Criticality of heterogeneous lattices of Experimental Beryllium Oxide Reactor fuel pins in water and in aqueous solutions containing boron and uranyl nitrate

The fuel intended for the Experimental Beryllium Oxide Reactor was made available for a series of critical experiments at the Oak Ridge Critical Experiments Facility. The fuel pins consisted of compressed ceramic pellets contained in Hastelloy X-280 tubes. The pellets were a homogeneous mixture of U(62.4)O2 and BeO. The data generated are applicable to support the establishment of specifications for the chemical recovery of uranium in a process in which boron as a soluble neutron absorber is a part of the dissolver solution. It was found that a boron concentration of about 0.3 g/liter in a dilute solution of uranyl nitrate (approximately 3.7 g of 235U/liter) increased the critical mass 60 percent over that without boron