THORP

In its recently published paper ‘Oxide Fuels – Credible Options’, November 2011, the United Kingdom's Nuclear Decommissioning Authority (NDA) sets out options for the future operation of Sellafield’s Thermal Oxide Reprocessing Plant THORP. Opened in 1994 to reprocess UK’s domestic Advanced Gas Cooled (AGR) fuel and Light Water Reactor (LWR) fuel from overseas customers, the plant is currently operating years behind schedule. An estimated 400 tons of overseas spent fuel that should have been completed around 2004, plus some 2000 tons of UK AGR fuel remains to be reprocessed.

In addition, a further 4000+ tons of spent AGR fuel (including the currently expected lifetime arisings from the UK’s fleet of AGR power stations) are destined either for long-term storage at Sellafield prior to disposal or for reprocessing – at the NDA’s discretion. Should 5-year extensions be granted to the AGR power stations, a further 900 tons of spent fuel would arise.

A November 24, CORE Briefing provides a summary of the NDA’s assessment of three Options for THORP: - 1- Complete THORP’s reprocessing contracts; 2- Close THORP early by reprocessing less than the contracted amount of spent fuel and 3- Extend THORP operations so that more than the contracted amount of spent fuel can be reprocessed.

From its assessment, the NDA has concluded that, in line with its 2011 Strategy, Option 1 is the most viable and cost-effective - with the proviso that ‘additional new and costly infrastructure can be avoided (this would include the installation of new High Level Waste tanks), and that NDA proposals for the interim storage of AGR fuel are themselves viable. After further work to underpin the strategy, and providing the provisos are met, the NDA expects to confirm Option 1 as its preferred strategic option by summer 2012.

NDA currently rejects Option 3 – extending THORP operations to include more AGR fuel being reprocessed than currently contracted, and potential new business from domestic and overseas customers ‘if there were any’ – because:

• extended reprocessing would require multi-billion pound investment across a wide range of infrastructure at Sellafield, with major capital build projects required to support THORP’s extension beyond 2020. Such investment would divert finite resources from the NDA’s primary role of risk and hazard reduction at Sellafield, and new capital build projects would result in energy use and carbon emissions.
• extended reprocessing could potentially impact on the UK’s discharge commitments under the OSPAR treaty and could challenge the alpha and tritium target levels under the UK’s own Strategy for Radioactive Discharges.
• no interest has been expressed by the potential operators of new-build reactors in the UK to have their spent fuel reprocessed and recycled. Even had they done so, bulk quantities of spent fuel would be unlikely to be ready for reprocessing until the mid-2030’s when THORP and associated facilities would be over 40 years old.

The NDA’s current rejection of closing THORP early under Option 2 is based on:

• the provision of additional storage capacity for AGR fuel at Sellafield to ensure that incoming fuel from the power stations – at around 180 tons/yr - can be managed
• the possible need to implement alternative arrangements for overseas fuel.
• the requirement to manage spent fuels that are more susceptible to corrosion during storage
• the resultant earlier reduction to the workforce – though this could be mitigated by redeploying workers to the high hazard reduction activities elsewhere on site.

However, the NDA nevertheless believes that the early closure option should continue to be examined because of concerns that should a number of performance risks associated with THORP and its support facilities arise, Option 1 might have to be abandoned before 2018.

These risks include the overall age and condition of the reprocessing infrastructure, further failures of Sellafield’s current suite of Evaporators which process the high level wastes produced by reprocessing – or a delay in bringing on-line of a new Evaporator in 2014/15 – and the viability of the plans to store AGR fuel. The success of these storage plans depends on the current program to remove redundant multi-element bottles (MEB’s used to transport overseas fuel that has now been reprocessed)) from the ponds being completed on schedule, and the ponds suitably dosed with a corrosion inhibitor.

Based on THORP’s 2018 closure, an application to the Local Authority for a change of use of the ponds from buffer storage prior to reprocessing to interim storage pending disposal is expected to be made around 2016. Subject also to Regulatory approval, the NDA believes a technical and safety case for both storage and disposal of AGR fuel can be made.

In promoting what is likely to be its preferred Option 1, the NDA says that by completing THORP’s contracts in 2018, it will have honored obligations to overseas customers (and inter-Governmental treaties); provide time to prepare facilities for the interim storage of AGR fuel and create space to receive and manage all fuel arisings from AGR stations. It would also enable fuels susceptible to corrosion to be reprocessed.

The NDA believes the costs of the next 7 years of reprocessing - taking THORP to a 2018 closure - are comparable to those of the storage and direct disposal of spent fuel – largely because the capital costs for the reprocessing infrastructure are already sunk. If this had not been the case ‘it would be more cost-effective to cease reprocessing early’.

As part of its Oxide Fuels Credible Options paper, the NDA was asked by Government to consider the wider impacts of its THORP closure decision on the potential for future reprocessing in the UK. Reviewing topics that included Fast Breeder Reactor prospects, the future use of plutonium and new-build reactor operations, the NDA concluded that the timing of THORP’s closure had little material impact on any potential future requirement to supply plutonium; that THORP’s closure would neither impact on the UK’s new-build program nor on the long-term potential for reprocessing in the UK. Should the latter be required, a new reprocessing plant would be necessary.

It also concluded that, on a like for like basis, spent fuel storage followed by disposal ‘is currently more cost-effective than reprocessing’. This was based on an anticipated rise in costs of reprocessing and MOX fuel production in the UK, and the currently low price of uranium. Not surprisingly, all cost data was omitted from the NDA’s paper on the grounds of commercial confidentiality.

Plutonium re-use - putting the cart before the white elephant. Unwilling or incapable of learning from the UK’s disastrous MOX fuel experiences, the December 1 Government approval for the re-use of plutonium as MOX fuel is branded by CORE as a ‘decision made in the dark that yet again puts the proverbial cart before the inevitable nuclear white elephant’. With a preliminary decision taken by Government even before its Department of Energy and Climate Change (DECC) public consultation on plutonium management had started, it nevertheless promised that final approval for the re-use option was conditional on a range of major issues – including costs and demand for MOX fuel - being tested ‘before the UK Government will be in any position to take a final view'. (emphasis added)

The weakness of its case for the re-use of plutonium as MOX fuel has undoubtedly prevented the Government from going ‘the whole hog’ and putting its weight behind the construction of a new MOX plant at Sellafield or elsewhere in the UK. In its document published December 1 ‘Management of the UK’s plutonium stocks - A consultation response on the long-term management of UK-owned separated civil plutonium’  the Government however suggests that the construction of a new MOX plant could begin around 2019 with the first MOX fuel being fabricated in 2025.

On August 3, NDA decided to close the Sellafield MOX Plant SMP, a total failure which has so far cost the taxpayer BP1.4 bn (US$2.18 bn or 1.67 bn euro). (see Nuclear Monitor 732, 8 September 2011)
CORE Press Release, 2 December 2011

Source: CORE Briefing 3/11, 24 November 2011
Contact: Martin Forwood at  CORE (Cumbrians Opposed to a Radioactive Environment). Dry Hall, Broughton Mills, Broughton-in-Furness, Cumbria LA20 6AZ, UK.
Tel: +44 1229 716523
Mail: martin[at]core.furness.co.uk
Web: www.corecumbria.co.uk

Sellafield Ltd, the company that operates THORP (Thermal Oxide Reprocessing Plant) under contract to the Nuclear Decommissioning Authority (NDA), is facing yet another extended shut-down of THORP – this time for an estimated 7 months – when the only High Level Waste Evaporator configured to deal with THORP’s high level waste is taken off line for a major investigation.

The closure comes as little surprise given that Company reports and presentations over the last year have clearly anticipated the need to take action on the plant’s operational future because of increasing problems in managing the dangerous high level waste (HLW) produced not only by THORP, but also by the Magnox reprocessing plant (B205) and the effluents from the site’s Vitrification plant (WVP). 

At the heart of the problem are the site’s three HLW Evaporators A, B & C, which condense the liquid HLW from the site’s reprocessing plant and the effluents arising from the subsequent vitrification of HLW. THORP, by design, is configured for use with Evaporator C only, whilst A and B have historically been used to process WVP and Magnox wastes respectively - both the latter given priority over THORP wastes by the Nuclear Installations Inspectorate (NII) for ‘hazard reduction purposes’.  As a consequence, if either A or B break down and have to be taken out of service (as has happened in recent years), THORP’s Evaporator C is pressed into service to process Magnox or WVP wastes, leaving THORP effectively with no ‘evaporative capacity’ and therefore unable to reprocess.

THORP’s future operations at anything like a full commercial rate are therefore dependent on the regular and reliable operation of A & B. Their unreliability in recent years however has resulted in Sellafield Ltd having to place orders for 2 new Evaporators (D & E). Of similar design to C, the first of the new Evaporators is not expected to come into operation before 2014, the project currently being only at the stage of site foundation work. The original cost of BP 90 million is understood to have escalated to some BP 400 million (US$654 million, 470 million Euro)

In May 2008, in rationing the use of Evaporator C between the various facilities, the NII approved its further use for THORP - but only up to a maximum of 300 tons of oxide fuel derived HLW. Whilst this placed a limit on THORP reprocessing, it ensured that should the operation of A or B remain problematic, the prioritised Magnox and WVP wastes could at least be diverted for processing in Evaporator C if needs be.

Against this background of uncertainty over the reliability of Evaporators, Sellafield Ltd’s recent reports and presentations have assessed a number of possible options for THORP’s future - one being a moratorium on reprocessing at the plant and another being to operate THORP for part of the year only – with its workforce redeployed to other work on site. The prospect of such options becoming a reality came a step closer on the May 18 this year when Sellafield Ltd announced that Evaporator B had been shut down following the discovery of a rise in radioactivity levels in one of its internal heating/cooling coils.

Though the closure of B for inspection was relatively short lived, Sellafield Ltd was forced to refute opposition claims that THORP faced imminent closure, and to assure its workforce that, despite the problem with Evaporator B, there ‘was no danger of any plant closures’. 

In early June the claim of no plant closures was however thrown into disarray when confirmation was given to CORE, at a meeting with the NDA, Sellafield Ltd and Sellafield’s new parent body organisation Nuclear Management Partners (NMP), that Evaporator C was shortly to be taken out of service for a thorough investigation.  As Evaporator C is the only Evaporator configured to process THORP HLW, THORP would have to close down for 7 months - the projected duration of the Evaporator investigation. This would include not only the physical investigation itself (thickness measurement of internal cooling coils), but also the subsequent evaluation of the data from the investigation, the making of a new Safety Case for the Evaporator, and gaining approval from the Nuclear Installations Inspectorate (NII) for future use of the Evaporator for THORP reprocessing.

The prospect of a further 7-month closure of THORP, following the large number of unplanned ‘outages’ that have blighted the plant’s operational life, will do little to calm the increasing concerns of its reprocessing customers. Already known to be highly critical of Sellafield’s inability to operate THORP properly, overseas customers must now reconcile themselves to having to wait even longer for their contracts to be completed – perhaps 13 or more years late.

When THORP opened in 1994, its contracted customers had been assured by the then owners British Nuclear Fuels plc (BNFL) that, as Sellafield’s ‘flagship’ plant, THORP would reprocess 7000 tons of spent fuel in its first ten years of operation (the base load contracts). At the end of that 10-year base load period, THORP had struggled to complete 5000 tons of that order book.

Originally scheduled to close ‘with all contracts completed’ around 2010/11, the closure date had to be put back to around 2016 when, with a total 5729 tonnes reprocessed, THORP was closed down in April 2005 following the major accident (INES Level 3) when 83,000 litres of dissolved spent fuel leaked undetected from a fractured pipe in THORP’s Feed Clarification Cell. Re-opened in 2007, and still with contracts for 800 tons of overseas fuel and 2000-3000 tons of UK AGR fuel to complete, THORP has reprocessed a further 300 tons to date, including 50 tons of overseas fuel (Dutch and Swiss), bringing the overall total reprocessed since 1994 to 6000 tons.

The throughput target for the current financial year 2009/10 – the plant’s 16^th year of operation - is just 200 tons, 17% of its original design throughput of 1200 tons per year, and a rate previously described to CORE by BNFL as being commercially uneconomic for THORP. As a result of the imminent 7-month closure for Evaporator C investigation, THORP is now projected to close (with all contracts completed) in 2017, though any combination of further Evaporator failures, delays to new Evaporators or any other unexpected technical failures within THORP itself, could see reprocessing operations continuing to 2020 or beyond.

The NII’s current 300-ton limit for THORP’s use of Evaporator C is expected to be reached at some point in July this year. Once reached, and with the Evaporator taken out of service and THORP closed, the burden of processing Sellafield’s Magnox and WVP wastes will fall entirely on Evaporator B which only came back on line in July 2008 after a 43-month outage for repair. Evaporator A will be kept on stand-by.

Built some fifty years ago, A & B are fitted with a cooling/heating jacket around the base and sides of the evaporator and four internal coils, which can be used alternately for heating and cooling the HLW under process. By comparison, Evaporator C was commissioned in 1990 and has 6 internal coils. Corrosion and vibration pose the greatest threat to the integrity and lifetime of these evaporators, particularly the coils and stainless steel base of the evaporators which are subject to high temperatures and hot-spots within the bottom layer of the waste sludge’s.

Failure of the coils through corrosion has resulted in A & B being forced out of service on numerous occasions in the last few years and both now have to be operated with less than their full complement of heating/cooling coils. Heating and cooling provision for Evaporator B, for example, is restricted to its jacket and just two (of the original four) heating/cooling coils. In its Quarterly report on Sellafield (July to September 2008) the NII considered the operational life of B could be quite considerable ‘provided that waterside corrosion does not cause premature failure of the remaining two heating/cooling coils’.

For its part,  Evaporator A, with its jacket and just one serviceable coil, is kept on stand-by ‘as a contingency’ to deal with the wastes from WVP which have a lesser heat loading than those from reprocessing and are therefore less demanding on the Evaporators.

It is ironic that as the worldwide economic downturn forces household-name businesses into liquidation across the UK, reprocessing at THORP - arguably the UK’s largest white-elephant of all – should continue to get the backing of the UK Government and the plant’s owners the NDA despite its woeful performance and its increasingly poor commercial prospects. It apparently owes its survival, not on any merit as a spent fuel management option, but solely because of the revenues it continues to bring in from the now disgruntled overseas customers who signed up with THORP decades ago. The NDA, funded by the taxpayer, uses the revenues to offset some of its spiralling clean-up and decommissioning costs at Sellafield and other UK sites.

Whilst Sellafield Ltd will be keeping its fingers crossed that the site’s Evaporator problems can be overcome, it will also be working hard to understand and improve the weakness in associated facilities that similarly threaten THORP’s future. One such is the continuing underperformance of WVP whose ability to deal with the HLW from reprocessing is essential in reducing the overall stocks of HLW at Sellafield (currently just under 1000 cubic meters) as required by the NII’s 2001 Specification, to a buffer stock of 200 cubic meters by 2015. Then there is the condition of the storage tanks in which the HLW is stored prior to vitrification. Having been subject of particular NII concern over recent years because of corrosion problems, plans are now being drawn up to build new tanks, though their installation and operation is not envisaged for at least ten years.  

Whilst THORP is owned by the NDA, its operators Sellafield Ltd now come under the management of Sellafield’s new Parent Body Organisation (PBO) appointed late last year by the NDA. The PBO – Nuclear Management Partners Ltd (NMP) is a consortium of the US Washington International Holdings Ltd., AMEC and AREVA. NMP will hold shares in Sellafield for the next 17 years under a contract estimated at some BP 22 billion (US$ 36 billion, 26 billion Euro). As relative newcomers to Sellafield, NMP’s view on the future of THORP and reprocessing remains unknown.

Source and contact: Cumbrians Opposed to a Radioactive Environment (CORE). Dry Hall, Broughton Mills, Broughton-In-Furness, Cumbria, LA20 6AZ England.

Tel/Fax: +44 1229 716523
Email: info@corefurness.co.uk
Web: www.corecumbria.co.uk

(December 15, 2006) At Carlisle Crown Court, British Nuclear Group (BNG) was fined £500,000 (currently about 575.000 Euro) for the accident in April last year at Sellafield's THORP. The accident was classified at Level 3 on the International Nuclear Event Scale, the worst recorded accident at Sellafield for many years.

(650.5775) Laka Foundation - BNG, who operate Thermal Oxide Reprocessing Plant (THORP) under contract to site owners the Nuclear Decommissioning Authority (NDA), had pleaded guilty in an initial hearing at Whitehaven Magistrates Court earlier this year to three charges brought by the Health & Safety Executive (HSE). The charges, under the Nuclear Installations Act 1965, related to breaches of Sellafield site licence conditions, and were summarized by HSE as (i) failing to make and comply with written instructions, (ii) failing to ensure that safety systems are in good working order and (iii) failing to ensure that radioactive material is contained and, if leaks occur, that they are detected and reported.

In fining BNG, Judge Openshaw told the Court that as BNG had pleaded guilty to the offences, he was reducing what he considered to be an appropriate level of fine of £750,000 to £500,000. In reminding the Court of the 'cumulative failures' and the 'worker culture of tolerating alarms' that had lead to the accident, he added that BNG's failure to detect the leak 'probably within days' rather than 8 months was a serious failure worthy of condemnation.

The accident, reported to the HSE's Nuclear Installations Inspectorate (NII) on April 20, 2005, entailed the undetected spillage of 83,000 litres of highly radioactive dissolved nuclear fuel and nitric acid over an estimated 8 month period from fractured pipework in the plant's Feed Clarification Cell. The plant was closed immediately and has remained shut down since then. During the closure, which has seen 18 months of reprocessing business put on hold, 2 improvement notices and 49 recommendations have been served on BNG by the NII along with a further 18 recommendations imposed by BNG following its own Board of Investigation into the accident..

At the time of the accident, (THORP's 11th year), the plant was running almost 3 years behind schedule, with just 5729 tonnes of spent fuel reprocessed from a total of 7000 tonnes originally scheduled for completion in the first 10 years of operation (the baseload). The outstanding fuel includes over 700 tonnes of foreign fuel, with the remainder being UK fuel from British Energy's (BE) Advanced Gas Cooled reactor stations. If and when these 'baseload' contracts are completed, a further volume of fuel (post-baseload), largely from BE, is also contracted for reprocessing at THORP.

Restart of the plant, already re-scheduled a number of times, is now set for early 2007, providing all required recommendations have been 'closed out' to the satisfaction of the NII and with the agreement of the NDA. THORP's future however currently remains under close review by the NDA and by the Government who will make the final decision as to whether further reprocessing at the plant can be justified.

The costs of the accident, not yet fully quantified, have been put variously between £50M and hundreds of £M. Modifications (rather than repairs) to THORP's damaged Cell, now completed, will allow an eventual re-start of the plant by by-passing the damaged equipment and pipework. As a result of the modified system, THORP's future throughput rate is expected to be limited to well below the plant's design specification.
Martin Forwood added: "We have major concerns about the restart of THORP given that the systems and pipework that will be used share exactly the same history as that which failed so comprehensively during the accident from metal fatigue and other stresses. As the plant can never again operate as originally designed, there are no good grounds for resuscitating this White Elelephant. We will continue to call for its immediate closure".

More Sellafield News:
Reprocessing at the Sellafield complex has been halted completely early December as a safety precaution following discovery that radioactivity has been leaking into an evaporator's cooling water. This means Magnox reprocessing will not be able to restart until the Nuclear Installations Inspectorate gives the all-clear, which is not expected before January.
Meanwhile, British Nuclear Group has signed a new MOX fuel supply contract with German utility EnBW kernkraft, for the supply and transport of MOX fuel to the Neckarwestheim 2 reactor. It also requires EnBW to commit to convert all the plutonium arising from their reprocessing contract at Sellafield into MOX. But this presumably means BNG has to get the Sellafield MOX-plant and THORP working properly.

Sources: CORE Press Release, 16 October 2006 / Whitehaven News, 8 December 2006 / Renew, the NATTA newsletter # 164, Nov/Dec 2006
Contact: CORE, 98 Church Street, Barrow In Furness, Cumbria LA14 2HT, U.K.
Tel: +44 (0)1229 833851; Fax: +44 (0)1229 812239
web: www.corecumbria.co.uk
Email: info@core.furness.co.uk