S.Mahmoud Altaha - Department of Nuclear Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
Masoud Mansouri - Department of Nuclear Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
Gholamreza jahanfarnia - Department of Nuclear Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran

In this paper, uncertainty and sensitivity of high pressure and low pressure injection systems and also accumulators are investigated in the VVER1000/V446 nuclear reactor during the small break LOCA. The analysis is performed by RELAP5/Mod 3.2 Code for nodalization and simulation of nuclear power plant. The GRS method is used to calculate the minimum number of code calculation to achieve 95% of tolerance limit and confidence level. For a conservative analysis of the accident, the loss of power to the NPP and failure of one accumulator, and also two emergency core cooling systems (ECCS) in loops 2 and 3 of the primary and secondary circuits are considered when SB-LOCA has occurred. The setpoint of accumulator pressure, high pressure injection pump and low pressure injection pump vary in the working interval of each system. The Spearman rank correlation method is used to predict the sensitivity of each setpoint of safety systems. The maximum temperature of clad is analyzed in two conditions. In 1st state, each system setpoint is changed by considering of constant status for other systems. In 2nd state, all of those system setpoint are altered. The results are shown that the accumulators made a most sensitivity of the maximum temperature of clad. Furthermore, the HPIS pumps have relatively little influence on the SB-LOCA. It can be seen from the second state that the new setpoint achieved, which cause to lower temperature of maximum clad comparing with a default setpoint of emergency core cooling systems.

uncertainty and sensitivity analysis, small break loss of coolant accident, VVER-1000 reactor, GRS method,ECCS