On-line system to monitor 235U mass in multiple sites for criticality control

For laboratory operations, there has been a trend recently toward the control of nuclear materials for criticality purposes to track the mass of the radionuclides in approved sites. In the past, a blend of geometric, volumetric, and mass controls was used for operations involving moving and transferring nuclear materials from site to site. Migration from using a blend of criticality controls to that of a system that tracks the mass of the radionuclides at each site has resulted in the need for a logbook system. Each site needs a logbook; also, a master logbook is used to track the sum of the nuclear material for all the sites. Updating the master logbook in real time was difficult and time consuming. The logistics of operating with the hardcopy logbook system consumed major resources. The on-line electronic system described in this paper demonstrates how the on-line system can be used to replace the hard-copy logbook system. The program records and calculates the amount of material present at 37 individual sites as well as the total material present in all (the sum) of the sites (sites are defined as work areas, hoods, instruments, safe bottles, rooms, etc.). The program monitors two criticality requirements: (1) The quantity of 235U material at an individual site shall not exceed a conservative preestablished maximum. (2) The total material or sum of all sites shall not exceed a conservative preestablished maximum. As implemented in the program, a warning message is issued if either condition exceeds 90%. Also, the system issues a critical warning if the maximum limit is exceeded. Therefore, 235U limits cannot be exceeded