Year
2005
Abstract
Current International Atomic Energy Agency (IAEA) policy considers any purified aqueous uranium solution or any purified uranium oxides to be nuclear material of a composition and purity suitable for isotopic enrichment or fuel fabrication, respectively. The U.S. Department of Energy (DOE) is developing instruments, tools, strategies, and methods that could be of use to the IAEA in the application of safeguards for materials found in the front end of the nuclear fuel cycle prior to the production of uranium hexafluoride or oxides that have been the traditional starting points of IAEA safeguards. One such material is purified uranyl nitrate solution produced in plants that convert ore concentrates to uranium hexafluoride via aqueous processes. Through its laboratories DOE is developing a system for unattended monitoring of the uranium content of purified uranyl nitrate solution produced in a natural uranium conversion plant (NUCP). The process monitoring system has three essential elements: a flow meter that measures the solution volume or mass flow; a neutron-based system to measure the uranium concentration of the solution; and a surveillance system that would detect tampering, attempts to bypass the monitoring system, or activities that might indicate undeclared production. The time-integrated product of incremental volume or mass flows and the concentrations gives the uranium content of the purified process material produced in the NUCP and can be compared with the uranium content of the declared plant products, e.g., uranium hexafluoride, oxide and/or metal. The monitoring system has been assembled and is being tested with uranium-containing solutions at ORNL. Further testing is planned to evaluate performance under processing conditions in an operating fuel-cycle facility. Progress in this multi-laboratory program, including the ongoing testing program, the concept for integration of unattended process-monitoring instrumentation at a NUCP operating under IAEA safeguards, and systems modeling concept, will be presented.