The Critical Safety Analysis For The Spent Nuclear Fuel Storage System Of The10MWt Thorium Molten Salt Reactor With Solid Fuel

The molten salt reactor (MSR) was chosen as one candidate of the six advanced nuclearenergy system by Generation IV International Forum (GIF). Thorium Molten Salt Reactor(TMSR) project was lunched by Chinese Academy of Science (CAS) as-Adavance NuclearFission Energy in the strategic priority research programs. Design and construction of theThorium Molten Salt Reactor-Solid Fuel (TMSR-SF) is part of the special task. As molten salt isused as TMSR-SF primary coolant, molten salt may be attached to the spent fuel element surface,therefore, it is necessary to analyze the effect of attached molten salt on the nuclear criticalitysafety for the spent fuel storage. In this paper, The critical safety analysis was carried out for thespent nuclear fuel storage system of the10MWt Thorium Molten Salt Reactor with Solid Fuel(TMSR-SF1). The critical safety calculation based on burnup credit application was adopted bycomparing its advantages to the traditional critical safety calculation method.. The critical safetyanalysis then was carried out both under normal condition and abnormal condition. The effect ofthe attached molten salt on the nuclear criticality safety were mainly considered. The resultsshow that regardless of whether the molten salt attached, the TMSR-SF1spent fuel storagesystem is always in the subcritical, The main chapters are as followings:Chapter1: An overview of the history and development status of molten salt reactors and ofcriticality safety analysis for storage spent nuclear fuel was given first, followed by the purposeand significance of this research.Chapter2: Criticality safety and its effect factors, and the criticality safety calculationmethod were introduced. The deterministic method, stochastic method and computer codesdeveloped on basis of them. Were focused.Chapter3:The spent nuclear fuel storage system of TMSR-SF1and the TRISO pebble asfuel were described with fuel element structural parameters and the function of each part. Thespent nuclear fuel storage canister design principles/design requirements/experimentalverification method were also added.Chapter4: According to the reactor core parameters of the TMSR-SF1, burnup calculationwas carried out with core modeling, then combined with the “actinide+fission product” level inburnup credit application to choose reactivity worth nuclides, and then get the analysis results.Chapter5: According to the parameters of the spent nuclear fuel storage system, criticalsafety analysis was carried out by MCNP5code both in normal condition and abnormal condition First， comparisons of the critical safety calculations based on burnup creditapplication to the traditional one were given for the single strogae canister case under normalcondition. The result shows the former is lower than the latter, it means the former have a biggersafety margin than the latter under the same load condition; then, the effect of the attachedmolten salt on the critical safety was evaluated with considering two typical modes, one is themolten salt infiltrate the fuel element and the other is the surfaces coated. The results shows theformer’s effect on the reactivity is bigger than the latter. The storage system flooded wasconsidered as a typical abnormal condition. The effects of different water density and water layerthickness on the reactivity were anlyszed for the storage systems. The results showed that thereactivity slightly changed with the water density, while the reactivity increases with the waterlayer thickness, and finally to be stable.. The critical safety analysis shows that the storagesystem is in subcritical reactivity both in normal condition and abnormal conditions, it is that, thestorage system is critical safe..Chapter6: Summary and prospect. The achievements and the insufficient of the presentwork were summarized, and the possible improvements were prospected.