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Description and performance characteristics for the neutron Coincidence Collar for the verification of reactor fuel assemblies

Description: An active neutron interrogation method has been developed for the measurement of /sup 235/U content in fresh fuel assemblies. The neutron Coincidence Collar uses neutron interrogation with an AmLi neutron source and coincidence counting the induced fission reaction neutrons from the /sup 235/U. This manual describes the system components, operation, and performance characteristics. Applications of the Coincidence Collar to PWR and BWR types of reactor fuel assemblies are described.
Date: August 1, 1981
Creator: Menlove, H.O.
Partner: UNT Libraries Government Documents Department

Standardization of portable assay instrumentation: the neutron-coincidence tree

Description: Standardization of portable neutron assay instrumentation has been achieved by using the neutron coincidence technique as a common basis for a wide range of instruments and applications. The electronics originally developed for the High-Level Neutron Coincidence Counter has been adapted to both passive- and active-assay instrumentation for field verification of bulk plutonium, inventory samples, pellets, powders, nitrates, high-enriched uranium, and materials-testing-reactor, light-water-reactor, and mixed-oxide fuel assemblies. The family of detectors developed at Los Alamos National Laboratory and their performance under in-field conditions are described. 16 figures, 3 tables.
Date: January 1, 1983
Creator: Menlove, H.O.
Partner: UNT Libraries Government Documents Department

Manual for the Portable Handheld Neutron Counter (PHNC) for Neutron Survey and the Measurement of Plutonium Samples

Description: We have designed a portable neutron detector for passive neutron scanning measurement and coincidence counting of bulk samples of plutonium. The counter will be used for neutron survey applications as well as the measurement of plutonium samples for portable applications. The detector uses advanced design {sup 3}He tubes to increase the efficiency and battery operated shift register electronics. This report describes the hardware, performance, and calibration for the system.
Date: November 1, 2005
Creator: Menlove, H.O.
Partner: UNT Libraries Government Documents Department

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 effects of moisture biases for two PuO/sub 2/ sample sizes and a range of moisture levels from 0 to 9 wt %. Results of the calculations suggest a simple correction procedure for moisture bias that is effective from 0 to 3 wt % H/sub 2/O. The procedure requires that the moisture level in the sample be known before the coincidence measurement.
Date: January 1, 1987
Creator: Stewart, J.E. & Menlove, H.O.
Partner: UNT Libraries Government Documents Department

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 partially filled or contained reactor return material. The cylinders contained UF/sub 6/ with enrichments from 5.96% to 97.6%. Count times were 3 to 6 min depending on /sup 235/U mass. Samples ranged from below 1 kg to over 16 kg of /sup 235/U. Because the method relies primarily on fast neutron self-interrogation, complete sampling of the UF/sub 6/ takes place. This feature alleviates inhomogeneity problems and offers increased assurance of the presence of stated amounts of bulk fissile material as compared with current verification methods.
Date: January 1, 1983
Creator: Stewart, J.E. & Menlove, H.O.
Partner: UNT Libraries Government Documents Department

Passive neutron assay of heterogeneous waste drums using the segmented Add-a-Source method

Description: We have developed passive neutron detectors that include the Add-a-Source (AS) technique to improve the accuracy of the nondestructive assay of plutonium in large waste containers. We have improved the AS by incorporating multiple positions for the {sup 252}Cf source on the exterior of a 200-L drum. The multiple positions give a better coverage of the drum and have the effect of segmenting the matrix as a function of fill height. We have applied the multiposition AS to the assay of drums with heterogeneous matrix combinations of concrete, polyethylene, wood, paper, and metal. The measurement errors caused by the matrix significantly reduced by the AS technique and anomalous shielding material in the drum can be flagged for more detailed investigation.
Date: July 1, 1995
Creator: Menlove, H.O.
Partner: UNT Libraries Government Documents Department

International safeguards: experience and prospects

Description: IAEA safeguards have been applied to over 95% of the nuclear material and facilities outside of the nuclear weapon states. The present system of nonproliferation agreements implemented by IAEA safeguards likely will not be changed in the foreseeable future. Instruments used for nondestructive analysis are described: portable multichannel analyzer, high-level neutron coincidence counter, active well coincidence counter, and neutron coincidence collar. 7 figs. (DLC)
Date: January 1, 1982
Creator: Keepin, G.R. & Menlove, H.O.
Partner: UNT Libraries Government Documents Department

Channel coincidence counter: version 1

Description: A thermal neutron coincidence counter has been designed for the assay of fast critical assembly fuel drawers and plutonium-bearing fuel rods. The principal feature of the detector is a 7-cm by 7-cm by 97-cm detector channel, which provides a uniform neutron detection efficiency of 16% along the central 40 cm of the channel. The electronics system is identical to that used for the High-Level Neutron Coincidence Counter.
Date: June 1, 1980
Creator: Krick, M.S. & Menlove, H.O.
Partner: UNT Libraries Government Documents Department

High-level neutron coincidence counter (HLNCC): users' manual

Description: This manual describes the portable High-Level Neutron Coincidence Counter (HLNCC) developed at the Los Alamos Scientific Laboratory (LASL) for the assay of plutonium, particularly by inspectors of the International Atomic Energy Agency (IAEA). The counter is designed for the measurement of the effective /sup 240/Pu mass in plutonium samples which may have a high plutonium content. The following topics are discussed: principle of operation, description of the system, operating procedures, and applications.
Date: June 1, 1979
Creator: Krick, M.S. & Menlove, H.O.
Partner: UNT Libraries Government Documents Department

Experimental comparison of the active well coincidence counter with the random driver

Description: A direct comparison has been made between the IAEA Active Well Coincidence Counter (AWCC) and the LASL Random Driver at CMB-8. The comparison included an experimental evaluation of precision, counting rate, accuracy, penetrability, stability, and the effect of sample inhomogeneity. Samples used in the evaluation included highly enriched U/sub 3/O/sub 8/, U/sub 3/O/sub 8/ mixed with graphite, highly enriched uranium metal discs, and depleted uranium metal. These materials are typical of the samples of interest to the IAEA inspectors. It is concluded that the two instruments had very similar performance characteristics with the Random Driver giving better penetrability and the AWCC giving better stability.
Date: January 1, 1979
Creator: Menlove, H.O.; Ensslin, N. & Sampson, T.E.
Partner: UNT Libraries Government Documents Department

Birdcage neutron coincidence counter manual

Description: A thermal neutron coincidence counter has been constructed for the assay of fast critical assembly fuel plates stored in birdcages. Standard coincidence counting electronics are used. This manual describes the birdcage, the measurement system, and its performance characteristics. 3 refs.
Date: July 1, 1985
Creator: Krick, M.S.; Menlove, H.O. & Ramalho, A.
Partner: UNT Libraries Government Documents Department

Application of the active well coincidence counter to the measurement of uranium

Description: An Active Well Coincidence Counter has been developed to assay uranium fuel material in field inspection applications. The unit is used to measure bulk UO/sub 2/ samples, high enrichment uranium metals, LWR fuel pellets, and /sup 233/U-Th fuel materials which have very high gamma-ray backgrounds.
Date: January 1, 1980
Creator: Menlove, H.O.; Foley, J.E. & Bosler, G.E.
Partner: UNT Libraries Government Documents Department

Measurement system for high enriched spent fuel assemblies and waste solids

Description: A nondestructive neutron interrogation system, being developed to assay the /sup 235/U content in bulk waste solids and high enriched spent fuel assemblies, is described. The instrument will be used for both nuclear materials accountability and criticality control by the facility operator. A range of fissile contents varies from 0 to 400 g in the waste and from about 8 to 12 kg in the spent fuel elements. Measurements must be obtained in the presence of large neutron (1.2 x 10/sup 7/ n/s) and gamma (50,000 R/h) backgrounds. The system employs fast-neutron interrogation of the sample using a 5 mg /sup 252/Cf source combined with delayed neutron counting after the source is moved to storage. Preliminary monte carlo calculations indicate measurement precisions of better than +-5% (2sigma) are obtainable for waste loadings in excess of 200 g /sup 235/U.
Date: January 1, 1979
Creator: Eccleston, G.W.; Menlove, H.O. & Echo, M.W.
Partner: UNT Libraries Government Documents Department

Measurement of enriched uranium and uranium-aluminum fuel materials with the AWCC

Description: The active well coincidence counter (AWCC) was calibrated at the Chalk River Nuclear Laboratories (CRNL) for the assay of 93%-enriched fuel materials in three categories: (1) uranium-aluminum billets, (2) uranium-aluminum fuel elements, and (3) uranium metal pieces. The AWCC was a standard instrument supplied to the International Atomic Energy Agency under the International Safeguards Project Office Task A.51. Excellent agreement was obtained between the CRNL measurements and previous Los Alamos National Laboratory measurements on similar mockup fuel material. Calibration curves were obtained for each sample category. 2 refs., 8 figs., 15 tabs.
Date: May 1, 1985
Creator: Krick, M.S.; Menlove, H.O.; Zick, J. & Ikonomou, P.
Partner: UNT Libraries Government Documents Department

Experimental comparison of the active well coincidence counter with the random driver

Description: A direct comparison has been made between the IAEA Active Well Coincidence Counter (AWCC) and the CMB-8 Random Driver. The comparison included an experimental evaluation of precision, counting rate, accuracy, penetrability, stability, and the effect of sample inhomogeneity. Samples used in the evaluation included highly enriched U/sub 3/O/sub 8/, U/sub 3/O/sub 8/ mixed withe qgraphite, highly enriched uranium metal discs, and depleted uranium metal. These materials are typical of the samples of interest to the IAEA inspectors. It was concluded that the two instruments had very similar performance characteristics with the Random Driver giving better penetrability and the AWCC giving better stability.
Date: June 1, 1979
Creator: Menlove, H.O.; Ensslin, N. & Sampson, T.E.
Partner: UNT Libraries Government Documents Department

Plutonium Canister Counter operations and procedures manual

Description: A neutron coincidence counter has been designed for the measurement of plutonium powder contained in storage canisters. Each canister contains from one to four cans of mixed oxide. The neutron counter measures the spontaneous fission rate from the plutonium, and when this is combined with the plutonium isotopic ratios, the plutonium mass is determined. The system can accommodate plutonium loadings up to 8 kg, with 4 kg being a typical loading. This manual describes the system and its operation and gives performance and calibration parameters for typical applications. 5 refs., 10 figs., 8 tabs.
Date: February 1, 1986
Creator: Menlove, H.O.; Adams, E.L.; Dahn, E. & Ramalho, A.
Partner: UNT Libraries Government Documents Department

The development of {sup 3}He neutron detectors for applications in high level gamma-ray backgrounds

Description: To measure high-level-activity scrap and waste, it is necessary to use neutron detectors that are insensitive to the high gamma-ray background. We have developed a combination of {sup 3}He tubes and custom preamplifiers to provide the high efficiency associated with {sup 3}He detectors with good gamma-ray rejection. We have preamplifiers with short time constants in the signal processing to help separate the neutron signals from the slower risetime gamma signals. We have compared AMPTEK (A-111) preamplifiers with Precision Data Technology (PDT 110A) preamplifiers with experimental tests for gamma rejection and radiation damage. Hot cell radiation tests using a 4.5 Ci radium source were performed using {sup 10}B and {sup 3}He detectors to evaluate relative efficiency and the ability to separate neutrons and gamma rays. The AMPTEK A-111 and PDT-110A amplifiers were exposed to gamma doses between {approximately}0.1 R/h and 1500 R/h to observe where the gamma pileup would interfere with the neutron counting. The conclusion is that both amplifiers can operate in gamma fields up to {approximately}500 R/h with modest loss of neutron efficiency. This is valid for the case of only one {sup 3}He tube (30-cm active length) connected to a single amplifier. If an amplifier services multiple tubes or longer tubes, the gamma rejection will get worse. Studies are in progress to determine the lifetime of the amplifiers and {sup 3}He tubes in the high-radiation fields.
Date: December 1, 1995
Creator: Menlove, H.O. & Beddingfield, D.H.
Partner: UNT Libraries Government Documents Department

Design study for MOX fuel rod scanner for ATR fuel fabrication. Phase I: Design of active neutron scanner. Phase II: Design of passive neutron scanner. Phase III: Design of passive gamma-ray scanner

Description: An active neutron fuel-rod scanner has been designed for the assay of fissile materials in mixed oxide fuel rods. A {sup 252}Cf source is located at the center of the scanner very near the through-hole for the fuel rods. Spontaneous fission neutrons from the californium are moderated and induce fissions within the passing fuel rod. The rod continues past a combined gamma-ray and neutron shield where delayed gamma rays above 1 MeV are detected. The authors used the Monte Carlo neutron-photon (MCNP) code to design the scanner and review optimum materials and geometries. Applications of the rod scanner include accountability of fissile material for safeguards applications, quality control of the fissile content in a fuel rod, and the verification of reactivity potential for mixed oxide fuels. A passive neutron fuel-rod scanner has been designed for the assay of the plutonium in mixed oxide fuel rods. The {sup 240}Pu-effective is measured by counting the spontaneous fission neutrons using a high-efficiency thermal-neutron detector. This passive neutron detector would be combined with a high-resolution gamma-ray system (HRGS) measurement to obtain the total plutonium from the plutonium isotopic ratios. A passive gamma-ray scanner has been designed for the measurement of the {sup 241}Am and plutonium uniformity in mixed oxide fuel rods. The passive gamma-ray emissions from {sup 241}Am (60 keV) and plutonium (150-400 keV) are used to verify the unformity of the fuel enrichment zones and to check for any pellets that are out of specification. The fuel rod is moved through the interior of an NaI(Tl) or a bismuth germanate detector to measure the passive gamma-ray emissions. A tungsten sleeve collimator is used in the through-hole to improve the pellet-to-pellet spatial resolution. The same detector is used to verify the plutonium uniformity in the pellets with a 13-mm tungsten collimator. The low-resolution passive ...
Date: September 1, 1997
Creator: Griffith, G.W. & Menlove, H.O.
Partner: UNT Libraries Government Documents Department

Applications of curium measurements for safeguarding at large-scale reprocessing plants

Description: Safeguarding the plutonium passing through a large-scale reprocessing plant (such as one with 800 t of uranium per year) involves nondestructive assay measurements for plutonium at key points. The gamma-ray and neutron signals from the plutonium are generally hidden by the much larger backgrounds from fission products and actinides, so indirect measurements are routinely used. The intense neutron emission rate from spent fuel is from curium. In a spent fuel assembly at the head-end of a plant, the curium neutrons are used to deduce the amount of plutonium present. Coincidence and multiplicity counting are alternative ways to measure neutrons from spent fuel; they have advantages over total neutron counting in certain conditions and offer new opportunities for examining assemblies. New uses for measurements of curium`s neutrons are proposed to safeguard waste streams. From a year`s work at a large-scale plant, 4 to 7 kg of plutonium can remain in leached hulls and 4 to 22 kg of plutonium can remain in the vitrified high-level liquid waste. While the plutonium in these wastes has the safeguards advantage of being dilute, it is important to verify (a) that the many kilograms involved are in fact present and (b) that the declared masses are not higher than the actual amounts so that more concentrated plutonium cannot pass through the plant by masquerading as waste. Curium measurements on spent fuel assemblies, the accountability tank, and leached hulls would form a safeguards system around all the inputs and outputs of a plant`s head-end where the plutonium is always intimately mixed with the curium. A neutron measurement of the vitrified waste would help identify the presence of a diversion path upstream because essentially all of the curium measured in the spent fuel assemblies should also be found in the vitrified waste (on a batch basis). 7 ...
Date: August 1, 1997
Creator: Rinard, P.M. & Menlove, H.O.
Partner: UNT Libraries Government Documents Department

Application of curium measurements for safeguarding at reprocessing plants. Study 1: High-level liquid waste and Study 2: Spent fuel assemblies and leached hulls

Description: In large-scale reprocessing plants for spent fuel assemblies, the quantity of plutonium in the waste streams each year is large enough to be important for nuclear safeguards. The wastes are drums of leached hulls and cylinders of vitrified high-level liquid waste. The plutonium amounts in these wastes cannot be measured directly by a nondestructive assay (NDA) technique because the gamma rays emitted by plutonium are obscured by gamma rays from fission products, and the neutrons from spontaneous fissions are obscured by those from curium. The most practical NDA signal from the waste is the neutron emission from curium. A diversion of waste for its plutonium would also take a detectable amount of curium, so if the amount of curium in a waste stream is reduced, it can be inferred that there is also a reduced amount of plutonium. This report studies the feasibility of tracking the curium through a reprocessing plant with neutron measurements at key locations: spent fuel assemblies prior to shearing, the accountability tank after dissolution, drums of leached hulls after dissolution, and canisters of vitrified high-level waste after separation. Existing pertinent measurement techniques are reviewed, improvements are suggested, and new measurements are proposed. The authors integrate these curium measurements into a safeguards system.
Date: March 1, 1996
Creator: Rinard, P.M. & Menlove, H.O.
Partner: UNT Libraries Government Documents Department

Plutonium nitrate bottle counter manual

Description: A neutron coincidence counter has been designed for plutonium nitrate assay in large storage bottles. This assay system can be used in the reprocessing plant or in the nitrate-to-oxide conversion facility. The system is based on the family of neutron detectors similar to the high-level neutron coincidence counter. This manual describes the system and gives performance and calibration parameters for typical applications. 4 references, 11 figures, 9 tables.
Date: March 1, 1984
Creator: Menlove, H.O.; Adams, E.L. & Holbrooks, O.R.
Partner: UNT Libraries Government Documents Department