Study On The Performance Of Neutron Source Of Multiple Beam ADS And Fusion Plasma

As a clean energy source,nuclear energy has been considered as one of the main energy sources to replace fossil energy,but,the rapid development of nuclear energy will also face many problems like nuclear fuel supply and nuclear waste disposal.To solve these problems,the concepts of fusion reactor and accelerator-driven subcritical reactor(ADS)were proposed by researchers.Fusion reactions produce energy by reactions D+D?3He+n+3.27MeV D+T?4He+n+17.6MeV and D+T?4He*+n.However,tritium is a very expensive and short half-life nuclear material.It is difficult pro,vide a large amount of tritium for fusion reactor fuel.Generally speaking,a fusion reactor needs to use neutrons(produced by fusion reactions)to react with lithium in the fusion blanket to produce tritium to achieve self-sustainability.So designing fusion blanket with high tritium multiplication ratio(TBR)has always been one of the key issues in the fusion reactor program.Preconditions for accurate calculation of TBR is to provide accurate neutron source,and that would be one of the main goal of this work.In an ADS device,a large number of fast neutrons could be produced by bombarding heavy metal targets with high energy protons to drive the surrounding sub-critical reactor for nuclear reaction.Fast neutrons can be used to transmutate long-lived fission products,and directly induce fission of 238U or transform it to fissile nuclide 239Pu.However,a strong external neutron source(1017-1018n/s)will generate a high power peak near the spallation target.Therefore,the concept of multi-beam ADS was proposed by researchers.The combination of multiple beam and spallation targets was used to reduce the requirement for a single accelerator.,But the interference between neutron sources may also cause new problems,and that is another central issue of this work.The main high lights of this thesis are as follows:(1)A new algorithm for nuclear reaction in fusion plasma is presented,which can not only calculate the intensity information of fusion neutron source,but also simulate various nuclear reactions besides DD and DT reactions.(2)Neutronics analysis of multi-beam ADS reactor core,including parameters as much effective proliferation factor(keff),power,power peak and so on,has been done to give an optimized scheme.The structure of this thesis is organized as follows:Firstly,the neutronics of multi-beam ADS is analyzed.This part of the work is divided into two steps:The first step is to test the code Visual BUS 4.2.The core of the International Atomic Energy Agency's benchmark fast reactor BN-600 was modeled in detail.The parameters keff,fuel Doppler coefficient,density coefficient,radial expansion coefficient,axial expansion coefficient and effective delayed neutron fraction were calculated.The calculated results are in agreement with the published in the literature.Based on the test results,it is concluded that the code Visual BUS 4.2 meets the requirements for the neutronics simulation of the multi-beam ADS.The second step is neutronics analysis of multi-beam ADS.ADS-NWT was used as the reference core.Neutronics simulations of single-beam,three-beam,four-beam,six-beam and seven-beam were carried out.The calculated parameters include keff,power,power density distribution and neutron flux spectrum.An interference of spallation neutrons and fission neutrons on keff and power was observed and studied in detail.This finding is of great significances fore the core design of multi-beam ADS.In the second part of this work,a new fusion plasma nuclear reaction algorithm was constructed and the program was developed.Different from the traditional analytical method,we proposed an algorithm based on ENDF core database,Monte Carlo sampling and SN discretization.The new method consists of temperature correction of nuclear reaction cross section,time-space meshing and sampling,discretization of angle and energy,judgement of particle trace and calculation of nuclear reaction rate.And the new algorithm can also be used to calculate other nuclear reactions in the plasma.