Abstract
We investigated the effect of β on effective multiplication factor(keff) in the 1/fβ spectrum random system. The random system was generated by the 1/fβ noise model. The model is a continuous space model based on the Randomized Weierstrass function and describes the component spatial distribution with a power spectrum of 1/fβ, where f and β are the frequency domain variable and the characteristic parameter related to randomness, respectively. In this work, the two-group Monte Carlo calculations were performed to obtain the keff for a simple cubic geometry that consisted of two materials (fuel burned to 12 GWd/t and concrete). A large number of replicas having different spatial distribution and characterized by the representative β values were generated using the model, and the distribution on keff was analyzed. We found the dependency on β of standard deviation, skewness, and kurtosis of keff distribution. This result is expected to help to predict the keff distribution due to the randomizing model.
Highlights
The criticality control of the fuel debris is significant for decommissioning of the Fukushima Daiichi Nuclear Power Plant
It is important to obtain information about an inside of the fuel debris such as the composition that is a set of average values of material concentration including fuel, and the component spatial distribution that is the local variation of the concentration
The distributions of the keff values were analyzed from the view point of standard deviation, skewness, and kurtosis to capture the features of the keff distributions
Summary
The inside of the fuel debris is not known and expected to be non-uniform Under this situation, the systematic computational investigations of the effect of the composition on the criticality have been conducted by using the simplified model consisting of a fuel sphere and a moderator shell as a conservative model of the component spatial distribution [1,2,3]. Depending on the β value, the model generates the component spatial distribution which has different characteristics. The investigation of the effect of β on the keff is helpful to understand the effect of the component spatial distribution on the keff This knowledge is expected to be useful for the criticality control. The distributions of the keff values were analyzed from the view point of standard deviation, skewness, and kurtosis to capture the features of the keff distributions
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