This week, delegates met at a meeting organised by the European Nuclear Society and the International Atomic Energy Agency to discuss the type of fuel used in research reactors and how to manage the ageing facilities.
There are approximately 250 operating civilian research reactors, and around 75 use highly enriched uranium (HEU) for fuel. The use of HEU has the potential of nuclear proliferation as it could also be used for producing nuclear weapons. The solution is to convert HEU reactors to low enriched uranium (LEU), and programmes to do this are being carried out by the IAEA, as well the National Nuclear Security Administration in the USA (see reactor conversion feature from NEI's January issue).
Head of the IAEA’s research reactor group, Pablo Adelfang says that by 2020, almost all civilian HEU reactors will be converted to LEU reactors. But this will be a challenging process.
"When converting HEU reactors to LEU, we need to increase the density of the fuel. It needs to be around 4 to 5 times more dense than the equivalent HEU fuel," explains Adelfang. "This presents a challenge, and it will be a major focus of the meeting.
"The bottom-line is that with HEU minimization as the driving force, we need to develop technical tools to develop and qualify high-density LEU fuel which will replace HEU fuel with negligible or no impact on reactor performance," says Adelfang.
Another topic discussed during the meeting was the management of the ageing research reactor fleet. Around 65% of operating research reactors are at least over 30 years old. While training and research activities get adversely affected due to extended shutdowns of the ageing research reactors, the impact on medical practices that require isotopes is more serious.
“Ninety-five percent of the most utilized medical isotope worldwide are produced by 5 research reactors - all of them over 40 years old," states Ed Bradley, nuclear engineer in the IAEA’s research reactor group.
"Since the last quarter of 2007, we have seen extended shutdowns among these reactors, severely curtailing the supply of medical isotopes," he adds.
A notable and ongoing shutdown has affected Canada’s NRU reactor, which has been shuttered since May 2009 when a heavy water leak was detected. Operator Atomic Energy of Canada Ltd is currently working to repair the reactor pressure vessel. In its latest statement on 25 March, it said that the repairs are 56% complete and that isotope production is expected by the end of July.
"At the meeting we discuss how to address the refurbishment and modernization of the reactors and technologies related to ageing management, and planning," says Bradley. The IAEA has set up an Ageing Reactor Database to help address the problem of ageing, he says.