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PNC TN9450 91-009, 127 Pages, 1991/11
Effective neutron multiplication factors of subcritical assemblies, which will be applied to the experiments of subcriticality measurement, are estimated and summarized. Subcritical assemblies investigated here are supposed to be loaded in the subcriticality experiment system: The subcritical experiment system will be constructed by changing the core structure of Deuterium Critical Assembly, and the geometrical dimensions of investigated assemblies were selected so as the assemblies can be loaded to the experiment system. Subcriticalities or effective multiplication factors of cylindrical, slab and annular assemblies by using ATR fuel pins, FBR fuel pins or liquid uranium fuel were evaluated. The assemblies studied here have rather high multiplication factors, and the assemblies with lower multiplication factors should be added as future problem. It has been proved that the subcritical assemblies with desirable multiplication factors can be formed by the fuels mentioned above.
Aihara, Nagafumi; ;
PNC TN9410 91-135, 121 Pages, 1991/04
An analysis of nuclear characteristic of a driver region core has been performed in order to contribute for the experimental plan of criticality safety using Deuterium Critical Assembly (DCA). The driver region core is composed of two parts by the inner void region and outer driver region loaded with fuel clusters in the DCA core. The analysis was carried out by use of the coupled WIMS-ATR/TWOTRAN code system. From the present analysis, we could understand the effect of nuclear characteristic due to the parameter change of lattice pitch distance, coolant material, void region diameter, fuel loading pattern and so on for the driver region core. The items of nuclear characteristic obtained by the present analysis are effective multiplication factor, critical heavy water level, critical 
B concentration, control rod reactivity worth and so on. Furthermore, the analysis of nuclear characteristic of two region core, which is composed of test region including fuel material in the void region and driver region, will be performed as the near future work.
