The “Versatile Fast Neutron Source”: A Misguided Nuclear Reactor Project

, Director of Nuclear Power Safety, Climate & Energy | February 15, 2018, 4:10 pm EDT
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The Union of Concerned Scientists (UCS) supports a moderate level of Department of Energy (DOE) research funding to make nuclear power safer and more secure—for example the agency’s program to develop accident tolerant fuels for nuclear reactors. Conversely, UCS does not support programs that not only would cost a lot of money, but also could make nuclear power more dangerous and less secure. That’s why the organization is troubled by a bill that was passed by the House of Representatives on February 13.

The bill in question, H.R. 4378, authorizes the secretary of energy to spend nearly $2 billion over the next seven years to build what’s called a “versatile reactor-based fast neutron source.” As its name indicates, the primary purpose of this facility would be to provide a source of high-energy neutrons to help researchers develop fuels and materials for a class of advanced nuclear reactors called fast reactors.

What is it?

What may not be clear from the name is that this facility itself would be an experimental fast reactor, likely fueled with weapon-usable plutonium. Compared to conventional light-water reactors, fast reactors are less safe, more expensive, and more difficult to operate and repair. But the biggest problem with this technology is that it typically requires the use of such weapon-usable fuels as plutonium, increasing the risk of nuclear terrorism. Regardless, the House passed the bill with scant consideration of the risks and benefits of building it. Hopefully, the Senate will conduct a due diligence review before taking up a companion bill. Caveat emptor.

Based on what little public information there is available about the plans for this facility, it would be a fast reactor of at least 300 thermal megawatts (or about 120 MW of electricity if it is also used for power generation). This power level is the minimum necessary to achieve the desired rate of neutron production. This would make the reactor about five times larger than the last experimental fast reactor operated in the United States, the EBR-II, which shut down in 1994. One proposed design, called FASTER, would have a peak power density three times higher than the EBR-II, making it much more challenging to remove heat from the core. This design would require about 2.6 metric tons of metallic fuel containing about 500 kilograms of plutonium per year. One third of the reactor fuel would be replaced every 100 days. (The DOE also is apparently considering a different fast reactor design that would use high-assay, low-enriched uranium fuel, but this material is in short supply and a new production source would have to be established. In any case, the DOE has not yet determined if it is feasible to use low-enriched uranium.)


The amount of funding authorized by H.R. 4378 for designing and constructing this fast reactor is less than 60 percent of its estimated cost of $3.36 billion, and the aggressive timeline mandated by the bill, which calls for full operation by the end of 2025, is significantly shorter than the optimistic 11- to 13-year schedule anticipated by its designers. By low-balling the initial authorization and construction time, H.R. 4378’s sponsors may have been trying to make it more palatable, but they are also undermining their project.

It’s also important to keep in mind that the estimated cost of $3.36 billion is just a fraction of the project’s total cost. It does not include a facility to fabricate the plutonium fuel, which could add billions to the final price tag. The current cost estimate for the DOE’s Mixed Oxide Fuel Fabrication Facility at the Savannah River Site, which is being built to convert 2 metric tons of plutonium annually into fuel for operating light-water reactors, is more than $17 billion. Then there’s the cost of managing and disposing of the several tons of plutonium-containing spent fuel that would accumulate each year at the fast reactor site.

We’ve been down this road before. As the Union of Concerned Scientists reported last year, the DOE’s Idaho National Laboratory has been unable to deal effectively with the spent fuel legacy of the defunct EBR-II, which is similar to but less hazardous than the spent fuel that the FASTER test reactor would produce because it contains far less plutonium. (Only a small fraction of the fuel rods irradiated in the EBR-II were fabricated with plutonium.)

The project’s high cost and risks might be justified if there were a critical need for a new fast neutron source in the United States. That’s simply not the case.


The primary purpose of the facility would be to assist private companies that want to develop and sell fast reactors, but most of those companies aren’t sold on the idea. According to a report last year by the DOE’s Nuclear Energy Advisory Committee, “some of the industry representatives (e.g., AREVA, GE-Hitachi, TerraPower, Westinghouse, and Terrestrial Energy) who have an interest in pursuing advanced reactors … [are] of the view … that a test facility was not essential for the commercial advancement of their technology.” Moreover, the DOE hasn’t determined that there is an actual need for the project. On February 6, Principal Deputy Assistant Secretary for Nuclear Energy Edward McGinnis told the House Energy and Commerce Committee that “a decision whether or not to deploy an advanced fast spectrum test reactor has not been made.…”

H.R. 4378’s mandate that the DOE to proceed with design and construction, therefore, is premature at best.

Finally, what agency will oversee the safety and security of this risky project? The DOE. By designating this reactor as a neutron source, and building it at a DOE site, it will be exempt from licensing and oversight by the Nuclear Regulatory Commission. While NRC licensing is far from perfect, it would be far superior to DOE self-regulation.

To summarize, H.R. 4378 authorizes constructing a fast reactor without assessing the need or evaluating its costs and benefits. It compels the DOE to build an experimental fast reactor, using an experimental fuel, at a scale and power density that has never been demonstrated, on a rushed schedule, with insufficient funding.

This is simply the wrong way to pursue nuclear energy research and development. Instead, DOE should undertake projects only if they pass a rigorous peer review and make safety and security a priority.

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  • Daniel Siefman

    For a group of scientists there sure are a lot of unsubstantiated claims. For instance,

    “The biggest problem with this technology is that it typically requires the use of such weapon-usable fuels as plutonium, increasing the risk of nuclear terrorism”

    Increased risk? By how much? Of course if there’s more Pu in the world there’s a higher risk. But does this change from a one in a billion risk to on in one hundred? Or maybe one in a billion to two in a billion? For “scientists” this is just manipulative. The DOE already has ALL of our weapons grade Pu. Do you think by adding some reactor fuel (which will have tons of fission products in it and not be very useful for weapons) really increases the risk to a concerning level?

    If you want to be taken seriously by other scientists, please use numbers rather than suggestive language.

    • Edwin Lyman

      Dear Mr. Siefman,

      Thanks for your message. First, I’d like to point out that there is a consensus among analysts that there is no technically valid approach to quantify the risks of security events because of the role of human agency in initiating and influencing the course of such events. For example, see the National Academy of Sciences’ report on this: (unfortunately, only an unclassified summary is available). For this reason, we tend to avoid attempting to quantify the unquantifiable.

      In qualitative terms, the fast reactor project will increase the risks of nuclear terrorism both directly and indirectly. Assuming, as you do, that the source of the plutonium for the reactor would be the DOE’s excess weapons-grade plutonium stockpile, the risk of theft or diversion would increase due to the increased handling, processing and transportation necessary to convert that material to reactor fuel and utilize it in the reactor. DOE’s physical security program is not perfect and is under the same fiscal pressure as all other aspects of lab operations. That is why we support the administration’s plan to dispose of the excess weapons-grade plutonium stockpile through the simplest method available – -“dilute and dispose.”
      The indirect impact of the program would be a signal to the rest of the world that fast reactors hold promise and are worthy of large government investments–despite the cost and dangers of the technology. This could encourage other countries to begin or restart programs to develop fast reactors and associated fuel cycles, including spent fuel reprocessing. That would lead to further strain on the international nonproliferation regime and result in an increase in the risks of nuclear terrorism and proliferation worldwide.
      I hope this addresses your questions.
      Best regards,
      Edwin Lyman
      Senior Scientist
      Union of Concerned Scientists

      • Daniel Siefman


        Thank you for your reply. I understand very well the difficulties of quantifying human events, but efforts can be made (see probabilistic risk assessment). Assume some probability distributions, use Bayes’ theory, make an effort. My issue is with the language that is employed. If this was given to a decision maker without technical knowledge, they would understand that the risk of nuclear terrorism is increased based on, for example, this sentence “But the biggest problem with this technology is that it typically requires the use of such weapon-usable fuels as plutonium, increasing the risk of nuclear terrorism. ” Is this a real increased risk? By writing this article, you may have increased the risk that the existence of this reactor causes nuclear terrorism because know more people know it exists. I can’t quantify this and it is impossible to contradict. There’s a fault in logic somewhere here that, for me, causes this article to be unconvincing.

        I find fast reactors to be very much worth the “risk” they entail, however unquantifiable it is. Risk is a pessimistic approach to technology and advancing society. Fast reactors come with great rewards when done properly and will inherently increase the risk of nuclear terrorism, but to your unknown degree. It’s easy to be safe and just fight against anything with risk, but then we lock ourselves in a bunker to avoid any, however small, risk.

        Summary: Give quantifying the risk a shot with whatever models and approximations you want rather than just using ambiguous rhetoric saying that “risk increases.” I, personally, could then be convinced by your argument.