Study On The Methodology For Sub-criticality Monitoring Of ADS And Numerical Analysis Of Venus 1# Experimental Device

How to measure or monitor the sub-criticality of a subcritical reactor of ADS is a key issue of ADS research. Due to the unique reactor physics characteristics of a subcritical reactor driven by an external neutron source, conventional reactivity measurement methods developed on the base of point reactor model and extensively applied in current critical reactors will be difficult to be directly applied to ADS. In this thesis, starting from the fundamental reactor physics theory, we have illustrated that differing from that of a critical reactor the static neutron flux spatial distribution of a subcritical reactor is determined not only by the eigen-functions of the system but also the eigen-values. Based on this feature, we have proposed a new methodology for subcriticality monitoring via the measuring of in-core neutron flux spatial distribution. The feasibility of the new methodology has been preliminarily demonstrated by numerical tests on IAEA ADS benchmark problem and Chinese Venus 1# experimental device. Comparing against the conventional reactivity measurement methods, the new method has the merits of simplicity, freedom from the impacts of external source fluctuation and high-order harmonics spatial effect as well.In order to cooperate with CIAE to undertake both theoretical and experimental studies of subcritical experimental device Venus 1#, we have numerically analyzed the device by use of MC method. Effective delayed neutron fraction, both experiments on extrapolation criticality assessment and measurement of decay constant of prompt neutron have been analyzed. Based on the numerical results, we have independently studied the experimental data and derived our own result on the subcriticality of the device. The result is much different from the one CIAE obtained, but we consider that our result is more reasonable and consistent.In conclusion, the new subcriticality monitoring methodology we have proposed...