Combined Assay Systems for the Characterisation of Historical ILW at of the Dounreay Shaft and Silo-18140

Conference · Sun Jul 01 00:00:00 EDT 2018

OSTI ID:22975331

Bourva, L.; Wilkins, C.; Chard, P. M.J.; Singh, J. ^[1]; Young, P.; Gunn, R.; McIntosh, C. ^[2]

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1. Mirion Technologies Canberra UK Ltd, Harwell Oxford, Building 528.10 Unit 1, Didcot, OX11 0DF (United Kingdom)
2. Dounreay Site Restoration Ltd, D2003, Zone 6, Dounreay, Thurso, Caithness, KW14 7TZ (United Kingdom)

In 1955 the Dounreay nuclear power development establishment was created on the northern coast of Scotland primarily to pursue the UK Government policy of developing Fast Breeder Reactor (FBR) technology. The site operated then by the United Kingdom Atomic Energy Authority (UKAEA) saw the development, test and operation of 3 nuclear reactors, two of them FBRs, alongside fabrication and reprocessing facilities for the FBR fuel elements. From the late 1950's until 1977 Intermediate Level radioactive Waste (ILW) generated on site was disposed of into a 65 m deep, 4.6 m diameter shaft. In January 1977, an explosion thought to be caused by hydrogen generated from sodium and potassium wastes reacting with water occurred in the upper part of the shaft, thus stopping any further waste disposal. A second ILW storage facility, the ILW-Silo, started operation in 1971 to deal with the increasing volume of intermediate level waste generated on site in the mid-1960's and continued receiving waste until 1998. The decommissioning of the Shaft and Silo facilities is a challenging engineering task due to the complexity and potential hazards linked with the retrieval and handling of historical waste. Following recovery it is intended to shred the majority of the waste and load it into 200-l assay drums. Sludges would be separated and solidified within a special annulus drum to make them suitable for assay. To support the decommissioning strategies put forward by Dounreay Site Restoration Limited (DSRL), Mirion Technologies Canberra UK Ltd have designed and completed the manufacture of a pair of combined non-destructive waste assay (NDA) systems. The two identical automated ILW counters are intended to provide a means to characterise the waste materials by performing active and passive neutron measurement as well as segmented high resolution gamma spectrometry (HRGS) of 200-l sacrificial waste drums. The active neutron technique is based on the Differential Die Away (DDA) technique using a pulsed Deuterium-Tritium neutron generator to interrogate fissile material present in the waste. The active neutron measurements support, as well as the passive neutron coincidence measurements, a matrix correction capability by use of an Add-a-Source mechanism. The publication will describe in broad lines the approach proposed by DSRL in the processing of the waste retrieved from both the Shaft and Silo facilities. It will also present a description of the overall design of the NDA counters, illustrating how the measurements to be performed will allow DSRL to safely characterise the retrieved waste materials. (authors)

• Research Organization: WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
• OSTI ID: 22975331
• Report Number(s): INIS-US-20-WM-18140; TRN: US21V0144015373
• Resource Relation: Conference: WM2018: 44. Annual Waste Management Conference, Phoenix, AZ (United States), 18-22 Mar 2018; Other Information: Country of input: France; 7 refs.; Available online at: https://www.xcdsystem.com/wmsym/2018/index.html
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
COINCIDENCE METHODS
DECOMMISSIONING
DEUTERIUM
DFR REACTOR
GAMMA SPECTROSCOPY
INTERMEDIATE-LEVEL RADIOACTIVE WASTES
NEUTRON GENERATORS
NONDESTRUCTIVE ANALYSIS
RADIATION HAZARDS
RADIOACTIVE WASTE DISPOSAL
RADIOACTIVE WASTE STORAGE
RADIOASSAY
SLUDGES
SOLIDIFICATION
TRITIUM
UKAEA
UNITED KINGDOM