The objective of this research is to develop methods to analyze the offsite consequences of specific sodium fast reactor (SFR) licensing basis events as used to characterize the safety of a nuclear plant design in a license application. An algorithm has been developed which assesses pool heatup, containment load, radionuclide transport, and release from containment during accident scenarios. To analyze temperature transients, the SFR pool has been divided into two, well-mixed regions separated by a metal divider referred to as a redan. Heatup due to fission power or decay heat in the core and heat removal by either the Intermediate Heat Exchanger (IHX) or passive heat removal system drive the energy balance. A reactor kinetics model is also included in this analysis. Radionuclide transport from the cover gas region to containment, as well as the heat and pressure load on containment are analyzed using MELCOR. Subsequent releases from containment to the environment are then analyzed using WinMACCS or Regulatory Guide 1.145 to calculate offsite consequences. Both WinMACCS and Regulatory Guide 1.145 employ a Gaussian dispersion model and meteorological data from an Eastern U.S. site.
Several accident scenarios are examined in the radionuclide release and transport analysis: varying sizes of sodium spills inside containment, arrested melt scenarios, an energetic recriticality event, core uncovery and a case of sustained sodium vaporization. The scenarios will be analyzed for both containment intact and containment failed, where the containment has a design basis leak rate of 1.0 v/o per day. Resulting offsite consequences are then compared with the NRC’S frequency-consequence (F-C) curve in the Technology Neutral Framework (TNF) for compliance. Calculations are also performed to examine the implications of satisfying the F-C curve and its relationship to satisfaction of the NRC’s Quantitative Health Objectives.