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22 | 13th - 19th March 2015 | UtILItY WEEK Game changer Prism aims to dethrone Mox GE Hatachi claims its Prism reactor is a technically superior way of getting rid of the UK's stockpile of plutonium – and it generates electricity into the bargain. All it needs is a first adopter to prove it. P roponents of nuclear power have never been able to say much to allay the fears of the anti-nuclear lobby when it comes to radioactive waste. But now a technology – long in development – might be deployed that could salve those fears. It would also contribute to UK electricity gen- eration for at least 60 years. Prism (Power Reactor Inherently Safe) is a fourth-generation nuclear reactor from GE Hitachi, a joint venture based in North Caro- lina, US. The reactor works on an integral fast reactor principle and uses metal rather than oxide fuel – distinguishing it from the vast majority of nuclear reactors around the world both "fast" and "slow". Crucially, the metal fuel is made using plutonium – of which the UK has the largest civil stockpile in the world. It currently totals about 100 tons and is forecast to increase to about 140 tons over the next few years. The British government has made a binding com- mitment to ensure the plutonium is "disposi- tioned" so that it cannot be used in weapons. Apart from the obvious desirability of doing this, it is also very expensive to secure Sella- field to stop any ill effects of plutonium get- ting out and anyone with terrorist motives getting in. Prism would use plutonium from the UK's stockpile (in the form of plutonium Operations & Assets oxide powder) to make an alloy with uranium and zirconium. This would then be cast into chunks and stacked in stain- less steel containers to form fuel pins. Waste from the Prism process is many orders of magnitude less radioactive than conventional waste from nuclear power generation – and useless for mak- ing nuclear weapons. Prism's waste – consisting of "fission products" such as caesium and krypton – would take about 300 years to reach back- ground radiation levels, a big improvement on the 300,000 years needed for conven- tional nuclear waste. Depending on whether the fission wastes of Prism naturally occur as minerals or metals, they would be turned into either ceramic or metal matrices and stored in geological disposal facilities. Emphasising the "robust" safety of this stor- age technique, Eric Loewen, chief consulting engineer for GE Hitachi and a world authori- ties on nuclear power, playfully tells Util- ity Week "even if some of this stuff got into the hot water for making your tea, it would not leach out its elements". It sounds as though Prism is a no-brainer. So why hasn't the UK government, or oth- ers around the world, committed to building reactor modules? Primarily, according to Jay Wileman, GE Hitachi's chief operating officer, it's because the development of Prism was stalled in the 1980s because of "budgetary refocusing" in the US. With Prism on the back boiler, another form of plutonium disposition came to the fore – Mox, the process of making mixed oxide fuel from civil plutonium. Mox is now relatively well-established, accounting for about 5 per cent of the nuclear fuel used in the world today. And because we are talking about nuclear, it is hard to depose a technology once it has become established – especially, as is the case with Prism, if your technology has never yet been trialed as an integrated unit and at scale. Governments are understandably nervous about being the first to trial new nuclear technologies. However, Wileman and Loewen are both optimistic about the prospects for Prism in the UK. In 2012, GE Hitachi successfully introduced the idea of Prism as an alterna- tive technology for disposition to the Nuclear Decommissioning Authority (NDA). In early 2014, the NDA declared Prism a "viable" • Prism is vying with two other technolo- gies, Candu and Mox, for the Nuclear Decommissioning Agency's favour as the right choice for dispositioning the UK's plutonium stockpile. (The UK has committed to ensuring that it's large plutonium stockpile is dispositioned for non-proliferation). • The only suggested location for Prism in the UK is Sellafield, since the pluto- nium stored there cannot be trans- ported without insupportable risk and public concern. • Prism is an integral fast reactor that converts plutonium into a waste prod- uct that has a much shorter half-life than conventional nuclear waste. • Electricity is a by-product of this dispo- sition process. • A single prism reactor has an electric- ity generation capacity of 300MW. The proposition for Sellafield is to deploy two reactors powering one turbine giv- ing an overall capacity of 600MW. • Prism can also use spent nuclear fuel as a fuel source. 6 things you should know