RWMAC Annual Report 2001/2002

Chapter 4: Conditioning, packaging and storage of ILW

Introduction

4.1 Early in 2001, RWMAC and NuSAC were asked to undertake a joint study of the conditioning, packaging and storage of intermediate level radioactive waste (ILW) in the United Kingdom. The Committees considered this issue to be of importance in the light of HSE concerns about the storage conditions of some ILW, increasing emphasis on the need for potentially mobile wastes to be conditioned, and the dramatically lengthened times over which interim storage of ILW could be anticipated following the collapse of the Nirex ILW underground repository programme in 1997.

4.2 The report of the joint study was submitted to Ministers and to the Health and Safety Commission in April 2002, and was published in June 2002 ¹. Work on the study was led by a working group, chaired by Mr Fred Barker, with members drawn from each committee (see Annex 2). Drafts of the report were subsequently discussed and finalised by the full membership of both committees.

The current state of ILW

4.3 ILW covers a wide range of waste streams, including materials irradiated in nuclear reactors and used in the reprocessing of spent fuel. As of April 1998 (the time of the most recent official figures), only a small proportion - 12 per cent - of existing ILW had been conditioned: that is put into a form suitable for long-term storage and/or disposal. Most of the remainder is stored in untreated form on licensed nuclear sites.

4.4 There are various reasons for this situation. Government policy prior to 1995 was that ILW should remain untreated for as long as it was safe to do so. This reflected a concern that treatment might foreclose disposal options. The policy also meant that expenditure on new ILW conditioning and storage facilities could be deferred. Although the Cm 2919 White Paper ² relaxed the presumption against early treatment in circumstances where safety or economic benefits could be achieved, it did not provide a major impetus for conditioning programmes.

4.5 In view of the collapse of the Nirex repository programme and concerns about the storage conditions of some untreated wastes, the RWMAC/NuSAC report concluded that ILW conditioning programmes need to be carried forward more vigorously than in the past. To achieve this, it recommended that waste producers should have better articulated strategies and plans, with clear targets and objectives so that progress could be monitored and reported, and with an appropriate allocation of resources, particularly to deal with "historic" wastes. The study highlighted that some wastes are poorly characterised, physically and chemically degraded, and held in old facilities subject to deterioration.

Need for review and development of policy

4.6 The RWMAC/NuSAC report concluded that there is a need for a clear and updated statement of Government policy for the interim management of ILW (pertaining to the period prior to implementation of long-term management options). It expressed concern that national policy regarding the conditioning, packaging and storage of ILW is effectively being set by default - and in a potentially fragmented fashion - by the waste producers, the regulators and Nirex.

4.7 The Government consultation paper, Managing Radioactive Waste Safely (MRWS) ³, focuses primarily on the processes that might be used to formulate policy on the long-term management of solid radioactive wastes. Although some statements on shorter-term issues are contained in MRWS, it does not encompass the full range of issues that must be addressed in developing policy on the conditioning, packaging and storage of ILW.

4.8 The report therefore recommended that the Government should clarify which parts of Cm 2919 are extant and which are not, and take the earliest possible opportunity to develop and set out its policy for ILW conditioning, packaging and interim storage.

Towards passive safe storage

4.9 The report supported the view that, so far as is reasonably practicable, ILW should be stored according to the principles of passive safety set out in NII guidance to its inspectors ⁴. These principles describe the attributes of passive safety, including that the radioactivity be immobile and the waste form and container be chemically and physically stable, so that the need for safety systems, maintenance, monitoring and human intervention is minimised. The report commended the NII's principles, and concurred with the regulator's view that licensees should aim to apply them within a framework of reasonable practicability and cost-effectiveness.

4.10 As ILW conditioning and packaging programmes are developed, there are likely to be tensions around passive safe storage and interpretations of reasonable practicability and cost-effectiveness. Within the framework established by NII guidance, RWMAC/NuSAC considered it legitimate for NII to scrutinise and, where necessary, robustly challenge waste producer proposals, as long as conclusions are reached on the basis of transparent, consistent, case by case judgements that take proper account of all relevant factors.

4.11 Given the extended periods of storage now likely, and regulatory concerns about the storage conditions of some ILW waste streams, the report considered that the NII emphasis on the implementation of programmes to achieve passively safe storage as soon as reasonably practicable is appropriate. This is as long as due recognition is given to the "disposability" of conditioned waste forms (see below) and to the safety-related factors that should influence the timing of specific conditioning programmes.

4.12 The report recommended that Government policy on passively safe storage should be clarified by explicitly endorsing these perspectives.

Interim storage timescales

4.13 There is also a need for Government to clarify its expectation of the timescales for interim storage. This would encourage a greater focus on the standards required for the provision of packages and stores, and help inform local development control and planning decisions. The main waste producers and regulators all broadly accept that it would be prudent to plan for a period of interim storage of the order 100 to 150 years.

Disposability and the Letter of Comfort system

4.14 The report concluded that there is a continuing need for a system that seeks to ensure the disposability of conditioned waste forms, so that disposal options are not foreclosed for future generations. Disposability in this context is defined as the likelihood that a package of conditioned ILW will be acceptable for disposal in a purpose-designed facility. The continuing need for such a system has been brought into sharp focus by NII's emphasis on the early conditioning of wastes.

4.15 Nirex currently provides a system of endorsement that packaged wastes will meet future management requirements, including potential disposal. This is known as the Letter of Comfort (LoC) system, which is operated in three stages (conceptual, interim and final). The system also entails the provision of packaging advice based on standards and performance specifications developed by the company. The packaging advice is currently linked to Nirex's Phased Disposal Concept.

4.16 The report highlighted the importance of operating the LoC system to well founded programmes, with a clear commitment to early discussions about specific conditioning programmes, involving waste producers, the regulatory bodies and Nirex. In particular, the early and sustained involvement of Nirex (or a successor organisation) is important for the timely provision of packaging advice and enabling long-term disposability requirements to be properly considered.

4.17 The report recommended that Government policy on disposability should be clarified by explicitly endorsing these perspectives.

4.18 It was recognised that the disposability of waste forms is central to the environment agencies' responsibilities and, subsequently, that there is a case for enabling the agencies to provide additional "regulatory assurance" that this will usually be achieved. However, the ILW report, like RWMAC's response to MRWS, did not favour the EA suggestion of a new statutory power over the storage of radioactive wastes. This was partly because of the difficulties that are likely to arise from dual regulation. An alternative approach might be to make each of the three stages of LoC subject to endorsement by the appropriate environment agency. This could be stated as an expectation of policy, and be achieved by formal administrative agreement between NII and the appropriate agency. Another approach might be to develop a new statutory role for the agencies based on the issue by them of a "certificate of disposability".

Nirex packaging advice and long-term management options

4.19 At the time of the study, Nirex was assessing the robustness of its packaging advice to a range of long-term management options. The RWMAC/NuSAC report considered it important that Nirex publish its assessments at an early date so that claims for the wider applicability of its packaging advice, and the implications for long-term policy, can be reviewed. The preliminary findings of the Nirex assessment have subsequently been published ⁵.

Fundamental review of the LoC system

4.20 If the current policy review does not result in the adoption of a policy of deep underground disposal, the linkage between the LoC system and Nirex's Phased Disposal Concept will be become increasingly questionable. In such circumstances, the report recommended that the form, institutional location and presentation of the LoC system be made subject to fundamental review.

Interim packaging arrangements

4.21 BNFL's "Interim Safe Storage" (ISS) strategy for the Sellafield site is a significant development in the field of ILW management and requires careful consideration by national and local stakeholders. In view of safety concerns about the storage of historic wastes on the Sellafield site, the report acknowledged that in certain circumstances it might be necessary to adopt interim packaging arrangements for specific waste streams. In this context, an interim packaging arrangement means that a packaged waste has not secured a LoC. However, the report highlighted that "interim" arrangements require convincing and transparent case-by-case justification. In addition, where such arrangements can be justified, it recommended approaches, which facilitate final treatment at a later date, rather than requiring complete re-working to meet future needs.

4.22 RWMAC/NuSAC recommended that Government policy should acknowledge the potential need for interim packaging arrangements, but state an expectation that these would only be adopted in openly declared and justified cases, and with the agreement of NII and appropriate environment agency.

The LMA and the management of ILW

4.23 Lastly, the RWMAC/NuSAC report observed that the Government's decision to set up the LMA - to be responsible for the management of public sector civil nuclear liabilities - further underlines the need for policy clarity on the conditioning, packaging and storage of ILW.

References

¹ Report of a Joint Study by the Radioactive Waste Management Advisory Committee and the Nuclear Safety Advisory Committee: Current Arrangements and Requirements for the Conditioning, Packaging and Storage of Intermediate Level Radioactive Waste, Department for Environment, Food and Rural Affairs, June 2002.

² Review of Radioactive Waste Management Policy: Final Conclusions (Cm 2919), Her Majesty's Stationery Office, July 1995.

³ Managing Radioactive Waste Safely: Proposals for Developing a Policy for Managing Solid Radioactive Waste in the UK, Department for Environment, Food and Rural Affairs et al, September 2001.

⁴ Health and Safety Executive, Nuclear Safety Directorate, Guidance for Inspectors on the Management of Radioactive Materials and Radioactive Waste on Nuclear Licensed Sites, March 2001.

⁵ Compatibility of the Nirex Waste Package Specification with Long-term Waste Management Options, UK Nirex Ltd,July 2002.