Year
1994
Abstract
Continuous monitoring of special nuclear materials' (SNM) attributes in long-term storage areas is a high priority mission at the Department of Energy (DOE) site at the Y-12 Plant in Oak Ridge. New monitoring technologies that will reduce the cost, employee exposures, and effort required to do nuclear material inventories are being evaluated. A small solid-state gamma-ray detection device whose components are estimated to cost less than $15 per unit can be implemented in a variety of configurations and can be adapted to enhance exiting 235U monitoring systems. The silicon photodiode radiation monitor is composed of low-cost, off-the-shelf microcircuits that combine the low-voltage, reversed-bias photon detector with a low-noise preamplifier, a pulse-shaping amplifier, and a discriminator circuit. The discriminator circuits eliminate spurious noise pulses and low-energy gamma-ray pulses. The system can provide useful count rates from background up the 4 Gy/hr radiation levels. Output signals can be locally displayed or cabled to a central data station and analyzed; in addition, each unit could contain a count-rate indicator to facilitate on-site checks and maintenance. The system is small (i.e., 1 cm x 2 cm x 4 cm ), rugged, highly sensitive and low cost. The detector chip costs less than $2 and the detector plus all supporting electronics to produce recordable signals cost less than $15. All detection and electronic components are commercially available.