RWMAC's Advice to Ministers on the Radioactive Waste Implications of Reprocessing

ANNEX 6

STORAGE FACILITIES AT SELLAFIELD

HLW

There is only one HLW store - the Vitrified Product Store - in operation at Sellafield. This has a capacity of about 1,200m³(8000 containers). Total arisings of HLW estimated on the basis of volumes of fuel to be reprocessed given in Table 3 and the conversion rates given in Table 4 is of the order 1,345m ³, assuming no substitution/see Table 7). This would be reduced to about 1,295m³ if substitution were permitted. For the Combined Extended scenario, the corresponding figures without and with substitution would be of the order 1,495m³ and 1,245m³ respectively. BNFL believe that, despite this apparent excess of arisings over capacity, it will be possible to accommodate all eventual VHLW arisings in the existing store if substitution is allowed. This is because they believe it will be possible to reduce volume production rates in future, due, for example, to needs for fewer flushings of the THORP plant. RWMAC has erred on the side of caution in its own assessment that additional storage is likely to be necessary, particularly if substitution is not ultimately allowed.

ILW

ILW stores at THORP may broadly be considered to be of three generic types:

• Encapsulated Product Stores (EPSs) for radioactive waste with a significant beta/gamma radiation content (this category includes the Box Encapsulation Plant Store (BEPS) and the Waste Packaging and Encapsulation Plant (WPEP))

• Engineered Drum Stores (EDSs) for radioactive waste containing alpha radiation

• Miscellaneous Beta Gamma Waste Store (MBGWS) for radioactive wastes with a high beta/gamma, but low alpha, radiation content which are large and bulky and therefore incompatible with the EPS family of stores.

Current BNFL planning for these ILW stores is as follows:

BNFL actually have outline planning permission for ten EPSs. One of the EPS-classified stores currently in operation is the WPEP. That which is under construction is the BEPS.

The three EPS stores currently in operation have a total capacity of 30,000m³. The three further stores planned will provide a further 17,000m³ each, adding about another 50,000m³. According to current forecasts, there will be about 10,000m³ of spare capacity available in these stores. Thus, broadly, any scenario that adds more than an extra 10,000m³ of beta/gamma ILW relative to the Combined Reference scenario would result in the need for an additional store. Any which reduces arising of this form of ILW by more than 7,000 m³ would reduce the numbers of stores required.

BNFL estimate that the Combined Extended scenario will provide an extra 17,900 m³ of beta/gamma waste relative to the combined reference scenario. The Combined Early Termination scenario reduces such arisings by 11,100m³. On this basis the Combined Extended scenario could increase the EPS store requirement by one over the Combined Reference scenario. Whilst it would appear that a store might be saved under the Combined Early Termination scenario, this may not be the case if substitution is allowed.

At the moment there is one EDS store in operation and a further store is under construction. No further stores are anticipated. The combined capacity of the stores will be about 13,000m³ and the volume of wastes requiring storage under the Combined Reference scenario will be 12,000m³. Thus any scenario which increases alpha waste volume by more than 1,000m³ will require additional storage capacity. For the Combined Extended scenario the additional generation of alpha waste is estimated to be 1,400m³. This additional requirement is marginal and BNFL believe it will be possible to accommodate the waste either via a minor store extension or, more likely, improvements in packaging efficiencies or waste minimisation. This analysis again assumes that all waste remains in the UK (i.e. that there is no waste substitution). There can be no savings in the number of EDS, even though the Combined Early Termination scenario would reduce arisings by 1,000m³, as the second EDS store is already under construction.

This is presently only one MBGWS in operation, and no further stores are anticipated. The capacity of the store is about 4,700m³ and the volume of relevant wastes requiring storage in the Combined Reference case will be about 3,300m³. The Combined Extended scenario is estimated to increase relevant waste arisings by 1,900m³ relative to the Combined Reference case. The reprocess existing Magnox fuel stop THORP now scenario will reduce relevant arisings by 1000m³. Combined Extended arisings will exceed MBGWS store capacity by 500m³. Although this suggests the need for an additional store, it may be possible to accommodate this either through a store extension or greater packaging efficiency. As only one store exists, there will be no scope for savings.

LLW

There is no long-term holding of LLW as this is all disposed off to Drigg.

Plutonium

As of 1 April 2000, approximately 70t of plutonium, by metal weight, was stored at Sellafield in two facilities, the Magnox product store complex and the THORP product store. Actual storage is in the form of plutonium oxide powder (PuO₂) which itself is some 10 per cent heavier than the metal content.

Plutonium management is governed by international safeguards and anti-proliferation systems administered world-wide by the International Atomic Energy Agency (IAEA) and regionally by the European Atomic Energy Community (Euratom). Both IAEA and Euratom inspectors and facilities are installed at Sellafield and at other appropriate UK civil nuclear installations.

Magnox PuO₂ is stored in an aluminium inner can. Each pack contains about 5.5 kg of plutonium (by metal weight). Originally PVC-based intermediate bags were used which were subject to radiation-induced deterioration. As a result programmes of repackaging into non-PVC intermediate bags have been undertaken. THORP PuO₂ is stored in steel triple packs each containing approximately 7.5 kg of material.

The Magnox store has recently been extended to have a capacity of 80 tonnes. It is currently about 60 per cent full and will take Magnox product under the reference case scenario until 2010. Any decision to further extend the store would not be required until about 2006.

The THORP store has a capacity of approximately 45 t of metal weight plutonium. It has been sized to take the output from baseload. This is the amount to be reprocessed over the first 10 years, and was originally 6,000 t at a reactor burn-up of 40 Gwd/te. The baseload feedstock is now 7,000 t. The actual baseload fuel recycled is actually of lower reactor burn-up than assumed in the original capacity plan for the plant. This effectively means that less plutonium has been generated and therefore the store capacity is sufficient for the increased baseload fuel requirement.

The THORP plutonium store is currently over 30 per cent full. With no use of PuO₂ in mixed oxide (MOX) fuel - that is, if the Sellafield MOX plant (SMP) does not operate - the store will become full by about 2004. If the MOX plant operates, the life of the store will be extended. BNFL has a provision of £50m in its current business plan to double the capacity of the THORP plutonium store.

Under the Magnox Reference scenario, there would then be no need for another Magnox plutonium store. If Magnox reprocessing continues beyond around 2010, as it would under the Extended scenario, another store would be needed. Note that the revised Magnox business plan announced by BNFL in May 2000 foresees an end to Magnox reprocessing in 2012. Under the THORP Reference scenario, another store would not be needed if there was a relatively high demand for MOX fuel. However some of the residues from MOX production might have to be held in the Magnox plutonium store. If THORP reprocessing was stopped, there would be no need for another store after 2004. Under the Extended THORP scenario, which involves mainly additional reprocessing of overseas fuel, whether or not another store was needed would depend on the timing of overseas return either as plutonium oxide or MOX.

Uranium

Magnox uranium product is stored in drums, each of which holds about 800 kg of oxide. There is approximately 200 tonnes of buffer store capacity at Sellafield. The main stock of Magnox uranium oxide, 27,000 drums, is held at Capenhurst. There are additional 10,000 drums held at Chapelcross, but this material is to be moved to Capenhurst. Present facilities at Capenhurst are sufficient for 60-75,000 tonnes.

THORP has two uranium product stores, including a recent extension. The THORP uranium product is held in drums each containing approximately 180 kg of oxide. The original THORP store has a capacity for 28,000 drums. The new drum store will hold about another 30,000 drums.

The existing storage at Capenhurst would be sufficient to hold all Magnox uranium products, even under the Extended scenario.

Under the THORP Stop Now scenario all uranium oxide could be held in the original THORP uranium store. The existing second store would not be loaded. Under the reference scenario, the second store would be loaded and a third store would be needed around 2004. Whether or not a fourth store was needed under the Extended scenario would depend on the timing of return of overseas products.