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Evaluation of the Argonne National Laboratory servo-controlled calorimeter system

Description: The control system of a replacement mode, twin-bridge, water-bath calorimeter originally built by Mound EG&G Applied Technologies was modified by Argonne National Laboratory. The calorimeter was upgraded with a PC-based computer control and data acquisition system. The system was redesigned to operate in a servo-control mode, and a preheater was constructed to allow pre-equilibration of samples. The instrument was sent to the Plutonium Facility at Los Alamos National Laboratory for testing and evaluation of its performance in the field using heat source standards and plutonium process materials. The important parameters for calorimeter operation necessary to satisfy the nuclear materials control and accountability requirements of the Plutonium Facility were evaluated over a period of several months. These parameters include calorimeter stability, measurement precision and accuracy, and average measurement time. The observed measurement precision and accuracy were found to be acceptable for most accountability measurements, although they were slightly larger than the values for calorimeters in routine use at the Plutonium Facility. Average measurement times were significantly shorter than measurement times for identical items in the Plutonium Facility calorimeters. Unexplained shifts in the baseline measurements were observed on numerous occasions. These shifts could lead to substantial measurement errors if they are not very carefully monitored by the operating facility. Detailed results of the experimental evaluation are presented in this report.
Date: January 1, 1997
Creator: Foster, L.A.
Partner: UNT Libraries Government Documents Department

Comparison testing of a mound calorimeter and a Savannah River Site calorimeter

Description: This paper describes the paired comparison testing of a Savannah River Site (SRS) calorimeter and a Mound calorimeter. Prior to this test, no offsite testing had been performed on an SRS calorimeter. The testing was performed at the Plutonium Facility of Los Alamos National Laboratory (LANL). The SRS calorimeter was designed, fabricated and delivered to LANL. The Mound calorimeter chosen for comparison was similar in well dimensions and located in the same room as the SRS calorimeter. There were three series of tests performed. First, twenty radiometric standard measurements were completed using two different standards. The second series of tests were dedicated to heat distribution measurements and the third series focused on measuring typical process samples.
Date: November 1, 1995
Creator: ReFalo, L.A. & Foster, L.A.
Partner: UNT Libraries Government Documents Department

Calorimetric assay of minor actinides

Description: This paper reviews the principles of calorimetric assay and evaluates its potential application to the minor actinides (U-232-4, Am-241, Am- 243, Cm-245, Np-237). We conclude that calorimetry and high- resolution gamma-ray isotopic analysis can be used for the assay of minor actinides by adapting existing methodologies for Pu/Am-241 mixtures. In some cases, mixtures of special nuclear materials and minor actinides may require the development of new methodologies that involve a combination of destructive and nondestructive assay techniques.
Date: December 31, 1996
Creator: Rudy, C.; Bracken, D.; Cremers, T.; Foster, L.A. & Ensslin, N.
Partner: UNT Libraries Government Documents Department

Detection and measurement of gamma-ray self-attenuation in plutonium residues

Description: A new method to correct for self-attenuation in gamma-ray assays of plutonium is presented. The underlying assumptions of the technique are based on a simple but accurate physical model of plutonium residues, particularly pyrochemical salts, in which it is assumed that the plutonium is divided into two portions, each of which can be treated separately from the standpoint of gamma-ray analysis: a portion that is in the form of plutonium metal shot; and a dilute portion that is mixed with the matrix. The performance of the technique is evaluated using assays of plutonium residues by tomographic gamma scanning at the Los Alamos Plutonium Facility. The ability of the method to detect saturation conditions is examined.
Date: September 1, 1996
Creator: Prettyman, T.H.; Foster, L.A. & Estep, R.J.
Partner: UNT Libraries Government Documents Department

Evaluation of the MADAM waste measurement system

Description: The Multiple Assay Dual Analysis Measurement (MADAM) system is a combined low-level and transuranic waste assay system. The system integrates commercially available Segmented Gamma Scanner (SGS) capability with a multienergy x-ray and gamma-ray analysis to measure these two waste forms. In addition, the system incorporates a small neutron slab detector to satisfy safeguards concerns and the capability for automated high-resolution gamma-ray analysis for isotope identification. Since delivery of the system to this facility, an evaluation of the waste measurement characteristics of the system has been conducted. A set of specially constructed NIST-traceable standards was fabricated for calibration and evaluation of the low-level waste (LLW) measurement system. The measurement characteristics of the LLW assay system were determined during the evaluation, including detection limits for all isotopes of interest, matrix attenuation effects, and detector response as a function of source position. Based on these studies, several modifications to the existing analysis algorithms have been performed, new correction factors for matrix attenuation have been devised, and measurement error estimates have been calculated and incorporated into the software.
Date: March 1995
Creator: Foster, L. A.; Wachter, J. R. & Hagan, R. C.
Partner: UNT Libraries Government Documents Department

TRANSFER OF EXCESS NUCLEAR MATERIAL FROM LOS ALAMOS TO SAVANNAH RIVER SITE FOR LONG-TERM DISPOSITION

Description: Los Alamos National Laboratory is preparing excess nuclear material for shipment to Savannah River Site (SRS) for final disposition. Prior to shipment the nuclear material will be stabilized and packaged to meet strict criteria. The criterion that must be met include: (1) the DOE stabilization, packaging and storage requirements for plutonium bearing materials, DOE-STD-3013, (2) shipping container packaging requirements, (3) SRS packaging and storage criteria, and (4) DOE Material Disposition criteria for either immobilization or MOX reactor fuel. Another issue in preparing for this transfer is the DOE certification of shipping containers and the availability of shipping containers. This transfer of the nuclear material is fully supported by the EM, DP and NN Sections of the DOE, as well as, by LANL and SRS, yet a strong collaboration is needed to meet all established requirements relating to stabilization, packaging, shipment, storage and final disposition. This paper will present the overall objectives, the issues and the planned strategy to accomplish this nuclear material transfer.
Date: June 1, 2001
Creator: Hoth, C. W.; Foster, L. A. & Yarbro, T. F.
Partner: UNT Libraries Government Documents Department

Non-Destructive Assay of Curium Contaminated Transuranic Waste Drums

Description: At the Plutonium Facility at Los Alamos National Laboratory, a series of non-destructive assays were performed on five transuranic waste (TRU) drums containing non-plutonium scrap metal that was potentially contaminated with weapons grade plutonium and trace quantities of curium. Typically, waste drums containing metal matrices are assayed for plutonium content using passive neutron coincidence counting techniques. The presence of trace quantities of Cm-244 prevents this type of analysis because of the strong coincidence signal created by spontaneous fission of Cm-244. To discriminate between the plutonium and curium materials present, an active neutron measurement technique was used. A Cf shuffler designed for measurement of uranium bearing materials was calibrated for plutonium in the active mode. The waste drums were then assayed for plutonium content in the shuffler using the active-mode calibration. The curium contamination levels were estimated from the difference between the active-mode measurement in the shuffler and a passive assay in a neutron coincidence counter. Far field gamma-ray measurements were made to identify additional radioactive contaminants and to corroborate the plutonium measurement results obtained from the active-mode assay. This report describes in detail the measurement process used for characterization of these waste drums. The measurement results and the estimated uncertainty will be presented.
Date: November 1, 1998
Creator: Foster, L.A.
Partner: UNT Libraries Government Documents Department

A Calibration to Predict Concentrations of Impurities in Plutonium Oxide by Prompt Gamma Analysis

Description: Prompt gamma (PG) analysis has been used to identify the presence of certain impurities in plutonium oxide, which has been stored in 3013 containers. A regression analysis was used to evaluate the trends between the count rates obtained from PG analysis and the concentration of the impurities in plutonium oxide samples measured by analytical chemistry techniques. The results of the analysis were used to obtain calibration curves, which may be used to predict the concentration of Al, Be, Cl, F, Mg, and Na in the 3013 containers. The scatter observed in the data resulted from several factors including sample geometry, error in sampling for chemical assay, statistical counting error, and intimacy of mixing of impurities and plutonium. Standards prepared by mixing plutonium oxide with CaF{sub 2}, NaCl, and KCl show that intimacy mixing and sampling error have the largest influence on the results. Although these factors are difficult to control, the calibrations are expected to yield semiquantitative results that are sufficient for the purpose of ordering or ranking.
Date: December 13, 2005
Creator: Narlesky, J.E.; Kelly, E.J. & Foster, L.A.
Partner: UNT Libraries Government Documents Department

NBC operation manual including the multi-position add-a-source function

Description: This manual describes the design modifications and operating characteristics of a 200-l-drum neutron coincidence counter. The counter has six shielded banks of {sup 3}He tubes and JSR-11 shift register coincidence electronics. The modified design has a counting efficiency of 19.3%. The neutron counter measures the spontaneous-fission rate from the plutonium, and when this is combined with the plutonium isotopic ratios, we can determine the plutonium mass. The system includes the new multi-position add-a-source (AS) technique that uses a small {sup 252}Cf source to determine the drum`s matrix perturbation to the plutonium assay. The {sup 252}Cf source is measured at three positions on the exterior of the drum to obtain the spatial distribution for the matrix correction. This manual gives the performance and calibration parameters. The matrix corrections by the AS technique are accurate to a few percent for typical applications.
Date: March 1, 1994
Creator: Menlove, H. O.; Foster, L. A. & Baca, J.
Partner: UNT Libraries Government Documents Department

Evaluation of low-level waste analysis using the MADAM system

Description: Previously, the important hardware features and capabilities for the Multiple Assay Dual Analysis Measurement (MADAM) system were reported. MADAM is a combined low-level and transuranic waste assay system. The system integrated commercially available Segmented Gamma Scanner (SGS) capability together with multienergy X-ray and gamma-ray analysis to measure these two waste forms. In addition, the system incorporated a small neutron slab detector to satisfy safeguards concerns and high resolution gamma-ray isotopics analysis proficiency. Since delivery of the system to this facility, an evaluation of its low-level waste measurement performance has been conducted using a set of specially constructed NIST-traceable standards. The evaluation studied existing analysis algorithms, matrix and attenuation effects, source position as a function of detector response, instrument stability, and sensitivity. Based on these studies, several modifications to the existing analysis algorithms have been performed, new correction factors for matrix attenuation have been devised, and measurement error estimates have been calculated and incorporated into the software. This report discusses the results of the evaluation program and the software modifications that have been developed.
Date: August 1, 1994
Creator: Foster, L. A.; Wachter, J. R. & Hagan, R. C.
Partner: UNT Libraries Government Documents Department

Installation and calibration of the oversized low-level package counter at Los Alamos National Laboratory

Description: With the importance of safeguards in production facilities, the Los Alamos National Laboratory Plutonium Facility has installed a neutron slab counter to facilitate the measurement of low-level waste packaged in 4 ft {times} 4 ft {times} 8 ft crates. In the past, oversized packages were measured by a gamma technique to assess holdup. The measurement was time-consuming and cumbersome, and the efficiency was questionable. The slab counter has alleviated the time and efficiency problems of the gamma measurement. The counter consists of four slab counters, each slab containing twenty 60-in. long helium-3 tubes embedded in 3.5 in. thick polyethylene slab. The detectors are shielded from room background by an additional 3.5 in. of polyethylene. The 4 ft 6 in. by 7 ft 6 in by 8 in. steel encased slabs are arranged around a 4 ft 6 in. {times} 22 ft conveyor system with two slabs on each side of the conveyor. The slabs are located on one end of the conveyor, with the end open to facilitate waste crate loading by forklift. The system was calibrated with a {sup 252}Cf source and placed in various locations throughout a mock waste crate. The mock calibration waste crate can be loaded with waste material to simulate waste crates generated in the facility.
Date: August 1, 1994
Creator: Long, S. M.; Langner, D. G.; Foster, L. A. & Malcom, J. E.
Partner: UNT Libraries Government Documents Department

Inventory verification measurements using neutron multiplicity counting

Description: This paper describes a series of neutron multiplicity measurements of large plutonium samples at the Los Alamos Plutonium Facility. The measurements were corrected for bias caused by neutron energy spectrum shifts and nonuniform multiplication, and are compared with calorimetry/isotopics. The results show that multiplicity counting can increase measurement throughput and yield good verification results for some inventory categories. The authors provide recommendations on the future application of the technique to inventory verification.
Date: December 31, 1998
Creator: Ensslin, N.; Foster, L.A.; Harker, W.C.; Krick, M.S. & Langner, D.G.
Partner: UNT Libraries Government Documents Department

Matrix Characterization of Plutonium Residues by Alpha-Particle Self-Interrogation

Description: Legacy plutonium residues often have inadequate item descriptions. Nondestructive characterization can help segregate these items for reprocessing or provide information needed for disposal or storage. Alpha particle-induced gamma-ray spectra contain a wealth of information that can be used for matrix characterization. We demonstrate how this information can be used for item identification. Gamma-ray spectra were recorded at the Los Alamos Plutonium Facility from a variety of legacy, plutonium-processing residues and product materials. The comparison and analysis of these spectra are presented.
Date: July 26, 1998
Creator: Prettyman, T.H.; Foster, L.A. & Staples, P.
Partner: UNT Libraries Government Documents Department

Neutron-based measurements for nondestructive assay of minor actinides produced in nuclear power reactors

Description: Because of their impacts on long-term storage of high-level radioactive waste and their value as nuclear fuels, measurement and accounting of the minor actinides produced in nuclear power reactors are becoming significant issues. This paper briefly reviews the commercial nuclear fuel cycle with emphasis on reprocessing plants and key measurement points therein. Neutron signatures and characteristics are compared and contrasted for special nuclear materials (SNMs) and minor actinides (MAs). The paper focuses on application of neutron-based nondestructive analysis (NDA) methods that can be extended for verification of MAs. We describe current IAEA methods for NDA of SNMs and extension of these methods to satisfy accounting requirements for MAs in reprocessing plant dissolver solutions, separated products, and high-level waste. Recommendations for further systems studies and development of measurement methods are also included.
Date: October 1, 1996
Creator: Stewart, J.E.; Eccleston, G.W.; Ensslin, N.; Cremers, T.L.; Foster, L.A.; Menlove, H.O. et al.
Partner: UNT Libraries Government Documents Department

Computer-determined assay time based on preset precision

Description: Most current assay systems for special nuclear materials (SNM) operate on the principle of a fixed assay time which provides acceptable measurement precision without sacrificing the required throughput of the instrument. Waste items to be assayed for SNM content can contain a wide range of nuclear material. Counting all items for the same preset assay time results in a wide range of measurement precision and wastes time at the upper end of the calibration range. A short time sample taken at the beginning of the assay could optimize the analysis time on the basis of the required measurement precision. To illustrate the technique of automatically determining the assay time, measurements were made with a segmented gamma scanner at the Plutonium Facility of Los Alamos National Laboratory with the assay time for each segment determined by counting statistics in that segment. Segments with very little SNM were quickly determined to be below the lower limit of the measurement range and the measurement was stopped. Segments with significant SNM were optimally assays to the preset precision. With this method the total assay time for each item is determined by the desired preset precision. This report describes the precision-based algorithm and presents the results of measurements made to test its validity.
Date: August 1, 1994
Creator: Foster, L. A.; Hagan, R.; Martin, E. R.; Wachter, J. R.; Bonner, C. A. & Malcom, J. E.
Partner: UNT Libraries Government Documents Department

Status of the WAND (Waste Assay for Nonradioactive Disposal) project as of July 1997

Description: The WAND (Waste Assay for Nonradioactive Disposal) system can scan thought-to-be-clean, low-density waste (mostly paper and plastics) to determine whether the levels of any contaminant radioactivity are low enough to justify their disposal in normal public landfills or similar facilities. Such a screening would allow probably at least half of the large volume of low-density waste now buried at high cost in LANL`s Rad Waste Landfill (Area G at Technical Area 54) to be disposed of elsewhere at a much lower cost. The WAND System consists of a well-shielded bank of six 5-in.-diam. phoswich scintillation detectors; a mechanical conveyor system that carries a 12-in.-wide layer of either shredded material or packets of paper sheets beneath the bank of detectors; the electronics needed to process the outputs of the detectors; and a small computer to control the whole system and to perform the data analysis. WAND system minimum detectable activities (MDAs) for point sources range from {approximately}20 dps for {sup 241}Am to approximately 10 times that value for {sup 239}Pu, with most other nuclides of interest being between those values, depending upon the emission probabilities of the radiations emitted (usually gamma rays and/or x-rays). The system can also detect beta particles that have energies {ge}100 keV, but it is not easy to define an MDA based on beta radiation detection because of the greater absorption of beta particles relative to photons in low Z-materials. The only radioactive nuclides not detectable by the WAND system are pure alpha emitters and very-low-energy beta emitters. At this time, operating procedures and quality assurance procedures are in place and training materials are available to operators. The system is ready to perform useful work; however, it would be both possible and desirable to upgrade the electronic components and the analysis algorithms.
Date: March 1998
Creator: Arnone, G. J.; Foster, L. A.; Foxx, C. L.; Hagan, R. C.; Martin, E. R.; Myers, S. C. et al.
Partner: UNT Libraries Government Documents Department