UK Plutonium and MOX Experience

Nuclear Monitor Issue: 
#763
13/06/2013
Martin Forwood
Article

Since the production of plutonium (via the Windscale Pile reactors) for use by the UK's nuclear weapons program of the 1950's, Sellafield's flirtation with the civil use of plutonium has seen little progress and led to technical failure and international embarrassment.

From its military origins, plans to permanently deal with the country's ever-growing plutonium stockpile – currently at 118 tonnes, the largest in the world − have remained largely in the background until 2010 when the UK Government launched a Public Consultation on a range of management options. These included its re-use as mixed oxide fuel (MOX), its sale to third parties or its classification as nuclear waste. Given successive Governments' record of unbridled support for the industry, it is unsurprising that the re-use of plutonium in MOX fuel was chosen as the preferred option. Clearly ignoring recent experiences – as the record shows − both Government and industry appear to have fallen into the trap of actually believing their own propaganda.

Sellafield first turned its hand in the 1960s to the 'civil' use of plutonium which was being recovered in increasing amounts through the site's B204 and B205 reprocessing plant – the latter dealing with the spent from the UK's first generation Magnox reactors. The first of these, the Calder Hall reactors, retaining a dual civil/military role until the 1990s.

This new civil era saw the production of 18 tonnes of plutonium fuel for the Prototype Fast Reactor at Dounreay in Scotland, and some 3 tonnes of light-water reactor MOX fuel. Despite this limited experience, but sensing the growing MOX market being tapped into by European fabricators, British Nuclear Fuels Ltd (BNFL) launched its plans for a MOX Demonstration Facility (MDF) that would 'demonstrate BNFL's ability to produce quality MOX fuel'.

With an 8 tonne per year capacity, MDF operated from 1993 to 1999, producing 44 MOX assemblies for pressurised water reactors (around 660 kgs plutonium) for Japanese and European customers. The facility was closed down in 1999 after the quality assurance data for the only fuel to be produced by MDF for Japan was found, on delivery to Takahama, to have been falsified by MDF workers. Returned to the UK in 2002, the falsified fuel has been pond-stored at Sellafield and is scheduled for transport in 2014/15 to France's La Hague for plutonium recovery.

Despite the scandal bringing the resignation of BNFL's Chief Executive and a compensation payment to Japan (whose utilities called a temporary ban on further dealings with BNFL), the embarrassing event made little impression on BNFL's determination to pursue the MOX fuel market. Plans to enter the market – based on 'the wealth of experience gained within BNFL' − had been laid in 1992 (pre MDF operations) with a planning application for the Sellafield MOX Plant (SMP) whose viability rested on winning major business from Japan.

Sellafield MOX Plant
Surviving legal challenges and 5 rounds of public consultation which focussed largely on the plant's increasingly dodgy economic case, the first plutonium was introduced into SMP in 2002. With small orders secured from German, Swiss and Swedish utilities, the expected business from Japan was conspicuous by its absence. The technical complexity of SMP, largely responsible for its eventual downfall, caused problems from the first days of operation.

Using a 'short binderless' powder mixing process unique to BNFL, the production line consisted of pellet production, rod filling and assembly of the rods into a MOX fuel assembly. Early failures in one section of the production line lead to bottlenecks in other sections and after 3 years of operation only one MOX fuel assembly had been produced. With its design production capacity cut from 120 tonnes per year to 72 – and then 40 tonnes − SMP was forced to sub-contract some orders to rival fabricators in Belgium and France.

Against this background, and taking ownership of Sellafield and SMP in 2005, the Nuclear Decommissioning Authority (NDA) almost immediately commissioned independent reports on SMP from consultants Arthur D Little, whose 2006 report exposed the extent of SMP's problems and concluded that 'looked at pessimistically, improvement plans will fail to live up to expectations leading eventually to an irrevocable collapse in the business case and closure'.

By 2009, with an overall total of just nine assemblies produced in seven years of operation, it was clear that a major engineering rescue package was needed, with an NDA technical assessment concluding that SMP could provide neither the capacity nor longevity to be used for the UK civil stockpile.

In a surprise announcement in 2010, Japanese utilities agreed to pay an undisclosed sum for the refurbishment with a promise of trial orders with a revamped SMP. Fate intervened however in the form of the Fukushima meltdowns which resulted in the interest in SMP by Japanese utilities being abandoned.

In August 2011, the NDA announced the closure of SMP – the blame being laid conveniently on Japanese problems. In reality, the over-complex plant which cost the UK taxpayer £1.34 billion and had produced just 13 tonnes of MOX fuel (32 fuel assemblies incorporating around 800 kgs of plutonium) in its 9-year life, was clearly beyond salvation − with or without Japanese help.

SMP's closure rekindled official interest in managing the plutonium stockpile. The Government's public consultation, already launched in 2010, had assessed a number of management options. Ruling out fast-breeder reactors and immobilisation of plutonium as a waste as options that were either technically immature, impractical or too costly, the Government concluded that the re-use of plutonium in MOX fuel remained its preferred option.

Growing plutonium stockpile
The latest official figures show Sellafield's stockpile amounting to 118 tonnes of separated plutonium which includes 24 tonnes of overseas-owned plutonium. Whilst a majority of the 94 tonnes of UK-owned material has arisen from Magnox reprocessing, the overseas-owned plutonium has been recovered largely in the Thermal Oxide Reprocessing Plant (THORP) and, under the terms of the original reprocessing contracts, is destined for return to customers in the form of MOX fuel.

However, in a recent Government U-turn on those contractual requirements, title transfers ('paper swaps') of some overseas plutonium has already seen 7 tonnes taken into UK ownership − 3 tonnes of plutonium of German and Dutch origin being transferred in April 2013 (the German material as repayment to France's manufacture of orders sub-contracted by SMP) and a title transfer of 4 tonnes of German plutonium made in 2012 (to allow MOX fuel for Germany to be produced in France in advance of the German nuclear phase-out).

As it stands, owners of the 24 tonnes of foreign plutonium are Japan (16 tonnes), Germany (3 tonnes), and the balance of around 5 tonnes owned between Switzerland, Italy, Spain and Sweden. Given officialdom's tacit acceptance that exporting weapons-useable plutonium − in dioxide powder form – from Sellafield is no longer an accepted option, more title transfers are likely as overseas customers increasingly seek to rid themselves of plutonium ownership. Indeed, the fate of the Japanese plutonium has already been under discussion between NDA and Japan.

For the stock of UK-owned plutonium, which will continue to rise until the 2020 scheduled end of reprocessing, its conversion to MOX as preferred by Government/NDA would require a new MOX plant to be built. Estimated at £6 billion, it remains unclear who would take on such a financially risky project, especially in the absence of any viable market for the fuel and the recent SMP debacle.

Seemingly impervious to these obstacles, the UK Government sees MOX fuel being used either in the UK's fleet of new-build reactors or in Candu 6 reactors overseas. Whilst the latter is an option belatedly suggested by Candu Energy − and still under consideration by the NDA − the former looks increasingly suspect with the UK new-build 'renaissance' in increasing disarray. Further, both reactor types scrutinised so far under the regulatory Generic Design Assessment (GDA) licensing process – the EPR and Westinghouse AP1000 − were assessed on their use of conventional uranium fuel only, with MOX use specifically excluded. A late addition, Hitachi-GE's ABWR reactor, began its expected four-year GDA process only in April this year.

Raising further doubts on the Government's preferred re-use option, the NDA revealed in June 2012 that it had opened talks not only with Candu Energy but also with GE-Hitachi who had submitted a feasibility proposal for the use of its liquid metal-cooled 'Power Reactive Innovative Small Module' (PRISM) fast-breeder reactor (a.k.a. 'integral fast reactor') as an alternative to MOX.

The PRISM proposal, which involves a 60-year program at Sellafield that would see the UK-owned stockpile of plutonium converted to the spent fuel standard of self-protection and proliferation resistance within the first 5 years, is still being assessed by the NDA with a decision expected this summer.

PRISM sceptics rightly point to the earlier rejection of fast-breeders by Government, and the complexity of an immature technology that is still at design stage and would require not only the construction/operation of PRISM itself but also a conversion plant to convert plutonium dioxide to a metal fuel and a pyroprocessing system to process the spent fuel from PRISM for re-use in the fast reactor.

So the jury is still out. Should the decision to approve the PRISM proposal be taken later this year, it would almost certainly mean the end of any future MOX plans at Sellafield. Meanwhile, the UK-owned stockpile of plutonium will remain in storage at a cost of £80 million per year.

 

'Pizza Cumbriana'
Eight years after it was produced from material gathered from the West Cumbrian coast near Waberthwaite, a radioactive 'Pizza Cumbriana' was delivered to the Low Level Waste (LLW) facility at Drigg on April 29 for disposal as LLW.

Originally presented by Cumbrians Opposed to a Radioactive Environment in March 2005 to the Italian Embassy in London as evidence of the environmental contamination caused by the reprocessing of Italian and other foreign spent fuel at Sellafield, the condemned pizza has languished with other LLW at the Atomic Energy Research Establishment at Harwell until 22 February 2013 when it was transported by road to its rightful resting place at Drigg.

In advance of its presentation to the Italian Embassy in 2005, analysis of the pizza by Manchester University's Department of Chemistry revealed levels of radioactivity in the pizza topping − comprised of estuary sediment, sea samphire, seaweed and shells − that classified the material as LLW. The levels of radioactivity included 25,000 Bq/kg of Caesium 137, 25,000 Bq/kg of Americium 241 and levels of plutonium up to 15,000 Bq/kg.

Placed in a traditional takeaway pizza box, it was marked with the nuclear waste danger sign and listed its 'traditional Italian ingredients' as 'Caesium, Americium and Plutonium'. The pizza is still 24,392 years within its sell-by date. (www.corecumbria.co.uk, 29 April 2013)