Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “NUCLEAR PHYSICS AND RADIATION PHYSICS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Reaction Rate Ratios for Recent Fast Metal Experiments with Large Plutonium Masses

Reaction rate ratios are integral responses that are used within the criticality experiments field because they contain spectral information. While these types of measurements have been utilized for nuclear data validation with historic experiments, few experiments of this type have been utilized for recent experiments, as few exist. This work focuses on measured reaction rate ratios for two nearly bare plutonium critical assemblies with different geometries: one that is cube like (with a Pu mass of 40 kg) and one that is slab like (with a Pu mass of 109 kg). Irradiations were performed with both configurations in which foils were placed near the center of the assembly. Plutonium, highly enriched uranium, depleted uranium, and Au foils were included in the irradiation and counted via high-purity germanium detectors. From these measurements, reaction rate ratios were calculated. Measured and simulated values and uncertainties are presented for the reaction rate ratios. Ratios utilizing the following reactions are given in this work: 197 Au(n, γ), 197 Au(n,2n), 235 U(n,fission), 238 U(n, fission), 238 U(n,2n), 238 U(n,γ), and 239 Pu(n,fission). Uncertainties for the measured reaction rate ratios ranged from 4% to 7%, and the contribution of various parameters to this uncertainty was investigated. The results are compared to historical experiments and should be used for nuclear data validation for future nuclear data library releases. These measurements are part of the EUCLID (Experiments Underpinned by Computational Learning for Improvements in Nuclear Data) project, which utilizes measurement responses in addition to k eff (such as these reaction rate ratios) to help reduce uncertainties in 239 Pu nuclear data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Investigating Similarity Differences for Light-Water-Moderated and Polyethylene-Moderated Systems [Slides]

Validation efforts revealed noticeable differences in c k for light-water and polyethylene moderated systems when compared to experimental systems. Although 1 H-H 2 O and 1 H-poly use some of the same cross section and identical covariance data, the treatment of TSLs in SCALE lead to no contribution to c k between polyethylene application and benchmark experiment. When H 2 O contribution is removed the difference in c k appears to come from 239 Pu chi. Sensitivity profiles and data-induced uncertainty confirm that the polyethylene application more closely resembles the benchmark experiment. Interrogation techniques were used to observe how TSLs and nuclide IDs affect c k . Specific differences between similar systems can be accounted for and examined to help understand differences in similarity (c k ) between systems

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Validating Mixtures of 233 U, 235 U, and 239 Pu for the Sum-of-Fractions Method [Slides]

A joint effort by PNNL and ORNL examined mixtures of 233 U, 235 U, and 239 Pu to determine subcritical mass limits based on similarities to critical benchmark experiments through the Sum-of-Fractions method. Results of the validation efforts by ORNL were used to determine areas of applicability based on EALF and moderator/reflector type. TSUNAMI-1D, TSUNAMI-IP, and VADER sequences used for generating sensitivities, similarity assessments, and statistical testing. Validation efforts provided here using the Sum-of-Fractions method results in k eff values below established calculational margins and provides additional flexibility to limits provided in ANSI/ANS-8.15.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Comparison of the sensitivity of 236 U measurements in environmental samples by MC-ICP-MS and ATONA based high precision U TIMS measurements

The ATONA project is focused upon exploring the improvements in uranium isotope ratio measurements by thermal ionization mass spectrometry (TIMS) provided by a new, capacitor-based, amplifier technology. These “ATONA” Faraday amplifiers (Isotopx Ltd, UK) promise accurate, low-noise measurements of very small signals (< 1 femto-amp) in a traditional Faraday cup, which was only previously possible using an ion counter. This report outlines a series of experiments that were performed to assess the performance of the system in samples that test our rapid analysis procedures, and then compare the results against other mass spectrometry techniques currently available for environmental analyses. The following major goals were achieved: (1) illustrated the importance of 236 U measurements for the screening and analysis of environmental samples; (2) improved sensitivity for 236 U, and then identified 236 U in the 4350B standard at ultra-trace levels (3) Provided comparison of the 236 U sensitivity to multi-collector inductively coupled mass spectrometry techniques (4) Illustrated high TRL for the ATONA based measurement technique. This completes the reporting requirements for task 4 in the project LCP and highlights the utility of the system to make highly sensitive 236 U measurements in programmatically relevant sample matrices and at relevant uranium concentrations.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2024

Report on New and Upgraded National User Facilities in Basic Energy Sciences

On December 1, 2023, the Director of the of the Office of Science (SC) charged all the Department of Energy Office of Science Federal Advisory Committees to respond to look toward the scientific horizon and identify what new or upgraded facilities will best serve the SC community needs in the next ten years (2024-2034). This report by the Basic Energy Sciences Advisory Committee (BESAC) assess facilities for the Basic Energy Sciences (BES) program.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2025

A Robust Assessment of High-Precision Plutonium Isotopic Analysis by Thermal Ionization Mass Spectrometry [Slides]

TIMS at SRNL • SRNL consolidated analytical laboratories and services into one area – loss of TIMS capability during relocation. • SRNL installed a new Thermo Scientific TRITON Plus TIMS in our Category II Nuclear Facility to re-establish the lab’s TIMS capabilities in Feb. 2024. • Allows for handling, preparation, purification, and analysis of high-level radiological materials within a single location • Pu and U isotopic composition and assay measurement qualification have been priority since installation. • Once the instrument has been qualified, this capability will support internal and external customers.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2024

Radiation Dose Modeling for Niowave’s Accelerator Driven Uranium Target Assembly 3

Molybdenum-99 is a high-value radionuclide commonly used for medical purposes within the United States. The National Nuclear Security Administration (NNSA) seeks to reliably produce the radioisotope 99 Mo without the use of highly enriched uranium. NNSA’s Office of Material Management and Minimization (M3) provides funding and government laboratory expertise to private companies to expedite the production process domestically and currently funds designs that use low-enriched uranium or other 99 Mo production pathways. Several production designs are being explored across the industry, including uranium fission and photonuclear conversion of 100 Mo targets. Niowave Inc. seeks to produce 99 Mo via a high-energy electron accelerator that strikes a lead-bismuth eutectic target that ultimately produces a consistent neutron flux. The neutron flux then interacts in a subcritical reactor core configuration to produce fission in low-enriched or natural uranium targets. These fissionable targets are then processed to extract 99 Mo. The purpose of this work is to estimate the neutron and photon dose response across Niowave’s proposed facility for worker safety during operation. Owing to the size of the proposed Niowave facility and necessary shielding, unbiased Monte Carlo radiation transport is impractical, and variance reduction methods are required. This work focuses on the weight window variance reduction method to produce high confidence dose response results within a Monte Carlo radiation transport code. Specifically, an adjoint-informed weight window methodology was created to improve the dose response estimates for accelerator-driven subcritical reactor designs. This adjoint-informed methodology was implemented for Niowave’s proposed design and improved dose results at far-field locations across the facility. Acceptable dose rate contours for the proposed facility were generated across the facility and are presented in this work.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2025

NCSP Outlook and Interest for Collaboration on HST Experiments [Slides]

The majority of the NCSP budget goes to Integral Experiments. The goal is to produce needed integral data for criticality safety needs in DOE, largely resulting in ICSBEP benchmarks. NCSP has a well defined process for allocating funding through proposals and expert review. NCSP is a fairly small program and funding is prioritized for experiments that would address DOE criticality safety needs. The majority of the currently identified DOE criticality safety needs are HEU and Pu systems. NCSP has a formal mechanism to ensure quality and benefit through the phase gates and approvals within the CED process.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Pathways to Improved Representation in Advanced NucleAr science (PIRANA)

This document presents the final technical report for Pathways to Improved Representation in Advanced NucleAr Science (PIRANA), supported by the U.S. Department of Energy Office of Science (Office of Nuclear Physics) under Award No. DE-SC0024677 through the Reaching a New Energy Sciences Workforce (RENEW) initiative. The project launched in Fall 2023 at Skyline College in San Bruno, California, a federally recognized Minority Serving Institution (MSI) and the only community college participating in the nEXO collaboration. Through this partnership, Skyline College established an accessible and rigorous research environment for its students. Over the course of the project, 10 student trainees made meaningful contributions to nEXO detector R&D and to activities aimed at expanding student engagement in advanced nuclear science. An additional 24 students completed the Summer Introduction to Research and Experimentation in Nuclear physics (SIREN), a three-week program developed from the training materials created for the nEXO trainees. All participating students engaged in opportunities to present their work locally and at national conferences, take part in public outreach, and contribute to a range of academic activities across campus. Collectively, these efforts extended the impact of the project throughout the wider Skyline College community.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Stockpile Stewardship and Nuclear Testing: A Technical Assessment

Since 1992, the United States has retained confidence in its nuclear weapon stockpile without performing any tests that produce nuclear yield. Instead, it has invested in a stockpile stewardship program (SSP) based on the same approach that was validated through fifty years of experience during the nuclear testing era. As the test moratorium continues and new information becomes available, it is both necessary and appropriate to periodically revisit the question of whether or not nuclear testing should resume. In a recent article by Dr. Mark Schneider, he asserts that the United States should return to nuclear testing to address the issues that negatively affect our country’s nuclear deterrent. A serious, technically informed evaluation of the most significant of the issues Dr. Schneider has raised is provided in this paper. The conclusion of this evaluation is that the strategy of a well-funded SSP coupled with rigorous assessments to identify if there is a specific need for a nuclear test is sound and cost-effective approach. Any decision otherwise needs to take into careful consideration all the classified SSP successes and data pertaining to the particular issues in question.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2021

Enhancement of sub-thermal neutron flux through cold polyethylene

Total thermal neutron cross section measurements serve as the primary means of validation for thermal neutron scattering kernels, an important quantity for neutron transport calculations. In an effort to improve the quality of thermal neutron scattering kernels, researchers at Rensselaer Polytechnic Institute (RPI) designed and constructed a polyethylene based cold moderation system to enhance neutron flux below 10 meV when coupled with the Enhanced Thermal Target (ETT) at the RPI Gaerttner LINAC. The final design yielded an increase in sub-thermal neutron flux (below 10 meV) by a factor of 4.5 for a moderator temperature of 37.5 K relative to the ETT alone. A further increase to a factor of 6 is expected after a minor geometry modification and decrease in polyethylene temperature to 25 K. This novel capability will be used to conduct total thermal neutron cross section measurements from 0.0005–10 eV for different materials including moderator materials.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗