Models for gamma-ray holdup measurements at duct contact

Conference · Tue Jan 01 04:00:00 EST 1991 · Nuclear Materials Management. Annual Meeting Proceedings; (United States)

OSTI ID:5537870

Sheppard, G A; Russo, P A; Wenz, T R; Miller, M C; Piquette, E C ^[1]; Haas, F X; Glick, J B; Garrett, A G ^[2]

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1. Los Alamos National Lab., NM (United States)
2. EG and G Rocky Flats, Inc., Golden, CO (US)

This paper reports that the use of gamma-ray measurements to nondestructively assay special nuclear material holdup in DOE processing facilities has increased recently. A measurement approach that is relatively insensitive to deposit geometry involves withdrawing the detector from the holdup-bearing equipment far enough to validate an assumed point;, line-, or area-source deposit geometry. Because of facility constraints, these generalized geometry procedures are not always followed, and some ducts are measured at contact. Quantitative interpretation of contact measurements requires knowledge of the width of the deposit transverse to the duct axis. Rocky Flats personnel have introduced a method to obtain data from which this width can be deduced. It involves taking measurements in pairs, with the detector viewing the holdup deposit at contact from above and below the duct. The interpretation of the top and bottom measurements to give the deposit width at each location requires a model for the detector's response to radial source position and a model for the deposit geometry. The authors have derived a relationship between the top-to-bottom count rate ratio and the deposit width that approximates the detector response and models the deposit geometry as a uniform strip. The model was validated in controlled experiments that used thin foils of high-enriched uranium metal to simulate deposits.

• OSTI ID: 5537870
• Report Number(s): CONF-910774--
• Conference Information: Journal Name: Nuclear Materials Management. Annual Meeting Proceedings; (United States) Journal Volume: 20
• Country of Publication: United States
• Language: English

Related Subjects

055001* -- Nuclear Fuels-- Safeguards
Inspection
& Accountability-- Technical Aspects
440101 -- Radiation Instrumentation-- General Detectors or Monitors & Radiometric Instruments
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION
ACTINIDES
CHEMICAL ANALYSIS
DEPOSITS
DUCTS
ELECTROMAGNETIC RADIATION
ELEMENTS
ENRICHED URANIUM
FILMS
FOILS
FOULING
GAMMA RADIATION
IONIZING RADIATIONS
ISOTOPE ENRICHED MATERIALS
MATERIALS
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
MEASURING METHODS
METALS
NATIONAL ORGANIZATIONS
NONDESTRUCTIVE ANALYSIS
NUCLEAR FACILITIES
PROCESSING
RADIATION DETECTORS
RADIATIONS
RADIOACTIVE MATERIALS
SIMULATION
THIN FILMS
URANIUM
US DOE
US ORGANIZATIONS