16 Matching Results

Search Results

Advanced search parameters have been applied.

ASP Performance Assessment: Toward a Science-Based Understanding

Description: Several approaches to ASP performance can be contemplated. Perhaps the ideal would be a full cost/benefit analysis (which is probably utterly infeasible). Another approach would be a test-based figure-of-merit (FOM), this approach has the virtue of being quantitative and the challenge that each customer and application would be characterized by a different FOM. The alternative proposed here is an approach that uses information about the limits of detection of real instruments to support informed judgments.
Date: April 22, 2008
Creator: Sale, K
Partner: UNT Libraries Government Documents Department

APPLICATION OF NOVEL NEUTRON CORRELATION TECHNIQUES TO NUCLEAR MATERIAL MEASUREMENTS

Description: Confirmation of the fissile mass of a system containing plutonium can be done using neutron multiplicity techniques. This can be accomplished with a detector system that is smaller and less costly than a standard neutron multiplicity counter (NMC). Also the fissile mass of a uranium containing system can be confirmed by passive means. Recent work at Lawrence Livermore National Laboratory has demonstrated that simple slab neutron detectors and a novel approach to data acquisition and analysis can be used to make an accurate measurement of the mass of fissile materials. Purely passive measurement of kilogram quantities of highly enriched uranium (HEU) have also been shown to be feasible. In this paper we discuss calculational tools for assessing the application of these techniques to fissile material transparency regimes. The tools required to adequately model the correlations and their application will be discussed.
Date: June 9, 2006
Creator: Sale, K
Partner: UNT Libraries Government Documents Department

Primordial nucleosynthesis in inhomogeneous cosmologies:. cap omega. = 1 with baryonic dark matter

Description: We consider the constraints on ..cap omega.. from primordial nucleosynthesis in inhomogeneous cosmologies. We find that allowance for isothermal fluctuations significantly weakens the upper bound on the average value of ..cap omega.. derived from the standard big bang. Under the plausible additional assumption that regions of high baryon density are preferentially absorbed into cold dark matter, the constraints from primordial nucleosynthesis can be satisfied for large values of ..cap omega.., including ..cap omega.. = 1. 22 refs., 2 figs.
Date: September 1, 1986
Creator: Mathews, G.J. & Sale, K.E.
Partner: UNT Libraries Government Documents Department

A parameter study of the r process

Description: We consider the r-process production of actinide nuclei from a high temperature nucleon gas in a model which is most favorable for the r process. In this way, we can place upper limits on the value of the free electron fraction, Y/sub e/, of the material which experiences the r process. We find that for a broad range of initial nucleon densities, Y/sub e/ must be small (close to that for equilibrium neutron star matter). 11 refs., 2 figs.
Date: September 1, 1987
Creator: Sale, K.E. & Mathews, G.J.
Partner: UNT Libraries Government Documents Department

Neutron Correlations in Special Nuclear Materials, Experiments and Simulations

Description: Fissile materials emit neutrons with an unmistakable signature that can reveal characteristics of the material. We describe here measurements, simulations, and predicted signals expected and prospects for application of neutron correlation measurement methods to detection of special nuclear materials (SNM). The occurrence of fission chains in SNM can give rise to this distinctive, measurable time correlation signal. The neutron signals can be analyzed to detect the presence and to infer attributes of the SNM and surrounding materials. For instance, it is possible to infer attributes of an assembly containing a few kilograms of uranium, purely passively, using detectors of modest size in a reasonable time. Neutron signals of three radioactive sources are shown to illustrate the neutron correlation and analysis method. Measurements are compared with Monte Carlo calculations of the authenticated sources.
Date: June 5, 2007
Creator: Verbeke, J; Dougan, A; Nakae, L; Sale, K & Snyderman, N
Partner: UNT Libraries Government Documents Department

Results of LLNL investigation of NYCT data sets

Description: Upon examination we have concluded that none of the alarms indicate the presence of a real threat. A brief history and results from our examination of the NYCT ASP occupancy data sets dated from 2007-05-14 19:11:07 to 2007-06-20 15:46:15 are presented in this letter report. When the ASP data collection campaign at NYCT was completed, rather than being shut down, the Canberra ASP annunciator box was unplugged leaving the data acquisition system running. By the time it was discovered that the ASP was still acquiring data about 15,000 occupancies had been recorded. Among these were about 500 alarms (classified by the ASP analysis system as either Threat Alarms or Suspect Alarms). At your request, these alarms have been investigated. Our conclusion is that none of the alarm data sets indicate the presence of a real threat (within statistics). The data sets (ICD1 and ICD2 files with concurrent JPEG pictures) were delivered to LLNL on a removable hard drive labeled FOUO. The contents of the data disk amounted to 53.39 GB of data requiring over two days for the standard LLNL virus checking software to scan before work could really get started. Our first step was to walk through the directory structure of the disk and create a database of occupancies. For each occupancy, the database was populated with the occupancy date and time, occupancy number, file path to the ICD1 data and the alarm ('No Alarm', 'Suspect Alarm' or 'Threat Alarm') from the ICD2 file along with some other incidental data. In an attempt to get a global understanding of what was going on, we investigated the occupancy information. The occupancy date/time and alarm type were binned into one-hour counts. These data are shown in Figures 1 and 2.
Date: August 1, 2007
Creator: Sale, K; Harrison, M; Guo, M & Groza, M
Partner: UNT Libraries Government Documents Department

Overview and applications of the Monte Carlo radiation transport kit at LLNL

Description: Modern Monte Carlo radiation transport codes can be applied to model most applications of radiation, from optical to TeV photons, from thermal neutrons to heavy ions. Simulations can include any desired level of detail in three-dimensional geometries using the right level of detail in the reaction physics. The technology areas to which we have applied these codes include medical applications, defense, safety and security programs, nuclear safeguards and industrial and research system design and control. The main reason such applications are interesting is that by using these tools substantial savings of time and effort (i.e. money) can be realized. In addition it is possible to separate out and investigate computationally effects which can not be isolated and studied in experiments. In model calculations, just as in real life, one must take care in order to get the correct answer to the right question. Advancing computing technology allows extensions of Monte Carlo applications in two directions. First, as computers become more powerful more problems can be accurately modeled. Second, as computing power becomes cheaper Monte Carlo methods become accessible more widely. An overview of the set of Monte Carlo radiation transport tools in use a LLNL will be presented along with a few examples of applications and future directions.
Date: June 23, 1999
Creator: Sale, K E
Partner: UNT Libraries Government Documents Department

Radioactive ion beam research at LLNL

Description: In this paper we discuss efforts underway at LLNL to develop the technology for the measurement of proton and alpha-particle reactions with unstable nuclei which are necessary for understanding the nucleosynthesis and energy generation in hot hydrogen-burning environments. 16 refs., 5 figs.
Date: August 1, 1985
Creator: Mathews, G.J.; Bauer, R.W.; Haight, R.C. & Sale, K.E.
Partner: UNT Libraries Government Documents Department

Bayesian Processing for the Detection of Radioactive Contraband from Uncertain Measurements

Description: With the increase in terrorist activities throughout the world, the need to develop techniques capable of detecting radioactive contraband in a timely manner is a critical requirement. The development of Bayesian processors for the detection of contraband stems from the fact that the posterior distribution is clearly multimodal eliminating the usual Gaussian-based processors. The development of a sequential bootstrap processor for this problem is discussed and shown how it is capable of providing an enhanced signal for eventual detection.
Date: June 26, 2007
Creator: Candy, J V; Sale, K; Guidry, B; Breitfeller, E; Manatt, D & Chambers, D
Partner: UNT Libraries Government Documents Department

Radioactive ion beam research at Lawrence Livermore National Laboratory

Description: Several modifications and additions have been made to improve the radioactive beam facility at Livermore with the main aim of measuring the cross section for /sup 7/Be(p,..gamma..)/sup 8/B (which is important in determining the solar neutrino flux) and other reactions of astrophysical interest. The quadrupole sextuplet spectrometer has been upgraded by inserting an electrostatic deflection element near the midpoint and by installing a movable beam stop near the /sup 7/Be production target. These changes have allowed an improvement in the purity, and a large increase in the intensity, of the /sup 7/Be beam. Six large NaI(Tl) detectors and the gas cell from the OSU system along with its active and passive shielding have been incorporated into the Lawrence Livermore facility. True events are to be identified by a multiple coincidence. The first requirement is the detection of a ..gamma..-ray from the proton capture /sup 7/Be(p,..gamma..)/sup 8/B. After the candidate capture gamma is observed the /sup 8/B decay signature is required. This signature is a positron (from /sup 8/B ..-->.. /sup 8/Be* + e/sup +/ + ..nu..) along with the two ..cap alpha..'s from /sup 8/Be ..-->.. ..cap alpha.. + ..cap alpha.. observed in a CaF/sub 2/ detector into which the /sup 8/B have implanted. Also a detector telescope inside the gas cell monitors the incoming /sup 7/Be beam. The current status of the /sup 7/Be(p,..gamma..)/sup 8/B measurement is discussed.
Date: September 1, 1986
Creator: Sale, K.E.; Bauer, R.W.; Boyd, R.N.; Mathews, G.J.; Haight, R.C. & Corn, P.B.
Partner: UNT Libraries Government Documents Department

COG - Publicly Available Now to Criticality Safety Practitioners

Description: COG is a modern, general-purpose, high fidelity, multi-particle transport code with a long history of use in criticality safety studies at the Lawrence Livermore National Laboratory. This code was released to the Radiation Safety Information Computational Center (RSICC) for distribution to the public for the first time in January 2006. This paper provides an overview of the code development history, a description of features and capabilities of interest to the criticality safety practitioner, and our plans in support of the next public RSICC release.
Date: September 12, 2006
Creator: Buck, R M; Cullen, D E; Heinrichs, D P; Lent, E M; Nielsen, Jr, D E & Sale, K E
Partner: UNT Libraries Government Documents Department

Neutron Scattering Cross Sections for Natural Carbon in the Energy Range 2-133 keV

Description: Natural carbon is well known as reactor structure material and at the same time as one of the most important neutron scattering standards, especially at energies less than 2 MeV, where the neutron total and neutron scattering cross sections are essentially identical. The best neutron total cross section experimental data for natural carbon in the range 1-500 keV have uncertainties of 1-4%. However, the difference between these data and those based on R-matrix analysis and used in the ENDF libraries is evident, especially in the energy range 1-60 keV. Experimental data for total scattering neutron cross sections for this element in the energy range 1-200 keV are scanty. The use of the technique of neutron filtered beams developed at the Kyiv Research Reactor makes it possible to reduce the uncertainty of the experimental data and to measure the neutron scattering cross sections on natural carbon in the energy range 2-149 keV with accuracies of 3-6%. Investigations of the neutron scattering cross section on carbon were carried out using 5 filters with energies 2, 3.5, 24, 54 and 133 keV. The neutron scattering cross sections were measured using a detector system covering nearly 2{pi}. The detector consisting of {sup 3}He counters (58 units), was located just above the carbon samples. The {sup 3}He counters (CHM-37, 7 atm, diameter =18 mm, L=50 cm) are placed in five layers (12 or 11 in each layer). To determine the neutron scattering cross section on carbon the relative method of measurement was used. The isotope {sup 208}Pb was used as the standard. The normalization factor, which is a function of detector efficiency, thickness of the carbon samples, thickness of the {sup 208}Pb sample, geometry, etc., for each sample and for each filter energy has been obtained through Monte Carlo calculations by means of the MCNP4C ...
Date: June 14, 2006
Creator: Gritzay, O; Gnidak, M; Kolotyi, V; Korol, O; Razbudey, V; Venedyktov, V et al.
Partner: UNT Libraries Government Documents Department

Model-Based Detection of Radioactive Contraband for Harbor Defense Incorporating Compton Scattering Physics

Description: The detection of radioactive contraband is a critical problem is maintaining national security for any country. Photon emissions from threat materials challenge both detection and measurement technologies especially when concealed by various types of shielding complicating the transport physics significantly. This problem becomes especially important when ships are intercepted by U.S. Coast Guard harbor patrols searching for contraband. The development of a sequential model-based processor that captures both the underlying transport physics of gamma-ray emissions including Compton scattering and the measurement of photon energies offers a physics-based approach to attack this challenging problem. The inclusion of a basic radionuclide representation of absorbed/scattered photons at a given energy along with interarrival times is used to extract the physics information available from the noisy measurements portable radiation detection systems used to interdict contraband. It is shown that this physics representation can incorporated scattering physics leading to an 'extended' model-based structure that can be used to develop an effective sequential detection technique. The resulting model-based processor is shown to perform quite well based on data obtained from a controlled experiment.
Date: March 2, 2010
Creator: Candy, J V; Chambers, D H; Breitfeller, E F; Guidry, B L; Verbeke, J M; Axelrod, M A et al.
Partner: UNT Libraries Government Documents Department

Radioactive Threat Detection with Scattering Physics: A Model-Based Application

Description: The detection of radioactive contraband is a critical problem in maintaining national security for any country. Emissions from threat materials challenge both detection and measurement technologies especially when concealed by various types of shielding complicating the transport physics significantly. The development of a model-based sequential Bayesian processor that captures both the underlying transport physics including scattering offers a physics-based approach to attack this challenging problem. It is shown that this processor can be used to develop an effective detection technique.
Date: January 21, 2010
Creator: Candy, J V; Chambers, D H; Breitfeller, E F; Guidry, B L; Verbeke, J M; Axelrod, M A et al.
Partner: UNT Libraries Government Documents Department

Conversion-electron experiment to characterize the decay of the /sup 237/Np shape isomer

Description: Conversion electrons from the decay of low-lying levels of /sup 237/Np have been measured to detect the population of these levels by gamma-ray decay of the /sup 237/Np shape isomer. Analysis of the 208-keV transition L conversion-electron peak gives an upper limit of about 17 ..mu..b for the population of the 3/2/sup -/ 267-keV level in /sup 237/Np from the shape isomer decay. Model calculations are compared with the measured limit. Improvements are suggested for this experiment. 9 refs., 4 figs.
Date: December 8, 1987
Creator: Henry, E.A.; Becker, J.A.; Bauer, R.W.; Gardner, D.G.; Decman, D.J.; Meyer, R.A. et al.
Partner: UNT Libraries Government Documents Department

Benchmark field study of deep neutron penetration

Description: A unique benchmark neutron field has been established at the Lawrence Livermore National Laboratory (LLNL) to study deep penetration neutron transport. At LLNL, a tandem accelerator is used to generate a monoenergetic neutron source that permits investigation of deep neutron penetration under conditions that are virtually ideal to model, namely the transport of mono-energetic neutrons through a single material in a simple geometry. General features of the Lawrence Tandem (LATAN) benchmark field are described with emphasis on neutron source characteristics and room return background. The single material chosen for the first benchmark, LATAN-1, is a steel representative of Light Water Reactor (LWR) Pressure Vessels (PV). Also included is a brief description of the Little Boy replica, a critical reactor assembly designed to mimic the radiation doses from the atomic bomb dropped on Hiroshima, and its us in neutron spectrometry. 18 refs.
Date: June 10, 1991
Creator: Morgan, J.F.; Sale, K. (Lawrence Livermore National Lab., CA (USA)); Gold, R.; Roberts, J.H. & Preston, C.C. (Metrology Control Corp., Richland, WA (USA))
Partner: UNT Libraries Government Documents Department