Computer Simulation Study Of The Beam Transient Dynamic Response Of Accelerator-driven Subcritical System (ads)

The development and commercial application in large scale of fission energy have respectively 50 and 25-year-long history. Although people wish that the application of nuclear fusion energy could ultimately solve human energy problem, the 40-year-long research & development process of nuclear fusion and current situation show that it is still a quite long course, since the application of nuclear fusion energy must undergo principle test, project development, project demonstration and commercial demonstration. Therefore, the using of nuclear fission energy will still play an important role in a long period till the middle of 21 century.Some shortcomings such as the ultimately dispose of high level radioactive waste, low use rate of uranium resource and safety issues exist in current commercial application of nuclear system, which hinder the further development of fission energy. In recent about ten years the nuclear science world is seeking a new technology route — Accelerator Driven Subcritical system (abbreviation, ADS), which can overcome the above mentioned obstacles. Our country has placed this research in the National Important Basis Research Project — '973' plan. This mixed system, which consists of high energy proton accelerator and subcritical reactor, will be a transition between the current nuclear system and the complete application of fusion energy.The subcritical reactor in ADS works on high power level, and the fission thermal power density is comparable to that of nuclear power plant of same type, so the safety related design principles are similar to those of the reactor core in current nuclear power plants.Because the maintain of power level in ADS relys on the neutron source generated through intensive proton beam hitting spallation target, the instability of proton beam as well as trips in any form will influence the reactor power level and further the safety of ADS. Therefore, the reliabilityof High Power Proton Accelerator (HPPA) determines the security of ADS.In ADS, the stability and trip of HPPA are named together as the reliability of HPPA. The trip here means that in ADS a certain reason results in the interrupt of proton beam or disappearance in beam duct.The main reason of trip phenomena exists in accidents of ion source and radio frequency,, The ion source accident results mainly from high-tension ignition, and the time of trip is usually less than one second and can automatic resume. The trip brought by radio frequency failure lasts longer than five minutes and man muss intervene.The trip of HPPA influences subcritical reactor in two aspects: 1) the change of power resulted from neutrons behavior in reactor; 2)the change of material temperature resulted from abrupt power change will bring about thermal stress and structural components fatigue & squirm change further influence lifetimes,.Currently, the research of trip problem is becoming international a hot issue in ADS research. Concerning how to appraise the influence of external neutron source transient change in the engineering design and safety analysis of ADS, many research institutions in development countries such as ENEA CasacciaQtalyh SCK CEN Mol (Belgium), JAERI Tokai (Japan), Royal Institute of Technology, Stockholm(Sweden)^ FZK Karlsruhe(Germany) and so on, adopt computer simulation technology, establish correspond calculation models, develop related professional simulation software such as TIESTE-MINOSSE^ SITHER-PKS EXCURS-M, SASSYS/SAS4A, SIM-ADS and so on. They set up Benchmark and carry through international compare and discuss.,In our country currently there is no simulation software, which specially serves the research of transient change of accelerator proton beam in ADS. It is urgent to develop a set of software dedicated to ADS trip research. According to the demand of the research plan of "973" project, the domesticand abroad research situation of beam transient change accident in ADS is extensively studied in this paper. Through general simulation platform and modern computer technology, simulation software - SIMULINK-ADS dedicating to ADS beam transient change accident is designed and developed.Main research tasks as follows:U According to the requirements of ADS design and simulation, the physical and mathematical simulation models of beam intensity of HPPA and sub-criticality of sub-critical reactor, which can be used for the simulation research of ADS principles, models of ADS subcritical reactor core driven with external source, reasonable thermal models, the transfer function of subcritical reactor and thermal system are established. 2n By use of the simulation tool package SIMULINK in general simulation software Matlab6. 1, all the physical mathematical models are modularized and a simulation software SIMULINK-ADS based on general micro-computer is independently developed , which can simulate the whole process of ADS accelerator beam transient change accident.3n By use of SIMULINK-ADS, the beam transient change in ADS with different sub-criticality is simulated. Through continual debugging and modification, simulation results are obtained and recorded, which tally satisfying with the results of abroad research institutions.