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At least 577 records · Page 32

Atomic Power in Space II: A history of space nuclear power and propulsion in the United States

Atomic Power in Space II is a sequel to Atomic Power in Space (published by DOE in 1987). Beginning with a brief overview of the programs and systems developed through the late 1970s, Atomic Power in Space II traces the development and use of space nuclear power systems, including the missions and programs for which they were developed, to the present day. The history is written largely in non technical language so as to be useful to the general reader as well as the seasoned space nuclear professional.

07 ISOTOPE AND RADIATION SOURCES↗

Status of the RRR evaluations for 233,235 U and 239 Pu [Slides]

The presentation discusses the R -Matrix Analysis of 233 U, 235 U, and 239 Pu and how their interplay among PFNS, TNC, RRR, and neutron multiplicities has a significant impact on the benchmarks. The presentation also discusses the 233 U improved agreement on benchmarks, an additional investigation on the thickness of beryllium reflectors, work on URR (up to 40 keV) and/or extension of RRR (600 eV to 2 keV). Also discussed is how the 235 U progresses on understanding reactivity rates related to depletion calculations, improved agreement with measured (capture) data is quite insensitive to resolve the negative slope, and how the 239 Pu negative slope as a function of the temperature is not understood yet (bias over 2σ lower than measured).

07 ISOTOPE AND RADIATION SOURCES↗

Validation of Recent Changes in Actinide Evaluations U-235, U-233, Pu-239 [Slides]

This presentation discusses U-235 updates, including fluctuations in the fission cross section in the URR range that were refined to represent measured data following the Paradela et al. evaluation. There were small changes to the low-energy resonances to improve the fit to measured capture data from RPI (capture reduced by 5% from 0.06-7.8 eV, by 7.7% from 7.8-11 eV) and there was a very small change to the thermal nu-bar within uncertainties. Discrete level data are stored in MF=6 (format requirement, no impact on calculations) and issues leading to negative eigenvalues in cross-covariances in the RR have been sorted out. In conclusion, many improvements were made to evaluated nuclear data of actinides in the resonance region and above, such as minor changes to U-235 including assessment of changes that depend on the finalization of the O-16 evaluation. U-233 improvements show significant progress in performance and some further improvement might be needed at intermediate energies. Pu-239 ORNL/IAEA evaluation is promising; however, more work is needed.

07 ISOTOPE AND RADIATION SOURCES↗

Status of the RRR evaluations for 233,235 U and 239 Pu [Slides]

The presentation discusses the R -Matrix Analysis of 233 U, 235 U, and 239 Pu and how their interplay among PFNS, TNC, RRR, and neutron multiplicities has a significant impact on benchmarks. The presentation also discusses the 233 U improved agreement on benchmarks, an additional investigation on the thickness of beryllium reflectors, work on URR (up to 40 keV) and/or extension of RRR (600 eV to 2 keV). Also discussed is how the 235 U progresses on understanding reactivity rates related to depletion calculations, improved agreement with measured (capture) data is quite insensitive to resolve the negative slope, and how the 239 Pu negative slope as a function of the temperature is not understood yet (bias over 2σ lower than measured).

07 ISOTOPE AND RADIATION SOURCES↗

Technical Evaluation of Accelerated Basin De-Inventory Material Addition to Sludge Batch 11

Savannah River Nuclear Solutions has a need to discard spent nuclear fuel (SNF), currently stored in L Basin, to the Defense Waste Processing Facility (DWPF) for vitrification. The Department of Energy (DOE) has approved the Accelerated Basin De-inventory (ABD) Program for discarding SNF via transfers from H-Canyon to the Savannah River Site (SRS) Liquid Waste (LW) system. The first ABD discards will occur during the preparation of Sludge Batch (SB) 11. An initial impact evaluation of the LW flowsheet was performed by the Savannah River National Laboratory (SRNL) prior to the approval of the ABD Program. This evaluation addressed the LW downstream facilities based on the current H-Canyon flowsheet sequence for the average ABD discard. The flowsheet evaluation only included aluminum-clad SNF, specifically Materials Test Reactor (MTR) fuel and High Flux Isotope Reactor (HFIR) fuel similar to the planned SB11 discard. Following this evaluation, the flowsheet has been slightly altered to address (i) new nuclear criticality safety controls for DWPF that credit a higher amount of gadolinium as a neutron poison for all of the enriched uranium contained in a SB and (ii) potential additions of the H-Canyon neutralized fuel stream prior to the Low Temperature Aluminum Dissolution (LTAD) process in Tank 51. The early introduction of ABD material into the SB assembly process is being investigated to provide flexibility regarding transfer opportunities for H-Canyon to Tank 51 for SB11 and future sludge batches.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

The timing of alkali metasomatism in paleosols

We have measured the concentrations of rubidium and strontium and 87Sr/86Sr values of whole-rock samples from three paleosols of different ages. The oldest of the three weathering horizons, the 2,760 Ma Mt. Roe #1 paleosol in the Fortescue Group of Western Australia, experienced addition of Rb, and probably Sr, at 2,168 +/- 10 Ma. The intermediate paleosol, developed on the Hekpoort Basalt in South Africa, is estimated to have formed at 2,200 Ma, and yields a Rb-Sr isochron age of 1,925 +/- 32 Ma. The youngest of the three paleosols, developed on the Ongeluk basalt in Griqualand West, South Africa ca. 1,900 Ma, yielded a Rb-Sr age of 1,257 +/- 11 Ma. The Rb-Sr systematics of all three paleosols were reset during post-weathering metasomatism related to local or regional thermal disturbances. The Rb-Sr systematics of the paleosols were not subsequently disturbed. The near-complete removal of the alkali and alkaline earth elements from these paleosols during weathering made them particularly susceptible to resetting of their Rb-Sr systematics. Paleosols of this type are therefore sensitive indicators of the timing of thermal disturbances.

NASA Discipline Number 52-20↗

Ambient monitoring to inform the protection of beneficial uses and achieve water quality goals in Sinclair and Dyes Inlets, Puget Sound, WA

Currently discharge limits enforced under the Clean Water Act are focused on meeting water quality standards at the end of the pipe and environmental performance is measured based on meeting the discharge limits; but meeting discharge limits has very little to do with achieving water quality goals for coastal and estuarine ecosystems. Therefore, an effective monitoring and assessment program is needed to assess continuous process improvement, evaluate the ecological conditions, and provide metrics that can inform effective management of coastal and estuarine water quality. As part of an integrated Environmental Investment (ENVVEST) project for Sinclair and Dyes Inlets (ENVVEST 2006; Johnston et al. 2009) a network of monitoring stations was established to characterize environmental conditions, assess potential impacts, and establish environmental quality trends within the Inlets. Water, sediment, and biota monitoring locations were selected that were co-located near suspected sources (industrial, waste water, and stormwater outfalls; marinas, stream mouths, and other sources) or were representative of ambient marine and nearshore conditions. Water column stations and effluents from industrial outfalls were sampled seasonally for trace metals (Cd, Cr, Cu, Hg, Pb, and Zn) using analytical procedures appropriate for seawater (Strivens, Brandenberger and Johnston, 2018), conventional parameters (salinity, dissolved and total organic carbon, total and suspended solids, dissolved O2, pH, turbidity, NO2+NO3, NH4, N, and P), and toxicity. Effluent and water column toxicity tests included mysid shrimp (Americamysis bahia) 96 hr survival, sand dollar (Dendraster excentricus) or purple sea urchin (Strongylocentrotus purpuratus) 96 hr embryo development, QwikLite – dinoflagellate (Pyrocystis lunula) 24 hr bioluminescence response, mussel larvae (Mytilus sp.) 48 hr larvae survival and development, and kelp (Macrocystis pyrifera) 48 hr growth and germination. Additionally, indigenous mussels (Mytilis spp.) were sampled biennially for contaminant residues of metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), lipid content, and stable isotopes of C and N. The mussel data were compared to benchmarks of ecological effects (Johnston et al. 2007, Applied Biomonitoring 2009), samples obtained from a local seafood market harvested from Penn Cove on Whidbey Island (PKPLPC), and data from the national mussel watch status and trends monitoring program (Kimbrough et al. 2008). Results from 2009-2016 showed that dissolved metals nearly always met water quality standards and that water quality in Navy nearshore areas appeared to improve after best management practices (BMPs) for industrial process improvements (US Navy 2012) were completed in Sept. 2013 (Figure 1). In general, toxicity from exposure to whole effluent samples was not observed and ambient water samples were not toxic to test organisms, except that ambient toxicity was only observed during the presence of algal blooms which showed that toxicity was highly correlated with the abundance of the toxic algae Gymnodinium splendens (Rosen et al. 2009). Overall, mussel tissue residues were below benchmarks at most locations (Figure 2), however there were locations that had elevated levels of PAHs, PCBs, Hg, and Cu. Results from the monitoring provide metrics that are being used to assess progress toward meeting environmental quality goals for the watershed.

ENVVEST, PSEMP↗

Advanced Capability of Monte Carlo Transport and Depletion Calculation Program SuperMC for Fusion and Fission Applications

Since the advantages of high simulation accuracy and flexible geometry representation, the Monte Carlo methods have been broadly adopted in nuclear design and analysis of nuclear energy systems. However, great challenges exist for the current Monte Carlo methods including the calculation modeling of complex geometries, slow convergence of complex calculation, etc. Super Monte Carlo Simulation Program for Nuclear and Radiation Process (SuperMC), developed by FDS team, is a general purpose, intelligent and multi-functional program for the design and safety evaluation of nuclear systems, which is designed to perform the comprehensive neutronics calculation. The latest version of SuperMC can accomplish the transport calculation of n,{gamma} for criticality and shielding problems, depletion calculation of isotopes, and has been integrated with the functions of automatic modeling, visualization and cloud computing. The latest progress will be introduced in this paper. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Using an Isotope Enabled Mass Balance to Evaluate Existing Land Surface Models

Abstract Land surface models (LSMs) play a crucial role in elucidating water and carbon cycles by simulating processes such as plant transpiration and evaporation from bare soil, yet calibration often relies on comparing LSM outputs of landscape total evapotranspiration ( ET ) and discharge with measured bulk fluxes. Discrepancies in partitioning into component fluxes predicted by various LSMs have been noted, prompting the need for improved evaluation methods. Stable water isotopes serve as effective tracers of component hydrologic fluxes, but data and model integration challenges have hindered their widespread application. Leveraging National Ecological Observation Network measurements of water isotope ratios at 16 US sites over 3 years combined with LSM‐modeled fluxes, we employed an isotope‐enabled mass balance framework to simulate ET isotope values ( δET ) within three operational LSMs (Mosaic, Noah, and VIC) to evaluate their partitioning. Models simulating δET values consistent with observations were deemed more reflective of water cycling in these ecosystems. Mosaic exhibited the best overall performance (Kling‐Gupta Efficiency of 0.28). For both Mosaic and Noah there were robust correlations between bare soil evaporation fraction and error (negative) as well as transpiration fraction and error (positive). We found the point at which errors are smallest ( x ‐intercept of the multi‐site regression) is at a higher transpiration fraction than is currently specified in the models. Which means that transpiration fraction is underestimated on average. Stable isotope tracers offer an additional tool for model evaluation and identifying areas for improvement, potentially enhancing LSM simulations and our understanding of land‐surface hydrologic processes.

58 GEOSCIENCES↗

New approach to calculate the true-coincidence effect of HpGe detector

The corrections for true-coincidence effects in HpGe detector are important, especially at low source-to-detector distances. This work established an approach to calculate the true-coincidence effects experimentally for HpGe detectors of type Canberra GC3018 and Ortec GEM25-76-XLB-C, which are in operation at neutron activation analysis lab in Malaysian Nuclear Agency (NM). The correction for true-coincidence effects was performed close to detector at distances 2 and 5 cm using {sup 57}Co, {sup 60}Co, {sup 133}Ba and {sup 137}Cs as standard point sources. The correction factors were ranged between 0.93-1.10 at 2 cm and 0.97-1.00 at 5 cm for Canberra HpGe detector; whereas for Ortec HpGe detector ranged between 0.92-1.13 and 0.95-100 at 2 and 5 cm respectively. The change in efficiency calibration curve of the detector at 2 and 5 cm after correction was found to be less than 1%. Moreover, the polynomial parameters functions were simulated through a computer program, MATLAB in order to find an accurate fit to the experimental data points.

07 ISOTOPE AND RADIATION SOURCES↗

SU-E-T-89: Comprehensive Quality Assurance Phantom for the Small Animal Radiation Research Platform

Purpose: Use of Small Animal Radiation Research Platform (SARRP) systems for conducting state-of-the-art image guided radiotherapy (IGRT) research on small animals has become more common over the past years. The purpose of this work is to develop and test the suitability and performance of a comprehensive quality assurance (QA) phantom for the SARRP. Methods: A QA phantom was developed for carrying out daily, monthly and annual QA tasks including imaging, dosimetry and treatment planning system (TPS) performance evaluation of the SARRP. The QA phantom consists of nine (60×60×5 mm3) KV-energy tissue equivalent solid water slabs that can be employed for annual dosimetry QA with film. Three of the top slabs are replaceable with ones incorporating Mosfets or OSLDs arranged in a quincunx pattern, or a slab drilled to accommodate an ion chamber insert. These top slabs are designed to facilitate routine daily and monthly QA tasks such as output constancy, isocenter congruency test, treatment planning system (TPS) QA, etc. One slab is designed with inserts for image QA. A prototype of the phantom was applied to test the performance of the imaging, planning and treatment delivery systems. Results: Output constancy test results showed daily variations within 3%. For isocenter congruency test, the phantom could be used to detect 0.3 mm deviations of the CBCT isocenter from the radiation isocenter. Using the Mosfet in phantom as target, the difference between TPS calculations and measurements was within 5%. Image-quality parameters could also be assessed in terms of geometric accuracy, CT number accuracy, linearity, noise and image uniformity, etc. Conclusion: The developed phantom can be employed as a simple tool for comprehensive performance evaluation of the SARRP. The study provides a reference for development of a comprehensive quality assurance program for the SARRP, with proposed tolerances and frequency of required tests.

07 ISOTOPE AND RADIATION SOURCES↗

Stable isotopic biogeochemistry of carbon and nitrogen in a perennially ice-covered Antarctic lake

Lake Hoare (77 degrees 38' S, 162 degrees 53' E) is an amictic, oligotrophic, 34-m-deep, closed-basin lake in Taylor Valley, Antarctica. Its perennial ice cover minimizes wind-generated currents and reduces light penetration, as well as restricts sediment deposition into the lake and the exchange of atmospheric gases between the water column and the atmosphere. The biological community of Lake Hoare consists solely of microorganisms -- both planktonic populations and benthic microbial mats. Lake Hoare is one of several perennially ice-covered lakes in the McMurdo Dry Valleys that represent the end-member conditions of cold desert and saline lakes. The dry valley lakes provide a unique opportunity to examine lacustrine processes that operate at all latitudes, but under an extreme set of environmental conditions. The dry valley lakes may also offer a valuable record of catchment and global changes in the past and present. Furthermore, these lakes are modern-day equivalents of periglacial lakes that are likely to have been common during periods of glacial maxima at temperate latitudes. We have analyzed the dissolved inorganic carbon (DIC) of Lake Hoare for delta 13C and the organic matter of the sediments and sediment-trap material for delta 13C and delta 15N. The delta 13C of the DIC indicates that 12C is differentially removed in the shallow, oxic portions of the lake via photosynthesis. In the anoxic portions of the lake (27-34 m) a net addition of 12C to the DIC pool occurs via organic matter decomposition. The dissolution of CaCO3 at depth also contributes to the DIC pool. Except near the Canada Glacier where a substantial amount of allochthonous organic matter enters the lake, the organic carbon being deposited on the lake bottom at different sites is isotopically similar, suggesting an autochthonous source for the organic carbon. Preliminary inorganic carbon flux calculations suggest that a high percentage of the organic carbon fixed in the water column is remineralized as it falls through the water column. At nearby Lake Fryxell, the substantial (relative to Lake Hoare) glacial meltstream input overprints Fryxell's shallow-water biological delta 13C signal with delta 13C-depleted DIC. In contrast, Lake Hoare is not significantly affected by surface-water input and mixing, and therefore the delta 13C patterns observed arise primarily from biological dynamics within the lake. Organic matter in Lake Hoare is depleted in 15N, which we suggest is partially the result of the addition of relatively light inorganic nitrogen into the lake system from terrestrial sources.

NASA Program Exobiology↗

Development of a Flexible Design for Irradiation of Miniature Tensile and Charpy Test Specimens in the High Flux Isotope Reactor

Fusion promises a sustainable, clean, safe source of energy that could play a major role in solving the great challenge of meeting the world’s growing power needs. Much of fusion technology in its current state requires further maturation to support a usable fusion reactor platform. Given that the environment in and around a sustained fusion reaction is very harsh, selecting the best materials for such a reactor is crucial. The European fusion materials community spent many years developing one such material, a low-activation martensitic structural steel named Eurofer that is intended primarily for use in the fusion blanket modules. Although this material has reached technological maturity, nuclear performance data are required to qualify Eurofer for these applications. Karlsruhe Institute of Technology (KIT), a member of the EUROfusion consortium, has sponsored an irradiation program to establish irradiation performance data for various forms of the Eurofer alloy family. This document describes the design and development of flexible irradiation capsule designs that can be used to irradiate specimens to temperatures ranging from ~200 – 400°C. This report also details as-built data for the screening and high dose phases of the KIT irradiation campaign of capsules that were submitted for irradiation in the High Flux Isotope Reactor in FY18.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Lunar and Planetary Science XXXVI, Part 1

Contents include the following: Observations with Near Infrared Spectrometer for Hayabusa Mission in the Cruising Phase. First Results of Quadrantid Meteor Spectrum. Compositional Investigation of Binary Near-Earth Asteroid 66063 (1998 RO1): A Potentially Undifferentiated Assemblage. Impact-induced Hydrothermal Activity on Early Mars. HRTEM and EFTEM Studies of Phyllosilicate-Organic Matter Associations in Matrix and Dark Inclusions in the EET92042 CR2 Carbonaceous Chondrite. Volumetric Analysis of Martian Rampart Craters. High Pressure Melting of H-Chondrite: A Match for the Martian Basalt Source Mantle. MERView: A New Computer Program for Easy Display of MER-acquired M ssbauer Data. Distribution, Exchange, and Topographic Control of Subsurface Ice on Mars. Shock-induced Damage Beneath Normal and Oblique Impact Craters. Amphitrites Patera Studied from the Mars Express HRSC Data. Oxygen Isotope Microanalysis of Enveloping Compound Chondrules in CV3 and LL3 Chondrites. Gamma-Ray Irradiation in the Early Solar System and the Conundrum of the Lu-176 Decay Constant. Magnesium Isotope Mapping of Silica-rich Grains Having. Extreme Oxygen Isotope Anomalies Extreme Oxygen Isotopic Anomalies from Irradiation in the Early Solar System, Re-Examining the Role of Chondrules in Producing the Elemental Fractionations in Chondrites. Meteorite Data on the Solar Modulation of Galactic Cosmic Rays and an Inference on the Solar Activity Influence on Climate of the Earth. Volatiles Enrichments and Composition of Jupiter. Thinking Like a Wildcatter Prospecting for Methane in Arabia Terra, Mars. Size Distribution of Genesis Solar Wind Array Collector Fragments. Initial Subdivision of Genesis Early Science Polished Aluminum Collector. Presolar Graphite and Its Noble Gases. Young Pb-Isotopic Ages of Chondrules in CB Carbonaceous Chondrites. Fe Isotopic Composition of Martian Meteorites. Petrology and Geochemistry of Nakhlite MIL 03346: A New Martian Meteorite from Antarctica.

Source record↗

Developing a GUM Compliant Uncertainty Approach for NDA Gamma Analysis Using FRAM

The Fixed-Energy Response-Function Analysis with Multiple Efficiency (FRAM) code was developed at Los Alamos National Laboratory (LANL) to analyze gamma-ray spectra for the isotopic composition of plutonium or uranium. This software provides means to easily process gamma-ray spectra to obtain isotopic information and is used globally for international safeguards applications. In a recent review of the FRAM code for the use in nuclear forensics applications, it was determined that a more complete understanding and definition of the various sources of uncertainty that contribute to the overall uncertainty of the FRAM measurement process is required. As one of the ISO 17025 accredited Bulk Special Nuclear Materials Analysis Program (BSAP) laboratories, LANL is required to perform an accurate and transparent uncertainty calculation on every analysis it performs. This paper describes a new approach to calculate a Guide to the Expression of Uncertainty in Measurement (GUM) compliant FRAM uncertainty to support nuclear forensics applications.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

NASA's Radioisotope Power Systems - Plans

NASA's Radioisotope Power Systems (RPS) Program continues to plan and implement content to enable planetary exploration where such systems could be needed, and to prepare more advanced RPS technology for possible infusion into future power systems. The 2014-2015 period saw significant changes, and strong progress. Achievements of near-term objectives have enabled definition of a clear path forward in which payoffs from research investments and other sustaining efforts can be applied. The future implementation path is expected to yield a higher-performing thermoelectric generator design, a more isotope-fuel efficient system concept design, and a robust RPS infrastructure maintained effectively within both NASA and the Department of Energy. This paper describes recent work with an eye towards the future plans that result from these achievements.

Program↗