To mitigate this deficiency, a study was made about replacing a certain number of fuel elements in the rack with absorber rods. At first the analysis was done about the number of uniformly mixed absorber rods in the lattice needed to sustain the subcriticality of the storage when pitch is decreased from rack design pitch of 8 cm to contact, assuming that the absorber rods remain in their proper positions. An additional short study of absorber rods made of boron carbide and hafnium, containing the dependence of keff on the thickness of hafnium layer is presented. Next, it is shown that, due to random mixing of the absorber rods during lattice compaction, supercriticality configurations cannot be completely excluded.
Question arises about the probability for such event.
For this purpose, a probabilistic study was made, sampling the probability density functions for random absorber rods lattice loadings.