The Bill Gates-backed $9 billion sodium cooled fast nuclear reactor planned for Kemmerer Wyoming is worse than unnecessary, according to the Union of Concerned Scientists. It’s dangerous.
In comments to the U.S. Nuclear Regulatory Commission on TerraPower’s 345-MW Natrium reactor request for a construction permit, UCS nuclear physicist Edwin Lyman says Kemmerer Unit 1 “is something that the world simply does not need. If it ever operates, which is highly unlikely, it will pose an unacceptable menace to domestic and international safety and security.”
Lyman adds, “Unfortunately, due to the incredibly poor judgment and lack of understanding of the project’s backers, including TerraPower, which is being played for a patsy by a cadre of fast reactor enthusiasts within the Department of Energy and its national lab system, it continues to move forward.” The project has a $2 billion partnership agreement with DOE’s Advanced Reactor Demonstration Program.
Lyman, UCS director of nuclear power safety, first focuses on “fast” reactors, which use fast, unmoderated neutrons at an enrichment level of up to 20% to sustain a chain reaction. Fast reactors, says Lyman, “have numerous, fundamental design flaws which render them significantly more dangerous than light-water reactors. However, TerraPower and other promoters of fast reactors continue to disseminate dangerous misinformation about them, misleading policymakers and the public about these risks.”
The construction permit application for Kemmerer, writes Lyman, “fails to evaluate the most severe accident scenarios that are known to be credible for fast reactors.” One of these unaddressed risks is “unprotected loss-of-flow (ULOF ).” If the pumps that circulate the liquid sodium fail, he explains, reactors such as TerraPower’s Natrium “depend on artificial ‘coast-down’ mechanisms” to buy time for the machine to avoid a loss of coolant disaster.
“These events can lead to ten-fold increases in power that can cause a Chernobyl-like destruction of the reactor core and its confinement.” — Edwin Lyman
But if the cool-down fails, the dreaded positive void coefficient of reactivity can take hold, where the coolent is lost and the reactor heats up “leading to bulk sodium boiling, fuel melt, and further rapid power increases on the order of tens of seconds. These events can lead to ten-fold increases in power that can cause a Chernobyl-like destruction of the reactor core and its confinement. In such events, a significant fraction of the core radionuclide inventory can be expected to be expelled to the environment, especially for a plant without a physical containment that can (to a limited extent) withstand the force of the core and coolant explosion.”
The Kemmerer application downplays the scale of the release of radionuclides in a severe Kemmerer accident, says Lyman. The application falsely asserts that the releases are considerably less than a modeled catastrophic accident at one of Dominion’s 859-MW Surry pressurized water reactors in Virginia including a containment failure and “very large” release of radioactive iodine, cesium, and strontium.
“However,” writes Lyman, “the actual release fractions for fast reactor severe accidents with core melt are considerably higher than these values.” That’s based on the Department of Energy’s environmental impact statement for its proposed Versatile Test Reactor, a fast reactor similar to the proposed Natrium machine. The environmental report for Kemmerer 1 “is quite nonconservative, and simply not credible, when compared to the DOE” virtual test reactor, Lyman concludes.
The TerraPower application also misplaces an analysis of what might be done to mitigate a severe accident. The application would postpone this to when the reactor construction is complete and the owners are seeking NRC approval to operate the unit, according to Lyman.
He argues that “it defies logic to defer consideration of design alternatives until after the preliminary design has been approved and, moreover, construction is underway or nearly complete. This is particularly important for major design alternatives that cannot be simply tacked on to a plant in the late stages of construction, such as a physical, pressure-resisting, low-leakage containment.”
The design of Kemmerer, according to Lyman, also results in “wasteful use of the natural uranium resource. Based on the publicly reported enrichment and burnup of the Natrium Type 1 fuel, one can calculate that the reactor will require about 550 metric tons of natural uranium per GWe-yr, or about three times as much as a light-water reactor uses for typical burnups.” TerraPower says it plans to develop a higher burnup fuel, but this is “remote and speculative to assume that it will be successful over the timeframe considered” by the environmental analysis according to Lyman.
The TerraPower environmental review of spent fuel storage is also a problem, writes Lyman, because the fuel is so different than the low-enriched uranium spent fuel in the general environmental impact statement for light water reactors. He notes that “there is very little operating experience with similar spent fuels to inform predictions of its storage behavior in the long-term. Thus the EIS must contain a site-specific and material-specific analysis of the safety and security of indefinite storage, fully accounting for uncertainties, in order to satisfy the legal requirements.”
Finally, the Kemmerer filing must address “radiological sabotage and theft” of the reactor fuel, as “there is very little operating experience with similar spent fuels to inform predictions of its storage behavior in the long-term. Thus the EIS must contain a site-specific and material-specific analysis of the safety and security of indefinite storage, fully accounting for uncertainties, in order to satisfy the legal requirements.”
Lyman earned an undergraduate degree in physics from NYU in 1986 and a Ph.D. in physics from Cornell University in 1992, with an emphasis on string theory and high-energy physics. He did post-doctoral work at Princeton University, focusing on science and security policy including management of the stockpiles of plutonium left over from the end of the Cold War.
–Kennedy Maize