Browsing by Subject "Plutonium"
Now showing 1 - 6 of 6
Results Per Page
Sort Options
Item Characterization of wound monitoring systems used to quantify and locate plutonium contamination(2009-05-15) Dimmerling, Paul JamesWhen an accident involving the possibility of a plutonium contaminated wound occurs, the contamination is often quantified using sodium iodide (NaI(Tl)) and high purity germanium (HPGe) detection systems. The NaI(Tl) system is used to quantify the amount of contamination, while HPGe is used to gauge the depth of contamination in the wound. Assessment of plutonium contaminated wounds is difficult due to the lowenergy and yield of the uranium L-shell x rays used for the measurement, which can be effected by source distance, shape, and tissue attenuation. These effects on wound counting systems used at Los Alamos National Laboratory (LANL) were characterized experimentally using common source shapes (disk, point, and line) and acrylic plastic as a tissue substitute. Experiments were conducted to characterize detector responses as a function of tissue attenuation, source distance, and source depth in tissue. The computer code MCNP5 was used to model both systems for wound counting and better examine angular displacement of a line source in tissue. The NaI(Tl) detector response was characterized using absolute detector efficiency for all experimental measurements. Measurements showed that the NaI(Tl) system is significantly effected by the source to detector position and depth in tissue. Characterization of the HPGe detection system was done utilizing the peak-to-peak ratio from the two low-energy x rays. HPGe peak-to-peak ratios were not affected by source to detector distance, but showed an increased response to source depth in tissue. MCNP results suggested that small incident angles from the plane of the detector face can cause significant effects on the response of both detectors. In summary, the response of both systems showed dependence on source geometry and depth of contamination in tissue. Correction values and uncertainties were determined based on these dependencies.Item Development of a portable neutron coincidence counter for field measurements of nuclear materials using the advanced multiplicity capabilities of MCNPX 2.5.F and the neutron coincidence point model(2009-05-15) Thornton, Angela LynnNeutron coincidence counting is an important passive Nondestructive Assay (NDA) technique widely used for qualitative and quantitative analysis of nuclear material in bulk samples. During the fission process, multiple neutrons are simultaneously emitted from the splitting nucleus. These neutron groups are often referred to as coincident neutrons. Because different isotopes possess different coincident neutron characteristics, the coincident neutron signature can be used to identify and quantify a given material. In an effort to identify unknown nuclear samples in field inspections, the Portable Neutron Coincidence Counter (PNCC) has been developed. This detector makes use of the coincident neutrons being emitted from a bulk sample. An in-depth analysis has been performed to establish whether the nuclear material in an unknown sample could be quantified with the accuracy and precision needed for safeguards measurements. The analysis was performed by comparing experimental measurements of PuO2 samples to the calculated output produced using MCNPX and the Neutron Coincidence Point Model. Based on the analysis, it is evident that this new portable system can play a useful role in identifying nuclear material for verification purposes.Item Safeguards for Uranium Extraction (UREX) +1a Process(2011-08-08) Feener, Jessica S.As nuclear energy grows in the United States and around the world, the expansion of the nuclear fuel cycle is inevitable. All currently deployed commercial reprocessing plants are based on the Plutonium - Uranium Extraction (PUREX) process. However, this process is not implemented in the U.S. for a variety of reasons, one being that it is considered by some as a proliferation risk. The 2001 Nuclear Energy Policy report recommended that the U.S. "develop reprocessing and treatment technologies that are cleaner, more efficient, less waste-intensive, and more proliferation-resistant." The Uranium Extraction (UREX+) reprocessing technique has been developed to reach these goals. However, in order for UREX+ to be considered for commercial implementation, a safeguards approach is needed to show that a commercially sized UREX+ facility can be safeguarded to current international standards. A detailed safeguards approach for a UREX+1a reprocessing facility has been developed. The approach includes the use of nuclear material accountancy (MA), containment and surveillance (C/S) and solution monitoring (SM). Facility information was developed for a hypothesized UREX+1a plant with a throughput of 1000 Metric Tons Heavy Metal (MTHM) per year. Safeguard goals and safeguard measures to be implemented were established. Diversion and acquisition pathways were considered; however, the analysis focuses mainly on diversion paths. The detection systems used in the design have the ability to provide near real-time measurement of special fissionable material in feed, process and product streams. Advanced front-end techniques for the quantification of fissile material in spent nuclear fuel were also considered. The economic and operator costs of these systems were not considered. The analysis shows that the implementation of these techniques result in significant improvements in the ability of the safeguards system to achieve the objective of timely detection of the diversion of a significant quantity of nuclear material from the UREX+1a reprocessing facility and to provide deterrence against such diversion by early detection.Item The simultaneous quantification of fissile U and Pu nuclides using delayed neutron activation analysis(2013-05) Kapsimalis, Roger James, 1985-; Landsberger, SheldonThe ability to quickly and accurately quantify fissile constituents in bulk materials remains essential to many aspects of nuclear forensics and for safeguarding nuclear materials and operations. This often entails the analysis of trace quantities of nuclear debris or effluents, and typically requires bulk sample digestion followed by actinide separation and mass spectrometry. Because destructive methods are time and labor intensive, efforts have been made to develop alternative nondestructive methods for this type of analysis. This work, performed at Oak Ridge National Laboratory at the High Flux Isotope Reactor (HFIR), seeks to utilize delayed neutron activation analysis on samples of interest containing multiple fissile constituents. Based on the variances in the fission product yields of individual fissile nuclides, this work utilizes methods of linear regression to derive a technique that allows for such analysis, forgoing chemical separation and using only a single irradiation and counting step.Item Stockpile reduction : the key to transition and infrastructure management at Los Alamos(2010-08) Gubernatis, David Charles; Nichols, Steven P.; Kautz, Douglas D.; Kornreich, Drew E.Since the end of World War II the United States has grown and maintained a stockpile of nuclear weapons in the interest of preserving world peace, and with the specific intent to provide unparalleled national security to its citizens. It was a commonly held view during this time that a large diverse stockpile was a fundamental key to national security. However, in today’s ever-changing environment, Los Alamos National Laboratory finds itself with an infrastructure unable to quickly adapt to new national security needs and threats. Burdened by the management of a Cold-War-era stockpile, nuclear operations at Los Alamos will benefit from a reduced stockpile initiative. Contrary to previously held beliefs, Los Alamos can be the prime beneficiary to such an approach, and use such a monumental shift in strategy to modernize infrastructure, revitalize critical staff, and effectively manage critical materials and facilities while simultaneously reducing waste and environmental impacts to better support national security needs.Item Thermal analysis of plutonium storage containers(Texas Tech University, 1999-08) Stevkovski, SasoExperimental results were obtained for four different values of heat generation rate (15, 20, 25 and 30W), and three different values of outside container temperature (20, 25 and 30°C). A constant temperature boundary condition was imposed on the outside surfaces of the container by circulating a constant temperature fluid. The purpose of the outside boundary condition was to enable basis for comparison between the experimental and numerical results. Heat generation caused by the decay of the plutonium was simulated by passing an electric current through a resistor placed in the center of a hollow bowling ball sized stainless steel sphere, referred to as the plutonium pit simulator. Experiments were performed with air, argon and helium as the backfill gases. The lowest temperatures were recorded with heHum as the backfill gas. The maximum temperatures registered in the ALR8(SI) container exceeded the safety Hmit of 60°C for most of the cases. According to the results, only using helium as a backfill gas can guarantee that the maximum temperature wiU not exceed the safety Hmit, for heat generation rates less than 20W. For higher heat generation rates, the limit will be exceeded for any tested backfill gas.