Fast Neutron Reactors

Nuclear Waste can be a solution not a problem
Advanced Fast Neutron Reactors (AFR) are fast breeder reactors that can use nuclear “waste” for fuel — the spent nuclear fuel that has been discarded from conventional nuclear plants can power AFR’s, producing clean electricity while destroying radioactive waste.

“Fast-neutron reactors could extract much more energy from recycled nuclear fuel, minimize the risks of weapons proliferation and markedly reduce the time nuclear waste must be isolated.

“If developed sensibly, nuclear power could be truly sustainable and essentially inexhaustible and could operate without contributing to climate change. In particular, a relatively new form of nuclear technology could overcome the principal drawbacks of current methods—namely, worries about reactor accidents, the potential for diversion of nuclear fuel into highly destructive weapons, the management of dangerous, long-lived radioactive waste, and the depletion of global reserves of economically available uranium. This nuclear fuel cycle would combine two innovations: pyrometallurgical processing (a high-temperature method of recycling reactor waste into fuel) and advanced fast-neutron reactors capable of burning that fuel. With this approach, the radioactivity from the generated waste could drop to safe levels in a few hundred years, thereby eliminating the need to segregate waste for tens of thousands of years…”
Smarter Use of Nuclear Waste  size: 575 Kb – 8 pages
By William H. Hannum,
    Gerald E. Marsh and
    George S. Stanford

 Fast Neutron Reactors — “Several countries have research and development programs for improved Fast Breeder Reactors (FBR), which are a type of Fast Neutron Reactor. These use the uranium-238 in reactor fuel as well as the fissile U-235 isotope used in most reactors.
      “Natural uranium contains about 0.7 % U-235 and 99.3 % U-238. In any reactor, the U-238 component is turned into several isotopes of plutonium during its operation. Two of these, Pu 239 and Pu 241, then undergo fission in the same way as U 235 to produce heat.  In a fast neutron reactor, this process is optimized so that it can ‘breed’ fuel, often using a depleted uranium blanket around the core. FBRs can utilize uranium at least 60 times more efficiently than a normal reactor.
Advanced Nuclear Power Reactors World Nuclear Association

“The American Nuclear Society believes that the development and deployment of advanced nuclear reactors based on fast-neutron fission technology is important to the sustainability, reliability, and security of the world’s long-term energy supply. Of the known and proven energy technologies, only nuclear fission can provide the large quantities of energy required by industrial societies in a sustainable and environmentally acceptable manner.

“Natural uranium mined from the earth’s crust is composed primarily of two isotopes: 99.3% is U- 238, and 0.7% is the fissile U-235. Nearly all current power reactors are of the “thermal neutron” design, and their capability to extract the potential energy in the uranium fuel is limited to less than 1% of that available. The remainder of the potential energy is left unused in the spent fuel and in the uranium, depleted in U-235, which remains from the process of enriching the natural uranium in the isotope U-235 for use in thermal reactors. With known fast reactor technology, this unutilized energy can be harvested, thereby extending by a hundred-fold the amount of energy extracted from the same amount of mined uranium.

“Fast reactors can convert U-238 into fissile material at rates faster than it is consumed making it economically feasible to utilize ores with very low uranium concentrations and potentially even uranium found in the oceans.1–3 A suitable technology has already been proven on a small scale.4 Used fuel from thermal reactors and the depleted uranium from the enrichment process can be utilized in fast reactors, and that energy alone would be sufficient to supply the nation’s needs for several hundred years.

“Fast reactors in conjunction with fuel recycling can diminish the cost and duration of storing and managing reactor waste with an offsetting increase in the fuel cycle cost due to reprocessing and fuel refabrication. Virtually all long-lived heavy elements are eliminated during fast reactor operation, leaving a small amount of fission product waste that requires assured isolation from the environment for less than 500 years.4

“Although fast reactors do not eliminate the need for international proliferation safeguards, they make the task easier by segregating and consuming the plutonium as it is created. The use of onsite reprocessing makes illicit diversion from within the process highly impractical. The combination of fast reactors and reprocessing is a promising option for reasons of safety, resource utilization, and proliferation resistance.5

“Reaping the full benefits of fast reactor technology will take a decade or more for a demonstration reactor, followed by buildup of a fleet of operating power stations. For now and in the intermediate-term future, the looming short-term energy shortage must be met by building improved, proven thermal-reactor power plants. To assure longer-term energy sustainability and security, the American Nuclear Society sees a need for cooperative international efforts with the goal of building a fast reactor demonstration unit with onsite reprocessing of spent fuel.”
American Nuclear Society Position Statement
Fast Reactor Technology: A Path to Long-Term Energy Sustainability
 size: 30 Kb – 2 pages

Is nuclear energy renewable?

Generally “renewable” relates to harnessing energy from natural forces which are renewed by natural processes, especially wind, waves, sun, and rain, but also heat from the Earth’s crust and mantle.  And because it shares many attributes with technologies harnessing these natural forces — for instance, radioactive decay produces much of the heat harnessed geothermally, nuclear energy is sometimes classified with them.
      But there are other reasons to call nuclear energy “renewable”.  In any nuclear reactor, the input fuel is normally uranium-235 (U-235) which is part of a much larger mass of uranium – mostly U-238.  This U-235 is progressively ‘burned’ over about three years to yield a lot of heat.  But about one-third of the energy yield comes from something which is not initially loaded in: plutonium 239 (Pu-239), which behaves almost identically to U-235.  This is because the fission of U-235 causes some of the U-238 to turn into Pu-239, so about half of the U-235 used actually renews itself by producing Pu-239 from the otherwise waste material U-238. So, it’s partly Renewable in this situation.
      This raises the possibility of whether U-235 can be made fully Renewable.  In fact, it can, by optimizing the process in another kind of reactor that can be configured to “breed” more Pu-239 than it consumes (by way of U-235 + Pu-239), so that the system can run indefinitely. While it can produce more fuel than it uses, there does need to be steady input of reprocessing activity to separate the fissile plutonium from the uranium and other materials.  This is fairly capital-intensive but well-proven and basically straightforward.  The used fuel from the whole process is recycled and the usable part of it increases incrementally.
Apart from this, there is thorium, which is four times as abundant as uranium. Using a similar process to the breeder reactor, thorium can produce U-233, which is fissile.  This process is not yet commercialized, but it works and if there were ever a pressing need for it, the development would be accelerated.—Sustainable Energy World Nuclear Association

Future Nuclear Fission Power Plant Technology — Generation IV

Scientists at Argonne National Laboratory are developing a new generation of Nuclear Reactors. The technology is called IFR which stands for Integral Fast Reactor. The technology is also called AFR which stands for Advanced Fast Reactor.

Read what a nuclear physicist says about Integral Fast Reactors:
Integral Fast Reactors: Source of Safe, Abundant, Non-Polluting Power by George S. Stanford, Ph.D. nuclear reactor physicist, now retired from Argonne National Laboratory after a career of experimental work pertaining to power-reactor safety.

“There’s another huge benefit, of course. If nothing better comes along, the IFR can supply the world with pollution-free energy for thousands of years.” — George Stanford, Ph.D.

Passively safe reactors rely on nature to keep them cool by David Baurac, director of public information for the Argonne National Laboratory.

Argonne’s advanced fast reactor (AFR) has demonstrated its passive safety conclusively on a working prototype. “Back in 1986, we actually gave a small prototype advanced fast reactor a couple of chances to melt down,” says Argonne nuclear engineer Pete Planchon, who led the 1986 tests. “It politely refused both times.”

Read more about Integral/Advanced Fast Reactors:
Dr. Charles Till Nuclear physicist and associate lab director at Argonne National Laboratory West in Idaho. He is co-developer of the Integral Fast Reactor, an inherently safe nuclear reactor with a closed fuel cycle.

“The radioactive isotopes in spent nuclear fuel are of two types: fission products and actinides. The fission products as a group have an effective half-life of about thirty years. It takes only about 500 years for their toxicity to drop below that of the natural uranium ore from which their parent atoms came.

“The actinides, on the other hand, have long half-lives, and their toxicity level is orders of magnitude greater for millions of years. In preprocessing, the actinides are easily recovered and recycled back into the reactor. This reduces the effective lifetime of the nuclear waste from tens of thousands of years to a few hundred, and meanwhile, energy is generated by fissioning the actinides.

“A repository is still needed, but its performance specifications can be much less stringent without the long-lived actinides. Furthermore, the repository’s capacity is increased substantially because the long-term heat source is eliminated. And the disposal site does not become a geological plutonium deposit, waiting to be mined by a would-be bomb-maker in the distant future, when the isotopic suitability of the plutonium for weapons will have improved considerably.

“Nonproliferation: The nuclear materials in the closed fuel cycle cannot be used directly in weapons, because pyroprocessing is unable to separate pure plutonium. Instead, the plutonium is mixed at all times with uranium, other actinides, and fission products. The mixture is protected against theft or unauthorized diversion because it is dauntingly radioactive and must be handled remotely with sophisticated, specialized equipment.

“Pyroprocessing systems are compact, and the fuel-cycle facility can easily be collocated with the reactor, all but eliminating the need to transport nuclear fuel.”

Yoon I. Chang
Adapted from a talk delivered at Argonne National Laboratory, Titled, Advanced Fast Reactor: A Next-Generation Nuclear Energy Concept

Argonne National Laboratory, along with the Idaho National Laboratory (INL), is leading U.S. participation in the Generation IV project, an international effort to develop the next generation of Closed fuel cycle advanced nuclear reactors.

Six Generation IV technology concepts have been selected for R&D

With a robust R&D effort, most of those concepts could be developed and deployed by the year 2020. And each is aimed at meeting projected power needs in the mid-21st century. For example, several concepts—most prominently, the very-high-temperature gas-cooled reactor—have a higher output temperature and are therefore attractive for process heat applications. These concepts also would be well-suited to produce hydrogen in quantity and at an attractive price. Nuclear power currently is one of the most attractive means of large-scale production of hydrogen.

Five of the six Generation IV technology concepts are being pursued at varying levels of effort based on their technology status and potential to meet program and national goals. Two are thermal neutron spectrum systems (Very-High-Temperature Reactor (VHTR) and Supercritical-Water-Cooled Reactor (SCWR)) with coolants and temperatures that enable hydrogen or electricity production with high efficiency, and three are fast neutron spectrum systems (Gas-Cooled (GFR), Lead-Cooled (LFR), and Sodium-Cooled (SFR) fast reactors) that will enable more effective management of actinides through recycling of most components in the discharged fuel.

The U.S. is not currently researching the molten salt reactor (MSR). Japan is focusing on the sodium-cooled reactor (MSR), with its significant potential for recycling spent nuclear fuel in the near future.

The six Gen IV reactor concepts are shown with illustrations:

Gas-Cooled Fast Reactor (GFR)
features a fast-neutron-spectrum, helium-cooled reactor, and closed fuel cycle.

Molten Salt Reactor (MSR)
produces fission power in a circulating molten salt fuel mixture with an epithermal-spectrum reactor and a full actinide recycle fuel cycle.

Sodium-Cooled Fast Reactor (SFR)
features a fast-spectrum, sodium-cooled reactor, and closed fuel cycle for efficient management of actinides and conversion of fertile uranium.

Lead-Cooled Fast Reactor (LFR)
features a fast-spectrum lead or lead/bismuth eutectic liquid metal-cooled reactor and a closed fuel cycle for efficient conversion of fertile uranium and management of actinides.

Supercritical-Water-Cooled Reactor (SCWR)
is a high-temperature, high-pressure water-cooled reactor that operates above the thermodynamic critical point of water (374 degrees Celsius, 22.1 MPa, or 705 degrees Fahrenheit, 3208 psi).

Very-High-Temperature Reactor (VHTR)
a graphite-moderated, helium-cooled reactor with a once-through uranium fuel cycle, designed to supply heat with core outlet temperatures of 1,000 degrees Celsius, which enables applications such as hydrogen production or process heat for the petrochemical industry or others.

INL team helps pave the way to Generation IV reactor “Fourth generation nuclear reactors, the nuclear power plants of tomorrow will provide safer, less expensive and more environmentally friendly energy. A critical step in developing new Very High-Temperature Reactors (VHTR) is certifying the graphite that is used in many parts of the reactor’s core. In recent years, it has become necessary to develop new nuclear-grade graphite and certify it for use in the next generation of gas-cooled nuclear reactors… nuclear experts envision two different versions of gas-cooled VHTRs for next-generation use. Both designs will require large amounts of high-quality graphite.”

Leave a Comment