engleski

Methodology to calculate radiological impact for NPP Krško life time extension environmental impact assessment

Initially NPP Krško (NEK) was licensed for 40 years of operation (until 2023). To obtain lifetime extension, an Environmental Impact Assessment (EIA) should be performed to evaluate the impact of NEK prolonged operation on the environment. The gaseous radioactivity release from reactor core during possible accidents has the largest potential for environmental impact. It is enveloping any other radioactivity accident and related releases. According to plant’s SAR, a limiting plant accident, from point of view of radiological release, is the Large Break LOCA. The radiological release in case of any possible severe accident (DEC-B or beyond design basis accident (BDBA)) was analysed using Station Black Out (SBO) without mitigation in the first 24 hours and release through passive containment system vent system (PCFVS) as a reference case. It is selected, due to an expected complete core melt, and the fastest and the most conservative radioactivity release within a containment. The methodology used to assess the dose rates and the consequences to the environment at selected distances from NEK in case of DBA LOCA and BDBA SBO scenario was described. It includes calculation of plant specific fuel source term, RADTRAD model calculating isotopic release to the environment and X/Q relative concentrations determined using ARIA Industry Lagrangian particle atmospheric dispersion model and WRF meteorology for distances up to 100 km from release point. For distances up to 200 km RODOS model using simplified spatial and weather data and release source term calculated by RADTRAD can be applied. Although the calculation models are different, the calculated doses at a distance of 100 km from the NPP agree well. The results of performed analyses show that no significant transboundary impact from the Krško NPP, in case of DBA or DEC-B accident, is expected, except possibly at parts of Croatian border.

evironmental impact assessment, life time extension, RADTRAD, SBO, LOCA

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