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In this research, the hydrodynamic behavior of two laterally interconnected channels with blockages in one of them has been studied experimentally. For blockages of different shapes and severities, the mass flow rates as well as the pressures in the channels upstream and downstream of the blockage were determined. The experiments were conducted on two square channels separated by an intermediate plate with slots of different geometric parameters. Two types of blockages have been considered: plate and smooth. The shape of the smooth blockage was a cosine. The experimental data on the mass flow rates and pressures in the channels have been compared with the predictions of the subchannel code COBRA-III-C. It is observed that COBRA-III-C may not be adequate to describe the hydrodynamic behavior of two-interconnected channels with plate type blockages much higher than 30 percent severity in one of the channels. The limit of applicability of the code in the case of smooth blockages can be safely extended up to 60 percent severity.

The 235U/238U ratio is determined by neutron activation analysis counting the y-rays of short half-lives fission products and 239U. The effect of the neutron spectrum hardening using a 6LiD converter is also demonstrated. The 235U/23~U ratio is determined using short irradiation, waiting and counting times.