Download or read book Neutron Multiplicity Counter Development written by and published by . This book was released on 1991 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have designed and built two multiplicity counters to test the usefulness of multiplicity counting for the safeguards assay of plutonium-bearing materials. The first prototype counter has been characterized and a variety of plutonium-bearing materials have been measured with it. Assays accurate to (approximately)0.7% have been obtained for both pure and impure plutonium oxide samples in reasonable measurement times. Assays accurate to (approximately)5% have been obtained for metal samples. A second multiplicity counter has been designed using experience gained from the first as well as Monte Carlo simulations. The second counter was designed to be more suitable for in-plant measurement of pyrochemical process materials. This paper presents the results of characterization studies of the two instruments. 10 refs., 9 figs., 2 tabs.

Download or read book Development of Neutron Multiplicity Counters for Safeguards Assay written by and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper reports on the development of a new generation of neutron multiplicity counters for assaying impure plutonium. The new counters will be able to obtain three measured parameters from the neutron multiplicity distribution and will be able to determine sample mass, multiplication, and (.cap alpha., n) reaction rate, making it possible to obtain a more matrix-independent assay of moist or impure materials. This paper describes the existing prototype multiplicity counters and evaluates their performance using assay variance as a figure of merit. The best performance to date is obtained with a high-efficiency, low die-away-time thermal neutron counter with shift-register electronics. 10 refs., 2 figs., 4 tabs.

Download or read book Development of Neutron Well Coincidence Counters for Plutonium Assay and Neutron Multiplicity Studies written by T. Datta and published by . This book was released on 1991 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book MPACT Fast Neutron Multiplicity System Prototype Development written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This document serves as both an FY2103 End-of-Year and End-of-Project report on efforts that resulted in the design of a prototype fast neutron multiplicity counter leveraged upon the findings of previous project efforts. The prototype design includes 32 liquid scintillator detectors with cubic volumes 7.62 cm in dimension configured into 4 stacked rings of 8 detectors. Detector signal collection for the system is handled with a pair of Struck Innovative Systeme 16-channel digitizers controlled by in-house developed software with built-in multiplicity analysis algorithms. Initial testing and familiarization of the currently obtained prototype components is underway, however full prototype construction is required for further optimization. Monte Carlo models of the prototype system were performed to estimate die-away and efficiency values. Analysis of these models resulted in the development of a software package capable of determining the effects of nearest-neighbor rejection methods for elimination of detector cross talk. A parameter study was performed using previously developed analytical methods for the estimation of assay mass variance for use as a figure-of-merit for system performance. A software package was developed to automate these calculations and ensure accuracy. The results of the parameter study show that the prototype fast neutron multiplicity counter design is very nearly optimized under the restraints of the parameter space.

Download or read book Application Guide to Neutron Multiplicity Counting written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

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 The Epithermal Neutron Multiplicity Counter at Hanford written by and published by . This book was released on 2002 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Epithermal Neutron Multiplicity Counter (ENMC) and the associated Advanced Multiplicity Shift register (AMSR) electronics package, developed at Los Alamos under the US Department of Energy (DOE) Office of Safeguards and Security Technology Development Program, was evaluated at the Hanford Plutonium Finishing Plant earlier this year. Initial demonstration measurements involved Hanford facility personnel and two International Atomic Energy Agency (IAEA) inspectors who measured selected IAEA standards and items the IAEA had experienced problems with previously. Items were measured in the ENMC and also in the Plutonium Scrap Multiplicity Counter (PSMC), which belongs to the IAEA but is also used by the facility. Each item was measured for 15 minutes. The Pu mass ranged from 250 to 1700 g. Alpha (the ratio of alpha, n to spontaneous fission neutrons) ranged from 0.5 to (almost equal to)15. In all cases, the precision of the ENMC measurements was far superior to that of the PSMC and provided 8.3 to 42.5 faster measurements, with the larger factors coming from the high-alpha items. The seven IAEA standards had alpha values ranging from 0.5 to 13, and the average bias was 0.75% with a standard deviation of 3.18% for the ENMC. The mean bias for the PSMC measurements is 4.02% with a standard deviation of 8.27%. In addition, the ENMC was used to assay 17 process residues with alpha values ranging from 2 to 20. The facility and the IAEA were impressed with the performance of the ENMC, and the facility is attempting to procure a unit for its use. The IAEA would also like to use the ENMC for its inspections once the facility has acquired the device.

Download or read book Pyrochemical Multiplicity Counter Development written by and published by . This book was released on 1991 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Impure plutonium-bearing materials from pyrochemical processes often display both significant self-multiplication and variable ([alpha], n) reaction rates. Standard neutron coincidence counting techniques usually fail to accurately measure these materials. Neutron multiplicity counters measure the third moment of the neutron multiplicity distribution and thus make it possible to deduce the fertile plutonium mass of a sample even when both the self-multiplication and the ([alpha], n) reaction rate are unknown. A multiplicity counter suitable for measuring pyrochemical materials has been designed and built. This paper describes the results of characterization studies for the new counter. The counter consists of 126 helium-3 tubes arranged in 4 concentric rings in a polyethylene moderator; the average spacing between the tubes is 1.59 cm. The end plugs for the counter are made of graphite, and the 24.1- by 37.5-cm sample cavity is cadmium lined. The counter consists of two distinct halves from which the neutron counts are summed. The counter is capable of operation in either a freestanding mode with the two halves coupled together by an external cabinet or in a glove-box mode with the two halves placed around a glovebox well and then mated. For a 252Cf source centered in the sample cavity, the measured efficiency of the new multiplicity counter is 57.7% and its die-away time is 47.2[mu]s. 8 refs., 9 figs.

Download or read book Neutron Multiplicity Easurements With 3He Alternative written by and published by . This book was released on 2015 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Counting neutrons emitted by special nuclear material (SNM) and differentiating them from the background neutrons of various origins is the most effective passive means of detecting SNM. Unfortunately, neutron detection, counting, and partitioning in a maritime environment are complex due to the presence of high-multiplicity spallation neutrons (commonly known as "ship effect") and to the complicated nature of the neutron scattering in that environment. In this study, a prototype neutron detector was built using 10B as the converter in a special form factor called "straws" that would address the above problems by looking into the details of multiplicity distributions of neutrons originating from a fissioning source. This paper describes the straw neutron multiplicity counter (NMC) and assesses the performance with those of a commercially available fission meter. The prototype straw neutron detector provides a large-area, efficient, lightweight, more granular (than fission meter) neutron-responsive detection surface (to facilitate imaging) to enhance the ease of application of fission meters. Presented here are the results of preliminary investigations, modeling, and engineering considerations leading to the construction of this prototype. This design is capable of multiplicity and Feynman variance measurements. This prototype may lead to a near-term solution to the crisis that has arisen from the global scarcity of 3He by offering a viable alternative to fission meters. This paper describes the work performed during a 2-year site-directed research and development (SDRD) project that incorporated straw detectors for neutron multiplicity counting. The NMC is a two-panel detector system. We used 10B (in the form of enriched boron carbide: 10B4C) for neutron detection instead of 3He. In the first year, the project worked with a panel of straw neutron detectors, investigated its characteristics, and developed a data acquisition (DAQ) system to collect neutron multiplicity information from spontaneous fission sources using a single panel consisting of 60 straws equally distributed over three rows in high-density polyethylene moderator. In the following year, we developed the field-programmable gate array and associated DAQ software. Finally, this SDRD effort successfully produced a prototype NMC with ~33% detection efficiency compared to a commercial fission meter.

Download or read book Development of a High efficiency Neutron Counter Using Novel Materials written by and published by . This book was released on 1997 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Development of a Portable Neutron Coincidence Counter for Field Measurements of Nuclear Materials Using the Advanced Multiplicity Capabilities of MCNPX 2 5 F and the Neutron Coincidence Point Model written by Angela Lynn Thornton and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Neutron coincidence counting is an important passive Nondestructive Assay (NDA) technique widely used for qualitative and quantitative analysis of nuclear material in bulk samples. During the fission process, multiple neutrons are simultaneously emitted from the splitting nucleus. These neutron groups are often referred to as coincident neutrons. Because different isotopes possess different coincident neutron characteristics, the coincident neutron signature can be used to identify and quantify a given material. In an effort to identify unknown nuclear samples in field inspections, the Portable Neutron Coincidence Counter (PNCC) has been developed. This detector makes use of the coincident neutrons being emitted from a bulk sample. An in-depth analysis has been performed to establish whether the nuclear material in an unknown sample could be quantified with the accuracy and precision needed for safeguards measurements. The analysis was performed by comparing experimental measurements of PuO2 samples to the calculated output produced using MCNPX and the Neutron Coincidence Point Model. Based on the analysis, it is evident that this new portable system can play a useful role in identifying nuclear material for verification purposes.

Download or read book The Performance of the Large Neutron Multiplicity Counter at the Rocky Flats Environmental Technology Site written by D.G. Langner and published by . This book was released on 1998 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A neutron multiplicity counter for the detection of superheavy nuclei written by Colin Rudolph and published by . This book was released on 1972 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Variations of Point Model Analysis in Neutron Multiplicity Counting and On going Theoretical Developments written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fast Neutron Multiplicity Counter Based on Stilbene and EJ 309 Detectors written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Simulations of Neutron Multiplicity Measurements with MCNP PoliMi written by and published by . This book was released on 2010 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: The heightened focus on nuclear safeguards and accountability has increased the need to develop and verify simulation tools for modeling these applications. The ability to accurately simulate safeguards techniques, such as neutron multiplicity counting, aids in the design and development of future systems. This work focuses on validating the ability of the Monte Carlo code MCNPX-PoliMi to reproduce measured neutron multiplicity results for a highly multiplicative sample. The benchmark experiment for this validation consists of a 4.5-kg sphere of plutonium metal that was moderated by various thicknesses of polyethylene. The detector system was the nPod, which contains a bank of 15 3He detectors. Simulations of the experiments were compared to the actual measurements and several sources of potential bias in the simulation were evaluated. The analysis included the effects of detector dead time, source-detector distance, density, and adjustments made to the value of [nu]-bar in the data libraries. Based on this analysis it was observed that a 1.14% decrease in the evaluated value of [nu]-bar for 239Pu in the ENDF-VII library substantially improved the accuracy of the simulation.

Download or read book FISSILE MATERIAL TRANSPARENCY TECHNOLOGY DEMONSTRATION written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: