KAIST-Micro Modular Reactor Steady State Modeling with GAMMA+ Code

Some safety and transient analyses of the MMR should be carried out whether the designed reactor exceeds safety margin when a major accident occurs. The GAMMA+ code which is developed by KAERI is one of the transient analysis codes to simulate S-CO₂ system. However, existing GAMMA+ code was coupled with NIST database to employ CO₂ properties directly. This coupling method requires long time to simulate the whole S-CO₂ power cycle. Therefore, the authors attempted to implement CO₂ thermal and transport properties into GAMMA+ code by using CO₂ property equations directly, rather than connecting NIST database externally. After the modification, CPU time was improved by 16 times compared to the previous coupling. To test the implementation a benchmark problem was selected and solved. The results of the benchmark problem calculation results as well as nodalization of the KAIST-MMR are presented in this paper. Previous GAMMA+ Code connected with NIST was too slow when modeling a fully integrated system. Thus, each property equation should be coded in the GAMMA+ code to reduce calculation time. The modified GAMMA+ code reduces CPU time and has a negligible difference about 0.02 - 0.06%. Moreover, PCHE correlation and compressor performance map were also modeled in the modified GAMMA+ code