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Improvements to address issues leading to cancellation of the July 2014 Plutonium shot
Overview: A Pu shot scheduled for July 17 on the Z machine at SNL was cancelled this past summer. The LiF windows on the Pu targets were cracked during assembly because of configuration changes. Sandia management concluded that continuing with this experiment would present an unacceptable level of risk to the facility and possibly to the workers. In this report, we document the events that occurred which led to this decision and also present some lessons learned and plans and procedures put in place to reduce the likelihood of another such occurrence. The changes and this memorandum reflect the thinking of subject matter experts at both LANL and SNL. These changes represent significant improvements in both communication protocols and quality of the hardware assemblies.
LLNL Final Design for the Thermal Epithermal eXperiments (TEX) with ZPPR Plutonium/ Aluminum Plates with Polyethylene and Tantalum, IER 184
Abstract not provided.
Uranium and Plutonium Measurements by Isotopic Ratio Methods [Slides]
Abstract not provided.
Electronic Structure of Plutonium Materials from Photoemission
No abstract provided.
Experimental Design to Study Criticality Effects of Plutonium Aging
No abstract provided.
Lessons Learned in the Nuclear Criticality Safety Program at the LANL Plutonium Facility
No abstract provided.
Process Model of Plutonium Aqueous Recovery Operations in PF-4
No abstract provided.
Addendum to the Closure Report for Corrective Action Unit 412: Clean Slate I Plutonium Dispersion (TTR), Tonopah Test Range, Nevada
The Corrective Action Unit (CAU) 412 Closure Report (CR) was published in August 2016 (NNSA/NFO, 2016). The purpose of this addendum is to reference a letter from the U.S. Air Force (USAF) regarding the closure of CAU 412.
Excluding Benchmark Statistical Outliers in Nuclear Criticality Safety Validation: A Comparison Study of Upper Subcritical Limits for Plutonium Systems using Whisper-1.1
Neutron transport methods used to establish subcriticality require validation by comparison to critical experiments considered to be benchmarks. Whisper is a sensitivity/uncertainty analysis tool developed to assist with the task of validation in nuclear criticality safety. Details on the Whisper methodology can be found in References 1-3 on the MCNP® reference collection website at https://mcnp.lanl.gov. During the process of validation there can be cases where a benchmark experiment may be found to be a statistical outlier, in which the calculated k-effective value and the experiment k-effective value differ by an amount atypical for similar experiments. A methodology optionally employed by Whisper is the exclusion of statistical outliers based upon the iterative diagonal chi-squared statistical rejection technique. Alternatively, there is an option to include all benchmarks in the Whisper library collection, even those benchmarks found to be statistical outliers, when computing the bias, bias uncertainty and margin of subcriticality (MOS) leading to establishment of the baseline upper subcritical limit (USL). A comparison study has been done to compute USLs with and without statistical outliers in the Whisper benchmark collection to determine what effect rejection of statistical outliers has on the recommended USL. The results show little overall difference in the recommended baseline USLs developed by Whisper when excluding statistical outliers. Additionally, there does not appear to be a clear trend in predicting whether the baseline USL will be higher or lower when rejecting statistical outliers from the benchmark critical experiment collection used for validation.
Three New Lead (Pb) Benchmark Experiments Performed Using Plutonium and Different Enrichments of Uranium
This report discusses the following three new experiments containing lead: HEU/Pb, 'LEU"/Pb, and Pu/Pb.
The Effects on Non-Actinide Impurities from Aging Heat Source Plutonium in Stainless Steel Containers
Replacing the tantalum vials used for 238 PuO 2 sample collection and storage with stainless steel sample vials has several advantages. These advantages include a decreased cost, better material availability, and ease of fabrication. However, it must first be demonstrated that the alloying elements contained in stainless steel are not leached into the 238 PuO 2 such that product specifications are exceeded. In order to determine the suitability of stainless steel for this application, two seperate 238 PuO 2 fuel lots were investigated. These two fuel lots had been stored in stainless steel containers since their first sampling date of March of 2015, and were again sampled in February of 2019.
Particle size of several plutonium-238 oxide fuel samples from oxalate precipitation processes
Particle size of 238 PuO 2 powders is an important factor in determining the structural integrity of fuel pellets hot-pressed from the oxide powder. Understanding the evolution of particle size during aqueous processing is a first step in assuring control of particle size throughout the pellet formation process. Measured particle sizes are reported here, and discussed in terms of measured particle size changes occurring during calcining, observed aggregation of particulate, and particle morphology. Morphology and aggregation are related to surface energy, which governs granule formation and hot pressing behavior. Results are discussed in terms of reported dependence of oxide morphology on process temperatures and reagent concentrations.
Advanced Analysis of Plutonium: Pre- and Post-Detonation Scenarios
A Dissertation Presented for the Doctor of Philosophy Degree in Nuclear Engineering. Overarching research question: Do nuclear reactions in surface environment lead to distinctive chemical and isotopic signatures that are not present in nature? Testable hypothesis: Nuclear processes will lead to distinctive chemical and isotopic patterns of partitioning because high-temperature processes under high radiation rarely occur in natural surface environment.
Integrated Initiative for Plutonium and Actinide Missions Overview Presentation [Slides]
Abstract not provided.
Proliferation of Interstellar Plutonium into the Solar System
The astrophysical site of production of actinides in the galaxy has long been debated. Recently, neutron star mergers have been shown to produce actinides, though their contribution to the total amount is unknown. A second site, Type II supernovae, likely also contributes. The relative frequencies and production totals of these two sources lead to two very different and distinguishable predictions for the contemporary concentration of actinides in the local interstellar medium. This project was aimed at measuring live cosmological 244 Pu in lunar soil in order to infer the current interstellar concentration of Pu for comparison with the concentration inferred in the early solar system 4.5 billion years ago. This requires detecting Pu in lunar soil at a concentration of 10 4 – 10 5 atoms/g. We developed Pu separation and detection methodologies that exceed the current state of the art by ~100× and are now capable of making this extremely challenging measurement in principle. Based on that success we obtained a sample of lunar soil from the Apollo 17 mission. We have not yet analyzed it owing to difficulties in quantitatively and reproducibly transferring such minute quantities of Pu from the separation step to the analysis step. Once this technical issue is resolved we will be able to analyze the lunar soil.
Pit Disassembly and Processing/Oxidation Capacity (PDP) for Disposition of Surplus Plutonium at Los Alamos (FY2021 Workshop 1) [Slides]
This workshop will establish NNSA/LANL consensus on the planning basis for: updating the 2017 Life Cycle Cost Estimate (LCCE) pre-conceptual estimate by identifying the specific scope elements that will be included; identifying the specific scope elements that will be included in the Line Item project; and identifying the preliminary agenda items for the next PDP workshop.
Plutonium workers get a new level of education in the actinide mission
The Associate Laboratory Directorate for Weapons Production (ALDWP) and the National Security Education Center (NSEC) have teamed to develop a new Nuclear Enterprise Science and Technology (NEST) Academic Certificate program offered through the University of New Mexico – Los Alamos (UNM-LA). The pilot program, which virtually kicked off on January 19 even amidst snow closures, received accreditation by the State Higher Education Department (HED) in FY20 and is designed for LANL’s existing fissile material handler technician and technologist employee workforce. It will provide essential science, operations, and business education on all aspects of working in modern nuclear materials handling and processing facilities. The first course for the certificate program is called “Nuclear Facility Fundamentals.” A call for nominations went out to the directorate and a cohort of 15 individuals has been established to start the program.