LAUSR

Abstract Following our previous works to evaluate the potential capability of Tehran research reactor core to conduct domestic fuel test during irradiation, safety of Tehran MTR-type research reactor containing 20% enriched U3O8-Al fuel plates while performing UO2 fuel rods irradiation experiments must be ensured not only in steady state but also during transients. In this regard, this paper aimed at developing an accurate transient model for safety analysis of TRR mixed-core during probable transients that may occur during fuel irradiation experiments. The main goal of this study is to get confidence that the developed RELAP5 model can be used with quite a lot of accuracy for the prediction of real transient parameters during fuel irradiation. Considering all related safety issues, two experiments which represent a loss of flow accident and a reactivity insertion transient are performed in TRR core containing 32 plate-type fuel assemblies and one rod-type instrumented mini fuel assembly. The results are used to benchmark the developed RELAP5 model prediction of TRR mixed-core behavior during aforementioned transients. In this study, some modifications are also performed in RELAP5 to include heat transfer correlations which are applicable within pressure and temperature operating ranges of TRR mixed-core to improve temperature predictions of the model. Hydraulic parameters, i.e., change of pool and hold-up tank water levels and coolant flow rate through the core as well as thermal parameters like clad and coolant temperature changes and also core power changes are desired parameters to be benchmarked using postulated transients. Good compatibility of experimental data and those predicted by modified RELAP5 model reveals the validity and accuracy of the model to be used for transient analysis in TRR mixed-core during irradiation experiments.