Beyond Design Basis Accident Source Terms and Release Fraction Mixes for a Typical CANDU-6 NPP

Abstract

Operational Intervention Levels (OILs) developed by the International Atomic Energy Agency (IAEA) are used to develop specific response procedures to promptly implement protective actions or other actions during a nuclear or radiological emergency. The latest IAEA methodology derives OILs directly from source term information following accidents. To aid in this effort, this study develops the necessary set of source term mixes based on the Point Lepreau NPP design for input to the IAEA methodology. The source terms and release mix information can also be utilized to support plume modeling and dose assessment for emergency preparedness and response. The severe accident code MAAP4-CANDU was utilized to assess several highly unlikely severe accident scenarios to derive the radionuclide mixtures found inside containment and released to the environment for each discrete core damage state. Results show noble gases, halogens, and alkali metals have a higher fractional release compared to the other fission products.