The Future of Nuclear Energy

Engineerblogger
March 7, 2012

Aerial photograph of Vogtle nuclear power plant site, just outside Augusta, Georgia. The existing Vogtle 1 adn 2 operating units to the left and the Vogtle 3 and 4 construction site to the right. Courtesy: Southern Company 2011

Last March, the world watched closely as Japan struggled to contain a series of equipment failures, hydrogen explosions and releases of radioactive materials at the Fukushima Daiichi Nuclear Power Plant.

The historic tsunami following the 9.0-magnitude earthquake destroyed the reactors’ connection to the power grid, causing them to overheat. Hundreds of people were exposed to increased levels of radiation. Thousands more were evacuated. Although Japanese officials have since declared the plant stable, the cleanup will be expensive and is expected to take decades.

A year later, however, the United States is moving forward with nuclear power. For the first time since 1978, the National Regulatory Commission has approved two new plants. The $14 billion facilities will be built just outside Augusta and operated by Atlanta-based Southern Company. They’re scheduled to be up and running by 2016 and 2017 and should produce about 10 percent of Georgia’s power.

“It’s smart to continue generating nuclear power in the United States,” said Marilyn Brown, professor in Georgia Tech’s School of Public Policy. “It is a reliable, cost-competitive option that doesn’t contribute to air pollution or contribute to greenhouse gas emissions.” Brown helps shape the nation’s energy policies as a board member of the Tennessee Valley Authority (TVA) and chair of the company’s Nuclear Oversight Committee.

Brown said that nuclear power plants are expensive to build, compared to natural gas facilities.

“But they are clearly worth the investment,” she said. “A nuclear plant produces no carbon dioxide emissions and four times the power of a typical natural gas facility. Fourteen billion is a big number, but the plants should stay online for 50 to 70 years.”

Despite the benefits, critics will always point to the risk of a nuclear catastrophe. These are the nation’s first approved nuclear facilities since Pennsylvania’s Three Mile Island accident in 1979. Experts contend that modern plant designs are much safer than those built previously.

“The new plant designs are passively safe, so there are far fewer issues to worry about, like those that occurred with the older plants at Fukushima with the loss of off-site power,” said Glenn Sjoden, Georgia Tech professor of nuclear and radiological engineering. “With the new plants, you have a convection cooling loop that uses gravity and runs by itself for days in the event of lost power. There would be no active pumping required. . . . The more modern designs and precautions taken make nuclear the best option to satisfy our energy needs.”

Since last year’s incident, the Nuclear Regulatory Commission has been reviewing existing U.S. plants to ensure that they can withstand earthquakes, floods and other natural disasters and making retrofit upgrades when necessary, Sjoden said.

Critics point to nuclear waste as another challenge with nuclear power. Each of the nation’s 104 plants store the radioactive waste on-site in steel casks protected by concrete and other safety systems. These are safe too, Brown said, because of careful construction and maintenance.

Nuclear waste would be a nonissue if the U.S. reprocessed its spent fuel like other nations such as France, Sjoden said.

“Like most nations, they recycle their used fuel, since 95 percent of the fuel can be recycled back into the reactor and used again, making nuclear power the most ‘green’ energy source out there,” Sjoden said. “Burying the waste, as we do in the United States, is completely wasteful.”

The United States generates almost 20 percent of its energy from nuclear plants, the same amount as natural gas. Coal supplies 50 percent. The remainder is generated from hydropower and other natural sources.

“We must develop more renewables sources, such as wind, solar and biopower,” says Brown. “Industry leaders, business and the general public must also become more energy efficient. That is the key to our future.”

Source:  Georgia Institute of Technology

European project investment in nuclear waste recycling

Engineerblogger
Feb 16, 2012

Christian Ekberg Credit:Chalmers University of Technology

With a 9,4 million euro budget, a group of European researchers are collaborating to investigate nuclear fuel manufacturing and recycling for the fourth generation nuclear power systems. The aim is to produce safe fuel that can be 80 per cent recycled, compared to the current 1 per cent. Chalmers University of Technology is in charge of the initiative.

Fourth generation nuclear power systems can lead to a reduction of the amount of high-level, long-lived nuclear waste to a tenth of what it is today, while energy output can increase hundredfold. Many researchers believe the new technology will have a commercial breakthrough within 20 years. Germany is at present the only European country that has decided to phase out nuclear power.

"The technology needed for the fourth generation already exists," says Christian Ekberg, professor and nuclear chemistry research team leader at Chalmers. "What is needed now is for the different parts to be connected. One important aspect involves integrating nuclear waste recycling into the cycle so that nuclear power plants can be built with facilities to recycle waste and produce new nuclear fuel on site."
Christian Ekberg is also the inaugural holder of Stena Metall’s professorship in Industrial Materials Recycling, and is the coordinator of the new research project called Asgard, which has received 5,5 million euro in EU grants. Around 50 European researchers will take part in the project over four years.

"Traditionally, three different groups have worked separately on the fourth generation nuclear power systems: reactor physicists, fuel chemists and separation chemists. The groups will cooperate within the Asgard project to tie their previous findings together. We will also perform research on entirely new reactor fuels that are safer, use resources more effectively and that enable a more comprehensive approach to the waste issue."

Oxides currently dominate among the nuclear fuels that are produced from recycled nuclear waste. One example is MOX fuel. During the course of the Asgard project, researchers will examine other types of chemical compounds with uranium or plutonium. Examples include nitrides and carbides. These chemical compounds are safer to use in reactors, amongst other things because their high melting point and thermal conductivity offer a higher safety margin in terms of a nuclear meltdown.

Researchers will now investigate whether the new fuels' qualities are as positive in terms of recycling and production. At Chalmers – the European university best equipped to perform research on the entire nuclear fuel cycle – researchers will primarily concentrate on nitrides.

"If it is possible to recycle as much as we think, at least 80 per cent of nuclear waste will be possible to recycle," says Christian Ekberg. "This would also mean that eight times as much of the remaining waste could be included in the final repository, since heat generation is reduced. In addition, the amount of long-lived nuclides in residual waste is reduced, which results in a significantly shorter storage period. However, it is important to remember that the final repository is still an important part of the fuel cycle."


Information about the Asgard project
Asgard is a four-year EU project that is addressing new and innovative fuels for nuclear reactors. Of the budgeted 9,4 million euro, 5,5 million euro is being provided by EU grants. The project got started in January and comprises 16 organisations in 10 countries across Europe. In addition to Chalmers, other Swedish participants include the Royal Institute of Technology and Westinghouse.

From an overall financial perspective, the Asgard project is the biggest project ever at Chalmers' largest department, the Department of Chemical and Biological Engineering. Christian Ekberg (professor and Asgard coordinator), Gunnar Skarnemark (professor), Teodora Retegan (PhD) and Emma Aneheim and Marcus Hedberg (doctoral students) are the Chalmers researchers taking part in the project.

Information about the Genius project
The nuclear chemistry research team at Chalmers is also involved in the Swedish Genius cooperation project with the Royal Institute of Technology and Uppsala University. They are working on developing advanced nuclear fuel, performing research on materials for lead cooled reactors and performing safety analyses. The project aims to develop fourth generation nuclear power systems.
Read more about Genius

Source: Chalmers University of Technology

Small modular reactor design could be a 'SUPERSTAR'

Argonne National Laboratory
Feb 9, 2012

Credit: ANL

Though most of today's nuclear reactors are cooled by water, we've long known that there are alternatives; in fact, the world's first nuclear-powered electricity in 1951 came from a reactor cooled by sodium. Reactors cooled by liquid metals such as sodium or lead have a unique set of abilities that may again make them significant players in the nuclear industry.

At the U.S. Department of Energy's (DOE) Argonne National Laboratory, a team led by senior nuclear engineer James Sienicki has designed a new small reactor cooled by lead—the Sustainable Proliferation-resistance Enhanced Refined Secure Transportable Autonomous Reactor, or SUPERSTAR for short.

Small modular reactors, or SMRs, are small-scale nuclear plants that are designed to be factory-manufactured and shipped as modules to be assembled at a site. They can be designed to operate without refueling for 15 to 30 years. The concept offers promising answers to many questions about nuclear power—including proliferation, waste, safety and start-up costs.

SUPERSTAR is an example of a so-called "fast reactor," a type fundamentally different from the light-water reactors common today. Light-water reactors use water both as a coolant and as a moderator to slow down neutrons created in the fuel as it fissions. Instead, fast reactors use materials that don't slow down neutrons—often a liquid metal, such as sodium or lead.

Like all new generations of reactors, SUPERSTAR has "passive" safety systems—backup safety measures that kick in automatically, without human intervention, in case of accidents. For example, all reactors have control rods incorporating substances that absorb neutrons and stop nuclear chain reactions. SUPERSTAR's rods can be suspended above the reactor core held in place by electricity. If the plant loses power, the control rods will automatically drop into the core and stop the reaction.

In addition, SUPERSTAR's lead coolant is circulated around the core by a process called natural circulation. While existing plants use electrically-driven pumps to keep the water moving, SUPERSTAR exploits a law of physics to move the coolant.

"In any closed loop, with heat at the bottom and cooling on top, a flow will develop, with the heated stream rising to the top and cooled stream going down," explained Anton Moisseytsev, an Argonne nuclear engineer also working on the reactor design. "The SUPERSTAR design takes advantage of this feature—its lead coolant is circulated solely by natural circulation, with no pumps needed. And of course, having no pumps means no pump failures." This means that if the plant loses power, as happened at the Fukushima Daiichi plant in Japan, the reactor does not need electricity to cool the core after shutdown.
To read more click here...

One step closer to controlling nuclear fusion

Engineerblogger
Jan 16, 2012

Confined chamber for the plasma © EPFL

Using a heating system, physicists have succeeded for the first time in preventing the development of instabilities in an efficient alternative way relevant to a future nuclear fusion reactor. It’s an important step forward in the effort to build the future ITER reactor.

Scientists have achieved a milestone: they have managed to stop the growth of instabilities inside a nuclear fusion reactor. How? Here’s a look at this energy source, which despite being challenging to control, is nevertheless extremely promising.

Nuclear fusion is an attempt to reproduce the energy of the Sun in an Earth-based reactor system. When gas is heated to several million degrees, it becomes plasma. Sometimes in the plasma, an instability will appear and grow large enough to perturb the plasma, making it vibrate despite the presence of the magnetic field in which it is contained. If the plasma touches the walls of the reactor, it will cool rapidly and create large electromagnetic forces within the structure of the machine.

The challenge is to reduce the instabilities deep within in the interior of the plasma so that they don’t amplify, while at the same time allowing the reactor to continue to function normally. Thus it is necessary to work within the specific configuration of these fusion reactors, where the plasma is strongly confined by a magnetic field. By adjusting an antenna that emits electromagnetic radiation, Jonathan Graves and his colleagues from EPFL’s Center for Research in Plasma Physics were able to quench the instabilities when they appear, in the precise region where they are forming, and without perturbing the rest of the installation.

From theory to practice

The physicists first conducted simulations to verify the extent to which specific radiation frequencies and locations of application would suppress the growth of instabilities. Then they carried out tests to confirm their calculations. The beauty of their approach is that they were able to use antennas that are used as part of the system to heat the plasma, and that are already present in the Joint European Torus (JET), the largest reactor currently in use. Surprisingly, the simulations and the tests showed that heating and instability suppression can be combined, by aiming the radiation slightly off-center in the plasma.

The next step will be to add a detector system that will make it possible to neutralize instabilities in real time over longer time periods. These improvements can then be implemented in the ITER fusion reactor, currently in development in Southern France.

Source: École polytechnique fédérale de Lausanne (EPFL)

Additional Information:

• "Control of magnetohydrodynamic stability by phase space engineering of energetic ions in tokamak plasmas", J.P. Graves, I.T. Chapman, S. Coda, M. Lennholm, M. Albergante & M. Jucker, Nature Commun. *3*, 624 (2012). DOI: 10.1038/ncomms1622

New material for thermonuclear fusion reactors

Engineerblogger
Jan 10, 2011

Summary: Scientists at Universidad Carlos III de Madrid (UC3M), Oxford University (United Kingdom) and the University of Michigan (USA) have joined efforts to develop new materials for thermonuclear fusion reactors. Their research focuses on characterization of oxide dispersion-strengthened, reduced-activation steel for the reactor structure. (OIC/UC3M)

Thermonuclear fusion promises to be a possible solution to the current energy crisis. It is produced when two atomic nuclei of light elements combine to produce heavier elements, which give off a huge quantity of energy. So that this reaction can occur, it is necessary to supply an enormous amount of energy, so that temperatures of many millions of degrees can be reached, allowing the nuclei to come close enough to overcome their natural repulsion and become condensed in a plasma state. “This plasma, which reaches temperatures near that of the stars, around 100 million degrees, does not touch the walls of the reactors because they would melt,” explained one of the project researchers, Vanessa de Castro, from the UC3M Physics Department. In order to confine the plasma, it is confined within the reactor by the magnetic fields. “Even so the walls must resist some very high temperatures as well as the effects of the irradiation from the neutrons from the reaction, for which we have to produce new materials that can withstand these extreme conditions,” the Professor remarked.

The ITER project (under construction) and its successor, DEMO (scheduled for 2035) propose development of fusion reactors that are economically viable. This work depends on, among other things, the development of these new structural materials capable of withstanding damage by irradiation and elevated temperatures resulting from the fusion reaction. The scientific community has begun to develop new reduced - activation material for use in these reactors, but it is still not known if some of them will be viable under such hostile conditions. Along these lines, one of the most important candidates is oxide dispersion-strengthened, reduced-activation ferrite steel, called ODS steels.

The mechanic behavior of the ODS steels depends enormously on their microstructure, which until now has not been rigorously controlled. Until recently, studies on the microstructure of these steels have been on the micrometric scale. However, the nanometric scale is more relevant in understanding the phenomena that occur under irradiation. “We are now using our knowledge in nuclear structural materials and in advanced techniques of nanoanalysis to characterize diverse new generation ODS steels on the nanonmetric scale,” noted the researchers, who have added nanometric particles to these steels (between 1 and 50 nm), which help to improve the mechanical properties and increase their resistance. The results of the research have been recently published in a special number of the journal Materials Science and Technology dedicated to the atomic scale characterization of steels.

The characterization of these materials is carried out using nanometric scale techniques. For example, with a transmission electron microscope, particles can be seen which are added to the material, even the smallest one of a nanometer (one millionth of millimeter). Because of this the following can be studied: if the distribution of the particles is optimum, its chemical composition, or if by changing it, better material is obtained or if interaction of these particles with the defects produced in the material is improved. “From there we extract the information that allows us to explain why material behaves in one way or another, because the fact that it has bad mechanical properties could be related to the particles not being well-distributed”, ESTRUMAT’s Professor de Castro, pointed out. The objective of this Advanced Structural Materials consortium, composed of five research groups from four universities and a Madrid Region research institute, is to provide a framework of scientific-technological activity in the area of advanced materials structures for applications in engineering.

This research, funded by the Ministry of Science and Innovation, is focused on the study of oxide nanoparticles which are present in these steels, and the damage caused by radiation of these materials. The analyses carried out up to now show, for example, that the particles have a core-shell type structure consistent in an yttrium(Y) -rich nucleus surrounded by a chrome (Cr)-enriched area.

Source: Universidad Carlos III de Madrid (UC3M)

Related Information:

• Title: Analytical characterisation of oxide dispersion strengthened steels for fusion reactors Authors: de Castro, V. Lozano-Pérez, S. Marquis, E. A Auger, M. A. Leguey, T. Pareja, R. Source: Material Science and Technology. Volumen: 27 Número: 4 Páginas: 719-723 ISSN: 0267-0836

Small reactors could figure into U.S. energy future

Engineerblogger
Dec 14, 2011

Photo by Lloyd DeGrane

A newly released study from the Energy Policy Institute at the University of Chicago (EPIC) concludes that small modular reactors may hold the key to the future of U.S. nuclear power generation.

“Clearly, a robust commercial SMR industry is highly advantageous to many sectors in the United States,” concluded the study, led by Robert Rosner, institute director and the William Wrather Distinguished Service Professor in Astronomy & Astrophysics.

“It would be a huge stimulus for high-valued job growth, restore U.S. leadership in nuclear reactor technology and, most importantly, strengthen U.S. leadership in a post-Fukushima world, on matters of nuclear safety, nuclear security, nonproliferation, and nuclear waste management,” the report said.

The SMR report was one of two that Rosner rolled out Thursday, Dec. 1, at the Center for Strategic and International Studies in Washington, D.C. Through his work as former chief scientist and former director of Argonne National Laboratory, Rosner became involved in a variety of national policy issues, including nuclear and renewable energy technology development.

The reports assessed the economic feasibility of classical, gigawatt-scale reactors and the possible new generation of modular reactors. The latter would have a generating capacity of 600 megawatts or less, would be factory-built as modular components, and then shipped to their desired location for assembly.

The U.S. Department of Energy funded the reports through Argonne, which is operated by UChicago Argonne LLC. The principal authors of the report were Rosner and Stephen Goldberg, special assistant to Argonne’s director.

The reports followed up a 2004 UChicago study on the economic future of nuclear energy. The 2004 study concluded that the nuclear energy industry would need financial incentives from the federal government in order to build new plants that could compete with coal- and gas-fired plants.

The first report, “Analysis of GW-scale Overnight Costs,” updates the overnight cost estimates of the 2004 report. Overnight costs are the estimated costs if you were to build a new large reactor ‘overnight,’ that is, using current input prices and excluding the cost of financing.

It would now cost $4,210 per kilowatt to build a new gigawatt-scale reactor, according to the new report. This cost is approximately $2,210 per kilowatt higher than the 2004 estimate because of commodity price changes and other factors.

Struggling restart

At the Center for Strategic and International Studies event on Dec. 1, CSIS president and CEO John Hamre said that economic issues have hindered the construction of new large-scale reactors in the United States. The key challenge facing the industry is the seven-to-nine-year gap between making a commitment to build a nuclear plant and revenue generation.

Few companies can afford to wait that long to see a return on the $10 billion investment that a large-scale nuclear plant would require. “This is a real problem,” Hamre said, but the advent of the small modular reactor “offers the promise of factory construction efficiencies and a much shorter timeline.”

Natural gas would be the chief competitor of nuclear power generated by small modular reactors, but predicting the future of the energy market a decade from now is a risky proposition, Rosner said. “We’re talking about natural-gas prices not today but 10, 15 years from now when these kinds of reactors could actually hit the market.”

The economic viability of small modular reactors will depend partly on how quickly manufacturers can learn to build them efficiently. “The faster you learn, the better off you are in the long term because you get to the point where you actually start making money faster,” Rosner noted.

Small modular reactors could be especially appealing for markets that could not easily accommodate gigawatt-scale plants, such as those currently served by aging, 200- to 400-megawatt coal plants, which are likely to be phased out during the next decade, Rosner said. An unknown factor that will affect the future of these plants would be the terms of any new clean-air regulations that might be enacted in the next year.

An important safety aspect of small modular reactors is that they are designed to eliminate the need for human intervention during an emergency. In some of the designs, Rosner explained, “the entire heat load at full power can be carried passively by thermal convection. There’s no need for pumps.”

Getting the first modular reactors built will probably require the federal government to step in as the first customer. That is a policy issue, though, that awaits further consideration. “It’s a case that has to be argued out and thought carefully about,” Rosner said. “There’s a long distance between what we’re doing right now and actually implementing national policy.”

Source:  University of Chicago

Additional Information: 

• The full reports can be downloaded at the Energy Policy Institute website.

GE Hitachi Nuclear Energy Proposed to Turn World’s Biggest Civilian Plutonium Stockpile into Electricity

Engineerblogger
Dec 9, 2011

GE Hitachi Nuclear Energy has proposed to the U.K. government to build an advanced nuclear reactor that would consume the country’s stockpile of radioactive plutonium. The technology called PRISM, or Power Reactor Innovative Small Module, would use the plutonium to generate low-carbon electricity.

The U.K. has the world’s largest civilian stockpile of plutonium. The size of the stockpile is 87 tons and growing.

Nuclear reactors unlock energy by splitting atoms of the material stored in fuel rods. This process is called fission. For fission to be effective, neutrons – the nuclear particles that do the splitting and keep the reaction going – must maintain the right speed. Conventional reactors use water to cool and slow down neutrons, keeping fission effective. But water-cooled reactors leave some 95 percent of the fuel’s potential energy untapped.

PRISM is a so-called “fast reactor.” It uses liquid sodium, rather than water, to cool the reactor. The sodium allows the neutrons to maintain higher energies and to cause fission in elements such as plutonium more efficiently than water-cooled reactors.

PRISM incorporates “passive safety” features and can shut down automatically, in the unlikely event that it should be needed. PRISM does not need any automatic systems, valves or operators, to remove reactor heat after a shutdown with a complete loss electrical power.

Another benefit is PRISM’s relatively small size and simplified design. The reactor can be built in modules and transported to the power plant site, lowering the costs and adding another level of component control.

The plutonium is stockpiled in the coastal town of Sellafield in northern England. The Guardian newspaper reported that storing this plutonium costs the British government a significant amount of money per year to maintain. “Some in government want the plutonium to be classed as an asset, rather than a liability,” the newspaper wrote. GEH said that the PRISM reactor would use practically all the stored plutonium at Sellafield to create low-carbon electricity, turning it into an asset.

The PRISM reactor is very different from other proposals to process plutonium, including turning the spent fuel into mixed oxide (MOX). The PRISM reactor actually disposes of a great majority of the plutonium as opposed to simply reusing it over again without ever actually ridding the planet of the substance.

Source: GE Reports

Gates discussing new nuclear reactor with China

Engineerblogger
Dec 8, 2011

Microsoft Corp. co-founder Bill Gates speaks to the media after delivering a speech at the Ministry of Science and Technology in Beijing Wednesday, Dec. 7, 2011. Gates confirmed Wednesday he is in discussions with China to jointly develop a new kind of nuclear reactor. (AP Photo/Andy Wong)

Microsoft co-founder Bill Gates confirmed Wednesday he is in discussions with China to jointly develop a new and safer kind of nuclear reactor.

"The idea is to be very low cost, very safe and generate very little waste," said the billionaire during a talk at China's Ministry of Science and Technology.

Gates said he had largely funded a Washington state-based company, TerraPower, that is developing a Generation IV nuclear reactor that can run on depleted uranium. TerraPower says it has discussed its plans with India, Russia and other countries with nuclear energy programs.

The general manager of state-owned China National Nuclear Corporation, Sun Qin, was quoted in Chinese media last week saying Gates was working with it to research and develop a reactor.

"TerraPower is having very good discussions with CNNC and various people in the Chinese government," said Gates, cautioning the talks were at an early stage.

Gates says perhaps as much as a billion dollars will be put into research and development over the next five years.

TerraPower says its traveling wave reactor would run for decades on depleted uranium and produce significantly smaller amounts of nuclear waste than conventional reactors.

"All these new designs are going to be incredibly safe," Gates told the audience. "They require no human action to remain safe at all times."

He said they also benefit from an ability to simulate earthquake and tidal wave conditions. "It takes safety to a new level," he said.

Since leaving Microsoft Corp., Gates has concentrated on philanthropy and advocating on public health, education and clean energy issues. He is an investor and strategic adviser to TerraPower.

Gates was at the Ministry of Science and Technology to talk about a joint project between China and the Bill & Melinda Gates Foundation to support innovative research and development to help alleviate poverty.

Gates said the ministry will help identify entrepreneurs and companies to manufacture new products in global health and agriculture to "change the lives of poor people," including new vaccines and diagnostics and genetically modified seeds.

"China has a lot to contribute because it's solved many of the problems of poverty, not all of them but a lot of them, itself, and many Asian, south Asian and African countries are well behind, whether it's agriculture or health," said Gates.

No specific poverty alleviation projects were mentioned.

Source: The Associated Press

The Next Generation of Nuclear Reactors

Engineerblogger
Nov 29, 2011

The nuclear-power-generation future is quietly taking shape, at least virtually, through the labors of several hundred scientists and technicians working on the Next Generation Nuclear Plant (NGNP) at the Idaho National Laboratory (INL) in Idaho Falls, ID. Scattered through several research facilities and operating sites, these experts are wrestling with dozens of questions—from technology evaluations to site licensing to spent fuels—that accompany any extension of nuclear power.

High-temperature gas-cooled reactor.
Image courtesy of Idaho National Laboratory (INL).

NGNP is far more than an extension: it is a radical step forward for nuclear power. It will be the first truly new reactor design to go into commercial service in the U.S. in decades; it is to be up and running by September 2021. The way forward may not be smooth. Cost estimates range from $4 billion to nearly $7 billion and who pays for what remains unsettled. Nevertheless, barring a technical crunch, a licensing snag, or a financial meltdown, NGNP could become a cornerstone of an energy future with abundant electricity and drastically reduced carbon emissions.

The reactor initiative is for a high-temperature gas-cooled reactor or HTGC (sometimes abbreviated as HTGR), a graphite-moderated and helium-cooled design backed by considerable engineering development in Japan, China, Russia, South Africa, and, in the U.S. by General Atomics, Inc. The primary goal of the project is to commercialize HTGCs. Experts put the potential market at several hundred reactors if most coal-fired power plants are replaced.

Researcher at Idaho National Laboratory (INL).

Running NGNP is what the U.S. Department of Energy calls the NGNP Industry Alliance. Members include many of power-generation’s biggest names: General Atomics; Areva NP; Babcock & Wilcox; Westinghouse Electric Co.; SGL Group, a German producer of graphite and carbon products; and Entergy Nuclear. Entergy owns, operates, or manages 12 of the 104 power-gen reactors in the U.S. and is expected to handle licensing. These firms’ operations and expertise span the industry.

Further backing comes from the consortium that operates INL itself. Its members are Battelle Energy Alliance / Battelle Memorial Institute; Babcock & Wilcox; Washington Group International / URS Corp.; Massachusetts Institute of Technology; and the Electric Power Research Institute.

The high-temperature reference is to the reactor’s outlet temperature, about 1,000 °C, or very roughly three times higher than most of today’s reactors. That means HTGCs can be a source of low-carbon, high-temperature process heat for petroleum refining, biofuels production, the production of fertilizer and chemical feedstocks, and reprocessing coal into other fuels, among other uses. This is why the NGNP alliance includes Dow Chemical, Eastman Chemical, ConocoPhillips, Potash Corp., and the Petroleum Technology Alliance of Canada. All are potential customers for NGNP’s clean heat.

The NGNP Industry Alliance’s HTGC is an integral part of the Generation IV International Forum (GIF). Founded in 2000, GIF is a broadly based international effort to put nuclear power to widespread use for base-load electricity generation and low-cost heat for industrial processes. The other five Generation IV designs are molten-salt reactors, sodium-cooled fast, supercritical water-cooled, gas-cooled fast, and lead-cooled fast. (“Fast” refers to a portion of the neutron spectrum.)

Improvements to existing reactors of 2000 and later are classed as Generation III reactors. They have:

• standardized type designs to expedite licensing, reduce capital costs, and speed construction. Gen II’s were largely custom-built.

• simpler, more rugged designs for less complicated operation and lower vulnerability to operational problems.

• higher availability with fewer, shorter outages and operating lives stretching 60 years.

• better resistance to damage from possible core melts and aircraft impact.

• "grace periods" of 72 hours; a shutdown plant requires no active intervention for the first 72 hours in part because of passive or inherent safety features that rely on gravity, natural convection, or resistance to high temperatures.

• higher "burn up" to reduce fuel use and the amount of waste.

There is also a Gen III-plus group of about a dozen reactor designs in advanced planning stages. Today’s operating units, mostly built since 1970, are second generation. The first generation was 1950 - 1970 prototypes and demonstration units.

Despite optimistic long-term prospects for NGNP and Gen-IV, the nuclear industry’s critics raise two objections. First, safety risks may be greater initially with new reactor types as reactor operators will have had little experience with the new design. Second, fabrication, construction, and maintenance of new reactors can be expected to have a steep learning curve. Advanced technologies always carry a higher risk of accidents and mistakes than predecessors. Established technologies grow safer with accumulated experience and lessons-learned.

The NGNP program envisions dozens of these reactors by 2050. In contrast to today’s power-generation reactors and their enormous concrete-and-steel containment structures, these reactors may be nearly invisible. They will be underground in concrete silos 150 feet deep.

Meanwhile, ASME is playing a major role in NGNP research on metal alloys that can withstand the reactors’ extremely high outlet temperatures. The alloys under consideration are 800H (iron-nickel-chromium), Grade 91 steel (chromium–molybdenum) and Haynes International’s Hastelloy XR (nickel-chromium-iron-molybdenum). The work is being carried out by ASME Standards Technology LLC under an agreement with the U.S. Department of Energy.

Source: ASME

Reliable nuclear device to heat, power Mars Science Lab

Engineerblogger
Nov 24, 2011

NASA's Mars Science Laboratory mission, which is scheduled to launch this week, has the potential to be the most productive Mars surface mission in history. That's due in part to its nuclear heat and power source.

When the rover Curiosity heads to space as early as Saturday, it will carry the most advanced payload of scientific gear ever used on Mars' surface. Those instruments will get their lifeblood from a radioisotope power system assembled and tested at Idaho National Laboratory. The Multi-Mission Radioisotope Thermoelectric Generator is the latest "space battery" that can reliably power a deep space mission for many years.

The device provides a continuous source of heat and power for the rover's instruments. NASA has used nuclear generators to safely and reliably power 26 missions over the past 50 years. New generators like the one destined for Mars are painstakingly assembled and extensively tested at INL before heading to space.

"This power system will enable Curiosity to complete its ambitious expedition in Mars' extreme temperatures and seasons," said Stephen Johnson, director of INL's Space Nuclear Systems and Technology Division. "When the unit leaves here, we’ve verified every aspect of its performance and made sure it’s in good shape when it gets to Kennedy Space Center."

The power system provides about 110 watts of electricity and can run continuously for many years. The nuclear fuel is protected by multiple layers of safety features that have each undergone rigorous testing under varied accident scenarios.

The INL team began assembling the mission's power source in summer 2008. By December of that year, the power system was fully fueled, assembled and ready for testing. INL performs a series of tests to verify that such systems will perform as designed during their missions. These tests include:

• Vibrational testing to simulate rocket launch conditions.
• Magnetic testing to ensure the system's electrical field won't affect the rover's sensitive scientific equipment. 
• Mass properties tests to determine the center of gravity, which impacts thruster calculations for moving the rover.
• Thermal vacuum testing to verify operation on a planet’s surface or in the cold vacuum of space.

INL completed its tests in May 2009, but by then the planned September 2009 launch had been delayed until this month because of hurdles with other parts of the mission. So INL stored the power system until earlier this summer, when it was shipped to Kennedy Space Center and mated up with the rover to ensure everything fit and worked as designed.

The system will supply warmth and electricity to Curiosity and its scientific instruments using heat from nuclear decay. The generator is fueled with a ceramic form of plutonium dioxide encased in multiple layers of protective materials including iridium capsules and high-strength graphite blocks. As the plutonium naturally decays, it gives off heat, which is circulated through the rover by heat transfer fluid plumbed throughout the system. Electric voltage is produced by using thermocouples, which exploit the temperature difference between the heat source and the cold exterior. More details about the system are in a fact sheet here: http://www.inl.gov/marsrover/.

Curiosity is expected to land on Mars in August 2012 and carry out its mission over 23 months. It will investigate Mars' Gale Crater for clues about whether environmental conditions there have favored the development of microbial life, and to preserve any evidence it finds.

NASA chose to use a nuclear power source because solar power alternatives did not meet the full range of the mission's requirements. Only the radioisotope power system allows full-time communication with the rover during its atmospheric entry, descent and landing regardless of the landing site. And the nuclear powered rover can go farther, travel to more places, last longer, and power and heat a larger and more capable scientific payload compared to the solar power alternative NASA studied.

Source: Idaho National Laboratory (INL)

Related Article:

• NASA launching 'dream machine' to explore Mars

Thorium Energy: The Clean Energy Source We Need!

Engineerblogger
Nov 2011



With the global spotlight on green / renewable energy and on the safety of nuclear power following Japan's tsunami and the problems at the Fukushima Daiichi plant, Many countries are looking at spearheading efforts to make the industry safer.  For instance, the Chinese are investing millions in research into reactors powered by the element Thorium -- a metal, proponents say, as common as lead, and one which, despite some concerns, would lead to power plants with fewer safety issues as well as other benefits.  Thorium-based reactors certainly have advantages, the energy release from Thorium is greater than from Uranium, the by-products from using Thorium are less toxic than from Uranium, and it's much harder to make weapons from those by-products.

The development of workable and large-scale thorium reactors has for decades been a dream for nuclear engineers, while for environmentalists it has become a major hope as an alternative to fossil fuels. Proponents say the fuel has considerable advantages over uranium. Thorium is more abundant and exploiting it does not involve release of large quantities of carbon dioxide, making it less dangerous for the climate than fossil fuels like coal and oil.

Producing a workable thorium reactor would be a massive breakthrough in energy generation. Using thorium – a naturally occurring moderately radioactive element named after the Norse god of thunder – as a source of atomic power is not new technology. Promising early research was carried out in the US in the 1950s and 60s and then abandoned in favour of using uranium.

The pro-thorium lobby maintains this was at least partly because national nuclear power programs in the US and elsewhere were developed with a military purpose in mind: namely access to a source of plutonium for nuclear weapons. Unlike uranium, thorium-fuelled reactors do not result in a proliferation of weapons-grade plutonium. Also, under certain circumstances, the waste from thorium reactors is less dangerous and remains radioactive for hundreds rather than thousands of years.

Thorium as a nuclear fuel
Thorium (Th-232) is not itself fissile and so is not directly usable in a thermal neutron reactor – in this regard it is very similar to uranium-238. However, it is ‘fertile’ and upon absorbing a neutron will transmute to uranium-233 (U-233) , which is an excellent fissile fuel material. Thorium fuel concepts therefore require that Th-232 is first irradiated in a reactor to provide the necessary neutron dosing. The U-233 that is produced can either be chemically separated from the parent thorium fuel and recycled into new fuel, or the U-233 may be usable ‘in-situ’ in the same fuel form."

Thorium fuels therefore need a fissile material as a ‘driver’ so that a chain reaction (and thus supply of surplus neutrons) can be maintained. The only fissile driver options are U-233, U-235 or Pu-239.

It is possible – but quite difficult – to design thorium fuels that produce more U-233 in thermal reactors than the fissile material they consume (this is referred to as having a fissile conversion ratio of more than 1.0 and is also called breeding). Thermal breeding with thorium is only really possible using U-233 as the fissile driver, and to achieve this the neutron economy in the reactor has to be very good (ie, low neutron loss through escape or parasitic absorption). The possibility to breed fissile material in slow neutron systems is a unique feature for thorium-based fuels and is not possible with uranium fuels.

Another distinct option for using thorium is as a ‘fertile matrix’ for fuels containing plutonium (and even other transuranic elements like americium). No new plutonium is produced from the thorium component, unlike for uranium fuels, and so the level of net consumption of this metal is rather high. In fresh thorium fuel, all of the fissions (thus power and neutrons) derive from the driver component. As the fuel operates the U-233 content gradually increases and it contributes more and more to the power output of the fuel. The ultimate energy output from U-233 (and hence indirectly thorium) depends on numerous fuel design parameters, including: fuel burn-up attained, fuel arrangement, neutron energy spectrum and neutron flux (affecting the intermediate product protactinium-233, which is a neutron absorber).
  
Thorium R&D history
The use of thorium-based fuel cycles has been studied for about 40 years, but on a much smaller scale than uranium or uranium/plutonium cycles. Basic research and development has been conducted in Germany, India, Japan, Russia, the UK and the USA. Test reactor irradiation of thorium fuel to high burn-ups has also been conducted and several test reactors have either been partially or completely loaded with thorium-based fuel.

Noteworthy experiments involving thorium fuel include the following, the first three being high-temperature gas-cooled reactors:

• Between 1967 and 1988, the AVR (Atom Versuchs Reaktor, Nuclear Test Reactor) experimental pebble bed reactor at Jülich, Germany, operated for over 750 weeks at 15 MWe, about 95% of the time with thorium-based fuel. The fuel used consisted of about 100,000 billiard ball-sized fuel elements. Overall a total of 1360 kg of thorium was used, mixed with high-enriched uranium (HEU). Burn-ups of 150,000 MWd/t were achieved.

• Thorium fuel elements with a 10:1 Th/U (HEU) ratio were irradiated in the 20 MWth Dragon reactor at Winfrith, UK, for 741 full power days. Dragon was run as an OECD/Euratom cooperation project, involving Austria, Denmark, Sweden, Norway and Switzerland in addition to the UK, from 1964 to 1973. The Th/U fuel was used to 'breed and feed', so that the U-233 formed replaced the U-235 at about the same rate, and fuel could be left in the reactor for about six years.

• General Atomics' Peach Bottom high-temperature, graphite-moderated, helium-cooled reactor in the USA operated between 1967 and 1974 at 110 MWth, using high-enriched uranium with thorium.

• In Canada, AECL has more than 50 years experience with thorium-based fuels, including burn-up to 47 GWd/t. Some 25 tests were performed to 1987 in three research reactors and one pre-commercial reactor (NPD), with fuels ranging from ThO2 to that with 30% UO2, though most were with 1-3% UO2, the U being high-enriched.

• In India, the Kamini 30 kWth experimental neutron-source research reactor using U-233, recovered from ThO2 fuel irradiated in another reactor, started up in 1996 near Kalpakkam. The reactor was built adjacent to the 40 MWt Fast Breeder Test Reactor, in which the ThO2 is irradiated.

• In the Netherlands, an aqueous homogenous suspension reactor operated at 1MWth for three years in the mid-1970s. The HEU/Th fuel was circulated in solution and reprocessing occurred continuously to remove fission products, resulting in a high conversion rate to U-233.

There have also been several experiments with fast neutron reactors.

Current thorium fuel cycle research
Several advanced reactors concepts are currently being developed, including:

• High-temperature gas-cooled reactors (HTGRs) of two kinds: pebble bed and with prismatic fuel elements. The Gas Turbine-Modular Helium Reactor (GT-MHR) being developed by General Atomics uses a prismatic fuel and builds on US experience, particularly from the Fort St Vrain reactor. The GT-MHR core can accommodate a wide range of fuel options, including HEU/Th, U-233/Th and Pu/Th. Pebble bed reactor development builds on German work with the AVR and THTR and is under development in China and South Africa c . A pebble bed reactor can potentially use thorium in its fuel pebbles.

• The Radkowsky Thorium Reactor builds on the seed-blanket arrangement of the LWBR concept. (see subsection below)

• The molten salt reactor (MSR) is an advanced breeder concept, in which the coolant is a molten salt, usually a fluoride salt mixture. This is hot, but not under pressure, and does not boil below about 1400°C. Much research has focused on lithium and beryllium additions to the salt mixture. The fuel can be dissolved enriched uranium, thorium or U-233 fluorides, and recent discussion has been on the Liquid Fluoride Thorium Reactor, utilizing U-233 which has been bred in a liquid thorium salt blanket and continuously removed to be added to the core. The MSR was studied in depth in the 1960s, but is now being revived because of the availability of advanced technology for the materials and components. There is now renewed interest in the MSR concept in China, Japan, Russia, France and the USA, and one of the six Generation IV designs selected for further development is the MSR (see also subsection below and information page on Generation IV Nuclear Reactors).

• CANDU-type reactors – AECL is researching the thorium fuel cycle application to Enhanced Candu 6 and ACR-1000 reactors with 5% plutonium (reactor grade) plus thorium. In the closed fuel cycle, the driver fuel required for starting off is progressively replaced with recycled U-233, so that on reaching equilibrium 80% of the energy comes from thorium. Fissile drive fuel could be LEU, plutonium, or recycled uranium from LWR. AECL envisages fleets of CANDU reactors with near-self-sufficient equilibrium thorium (SSET) fuel cycles and a few fast breeder reactors to provide plutonium. AECL is also working closely with Third Qinshan Nuclear Power Company (TQNPC), China North Nuclear Fuel Corporation and Nuclear Power Institute of China (NPIC) at Chengdu to develop and demonstrate the use of thorium fuel and to study the commercial and technical feasibility of its full-scale use in Candu units such as at Qinshan. (see also Th in PHWR subsection of R&D section in China Fuel Cycle paper)

• Advanced heavy water reactor (AHWR) – India is working on this and, like the Canadian ACR design, the 300 MWe AHWR design is light water cooled. The main part of the core is subcritical with Th/U-233 oxide and Th/Pu-239 oxide, mixed so that the system is self-sustaining in U-233. The initial core will be entirely Th-Pu-239 oxide fuel assemblies, but as U-233 is available, 30 of the fuel pins in each assembly will be Th-U-233 oxide, arranged in concentric rings. It is designed for 100-year plant life and is expected to utilise 65% of the energy of the fuel. About 75% of the power will come from the thorium.

• Fast breeder reactor (FBRs), along with the AHWRs, play an essential role in India's three-stage nuclear power program (see section on India's plans for thorium cycle below). A 500 MWe prototype FBR under construction in Kalpakkam is designed to breed U-233 from thorium.

Liquid Fluoride Thorium Reactor
A quite different concept is the Liquid Fluoride Thorium Reactor (LFTR), utilizing U-233 which has been bred in a liquid thorium salt blanket(shown in video above).

The core consists of fissile U-233 tetrafluoride in molten fluoride salts of lithium and beryllium at some 700°C and at low pressure within a graphite structure that serves as a moderator and neutron reflector. Fission products dissolve in the salt and are removed progressively – xenon bubbles out, others are captured chemically. Actinides are less-readily formed than in fuel with atomic mass >235, and those that do form stay in the fuel until they are transmuted and eventually fissioned.

The blanket contains a mixture of thorium tetrafluoride in a fluoride salt containing lithium and beryllium, made molten by the heat of the core. Newly-formed U-233 forms soluble uranium tetrafluoride (UF4), which is converted to gaseous uranium hexafluoride (UF6) by bubbling fluorine gas through the blanket solution (which does not chemically affect the less-reactive thorium tetrafluoride). Uranium hexafluoride comes out of solution, is captured, then is reduced back to soluble UF4 by hydrogen gas in a reduction column, and finally is directed to the core to serve as fissile fuel.

The LFTR is not a fast reactor, but with some moderation by the graphite is epithermal (intermediate neutron speed). Safety is achieved with a freeze plug which if power is cut allows the fuel to drain into subcritical geometry in a catch basin. There is also a negative temperature coefficient of reactivity due to expansion of the fuel. The China Academy of Sciences in January 2011 launched an R&D program on LFTR, known there as the thorium-breeding molten-salt reactor (Th-MSR or TMSR), and claimed to have the world's largest national effort on it, hoping to obtain full intellectual property rights on the technology.

Much development work is still required before the thorium fuel cycle can be commercialised, its potential for breeding fuel without the need for fast neutron reactors, holds considerable potential in the long-term. It is a significant factor in the long-term sustainability of nuclear energy.

Source: World Nuclear Association




Related Articles:

• Don't believe the spin on thorium being a greener nuclear option
• Safe nuclear does exist, and China is leading the way with thorium 
• Thorium nuclear power 
• India plans 'safer' nuclear plant powered by thorium 

Thorium Energy: The clean energy source we need!

Engineerblogger
Nov 2011



With the global spotlight on green / renewable energy and on the safety of nuclear power following Japan's tsunami and the problems at the Fukushima Daiichi plant, many countries are looking at spearheading efforts to make the industry and the environment safer.  For instance, the Chinese are investing millions in research into reactors powered by the element Thorium -- a metal, proponents say, as common as lead, and one which, despite some concerns, would lead to power plants with fewer safety issues as well as other benefits.  Thorium-based reactors certainly have advantages, the energy release from Thorium is greater than from Uranium, the by-products from using Thorium are less toxic than from Uranium, and it's much harder to make weapons from those by-products.

Thorium as a nuclear fuel

Thorium (Th-232) is not itself fissile and so is not directly usable in a thermal neutron reactor – in this regard it is very similar to uranium-238. However, it is ‘fertile’ and upon absorbing a neutron will transmute to uranium-233 (U-233) , which is an excellent fissile fuel material. Thorium fuel concepts therefore require that Th-232 is first irradiated in a reactor to provide the necessary neutron dosing. The U-233 that is produced can either be chemically separated from the parent thorium fuel and recycled into new fuel, or the U-233 may be usable ‘in-situ’ in the same fuel form."

Thorium fuels therefore need a fissile material as a ‘driver’ so that a chain reaction (and thus supply of surplus neutrons) can be maintained. The only fissile driver options are U-233, U-235 or Pu-239.

It is possible – but quite difficult – to design thorium fuels that produce more U-233 in thermal reactors than the fissile material they consume (this is referred to as having a fissile conversion ratio of more than 1.0 and is also called breeding). Thermal breeding with thorium is only really possible using U-233 as the fissile driver, and to achieve this the neutron economy in the reactor has to be very good (ie, low neutron loss through escape or parasitic absorption). The possibility to breed fissile material in slow neutron systems is a unique feature for thorium-based fuels and is not possible with uranium fuels.

Another distinct option for using thorium is as a ‘fertile matrix’ for fuels containing plutonium (and even other transuranic elements like americium). No new plutonium is produced from the thorium component, unlike for uranium fuels, and so the level of net consumption of this metal is rather high. In fresh thorium fuel, all of the fissions (thus power and neutrons) derive from the driver component. As the fuel operates the U-233 content gradually increases and it contributes more and more to the power output of the fuel. The ultimate energy output from U-233 (and hence indirectly thorium) depends on numerous fuel design parameters, including: fuel burn-up attained, fuel arrangement, neutron energy spectrum and neutron flux (affecting the intermediate product protactinium-233, which is a neutron absorber).
  
Thorium R&D history
The use of thorium-based fuel cycles has been studied for about 40 years, but on a much smaller scale than uranium or uranium/plutonium cycles. Basic research and development has been conducted in Germany, India, Japan, Russia, the UK and the USA. Test reactor irradiation of thorium fuel to high burn-ups has also been conducted and several test reactors have either been partially or completely loaded with thorium-based fuel.

Noteworthy experiments involving thorium fuel include the following, the first three being high-temperature gas-cooled reactors:

• Between 1967 and 1988, the AVR (Atom Versuchs Reaktor, Nuclear Test Reactor) experimental pebble bed reactor at Jülich, Germany, operated for over 750 weeks at 15 MWe, about 95% of the time with thorium-based fuel. The fuel used consisted of about 100,000 billiard ball-sized fuel elements. Overall a total of 1360 kg of thorium was used, mixed with high-enriched uranium (HEU). Burn-ups of 150,000 MWd/t were achieved.

• Thorium fuel elements with a 10:1 Th/U (HEU) ratio were irradiated in the 20 MWth Dragon reactor at Winfrith, UK, for 741 full power days. Dragon was run as an OECD/Euratom cooperation project, involving Austria, Denmark, Sweden, Norway and Switzerland in addition to the UK, from 1964 to 1973. The Th/U fuel was used to 'breed and feed', so that the U-233 formed replaced the U-235 at about the same rate, and fuel could be left in the reactor for about six years.

• General Atomics' Peach Bottom high-temperature, graphite-moderated, helium-cooled reactor in the USA operated between 1967 and 1974 at 110 MWth, using high-enriched uranium with thorium.

• In Canada, AECL has more than 50 years experience with thorium-based fuels, including burn-up to 47 GWd/t. Some 25 tests were performed to 1987 in three research reactors and one pre-commercial reactor (NPD), with fuels ranging from ThO2 to that with 30% UO2, though most were with 1-3% UO2, the U being high-enriched.

• In India, the Kamini 30 kWth experimental neutron-source research reactor using U-233, recovered from ThO2 fuel irradiated in another reactor, started up in 1996 near Kalpakkam. The reactor was built adjacent to the 40 MWt Fast Breeder Test Reactor, in which the ThO2 is irradiated.

• In the Netherlands, an aqueous homogenous suspension reactor operated at 1MWth for three years in the mid-1970s. The HEU/Th fuel was circulated in solution and reprocessing occurred continuously to remove fission products, resulting in a high conversion rate to U-233.

There have also been several experiments with fast neutron reactors.

Current thorium fuel cycle research

Several advanced reactors concepts are currently being developed, including:

• High-temperature gas-cooled reactors (HTGRs) of two kinds: pebble bed and with prismatic fuel elements. The Gas Turbine-Modular Helium Reactor (GT-MHR) being developed by General Atomics uses a prismatic fuel and builds on US experience, particularly from the Fort St Vrain reactor. The GT-MHR core can accommodate a wide range of fuel options, including HEU/Th, U-233/Th and Pu/Th. Pebble bed reactor development builds on German work with the AVR and THTR and is under development in China and South Africa c . A pebble bed reactor can potentially use thorium in its fuel pebbles.

• The Radkowsky Thorium Reactor builds on the seed-blanket arrangement of the LWBR concept. (see subsection below)

• The molten salt reactor (MSR) is an advanced breeder concept, in which the coolant is a molten salt, usually a fluoride salt mixture. This is hot, but not under pressure, and does not boil below about 1400°C. Much research has focused on lithium and beryllium additions to the salt mixture. The fuel can be dissolved enriched uranium, thorium or U-233 fluorides, and recent discussion has been on the Liquid Fluoride Thorium Reactor, utilizing U-233 which has been bred in a liquid thorium salt blanket and continuously removed to be added to the core. The MSR was studied in depth in the 1960s, but is now being revived because of the availability of advanced technology for the materials and components. There is now renewed interest in the MSR concept in China, Japan, Russia, France and the USA, and one of the six Generation IV designs selected for further development is the MSR (see also subsection below and information page on Generation IV Nuclear Reactors).

• CANDU-type reactors – AECL is researching the thorium fuel cycle application to Enhanced Candu 6 and ACR-1000 reactors with 5% plutonium (reactor grade) plus thorium. In the closed fuel cycle, the driver fuel required for starting off is progressively replaced with recycled U-233, so that on reaching equilibrium 80% of the energy comes from thorium. Fissile drive fuel could be LEU, plutonium, or recycled uranium from LWR. AECL envisages fleets of CANDU reactors with near-self-sufficient equilibrium thorium (SSET) fuel cycles and a few fast breeder reactors to provide plutonium. AECL is also working closely with Third Qinshan Nuclear Power Company (TQNPC), China North Nuclear Fuel Corporation and Nuclear Power Institute of China (NPIC) at Chengdu to develop and demonstrate the use of thorium fuel and to study the commercial and technical feasibility of its full-scale use in Candu units such as at Qinshan. (see also Th in PHWR subsection of R&D section in China Fuel Cycle paper)

• Advanced heavy water reactor (AHWR) – India is working on this and, like the Canadian ACR design, the 300 MWe AHWR design is light water cooled. The main part of the core is subcritical with Th/U-233 oxide and Th/Pu-239 oxide, mixed so that the system is self-sustaining in U-233. The initial core will be entirely Th-Pu-239 oxide fuel assemblies, but as U-233 is available, 30 of the fuel pins in each assembly will be Th-U-233 oxide, arranged in concentric rings. It is designed for 100-year plant life and is expected to utilise 65% of the energy of the fuel. About 75% of the power will come from the thorium.

• Fast breeder reactor (FBRs), along with the AHWRs, play an essential role in India's three-stage nuclear power program (see section on India's plans for thorium cycle below). A 500 MWe prototype FBR under construction in Kalpakkam is designed to breed U-233 from thorium.

Liquid Fluoride Thorium Reactor

A quite different concept is the Liquid Fluoride Thorium Reactor (LFTR), utilizing U-233 which has been bred in a liquid thorium salt blanket.

The core consists of fissile U-233 tetrafluoride in molten fluoride salts of lithium and beryllium at some 700°C and at low pressure within a graphite structure that serves as a moderator and neutron reflector. Fission products dissolve in the salt and are removed progressively – xenon bubbles out, others are captured chemically. Actinides are less-readily formed than in fuel with atomic mass >235, and those that do form stay in the fuel until they are transmuted and eventually fissioned.

The blanket contains a mixture of thorium tetrafluoride in a fluoride salt containing lithium and beryllium, made molten by the heat of the core. Newly-formed U-233 forms soluble uranium tetrafluoride (UF4), which is converted to gaseous uranium hexafluoride (UF6) by bubbling fluorine gas through the blanket solution (which does not chemically affect the less-reactive thorium tetrafluoride). Uranium hexafluoride comes out of solution, is captured, then is reduced back to soluble UF4 by hydrogen gas in a reduction column, and finally is directed to the core to serve as fissile fuel.

The LFTR is not a fast reactor, but with some moderation by the graphite is epithermal (intermediate neutron speed). Safety is achieved with a freeze plug which if power is cut allows the fuel to drain into subcritical geometry in a catch basin. There is also a negative temperature coefficient of reactivity due to expansion of the fuel. The China Academy of Sciences in January 2011 launched an R&D program on LFTR, known there as the thorium-breeding molten-salt reactor (Th-MSR or TMSR), and claimed to have the world's largest national effort on it, hoping to obtain full intellectual property rights on the technology.

Much development work is still required before the thorium fuel cycle can be commercialised, its potential for breeding fuel without the need for fast neutron reactors, holds considerable potential in the long-term. It is a significant factor in the long-term sustainability of nuclear energy.

Source: World Nuclear Association





Related Articles:

• Don't believe the spin on thorium being a greener nuclear option
• Safe nuclear does exist, and China is leading the way with thorium 
• Is thorium the answer to our energy crisis?  
• Is Thorium the Biggest Energy Breakthrough Since Fire? Possibly. 

Miniaturizing nuclear recycling experiments : New device could help design new fuel reprocessing methods

Engineerblogger
Oct 21, 2011

Argonne scientists Artem Guelis (right) and Kevin Nichols test their miniaturized apparatus for nuclear recycling research

Designing better ways to recycle spent nuclear fuel could make nuclear energy a safer solution to the global energy problem, but there are a lot of gaps in our chemical knowledge—and it's difficult to get those answers when the experiments involve radioactive material.

Scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory have one answer: Shrink the whole experiment down—to microliters.

When it comes out of a reactor, nuclear spent fuel contains a whole glut of different radioactive isotopes, all mixed together.

For years, scientists have looked for ways to separate out reusable fuel from the truly toxic stuff.

The nations that recycle spent nuclear fuel today use processes based on PUREX, a technique whose underpinnings date back to the 1940s. Ideally, new processes would make fuel recycling cheaper, safer and less complex.

But one big challenge to creating models that accurately represent fuel reprocessing lies in determining the rates of reaction in the procedure—essentially, how quickly different elements move between phases.

Recycling nuclear fuel is fundamentally a sorting exercise: chemists want to sift out the useful uranium from the bulk of other byproducts and highly radioactive ones. The fuel is dissolved in acid and different metals can be separated out using solvent extraction—a bit like oil collecting on the surface of a bottle of salad dressing. The rates at which the metals separate is determined by kinetics, and knowing the rates helps scientists design new and better techniques.

"From the chemistry standpoint, if we want to be able to design new and improved nuclear recycling schemes, you have to be able to understand the mechanism," said Argonne chemical engineer Kevin Nichols, who helped lead the research. "You have to be able to develop chemical insight, which comes from knowing the kinetics."

Previous experiments that looked into the kinetics of these particular classes of reactions used large volumes of material, which slows the process and leads to less accurate results. But Nichols and chemist Artem Gelis have built a solution: an apparatus that miniaturizes the process.

"If we cut the size down, we can do the same experiment much more quickly, generate less waste and get more precise measurements," Gelis explained.

The apparatus uses mere drops of radioactive material, rather than liters. This allows hundreds or even thousands of trials to be performed with just a few microliters of sample.

The new process grew out of a combination of solvent extraction research being done at Argonne and work being done by University of Chicago professor Rustem Ismagilov, whose laboratory created a miniaturized apparatus for protein crystallization. The process generated thousands of aqueous droplets containing proteins separated by an oil layer, which—as it happens—is similar to the process for nuclear recycling. Though it had not been tried before, the researchers decided to modify the technique for nuclear fuel treatment kinetics.

Next, the team is planning to adapt the technique for other applications, such as processes that produce radioactive isotopes for medical use or even rare earth metal processing.

Rare earth metals are used in many energy technologies, such as solar panels and compact fluorescent lightbulbs, but today are primarily mined in China. The U.S. has rare earth metal deposits, but the popularity of renewable energy has triggered new interest in making U.S. rare earth metal mining more economical.

The paper, "Toward Mechanistic Understanding of Nuclear Reprocessing Chemistries by Quantifying Lanthanide Solvent Extraction Kinetics via Microfluidics with Constant Interfacial Area and Rapid Mixing", was published in the Journal of the American Chemical Society and is available online.

Source: Argonne National Laboratory

Nuclear energy phase-out is possible

ETH Zurich
Sept 2, 2011

Restructuring the energy system without nuclear power by 2050 is in principle technologically possible and economically manageable. However, it will demand a concerted effort by the whole of society. This is the conclusion reached by ETH Zurich researchers in a study they presented at the Energy Talks 2011.

Over the past few months, a group of researchers at the Energy Science Center (ESC) of ETH Zurich have carried out an intensive examination of whether the available options will enable Switzerland to scope out a medium-term energy future without nuclear power, as decided by the Swiss Federal Council in May. Their answer was «yes».

However, a step-by step restructuring of Switzerland’s energy systems during the coming years and decades will require great efforts by all areas of society. Nevertheless, a phase-out is not only technologically possible but would also enable positive long-term growth in all sectors of the economy. The study examined the period up to 2050. The researchers presented the most important results of the study (see box) at the Energy Talks at ETH Zurich on 2 September 2011.

No relaxations in climate targets
The unalterable boundary conditions applying to the ETH Zurich researchers’ modelling calculations are that the global climate targets – a maximum warming of two degrees centigrade – must be complied with. For Switzerland this means reducing annual per capita CO2 emissions from the present 5.2 to less than 2 tons by 2050 and to 1 ton towards the end of the century.

These targets require that, by 2050, this country must achieve, among other things, CO2-free building heating systems, efficient, partly electrified mobility, and minimal CO2 emission in electricity generation, all developments that are expected to be necessary and possible.

Hydroelectric power and new renewable energy sources

One of the biggest challenges facing the studies was to make plausible forecasts of the future electricity supply, which turn out differently depending on economic growth, population development and efficiency increases. For this purpose, the researchers calculated three demand scenarios and predict that, in 2050, Switzerland will have a gross electricity production of between 67 and 92 terawatt-hours (TWh). The most likely «medium» scenario assumes an annual electricity demand of around 80 TWh.

According to Konstantinos Boulouchos, coordinating author of the ETH Zurich study and Professor of Aerothermochemistry and Combustion Systems, it is clear that hydroelectric power, which amounts to just under 50 percent of total electricity generation and has limited potential for expansion, will continue to make an important base-load contribution. If the remaining 40 TWh is to be provided without nuclear energy, this will need a major expansion in new renewable energy sources, mainly photovoltaic, followed by the localised utilisation of biomass and finally geothermal energy. According to the ETH Zurich researchers, flexible gas-fired power stations or electricity imports will be indispensable to cover demand peaks, at least in the short term. However, foreseeable technological development should enable, from 2020 to 2025 onwards, the construction of combined gas-fired power stations in which the CO2 produced can be captured and stored.
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Advanced Reactor Gets Closer to Reality

Technology Review
July 29, 2011

 Terrapower, a startup funded in part by Nathan Myhrvold and Bill Gates, is moving closer to building a new type of nuclear reactor called a traveling wave reactor that runs on an abundant form of uranium. The company sees it as a possible alternative to fusion reactors, which are also valued for their potential to produce power from a nearly inexhaustible source of fuel.

Work on Terrapower's reactor design began in 2006. Since then, the company has changed its original design to make the reactor look more like a conventional one. The changes would make the reactor easier to engineer and build. The company has also calculated precise dimensions and performance parameters for the reactor. Terrapower expects to begin construction of a 500-megawatt demonstration plant in 2016 and start it up in 2020. It's working with a consortium of national labs, universities, and corporations to overcome the primary technical challenge of the new reactor: developing new materials that can withstand use in the reactor core for decades at a time. It has yet to secure a site for an experimental plant—or the funding to build it.

The reactor is designed to be safer than conventional nuclear reactors because it doesn't require electricity to run cooling systems to prevent a meltdown. But the new reactor doesn't solve what is probably the biggest problem facing nuclear power today: the high cost of building them. John Gilleland, Terrapower's CEO, says the company expects the reactors to cost about as much to build as conventional ones, "but the jury is still not in on that."

Conventional reactors generate heat and electricity as a result of the fission of a rare form of uranium—uranium 235. In a traveling wave reactor, a small amount of uranium 235 is used to start up the reactor. The neutrons the reactor produces then convert the far more abundant uranium 238 into plutonium 239, a fissile material that can generate the heat needed for nuclear power. Uranium 238 is readily available in part because it's a waste product of the enrichment processes used to make conventional nuclear fuel. It may also be affordable in the future to extract uranium 238 from seawater if demand for nuclear fuel is high. Terrapower says there's enough of this fuel to supply the world with power for a million years, even if everyone were to use as much power as people in the United States do.
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Additional Information:

• Depleted Uranium as Fuel Cuts Path to Less Waste
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China makes nuclear power breakthrough

AFP
July 22, 2011

China said Friday it had hooked its first so-called "fourth generation" nuclear reactor to the grid, a breakthrough that could eventually reduce its reliance on uranium imports

The experimental fast-neutron reactor is the result of more than 20 years of research and could also help minimise radioactive waste from nuclear energy, the state-run China Institute of Atomic Energy (CIAE) said.

China is the ninth country to develop a fast-neutron reactor, which uses uranium 60 times more efficiently than a normal reactor, helping the country to reduce its reliance on imports of the mineral.

Beijing has stepped up investment in nuclear power in an effort to slash its world-leading carbon emissions and scale down the country's heavy reliance on coal, which accounts for 70 percent of its energy needs.

But China's uranium reserves are limited, and it will have to import increasingly large amounts as its civilian nuclear programme gathers speed.

China -- the world's second largest economy -- currently has 14 nuclear reactors and is building more than two dozen others. It aims to get 15 percent of its power from renewable sources by 2020.

According to the World Nuclear Association, it aims to increase nuclear power capacity to 80 gigawatts by 2020 from 10.8 gigawatts in 2010.

The fourth-generation reactor, located just outside Beijing, has a capacity of just 20 megawatts. Other recently launched nuclear reactors in China had a capacity of more than one gigawatt, or 1,000 megawatts.

The latest technological step comes after China succeeded in reprocessing spent nuclear fuel in an experimental reactor in the northwestern province of Gansu in January.

Authorities said this would help extend the lifespan of proven uranium deposits to 3,000 years from the current forecast of 50-70 years.

Beijing has also pledged to improve emergency procedures and construction standards at its nuclear power plants, after Japan's devastating earthquake and ensuing tsunami triggered an atomic crisis.

Copyright © 2011 AFP

University of Manchester examines safety of the next generation of nuclear reactors

University of Manchester
July 20, 2011

As part of a consortium of EU research institutes and universities, academics from the University’s Dalton Nuclear Institute will carry out research on evolutionary designs of nuclear reactors called Generation IV.

The 1mEuro project is called SARGEN IV, which stands for 'Safety Assessment of Reactors of Generation IV'. The money has been provided from the EC Euratom Framework Programme.

The outcome of the University of Manchester research will be key in defining the future EU research agenda for the successful implementation of this advanced technology.

Generation IV reactors are evolutionary in design and so will be able to ‘burn’ plutonium created from the spent fuel from pressurised water reactors (PWR).

This will allow them to improve the efficiency of the fuel cycle and form an option for the UK when its expected new fleet of PWRs has been built and is operational – forecast to be in about 2040.

Being evolutionary, they will be the state-of-the-art in design and types of materials used and will have a high level of nuclear safety.

The safety claims will need assessing before their deployment and the objective of this project is to identify what the critical issues might be, to develop a roadmap for necessary research to address them and assist with the development of a safety assessment approach for the licensing of these new designs of reactor.

The consortium is led by IRSN, the French Technical Support Organisation and has all the key European players involved in Gen IV reactor research.

Professor Peter Storey, from the Dalton Nuclear Institute, will lead the development of a roadmap for FAST reactor safety R&D and, with Dr Tim Ware from the School of Physics and Astronomy, will be involved in identifying safety features of Gen IV reactors, identifying accident initiators and disseminating findings of the project.

Professor Storey said: “Involvement in this prestigious EC funded project on advanced nuclear reactors is of strategic importance to the Dalton Nuclear Institute.

“It builds on our involvement in two other European projects in this area, draws upon our high expertise in reactor technology and nuclear safety and involves the Institute in helping set the agenda for ground breaking research."

The project will start in early 2012 and last for two years. It will build upon other EC funded Gen IV projects that the University is already involved in and will act as a key step in engaging specialist expertise within the Centre for Nuclear Energy Technology (C-NET) in European projects that will grow as interest in advanced systems also grows.

The Generation IV International Forum (GIF) was chartered in 2001 to lead the collaborative efforts of the world's leading nuclear technology nations to develop next generation nuclear energy systems to meet the world's future energy needs.

The GIF Charter has been signed by Argentina, Brazil, Canada, France, Japan, the Republic of Korea, South Africa, the United Kingdom, the United States (2001), Switzerland (2002), Euratom (2003), the People's Republic of China and the Russian Federation (2006).

Among the signatories of the Charter, Canada, Euratom, France, Japan, the People’s Republic of China, the Republic of Korea, Switzerland and the United States have signed a Framework Agreement (FA) formally agreeing to participate in the development of one or more Generation IV systems.

These revolutionary “Generation IV” nuclear energy systems will be developed in the context of eight technological goals:

• to provide sustainable energy generation that meets clean air objectives and provides long-term availability of systems and effective fuel utilization for energy production
• to minimize and manage nuclear waste and notably reduce the long-term stewardship burden, thereby improving protection for the public health and the environment
• to have a clear life-cycle cost advantage over other energy sources
• to have a level of financial risk comparable to other energy projects
• to excel in safety and reliability
• to have a very low likelihood and degree of reactor core damage
• to eliminate the need for offsite emergency response
• to be very unattractive and the least desirable route for diversion or theft of weapons-usable materials, and provide increased physical protection against acts of terrorism.

Six nuclear energy systems have been selected by GIF for further development. In principle, these systems should be marketable or deployable from 2030 onwards.

Inside the innards of a nuclear reactor: Tiny robots may monitor underground pipes for radioactive leaks

MIT News

July 21, 2011

As workers continue to grapple with the damaged Fukushima Daiichi nuclear powerplant in Japan, the crisis has shone a spotlight on nuclear reactors around the world. In June, The Associated Press released results from a yearlong investigation, revealing evidence of “unrelenting wear” in many of the oldest-running facilities in the United States.

That study found that three-quarters of the country’s nuclear reactor sites have leaked radioactive tritium from buried piping that transports water to cool reactor vessels, often contaminating groundwater. According to a recent report by the U.S. Government Accountability Office, the industry has limited methods to monitor underground pipes for leaks.

“We have 104 reactors in this country,” says Harry Asada, the Ford Professor of Engineering in the Department of Mechanical Engineering and director of MIT’s d’Arbeloff Laboratory for Information Systems and Technology. “Fifty-two of them are 30 years or older, and we need immediate solutions to assure the safe operations of these reactors.”

Asada says one of the major challenges for safety inspectors is identifying corrosion in a reactor’s underground pipes. Currently, plant inspectors use indirect methods to monitor buried piping: generating a voltage gradient to identify areas where pipe coatings may have corroded, and using ultrasonic waves to screen lengths of pipe for cracks. The only direct monitoring requires digging out the pipes and visually inspecting them — a costly and time-intensive operation.

Now Asada and his colleagues at the d’Arbeloff Laboratory are working on a direct monitoring alternative: small, egg-sized robots designed to dive into nuclear reactors and swim through underground pipes, checking for signs of corrosion. The underwater patrollers, equipped with cameras, are able to withstand a reactor’s extreme, radioactive environment, transmitting images in real-time from within.

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