Areva, Candu Energy and GE Hitachi are competing to re-use the UK's plutonium stockpile. (Image credit: Ilyast)

The UK government is deciding whether to re-use or dispose of the world’s largest stockpile of used civil plutonium stocks, located at the Sellafield reprocessing and waste facility in Northwest England.

The stocks are currently estimated at around 130 metric tons and are expected to rise to 140 metric tons when reprocessing operations are completed.

The U.K.'s specific plutonium stockpile challenge has presented developers with specific opportunities to deploy third and fourth reactor technologies, overseen by a government which has firmly backed the widespread construction of new nuclear capacity.

The government would prefer to re-use the plutonium rather than dispose of it, and it has labelled Areva’s CONVERT plan as the “preferred option.”

AREVA’s CONVERT project involves the design, construction, operation and decommissioning of the firm's first UK-based Mixed Oxide (MOX) plant, to eliminate the plutonium stockpile and convert the vast majority of it into MOX fuel for use in the new generation of light water nuclear reactors in the UK.

However, two other innovative projects using solutions developed by GE Hitachi’s (GEH) and Canada’s Candu Energy have been labelled as “credible” alternatives by the UK’s Nuclear Decommissioning Authority, the government-owned body which overseas the U.K.'s decommissioning and nuclear legacy program.

GE Hitachi’s proposed PRISM-based facility would utilise fourth generation 311 MW pool-type, metal-fueled, small modular Sodium Fast Reactors, while Candu Energy has proposed using its 700 MW Generation III Enhanced CANDU 6 (EC6) reactors which are heavy-water moderated and heavy-water cooled.

The NDA published its initial view on the proposed technologies in a research paper in January 2014, and has been reviewing the project proposals in more detail since then.

The government is expected to reveal more detail on its plutonium processing plan by the end of 2015, David Powell, VP Nuclear Power plants sales, GE Hitachi, told Nuclear Energy Insider on the sidelines of the World Nuclear Association conference, on September 10.

The government is to provide more detail on the procedure used to process the stockpile, without specifically defining the preferred technology, Powell said.

Bill Hamilton, Head of Stakeholder Relations at the UK Nuclear Decommissioning Authority, said October 6 he expects a government statement “in the next few months,” which will outline the broader plan to manage the stockpile.

The plutonium stocks held at Sellafield represent a significant portion of global stocks, which are equivalent to three years' supply of natural uranium from the world's mines, according to the World Nuclear Association.

                       Global Inventory of separated recyclable materials

Source: WNA

MOX versus Metal

NDA has said the reprocessing of the plutonium held at Sellafield into a MOX fuel remains a credible and technically mature option for the majority of the stocks, given the planned new build reactor technologies.

“In the short term, a window of opportunity may exist to factor in use of MOX, whilst developers establish their business cases for new reactors, agree commercial terms and develop licensing approaches,” NDA said in its January 2014 research paper.

Areva's Melox plant in Gard, Southeast France has been producing more than 140 metric tons of MOX fuel per year, to power light-water reactors in several countries. It has produced over 1,500 metric tons in total.

French state-controlled Areva has worked closely with the UK government on its proposal to build the first MOX production plant in the UK, Caroline Drevon, Vice President Strategy, Sales & Innovation for Back-End at Areva, told Nuclear Energy Insider September 12.

Areva is a leading provider of nuclear fuel recycling solutions and has already reprocessed some 55,000 metric tons of uranium-rich nuclear fuel in the UK market, Drevon noted.

Candu Energy’s CANMOX solution would also involve building a mixed oxide (MOX) fuel plant, to reprocess the plutonium to fuel four 700 MW Generation III EC6 reactors, which are heavy-water moderated and heavy-water cooled.

The EC6 reactor has a 60-year design life and it has completed its formal regulatory design review against modern safety standards by the Canadian Nuclear Safety Commission (CNSC).

Candu Energy is confident the facility would meet the UK licensing requirements given the firm’s experience of licencing the CANDU design in Canada and Europe and the similarities in UK and Canadian regulatory approaches.

The EC6 Reactor is based on the CANDU 6 reactor model which has a proven deployment and operation record and the company argues its plutonium processing facility can be implemented earlier than the other reuse options.

“Based on their worldwide experience, the overall implementation timetable to first irradiation is claimed by Candu to be in the range of 10-12 years,” NDA said in January 2014.

GEH’s project differentiates itself by proposing to use metal rather than oxide fuel to supply a pair of 311 MW PRISM reactor modules, avoiding the need for MOX production. GEH’s PRISM plants have a 60 year design life, in line with Candu Energy’s EC6 reactors.

NDA has supported GEH’s view that PRISM could reuse the UK’s full inventory of plutonium and use it faster than the competing technologies, because of a higher incorporation of plutonium in the fuel base. GEH has said that its plant could make the plutonium proliferation resistant within 30 years.

According to GEH, the modular approach to construction of the PRISM plant allows the addition of generating capacity in stages, making construction arrangements more flexible and keeping supply growth in line with demand.

“Using its own experience and industry norms, GEH estimated that licensing these first of a kind facilities would take around six years, similar to the period it took to licence Sizewell B,” NDA said in in its research paper.

”The overall implementation timetable to first irradiation is claimed by GEH to be in the range of 14-18 years, with these estimates being supported by [Advanced Boiling Water Reactor] delivery results outside the UK,” it said.

NDA also said it believes the implementation timetables set out by both GEH and Candu Energy are ambitious “considering the delivery performance norms currently seen in the UK and European nuclear landscape.”

Nuclear island

The UK government was expected to make a decision on its preferred plutonium research option by the end of June 2015. Having failed to meet this deadline, the plans set out by the government in the coming months will be the focus of much attention in the nuclear sector, given the UK’s ambitious nuclear build program and stuttering progress of EDF’s 3.2 GW Hinkley Point C EPR project.

EDF’s proposed Hinkley Point C plant is the UK’s furthest advanced new build project and there is some 15.6 GW of new capacity planned or proposed, not including the plutonium processing projects, according to the World Nuclear Association.

Further direction from the government over the processing of plutonium at Sellafield will provide developers with a clearer idea of when commercial development can begin.

“In a few years time, DECC [the Department of Energy and Climate Change] will run procurement for this project,” GEH’s Powell noted. “I expect that in 2016, the next step will happen,” he said.

The chosen technology could have a wider impact on future new build in the UK, Powell added.

“It seems that where to go with plutonium determines the direction of UK new nuclear power in the future,” Powell said.

By Rumyana Vakarelska