Intermediate-level waste (ILW)

ILW is waste which has limited heat generation capacity that need not be considered for its disposal or in its disposal option (typically below 2 kW/m3) with intermediate short-lived and/or intermediate long-lived radionuclide concentrations. ILW consists mainly of irradiated uranium (uranium, actinides, other activation products and fission products) in smaller quantities, or cooled irradiated uranium or in the form of irradiated uranium contaminated waste as generated in the isotope production facili­ties and the operation of the SAFARI research reactor. Unirradiated uranium (from the NFC) could also fall into this waste class, especially when it occurs in higher concentrations. Waste management is aimed at prevent­ing unirradiated uranium falling into this waste class. Long-lived sealed sources, for example Ra-226 or SHARS (spent high activity sealed radioac­tive sources) could also fall in this waste class. SHARS of shorter lived radionuclides may have such high activity levels that the intrusion dose after the institutional control period is in excess of 10 mSv/a as specified for near surface disposal.

The long-lived radionuclide half life (Ti/2 > 30.2 years) concentrations could on average typically be 4,000 Bq/g and 40,000 Bq/g for a and в у emit­ters, respectively. Criteria for long-lived radionuclide concentrations need to be justified for a specific repository. Criteria are justifiable in the case of a specific repository if inherent intrusion dose after the institutional control period is between 10 mSv/a and 100 mSv/a.

For irradiated uranium waste, containers are shielded to ensure surface dose rate levels <2 mSv/h. Unirradiated uranium waste could be pre-treated in unshielded containers. ILW that is removed from authorized containment systems shall be processed to ensure a solid waste form in a waste package that is suitable for handling, transport and storage for a period of 50 years. Additional requirements may be prescribed for a specific ILW repository. Corporate pre-disposal management standards need to be specified to ensure good practice and waste packages that are compliant and verifiable in terms of the applied IAEA standards [5]. These generic standards ought to be used as reference standards for the evaluation of ILW disposal con­cepts and for the long-term safety of planned ILW repositories. Disposal of ILW needs a high degree of containment and isolation from the biosphere over a long period of time that is obtainable by intermediate disposal at depths of tens to hundreds of metres.

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