Development of the ASYST VER 3.x LWR/HPWR Best Estimate Integral Code

ASYST (Adaptive SYStem Thermal-hydraulics) is a new BEPU integral code being developed through an international collaborative project, ADTP (ASYST Development and Training Program). ASYST VER 3, designed to support the analysis of LWRs/HPWRs, is intended to address some of the outstanding safety analysis issues identified in the Fukushima Daiichi R&D activities. VER 3 also includes the integrated uncertainty analysis (IUA) option developed originally for RELAP/SCDAPSIM as well as several options for integrated desktop simulator GUI environments including GRAPE, Adv3DGUI, and RHYS developed by 3rd parties from Japan, Mexico, and the US. ASYST is also backwards I/O compatible with RELAP/SCDAPSIM so existing RELAP5 and RELAP/SCDAPSIM input models will run with little or no changes. ASYST VER 3.7, with advanced HPWR fuel channel and Fukushima-Daiichi related modeling improvements, planned for release over the coming year, will incorporate the latest modeling options developed for SCDAPSIM/MOD3.7.