CONCEPTUAL DESIGN OF THE SPECIAL NUCLEAR MATERIAL NONDESTRUCTIVE ASSAY AND ACCOUNTABILITY SYSTEM FOR THE HTGR FUEL REFABRICATION PILOT PLANT

摘要

The conceptual design of the fissile material assay and accountability system for the HTGR refabrication pilot plant has been established. The primary feature affecting the design is the high, time varying, gamma activity of the process mate¬rial due to the unavoidable presence of uranium-232. This imposes stringent requirements for remote operation and remote maintainability of system components. At the same time, the remote operation lends itself to implementation of an automated data collection and processing system for real-time accounta¬bility. The high time-varying gamma activity of the material also precludes application of a number of techniques presently employed for light-water reactor fuel assay. The techniques selected for application in the refabrication facility aren(1) active thermal neutron interrogation with fast-fission or delayed-neutron counting for fuel-rod and small-sample assay,n(2) calorimetry for high-level waste assay, and (3) passive gamma scanning for low-level waste assay, and rapid on-line relative rod-loading measurements. The principal nondestruc¬tive assay subsystems are identified as (1) on-line devices for 100% product fuel rod assay and quality control, (2) a multipurpose device in the sample inspection laboratory for small-sample assay and secondary standards calibration, andn(3) equipment for assay of high- and low-uranium content scrap and waste materials. A data processing system, which coordinates data from these subsystems with information from other process control sensors, is included to provide real¬-time material balance information.