Intermediate level waste (ILW)

Intermediate level waste is the waste that, because of its higher radioactivity concentration and/or higher concentration of long-lived radionuclides, does not fit into the previous LLW category. ILW may contain long-lived radio­nuclides, in particular, long-lived fission products and alpha emitting radio­nuclides that will not decay to a level of activity concentration acceptable for near-surface disposal during the time for which institutional controls can be relied upon. However, ILW needs no provision, or only limited provi­sion, for heat dissipation during its handling, storage and disposal. The activity concentration of bulk radionuclides, as well as minor long-lived radionuclides used to distinguish between LLW and ILW are not universally agreed upon. Moreover, the upper activity concentration limits for ILW are not universally agreed upon. These limits and concentrations are site — specific and they shall be established in each individual case by the regulator, based on a safety analysis of the disposal option being considered. Some guidelines about the limiting values for long-lived radionuclide activity concentrations can be found in Table 2.1.

ILW is typically generated at NPP as a result of treatment (concentra­tion) of primary waste. Another significant source is reprocessing of spent fuel. ILW requires a greater degree of containment and isolation than LLW and disposal in subsurface repositories at depths of the order of tens of metres to a few hundred metres.

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