Estimation of total effective dose equivalent (TEDE) following a hypothetical nuclear power release of radionuclides from a 4- loop Pressurized Water Reactor (PWR)

Safety is an essential aspect in design and analysis of nuclear reactors to keep the system in a safe condition in case of accidents. One vital issue in safety assessment is the management of radiological accident and dispersion of released radionuclides during nuclear accident. With the increase in interest of nuclear energy and its introduction in the overall national energy mix, a corresponding environmental impact and radiological assessment is imperative. Modeling atmospheric dispersion is the first step of such assessments using versatile computer codes. Atmospheric dispersion modeling and radiological safety analysis have been performed for a postulated accident scenario of the genetic Enrico Fermi 4-loop PWR NPP in Trino, a kind of nuclear reactor type to be introduced in Ghana's energy mix. The postulated procedure considered would be applied Ghana in selecting a suitable site for its nuclear power program as a requirement by licensee. The source term was generated from an inventory of peak radioisotope activities released by using the isotope generation code ORIGEN2. The MACCS2 and RASCAL 3.0.5 code were employed to perform the atmospheric transport and dispersion modeling. The idea is to select the best method that can better predict the radiological assessment in terms of radionuclide concentration and released doses from a nuclear facility. The codes were used to estimate the Total Effective Dose Equivalent (TEDE) and investigate how the release would be distributed to human organs as a function of distance. The adopted methodology was the use of predominant site-specific meteorological data and dispersion modeling. The study considered calculation of release dose of three selected radionuclide (Cs-137, 1-131 and Sr-90) due to their health implication on the environment during accident conditions. The results indicate that the maximum TEDE value of 1.2E-09Sv and 3.8E-80 were estimated from RASCAL and MACCS2 code respectively at a distance of 50km from the source term, as a contribution of the three main radionuclides selected with significant importance as far as Radiation Protection is concerned. The results are in agreement with a reference dispersion model RODOS with TEDE value of 1.4E-08 Sv at 50km distance. The comparison of the results proved the efficacy and reliance of the models; and its relevance for reactor licensing purposes. The dose values are far below the regulatory limits even in the event of severe accident scenario and good for site selection licensing approval. (au)