Modeling a nuclear research reactor and radiation dose estimation in an accident scenario

“A detailed, flexible three-dimensional (3D) model of the Missouri S&T Reactor (MSTR) with a heterogeneous core geometry was developed using the Standardized Computer Analyses for Licensing Evaluation (SCALE). A Graphical User Interface (GUI) was developed for SCALE, which allows the user to generate an input file automatically. The SCALE model was validated with a Monte Carlo N-Particle Transport (MCNP) model of the MSTR. The validation process was based on the criticality calculations using the Criticality Safety Analysis Sequence (CSAS6). Three geometrical models were examined. The SCALE model that has the full detailed geometry showed a good agreement with the MCNP results. However, the CSAS6 results related to the keff were slightly overestimated. Furthermore, the difference in the predicted critical Control Rod (CR) height was less than 2%. The developed SCALE model was utilized to generate a 3D map of the radiation dose estimation using a hybrid Monte Carlo simulation with automatic variance reduction techniques under normal operations. The radiation dose estimation in all accessible areas showed a dose rate below the annual exposure limit for the public in accordance with the International Commission on Radiological Protection (ICRP) recommendations and guidance. Subsequently, the code was used to simulate two accident scenarios for the MSTR. Both scenarios were initiated by an EF-5 tornado that stroke the MSTR and destroyed the walls. In the first scenario, the beam port was damaged, which created a path for the reactor pool water to flood the experimental floor. In the second scenario, the pool water was fully sucked-out by the tornado. The SCALE-6.2.3 model was able to predict the 3D map of the radiation dose within 200 ft diameter for both accident scenarios”--Abstract, page iii