MCR Safety Dose Assessment in LOCA Condition of Westinghouse Type NPP

The MCR(Main Control Room) dose assessment is performed assuming LOCA(Loss Of Coolant Accident) which is the most limiting design basis accident and assumes the largest fission product release to the containment. For MCR dose assessment, some input parameters are needed. They are onsite atmospheric dispersion factor, accumulated break flow from each break point, initial condition for LOCA and etc. In this paper, ARCON96, RADTRAD and SCALE6.1 are used as analysis tools. This requirement is originated from TMI accident issue and the lesson. In 2003, the additional requirement is published by GL 2003-01. According to the documents, the additional requirement is the experimental data acquisition and the data check for the criteria of MCR habitability from MCR leakage test. MCR dose assessment is carried out by calculations of onsite dispersion factor, LOCA fission products release analysis and dose conversion factors. From this study, we find some conclusions as below: a. X/Q value at the early part of the accident has significant effect on MCR dose results b. Atmospheric stability is important factor that affects the X/Q. c. Categories (E~G) of atmosphere stability are the key factor in the case of X/Q value increase. d. FGR13/ICRP72 is more conservative than FGR11/12. From these conclusions we can find what major elements of MCR dose in LOCA could be considered to increase the safety margin.