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Introduction
Publications
Publications (170)
Detecting shielded special nuclear material, such as nuclear explosives, is a difficult challenge pursued by non-proliferation, anti-terrorism, and nuclear security programs worldwide. Interrogation with intense fast-neutron pulses is a promising method to characterize concealed nuclear material rapidly but is limited by suitable source availabilit...
This chapter describes the use of active neutron instrumentation, in which an external neutron source is used to induce fission in the item of interest. The chapter includes a description of the properties of a variety of neutron sources that can be used to induce fission in the item. The application presented include single neutron counting (Cf sh...
This chapter describes the interactions that neutrons have with matter. There is a description of microscopic interactions, such as fission, scattering and absorption, using the concept of cross-section. The idea of individual neutron interactions is extended to the macroscopic behavior of neutrons, giving rise to the calculation of reaction rates...
This chapter presents the various sources of neutrons that are important in nondestructive measurements. These sources include the key mechanisms of spontaneous fission, neutrons from alpha particle reactions on light elements, and induced fission. The characteristics of neutrons resulting from typical sources are presented. A brief discussion of o...
This chapter presents a description of most of the instruments that are currently in use for the measurement of plutonium and uranium using passive methods (without an external source). This includes the acquisition electronics as well as Singles counting methods, coincidence counting methods and multiplicity counting methods. The Singles counting...
This chapter describes the principles of operation of the main types of neutron detector that are used in nondestructive assay. One section is devoted to gas detectors ( ³ He and BF 3 ) as well as boron-lined detectors, proton recoil detectors and fission chambers. A second section describes scintillation detectors. The description includes a discu...
This chapter describes the principles involved with using neutron coincidences that obtain more information about a measured sample than through singles counting alone. The chapter describes the origin of neutron correlations and how they manifest themselves in the neutron pulse train from a detector. The Rossi-α distribution is presented. The chap...
This chapter presents an introduction to the basic concept of uncertainty, which is that every result is an instance taken from a distribution of potential measurements. Describing this distribution is an important part of characterizing a result. This is a complex topic and the literature has not always been consistent in the use of specific terms...
The active uranium neutron coincidence collar provides a means of non-destructively assaying the fissile linear density of Light Water Reactor fresh fuel assemblies containing low enriched uranium. These neutron collars can operate in two modes: a thermal and a fast mode. In fast mode, a neutron collar has an added cadmium (Cd) liner in the sample...
Measurements were performed using multiple mechanically cooled high-purity germanium detectors at six positions around standard industrial 30B cylinders (2.2 metric ton) of UF6 to assess if matrix inhomogeneity is detectable and its impacts on the measured apparent uranium enrichment. Uranium enrichment was calculated with FRAM™. Six of the nine cy...
In 2018, a measurement campaign took place with participants from Los Alamos National Laboratory (LANL), the Nuclear Research Centre-Negev (NRCN) and Soreq Nuclear Research Center (SNRC) at the Israeli Research Reactor-1 (IRR-1) in which 14 of the reactor’s used fuel assemblies (FAs) with varied amount of depletion were measured with the nondestruc...
Natural, depleted, and low enriched uranium hexafluoride is manufactured and transported on an industrial scale to support commercial nuclear power plant operation. One-way material production and flow is verified by nuclear safeguards inspectorates is by neutron counting. The dominant neutron source term is (α,n) production due to ²³⁴U which gets...
22Na ingrowth originating from fluorine–alpha interactions has been proposed as a chronometer for U F6 cylinders. However, these proposals have ignored the prompt 1274 keV gamma-ray contribution from ¹⁹F(α, p). We have shown that this contribution is significant and cannot be ignored when using this as a chronometer for UF6.
Compact, bright neutron sources are opening up several emerging applications including detection of nuclear materials for national security applications. At Los Alamos National Laboratory, we have used a short-pulse laser to accelerate deuterons in the relativistic transparency regime. These deuterons impinge on a beryllium converter to generate ne...
Monte Carlo simulation is a powerful tool used to model neutron coincidence detectors for international safeguards. The simulation has typically sampled properties such as the fission neutron multiplicity, energy, and direction, from independent probability density functions. However, multiplicity counters detect event-based neutron correlations an...
In recent years, the International Atomic Energy Agency (IAEA) has pursued innovative techniques and an integrated suite of safeguards measures to address the verification challenges posed by the front end of the nuclear fuel cycle. Among the unattended instruments currently being explored by the IAEA is an Unattended Cylinder Verification Station...
Lightly encapsulated 252Cf sources are commonly used to
characterize and calibrate neutron detectors for safeguards
applications without much attention being paid to
what it means for the encapsulation to be neutronically
“light”. In this work we quantify the impact of encapsulation
on both the neutron spectrum and neutron intensity. We
find that a...
Laser-plasma interactions in the novel regime of relativistically induced transparency (RIT) have been harnessed to generate intense ion beams efficiently with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at “table-top” scales in experiments at the LANL Trident Laser. By further optimization of the laser and target, the RIT regi...
The purpose of the Next Generation Safeguards Initiative (NGSI)–Spent Fuel (SF) project is to strengthen the technical toolkit of safeguards inspectors and/or other interested parties. The NGSI–SF team is working to achieve the following technical goals more easily and efficiently than in the past using nondestructive assay measurements of spent fu...
Emerging approaches to short-pulse laser-driven neutron production offer a possible gateway to compact, low cost, and intense broad spectrum sources for a wide variety of applications. They are based on energetic ions, driven by an intense short-pulse laser, interacting with a converter material to produce neutrons via breakup and nuclear reactions...
This paper describes the development of quantitative nuclear data uncertainty analysis tools for the systematic evaluation of complex, often multi-physics problems that rely on a vast array of diverse nuclear data. These tools can be applied to assess total uncertainty from data and are also being designed to quantify contributions of individual nu...
The widely encountered case of plutonium oxide is analyzed to evaluate uncertainties and uncertainty contributions from nuclear data because it exercises a broad range of data: • plutonium and oxygen neutron reaction cross sections, • neutron-induced fission data for plutonium isotopes, • 240Pu spontaneous fission neutron spectrum, • P(ν) for 240Pu...
As part of the United States (US) Department of Energy's Next Generation Safeguards Initiative Spent Fuel (NGSI-SF) project, the traditional Differential Die-Away (DDA) method that was originally developed for waste drum assay has been investigated and modified to provide a novel application to characterize or verify spent nuclear fuel (SNF). Follo...
A short-pulse laser-driven deuteron beam is generated in the relativistic transparency regime and aimed at a beryllium converter to generate neutrons at the TRIDENT laser facility. These prompt neutrons have been used for active interrogation to detect nuclear materials, the first such demonstration of a laser-driven neutron source. During the expe...
In neutron coincidence counting using the shift register autocorrelation technique, a predelay is inserted before the opening of the (R+A)-gate. Operationally the purpose of the predelay is to ensure that the (R+A)- and A-gates have matched effectiveness, otherwise a bias will result when the difference between the gates is used to calculate the ac...
International safeguards inspectorates (e.g., International Atomic Energy Agency {IAEA}, or Euratom) rely heavily on neutron assay techniques, and in particular, on coincidence counters for the verification of declared nuclear materials under safeguards and for monitoring purposes. While ³He was readily available, the reliability, safety, ease of u...
Neutron coincidence and multiplicity counting is a standard technique used to measure uranium and plutonium masses in unknown samples for nuclear safeguarding purposes. Time correlated neutron detections and knowledge of fission neutron production are used to find the composition of the sample. Background sources of radiation can obscure the detect...
Previous simulation studies of Differential Die‐Away (DDA) instrument’s response to active interrogation of spent nuclear fuel from a pressurized water reactor (PWR) yielded promising results in terms of its capability to accurately measure or estimate basic spent fuel assembly (SFA) characteristics, such as multiplication, initial enrichment (IE)...
Most 3He replacement neutron detector technologies today have overlapping neutron-gamma pulse-height distributions, which limits their usefulness and performance. Different techniques are used to mitigate this shortcoming, including Pulse Shape Discrimination (PSD) or threshold settings that suppress all gammas as well as much of the neutrons. As a...
Correlated neutron counting using multiplicity shift register logic extracts the first three factorial moments from the detected neutron pulse train. The descriptive properties of the measurement item (mass, the ratio of (α,n) to spontaneous fission neutron production, and leakage self-multiplication) are related to the observed singles (S), double...
In this paper, we report our progress toward the development of an advanced enrichment monitoring technology for safeguarding gas centrifuge enrichment plants. We compare the UF6 gas pipe attenuation and sensitivity to X-ray tube HV variations for two transmission energies: 22 keV and 25.5 keV. The first experimental enrichment results taken with a...
As a part of the Next Generation Safeguards Initiative Spent Fuel project, we simulate the response of the Differential Die-away Self-Interrogation (DDSI) instrument to determine total elemental plutonium content in an assayed spent nuclear fuel assembly (SFA). We apply recently developed concepts that relate total plutonium mass with SFA multiplic...
The Swedish Nuclear Fuel and Waste Management Company (SKB), European Atomic Energy
Community (Euratom), two universities and several U.S. Department of Energy Laboratories have joined in
a collaborative research effort to determine the capability of non-destructive assay (NDA) techniques for
spent fuel to meet the combined needs of the safeguards...
List-mode data collection for high-activity sources such as spent nuclear fuel has been made possible recently by advances in data collection and data-storage capabilities. While the shift-register technique has been utilized primarily in the past, list-mode data collection and subsequent Rossi-alpha distribution (RAD) production offers the same an...
We present a novel method for determining the multiplication of a spent nuclear fuel assembly with a Differential Die-Away Self-Interrogation (DDSI) instrument. The signal, which is primarily created by thermal neutrons, is measured with four 3He detector banks surrounding a spent fuel assembly. The Rossi-alpha distribution (RAD) at early times ref...
Safeguards inspection measurements must be performed in a timely manner in order to detect the diversion of significant quantities of nuclear material. A shorter measurement time can increase the number of items that a nuclear safeguards inspector can reliably measure during a period of access to a nuclear facility. In turn, this improves the relia...
Self-Interrogation Neutron Resonance Densitometry (SINRD) is one of
several nondestructive assay (NDA) techniques being integrated into
systems to measure spent fuel as part of the Next Generation Safeguards
Initiative (NGSI) Spent Fuel Project. The NGSI Spent Fuel Project is
sponsored by the US Department of Energy's National Nuclear Security
Admi...
The Next Generation Safeguards Initiative (NGSI) Spent Fuel Nondestructive Assay Project was started in March of 2009. The primary focus of this effort is to determine the Pu mass in spent fuel assemblies using nondestructive assay; additional goals include applying other signatures to verify the completeness and correctness of spent fuel declarati...
As a part of the Next Generation Safeguards Initiative (NGSI) Spent Fuel Nondestructive Assay (NDA) project, we are researching the capability of the differential die-away self-interrogation (DDSI) technique to measure or estimate the isotopic composition of fissile and fertile content of spent nuclear fuel. Since the measured Rossi-alpha distribut...
In this paper, we present a novel approach to estimating the total plutonium content in a spent fuel assembly (SFA) that is based on combining information from a passive measurement of the total neutron count rate (PN) of the assayed SFA and a measure of its multiplication. While PN can be measured essentially with any non-destructive assay (NDA) t...
The nuclear material contained in the process equipment of a uranium enrichment plant (referred to as holdup) is an important component of the overall nuclear material inventory for the plant. Accurate quantification and verification of holdup is needed to improve international safeguards and nuclear material accountancy. This is also needed for cr...
The Next Generation Safeguards Initiative Spent Fuel (NGSI-SF) Project started in 2009 with the general purpose of strengthening the technical toolkit of safeguard inspectors and the focused goal of measuring the Pu mass in spent fuel assemblies. Subsequently the safeguards goals of the projects have evolved to include verifying the correctness and...
The new plastic scintillators with n/γ pulse shape discrimination (PSD) properties being developed by the Lawrence Livermore National Laboratory (LLNL) and commercialized by Eljen Technology are addressing the toxicity and flammability issues of liquid scintillators, thus enabling a much wider range of practical applications for the detection of ne...
Alternatives to helium-3 are being actively pursued due to the shortage and rising costs of helium-3. For safeguards applications, there are a number of ongoing investigations to find alternatives that provide the same capability in a cost-effective manner. One of the greatest challenges is to find a comparable alternative for multiplicity counters...
Uranium cylinder assay plays an important role in the nuclear material accounting at gas centrifuge enrichment plants. The Passive Neutron Enrichment Meter (PNEM) was designed to determine uranium mass and enrichment in 30B and 48Y cylinders using total neutron and coincidence counting in the passive mode. 30B and 48Y cylinders are used to hold bul...
A new nondestructive assay technique called selfinterrogation neutron resonance densitometry (SINRD) is currently being developed at Los Alamos National Laboratory to improve existing nuclear safeguards and material accountability measurements for light water reactor fuel assemblies. The viability of using SINRD to improve the detection of possible...
Fluorine has a relatively large (α,n) production cross-section in the MeV range, the energy range of interest for special nuclear materials. In the uranium fuel cycle enriched UF6 in particular is a reasonably prolific source of (α,n) neutrons because along with 235U, 234U becomes enriched and it has a relatively short half-life. This enables the m...
Boron-lined proportional technologies are increasingly being considered as a viable option for the near-term replacement of 3He-based technologies for use in international nuclear safeguards neutron detection and coincidence counting applications. In order to determine the applicability and feasibility of any replacement technology for internationa...
This paper presents an experimental comparison of different neutron pulse train analysis methods developed to extract correlated count rates from the detected neutron arrival times. This work comprises a sequel to the previous paper (Part I Theory) [1], where the complete formalism of different analysis methods was presented. In the current paper,...
Transmission measurements of radiation through process pipes provide a non-intrusive method of determining the amount of product present in the pipes. The product could be a liquid, a slurry, or a gas, which is the most challenging because of the low density. Traditionally, these techniques have used a radioactive source that has to be replaced per...
Estimating plutonium (Pu) mass in spent nuclear fuel assemblies (SFAs) helps inspectors ensure that no Pu is diverted. Therefore, nondestructive assay (NDA) methods are being developed to assay Pu mass in SFAs. Uncertainty quantification is an important task in most assay methods, and particularly for SFA assay. A computer model (MCNPX) is being us...
Multiplicity counters are an example of a neutron detection system affected by the shortage of 3He. Efforts are underway to identify potential 3He neutron detector replacements for use in multiplicity counters. Boron-10 and 6Li based systems are two of the options being explored as near-term 3He alternatives for neutron multiplicity counters. Simul...
The purpose of this talk is to give an overview of the role of modeling and simulation in Safeguards R&D and introduce you to (some of) the tools used. Some definitions are: (1) Modeling - the representation, often mathematical, of a process, concept, or operation of a system, often implemented by a computer program; (2) Simulation - the representa...
In this article we extend the neutron multiplicity counting dead time correction scheme devised by Dytlewski to include Singles. In this way a self consistent, item specific, Singles dead time correction is obtained under the same physical assumptions and approximations as are used for the Doubles and Triples corrections. This correction for the Si...
A new non-destructive assay technique called Self-Interrogation Neutron Resonance Densitometry (SINRD) is currently being developed at Los Alamos National Laboratory (LANL) to improve existing nuclear safeguards measurements for Light Water Reactor (LWR) fuel assemblies. SINRD consists of four 235U fission chambers (FCs): bare FC, boron carbide shi...
A new nondestructive assay technique called self-interrogation neutron resonance densitometry (SINRD) is currently being developed at Los Alamos National Laboratory to improve existing nuclear safeguards and material accountability measurements for light water reactor fuel assemblies. The viability of using SINRD to quantify the fissile content ( 2...
Overview of this presentation is: (1) pulsed histogram analysis, (2) creation of SPNS, (3) use of SPNS for modeling pulsed neutron data, (4) creation of MUDI, (5) calculated accidentals correction using GUAM + MUDI, (6) background subtraction analysis, and (7) current/figure work with MCNP.
The Passive Neutron Enrichment Meter (PNEM) is a nondestructive assay (NDA) system being developed at Los Alamos National Laboratory (LANL). It was designed to determine ²³âµU mass and enrichment of uranium hexafluoride (UFâ) in product, feed, and tails cylinders (i.e., 30B and 48Y cylinders). These cylinders are found in the nuclear fuel cycle...
The Self-interrogation Neutron Resonance Densitometry Technique (SINRD) is one of the fourteen nondestructive assay (NDA) techniques investigated under the Next Generation Safeguards Initiative (NGSI) effort. SINRD shows promising capability in determining the 239Pu and 235U content in spent nuclear fuel. SINRD is a relatively low-cost and lightwei...
252Cf Interrogation with Prompt Neutron (CIPN) detection is one of the fourteen nondestructive assay (NDA) techniques researched under the Next Generation Safeguards Initiative effort. CIPN is relatively low-cost and lightweight instrument, and it looks like a Fork detector combined with an active interrogation source. This study of CIPN evaluates...
Ever since there has been spent fuel (SF), researchers have made nondestructive assay (NDA) measurements of that fuel to learn about its content. In general these measurements have focused on the simplest signatures (passive photon and total neutron emission) and the analysis has often focused on diversion detection and on determining properties su...
One pressing research and development challenge currently facing the nuclear safeguards community is finding an alternative to 3He gas for neutron detection. The high demand for 3He gas for several scientific and global security applications has exceeded the gas supply. 1 This has resulted in the depletion of 3He stockpiles and consequent shortfall...
As part of the Next Generation Safeguards Initiative (NGSI) spent fuel project, researchers evaluated the ability of fourteen different non-destructive assay techniques to determine elemental plutonium content in a spent fuel assembly (SFA). The Differential Die-away (DDA) technique is one of these techniques.DDA uses short neutron pulses generated...
The Differential Die-away Self-Interrogation (DDSI) technique is being studied by the Next Generation Safeguard Initiative (NGSI) for the purposes of determining fissile mass, and eventually Pu mass, in spent fuel assemblies. The technique utilizes ambient neutrons primarily from the spontaneous fission of 244Cm to interrogate the fissile materials...
Collaboration between the Pacific Northwest National Laboratory (PNNL) and the Los Alamos National Laboratory (LANL) is underway to evaluate neutron detection technologies that might replace the high-pressure helium (3He) tubes currently used in neutron multiplicity counter for safeguards applications. The current stockpile of 3He is diminishing an...
Inspired by approach of Bignan and Martin-Didier (ESARDA 1991) we introduce novel (instrument independent) approach based on multiplication and passive neutron. Based on simulations of SFL-1 the accuracy of determination of {sup tot}Pu content with new approach is â1.3-1.5%. Method applicable for DDA instrument, since it can measure both multiplica...
The differential die-away (DDA) technique has been simulated by using the MCNPX code to quantify its capability of measuring the fissile content in spent fuel assemblies. For 64 different spent fuel cases of various initial enrichment, burnup and cooling time, the count rate and signal to background ratios of the DDA system were obtained, where neu...
The Next Generation Safeguards Initiative (NGSI) of the U.S. Department of Energy has funded a multi-lab/multi-university collaboration to quantify the plutonium mass in spent nuclear fuel assemblies and to detect the diversion of pins from them. The goal of this research effort is to quantify the capability of various non-destructive assay (NDA) t...
Increasing needs for neutron detection and limited supply of 3He have led to the need for replacement neutron detection technology. This paper presents the design and initial results for a neutron detector (6Li foil scintillator sandwich) that uses lithium metal foil to detect thermal neutrons. The reaction products, primarily triton, deposit most...
The nondestructive assay of Plutonium bearing items for criticality, safety, security, safeguards, inventory balance, process control, waste management and compliance is often undertaken using correlated neutron counting. In particular Multiplicity Shift Register analysis allows one to extract autocorrelation parameters from the pulse train which c...
This paper describes the techniques that are available to calculate the performance of 3He alternative detectors using MCNPX. Calculations of the performance of safeguards detectors that use 3He have been successfully carried out for many years. In the case of coincidence or multiplicity counting, specific tallies have been implemented to calculate...
To address the urgent need to find a viable 3He replacement technology, Los Alamos National Laboratory has developed an integrated test program for performance evaluation of 3He replacement technologies with focus on safeguards specific parameters. In addition, a dedicated experimental setup was built to support the experimental activities. Current...
In the field of neutron multiplicity counting, modern list mode counters provide increased possibilities for neutron data analysis. Here a new method to correct dead-time using a multichannel list mode neutron counter is described. As it will become clear in this article, the data analysis can be done “on the fly” without further data storage. This...
The Japan Atomic Energy Agency (JAEA) has worked on high-accuracy measurement of plutonium mass by non-destructive assay under a joint study program with the Los Alamos National Laboratory (LANL) in order to improve the effectiveness and efficiency of safeguards. As a part of this approach, we have developed the Epithermal Neutron Multiplicity Coun...
Neutron coincidence measurements of plutonium samples with uncertainties <0.5% could reduce the amount of costly destructive analysis required for nuclear material accountancy in plutonium handling plants. The ratio of (α,n) emission to spontaneous fission neutron emission, a, of plutonium samples is important to the interpretation of neutron coinc...
The existing Monte Carlo N-Particle (MCNPX) particle tracking (PTRAC) coincidence capture file allows a full list of neutron capture events to be recorded in any simulated detection medium. The originating event history number (e.g. spontaneous fission events), capture time, location and source particle number are tracked and output to file for pos...
Safeguarding sensitive fuel cycle technology such as uranium enrichment is a critical component in preventing the spread of nuclear weapons. A useful tool for the nuclear materials accountancy of such a plant would be an instrument that measured the uranium content of UF cylinders. The Uranium Cylinder Assay System (UCAS) was designed for Japan Nuc...