Development assessment of RELAP5/MOD3 using the Semiscale natural circulation tests

This paper documents the simulation of the Semiscale natural circulation (SNC) tests SNC-01, SNC-03, and SNC-04 using RELAP5/MOD3 for developmental assessment. The main purpose of applying MOD3 to these tests is to show the code's capability of single- and two-phase natural circulation, reflux heat transfer, and countercurrent flow with the improved models. A brief description of the Semiscale test facility and RELAP5/MOD3 system model is given, followed by a description of some code results and analysis of the phenomena simulated. The RELAP5/MOD3 systems analysis code has simulated the Semiscale natural circulation tests. In general, the code calculations are in good agreement with the measured data at the higher PCS and steam generator mass inventories. Additionally, the code performance at the higher PCS mass inventories is an improvement over previous RELAP5/MOD2 calculations of this problem