A group of 35 Nobel laureates, including 16 physicists, has called on world leaders to reduce the use of highly enriched uranium (HEU) in naval nuclear propulsion and research reactors. In a letter addressed to national leaders at last week’s Nuclear Security Summit in Washington, the laureates call for “serious technical studies” to transition naval reactors to using low-enriched uranium (LEU). They also call for a road map for converting or shutting down research reactors that use HEU, as well as the development of non-radioactive alternatives – such as cobalt-60 and caesium-137 – for use in medicine and research.
More than 90 research reactors have been converted to LEU or closed down in the past 40 years. The US has also been reducing its stocks of HEU, which is defined as uranium with 20% to 90% concentration of the uranium-235 isotope. According to the US government, the country’s stocks of HEU fell from 740.7 tonnes to 585.6 tonnes between 1996 and 2013. The latter amount includes around 500 tonnes for national security, such as the production of nuclear weapons and naval propulsion, 44.6 tonnes of spent nuclear reactor fuel, as well as 41.6 tonnes that could be reduced to LEU or disposed of as low-level waste.
Regardless of these steps, the laureates urge “serious technical studies” to investigate moving to LEU fuels for naval nuclear propulsion as well as “strongly” recommending governments devote more resources to addressing the remaining HEU-fuelled reactors over the next decade. Burton Richter, who shared the 1976 Nobel Prize for Physics and instigated the letter together with the president of the Federation of American Scientists, Charles Ferguson, told physicsworld.com that almost all research reactors should be convertible to LEU. “Some might not be,” he adds. “But the world can live without them.”
Richter regards the non-military uses of HEU as the more serious risk of falling into the wrong hands. “I’m less worried about the naval-reactor HEU than the civilian HEU because military reactors have a lot more security,” he told physicsworld.com. “The amounts are much higher on the military side, but so is the security.” Indeed, in their letter, the 35 laureates warn that the threats of nuclear and radiological terrorism “cross national boundaries” and will require collaboration between nations to prevent an incident from happening. “We urge [national leaders] to devote the necessary resources to make further substantial progress in the coming years to real risk reduction in preventing nuclear and radiological terrorism,” they add.
The laureates also praise the progress made by governments and companies in developing ways of treating cancer and blood disorders by using other techniques that do not rely on highly radioactive sources.
About the author
Peter Gwynne is Physics World‘s North America correspondent