Nuclear criticality neutron-absorbing poisons

Experimental criticality data are needed for soluble neutron absorbers (poisons) to accurately determine their effectiveness in the criticality prevention and control of solutions bearing fissile material. These data are needed to validate, criticality control calculational techniques that are used in the analysis of poismwd systems. This paper summarizes the results of a series of experiments performed at the Battelle-Pacific Northwest Critical Mass Laboratory, on water-flooded uranium rod lattices which vere poisoned with soluble neutron absorbers. The poisons utilized, B, Cd, and Gd, were chosen due to their large neutron-absorption cross sections. The exqxerlments were oriented toward providing data on the effectiveness of these materials as soluble absorbers for use in nuclear criticality prevention. Data on integral critical exq >eriments are provided against which calculational techniques can be checked. 

Many factors influence both the decision to use soluble poisons and the selection of a particular neutron absorber. These foctors can be broadly categorized as technical and philosophical requirements. Technical requirements include physical, chemical, and nuclear properties of the poisoned systems philos(q>hical requirements include remote operations, process flexibility, contingency foctors, and other options available for criticality control. 

---