A note on the multiplicity expressions in nuclear safeguards

Pázsit, Imre; Enqvist, Andreas; Пал, Л.

doi:10.1016/j.nima.2009.03.018

Cited by 29 publications

(15 citation statements)

References 4 publications

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“…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. [1,2] 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.…”

Section: Discussionmentioning

confidence: 99%

“…With these three moments, the sample multiplication, fission rate, The calculations and equations shown below have been derived in numerous reports and publications. [8,1,11] The detected neutron singles rate, S, represents all neutrons detected, regardless of their reaction of origin, including those emitted via spontaneous fission, induced fission, reactions. Empirically, this rate can be calculated as:…”

Section: Multiplicity Analysismentioning

confidence: 99%

“…[8,1,12] Factorial moments in this report are represented by the character with a primary subscript of 's' or 'i' denoting whether it is a moment of the multiplicity distribution of the spontaneous fission of 240 Pu or the induced fission of 239 Pu respectively. For all calculations described in this report the multiplicity distribution for fission induced by a 2 MeV neutron was used to determine all i factorial moments.…”

Section: Multiplicity Analysismentioning

confidence: 99%

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MPACT Fast Neutron Multiplicity System Prototype Development

Chichester¹,

Pozzi²,

Dolan³

et al. 2013

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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. [1, 2] 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.

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Section: Discussionmentioning

confidence: 99%

Section: Multiplicity Analysismentioning

confidence: 99%

Section: Multiplicity Analysismentioning

confidence: 99%

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MPACT Fast Neutron Multiplicity System Prototype Development

Chichester¹,

Pozzi²,

Dolan³

et al. 2013

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“…In this section the traditional method of multiplicity counting is summarized briefly using the terminology of [4]. In a multiplicity counting measurement, the detection rates of the first three k-tuplets (k detected neutrons originating from the same sample emission) are determined.…”

Section: Traditional Multiplicity Countingmentioning

confidence: 99%

Measurements and simulations to investigate the feasibility of neutron multiplicity counting in the current mode of fission chambers

et al. 2020

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In two earlier papers [1], [2] we investigated the possibility of extracting traditional multiplicity count rates from the cumulants of fission chamber signals in current mode. It was shown that if all neutrons emitted from the sample simultaneously are also detected simultaneously, the multiplicity rates can be retrieved from the first three cumulants of the currents of up to three detectors, but the method breaks down if the detections of neutrons of common origin take place with a time delay spread wider than the pulse shape. To remedy these shortcomings, in this work we extended the theory to two- and three-point distributions (correlations). It was found thatthe integrals of suitably chosen two- and three-point moments with respect to the time differences become independent of the probability density of the time delays of detections. With this procedure, the multiplicity rates can be retrieved from the detector currents for arbitrary time delay distributions. To demonstrate the practical applicability of the proposed method, a measurement setup was designed and built. The statistics (shape and amplitude distribution) of the detector pulse were investigated as important parameters of the theoretical model. Simulations were performed to estimate the expected value of the multiplicity rates in the built setup. Measurements were performed and two types of moments (the mean and the covariance function) of the recorded detector signals were calculated. Values of singles rates were successfully recovered.

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“…Empirically, this rate can be calculated as: ), İ = detection efficiency, M = sample multiplication (leakage), and Į = the ratio of (D,n) neutrons to spontaneous fission neutrons. [5,8,9] * For this report, factorial moments with subscript "s" denote spontaneous fission, while those without this marking correspond to induced fission. The detected neutron doubles rate, D, is dependent on spontaneous fission, induced fission, and (Į,n) reactions.…”

Section: Multiplicity Analysismentioning

confidence: 99%

MPACT Fast Neutron Multiplicity System Design Concepts

Chichester¹,

Pozzi²,

Dolan³

et al. 2012

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This report documents work performed by Idaho National Laboratory and the University of Michigan in fiscal year (FY) 2012 to examine design parameters related to the use of fast-neutron multiplicity counting for assaying plutonium for materials protection, accountancy, and control purposes. This project seeks to develop a new type of neutron-measurement-based plutonium assay instrument suited for assaying advanced fuel cycle materials. Some current-concept advanced fuels contain high concentrations of plutonium; some of these concept fuels also contain other fissionable actinides besides plutonium. Because of these attributes the neutron emission rates of these new fuels may be much higher, and more difficult to interpret, than measurements made of plutoniumonly materials. Fast neutron multiplicity analysis is one approach for assaying these advanced nuclear fuels.Studies have been performed to assess the conceptual performance capabilities of a fast-neutron multiplicity counter for assaying plutonium. Comparisons have been made to evaluate the potential improvements and benefits of fast-neutron multiplicity analyses versus traditional thermal-neutron counting systems. Fast-neutron instrumentation, using for example an array of liquid scintillators such as EJ-309, have the potential to either a) significantly reduce assay measurement times versus traditional approaches, for comparable measurement precision values, b) significantly improve assay precision values, for measurement durations comparable to current-generation technology, or c) moderately improve both measurement precision and measurement durations versus current-generation technology. Using the MCNPX-PoliMi Monte Carlo simulation code, studies have been performed to assess the doubles-detection efficiency for a variety of counter layouts of cylindrical liquid scintillator detector cells over one, two, and three rows.Ignoring other considerations, the best detector design is the one with the most detecting volume. However, operational limitations guide a) the maximum acceptable size of each detector cell (due to PSD performance and maximum-acceptable per-channel data throughput rates, limited by pulse pile-up and the processing rate of the electronics components of the system) and b)

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A note on the multiplicity expressions in nuclear safeguards

Cited by 29 publications

References 4 publications

MPACT Fast Neutron Multiplicity System Prototype Development

MPACT Fast Neutron Multiplicity System Prototype Development

Measurements and simulations to investigate the feasibility of neutron multiplicity counting in the current mode of fission chambers

MPACT Fast Neutron Multiplicity System Design Concepts

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