Physics Calculation Model Based On Monte Carlo Method And Characteristics Analysis Of Aqueous Homogeneous Reactors

AHRs (Aqueous Homogeneous Reactors), which use fissile nuclides' dissolublesalt's water solution as fuel, have many different characteristics compared with solidfuel reactors. Producing medical isotopes by AHRs has better safety, economy andextracting convenience than by traditional methods in solid fuel reactors. However,radiolytic gas bubbles' exist may limit AHRs' power density, which becomes the mainobstacle in transitioning this technology from research to a commercial industrialenvironment.Simulation of gas bubbles' behavior is especially important for AHRs' calculation,the small size and un-repeatable complex geometry requires a stronger geometrytreatment ability of AHRs' calculation model. Computational Fluid Dynamics method(CFD), along with Multiple Size Group model, and the consideration of bubbles'breakup and coalescence, is used to simulate the two-phase behavior of AHRs. Guidedby gas bubbles' dynamic behavior studied from the results, gas bubbles' model of AHRs,which considers bubbles' movement, is established. Based on the one-step computingtheory, using Monte Carlo method as the transport calculation module, the staticcalculation model of AHRs is established, which contains resonance treatment, burn-upcalculation, critical rod height searching, thermal-hydraulic model and gas bubbles'model. In order to achieve high efficiency and accuracy, improved quasi-staticapproximation method is applied in the transient calculation model. Aiming atintroducing Monte Carlo method into this approximation, a new method of usingiterated fission probability to replace the adjoint flux, and then using it as the weightfunction to compute neutron kinetics parameters, is investigated and carried out inMonte Carlo codes. Also, the sampling mechanism of source neutrons is modified foradding the function of solving fixed-source problems in Multi-group Monte Carlo codeMCMG. Together with the introduction of transient temperature and gas bubbles' model,the integrated transient calculation model of AHRs is established.According to the calculation model, FMCAHR (Fuel Management Code ofAqueous Homogeneous Reactors) and TCCAHR (Transient Calculation Code ofAqueous Homogeneous Reactors) is developed, verification results show that, theresults of gas bubbles' model match well with the simulation results of CFD method, calculation results of FMCAHR and TCCAHR keep good consistency with benchmarksand AHRs' experimental measurement results, the one-step calculation model is simpleand has little approximation. Physics characteristics of AHRs are analyzed usingFMCAHR and TCCAHR, the results show that, gas bubbles are the main issue thatinfluences the transient behavior and brings out the inherent safety of AHRs. As long asthe heat transfer ability is ensured, the power density of AHRs could reach2kW/L.This thesis establishes AHR's gas bubbles' model that takes into account ofbubbles' movement, constructs a one-step calculation model based on Monte Carlomethod, and provides a new implement for the calculation and analysis of AHRs.Preliminary characteristics of AHRs are investigated; the big effect of gas bubbles toAHRs' transient behavior is validated.