PST user`s guide

The Parametric Source Term (PST) software allows estimation of radioactivity release fractions for Level 2 Probabilistic Safety Assessments (PSAs). PST was developed at the Idaho National Engineering Laboratory (INEL) for the Nuclear Regulatory Commission`s (NRC`s) Accident Sequence Precursor (ASP) Program. PST contains a framework of equations that model activity transport between volumes in the release pathway from the core, through the vessel, through the containment, and to the environment. PST quickly obtains exact solutions to differential equations for activity transport in each volume for each time interval. PST provides a superior method for source term estimation because it: ensures conservation of activity transported across various volumes in the release pathway; provides limited consideration of the time-dependent behavior of input parameter uncertainty distributions; allows input to be quantified using state-of-the-art severe accident analysis code results; increases modeling flexibility because linkage between volumes is specified by user input; and allows other types of Light Water Reactor (LWR) plant designs to be evaluated with minimal modifications. PST is a microcomputer-based system that allows the analyst more flexibility than a mainframe system. PST has been developed to run with both MS DOS and MS Windows 95/NT operating systems. PST has the capability to load ASP Source Term Vector (STV) information, import pre-specified default input for the 6 Pressurized Water Reactors (PWRs) initially analyzed in the NRC ASP program, allow input value modifications for release fraction sensitivity studies, export user-specified default input for the LWR being modeled, report results of radioactivity release calculations at each time interval, and generate formatted results that can interface with other risk assessment codes. This report describes the PST model and provides guidelines for using PST