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

7. PROGRESS WITH CONDITIONING, "CHALLENGING" WASTES AND BNFL'S "INTERIM SAFE STORAGE" STRATEGY

7.1 This chapter starts by providing an overview of progress with the conditioning and packaging of ILW. It then focuses on the nature of "challenging"' wastes and highlights their importance. This is followed by an outline of different views about the impact of proposals for the regulation of radioactive discharges on the treatment of ILW. Finally, a discussion is provided of the development of an "Interim Safe Storage" strategy for the management of ILW on the Sellafield site.

Overview of progress with conditioning and packaging

7.2 Of the ILW currently held, what is striking is the relatively small percentage that has been put in a final conditioned form. As of 1 April 1998, only about 8,500 m³ - equivalent to about 12 per cent of the then existing holding - was in final conditioned form ³. Virtually all of this conditioned waste is held by BNFL, although UKAEA also hold a limited amount.

7.3 A considerable amount of work has, however, been undertaken in order to move forward with the conditioning of untreated ILW. One measure of this is the number of LoCs that have been issued by Nirex. Up until 31 March 2001, Nirex had issued LoCs for 69 packaging proposals. Of these 25 were in final form, 13 were to the interim level and 31 were conceptual (see paragraph 6.6). This corresponds to 45,700m³ of waste covered by final stage LoCs, 2,200m³ covered by interim LoCs and 26,100m³ covered by conceptual LoCs. That is, a total of 74,000m³ of ILW have been covered by LoCs of one sort or another. The vast majority of this coverage is for current and forecast operational wastes.

7.4 These figures mean that, based on the 1998 UK Radioactive Waste Inventory, about 35 per cent by volume of held and forecast operational and decommissioning ILW is covered by some form of LoC. About a further 7 per cent has also been the subject of one or more LoAs.

7.5 In addition, of course, BNFL and UKAEA have various operational conditioning and packaging plants. These include; the Magnox Encapsulation Plant, the Waste Encapsulation Plant, the Waste Packaging and Encapsulation Plant and Waste Treatment Complex at Sellafield; the WAGR Encapsulation Plant at UKAEA Sellafield and the Cementation Plant at UKAEA Dounreay.

7.6 Nonetheless, whilst acknowledging such progress, it is difficult to escape the overall conclusion that provision for, and progress with, the conditioning and packaging of the UK's ILW remains at a relatively early stage. Although there are various reasons for this - including previous policy presumptions against early treatment, and consequent ability to defer expenditure on new ILW conditioning and storage facilities - RWMAC/NuSAC consider that it is now unsatisfactory that only a small proportion of ILW has been treated. In order to rectify the situation, it is necessary for waste producers to have clearly articulated strategies and plans for the conditioning packaging and storage of ILW. Clear targets and objectives should be set for such work, against which progress is monitored and openly reported.

'Challenging' Wastes

7.7 A substantial proportion of untreated ILW can be described as 'challenging'. Nirex informed the joint study that challenging ILWs can include:

• Historic mixtures with uncertain properties. These are associated with facilities that have accepted wastes from a number of different processes and sources. They include the Sellafield B41 silo, B38 silo, and Miscellaneous Beta/Gamma store, the Dounreay shaft and wet silo and the Harwell B462 facility. Such wastes require facilities to undertake retrieval, characterisation, and where necessary segregation, prior to conditioning.
• Materials where effective immobilisation is difficult. These include: soft low density and/or absorbent wastes such as plastics; wastes with restricted access and or small porosity such as HEPA filters, filter beds and ion exchange columns; and wastes which are containerised or wrapped such as drummed vault wastes, bagged waste items and supercompacted hard wastes.
• Materials with inherent hazards. These include wastes containing accessible Wigner Energy (such as low temperature irradiated graphite), reactive metals, wastes containing pyrophoric materials such as uranium hydride, and wastes with high fissile content.

7.8 Nirex points out that these types of ILW are not mutually exclusive. It estimates that approximately 28,000m³ of highly heterogeneous waste streams - just under 38 per cent of holdings as of 1 April 1998 - could be described as challenging wastes. Nirex has also warned that the actual scale and distribution of these wastes is being unfolded through the LoC process, so that accurate figures cannot currently be predicted.

7.9 NII has focussed considerable attention on "historic" wastes ^* on the Sellafield, Dounreay and, to a lesser extent, Harwell sites. Such wastes may be poorly characterised, potentially mobile, physically and chemically degraded, and in 40-50 year old facilities that fall below current standards and are subject to further deterioration. Attention was drawn to such wastes in NII's review of ILW storage arrangements, undertaken following the 1997 RCF decision ⁶. In its report, NII identified a number of specific wastes and facilities that it wished to see addressed. As part of the current joint study, producers were asked what progress had been made in respect of the key NII concerns. The responses are given in Annex 4. In addition, RWMAC/NuSAC note that the UKAEA produced its Dounreay Site Restoration Plan in October 2000 ¹⁵ to address the issues of ILW management raised in respect of that site.

7.10 When asked about whether sufficient progress is being made, NII drew particular attention to the situation at Sellafield:

"NII has become increasingly concerned at the lack of progress in addressing the accumulations of legacy ILW and other radioactive material on the site. As a consequence, NII has engaged BNFL in high level discussion, and has pressed for the development of comprehensive and integrated strategies that cover the whole site, and that take into account the full extent of the retrieval, packaging and storage facilities that are required. BNFL is now attaching a high priority to this area and is in the process of carrying out the strategic planning."

NII added that there have been recent instances where it has judged it necessary to issue legal instruments to BNFL to target areas on the Sellafield site where waste management practice or progress has not been acceptable.

7.11 In RWMAC/NuSAC's view, considerable importance should be attached to the development and implementation of plans for the conditioning, packaging and storage of challenging ILW, including historic wastes. There is a clear need to ensure that adequate resources are devoted to this work and that substantive progress is made.

The impact of proposals for the regulation of radioactive discharges

7.12 The main civil waste producers were asked whether the implementation of the UK's OSPAR commitments to reduce discharges to sea ⁶, would cause any significant difficulties for the conditioning, packaging and storage of ILW. Although BE and UKAEA did not anticipate that they would, BNFL expressed strong concerns about EA's current proposals for the regulation of discharges from Sellafield. In particular, the company raised concerns that the proposals would severely restrict its ability to treat historic wastes:

"As and when historic waste is processed, it inevitably causes some small discharges. There is no allowance for any new activity in EA's current proposals - in theory, not even for any investigative work. BNFL has suggested that the concept of a reserve authorisation is appropriate where additional discharges are permitted up to agreed levels for specific purposes."

7.13 In response, EA outlined its position that normally operators should be able to plan conditioning programmes in such a way as to proceed within authorised limits (hence the importance of operators developing well formulated strategies and programmes for legacy wastes). However, in circumstances where there is a short term "sudden" problem (e.g., unexpected discharges during the retrieval of sludges), EA would use its powers to vary an authorisation promptly, without public consultation if necessary. EA stressed that in the latter case, there must be compelling reasons for such a course of action.

7.14 The Joint RWMAC/NuSAC Working Group was sceptical that this "fast track" could be achieved in practice, and suggested that EA consider a shadow certificate that might be activated in closely defined circumstances (i.e., NII agreement that retrieval and conditioning of a historic waste stream is required to a specific timescale). However, EA stated that it had considered and rejected BNFL's similar proposal for a reserve schedule, on the grounds that it was not possible to be sufficiently clear about the circumstances under which it would be activated. EA also pointed out that the detail needed for consultation on a reserve schedule had not been supplied by BNFL despite requests. In response, BNFL argued that such detail will only emerge after treatment processes have been established.

7.15 RWMAC/NuSAC are concerned that the disagreement between BNFL and EA about the implications of the latter's proposals for the regulation of discharges on the treatment of historic wastes remains unresolved. It is recommended that Government should review this issue in conjunction with the industry and regulators, so that ways of resolving it can be taken into account in finalising the UK Discharge Strategy and Statutory Guidance ^8,9 to the environment agencies.

BNFL's "Interim Safe Storage" strategy

7.16 The development by BNFL of an ILW management strategy for the Sellafield site is of particular importance given the quantity and nature of the ILW on site, BNFL's forthright views on the policy, regulatory and LoC situation, and the concerns of NII on the lack of progress in dealing with the site's historic wastes.

7.17 In the course of the November 2001 announcement about the creation of the LMA, the Secretary of State reported that BNFL:

".. has .. developed a new strategy for processing its intermediate level wastes which the Board endorsed today. Under the new strategy, which the company has discussed in outline with all its regulators, it is proposed that the wastes will be removed from existing, ageing stores as soon as is reasonably practicable and will be treated and packaged to enable them to be stored, safely, for decades."

7.18 BNFL's proposed new strategy for ILW management on the Sellafield site is known as "Interim Safe Storage", referred to hereafter as ISS. The company explained to RWMAC/NuSAC that its objective is to prepare waste products suitable for disposal, but that "safety issues may cause BNFL, on balance, to propose the packaging of waste in the short term in such a way that it is unlikely to be directly disposable". In such cases, the company added, it would be necessary to explain the likely steps to be taken in the future to achieve disposability. Such cases should, however, achieve a condition where - "as far as is reasonably practicable" - the waste is in a chemically and physically stable form so that safety can be achieved by passive means.

7.19 The company further stated that the extent to which waste packages in the ISS regime would meet long-term requirements is expected to vary for different waste forms. In particular four types of waste package could result:

• waste conditioned so that it meets all present and foreseeable future requirements;
• more processing required to meet future needs;
• complete re-working to meet future needs;
• where there are sufficient unknowns to have no clarity on the ability to meet future needs.

BNFL argues that it is for the company to make the case for a particular ISS regime, with a clear explanation of any proposed trade off between improving the safety of storage regimes and leaving a requirement for future processing or rework. As such, the company intends to comply with Nirex's packaging advice, and seek to avoid foreclosing future management options, "so far as is reasonably practicable".

7.20 On the face of it, BNFL's new ISS strategy is consistent with NII guidance ¹⁰ and NII's views on the operation of the LoC system (chapter 6). Specifically with regard to interim packaging, NII informed the joint study that "every case would be treated on its merits and needs to be justified by the licensee".

7.21 The position of the environment agencies is less easy to gauge. EA's guidance ¹¹ places great emphasis on ensuring disposability, but recognises the need to ensure safety and environmental protection during storage. The EA guidance also emphasises the desirability of avoiding the need for reworking conditioned wastes. EA informed the joint study that it had been involved in tripartite discussions with BNFL and NII as the strategy has evolved, which had enabled it to stress the importance of having regard to "all the factors set out in paragraph 113 of Cm 2919".

7.22 Nirex also informed the joint study that it has endorsed cases where waste producers have wished to package initially just for interim storage, on the grounds that the balance between short and long term safety dictates that this is the preferred strategy. However, Nirex added that in such cases a position had been achieved "whereby the act of packaging for interim storage does not compromise the ability to achieve, at a later time, a package consistent with eventual disposal". Based on previous experience reported to the joint study, it is likely that Nirex would not wish to endorse packaging proposals which would require complete reworking to achieve disposability.

7.23 When asked about the adoption of interim packaging arrangements, the UKAEA informed RWMAC/NUSAC that:

".. it is not UKAEA's intent or policy to adopt interim packaging solutions. UKAEA aim to identify final packaging solutions, in agreement with Nirex for all waste streams. The only two cases where it could be argued that UKAEA are adopting such an interim strategy is the packaging of remotely handled ILW in the B462 complex at Harwell and the packaging of Dragon fuel."

The UKAEA further explained that in both cases an approach was being taken which would facilitate conditioning at a later date.

7.24 RWMAC/NuSAC consider that BNFL's proposed ISS strategy for the Sellafield site is a potentially significant development in the field of ILW management and requires careful consideration by national and local stakeholders. In particular, in view of the genuine safety concerns that exist about the storage of historic wastes on the Sellafield site, RWMAC/NuSAC acknowledge that it may be necessary to adopt interim packaging arrangements for specific waste streams after a careful weighing of all the relevant factors. However, the Committees consider that such arrangements, without the cover of a LoC, require convincing and transparent case-by-case justification. In addition, where interim packaging can be justified, RWMAC/NuSAC strongly favour approaches which facilitate final treatment at a later date, rather than requiring complete re-working to meet future needs.

* While the term "historic" wastes has been used in this report, the term "legacy" wastes is also sometimes used in other contexts.