Solid Radioactive Waste Strategy Report.pdf - UK EPR

EPR UK
N° NESH-G/2008/en/0123
REV. A PAGE 49 / 257
6.4 Storage of Radioactive Waste to Allow Reclassification
A major factor in the management of radioactive wastes is the time period for which they remain
hazardous. It is uniquely inherent in the nature of radioactive materials that, through the
passage of time, they become less radioactive. For radioactive wastes where the activity is
dominated by relatively short lived isotopes, the waste can be reclassified to a lower hazard
category after a suitable period of interim storage.
The radioactivity of operational ILW arising from the operation of the UK EPR is dominated at
the time of arising by relatively short lived radionuclides. After a period of safe interim storage,
the radioactivity of some of this waste will have decayed to such levels that the waste would no
longer be classified as ILW. This would present the opportunity to manage the waste as LLW.
Decay storage is an important technique for the re-classification or exemption of radioactive
wastes. Decay storage is often used for wastes arising from medical uses of radioactive
material or for some sealed sources [Ref. 29] where the radioactive material is typically pure
and has a short half-life (e.g. less than one hundred days).
Decay storage is a robust strategy for waste management as it does not require any mechanical
or chemical waste treatment, and thus does not generate any secondary radioactive discharges.
The site operator must simply ensure that the waste is securely and safely stored for the period
needed for decay.
With regard to the UK EPR, some of the waste generated during operations is classified as ILW
at the time of generation. The dominant radioisotopes at the time of generation in these wastes
are cobalt-60 (half life of 5.27 years), caesium-137 (half life of 30.2 years) and iron-55 (half-life
of 2.7 years). The design lifetime of the EPR interim waste store is 100 years, with operational
wastes being interim stored for a maximum period of between 40 years (for wastes arising at
the end of operations) and 100 years (for wastes arising near the beginning of operations). This
storage period is greater than the half lives of the dominant radioisotopes within most
operational wastes streams at the time of waste generation.
A portion of the waste that is categorised as ILW at the time of generation will have decayed
sufficiently during the period of interim storage on site that it could be reclassified as LLW at the
time of disposal. The paragraphs below illustrate this strategy with respect to EPR operational
waste arisings.