Benchmarking of PC-COSYMA and COSYMA to estimate doses under postulated accident scenario

Full text: COSYMA (code system from MARIA) is extensively being used for the assessment of off-site radiological consequences of accidental release of radioactive material to the environment. COSYMA is intended for probabilistic safety analysis (PSA Level III) as well as deterministic calculations. It can be used to evaluate the health effects, impact of countermeasure and economic costs of postulated accidental releases. The near early (NE) and near late (NL) mainframe version and PC version of the code have been implemented on personal computer. This code has been used for assessing the off-site consequences arising out of the postulated release due to triplet failures (LOCA, ECCS and containment inlet damper failures) as per the Chernobyl committee's report (report of the task force on review of Indian nuclear power plants in the light of accident at Chernobyl). The meteorological conditions considered are applicable to Kakarapar atomic power station (KAPS) site. The results of analysis of this study are presented in this paper. Cloud shine, ground shine, inhalation, resuspension from ground deposited activity and skin doses from material deposited on skin are exposure pathways considered for estimating acute health effects. Short-term dose is integrated to one month except cloud shine, which may last for a day. Estimation of the dose for PSA level III are done using PC version of the code. Similar evaluations were also done using the mainframe version of the code. Reproducibility of the results obtained using the two versions are also checked. It has been found that there is about 2% variation in the estimated mean doses provided the same weather sequences are employed in these two codes