Current Arrangements and Requirements for the Conditioning, Packaging and Storage of Intermediate Level Radioactive Waste: Joint RWMAC/NuSAC Report

ANNEX 4

REPORTED PROGRESS WITH PROBLEM AREAS IDENTIFIED IN THE 1998 NII/HSE REVIEW OF ILW STORAGE

Introduction

This annex sets out reports of progress, supplied by BNFL, UKAEA and BE, in respect of problem areas identified by the 1998 NII/HSE review of UK ILW storage ⁷. For each, the questions posed are followed by the responses provided.

BNFL

Question

What progress has been made in respect of the following point(s) raised in the November 1998 NII review of ILW storage?

• the development of strategies for the conditioning and packaging of ILW in underground vaults at Magnox sites (see page 21 of NII/HSE review). What specific challenges are envisaged?
• with the retrieval, conditioning and packaging of wastes from B41 (dry silo), B38 (wet silo), B211 (medium active liquors), B241 (floc storage tanks) and the PCM in the B100 series of stores, B209, B136, B229 and Drigg [see page 9 onwards of NII/HSE review].

Answer

Underground vaults - with respect to underground vaults at Magnox reactor sites, it is intended to retrieve the raw wastes from such vaults in the period following station shutdown which should meet the expectation stated in the NII review that these facilities will "be emptied within ten years of station closure".

B41 - The process route is being developed, based on retrieval from the silo, sorting in a separate building and encapsulation in Box Encapsulation Plant. Recognising that it will be some years before the silo is empty, the interim safety will be substantially improved by the imminent provision of a permanent argon supply to inert the building.

B38 - The plan was to commence by retrieving the swarf from compartments 19-22 first to gain experience. This work is now complete, with a retrieval of around 80 per cent achieved. Design of the equipment for the other phases is in hand.

B211 and B212 - Activity is due to be encapsulated in WPEP after liquor removal:

1. Medium Active Concentrate
   The original stock of 5,000 cubic metres (m³) has been progressively reduced since 1994 to 3,400 m³. Typical treatment rates are 750 m³ in a full year, although there are fresh arisings of about 200 m³ per annum. The rate of processing has been restricted to that giving a 90 terabecquerels (TBq) maximum discharge of technetium. There are proposals by EA to reduce this limit to 10 TBq, which would end MAC processing.

2. Salt Evaporator Concentrate
   2,300 m³ was treated in 1996 and 1997. The process operates on a 3-tank regime of one filling, one being processed and one being held for at least three years for ruthenium-106 decay. The next tank is due to be processed from 2002. Current stocks are 3,800 m³ and are at equilibrium.

3. Solvent
   Current stocks are 2,800 m³. The Solvent Treatment Plant is now being commissioned but is likely to be limited by the iodine discharge permitted. Treatment rates are programmed to be 400-m³ pa with arisings at 180 m³pa.

B241 - The overbuilding is now complete and equipment is being installed to allow tank homogenisation and discharge. Processing will be via EARP and WPEP and is due to start 2002/3. There is a large alpha inventory (2,080 TBq) which is predominantly americium-241. The rate of processing is dependent upon achieving very high decontamination of the liquor, but the 7,400 m³ is expected to be processed at around 600m³ per annum.

PCM - It is intended to store PCM (either raw or treated) in the Engineered Drum Stores (EDS). EDS2 is currently undergoing inactive commissioning and will provide the space (together with EDS3) to receive the PCM. The Waste Treatment Complex has been actively commissioned by compacting and encapsulating 2,000 drums of low plutonium content (i.e., less than 50 grams of plutonium). A Letter of Comfort exists for 260 grams but regulatory agreement is currently outstanding. There is also a programme of work to improve the repeatability and precision of the plutonium measuring equipment. WTC is due to restart in April 2002.

The B100 series of stores are due to be vacated to EDS by 2004. It will commence as soon as EDS2 is available, and some will be processed en route at WTC. The B300 series will also be vacated but the timescale is under discussion with NII.

All crates have been removed from the North Group Compound.

An overbuilding is currently being provided for B136 to allow entry and processing of the contents. A good inventory of quadrants 1 to 3 has been obtained. 1360 drums are expected to be generated from quadrants 1 and 2. The waste retrieval is scheduled to be undertaken by 2004.

Drigg - Since 1997, 950 drums have been sent from Drigg to Sellafield out of a total of 8,500 eventually envisaged.

Drummed waste exists in B720. The transport route was established in 1997 and material is being sent to Sellafield.

Five magazines of the original 10 still exist and contain PCM packages. A new entrance building is to be provided for each magazine, encompassing a sentencing and packing facility. Work on the first magazine commenced in 1998, the product being drummed waste. Approximately half of the contents have been removed. From 2002, it is envisaged that two magazines will be emptied in parallel to allow all PCM to be removed by 2006. Appropriate extra transport containers are being obtained.

BE

Question

What progress has been made with the following point raised in the November 1998 NII review of ILW storage?

• assessing the suitability of reactor voids as locations for long-term ILW storage, and whether the wastes current stored there will require retrieval, packaging and new stores (see page 29 of the 1998 NII/HSE review).

Answer

The suitability of the purpose designed reactor building High Active Debris Vaults (HADVs) as locations for the long-term storage of solid ILW has been the subject of detailed consideration within the BEG HADV Project. The HADV project commenced in 1997 to address the concerns surrounding the long-term storage of solid ILW within the AGR debris vaults until retrieval during Stage 3 decommissioning. This project has resulted in the production of a number of site specific and generic studies, which underpin the current strategy for all the AGR vaults, and associated ILW accumulated therein.

Much of the BEG HADV project was included in BE's submission to the recent HSE/NII Quinquennial Review (QQR) of BE's decommissioning strategy. In the HSE/NII report from this review, NII concurred with BE's view that deferral of the retrieval of debris from HADVs is justified subject to certain provisos relating to additional monitoring and inspection of the vaults. A technical specification for a design review has been produced to address all the recommendations/additional requirements identified within the debris vault long-term management safety justifications. The work identified within this design review incorporates the NI provisos.

UKAEA

Question

What progress has been made in respect of the following point(s) raised in the November 1998 NII review of ILW storage?

• development of plans for conditioning plant for solid ILW in B462.27. The transfer of PCM to Sellafield, and the encapsulation of the ILW components from sea disposal drums? (see page 36 of the 1998 NII review). Also in respect of PCM arisings from Winfrith (NII page 36).

Answer

Harwell B462.27 conditioning plant - Work is current underway to agree the functional requirements of the cementation plant and associated flexible waste handling facility. This work will lead to further work on optioneering and preliminary design before a tender exercise for the design and build of the Harwell Waste Encapsulation and Treatment Plant (WETP). UKAEA aim to have a cementation plant available by 2010.

Transfer of PCM to Sellafield - UKAEA and BNFL have formed a joint working group to explore the issues and practicalities associated with the processing of UKAEA PCM at Sellafield. UKAEA is in receipt of a letter from BNFL agreeing in principle that the UKAEA PCM can be processed in the Waste Treatment Complex (WTC) at Sellafield and that this forms part of BNFL's business plan for WTC.

However the business plan, indeed the strategy for the management of PCM, is currently under internal review within BNFL. UKAEA is awaiting the outcome of the BNFL review of WTC before we can progress a formal agreement for the transfer of UKAEA PCM to Sellafield. As fallback strategies, UKAEA are discussing with AWE the potential use of a supercompaction facility at Aldermaston for Harwell PCM and considering the provision of a purpose built facility at Dounreay for Dounreay PCM. This would be one of the areas where there would be a benefit in a Liabilities Management Authority addressing UK wide issues.

Sea Disposal Drums - A number of drums of waste originally destined for sea disposal are in storage at Harwell in B462.19 following the 1983 moratorium on this method of disposal. These concreted drums have different owners (UKAEA, MoD, BNFL and Amersham). During 1998/99, UKAEA sea-disposal drums containing only tritium and carbon-14 were transferred to the Amersham Cardiff facility. For the purpose of planning for the remaining drums it is currently intended that:

• the UKAEA drums containing beta-gamma waste will be opened and the waste sorted in B459. The LLW component will be disposed to Drigg as it arises. The dismantling activities will take place during the next 5-6 years;
• the UKAEA drums containing contact-handling ILW will be dismantled and segregated in the Pressurised Suite Area of the B462 complex. This work is planned to start in 2004 (after the repackaging of Winfrith PCM). The PCM fraction will be stored on-site before being sent to BNFL Sellafield Waste Treatment Complex with the other stocks of PCM from Harwell;
• the MoD drums contain waste that has decayed to LLW. These drums will be packed into ISO containers and disposed to Drigg;
• Amersham will dismantle their sea disposal drums in their own separately licensed facilities on the Harwell site;
• the drums belonging to BNFL will be returned to Sellafield where BNFL will make arrangements for dealing with them.

Winfrith PCM - UKAEA is currently in the process of transferring all of the Winfrith PCM to Harwell. Once at Harwell, the waste will be retrieved from the current 100 litre storage drums, characterised, shredded and transferred to a 200 litre galvanised drum for storage pending the availability of a packaging route.

MOD (AWE)

Question

What progress has been made in respect of the following point(s) raised in the November 1998 NII review of ILW storage.

• the two stores of brick construction, converted from 1950's vintage laboratories and containing drummed PCM, that were to be emptied into a modern stores by end of 1999;
• the store of 1970's brick construction, also containing drummed PCM, due to be emptied by the end of 2002;
• progress with preparing for and treating the sludges held in rubber lined steel tanks mentioned in the NII review; the treatment plant for these was said to be planned for the end of 2002.

Answer

One of the 1950's brick construction stores has been emptied; approximately 1,000 drums were removed, overpacked and are now stored in a modern purpose-built facility. The PCM drums from the second store are programmed to be moved by July 2002.

The 1970's store is programmed to be emptied early in 2004.

The sludge from two of the tanks has been encapsulated in a cementitious grout and disposed of as LLW to BNFL Drigg. The engineering pre-works to enable the encapsulation of the remaining tanks should be completed by the end of 2002 with encapsulation starting early in 2003. NII Licence Instrument 33 requires that AWE immobilise the remaining sludge by 2008. It is anticipated that the programme will be completed well before this date.