Download or read book Estimation of the Performance of Multiple Active Neutron Interrogation Signatures for Detecting Shielded HEU written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive modeling study has been carried out to evaluate the utility of multiple active neutron interrogation signatures for detecting shielded highly enriched uranium (HEU). The modeling effort focused on varying HEU masses from 1 kg to 20 kg; varying types of shields including wood, steel, cement, polyethylene, and borated polyethylene; varying depths of the HEU in the shields, and varying engineered shields immediately surrounding the HEU including steel, tungsten, and cadmium. Neutron and gamma-ray signatures were the focus of the study and false negative detection probabilities versus measurement time were used as a performance metric. To facilitate comparisons among different approaches an automated method was developed to generate receiver operating characteristic (ROC) curves for different sets of model variables for multiple background count rate conditions. This paper summarizes results or the analysis, including laboratory benchmark comparisons between simulations and experiments. The important impact engineered shields can play towards degrading detectability and methods for mitigating this will be discussed.

Download or read book Recueil Documentation sur Andr e Pollier written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Active Interrogation Measurements of Induced Fission Neutrons from Low Enriched Uranium written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Protection and control of nuclear fuels is paramount for nuclear security and safeguards; therefore, it is important to develop fast and robust controlling mechanisms to ensure the safety of nuclear fuels. Through both passive- and active-interrogation methods we can use fast-neutron detection to perform real-time measurements of fission neutrons for process monitoring. Active interrogation allows us to use different ranges of incident neutron energy to probe for different isotopes of uranium. With fast-neutron detectors, such as organic liquid scintillation detectors, we can detect the induced-fission neutrons and photons and work towards quantifying a sample's mass and enrichment. Using MCNPX-PoliMi, a system was designed to measure induced-fission neutrons from U-235 and U-238. Measurements were then performed in the summer of 2010 at the Joint Research Centre in Ispra, Italy. Fissions were induced with an associated particle D-T generator and an isotopic Am-Li source. The fission neutrons, as well as neutrons from (n, 2n) and (n, 3n) reactions, were measured with five 5? by 5? EJ-309 organic liquid scintillators. The D-T neutron generator was available as part of a measurement campaign in place by Padova University. The measurement and data-acquisition systems were developed at the University of Michigan utilizing a CAEN V1720 digitizer and pulse-shape discrimination algorithms to differentiate neutron and photon detections. Low-enriched uranium samples of varying mass and enrichment were interrogated. Acquired time-of-flight curves and cross-correlation curves are currently analyzed to draw relationships between detected neutrons and sample mass and enrichment. In the full paper, the promise of active-interrogation measurements and fast-neutron detection will be assessed through the example of this proof-of-concept measurement campaign. Additionally, MCNPX-PoliMi simulation results will be compared to the measured data to validate the MCNPX-PoliMi code when used for active-interrogation simulations.

Download or read book Active Interrogation Observables for Enrichment Determination of DU Shielded HEU Metal Assemblies with Limited Geometrical Information written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Determining the enrichment of highly enriched uranium (HEU) metal assemblies shielded by depleted uranium (DU) proves a unique challenge to currently employed measurement techniques. Efforts to match time-correlated neutron distributions obtained through active interrogation to Monte Carlo simulations of the assemblies have shown promising results, given that the exact geometries of both the HEU metal assemblies and DU shields are known from imaging and fission site mapping. In certain situations, however, it is desirable to obtain enrichment with limited or no geometrical information of the assemblies being measured. This paper explores the possibility that the utilization of observables in the interrogation of assemblies by time-tagged D-T neutrons, including time-correlated distribution of neutrons and gammas using liquid scintillators operating on the fission chain time scale, can lead to enrichment determination without a complete set of geometrical information.

Download or read book Using Electronic Neutron Generators in Active Interrogation to Detect Shielded Fissionable Material written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments have been performed at Idaho National Laboratory to study methodology and instrumentation for performing neutron active interrogation die-away analyses for the purpose of detecting shielded fissionable material. Here we report initial work using a portable DT electronic neutron generator with a He-3 fast neutron detector to detect shielded fissionable material including>2 kg quantities of enriched uranium and plutonium. Measurements have been taken of bare material as well as of material hidden within a large plywood cube. Results from this work have demonstrated the efficacy of the die-away neutron measurement technique for quickly detecting the presence of special nuclear material hidden within plywood shields by analyzing the time dependent neutron signals in-between neutron generator pulses. Using a DT electronic neutron generator operating at 300 Hz with a yield of approximately 0.36 x 10**8 neutrons per second, 2.2 kg of enriched uranium hidden within a 0.60 m x 0.60 m x 0.70 m volume of plywood was positively detected with a measurement signal 2-sigma above the passive background within 1 second. Similarly, for a 500 second measurement period a lower detection limit of approaching the gram level could be expected with the same simple set-up.

Download or read book MCNP PoliMi Calculations of Active Neutron Interrogation Measurements of HEU Metal written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents a comparison of Monte Carlo Code/MCNP-PoliMi calculations [Ref 1] with measurements of the prompt neutron time behavior after introduction into the highly enriched uranium ((almost equal to)93 wt % 235U) metal of interrogating neutrons from a time tagged 252Cf spontaneous fission source or a time and directionally tagged neutrons from a steady state DT neutron generator with an embedded alpha detector [Ref 2]. These measurements used a fast time correlation processor from the nuclear material identification system (NMIS) which measured the time distribution of detection events on a nanosecond time scale (equivalent to a randomly pulsed neutron measurement) and the time distribution of events in one detector after an event in another detector (equivalent to a two-detector Rossi-alpha measurement) [Ref 3]. These calculations of the prompt neutron time behavior were performed to verify the ability of calculational methods and cross sections to predict the results for subcritical experiments.

Download or read book SIMULATIONS FOR ACTIVE INTERROGATION OF HEU IN CARGO CONTAINERS written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We describe the results of a Monte Carlo simulation 10 investigate the feasibility of using a pulsed deuterium-tritium (D-T) neutron technique for active interrogation of special nuclear material in cargo containers. Time distributions of fission neutrons from highly enriched uranium induced by a pulsed D-T neutron source were calculated for cargo containers with different hydrogen contents. A simple detector system with polyethylene and cadmium was modeled to calculate the two-group neutron flux at the detector.

Download or read book Passive Nondestructive Assay of Nuclear Materials written by Doug Reilly and published by . This book was released on 1991 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Active Neutron Interrogation to Detect Shielded Fissionable Material written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Portable electronic neutron generators (ENGs) may be used to interrogate suspicious items to detect, characterize, and quantify the presence fissionable material based upon the measurement of prompt and/or delayed emissions of neutrons and/or photons resulting from fission. The small size (

Download or read book Addressing Different Active Neutron Interrogation Signatures from Fissionable Material written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In a continuing effort to examine portable methods for implementing active neutron interrogation for detecting shielded fissionable material research is underway to investigate the utility of analyzing multiple time-correlated signatures. Time correlation refers here to the existence of unique characteristics of the fission interrogation signature related to the start and end of an irradiation, as well as signatures present in between individual pulses of an irradiating source. Traditional measurement approaches in this area have typically worked to detect die-away neutrons after the end of each pulse, neutrons in between pulses related to the decay of neutron emitting fission products, or neutrons or gamma rays related to the decay of neutron emitting fission products after the end of an irradiation exposure. In this paper we discus the potential weaknesses of assessing only one signature versus multiple signatures and make the assertion that multiple complimentary and orthogonal measurements should be used to bolster the performance of active interrogation systems, helping to minimize susceptibility to the weaknesses of individual signatures on their own. Recognizing that the problem of detection is a problem of low count rates, we are exploring methods to integrate commonly used signatures with rarely used signatures to improve detection capabilities for these measurements. In this paper we will discuss initial activity in this area with this approach together with observations of some of the strengths and weaknesses of using these different signatures.

Download or read book Portable Active Interrogation System written by and published by . This book was released on 2004 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The system consists of a pulsed DT neutron generator (5 x 107 n/s) and a portable but high intrinsic efficiency, custom-designed, polyethylene-moderated 3He neutron detector. A multichannel scaler card in a ruggedized laptop computer acquires the data. A user-friendly LabVIEW program analyzes and displays the data. The program displays a warning message when highly enriched uranium or any other fissionable materials is detected at a specified number of sigmas above background in the delayed region between pulses. This report describes the system and gives examples of the response of the system to highly enriched uranium and some other fissionable materials, at several distances and with various shielding materials.

Download or read book A Kinematically Beamed Low Energy Pulsed Neutron Source for Active Interrogation written by P. Kerr and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We are developing a new active interrogation system based on a kinematically focused low energy neutron beam. The key idea is that one of the defining characteristics of SNM (Special Nuclear Materials) is the ability for low energy or thermal neutrons to induce fission. Thus by using low energy neutrons for the interrogation source we can accomplish three goals, (1) Energy discrimination allows us to measure the prompt fast fission neutrons produced while the interrogation beam is on; (2) Neutrons with an energy of approximately 60 to 100 keV do not fission 238U and Thorium, but penetrate bulk material nearly as far as high energy neutrons do and (3) below about 100keV neutrons lose their energy by kinematical collisions rather than via the nuclear (n,2n) or (n, n') processes thus further simplifying the prompt neutron induced background. 60 keV neutrons create a low radiation dose and readily thermal capture in normal materials, thus providing a clean spectroscopic signature of the intervening materials. The kinematically beamed source also eliminates the need for heavy backward and sideway neutron shielding. We have designed and built a very compact pulsed neutron source, based on an RFQ proton accelerator and a lithium target. We are developing fast neutron detectors that are nearly insensitive to the ever-present thermal neutron and neutron capture induced gamma ray background. The detection of only a few high energy fission neutrons in time correlation with the linac pulse will be a clear indication of the presence of SNM.

Download or read book System for Active Long Range Detection and Identification of Special Nuclear Materials Using a High Intensity Particle Beam written by Istvan Dioszegi and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A long-range method and a system for reliably detecting and identifying special nuclear materials is provided that relies on the emission of delayed neutrons present in the decay of fission products (delayed neutron precursors) as a unique signature for the special nuclear materials, such as highly enriched uranium (235/238U). The method relies on a time-of-flight measurement in the first 1?s after the inducing radiation pulse, and pulse height data analysis for both neutrons and gamma rays that can be done at a much higher data rate than in traditional pulse processing systems. The thermal neutron fission within the time regime of 100-500?s provides a unique signature of special nuclear materials such as the highly enriched uranium.

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 Investigation of Active Interrogation Techniques to Detect Special Nuclear Material in Maritime Environments written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The detection and interdiction of special nuclear material (SNM) is still a high-priority focus area for many organizations around the world. One method that is commonly considered a leading candidate in the detection of SNM is active interrogation (AI). AI is different from its close relative, passive interrogation, in that an active source is used to enhance or create a detectable signal (usually fission) from SNM, particularly in shielded scenarios or scenarios where the SNM has a low activity. The use of AI thus makes the detection of SNM easier or, in some scenarios, even enables previously impossible detection. In this work the signal from prompt neutrons and photons as well as delayed neutrons and photons will be combined, as is typically done in AI. In previous work AI has been evaluated experimentally and computationally. However, for the purposes of this work, past scenarios are considered lightly shielded and tightly coupled spatially. At most, the previous work interrogated the contents of one standard cargo container (2.44 x 2.60 x 6.10 m) and the source and detector were both within a few meters of the object being interrogated. A few examples of this type of previous work can be found in references 1 and 2. Obviously, more heavily shielded AI scenarios will require larger source intensities, larger detector surface areas (larger detectors or more detectors), greater detector efficiencies, longer count times, or some combination of these.

Download or read book Reflected Neutron Effects in Multiplicity Measurements of Bare HEU Assemblies written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In a passive multiplicity characterization of highly enriched uranium (HEU) assemblies, fission chains are initiated by the characteristically fast neutrons from spontaneous fission of 238U and 235U as well as cosmic-ray spallation neutrons. Active interrogation of HEU uses other physical mechanisms for starting chains by inducing fission from high-energy neutrons, high-energy gamma-rays, delayed neutrons, or thermal neutrons. In all cases a contribution to the initiation of fission chains is the reflection of neutrons that initially escape the assembly and re-enter it after undergoing some scattering. The reflected neutron flux is geometry dependent and a combination of fast and thermal energies. The reflected thermal neutron contribution occurs hundreds of microseconds after the beginning of the fission chain and can be distinguished from the cosmic-ray spallation neutrons unrelated to fission chains, resulting in an HEU detection signature with high signal-to-noise. However, the reflected thermal neutron flux can be eliminated with an efficient thermal neutron absorber to investigate reflected neutron effects. In this paper, active and passive multiplicity measurements with HEU oxide assemblies of up to 16 kg of fuel pins and HEU metal assemblies of up to five 18 kg storage castings are reported. Each case demonstrates the differences in HEU signature when a borated thermal neutron absorber is present and shows the various detectable signatures with 3He proportional counters, the standard detector for differential die-way and neutron multiplicity measurements, and liquid scintillators, a detector capable of operating on the timescale of fission chains.

Download or read book Active Interrogation Using Electronic Neutron Generators for Nuclear Safeguards Applications written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Active interrogation, a measurement technique which uses a radiation source to probe materials and generate unique signatures useful for characterizing those materials, is a powerful tool for assaying special nuclear material. The most commonly used technique for performing active interrogation is to use an electronic neutron generator as the probe radiation source. Exploiting the unique operating characteristics of these devices, including their monoenergetic neutron emissions and their ability to operate in pulsed modes, presents a number of options for performing prompt and delayed signature analyses using both photon and neutron sensors. A review of literature in this area shows multiple applications of the active neutron interrogation technique for performing nuclear nonproliferation measurements. Some examples include measuring the plutonium content of spent fuel, assaying plutonium residue in spent fuel hull claddings, assaying plutonium in aqueous fuel reprocessing process streams, and assaying nuclear fuel reprocessing facility waste streams to detect and quantify fissile material. This paper discusses the historical use of this technique and examines its context within the scope and challenges of next-generation nuclear fuel cycles and advanced concept nuclear fuel cycle facilities.