35 Matching Results

Search Results

Advanced search parameters have been applied.
in creator/contributor: "Stewart, J.E."  
Results: 1 - 24 next
open access

Direct fissile assay of highly enriched UF/sub 6/ using random self-interrogation and neutron coincidence response

Description: A new nondestructive method for direct assay of /sup 235/U mass contained in Model 5A uranium hexafluoride (UF/sub 6/) product storage cylinders has been successfully tested in the laboratory and under field conditions. The technique employs passive neutron self-interrogation and uses the ratio of coincidences-to-totals counts as a measure of bulk fissile mass. The accuracy of the method is 6.8% (1 sigma) based on field measurements of 44 Model 5A cylinders, 11 of which were either only partial… more
Date: January 1, 1983
Creator: Stewart, J. E. & Menlove, H. O.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Moisture corrections in neutron coincidence counting of PuO/sub 2/

Description: Passive neutron coincidence counting is capable of 1% assay accuracy for pure, well-characterized PuO/sub 2/ samples that contain plutonium masses from a few tens of grams to several kilograms. Moisture in the sample can significantly bias the assay high by changing the (..cap alpha..,n) neutron production, the sample multiplication, and the detection efficiency. Monte Carlo calculations and an analytical model of coincidence counting have been used to quantify the individual and cumulative eff… more
Date: January 1, 1987
Creator: Stewart, J. E. & Menlove, H. O.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Data analysis for neutron monitoring in an enrichment facility. [To detect high-enriched uranium production]

Description: Area monitoring of neutron radiation to detect high-enriched uranium production is a potential strategy for inspector verification of operations in the cascade area of a centrifuge enrichment facility. This paper discusses the application of statistical filtering and hypothesis testing procedures to experimental data taken in an enrichment facility. The results demonstrate that these data analysis methods can enhance detection of facility misoperation by neutron monitoring.
Date: January 1, 1982
Creator: Markin, J.T.; Stewart, J.E. & Goldman, A.S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Application of detailed fission-product decay gamma spectra in the calculation of photoneutron spectra from D(. gamma. ,n) reactions in PWR fuel

Description: The magnitude, average neutron energy, and spectrum of the photoneutron source in a PWR fuel is calculated for shutdown times to 100 y using CINDER radionuclide inventory calculations, ENDF/B-V ..gamma.. line decay spectra, MCNP ..gamma.. transport calculations, and PHONEX D(..gamma..,n) reaction physics calculations.
Date: January 1, 1985
Creator: Wilson, W. B.; Stewart, J. E.; England, T. R. & Perry, R. T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

NDA (nondestructive assay) training for new IAEA inspectors at Los Alamos

Description: The history of the evolution of nondestructive assay (NDA) training for international inspectors at Los Alamos is described. The current NDA training course for International Atomic Energy Agency inspectors is presented in terms of structure, content, and rationale. Results of inspector measurement exercises are given along with projections for future developments in NDA inspector training. 3 refs.
Date: January 1, 1987
Creator: Stewart, J. E.; Reilly, T. D.; Belew, W.; Woelfl, E. & Fager, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Calibration parameters from Monte Carlo simulations for neutron coincidence assay of MOX (mixed oxide) fuel elements: A substitute for standards

Description: Results from application of a calculational model for the two- parameter (singles and doubles) passive neutron coincidence assay of finished Fast Breeder Reactor (FBR) subassemblies are compared with calibration measurements. Two assay instruments are considered; the Universal Fast Breeder Reactor Subassembly Counter (UFBC) and the Capsule Counter installed at the Japanese Plutonium Fuel Production Facility (PFPF). In the case of US Fast Flux Test Facility (FFTF) fuel, the absolute ratio of cal… more
Date: January 1, 1989
Creator: Stewart, J. E.; Ferran, R. R.; Simmonds, S. M. & Menlove, H. O.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Methods of Verification, Accountability and Control of Special Nuclear Material

Description: This session demonstrates nondestructive assay (NDA) measurement, surveillance and analysis technology required to protect, control and account (MPC and A) for special nuclear materials (SNM) in sealed containers. These measurements, observations and analyses comprise state-of-the art, strengthened, SNM safeguards systems. Staff member specialists, actively involved in research, development, training and implementation worldwide, will present six NDA verification systems and two software tools … more
Date: May 3, 1999
Creator: Stewart, J. E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Development of an integrated, unattended assay system for LWR-MOX fuel pellet trays

Description: Four identical unattended plutonium assay systems have been developed for use at the new light-water-reactor mixed oxide (LWR-MOX) fuel fabrication facility at Hanau, Germany. The systems provide quantitative plutonium verification for all MOX pellet trays entering or leaving a large, intermediate store. Pellet-tray transport and storage systems are highly automated. Data from the ``I-Point`` (information point) assay systems will be shared by the Euratom and International Atomic Energy Agency … more
Date: August 1, 1994
Creator: Stewart, J. E.; Hatcher, C. R. & Pollat, L. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Guide to nondestructive assay standards: Preparation criteria, availability, and practical considerations

Description: For certification and measurement control, nondestructive assay (NDA) instruments and methods used for verification measurement of special nuclear materials (SNMs) require calibrations based on certified reference materials (CRMs), or working reference materials (WRMs), traceable to the national system of measurements, and adequately characteristic of the unknowns. The Department of Energy Office of Safeguards and Security is sponsoring production of a comprehensive guide to preparation of NDA … more
Date: October 1, 1997
Creator: Stewart, J.E.; Hsue, S.T. & Sampson, T.E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Energy dependent bias in plutonium verification measurements using thermal neutron multiplicity counters

Description: 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 p… more
Date: October 1, 1997
Creator: Krick, M. S.; Langner, D. G. & Stewart, J. E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Preparation of Pure Plutonium Metal Standards for Nondestructive Assay

Description: To calibrate neutron coincidence and neutron multiplicity counters for passive assay of plutonium, certain detector parameters must be determined. When one is using small plutonium metal samples, biases can be introduced from non-zero multiplication and impurities. This paper describes preparing small, pure plutonium metal standards with well-known geometries to enable accurate multiplication corrections and with acceptably low levels of impurities. To minimize multiplication, these standards a… more
Date: November 1, 2000
Creator: Hsue, S. -T.; Stewart, J. E. & Krick, M. S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Confirmatory measurements of UF/sub 6/ using the neutron self-interrogation method

Description: A passive neutron counting method has been developed for measurement of the /sup 235/U mass in Model 5A cylinders of UF/sub 6/. The unique neutronic properties of UF/sub 6/ containing highly enriched uranium (HEU) permit /sup 235/U assay using only passive neutron counting. The sample effectively assays itself by self-interrogation. Shipped from enrichment plants and received at fuel fabrication and conversion facilities, 5A UF/sub 6/ cylinders hold up to approx.17 kg of /sup 235/U each. Field … more
Date: January 1, 1985
Creator: Stewart, J. E.; Ensslin, N.; Menlove, H. O.; Cowder, L. R. & Polk, P. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

The state-of-the-art of thermal neutron multiplicity counting

Description: Neutron multiplicity counting is a maturing technology. It has been implemented at many facilities to address the increasing need to rapidly measure impure plutonium bearing materials. At Hanford Site and Rocky Flats Environmental Technology Site, multiplicity counting has also been used with excellent results by the International Atomic Energy Agency to verify excess plutonium inventories now under their safeguards. Neutron multiplicity counting as currently implemented, however, will not addr… more
Date: November 1, 1997
Creator: Langner, D. G.; Krick, M. S.; Stewart, J. E. & Ensslin, N.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Neutron multiplicity assay of impure materials using four different neutron counters

Description: During an advanced IAEA inspector training course given at Los Alamos in November, 1997, the opportunity existed for an intercomparison study of various neutron detectors to quantify measurement performance using pure and impure plutonium oxide and mixed uranium-plutonium oxide (MOX) items. Because of the cost of counters designed specifically for multiplicity analysis, it was desired to explore the limits of other, less costly and less efficient detectors. This paper presents and intercompares… more
Date: December 1, 1998
Creator: Stewart, J. E.; Langner, D. G. & Wenz, T. R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Design of standards for nondestructive assay of special nuclear material

Description: Nondestructive assay (NDA) of special nuclear material (SNM) involves a variety of measurement techniques, instruments, and nuclear materials. High-quality measurements require well-characterized SNM standards that represent the expected range of mass, chemical composition, and physical properties of the SNM to be measured. Due to the very limited commercial availability of NDA standards, facilities must usually produce their own standards, both to meet their specific measurement needs and to c… more
Date: May 1997
Creator: Smith, H. A., Jr.; Stewart, J. E. & Ruhter, W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Advances in passive neutron instruments for safeguards use

Description: Passive neutron and other nondestructive assay techniques have been used extensively by the International Atomic Energy Agency to verify plutonium metal, powder, mixed oxide, pellets, rods, assemblies, scrap, and liquids. Normally, the coincidence counting rate is used to measure the {sup 240}Pu-effective mass and gamma-ray spectrometry or mass spectrometry is used to verify the plutonium isotopic ratios. During the past few years, the passive neutron detectors have been installed in plants and… more
Date: February 1, 1994
Creator: Menlove, H. O.; Krick, M. S.; Langner, D. G.; Miller, M. C. & Stewart, J. E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

A two-fold reduction in measurement time for neutron assay: Initial tests of a prototype dual-gated shift register

Description: Neutron coincidence counting (NCC) is used routinely around the world for nondestructive mass assay of uranium and plutonium in many forms, including waste. Compared with other methods, NCC is generally the most flexible, economic, and rapid. Many applications of NCC would benefit from a reduction in counting time required for a fixed random error. We have developed and tested the first prototype of a dual- gated, shift-register-based electronics unit that offers the potential of decreased meas… more
Date: September 1, 1996
Creator: Stewart, J.E.; Bourret, S.C.; Krick, M.S.; Hansen, W.J. & Harker, W.C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Passive neutron assay of irradiated nuclear fuels

Description: Passive neutron assay of irradiated nuclear fuel has been investigated by calculations and experiments as a simple, complementary technique to the gamma assay. From the calculations it was found that the neutron emission arises mainly from the curium isotopes, the neutrons exhibit very good penetrability of the assemblies, and the neutron multiplication is not affected by the burnup. From the experiments on BWR and PWR assemblies, the neutron emission rate is proportional to burnup raised to 3.… more
Date: February 1, 1979
Creator: Hsue, S. T.; Stewart, J. E.; Kaieda, K.; Halbig, J. K.; Phillips, J. R.; Lee, D. M. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Continuous remote unattended monitoring for safeguards data collection systems

Description: To meet increased inspection requirements, unattended and remote monitoring systems have been developed and installed in several large facilities to perform safeguards functions. These unattended monitoring systems are based on instruments originally developed for traditional safeguards and the domestic nuclear industry to nondestructively assay nuclear materials. Through specialized measurement procedures, these instruments have been adapted to be unattended monitors. This paper defines the pa… more
Date: February 1, 1994
Creator: Klosterbuer, S. F.; Halbig, J. K.; Harker, W. C.; Menlove, H. O.; Painter, J. A. & Stewart, J. E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Guide to nondestructive assay standards: Preparation criteria, availability, and practical considerations

Description: For certification and measurement control, nondestructive assay (NDA) instruments and methods used for verification measurements of special nuclear materials (SNMs) require calibrations based on certified reference materials (CRMs), or working reference materials (WRMs), traceable to the national system of measurements, and adequately characteristic of the unknowns. The Department of Energy Office of Safeguards and Security is sponsoring production of a comprehensive guide to preparation of NDA… more
Date: October 1, 1997
Creator: Hsue, S. T.; Stewart, J. E.; Sampson, T. E.; Butler, G. W.; Rudy, C. R. & Rinard, P. M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
Back to Top of Screen