"Advanced" Isn't Always Better: Assessing the Safety, Security, and Environmental Impacts of Non-Light-Water Nuclear Reactors*

If nuclear power is to play an expanded role in helping to mitigate climate change, newly built reactors must be demonstrably safer, more secure, and more economical than current-generation reactors. One approach to improving nuclear power has been to pursue the development of non-light-water nuclear reactors (NLWRs), which differ fundamentally from today’s light-water reactors (LWRs). But is different actually better? The answer is “no” for most designs considered in this assessment comparing NLWRs to LWRs with regard to safety and security, sustainability, and the risks of nuclear proliferation and nuclear terrorism. Based on the available evidence, the NLWR designs currently under development do not offer obvious improvements over LWRs significant enough to justify their many risks. 

Nonetheless, billions of dollars in both public and private investment have been committed over the last several years for development and demonstration of a number of NLWR designs by the end of this decade, including the TerraPower "Natrium" sodium-cooled fast reactor, to be built in Wyoming by a company founded by Bill Gates, and the X-Energy pebble-bed gas-cooled reactor, likely to be built in the state of Washington. These reactor designs have significant unresolved safety issues, and they both require uranium fuel enriched to higher levels than LWRs, raising proliferation concerns.These projects are also likely to experience high levels of technical and programmatic risk. Future appropriations for NLWR technology research, development, and deployment should be guided by more realistic assessments of the likely societal benefits and prospects for success than those that policymakers and investors have conducted to date.