Considerations on a Validation Matrix for System Analysis Codes of Pebble Bed Modular HTRs

Abstract

The modular High Temperature Reactor (HTR) experienced substantial development over the past two decades in China. At present, the 10 MWth experimental reactor HTR-10 is under operation and the 200 MWe demonstration power plant HTR-PM is in its commissioning phase. Both of the HTR-10 and the HTR-PM are pebble bed HTRs designed by the institute of nuclear and new energy technology (INET) of Tsinghua University. In the design and analysis of modular HTRs, system analysis codes play an important role in predicting the reactor behaviour under both normal operation and accident conditions. According to China’s nuclear safety regulations, codes and models employed in the HTR system analysis must be verified and validated in conformance with a specified procedure. Thus, a flowchart is recommended in this paper for the validation of system analysis codes. As the first step of the flowchart, a phenomena identification and ranking table (PIRT) process has been performed on the subject of the HTR-PM thermal hydraulics and accident analysis. In this paper, the PIRT process is introduced and the PIRT results are presented. With the purpose of developing a validation matrix, test data have been collected mainly from the operation history and various tests of the HTR-10. On such basis, some considerations on developing a validation matrix are discussed to benefit the code validation work.