DARLINGTON NUCLEAR GENERATING STATION (DNGS) HABITABILITY STUDY WITH MAAP-CANDU 4.0.7C AND MAAP5

摘要

In response to the nuclear accident at the Fukushima Dai-ichi Nuclear Power Plant, the Darlington Nuclear Generating Station (DNGS) has procured Emergency Mitigating Equipment (EMEs). To support the installation and servicing of the EMEs, ERIN Engineering along with OPG and Kinectrics has performed a DNGS site-wide habitability assessment. The habitability assessment quantified the radiological conditions and the dose in vital ex-plant and in-plant areas for a series of postulated single-unit and multi-unit CANDU accidents. This first-of-a-kind approach combined MAAP-CANDU source term analysis and containment response with MAAP5 calculations of site-wide fission product transport and dose assessment. In addition to providing crucial knowledge to DNGS regarding where workers may operate during such accidents, these studies also provided knowledge regarding the dose received by operators via radiation shine from the environment back into the various DNGS control rooms. Specific dose results for a series of 7-day accident calculations were provided for 65 rooms in the reactor building and service areas, including the dose in 3 control rooms which could potentially be occupied throughout the accident. Results indicated that habitability in vital area was generally acceptable allowing for successful installation and servicing of the EMEs. In some instances, temporary evacuation of the highest dose areas was indicated. This is consistent with the Fukushima Dai-ichi experience. Finally, sensitivity calculations indicated significant dose reductions could be obtained by implementing accident management actions, such as using gravity drain systems to provide extended steam generator inventory and heat removal.