Evaluation of advanced accumulator in a VVER-1000 reactor in loss of coolant accident

The advanced accumulator is a passive system which gradually decreases the high flow into a low flow. The role of the fluidic device is to obtain an additional safety margin by increasing golden time to cope in the LOCA. In this paper, the effect of using the safety injection tank and the fluidic device, called advanced accumulator, in a wide spectrum of LOCA break sizes without emergency core cooling systems (ECCS) of a VVER-1000 is evaluated. Firstly, the main component of primary and secondary loops of Bushehr nuclear power plant (BNPP) is modeled by RELAP5. Secondly, the performance of the model is assessed in steady-state and LOCA conditions by comparing the obtained results with the plant's FSAR. Thirdly, a model is developed in RELAP5 to simulate the behavior of advanced accumulator and validated by blowdown test in a test facility and MARS-KS code. Finally, the performance of advanced accumulator in the spectrum of 200-300 mm break sizes of LOCA without ECCS. In this range of breaks, the core damage times (CDT) developed from peak cladding temperature (PCT) of 1204 degrees C have been calculated. In accordance with the results, the advanced accumulators can increase the CDT in the whole range of breaks.