Application of Neutron Multiplicity Counting to Waste Assay

Application of Neutron Multiplicity Counting to Waste Assay
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Total Pages: 17
Release: 1997
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ISBN:

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This paper describes the use of a new figure of merit code that calculates both bias and precision for coincidence and multiplicity counting, and determines the optimum regions for each in waste assay applications. A tunable multiplicity approach is developed that uses a combination of coincidence and multiplicity counting to minimize the total assay error. An example is shown where multiplicity analysis is used to solve for mass, alpha, and multiplication and tunable multiplicity is shown to work well. The approach provides a method for selecting coincidence, multiplicity, or tunable multiplicity counting to give the best assay with the lowest total error over a broad spectrum of assay conditions.

Expected Precision of Neutron Multiplicity Measurements of Waste Drums

Expected Precision of Neutron Multiplicity Measurements of Waste Drums
Author:
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Total Pages: 10
Release: 1995
Genre:
ISBN:

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DOE facilities are beginning to apply passive neutron multiplicity counting techniques to the assay of plutonium scrap and residues. There is also considerable interest in applying this new measurement technique to 208-liter waste drums. The additional information available from multiplicity counting could flag the presence of shielding materials or improve assay accuracy by correcting for matrix effects such as ([alpha], n) induced fission or detector efficiency variations. The potential for multiplicity analysis of waste drums, and the importance of better detector design, can be estimated by calculating the expected assay precision using a Figure of Merit code for assay variance. This paper reports results obtained as a function of waste drum content and detector characteristics. We find that multiplicity analysis of waste drums is feasible if a high-efficiency neutron counter is used. However, results are significantly poorer if the multiplicity analysis must be used to solve for detection efficiency.

Nondestructive Assay Tests of High-efficiency Neutron Counter (HENC) for Waste Assay and Possible Diversion Scenario

Nondestructive Assay Tests of High-efficiency Neutron Counter (HENC) for Waste Assay and Possible Diversion Scenario
Author:
Publisher:
Total Pages: 35
Release: 1998
Genre:
ISBN:

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An advanced passive neutron counter, the high-efficiency neutron counter (HENC), has been used to measure plutonium content in 200-L waste drums. The HENC was designed with the 252Cf add-a-source (AS) feature to improve accuracy over a wide range of waste matrix materials. The current implementation allows for passive neutron coincidence counting, AS analysis, and multiplicity analysis. Passive neutron assay of typical waste containers is intrinsically more accurate than active neutron techniques because of the penetrability of the spontaneous fission neutrons originating from within the waste matrix. In addition, the HENC is designed as a slightly undermoderated detector to be less sensitive to low loading of hydrogen-bearing matrices. The following paper considers the applicability of three different nondestructive assay methods for analysis of waste drums and the flagging of possible diversions in waste drums. The 252Cf AS method, multiplicity counting, and a bounded-parameter multiplicity analysis are presented with areas of applicability.

The Application of Neutron Multiplicity Counting to the Assay of Bulk Plutonium Bearing Materials at RFETS and LLNL.

The Application of Neutron Multiplicity Counting to the Assay of Bulk Plutonium Bearing Materials at RFETS and LLNL.
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Publisher:
Total Pages: 8
Release: 1995
Genre:
ISBN:

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In the past several years, several facilities have identified a need for a large multiplicity counter to support safeguards of excess weapons materials and the measurement control and accountability of large, unusual samples. The authors have designed and fabricated two large thermal neutron multiplicity counters to meet this need at two DOE facilities. The first of these counters was built for Rocky Flats Environmental Test Site for use in the initial inventory inspection of excess weapons plutonium offered to International Atomic Energy Agency safeguards. The second counter was built for the Lawrence Livermore National Laboratory (LLNL) to support their material control and accountability program. For the LLNL version of the counter, a removable, fast-neutron interrogation assembly was added for the measurement of large uranium samples. In the passive mode these counters can accommodate samples in containers as large as a 30-gal. drum. This paper reports on the measured performance of these two counters and the data obtained with them.

Application Guide to Neutron Multiplicity Counting

Application Guide to Neutron Multiplicity Counting
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Total Pages:
Release: 1998
Genre:
ISBN:

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This document is intended to serve as a comprehensive applications guide to passive neutron multiplicity counting, a new nondestructive assay (NDA) technique developed over the past ten years. The document describes the principles of multiplicity counter design, electronics, and mathematics. Existing counters in Department of Energy (DOE) facilities are surveyed, and their operating requirements and procedures and defined. Current applications to plutonium material types found in DOE facilities are described, and estimates of the expected assay precision and bias are given. Lastly, guidelines for multiplicity counter selection and procurement are summarized. The document also includes a detailed collection of references on passive neutron coincidence and multiplicity publications over the last ten to fifteen years.

Development of a High-efficiency Neutron Counter Using Novel Materials

Development of a High-efficiency Neutron Counter Using Novel Materials
Author:
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Total Pages: 16
Release: 1997
Genre:
ISBN:

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Neutron detection efficiency is an important figure of merit for waste assay applications that must measure small quantities of material. It is also important for neutron coincidence counting and multiplicity counting because the detection of double- and triple-correlated events scales as the detection efficiency squared and cubed, respectively. Conventional thermal neutron detection systems typically employ 3He detector tubes embedded in polyethylene. The polyethylene moderates the neutrons so they can be detected by the 3He tubes. However, the hydrogen in the moderator also absorbs neutrons and reduces the diffusion length. We have extensively explored alternate designs that use both polyethylene and other industrial plastics with lower concentrations of hydrogen. In MCNP studies, we have achieved higher detection efficiency by using both polyethylene and other plastics in a hybrid design. In this paper we will present the design of a nominal 30%-efficient, 200-liter neutron counter that uses a hybrid design. We will show comparison results of this design compared to a standard polyethylene design. Finally, this counter has been constructed and tested, and was used in the Los Alamos waste assay course. We will show comparisons of the experimental results from this counter to the MCNP predictions.

Recent Experiences of Scrap and Waste Assay Using Neutron Coincidence Counting of Materials from F B-Line at the Savannah River Site

Recent Experiences of Scrap and Waste Assay Using Neutron Coincidence Counting of Materials from F B-Line at the Savannah River Site
Author:
Publisher:
Total Pages: 8
Release: 1990
Genre:
ISBN:

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The heterogeneous nature of scrap and waste poses unique problems for quantitative measurement. This is particularly true when the sample to be measured can have significant amounts of plutonium in addition to a variety of matrix components. One approach to addressing these difficulties is to combine gamma-ray and neutron counting techniques. A system combining a segmented gamma-ray scanner and neutron coincidence counter has recently been developed for the non-destructive assay of plutonium-bearing scrap and waste. Experience gained with the neutron coincidence counter portion of the system is described. Results obtained from the measurement of scrap and waste materials containing a few grams to a few hundred grams of plutonium are given. The effects of different matrices are evaluated and the role of special diagnostics is explored. 5 refs., 13 figs., 3 tabs.

Handbook of Radioactivity Analysis

Handbook of Radioactivity Analysis
Author: Michael F. L'Annunziata
Publisher: Academic Press
Total Pages: 1076
Release: 2020-03-07
Genre: Science
ISBN: 0128143967

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Handbook of Radioactivity Analysis: Radiation Physics and Detectors, Volume One, and Radioanalytical Applications, Volume Two, Fourth Edition, constitute an authoritative reference on the principles, practical techniques and procedures for the accurate measurement of radioactivity - everything from the very low levels encountered in the environment, to higher levels measured in radioisotope research, clinical laboratories, biological sciences, radionuclide standardization, nuclear medicine, nuclear power, and fuel cycle facilities, and in the implementation of nuclear forensic analysis and nuclear safeguards. It includes sample preparation techniques for all types of matrices found in the environment, including soil, water, air, plant matter and animal tissue, and surface swipes.Users will find the latest advances in the applications of radioactivity analysis across various fields, including environmental monitoring, radiochemical standardization, high-resolution beta imaging, automated radiochemical separation, nuclear forensics, and more. Spans two volumes, Radiation Physics and Detectors and Radioanalytical Applications Includes a new chapter on the analysis of environmental radionuclides Provides the latest advances in the applications of liquid and solid scintillation analysis, alpha- and gamma spectrometry, mass spectrometric analysis, Cherenkov counting, flow-cell radionuclide analysis, radionuclide standardization, aerosol analysis, high-resolution beta imaging techniques, analytical techniques in nuclear forensics, and nuclear safeguards Describes the timesaving techniques of computer-controlled automatic separation and activity analysis of radionuclides Provides an extensive table of the radiation characteristics of most radionuclides of interest for the radioanalytical chemist