Report on the outcome from the consultancy Safety-related issues for the disposal of intermediate level waste (ILW) Drafted at Consultants’ Meeting to draft a technical document on disposal facilities for intermediate level waste 22-26 April 2013, Vienna, Austria TM-45865 Technical Meeting on the Disposal of Intermediate Level Waste Vienna 9-13 September 2013 Report on the outcome from the consultancy

Report on the outcome from the consultancy 1 – Overview TM-45865 Technical Meeting on the Disposal of Intermediate Level Waste Vienna 9-13 September 2013 Report on the outcome from the consultancy

Report on the outcome from the consultancy Scope This document is intended to be used as supplemental technical document for the existing IAEA Safety Standards by examining a number of issues to determine appropriate disposal options for the ILW and for factors that may contribute to the safety case. It can constitute a first draft in the development of a TECDOC/safety report of which the purpose is to assist in the use of existing guides for the development of ILW specific disposal facilities. TM-45865 Technical Meeting on the Disposal of Intermediate Level Waste Vienna 9-13 September 2013 Report on the outcome from the consultancy

Existing IAEA definitions for ILW ILW is defined in IAEA Safety Guide GSG-1 as “waste that contains long lived radionuclides in quantities that need a greater degree of containment and isolation from the biosphere than is provided by near surface disposal.“ IAEA safety glossary defines low and intermediate level waste (LILW) as “Radioactive waste with radiological characteristics between those of exempt waste and high level waste.“ Also in the IAEA safety glossary, the terms short lived and long lived waste is introduced (half life <> 30y) TM-45865 Technical Meeting on the Disposal of Intermediate Level Waste Vienna 9-13 September 2013 Report on the outcome from the consultancy

Outcome from the consultancy Intermediate-level waste (ILW) is, from a disposal and safety case perspective, situated between low-level waste which can be disposed of in a near surface facility and high-level waste that must be disposed in a deep geological formation. Some contain a relatively high activity, but a low content of long lived radionuclides whereas other have a relatively high content of long lived radionuclides, but with low to moderate activity. The volume of ILW is usually more significant than HLW. This justifies the treatment of ILW as separate waste stream(s). For some ILW with significant amounts of uranium or plutonium, criticality and safeguards can be an issue. Heat generation can be an issue for the sizing of disposal cells for some ILW. Concerning chemtoxicity the situation of some ILW waste can be similar to LLW waste whereas it is generally not an issue with HLW waste. With regard to mechanical and chemical disturbances induced by the waste packages, the properties of ILW are generally closer to low level waste characteristics than to HLW characteristics. TM-45865 Technical Meeting on the Disposal of Intermediate Level Waste Vienna 9-13 September 2013 Report on the outcome from the consultancy

Report on the outcome from the consultancy Disposal depth IAEA Safety Guide GSG-1: “Disposal in a facility at a depth of between a few tens and a few hundreds of metres is indicated for ILW” “Disposal at such depths has the potential to provide a long period of isolation from the accessible environment if both the natural barriers and the engineered barriers of the disposal system are selected properly.” “Another important advantage of disposal at intermediate depths is that (..) the likelihood of inadvertent human intrusion is greatly reduced. Consequently, long term safety for disposal facilities at such intermediate depths will not depend on the application of institutional controls.” TM-45865 Technical Meeting on the Disposal of Intermediate Level Waste Vienna 9-13 September 2013 Report on the outcome from the consultancy

Outcome from the consultancy It is not recommended to discuss an ILW disposal facility only in terms of depth but rather by considering many influencing properties that can provide an acceptable degree of containment and isolation. The depth of the disposal facility should be primarily determined based on a set of site specific properties, such as site geology, permafrost and glaciation, erosion, redox, as well as waste properties and facility design. The safety case has to define an appropriate time-scale, consistent with: the natural evolution of the site and the considered depth, the characteristics of the waste, in particular the reduction of activity with time as a function of the half-life of radionuclides. An assessment timescale over 1 million years may require disposal in a deep geological formation. An assessment timescale between 10,000 and 100,000 years may result in disposal at a swallower depth. TM-45865 Technical Meeting on the Disposal of Intermediate Level Waste Vienna 9-13 September 2013 Report on the outcome from the consultancy

Safety case and design issues Human intrusion scenarios must be considered in the safety case after the end of the institutional control period (no longer than a few hundred years). Limits must be identified for the acceptable residual activity within the waste after the institutional control period. The acceptable content in long lived radionuclides is a function of the type of intrusion scenarios to be considered and therefore a function of repository depth. The design considerations for an ILW disposal facility are typically no different than for other types of disposal facilities; however, the final design will be specific to the characteristics of the waste. The large variety and the composition of the ILW waste needs to consider various issues that is not associated with HLW waste such as gas generation and compatibility between different waste types as well as between the waste and the engineering system. TM-45865 Technical Meeting on the Disposal of Intermediate Level Waste Vienna 9-13 September 2013 Report on the outcome from the consultancy

Report on the outcome from the consultancy Recommendations (1/2) Revisit the definition of the ILW (GSG-1) to potentially provide more flexibility. Consideration on long-lived LLW and short-lived ILW could be included without imposing the types of disposal facilities. The depth of the disposal facility should be adapted to the characteristics of the waste such as the half-life as well as site-specific geological and technological features. Historically, the depth has been associated with the class of wastes (LLW  near- surface disposal). This has resulted in confusion with respect to disposal facilities for ILW. Consideration should be given to one or more separate waste streams for ILW as a function of half-life. Some ILW can be characterized by intermediate half-life nuclides (radium 226, carbon 14 or americium 241) which are compatible with an intermediate timescale that can be used in the safety case. This timescale lies between short- lived LLW and HLW. ILW has a higher diversity than HLW and different mechanisms are to be considered in the design and safety case. Consideration should be given to develop specific disposal options for ILW waste streams, which might result in co-location with other types of waste in some cases. TM-45865 Technical Meeting on the Disposal of Intermediate Level Waste Vienna 9-13 September 2013 Report on the outcome from the consultancy

Report on the outcome from the consultancy Recommendations (2/2) While developing disposal options for ILW, the existing IAEA safety guides relating to LLW and HLW can be used as appropriate. Existing guides could be updated to make them more efficient for ILW for instance to take into consideration all potential characteristics of ILW and to adapt the wording. TM-45865 Technical Meeting on the Disposal of Intermediate Level Waste Vienna 9-13 September 2013 Report on the outcome from the consultancy