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Significance and Use
Segmented gamma-ray scanning provides a nondestructive means of measuring the nuclide content of scrap and waste where the specific nature of the matrix and the chemical form and relationship between the nuclide and matrix may be unknown.
The procedure can serve as a diagnostic tool that provides a vertical profile of transmission and nuclide concentration within the item.
Item preparation is generally limited to good waste/scrap segregation practices that produce relatively homogeneous items that are required for any successful waste/inventory management and assay scheme, regardless of the measurement method used. Also, process knowledge should be used, when available, as part of a waste management program to complement information on item parameters, container properties, and the appropriateness of calibration factors.
To obtain the lowest detection levels, a two-pass assay should be used. The two-pass assay also reduces problems related to potential interferences between transmission peaks and assay peaks. For items with higher activities, a single-pass assay may be used to increase throughput.
1.1 This test method covers the transmission-corrected nondestructive assay (NDA) of gamma-ray emitting special nuclear materials (SNMs), most commonly 235U, 239Pu, and 241Am, in low-density scrap or waste, packaged in cylindrical containers. The method can also be applied to NDA of other gamma-emitting nuclides including fission products. High-resolution gamma-ray spectroscopy is used to detect and measure the nuclides of interest and to measure and correct for gamma-ray attenuation in a series of horizontal segments (collimated gamma detector views) of the container. Corrections are also made for counting losses occasioned by signal processing limitations (1-3).
1.2 There are currently several systems in use or under development for determining the attenuation corrections for NDA of radioisotopic materials (4-8). A related technique, tomographic gamma-ray scanning (TGS), is not included in this test method (9, 10, 11).
1.2.1 This test method will cover two implementations of the Segmented Gamma Scanning (SGS) procedure: (1) Isotope Specific (Mass) Calibration, the original SGS procedure, uses standards of known radionuclide masses to determine detector response in a mass versus corrected count rate calibration that applies only to those specific radionuclides for which it is calibrated, and (2) Efficiency Curve Calibration, an alternative method, typically uses non-SNM radionuclide sources to determine system detection efficiency vs. gamma energy and thereby calibrate for all gamma-emitting radionuclides of interest (12).
18.104.22.168 Efficiency Curve Calibration, over the energy range for which the efficiency is defined, has the advantage of providing calibration for many gamma-emitting nuclides for which half-life and gamma emission intensity data are available.
1.3 The assay technique may be applicable to loadings up to several hundred grams of nuclide in a 208-L [55-gal] drum, with more restricted ranges to be applicable depending on specific packaging and counting equipment considerations.
1.4 Measured transmission values must be available for use in calculation of segment-specific attenuation corrections at the energies of analysis.
1.5 A related method, SGS with calculated correction factors based on item content and density, is not included in this standard.
1.6 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 10.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
C1030 Test Method for Determination of Plutonium Isotopic Composition by Gamma-Ray Spectrometry
C1128 Guide for Preparation of Working Reference Materials for Use in Analysis of Nuclear Fuel Cycle Materials
C1156 Guide for Establishing Calibration for a Measurement Method Used to Analyze Nuclear Fuel Cycle Materials
C1207 Test Method for Nondestructive Assay of Plutonium in Scrap and Waste by Passive Neutron Coincidence Counting
C1210 Guide for Establishing a Measurement System Quality Control Program for Analytical Chemistry Laboratories Within the Nuclear Industry
C1215 Guide for Preparing and Interpreting Precision and Bias Statements in Test Method Standards Used in the Nuclear Industry
C1316 Test Method for Nondestructive Assay of Nuclear Material in Scrap and Waste by Passive-Active Neutron Counting Using 252Cf Shuffler
C1458 Test Method for Nondestructive Assay of Plutonium, Tritium and 241Am by Calorimetric Assay
C1490 Guide for the Selection, Training and Qualification of Nondestructive Assay (NDA) Personnel
C1592 Guide for Nondestructive Assay Measurements
C1673 Terminology of C26.10 Nondestructive Assay Methods
E181 Test Methods for Detector Calibration and Analysis of Radionuclides
ICS Number Code 13.030.30 (Special wastes); 71.040.50 (Physicochemical methods of analysis)
UNSPSC Code 15131500(Nuclear fuel); 41111812(Gamma ray radiography examination equipment)