Numerical Simulating Studies On PWR's Capability Of Producing WGPu

Nuclear weapons are weapons of mass destruction,any possible use of which would have a significant impact on global security and human survival.The infinite proliferation of nuclear weapons increases the probability of nuclear weapon employment.Therefore,the international society has been thinking on the preventing of proliferation on the day the bomb was created.Weapon usable fissile material is the essential one for the development of nuclear weapons,so a vital way to prevent the proliferation of nuclear weapons is to control the acquisition of weapon usable fissile material.Nuclear technology is of dual-use of military and civilian.If free from economic considerations,it is possible that weapon-grade plutonium(WGPu)would be produced in any nuclear reactors feeding with uranium.How to prevent unauthorized diversion of production technologies for civilian nuclear material to the production of military nuclear material has become a big challenge for the international non-proliferation system.Some countries have already mastered the production methods and techniques of fissile materials through civil nuclear program,which have led to the increase of the risk of some weapon usable nuclear material being diverted into military.Japan is a typical case of this problem.Japan has advanced nuclear technologies and a mature nuclear industry system,a large number of nuclear spent fuel(NSF)discharged from its commercial power nuclear reactors,and adopts the technical route of uranium-plutonium closed cycle,which can be used to separate plutonium materials for nuclear weapons.Whether or not to develop nuclear weapon depends only on its political decisions.It is a great challenge for the security of countries all over the world facing a new country armed with nuclear weapons in such an international situation.In the thesis,the numerical simulation is carried out to analyze the production of WGPu and spatial distribution in pressurized water reactor(PWR),and the correlation between characteristic nuclide ratio and the reprocessing of NSF containing WGPu is preliminarily explored.In order to calculate Pu abundance and stable Xe isotope ratio with cooling time,the cooling calculation function is added to the parallel computation code of three-dimensional neutron transport and burnup calculation MCORGS.The subzones' burnup-calculating function of MC particle transport software platform JMCT is proposed and assisted to finish.Improved JMCT can calculate the radial burnup distribution of the whole nuclear reactor core and nuclide components in every subzone,based on which the radial burnup zones of nuclear reactors can be divided.Benchmark tests are carried out to verify and validate improved MCORGS and JMCT,which show the calculation results of MCORGS and JMCT are reliable.In order to calculate the temporal and spatial distribution of WGPu amount in PWR,the physical model of PWR is constructed,according to Takahama-3,and its calculation model is established.Based on data of Takahama-3,the model of PWR presented by Kord Smith,and BEAVRS benchmark available in the literature,as well as a series of reasonable simplifications,the three dimension geometrical parameters and nuclide components of the PWR's internals and fuel assemblies in the reactor core are designed.According to the simulation result of the infinite pin-cell model of Takahama-3,the effect of boron concentration and temperature/density of moderator water on reactivity and Pu abundance are analyzed,and the component parameters of the moderator and boron were determined.Based on the physical model of typical PMR,its reactor core pin-by-pin calculation model and the calculation model of burnup zones are established.According to the simulation results of burnup calculation,the temporal and spatial distribution of WGPu's amount in PWR when it is operating is obtained.The amount and possible scenarios of WGPu produced in commercial PWR are analyzed.In order to prevent nuclear proliferation that uses commercial power nuclear reactors and reprocessing plants to obtain WGPu,the stable Xe isotope ratio contented in discharged NSF is simulated,and obtain preliminarily the correlation between the mass ratio of 132Xe and 134Xe and the reprocessing of NSF containing WGPu.In all,the physical model of PWR is constructed,and its burnup calculation model is established.The temporal and spatial distribution of WGPu in PWR is obtained though simulation calculation,based on which the amount of WGPu and possible scenarios are analyzed.Numerical simulation is carried out to screen out a preliminary method of judging whether NSF containing WGPu is reprocessed.The thesis provides a technical idea to assess the capacity of nuclear reactors to produce WGPu and to prevent reprocessing NFS containing WGPu.