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Title: PERFORMANCE OF UPGRADED THERMAL NEUTRON COUNTERS (TNCs)

Abstract

No abstract prepared.

Authors:
;
Publication Date:
Research Org.:
Los Alamos National Lab., NM (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
783422
Report Number(s):
LA-UR-01-4141
TRN: US0302071
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 Jul 2001
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION; PERFORMANCE; THERMAL NEUTRONS; LANL

Citation Formats

J. M. PECOS, and J. E. MALCOLM. PERFORMANCE OF UPGRADED THERMAL NEUTRON COUNTERS (TNCs). United States: N. p., 2001. Web.
J. M. PECOS, & J. E. MALCOLM. PERFORMANCE OF UPGRADED THERMAL NEUTRON COUNTERS (TNCs). United States.
J. M. PECOS, and J. E. MALCOLM. Sun . "PERFORMANCE OF UPGRADED THERMAL NEUTRON COUNTERS (TNCs)". United States. doi:. https://www.osti.gov/servlets/purl/783422.
@article{osti_783422,
title = {PERFORMANCE OF UPGRADED THERMAL NEUTRON COUNTERS (TNCs)},
author = {J. M. PECOS and J. E. MALCOLM},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jul 01 00:00:00 EDT 2001},
month = {Sun Jul 01 00:00:00 EDT 2001}
}

Conference:
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  • Worldwide, significant effort has been expended to develop replacement technologies for 3He-filled proportional counters used as neutron detectors and employed extensively in applications as diverse as Homeland Security portal monitoring to fundamental scientific research. Far less attention has been paid to the specific needs of safeguards measurement systems to meet mission objectives such as international obligations under the Nuclear Non-Proliferation Treaty. The measurement configuration, operational environments, and performance requirements for the typical safeguards assay system are sufficiently different from those of other applications that the new generation of neutron detectors is not generally suitable for use in demanding safeguards applications.more » To illustrate the performance needs for any viable replacement neutron detector technology, the operational constraints for several typical safeguards measurement systems are considered. Key attributes include achieving adequate efficiency per unit volume and minimal parasitic losses, along with gamma-ray immunity in a unit with high reliability and low maintenance.« less
  • Multiplicity analysis algorithms are extended to include the effect of ({alpha}, n) neutron energies on the detector efficiencies, induced fission probabilities, and induced fission factorial moments. The analysis is restricted to plutonium oxide. Bias is calculated as a function of ({alpha}, n) neutron energy for six thermal neutron coincidence counters: HLNC, AWCC, 3RMC, PSMC, PYRO, and 5RMC. Ring ratio data for the 3RMC are used to reduce energy dependent bias in the verification of impure plutonium oxide. The utility of the AWCC as a multiplicity counter is considered.
  • A coincidence neutron counting method has been developed for assaying batches of plutonium oxalate. Using counting data from two concentric rings of /sup 3/He detectors, corrections are made for the effects that water has on the coincidence neutron count rate. Batches of plutonium oxalate varying from 750 to 1000 g of plutonium and from 34 to 54% water are assayed with an average accuracy of +-3%.
  • We have developed a deadtime reduction circuit for thermal neutron coincidence counters using Amptek preamplifier/amplifier/discriminator circuits. The principle is to remove the overlap between the output pulses from the Amptek circuits by adding a derandomizer between the Amptek circuits and the shift-register coincidence electronics. We implemented the derandomizer as an Actel programmable logic array; the derandomizer board is small and can be mounted in the high-voltage junction box with the Amptek circuits, if desired. Up to 32 Amptek circuits can be used with one derandomizer. The derandomizer has seven outputs: four groups of eight inputs, two groups of 16 inputs,more » and one group of 32 inputs. We selected these groupings to facilitate detector ring-ratio measurements. The circuit was tested with the five-ring research multiplicity counter, which has five output signals-one for each ring. The counter`s deadtime was reduced from 70 to 30 ns.« less
  • The operating temperatures of BF/sub 3/ proportional counters are said to be limited to approximately 100/sup 0/C for standard designs and 150/sup 0/C for special designs, but no paper was found which described the details of temperature dependence of thermal neutron pulse height distributions obtained from them. All the counters tested showed a decrease in the pulse heights and a broadening of the peak widths as the temperature increased. Thermal neutron counting rates in two types of the counters stayed unchanged up to 150/sup 0/C and in another type up to 100/sup 0/C. The pulse risetimes did not change appreciablymore » for the temperature change. This decrease in the pulse heights is in contrast with an increase in the pulse heights observed in He-3 proportional counters.« less