Simulation of LOFA and RIA for the IEA-R1 research reactor using the code PARET

The thermal hydraulic system code PARET has been applied to model the Brazilian IEA-R1 research reactor. The PARET model is limited to the description for the fuel element groups inside the reactor core. The developed model was verified by simulation of the steady state operation at the nominal power of 5 MW. According to the safety significance of postulated initiating events two selected design basis accidents corresponding to loss of flow accident (LOFA) with reactor scram and reactivity insertion accident (RIA) without scram, have been analyzed. The results of LOFA simulation demonstrate the code ability to simulate the phenomena of flow reversal characterizing the flow turnaround from forced downward to natural upward circulation. The prevailing natural circulation after the flow reversal guarantees the removal of residual decay heat. The maximum clad temperature of the hot channel reaches its maximum of about 64 degree C after 35 s after the initiation of the transient. The step reactivity insertion of 2 mk leads to increasing the reactor power up to 1.6 times of the nominal value but without exceeding the design limit of the fuel elements. (author)