Download or read book Characterizing the Detector Response and Testing the Performance of a New Well Counter for Neutron Coincidence Measurements of Plutonium in Residues written by and published by . This book was released on 2001 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: A thermal neutron detector has been developed that integrates the neutron capture medium (6LiF) and scintillator (ZnS) into a thin screen, which is coupled to wavelength shifting fiber-optic ribbon. The 6LiF and ZnS powders are incorporated in a hydrogenous binder. The detector is constructed of alternating layers of the capture/scintillator screen and the fiber-optic ribbon. The scintillation light produced in the ZnS is absorbed and reemitted in the fibers and is transported to photomultiplier tubes (PMTs). The detector is sensitive to gamrna radiation, but the difference in the pulse decay times of gamma-ray and neutron events allows for discrimination using pulse shape analysis (PSA). To determine the feasibility of using PSA with this detector, a number of intrinsic characteristics of the detector have been measured; specifically, the number of photoelectrons produced at the photocathode of the PMT from the average neutron capture event in the screen and the temperature stability of the detector with respect to pulse shape. The number of photons that reach the PMTs was measured with two different PMTs. One was a typical PMT with single-photoelectron resolution, and the other was a Hybrid PMT comprised of a photocathode coupled to a PIN diode with few-photoelectron resolution. The number of photons that reach the PMTs is between 1600 and 2200, which is sufficient for PSA. The sensitivity of pulse shape to temperature has also been evaluated. Although the pulse decay time changes with varying temperature between -25 to +50 C, the normalized detector pulses have approximately the same amplitude around 400 ns. This results in a stable zero-crossing time of the 400-ns delay-line shaped pulse, and thus the PSA is independent of temperature. A four-sided prototype well counter has been built, It has a short neutron die-away time ([tau]
Download or read book Strategy and Methodology for Radioactive Waste Characterization written by International Atomic Energy Agency and published by IAEA. This book was released on 2007 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past decade significant progress has been achieved in the development of waste characterization and control procedures and equipment as a direct response to ever-increasing requirements for quality and reliability of information on waste characteristics. Failure in control procedures at any step can have important, adverse consequences and may result in producing waste packages which are not compliant with the waste acceptance criteria for disposal, thereby adversely impacting the repository. The information and guidance included in this publication corresponds to recent achievements and reflects the optimum approaches, thereby reducing the potential for error and enhancing the quality of the end product. -- Publisher's description.
Download or read book Handbook of Radioactivity Analysis written by Michael F. L'Annunziata and published by Academic Press. This book was released on 2012-08-16 with total page 1420 pages. Available in PDF, EPUB and Kindle. Book excerpt: Authoritative reference providing the principles, practical techniques, and procedures for the accurate measurement of radioactivity.
Download or read book The Ephithermal Neutron Multiplicity Counter Design and Performance Manual More Rapid Plutonium and Uranium Inventory Verifications by Factors of 5 20 written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal neutron multiplicity counters (TNMCs) assay [sup 240]Pu-effective mass, isolating spontaneous-fission (SF), induced-fission, and ([alpha], n) neutrons emitted from plutonium metal, oxide, scrap, and residue items. Three independent parameters are measured: single, double, and triple neutron-pulse-coincidence count rates. TNMC assays can become precision limited by high ([alpha], n) neutron rates arising from low-Z impurities and [sup 241]Am. TNMCs capture thermal neutrons in 4-atm [sup 3]He tubes after fast-source-neutron moderation by polyethylene. TNMCs are [approximately]50% efficient with [approximately]-[micro]s die-away times. Simultaneously increasing efficiency and reducing die-away time dramatically improve assay precision. Using 10-atm [sup 3]He tubes, they've developed and performance-tested the first of a new generation of neutron assay counters for a wide range of plutonium items. The Epithermal Neutron Multiplicity Counter (ENMC) has an efficiency of 65% and a 22-[micro]s die-away time. The ENMC detects neutrons before thermalization using higher [sup 3]He pressure counters and less moderator than TNMCs. A special insert raises efficiency to 80% for small samples. For five bulk samples containing 50 to 875 g of [sup 240]Pu-effective, ENMC assay times are reduced by factors of 5 to 21, compared with prior state-of-the-art TNMCs. The largest relative gains are for the most impure items, where gains are needed most. In active mode, the ENMC assay times are reduced by factors of 5 to 11, compared with the Active Well Coincidence Counter (AWCC). The ENMC, with high precision and low multiplicity dead time (37 ns), can be used in standards verification mode to precisely and accurately characterize plutonium standards and isotopic sources. The ENMC's performance is very competitive with calorimetry. This report describes the ENMC; presents results of characterization, calibration, and verification measurements; and shows the clear performance and economic advantages of implementing the ENMC for nuclear materials control and accountability.
Download or read book Final Evaluation of Characterizing Pipe over pack Containers Using High Efficiency Neutron Counters written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nondestructive assay (NDA) measurements of Transuranic (TRU) waste at Los Alamos National Laboratory (LANL) packed in Pipe-over-Pack Containers (POC) contain a number of complexities. The POC is highly attenuating to both gamma rays and neutrons which presents a difficult waste matrix for correct quantification of material in the container. Currently there are a number ofPOC containers at LANL that require evaluation for shipment to the Waste Isolation Pilot Plant (WIPP) in Carlsbad, NM. Updated data has been evaluated that finalizes the evaluation of characterizing Pipe-Over-Pack Containers. Currently at LANL, a single instrument has been used to explore the appropriateness of both passive neutron and quantitative gamma ray methods for measuring POC's. The passive neutron approach uses the Reals coincidence count rate to establish plutonium mass and other parameters of interest for TRU waste. The quantitative gamma ray method assumes a homogeneous distribution of radioactive source material with the surrounding material throughout the drum volume. Drums are assayed with a calibration based on the known density of the matrix. Both methods are supplemented by a simultaneous isotopic measurement using Multi-Group Analysis (MGA) to determine the plutonium isotopic composition. If MGA fails to provide a viable isotopic result Fixed Energy Response function Analysis with Multiple efficiencies (FRAM) has been used to replace the MGA results. Acceptable Knowledge (AK) may also be used in certain instances. This report will discuss the two methods in detail. Included in the discussion will be descriptions of the setup parameters and calibration techniques for the instrument. A number of test measurements have been performed to compare HENC data with certified historical data. Empty POCs loaded with known sources have also been measured to determine the viability of the technique. A comparison between calorimetry data, historical measurements and HENC data will also be performed. The conclusion will show that the current calibration on the HENC units is viable for analysis of POCs.
Download or read book Safeguards Techniques and Equipment written by International Atomic Energy Agency and published by . This book was released on 2011 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 1990s saw significant developments in the global non-proliferation landscape, resulting in a new period of safeguards development. The current publication, which is the second revision and update of IAEA/NVS/1, is intended to give a full and balanced description of the safeguards techniques and equipment used for nuclear material accountancy, containment and surveillance measures, environmental sampling, and data security. New features include a section on new and novel technologies. As new verification measures continue to be developed, the material in this book will be reviewed periodically and updated versions issued.
Download or read book Neutron Monitor for Plutonium Inventory Control written by William A. Kropp and published by . This book was released on 1958 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1973 with total page 1052 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Prototype Neutron capture Counter for Fast coincidence Assay of Plutonium in Residues written by and published by . This book was released on 2001 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new neutron coincidence counter with improved capabilities is being built as a commercial prototype. This counter uses 6LiF/ZnS(Ag) based scintillation detectors to achieve a short neutron die-away time ([tau]
Download or read book Thermal neutron Multiplicity Counter Measurements written by and published by . This book was released on 1992 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: An in-plant thermal-neutron multiplicity counter was designed and built to assay plutonium samples for which the relative ([alpha], n)neutron yield and the neutron multiplication are not known. Such samples are difficult to assay with conventional neutron coincidence counting techniques. We have characterized this counter with various 252Cf sources and plutonium samples to study the neutron detection efficiency, electronic dead-time, and neutron die-away properties of the detector and associated electronics. We used a new shift-register electronics module that features 256 channels for multiplicity counting. Preliminary reference parameters have been obtained for performing assays with the multiplicity counting system. We measured a variety of plutonium materials with the in-plant counter in the Los Alamos Plutonium Facility. The materials included samples with high neutron multiplication and samples with ([alpha], n) neutron yields. Preliminary assay results are presented. 12 ref.
Download or read book A New Neutron Multiplicity Counter for the Measurement of Impure Plutonium Metal at Westinghouse Savannah River Site written by and published by . This book was released on 1998 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new neutron multiplicity counter has been designed, fabricated, characterized, and installed for use in the assay of impure plutonium metal buttons from the FB-Line at the Westinghouse Savannah River Site (WSRS). This instrument incorporates the performance characteristics of the Pyrochemical or In-plant Multiplicity Counter with the package size of the Plutonium Scrap Multiplicity Counter. In addition, state-of-the art features such as the de-randomizer circuit and separate ring outputs have been added. The counter consists of 113, 71 cm active length 3He tubes in a polyethylene moderator. Its efficiency for 252Cf is 57.8 percent, the highest of any multiplicity counter to date. Its die-away time is 50.4 ms and its deadtime is 50 ns. In this paper we will present the characterization data for the counter and the results of preliminary metal measurements at WSRS. We will also discuss the new challenges the impure metal buttons from FB-Line are presenting to the multiplicity counting technique.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1979 with total page 1180 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Final Report written by and published by . This book was released on 2014 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Evaluation of In plant Neutron Coincidence Counters for the Measurement of Molten Salt Extraction Residues written by and published by . This book was released on 1993 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Americium is extracted from plutonium by a molten salt extraction (MSE) process. The residual americium-laden salts are a significant waste stream in this pyrochemical purification process. Rapid assay of MSE residues is desirable to minimize the exposure of personnel to these often high-level emissions. However, the quantitative assay of plutonium in MSE residues is difficult. Variable, unknown (a, n) rates and variable emitted-neutron energy spectra preclude the use of standard neutron coincidence counting techniques with old-generation neutron coincidence counters. Gamma-ray assay methods have not been successful with some residues because of random lumps of plutonium metal. In this paper, we present measurements of MSE residues with two state-of-the-art neutron coincidence counters at the Los Alamos Plutonium Processing Facility: an in-line counter built for the assay of bulk waste material and the pyrochemical multiplicity counter that underwent test and evaluation at that facility. Both of these counters were designed to minimize the effects on measurements of variations in the sample geometry and variable energy spectra of emitted neutrons. These results are compared to measurements made with an HLNCII and with a 20-yr-old in-line well counter. The latter two counters are not optimized in ft sense. We conclude that the newer counters provide significantly improved assay results. The pyrochemical multiplicity counter operated in the conventional coincidence mode provided the best assays overall.
Download or read book DIVERSE ACTIVE WELL NEUTRON COINCIDENCE COUNTER UTILITY AT THE SAVANNAH RIVER NATIONAL LABORATORY written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper we describe use of the Aquila active well neutron coincidence counter for nuclear material assays of 235U in multiple analytical techniques at Savannah River Site (SRS), at the Savannah River National Laboratory (SRNL), and at Argonne West National Laboratory (AWNL). The uses include as a portable passive neutron counter for field measurements searching for evidence of 252Cf deposits and storage; as a portable active neutron counter using an external activation source for field measurements searching for trace 235U deposits and holdup; for verification measurements of U-Al reactor fuel elements; for verification measurements of uranium metal; and for verification measurements of process waste of impure uranium in a challenging cement matrix. The wide variety of uses described demonstrate utility of the technique for neutron coincidence verification measurements over the dynamic ranges of 100 g-5000 g for U metal, 200 g-1300 g for U-Al, and 8 g-35 g for process waste. In addition to demonstrating use of the instrument in both the passive and active modes, we also demonstrate its use in both the fast and thermal neutron modes.
Download or read book Nondestructive Assay Tests of High efficiency Neutron Counter HENC for Waste Assay and Possible Diversion Scenario written by and published by . This book was released on 1998 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Design and Performance of a New High Accuracy Combined Small Sample Neutron written by and published by . This book was released on 1993 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes the design of an optimized combined neutron and gamma detector installed around a measurement well protruding from the floor of a glove box. The objective of this design was to achieve an overall accuracy for the plutonium element concentration in gram-sized samples of plutonium oxide powder approaching the (approximately)0.1--0.2% accuracies routinely achieved by inspectors' chemical analysis. The efficiency of the clam-shell neutron detector was increased and the flat response zone extended in axial and radial directions. The sample holder introduced from within the glove box was designed to form the upper reflector, while two graphite half-shells fitted around the thin neck of the high-resolution LEGE detector replaced the lower plug. The Institute for Reference Materials and Measurements (IRMM) in Geel prepared special plutonium oxide test samples whose plutonium concentration was determined to better than 0.05%. During a three week initial performance test in July 1992 at ITU Karlsruhe and in long term tests, it was established that the target accuracy can be achieved provided sufficient care is taken to assure the reproducibility of sample bottling and sample positioning. The paper presents and discusses the results of all test measurements.
