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At least 487 records · Page 27

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DOE OSTI2017

Plutonium Purification by Anion Exchange for Mark-18A Target Processing

The Mark-18A (Mk-18A) program was established to preserve the unique materials found in Mk-18A targets for future research and development activity within the Department of Energy or other U.S. government agencies. Some of the unique, high-valued materials include but are not limited to plutonium-244, heavy curium, americium-241, and californium. The Savannah River Site has sixty-five (65) Mk-18A targets available for recovery. Mk-18A targets will be removed from confinement, dissolved, chemically separated, and calcined to a stable oxide for transport to Oak Ridge National Laboratory (ORNL). The baseline flowsheet is patterned after the ORNL flowsheet, but adapted to the needs and capabilities of facilities at the Savannah River National Laboratory. The primary method for chemical separation of Pu from the other components of the targets is anion exchange using the Reillex™ HPQ resin. Although data exist in the literature for predicting the behavior of Mk-18A dissolver solutions on the Reillex™ resin, it was determined that the presence of a range of dissolved metals might negatively affect the resin performance, resulting in increased 244 Pu losses or poorer product quality.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2025

Closure Report for Corrective Action Unit 366: Area 11 Plutonium Valley Dispersion Sites, Nevada National Security Site, Nevada with ROTC 1

This Closure Report presents information supporting closure of Corrective Action Unit (CAU) 366, Area 11 Plutonium Valley Dispersion Sites, and provides documentation supporting the completed corrective actions and confirmation that closure objectives for CAU 366 were met. CAU 366 consists of the following six Corrective Action Sites (CASs), located in Area 11 of the Nevada National Security Site: • CAS 11-08-01, Contaminated Waste Dump #1 • CAS 11-08-02, Contaminated Waste Dump #2 • CAS 11-23-01, Radioactively Contaminated Area A • CAS 11-23-02, Radioactively Contaminated Area B • CAS 11-23-03, Radioactively Contaminated Area C • CAS 11-23-04, Radioactively Contaminated Area D

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2026

Integral Experiment Execution of Thermal or Epithermal eXperiments using Plutonium with Polyethylene and Iron, IER 519, TEX-Hanford (-Iron), CED-3b

This report documents the execution of experiments and measurements for IER 519, Thermal/Epithermal eXperiments (TEX) for Hanford applications, using plutonium Zero Power Physics Reactor (ZPPR) plates moderated by interstitial polyethylene and iron (Fe) absorber plates. Initial hand stack, mass, and dimensional measurements were performed in July 2025. The experiments were completed over three weeks from December 2025 to January 2026 at the National Criticality Experiments Research Center (NCERC) at the Nevada National Security Sites (NNSS). All photos and critical data were provided by NCERC and experimenters in LANL’s NEN-2.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2012

Sampling and Analysis of the Headspace Gas in 3013 Type Plutonium Storage Containers at Los Alamos National Laboratory

Department of Energy (DOE) sites have packaged approximately 5200 3013 containers to date. One of the requirements specified in DOESTD-3013, which specifies requirements for packaging plutonium bearing materials, is that the material be no greater than 0.5 weight percent moisture. The containers are robust, nested, welded vessels. A shelf life surveillance program was established to monitor these cans over their 50 year design life. In the event pressurization is detected by radiography, it will be necessary to obtain a head space gas sample from the pressurized container. This technique is also useful to study the head space gas in cans selected for random destructive evaluation. The atmosphere is sampled and the hydrogen to oxygen ratio is measured to determine the effects of radiolysis on the moisture in the container. A system capable of penetrating all layers of a 3013 container assembly and obtaining a viable sample of the enclosed gas and an estimate of internal pressure was designed.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2012

Measurements at Los Alamos National Laboratory Plutonium Facility in Support of Global Security Mission Space

The Los Alamos National Laboratory Plutonium Facility at Technical Area (TA) 55 is one of a few nuclear facilities in the United States where Research & Development measurements can be performed on Safeguards Category-I (CAT-I) quantities of nuclear material. This capability allows us to incorporate measurements of CAT-IV through CAT-I materials as a component of detector characterization campaigns and training courses conducted at Los Alamos. A wider range of measurements can be supported. We will present an overview of recent measurements conducted in support of nuclear emergency response, nuclear counterterrorism, and international and domestic safeguards. This work was supported by the NNSA Office of Counterterrorism.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2016

Importance of Plutonium Turnings in Criticality Safety

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2022

Rossi-α Measurements on a System Consisting of Weapons Grade Plutonium Moderated by Polyethylene

A critical experiment was performed on the Planet assembly to provide nuclear data in a thermal neutron spectrum, in particular to provide experimental data to help validate thermal scattering laws for polyethylene. The fuel consisted of layers of weapons grade plutonium plates that were moderated and reflected by various thicknesses of high density polyethylene. Rossi-α measurements were performed on a slightly modified configuration from the configuration used for the critical measurements. The Rossi-α measurement techniques are discussed and results are presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2023

Verifying MCNP Models of the TEX High 240 Plutonium Benchmark

Computational modeling programs are invaluable tools that allow us to understand systems, safely develop new processes, and make reliable predictions about future designs. However, the effectiveness of these codes is limited by the degree to which their parameters match the real world. In the field of nuclear engineering, cross section data is one of these vital parameters. Accurate cross section data on important fissile and fissionable isotopes promotes the design of safer and more efficient fabrication, transportation, storage, and stockpiling of nuclear fuel. Unfortunately, there are knowledge gaps in data on key isotopes. In 2011, a multinational meeting hosted by the US Department of Energy Nuclear Criticality Safety Program ranked the priority of certain cross section data needs. In response, Lawrence Livermore National Lab (LLNL) designed the Thermal and Epithermal eXperiment (TEX) series of benchmark experiments. Benchmark experiments are used to validate current cross section data. They validate data by comparing the results of an actual experiment to the predicted results from a computational model. The data a benchmark applies to depends on the isotope and energy range the experiment’s neutron multiplication factor ( k eff ) is most sensitive to. The development and testing of the TEX High 240 Plutonium Benchmark will help validate 240 Pu cross section data. The configuration and materials of this benchmark are designed to be most sensitive to 240 Pu's intermediate energy range (from 0.625 ev to 100 keV ). MCNP® models of the assembly have been developed by LLNL and the results have been written in the final design report. In order for the discrepancies between benchmark models and experiments to be attributed to cross section inaccuracies, the accuracy of the models needs to be verified. The goal of this project is to verify of the results of LLNL's modeling by creating a new set of MCNP models and comparing the results.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2023

Reactivity Coefficient Measurements to Aid in Reducing Compensating Errors in Plutonium Nuclear Data

Compensating errors between several nuclear data observables in a nuclear data library can adversely impact application simulations. The primary goal of the EUCLID project (Experiments Underpinned by Computational Learning for Improvements in Nuclear Data) is to reduce compensating errors between fast (0.1–5 MeV) 239Pu nuclear data for prompt fission neutron spectra (PFNS), average prompt fission neutron multiplicities, and neutron induced fission, capture, elastic, and inelastic cross sections. This work will focus on the design and execution of void reactivity coefficient measurements in the EUCLID experiment, performed on the Planet vertical lift critical assembly machine at the National Criticality Experiments Research Center (NCERC). Two different base configurations were designed and measured, one with high neutron leakage, and one with low neutron leakage. Both were primarily made up of plutonium metal (Zero Power Physics Reactor plates) without interstitial moderators and reflected by half-inch aluminum. Design optimization showed that void reactivity coefficient measurements in three locations per configuration was most impactful to reduce nuclear data uncertainties due to the varying impacts from elastic and inelastic scattering, as well as fission and capture. The locations for measurements were chosen based on preliminary studies which balanced measurement uncertainty and measurement practicality. The measurements were also selected to have sensitivities maximally complementary to previous arrangements. Comparisons across nuclear data libraries highlight the potential impact.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2013

Interim Safe Storage of Plutonium Production Reactors at the US DOE Hanford Site - 13438

Nine plutonium production reactors located on DOE's Hanford Site are being placed into an Interim Safe Storage (ISS) period that extends to 2068. The Environmental Impact Statement (EIS) for ISS [1] was completed in 1993 and proposed a 75-year storage period that began when the EIS was finalized. Remote electronic monitoring of the temperature and water level alarms inside the safe storage enclosure (SSE) with visual inspection inside the SSE every 5 years are the only planned operational activities during this ISS period. At the end of the ISS period, the reactor cores will be removed intact and buried in a landfill on the Hanford Site. The ISS period allows for radioactive decay of isotopes, primarily Co-60 and Cs-137, to reduce the dose exposure during disposal of the reactor cores. Six of the nine reactors have been placed into ISS by having an SSE constructed around the reactor core. (authors)

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2013

Glass-Ceramic Waste Forms for Uranium and Plutonium Residues Wastes - 13164

A program of work has been undertaken to treat plutonium-residues wastes at Sellafield. These have arisen from past fuel development work and are highly variable in both physical and chemical composition. The principal radiological elements present are U and Pu, with small amounts of Th. The waste packages contain Pu in amounts that are too low to be economically recycled as fuel and too high to be disposed of as lower level Pu contaminated material. NNL and ANSTO have developed full-ceramic and glass-ceramic waste forms in which hot-isostatic pressing is used as the consolidation step to safely immobilize the waste into a form suitable for long-term disposition. We discuss development work on the glass-ceramic developed for impure waste streams, in particular the effect of variations in the waste feed chemistry glass-ceramic. The waste chemistry was categorized into actinides, impurity cations, glass formers and anions. Variations of the relative amounts of these on the properties and chemistry of the waste form were investigated and the waste form was found to be largely unaffected by these changes. This work mainly discusses the initial trials with Th and U. Later trials with larger variations and work with Pu-doped samples further confirmed the flexibility of the glass-ceramic. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2017

Innovative Approach to the Management of Waste Arising from the Decommissioning of a Redundant Plutonium Processing Facility - 17081

There are a number of redundant plutonium processing facilities located at Sellafield, in the North West of England within the United Kingdom (UK). Over past decades several decommissioning strategies have been deployed to clean up these redundant facilities. Whilst there have been many successes previously reported, there remain many challenges. Some of these challenges have recently been addressed through a new approach which introduces a number of innovations. The new approach seeks to significantly reduce risks to both decommissioning personnel and the environment by minimising the extent of physical 'hands on' decommissioning activities and by simplifying the waste production process. A large bagless transfer system has been engineered to allow the transfer of whole gloveboxes into crates. This leads to a significant reduction in hazardous 'hands on' work in a highly contaminated environment. The crates are consigned directly to interim storage on the Sellafield site. These hazard minimisation activities have only been made possible through the development and implementation of a new approach to criticality safety assessment. This new approach has recently completed active commissioning with the first waste being safely exported in June 2016. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2017

Self-Absorption Corrections for Plutonium Measurements With the Tomographic Gamma Scanner - 17325

The Tomographic Gamma Scanner (TGS) is a Non-Destructive Assay (NDA) instrument that combines high-resolution gamma spectroscopy with low spatial resolution three-dimensional image reconstruction in order to reduce bias and improve precision for measurements of drummed waste. The TGS technique is especially suited to measure containers with non-uniform source distributions and low-to me-dium-density heterogeneous matrices, compared with traditional NDA methods. Canberra recently built, installed, and commissioned a TGS system, intended primarily for the measurement of plutonium (Pu) bearing waste, at a European nu-clear fuel reprocessing facility. Pu assays using the TGS technique present technical challenges distinct from those typically encountered in traditional LLW applications. Among these is the need to apply corrections for self-absorption effects that occur on scales smaller than the TGS spatial resolution, and can compromise the assay result if not included in the TGS imaging methodology. We present a brief review of the Self Absorption Correction (SAC) technique, and discuss the complications involved with its application to the TGS methodology with examples from our recent experience. This work continues a Canberra history of further developing and refining a technique to solve emerging problems, having commercialized the original methodology by partnering with the research institution that pioneered it. The TGS and the SAC methodologies were originally developed by Los Alamos National Laboratory (LANL) and John Fleissner respectively, and this work illustrates how Canberra has implemented an advancement of these techniques in a new TGS system. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2015

Characterization of plutonium activities in soil - 15429

Plutonium (Pu) contamination in soils at the Nevada National Security Site (NNSS) is characterized using Am-241 activity results from gamma spectroscopy (gamma Am-241) analysis. This is done by inferring the Pu activities using Pu to Am-241 ratios developed from Pu and Am-241 results from alpha spectroscopy isotopic analyses (isotopic Pu and isotopic Am-241). Although the isotopic Pu and Am-241 methods can accurately measure isotopic activities within the sampled material, the amount of soil analyzed is small (typically 1 gram [g] of soil). If there is heterogeneity of particle distribution within the contaminated release site soil, isotopic methods may provide results that are not representative of the contaminated site. The degree of potential heterogeneity needs to be considered before using isotopic analyses to characterize a Pu-contaminated site. Results from various Pu-contaminated sites at the NNSS are presented that demonstrate significant heterogeneity. A larger sample size (∼1,600 g) within a Marinelli container is used for the gamma spectroscopy analysis. This greatly reduces the impact of heterogeneously distributed discrete particles and provides results that are more representative of true contaminant activities at the release site. However, this method cannot provide Pu activities and has the potential to provide less accurate results due to the haphazard location of contaminant particles within the Marinelli container at the time of measurement. The distance of particles from the detector would result in some differential self-absorption of the emissions from radioactive particles. As the magnitude of this problem was not previously understood, a study was conducted to evaluate the variability in Am-241 results due to self-absorption from particle position. Results from this study are shown that demonstrate that this effect provides minimal variability in replicate Am-241 measurements. The method used at the NNSS to characterize Pu activities in soil takes advantage of the accuracy of the alpha spectroscopy isotopic analyses to establish Pu to Am-241 ratios and the more representative gamma spectroscopy results for Am-241 to provide a reliable characterization of Pu activities at contaminant release sites. (authors)

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2015

Thermal treatment of plutonium contaminated materials (PCM) Waste - 15714

Considering the high over all costs of waste disposal and the growing requirements for improved quality of the final waste form, the benefits offered by thermal processing become very significant. Key drivers for the application of thermal treatment processes include the reduced volume, improved passive safety, and superior long term stability, of the vitrified waste form products. The project has demonstrated these benefits are derived from the oxidation of the metallic waste fraction, destruction of organic components, and evaporation of entrained water, combined with simultaneous immobilization of radioactive and chemo-toxic elements with in a glass or slag (i.e. a partially crystallised glass) material. Currently a fundamental lack of scientific knowledge and understanding significantly hinders the uptake of thermal treatment processes for the immobilization and disposal of plutonium contaminated material waste. The project will contribute to accelerating the acquisition of knowledge and experience required to support the NDA in deploying thermal technologies as a national asset for ILW treatment. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2017

Introduction of plutonium systems to the nuclear criticality slide rule

AWE (UK), IRSN (France), LLNL (USA) and ORNL (USA) began a long term collaboration effort in 2015 to update the nuclear criticality Slide Rule for the emergency response to a nuclear criticality accident. This document, published almost 20 years ago, gives order of magnitude estimates of key parameters, such as number of fissions and doses (neutron/gamma), useful for emergency response teams and public authorities. This paper presents, firstly, the motivation and the long term objectives for this update, then it introduces the initial critical configuration, and finally it presents the preliminary results obtained with modern 3D radiation transport codes and nuclear data for new configurations including plutonium systems. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2016

Importance of Plutonium Turnings in Criticality Safety

In criticality safety, turnings are a concern due to the fact that they leave interstitial space in which a moderator can ingress and reduce the critical mass for a fissile material. As turnings are produced when a Plutonium (Pu) items are machined, they are commonly encountered in facilities that process Pu. The intent of this paper is to establish minimum subcritical mass data points for Pu turnings based on the minimum density achievable as measured in a turnings experiment performed at Los Alamos National Laboratory (LANL). Further discussion will cover the implications of these results with concern to criticality safety during normal operations and during a glovebox fire scenario. The results of the study show that a bare homogeneous Pu turnings (at 0.252 kg/L) and water mixture has a spherical critical mass of 3.80 kg, while the fully water reflected spherical critical mass of the same Pu turnings and water mixture has a critical mass of 1.65 kg. When mixed with an idealized hydrocarbon oil rather than water, the spherical critical mass is reduced. In this case, the bare critical mass of the homogeneous Pu turnings and oil mixture is 2.57 kg while the fully water reflected spherical critical mass of the Pu turnings and oil mixture is 1.17 kg. The results of this study show that up to approximately 1000 g of Pu turnings even if mixed with an ideal hydrocarbon and flooded would not be a criticality concern during fire fighting activities. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2016

A Practical Assessment of the Effect of Water Interspersed with Plutonium Metal Hemishells - Summary

Operations with fissile materials can be performed safely by complying with any of the listed single-parameter subcritical limits in ANS-8.1. For metallic units, the single-parameter subcritical limits apply to a single piece having no concave surfaces. They may be extended to an assembly of pieces, provided that there is no neutron moderating material interspersed with the pieces. An MCNP6.1 study was undertaken at the Los Alamos National Laboratory (LANL) to investigate the effect that interspersed water has on plutonium-metal hemishells. At LANL, it is common to have more than one hemishell at any given location, which obviously have concave surfaces. The intent of this paper is to present a high-level summary of the effect of having multiple concave shells, interspersed with water, as well as to discuss the methodology we used to determine the Upper Subcritical Limits (USL's) associated with the results. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗