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Title: Measurement and Analysis System for the Identification of Shielded Neutron Sources

Abstract

Accurate identification of radioactive materials is essential in areas such as nuclear nonproliferation, international safeguards, nuclear material control and accountability, and national security. Recently, a new application of a technique that acquires neutron pulse-height spectra using a liquid scintillation detector, a digitizer, and an optimized pulse shape discrimination technique was proposed. The method can be used for accurate identification of neutron sources such as Cf-252, Am-Be, and Am-Li. All these sources were investigated in combination with several shielding blocks made of polyethylene and lead. From the results it is apparent that source identification is possible by the data inspection of the measured pulse-height distributions. The general slope of the distributions can be used for the source identification and all sources tested can be accurately identified. All measured pulse-height distributions were also compared to distributions simulated with the MCNP-PoliMi code and very good agreement was achieved.

Authors:
 [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
Work for Others (WFO)
OSTI Identifier:
966087
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: IEEE, Honolulu, HI, USA, 20071031, 20071116
Country of Publication:
United States
Language:
English
Subject:
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE; LIQUID SCINTILLATION DETECTORS; NATIONAL SECURITY; NEUTRON SOURCES; NEUTRONS; POLYETHYLENES; PROLIFERATION; RADIOACTIVE MATERIALS; SAFEGUARDS; SHAPE; SHIELDING; SPECTRA

Citation Formats

Flaska, Marek, and Pozzi, Sara A. Measurement and Analysis System for the Identification of Shielded Neutron Sources. United States: N. p., 2007. Web.
Flaska, Marek, & Pozzi, Sara A. Measurement and Analysis System for the Identification of Shielded Neutron Sources. United States.
Flaska, Marek, and Pozzi, Sara A. Mon . "Measurement and Analysis System for the Identification of Shielded Neutron Sources". United States. doi:.
@article{osti_966087,
title = {Measurement and Analysis System for the Identification of Shielded Neutron Sources},
author = {Flaska, Marek and Pozzi, Sara A},
abstractNote = {Accurate identification of radioactive materials is essential in areas such as nuclear nonproliferation, international safeguards, nuclear material control and accountability, and national security. Recently, a new application of a technique that acquires neutron pulse-height spectra using a liquid scintillation detector, a digitizer, and an optimized pulse shape discrimination technique was proposed. The method can be used for accurate identification of neutron sources such as Cf-252, Am-Be, and Am-Li. All these sources were investigated in combination with several shielding blocks made of polyethylene and lead. From the results it is apparent that source identification is possible by the data inspection of the measured pulse-height distributions. The general slope of the distributions can be used for the source identification and all sources tested can be accurately identified. All measured pulse-height distributions were also compared to distributions simulated with the MCNP-PoliMi code and very good agreement was achieved.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • In recent years there has been a trend towards storage of Irradiated Nuclear Fuel (INF) in dry conditions rather than in underwater environments. At the same time, the Department of Energy (DOE) has begun encouraging custodians of INF to perform measurements on INF for which no recent fissile contents measurement data exists. INF, in the form of spent fuel from Experimental Breeder Reactor 2 (EBR-II), has been stored in close-fitting, dry underground storage locations at the Radioactive Scrap and Waste Facility (RSWF) at Argonne National Laboratory-West (ANL-W) for many years. In Fiscal Year 2000, funding was obtained from the DOEmore » Office of Safeguards and Security Technology Development Program to develop and prepare for deployment a Shielded Measurement System (SMS) to perform fissile content measurements on INF stored in the RSWF. The SMS is equipped to lift an INF item out of its storage location, perform scanning neutron coincidence and high-resolution gamma-ray measurements, and restore the item to its storage location. The neutron and gamma-ray measurement results are compared to predictions based on isotope depletion and Monte Carlo neutral-particle transport models to provide confirmation of the accuracy of the models and hence of the fissile material contents of the item as calculated by the same models. This paper describes the SMS and discusses the results of the first calibration and validation measurements performed with the SMS.« less
  • In recent years there has been a trend towards storage of Irradiated Nuclear Fuel (INF) in dry conditions rather than in underwater environments. At the same time, the Department of Energy (DOE) has begun encouraging custodians of INF to perform measurements on INF for which no recent fissile contents measurement data exists. INF, in the form of spent fuel from Experimental Breeder Reactor 2 (EBR-II), has been stored in close-fitting, dry underground storage locations at the Radioactive Scrap and Waste Facility (RSWF) at Argonne National Laboratory-West (ANL-W) for many years. In Fiscal Year 2000, funding was obtained from the DOEmore » Office of Safeguards and Security Technology Development Program to develop and prepare for deployment a Shielded Measurement System (SMS) to perform fissile content measurements on INF stored in the RSWF. The SMS is equipped to lift an INF item out of its storage location, perform scanning neutron coincidence and high-resolution gamma-ray measurements, and restore the item to its storage location. The neutron and gamma-ray measurement results are compared to predictions based on isotope depletion and Monte Carlo neutral-particle transport models to provide confirmation of the accuracy of the models and hence of the fissile material contents of the item as calculated by the same models. This paper describes the SMS and discusses the results of the first calibration and validation measurements performed with the SMS.« less
  • A portable measurement system consisting of a personal computer used as a Fourier analyzer and three detection channels (with associated electronics that provide the signals to analog-to-digital (A/D) convertors) has been assembled to measure subcriticality by the /sup 252/Cf-source-driven neutron noise analysis method. The /sup 252/Cf-source-driven neutron noise analysis method for obtaining the subcritical neutron multiplication factor of a configuration of fissile material requires measurement of the frequency-dependent cross-power spectral density (CPSD), G/sub 23/(..omega..), between a pair of detectors (Nos. 2 and 3) located in or near the fissile material and CPSDs G/sub 12/(..omega..) and G/sub 13/(..omega..) between these samemore » detectors and a source of neutrons emanating from an ionization chamber (No. 1) containing /sup 252/Cf, also positioned in or near the fissile material. The auto-power spectral density (APSD), G/sub 11/(..omega..), of the source is also required. A particular ratio of spectral densities, G/sub 12//sup */G/sub 13//G/sub 11/G/sub 23/ (/sup */ denotes complex conjugation), is then formed. This ratio is related to the subcritical neutron multiplication factor and is independent of detector efficiencies.« less
  • A portable measurement system consisting of a personal computer used as a Fourier analyzer and three detection channels (with associated electronics that provide the signals to analog-to-digital (A/D) convertors) has been assembled to measure subcriticality by the /sup 252/Cf-source-driven neutron noise analysis method. 8 refs.
  • A portable system has been assembled that is capable of measuring the subcriticality of fissile materials using the /sup 252/CF-source-driven neutron noise analysis method. The measurement system consists of a parallel-plate ionization chamber containing /sup 252/CF, two /sup 3/He proportional counters with their associated electronics, and a small computer containing anti-aliasing filters and A/D convertors. The system Fourier analyzes the digitized data and forms the appropriate auto and cross-power spectral densities. These spectra are used to form a ratio of spectral densities, G/sub 12/G/sub 13//G/sub 11/G/sub 23/, where 1 refers to the ionization chamber, and 2 and 3 refer tomore » the /sup 3/He counters, from which subcriticality can be determined. The chamber and detectors are located appropriately near the fissile material. The system is capable of sampling signals at rates of up to 80 kHz and processing these data at rates of 2 kHz to form the appropriate spectra. The presently configured system is a two-channel system, hence the measurement of G/sub 12/, G/sub 13/, and G/sub 23/ must be done sequentially before the ratio of spectral densities is obtained. Future improvements of the system will allow simultaneous measurement of all spectra and will further reduce size, thereby enhancing portability. This measurement system can provide reliable, cost effective, and convenient determination of the subcriticality of a wide variety of fissile materials and moderators.« less