Development of CANDU-specific operational intervention levels

Abstract

Operational intervention levels (OILs) are measurement-based criteria to indicate whether the prompt implementation of protective response actions (e.g.,evacuation, relocation, food restrictions) should be undertaken in a nuclear emergency. The IAEA published a new set in 2017 based on light water reactors, while the uncertainties on whether they could be applicable to CANDU reactors (which have different fuel burn-up and severe accident progression characteristics) are addressed in this study. By and large, the CANDU-specific OIL(t,mix) function values were similar to the light water reactor-based IAEA values. One exception was OIL7 for food restrictions, which required that an additional marker radionuclide, 106Ru, be considered in addition to 131I and 137Cs, to reduce the uncertainty of the OIL. The CANDU-specific OIL values that result from this study will help to inform national authorities on how to adapt OILs to the emergency response arrangements in Canada and other countries operating CANDU reactors.