The Space Distribution Of Dose Rate By MC Research And Safety Analysis Of Nuclear Power Plant Spent Fuel Pool

This thesis comes from the horizontal topic research project of Nuclear PowerInstitute of China. In recent years, with the rapid development of nuclear power, theused fuel unloading from the reactor is increasing. The storage of spent fuel hasbecome a very important part in the process of nuclear fuel cycle. At the same time,it has become an important research topic about the radiation safety and critical safetyproblem in the process spent fuel storage.Currently, the research about the spent fuel radiation shielding calculation andcritical safety are not enough both domestic and abroad. While the spent fuel has ahigh-level radioactive, high-calorie, and other characteristics, in the event of anaccident, it will have great radiation hazards on the surrounding workplace; thereforeit has very vital significance to strengthen the radiation safety and critical safetyresearch about the spent fuel storage place.This thesis use ORIGEN-Ⅱ and MCNP5to calculate, first of all, to analysis themain fuel module radioactive fission products in a certain burn up spent fuel, get thegamma ray energy group of distribution, establish the precise MC model of spent fuelassemble, using the monte-carlo to calculate the radiation shielding of spent fuelassemble, get the dose rate distribution curve about the spent fuel storage pool. At thesame time, through analysis the critical safety of spent fuel storage pool in normalcondition and loss water condition, can better direct the nuclear safety management ofspent fuel storage pool. This thesis uses the dose rate and critical safety byORIGEN-Ⅱ and MCNP5program; the main conclusions are as follows:(1)Through accurate analysis the radionuclide and gamma ray energy group ofspent fuel assemble, modify the spent fuel source model in MC, in this method we canaccurate simulation spent fuel assemble dose rate distribution. (2)By using of MCNP5to calculate the dose rate distribution of spent fuelstorage pool, apply the repeated structure filling function to establish the MC modelof whole fuel pool, through grid partition the space of spent fuel pool, we can get theradiation distribution above the spent fuel assemble in the spent fuel pool.(3)According to the radiation protection regulations rules(EJ316-88), analyzethe radiation levels of spent fuel pool in different loss water situations, divide thespent fuel pool into four work areas. they are common working place, continuousworking place，limited working place and charter working place. We can provide theradiation protection guidance to the working staff in different accident conditions.(4)Adopt two different calculation method to analyze the critical safety ofspent fuel storage pool in normal working conditions and accident conditions.TheKeff value are0.92276and0.50899in two conditions. According to the existingstorage layout, the spent fuel storage pool won’t happen supercritical accident whilespent fuel assembles has not melted.(5)We can get ideal result of calculation by using ORIGEN-Ⅱand MCNP5program combined to analysis the radiation shielding and critical safety of spent fuelpool. According to the research we can provide a certain reference for the aftermaintenance work and spent fuel storage layout, reduced the accident probability,which are caused by human behaviors.