Abstract
These experiments by Oak Ridge National Laboratory (ORNL) at Battelle Northwest Laboratory’s (PNL) critical experiments facility at Hanford, Washington in 1981 used 16 days of critical facility time, not including 10 days for setup and removal of ORNL equipment. These measurements were to assess the capability of the Cf source driven noise close to (CSDNA) method to measure the subcriticality of mixed uranium--plutonium nitrate solutions. In addition to the CSNDA measurements, measurements were also performed near delayed criticality where CSDNA measurements cannot be performed. This report documents the experiments that were not reported at that time by presenting the ORNL experimental results and any on-line analysis that was performed during and shortly after the measurements. The mixed nitrate solution had uranium concentration at 188 grams per liter (g/l), plutonium concentration of 280 g/l, free acid normality of 2.80, hydrogen ion molarity of 5.9 and specific gravity of 1These experiments by Oak Ridge National Laboratory (ORNL) at Battelle Northwest Laboratory’s (PNL) critical experiments facility at Hanford, Washington in 1981 used 16 days of critical facility time, not including 10 days for setup and removal of ORNL equipment. These measurements were to assess the capability of the Cf source driven noise close to (CSDNA) method to measure the subcriticality of mixed uranium--plutonium nitrate solutions. In addition to the CSNDA measurements, measurements were also performed near delayed criticality where CSDNA measurements cannot be performed. This report documents the experiments that were not reported at that time by presenting the ORNL experimental results and any on-line analysis that was performed during and shortly after the measurements. The mixed nitrate solution had uranium concentration at 188 grams per liter (g/l), plutonium concentration of 280 g/l, free acid normality of 2.80, hydrogen ion molarity of 5.9 and specific gravity of 1.754 grams per cm3, 240Pu isotopic content of 7.981 wt. %, and 235U isotopic content of 0.724 wt. %. The stainless-steel tank for the solution had: inside diameter (ID) of 35.38 cm, outside diameter (OD) of 35.53 cm, height of 56.72 cm, and bottom thickness of 0.9525 cm. A Zircalloy pipe with 3.1496 cm OD, 2.7788 cm ID with bottom thickness of 0.635 cm was available for insertion of the Cf source in the center of the fissile solution. The Cf source was also located at the outside surface of the tank (solution height varied from 10 to 53 cm.) and in the center of the solution (solution height varied from 10 to 60.7 cm.). The CSDNA measurements were not analyzed on line to determine the subcritical neutron multiplication factors .At all subcritical states the break frequency noise analysis data was fitted to obtain the prompt neutron decay constant. The neutron multiplication factors were determined for the two configuration of the measurements near delayed criticality without further analysis of the CSDNA measurements to obtain the subcritical neutron multiplication factors, only the near delayed critical, the prompt neutron decay constants obtained, the measured count rates, the measured cross and auto power spectral densities can be benchmarked by direct calculation of the measured data.. Much of data presented in this report are from ORNL notes not in the ORNL logbooks. For the final benchmark analysis the data from the Battelle Northwest Laboratory (who operated the critical facility in 1981) critical facility logbook should be consulted and be incorporated where appropriate. The purpose of this report is to document the experimental information for the measurements performed so that a later date some researcher could perform the required uncertainty and calculational analyses and documentation to use these data for an International Criticality Safety Benchmark Program (ICSBEP) or Nuclear Energy Agency (NEA) benchmark. The data from these measurements is available from the Records Management Services Department of Oak Ridge National Laboratory and the logbook is available from ICSBEP at Idaho National Laboratory.
