The integral fast reactor (IFR), originally the advanced liquid-metal reactor (ALMR), is a design for a nuclear reactor using fast neutrons and no neutron moderator (a "fast" reactor). IFRs can breed more fuel and are distinguished by a nuclear fuel cycle that uses reprocessing via electrorefining at the reactor site. The IFR was a sodium-cooled fast reactor (SFR) is its closest surviving fast breeder reactor, a type of Generation IV reactor.
The U.S. Department of Energy (DOE) began designing an IFR in 1984 and built a prototype, the Experimental Breeder Reactor II. On April 3, 1986, two tests demonstrated the safety of the IFR concept. These tests simulated accidents involving loss of coolant flow. Even with its normal shutdown devices disabled, the reactor shut itself down safely without overheating anywhere in the system. The IFR project was canceled by the US Congress in 1994, three years before completion.The IFR at Argonne National Laboratory, www.ne.anl.gov, accessed 1 November 2022
S-PRISM (from SuperPRISM), also called PRISM (power reactor innovative small module), is the name of a nuclear power plant design by GE Vernova Hitachi Nuclear Energy based on the IFR. In 2022, GE Vernova Hitachi Nuclear Energy and TerraPower began exploring locating five Natrium SFR-based nuclear power plants in Kemmerer, Wyoming; the design incorporates a PRISM reactor plus TerraPower's Traveling Wave design with a molten salt storage system.
History Research on IFR reactors began in 1984 at Argonne National Laboratory in Argonne, Illinois, as a part of the U.S. Department of Energy's national laboratory system, and currently operated on a contract by the University of Chicago.
Argonne previously had a branch campus named "Argonne West" in Idaho Falls, Idaho, that is now part of the Idaho National Laboratory. In the past, at the branch campus, physicists from Argonne West built what was known as the Experimental Breeder Reactor II (EBR-II). In the meantime, physicists at Argonne designed the IFR concept, and it was decided that the EBR-II would be converted to an IFR. Charles Till, a Canadian physicist from Argonne, was the head of the IFR project, and Yoon Chang was the deputy head. Till was positioned in Idaho, while Chang was in Illinois. Chang later served as acting director of Argonne.
The IFR concept is described in detail in Plentiful Energy: The Story of the Integral Fast Reactor.
Cancellation
With the election of President Bill Clinton in 1992, and the appointment of Hazel O'Leary as the Secretary of Energy, there was pressure from the top to cancel the IFR. Senator John Kerry (D-MA) and O'Leary led the opposition to the reactor, arguing that it would be a threat to non-proliferation efforts, and that it was a continuation of the Clinch River Breeder Reactor Project that had been canceled by Congress. Charles Till related that when he told Frank N. von Hippel, a science advisor to President Clinton, that it would cost more to terminate the research program and destroy the reactor than to finish the program and mothball the reactor, von Hippel replied "I know; it's a symbol. It has to go."
Simultaneously, in 1994 Energy Secretary O'Leary awarded the lead IFR scientist with $10,000 and a gold medal, with the citation stating his work to develop IFR technology provided "improved safety, more efficient use of fuel and less radioactive waste".
IFR opponents also presented a reportReport of investigation into allegations of retaliation for raising safety and quality of work issues regarding Argonne National Laboratory's Integral Fast Reactor Project, Report Number DOE/NS-0005P, 1991 Dec 01 OSTI Identifier OSTI ID: 6030509, by the DOE's Office of Nuclear Safety regarding a former Argonne employee's allegations that Argonne had retaliated against him for raising concerns about safety, as well as about the quality of research done on the IFR program. The report received international attention, with a notable difference in the coverage it received from major scientific publications. The British journal Nature entitled its article "Report backs whistleblower", and also noted conflicts of interest on the part of a DOE panel that assessed IFR research.Report backs whistleblower, Nature 356, 469 (9 April 1992) In contrast, the article that appeared in Science was entitled "Was Argonne Whistleblower Really Blowing Smoke?".Science, Vol. 256, No. 5055, 17 April 1992
Since 2000
In 2001, as part of the Generation IV roadmap, the DOE tasked a 242-person team of scientists from DOE, UC Berkeley, Massachusetts Institute of Technology (MIT), Stanford, ANL, Lawrence Livermore National Laboratory, Toshiba, Westinghouse, Duke, EPRI, and other institutions to evaluate 19 of the best reactor designs on 27 different criteria. The IFR ranked #1 in their study which was released April 9, 2002.Generation IV roadmap. Evaluation Summaries. 2002 18 slides – some illegible
At present, there are no integral fast reactors in commercial operation. However, the BN-800 reactor, a very similar fast reactor operated as a burner of plutonium stockpiles, became commercially operational in 2016.
Technical overview
The IFR is cooled by liquid sodium and fueled by an alloy of uranium and plutonium. The fuel is contained in steel cladding with liquid sodium filling in the space between the fuel and the cladding. A void above the fuel allows helium and radioactive xenon to be collected safely without significantly increasing pressure inside the fuel element, and also allows the fuel to expand without breaching the cladding, making metal rather than oxide fuel practical. The advantages of liquid sodium coolant, as opposed to liquid metal lead, are that liquid sodium is far less dense and far less viscous (reduced pumping costs), is not corrosive (via dissolution) to common steels, and creates essentially no radioactive neutron activation byproducts. The disadvantage of sodium coolant, as opposed to lead coolant, is that sodium is chemically reactive, especially with water or air. Lead may be substituted for the eutectic alloy of lead and bismuth, as used as reactor coolant in Soviet Alfa-class submarines.
Basic design decisions
Metallic fuel Metal fuel with a sodium-filled void inside the cladding to allow fuel expansion has been demonstrated in EBR-II. Pyroprocessing is primarily used for the reprocessing of metallic fuel.
Fabrication of metallic fuel is easier and cheaper than ceramic (oxide) fuel, especially under remote handling conditions.
Metallic fuel has better heat conductivity and lower heat capacity than oxide, which has safety advantages.
Sodium coolant The use of liquid metal coolant removes the need for a pressure vessel around the reactor. Sodium has excellent nuclear characteristics, a high heat capacity and heat transfer capacity, low density, low viscosity, a reasonably low melting point and a high boiling point, and excellent compatibility with other materials including structural materials and fuel. The high heat capacity of the coolant and the elimination of water from the reactor core increase the inherent safety of the core.
Pool design rather than loop Containing all of the primary coolant in a pool produces several safety and reliability advantages.
Onsite reprocessing using pyroprocessing Reprocessing is essential to achieve most of the benefits of a fast reactor, improving fuel usage and reducing radioactive waste by several orders of magnitude.
Onsite processing is what makes the IFR "integral". This and the use of pyroprocessing both reduce proliferation risk.
Pyroprocessing (using an electrorefiner) has been demonstrated at EBR-II as practical on the scale required. Compared to the PUREX aqueous process, it is economical in capital cost, and is unsuitable for the production of weapons material, again unlike PUREX which was developed for weapons programs.
Pyroprocessing makes metallic fuel the fuel of choice. The two decisions are complementary.
Advantages Breeder reactors (such as the IFR) could in principle extract almost all of the energy contained in uranium or thorium, decreasing fuel requirements by nearly two orders of magnitude compared to traditional once-through reactors, which extract less than 0.65% of the energy in mined uranium, and less than 5% of the enriched uranium with which they are fueled. This could greatly dampen concern about fuel supply or energy used in mining.
What is more important today is why fast reactors are fuel-efficient: because fast neutrons can fission or "burn out" all the transuranic waste components. Transuranic waste consists of actinides – reactor-grade plutonium and minor actinides – many of which last tens of thousands of years or longer and make conventional nuclear waste disposal so problematic. Most of the radioactive fission products produced by an IFR have much shorter half-lives: they are intensely radioactive in the short term but decay quickly. Through many cycles, the IFR ultimately causes 99.9% of the uranium and transuranium elements to undergo fission and produce power; so, its only waste is the nuclear fission products. These have much shorter half-lives; in 300 years, their radioactivity will fall below that of the original uranium ore.Nucleus-4-2007 pg 15 see SV/g chart, www.stralsakerhetsmyndigheten.se The fact that 4th generation reactors are being designed to use the waste from 3rd generation plants could change the nuclear story fundamentally—potentially making the combination of 3rd and 4th generation plants a more attractive energy option than 3rd generation by itself would have been, both from the perspective of waste management and energy security.
"Integral" refers to on-site reprocessing by electrochemical pyroprocessing. This process separates spent fuel into 3 fractions: uranium, plutonium isotopes and other transuranium elements, and nuclear fission products. The uranium and transuranium elements are recycled into new fuel rods, and the fission products are eventually converted to glass and metal blocks for safer disposal. Because the combined transuranium elements and the fission products are highly radioactive, fuel-rod transfer and reprocessing operations use robotic or remote-controlled equipment. An additional claimed benefit of this is that since fissile material never leaves the facility (and would be lethal to handle if it did), this greatly reduces the proliferation potential of possible diversion of fissile material.
Safety In traditional light-water reactors (LWRs) the core must be maintained at a high pressure to keep the water liquid at high temperatures. In contrast, since the IFR is a liquid metal cooled reactor, the core could operate at close to ambient pressure, dramatically reducing the danger of a loss-of-coolant accident. The entire reactor core, heat exchangers, and primary cooling pumps are immersed in a pool of liquid sodium or lead, making a loss of primary coolant extremely unlikely. The coolant loops are designed to allow for cooling through natural convection, meaning that in the case of a power loss or unexpected reactor shutdown, the heat from the reactor core would be sufficient to keep the coolant circulating even if the primary cooling pumps were to fail.