Safety Assessment of Depressurization Accident in High Temperature Gas Cooled Reactor (HTGR) Using System Dynamics (SD) Method;pp. 381-390
Authors: (Tae-Ho Woo, Soon-Ho Lee, Department of Nuclear Engineering, Seoul National University, Gwanak-gu, Seoul, Korea, and others)
Abstract: The advanced dynamical safety assessment is introduced for the analysis of the high temperature gas cooled reactor (HTGR) which is applicable for the modular pebble bed reactor (MPBR). The dynamical algorithm is adjusted for the safety assessment. An easier and reliable output is addressed. The poison xenon is contributed to the decrease of reactor power. The operatorís action is investigated for the manual action of SCRAM. The feedback of power increase causes to the temperature decrease. The accident scenario is changeable following the proposed conditions. The realistic analysis is constructed in the simple algorithm. The commercial computer package, Vensim, is used of the situations. Using system dynamics (SD) method, the event quantification is performed for the event flows, stocks, and feedback by the single and double arrow lines. Prof. Jay Forrest in the Massachusetts Institute of Technology (MIT) produced SD for the non-linear characteristics of the social and economical system. Several dynamical scenarios of the complex system are tested using SD. The organizations by the transitions of the time are quantified by the SD. Furthermore, there are some decision-making related researches. The top event of the event is power and temperature stable. It is not always successful in all periods. It is affected by the human factor, poison, and some other physical variables. So, this paper shows that the event scenario cannot guarantee the safety measure situation in the very danger accident like gas duct failure. The proposed accident in the nuclear power plant can produce unexpected results. So, it is necessary to analyze each step of the sequence using relevant tools like the SD algorithm. There are several factors including the economic and safety factors which are considered for the reliability of the modeling simulations.