The Nuclear Decommissioning Authority’s (NDA’s) strategic review has confirmed what has been expected for a while. The Thermal Oxide Reprocessing Plant (THORP) in Cumbria, England, will complete it reprocessing contracts (both UK and overseas) and then close. However, signs that the NDA has little confidence in predicting the closure of the magnox reprocessing plant are evident in documents published in July.
THORP's reprocessing contracts should be completed by 2018, at which time THORP would cease reprocessing activities and enter a post-closure and clean out phase prior to decommissioning. Any remaining spent AGR fuel from UK reactors, including any future arisings, will be placed into interim storage pending a decision to dispose of it in a geological disposal facility.
There are, however, a number of ‘performance risks’ that could impact on the delivery of the strategy. In other words, THORP might break down, which would be no great surprise given past experience. The NDA had previously expected to complete reprocessing contracts at THORP in 2010, but operational difficulties both in THORP and in downstream support plant, had delayed the completion of that work. Operational difficulties could result in the reprocessing of less than the currently planned amount of spent fuel by late 2018. The NDA says: “We believe, therefore, we should con-tinue to examine alternative options so that we can manage these risks to the delivery of our strategy.”
The NDA says keeping THORP open significantly beyond 2018 would require a major, multibillion pound investment program with like-for-like replacement of many support facilities with little or no prospect of significant new business and hence a return on this investment.
If THORP does shut in 2018, it would mean that by then all site reprocessing will have ceased because Magnox reprocessing (at the so called B205 plant) was suppose to end the year before. But serious doubts about this has been raised by NDA itself. The Magnox Operating Plan (MOP9) and accompanying Strategy Position Paper reveal how the NDA has been forced into a ‘pick and mix’ approach because of what it describes as the inconsistent and unpredictable performance of the plant and associated facilities.
When the last operating plan MOP8, published in 2010, had projected a plant closure in 2016, the date was based on a ‘single assumed’ annual throughput being achieved. Continuing poor performance however resulted in an almost immediate extension of the closure date to 2017, and even this is now is deemed to be ‘increasingly unrealistic’. MOP9 now tentatively suggests at least 2 closure dates (or something between the two) for B205 by assuming two different annual reprocessing rates – an upper bound of 740 tons per year and 450 tons per year lower bound. Put in context, the latter rate tallies almost exactly with the average throughput achieved annually by B205 over the last 5 years of operation, whilst the upper bound of 740 tons per year has not been achieved for 8 years.
As the NDA publications show, 3800 tons of magnox fuel remained due for reprocessing as at April this year - 3000 tons held in reactor/dry storage and 800 tons in pond storage at Sellafield or reactor sites. Reprocessing the 3800 tons of magnox fuel remained due for reprocessing, at 740 tons per year would see a 2017/18 closure of the reprocessing plant whereas, at 450 tons per year, reprocessing would continue to 2020 at least. Added to this workload is the 44 tons of metallic fuel from the Dounreay Fast Reactor (DFR), with transports to Sellafield expected to begin from Scotland this year. MOP9 recognises that the addition of this fuel could impact on the overall MOP program but confirms that, with priority given to magnox fuel, reprocessing the DFR fuel will not be allowed to significantly extend the pro-gram without a strategy review.
Though a number of initiatives to improve reprocessing performance are incorporated in a Magnox Throughput Improvement Plan (MTIP) set up last year, the NDA acknowledges that if improvements do not materialize, the annual throughput rate of 450 tons for B205 would ‘seem a reasonable value to select’ and will result in a 2020 end to reprocessing. If implemented, it will result in further years’ of radioactive discharges to the environment from the reprocessing plant at levels that pose an added threat – denied by the NDA - to meeting the already jeopar-dized international treaty targets on marine pollution signed up to by the UK Government at the OSPAR convention in 1998. At greatest risk would be the target of concentrations of radioactivity in the marine environment being ‘close to zero’ by 2020.
In operational terms, this ‘reasonable value’ of 450 tons per year represents a significant downgrading of reprocessing targets made by the NDA just 5 months ago in a supplement to its much vaun-ted Sellafield Plan. Described as ’the first credible and underpinned lifetime plan for the Sellafield site’, it projected throughput rates for magnox reprocessing from 2012 to 2017 which ranged from 650800 tons per year. Given the well documented frailties and problems of the ageing reprocessing plant and associated facilities – and its recent track record - these projections were patently incredible and appear to have been plucked from thin air rather than being based on a professional appraisal of the plant’s operational capabilities.
Although a large proportion of the 10,000 strong Sellafield workforce is employed on reprocessing, the anticipated number of job losses is not as great as first expected due to more focus on removing Sellafield’s high-hazard risks and increased NDA financial resources to accelerate decommissioning pro-jects. It is also possible that the government will eventually give the go-ahead for a second Mox plutonium recycling plant.
Source: NuClear News 42, July 2012 / CORE Press release, 20 July 2012
Contact: Cumbrians Opposed to a Ra-dioactive Environment (CORE), Dry Hall, Broughton Mills, Broughton-in-Furness, Cumbria LA20 6AZ, U.K.
Tel: +44 1229 716523