Part 3 of 3 Parts (Please read Parts 1 and 2 first)
As an alternative, the U.K. plutonium might be used in reactors that are better suited to deal with the plutonium stockpile according to their vendors. One choice would be a CANDU-EC6 heavy water reactor. Another choice would be the small, fast sodium cooled reactor concept called the PRISM. The use of recycled MOX in CANDU reactors appears to be feasible. On the other hand, the use of recycled MOX in a light water reactor would bring no addition benefits and would be more difficult to implement. In March of 2019, the NDA officially removed the PRISM reactor from the list of viable options for MOX fuel. As early as 2011, the NDA had stated in internal memos that the “technology maturity for the PRISM fuel, reactor, and recycling plant are considered to be low.” However, the NDA has said that it would continue to monitor progress in fast reactor programs.
Setting aside any questions about the viability of MOX fuel production, costs, and everything else related to actual of operation of the PRISM reactor, an analysis was conducted of the claim by Hitachi that PRISM could “could conceivably make the entire UK plutonium stockpile proliferation-resistant in 20 years” through irradiation. The analysis indicated that the Hitachi claims were highly optimistic.
Using plutonium as a reactor fuel has two major results. Some uranium is burned and the remaining is left mixed with highly radioactive spent fuel. That radioactivity creates a barrier for any malicious actors who might steal and separate the plutonium from that fuel. This results in proliferation resistance. However, because of radioactive decay in the spent nuclear fuel, the height of the proliferation barriers steadily decreases. The analysis mentioned here was only applied specifically to the PRISM reactor, the analysts assume that there would be similar effect for other irradiation options. During the time that would be required to reprocess the entire huge U.K. stockpile of plutonium, the material that had already been treated would be slowly decaying and losing much of its proliferation resistance.
Why should the public sector continue to pay money for “new” reactor concepts when it is not clear whether or not any of these new reactors could solve the problem under consideration. Some of these “new” reactor concepts have been under development for decades. The U.K. needs a practical and economical solution to the disposal of plutonium as soon as possible. The British government, the NDA and reactor operators in general should finally accept that plutonium is a burden and not a resource. A closer look should be taken at immobilization. These do not have the attraction of new, high tech solutions such as special reactors to burn the plutonium. The fact that urgent action needs to be taken suggest that established and working concept should be seen as the way forward to a solution. Other countries including the U.S., Japan and South Korea have also flirted with plutonium recycling for nuclear fuel without any significant progress in decades.