APPLICATIONS OF THE TRU-D PORTABLE PACKAGE MONITOR FOR RAPID GRAM ESTIMATION OF PLUTONIUM BEARING WASTE PACKAGES AT THE POINT OF ORIGIN

摘要

BNFL Instruments'TRU-D Portable Package monitor(PPM)was developed in response to a market need for a simple,highly maneuverable,accurate,reliable and inexpensive packet monitor.The instrument plays a major role at nuclear sites in performing a wide variety of plutonium measurement tasks,but is primarily being used as a portable instrument for criticality safety measurements of the fissile content of waste packages at the point of origin. Traditional packet monitoring methods used in operations and decommissioning have relied on methods such as gross gamma counting,which are subject to considerable variation,due to differences in the attenuation properties of waste matrix and source.The TRU-D Portable Package Monitor uses the total neutron counting method,which is far less sensitive to such biases.The system has been designed for rapid set-up and simple push button operation and can accept packages up to 30 cm in diameter and 50 cm in length with a maximum weight of 25 kg.The minimum detectable activity(MDA)is of the order of 0.1-1g Pu for a 10 minute measurement.Total measurement uncertainty(TMU)is typically less than+/- 40%at the 95%confidence level. Three applications are described in this paper,which demonstrate the versatility of this instrument.At nuclear sites in the United Kingdom,more than a dozen PPMs have been deployed in various waste management applications including provision of a“Threshold”indication of Pu content for criticality safety control.In the USA at the Rocky Flats Environmental Technology Site(RFETS)a PPM is in use, also for criticality safety controls,for cumulative waste container loading estimates.The qualification work at RFETS established a PPM upper range limit of 500g for Weapons Grade(WG)Pu Oxide.In the third application,Advanced Mixed Waste Treatment Plant(AMWTP)in Idaho,the instrument was upgraded with gamma spectroscopy to provide sensitivity to fissile uranium isotopes as well as plutonium.This system has been built to meet AMWTP’s needs for fissile content tracking and control of material entering or leaving the Special Case Waste(SCW)gloveboxes.