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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.

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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Experience with Inner Reflector Plug exchange in SNS

The Inner Reflector Plug (IRP) is a central component of the Spallation Neutron Source target monolith, which houses the mercury target and four liter-sized neutron moderator units. It is exposed to high-level radiation fields during routine operation and builds up significant activity. The IRP needs to be replaced due to moderator neutron poison and decoupler burn-out, which is used for shaping neutron pulses. The first IRP exchange took place in March 2018. The old IRP was extracted from the target monolith, providing space for the new one. It was split into three segments, each of which was handled separately. The lowest section of the IRP is the largest segment in size and in activity and is temporarily stored on-site for cool down before conduction post irradiation examination. In support of planning the replacement activities, a wide range of activation and transport analyses were performed. This included calculating isotope inventories and the radiation fields for each segment as it is extracted in storage casks, and the radiation field from the empty IRP pit in the target monolith. While the replacement was taking place, measurements were performed and later on compared to the calculations. During these studies, it was discovered that a significant contributor to the radiation field from the lower IRP segment is from photo-neutrons. Photo-nuclear physics was added to the analyses and calculated results compared well with measured dose rates.

Popova, Irina I.↗
DOE OSTI2024

Fixed Source Sensitivity Calculations for Inertial Confinement Fusion Applications

A numerical code library was developed for the radiation transport code MCNP6.3 to calculate generalized response sensitivity coefficients for fixed source neutron transport problems with applications to inertial confinement fusion (ICF) experiments. The new MCNP6.3 dependency is used to generate a novel time convolution response that represents a neutron time-of-flight (nToF) signal. The traditional suite of macroscopic cross-section sensitivities and constrained fixed source probability distribution sensitivities are available for both the standard and the new response tallies in this library. However, novel sensitivity coefficients for the constrained hyperparameters of analytic fixed source probability distributions are emphasized in this work for their connection to ICF neutron transport models. Particularly, advanced Monte Carlo methods are developed for calculating the sensitivity of a nToF signal to perturbations in an ICF plasma’s ion temperature and burn history as well as perturbations in the target liner mass density and the shape parameters of the nToF detector’s impulse response function. Together, these capabilities form an advanced suite of computational tools that can be used to analyze and extract information from any ICF experimental platform.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Evaluation of Second Target Station Target Streaming for the Preliminary Design of the Target Assembly

This report documents the analysis of dose rate fields from a combination of two sources stemming from the target system of the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source (SNS) Second Target Station (STS). This analysis supports the target drive components’ lifetime estimates and conventional facilities’ preliminary design. The two sources detailed in this report are the radiation generated by the proton beam incident on the target and the activated cooling water in the pipes at the top of the target assembly. The analysis considers the STS target system in operational configuration, with all shielding in place. The dose rate fields are calculated in the target drive room and through the target drive room ceiling. This report calculates the thickness necessary for the target drive room’s high-density concrete ceiling to meet the 0.25 mrem/hr dose limit requirement in the high bay directly above the target drive room. In addition to sizing the target drive room ceiling, this report includes details of the dose field surrounding the target drive assembly to estimate the deposited dose in the target drive assembly components resulting from both streaming and decay of activated water. Prompt neutrons and gammas generated by the proton beam incident on the target primarily stream along the gaps between the target assembly and core vessel shielding. Because the models and analysis detailed in this report are based on the STS preliminary design, future analysis is needed to support the STS final design.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Neutron Imaging Using Organic Glass Scintillators

In this work, we develop of a compact neutron imaging system based on organic glass scintillator and silicon photomultiplier arrays. The recently developed organic glass scintillator has excellent neutron and gamma-ray detection efficiency and exhibits pulse shape discrimination capability that is nearly as good as current state-of-the-art materials such as trans-stilbene. We have cast and characterized 6 mm by 6 mm by 50 mm bars of organic glass in our laboratory. When coupled to a silicon photomultiplier array, these bars demonstrated better energy and timing resolution than the stilbene organic scintillator. Here, this performance makes organic glass an ideal material for a compact neutron imaging system, which must resolve neutron scatter events on a sub-nanosecond time scale. We have demonstrated neutron imaging with bars of organic glass scintillator coupled to arrays of silicon photomultipliers. Additional bars of organic glass will be implemented into the system to improve the efficiency and imaging performance. The resulting system will be demonstrated using 252 Cf and PuBe neutron sources in our laboratory. In addition, we will compare imaging performance to other compact neutron imaging systems that exist in literature.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Radiation Hardening – Test Capabilities (LANSCE) [Slides]

The Los Alamos Neutron Science Center (LANSCE) has exceptional facilities for research and testing of radiation effects in electronics. We have the best terrestrial neutron source for sea-level and airplane-altitude environments. We have a thermal neutron test capability at the Lujan Center and a proton beam test capability at the “Blue Room”. LANL has the programmatic mission to develop this radiation-effects program, namely space and satellite environments, high-performance computing (silent data corruption), and weapons delivery systems. We have a strong connection to industry which continues to grow.

42 ENGINEERING↗
DOE OSTI2025

Detector pixel calibration of time-of-flight neutron diffractometers accelerated by machine learning

Modern time-of-flight neutron diffractometers at spallation neutron source are equipped with two dimensional detectors with fine pixelations. The flight path of neutrons from the moderator to the sample and to the detector needs to be precisely calibrated at detector pixel level using standard powders so the diffraction data from all the detector pixels can be correctly time-focused to produce high resolution diffraction peaks. The number of pixels can reach to millions which makes a single-pixel calibration process time-consuming, or even impossible, with conventional fitting routine. Here we presented a machine learning aided calibration process via a “training and predict” process by training machine learning models with the relations between the individual pixel time-of-flight diffraction pattern and fitted diffraction constant. The training models take a portion of the available pixels to predict the diffraction constants precisely and rapidly for massive pixel diffraction patterns.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Implementation and verification of PyNE R2S with DAG-OpenMC

The mesh-based Rigorous-Two-Step (R2S) method has been widely used in the accurate estimation of the shutdown dose rate (SDR) of fusion systems. Several mesh-based R2S code has been implemented based on Monte Carlo particle transport code MCNP5 or DAG-MCNP5 and inventory calculation code such as FISPACT-II, ALARA or ACAB. Recently, the OpenMC, a community-developed Monte Carlo particle transport code, implemented the photon particle transport capability, which enables OpenMC to be used in R2S. In this paper, PyNE R2S is extended with the support of DAG-OpenMC, i.e., OpenMC with DAGMC. Modifications that allow PyNE to read the flux result in the state point file of OpenMC has been implemented to PyNE R2S workflow. A custom source routine of OpenMC that reads the photon source file from PyNE R2S and sampling photon particle in OpenMC photon transport has been implemented in OpenMC. With these modifications, PyNE R2S is now capable of performing R2S calculations with both DAG-MCNP5 and DAG-OpenMC. The ITER FNG dose rate benchmark problem has been used to validate the code. The FNG neutron source has been modified for neutron transport with DAG-OpenMC. The shutdown dose rate of 19 cooling times has been calculated and compared with the experimental data and the computational results of other R2S codes. The results of PyNE R2S with DAG-OpenMC show satisfactory agreement with the experimental data and other computational results. Therefore, we consider PyNE R2S with DAG-OpenMC is a reliable code to calculate the SDR of fusion systems.

fusion↗
DOE OSTI2020

Coherent elastic neutrino-nucleus scattering at the European Spallation Source

The European Spallation Source (ESS), presently well on its way to completion, will soon provide the most intense neutron beams for multi-disciplinary science. Fortuitously, it will also generate the largest pulsed neutrino flux suitable for the detection of Coherent Elastic Neutrino-Nucleus Scattering (CEνNS), a process recently measured for the first time at ORNL’s Spallation Neutron Source. We describe innovative detector technologies maximally able to profit from the order-of-magnitude increase in neutrino flux provided by the ESS, along with their sensitivity to a rich particle physics phenomenology accessible through high-statistics, precision CEνNS measurements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Systematic evaluation of fast neutron sensing with Cesium Hafnium Chloride

Cesium Hafnium Chloride (CHC) is a promising new scintillator for dual mode sensing of both neutrons and gamma-rays. The high chlorine content allows for both 35 Cl(n,p) 35 S and 35 Cl(n,α) 32 P reaction channels leading to reliable detection of fast neutrons. By utilizing pulse shape discrimination (PSD), these neutron interactions may be reliably separated from gamma-ray signals with a high figure-of-merit (FOM) after optimization of the PSD algorithm. Here, in this study, the PSD algorithm settings for CHC were systematically investigated using a bare 252 Cf and a lead shielded plutonium beryllium neutron source. It was found that the PSD algorithm settings affects both the FOM and the neutron detection efficiency, but a FOM as high as 4.5 for alpha particles was observed in one data processing scenario. Further, an intrinsic 5 parts per million alpha emitting contamination was observed in the sample, which we attribute to natural uranium.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Methods for neutron diffraction studies on hydride superconductors and other metal hydrides

High-pressure neutron diffraction is an extremely useful technique in the quest for making and understanding novel hydride superconductors. Neutron diffraction can be used to directly determine elemental stoichiometries and atomic positions of many light elements such as hydrogen or deuterium, even in the presence of heavy elements such as rare-earth metals. In this work, we report on the current status and ongoing developments on high-pressure neutron diffraction for hydride superconductors and other metal hydrides with a special focus on current advancements at the Spallation Neutrons and Pressure (SNAP) beamline of the Spallation Neutron Source at Oak Ridge National Laboratory. For broader context, an overview of high-pressure neutron diffractometers and pressure cells is included together with insight into critical sample considerations. There, attention is given to the requirements for powdered hydride samples and the need for deuterium rather than hydrogen. Additionally, the advantages of angular access and data representation as possible at SNAP are described. We demonstrate the current capability for high-pressure neutron diffraction on two different samples created via hydrogen gas loading, specifically pure deuterium and nickel-deuteride. The deuterium example highlights the usefulness of adding sample materials that facilitate the formation of a good powder while the nickel-deuteride example demonstrates that atomic deuterium positions and stoichiometry can be directly determined. Both examples highlight the importance of large scattering apertures. These enable investigation of the data resolved by scattering angle that is needed to identify parasitic peaks and background features. Finally, future directions beyond current high-pressure neutron powder diffraction are also discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

ASIC Scoping Study Final Report

This report documents the results and findings of a one-year scoping study investigating multichannel readout application specific integrated circuits (ASICs) for interfacing to, and processing data from, silicon photomultiplier (SiPM) arrays. We document ASIC desired and required specifications for four applications supporting national security mission areas: neutron radiography, associated particle imaging, and two versions of kinematic neutron imaging cameras. While each application has a few unique requirements that stress capability, there is generally good agreement among most. Two recently developed ASIC devices were evaluated in a system-like configuration by interfacing these to scintillator crystals exposed to gamma and neutron sources. The 64-channel ORNL device delivered functional capability while meeting most mission requirements for neutron radiography. The Nalu Scientific device, a 32-channel full waveform digitizer, did not demonstrate reliable neutron / gamma separation but it is unclear if this was an ASIC issue or problems with test setup or firmware. A literature survey of other commercial and academic ASICs was undertaken to with the conclusion that existing devices do not meet all requirements.

42 ENGINEERING↗
DOE OSTI2025

GEANT3 simulations for a beryllium Moderator for the Neutron Target Demonstrator (NTD)

Measurements of neutron-induced reactions, particularly on short-lived nuclei, are crucial for nuclear astrophysics and applications. The Neutron Target Demonstrator (NTD) aims to address this by using a strong mod erated spallation neutron source coupled with an ion storage ring. This work investigates the potential of improving the neutron moderator, a key component of the NTD. Using GEANT3 simulations, we compare the performance of the existing 80 cm carbon moderator with a new moder ator design, which utilizes beryllium pieces available at LANL to form a core surrounded by carbon. Simulations were performed 800 MeV pro tons incident on a tungsten target. The results demonstrate that the beryllium-core moderator increases the density of moderated neutrons within the central beam pipe by roughly a factor 4 compared to the pure carbon moderator. This enhancement makes the beryllium-core design a very promising option for future experiments focused on neutron-induced measurements in inverse kinematics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Experiment Design and Preparation for a Shielding Benchmark Utilizing Godiva-IV

An experiment is currently being designed to provide a high-quality shielding benchmark for Criticality Accident Alarm System (CAAS) modeling. Previous benchmarks have suffered from uncertainty primarily due to two factors. The first factor is radiation that is not directly coming from the source, also known as room return. Room return is notoriously difficult to account for in experimental data and to model in benchmarks. The second factor is uncertainty associated with the source term itself. In order to reduce these two sources of uncertainty, this experiment will utilize a room return shield [1] that will reduce the effect of room return and previous work performed to ensure the reproducibility of the source term. The experiment will use the Godiva IV [2] assembly located at the National Criticality Experiments Research Center (NCERC) to provide a neutron source representative of a criticality accident. Previous experiments [3]-[4] have shown that Godiva IV is capable of producing both bursts and steady-state emissions of equal magnitude which will allow for reduced uncertainty in the source term. The room return shield will house and isolate the shielding samples, neutron activation foils, and other detectors. Data collected will provide a comparison of the neutron and gamma dose for shielded and unshielded configurations. This data will be used to validate shielding data used for modeling criticality accident alarm systems. Shielding samples included in this benchmark are C, Fe, NaCl, Pb, high density polyethylene, and SiO 2 . This paper details the design of the room return shield, the experimental plan, challenges, and mitigation strategies.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2026

Record of Decision: H - LEBT Design Modifications

The LAMP Conceptual Design (LCD) is described in the LAMP Conceptual Design Report. The proposed new configuration of the LAMP H - LEBT encompasses multiple changes to the LCD. The new configuration makes use of a single H - source to supply beam to all LANSCE user stations except IPF; this eliminates one of the H - sources in the LCD, and the associated pulsed merger magnet the use of two such sources required. The source current from the sole H - source is gated on a macropulse-by-macropulse basis using techniques demonstrated at SNS (Spallation Neutron Source), specifically, changes to the RF plasma drive power. A pulsed electrode system is used to match the beam into the LEBT transport line, variable on a macropulse-by-macropulse basis to match the source beam current.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Fast Neutron Scintillator Screens for Neutron Imaging Using a Layered Polymer-Phosphor Architecture

Fast neutrons enable a nondestructive examination of dense, large, and highly attenuating samples due to their lower interaction probability compared to thermal neutrons. However, this also creates a challenge in fast neutron imaging, as the thicker sensors necessary to detect fast neutrons degrade an image’s spatial resolution due to scattering within the sensor and the indeterminate depth of interaction in the sensor. This work explores the advantages of a fast neutron imaging screen with a layered polymer-phosphor screen approach as opposed to a mixed polymer-phosphor screen typically used in fast neutron imaging. Proton recoil is the primary conversion mechanism for fast neutron imaging. Simulations showed that the recoil proton range of typical fast neutrons is approximately 200 µm, however, tests at Idaho National Laboratory revealed that the light output of these screens increased at much greater polymer thicknesses. The NECTAR fast neutron beamline at FRM II was used to test the imaging performance of layered fast neutron imaging screens. Distinguishing between the fast-neutron and γ-ray signals is a major challenge in fast neutron imaging because all fast neutron sources also produce γ-rays. A relative comparison between a control plate and the fast neutron screen was made to distinguish between a γ-ray and fast neutron signals. MCNP modeling quantified the γ-ray and fast neutron contributions to the images measured at NECTAR, which were approximately a 75% γ-ray image.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

BM3DORNL

BM3DORNL is a high-performance, open-source library for removing streak and ring artifacts from computed-tomography (CT) data, developed for neutron imaging at Oak Ridge National Laboratory's Spallation Neutron Source (VENUS beamline) and applicable to X-ray CT as well. Ring artifacts — concentric rings in reconstructed slices caused by detector pixel-to-pixel response non-uniformities — appear as vertical streaks in the sinogram and degrade both image quality and quantitative analysis. BM3DORNL operates in the sinogram domain using an adaptation of the BM3D (block-matching and 3D collaborative filtering) algorithm (Dabov et al., 2007). It provides a dedicated streak-removal mode, a true multi-scale BM3D variant (after Mäkinen et al., 2021) that suppresses wide streaks single-scale methods miss, and an alternative Fourier–SVD method (~2.6× faster) combining FFT-based energy detection with rank-1 SVD. The computationally intensive core is implemented in Rust with parallel (Rayon) block matching, integral-image pre-screening, and optimized transforms, and is exposed through a simple Python API (with an optional GUI) so it integrates directly into existing tomography reconstruction pipelines. It processes both 2D sinograms and 3D sinogram stacks, is pip-installable for Linux and macOS, and is documented at https://bm3dornl.readthedocs.io.

Zhang, Chen [Oak Ridge National Laboratory (ORNL),↗
DOE OSTI2022

Fundamental Neutron Physics at Spallation Sources

Low-energy neutrons have been a useful probe in fundamental physics studies for more than 70 years. With advances in accelerator technology, many new sources are spallation based. These new, high-flux facilities are becoming the sites for many next-generation fundamental neutron physics experiments. In this review, we present an overview of the sources and the current and upcoming fundamental neutron physics programs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

An overview of polarized neutron instruments and techniques in Asia Pacific

Polarized neutron scattering is an indispensable tool for exploring a vast range of scientific phenomena. With its dynamic scientific community and significant governmental support as well as the rapid economic growth, the Asia–Pacific region has become a key player in the worldwide neutron scattering arena. From traditional research reactors to cutting-edge spallation neutron sources, this region is home to a myriad of advanced instruments offering a wide range of polarized neutron capabilities. This review aims to provide a comprehensive overview of the development and current status of polarized neutron instruments and techniques in the Asia–Pacific region, emphasizing the important role of the Asia–Pacific region in shaping the landscape of global polarized neutron scattering development.

47 OTHER INSTRUMENTATION↗