Reactivity Effect Measurement of Neutron Interaction between Two Slab Cores Containing 10% Enriched Uranyl Nitrate Solution without Neutron Isolator

Abstract

The reactivity effect of neutron interaction between two identical units containing low enriched (10% 235 U enrichment) uranyl nitrate solution without neutron isolator was measured in the STACY. The unit has 350 mm of thickness and 690 mm of width and distance between those two units was adjustable from 0 to 1,450 mm. Condition of the solution was about 290 gU/l in uranium concentration, about 0.8 N in free nitric acidity, 24-27• C in temperature and about 1.4 g/cm 3 in solution density. The reactivity effect was estimated from variation of critical solution level from 495 to 763 mm depending on the core distance. The reactivity effect was also evaluated by the solid angle method and a computational method using the continuous energy Monte Carlo code MCNP-4C and the nuclear data library JENDL 3.2. Those estimations were compared and the distance to isolate neutron interaction was overestimated by the solid angle method. The computational method considering neutron reflection from surrounding structures reproduced well the isolation distance given by the experiment.

Quantifying the Correlation between the Neutron Multiplication Factor and the Spatial Arrangement of Spent Fuel Casks in a Spent Fuel Storage Facility

“…The contributory factors which make the keff of the zigzag storage matrix to be lower than the others include the fact that each individual cask on either row is at an angle with respect to its counterpart on the other row of casks which affects the solid angle as the number of neutrons emanating one particular casks in a given row with a requite energy reaching the other cask on the opposite row is affected by the angular position of the casks with respect to one another, which has an effect on the neutron flux. The reactivity effects of the interaction neutrons between two containers have also been quantified by Kotaro Tonoike et al (2012) [15] where it was discovered that if a single unit containing fissile material is located near a similar unit with the same shape and both contain fissile material, then the relationship between the change in reactivity and the solid angle (Ω) (cf Eqn. 26 to Eqn.…”

“…, where M 2 is the neutron migration area, B 2 is the geometric buckling of a single unit and Ω is the solid angle between the units [15].…”