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At least 577 records · Page 32

HTGR Technology Family Assessment for a Range of Fuel Cycle Missions

This report examines how the HTGR technology family can provide options for the once through, modified open cycle (MOC), or full recycle fuel cycle strategies. The HTGR can serve all the fuel cycle missions that an LWR can; both are thermal reactors. Additional analyses are warranted to determine if HTGR “full recycle” service could provide improved consumption of transuranic (TRU) material than LWRs (as expected), to analyze the unique proliferation resistance issues associated with the “pebble bed” approach, and to further test and analyze methods to separate TRISO-coated fuel particles from graphite and/or to separate used HTGR fuel meat from its TRISO coating. The feasibility of these two separation issues is not in doubt, but further R&D could clarify and reduce the cost and enable options not adequately explored at present. The analyses here and the now-demonstrated higher fuel burnup tests (after the illustrative designs studied here) should enable future MOC and full recycle HTGR concepts to more rapidly consume TRU, thereby offering waste management advantages. Interest in “limited separation” or “minimum fuel treatment” separation approaches motivates study of impurity-tolerant fuel fabrication. Several issues are outside the scope of this report, including the following: thorium fuel cycles, gas-cooled fast reactors, the reliability of TRISO-coated particles (billions in a reactor), and how soon any new reactor or fuel type could be licensed and then deployed and therefore impact fuel cycle performance measures.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Options Study - Phase II

The Options Study has been conducted for the purpose of evaluating the potential of alternative integrated nuclear fuel cycle options to favorably address the issues associated with a continuing or expanding use of nuclear power in the United States. The study produced information that can be used to inform decisions identifying potential directions for research and development on such fuel cycle options. An integrated nuclear fuel cycle option is defined in this study as including all aspects of the entire nuclear fuel cycle, from obtaining natural resources for fuel to the ultimate disposal of used nuclear fuel (UNF) or radioactive wastes. Issues such as nuclear waste management, especially the increasing inventory of used nuclear fuel, the current uncertainty about used fuel disposal, and the risk of nuclear weapons proliferation have contributed to the reluctance to expand the use of nuclear power, even though it is recognized that nuclear power is a safe and reliable method of producing electricity. In this Options Study, current, evolutionary, and revolutionary nuclear energy options were all considered, including the use of uranium and thorium, and both once-through and recycle approaches. Available information has been collected and reviewed in order to evaluate the ability of an option to clearly address the challenges associated with the current implementation and potential expansion of commercial nuclear power in the United States. This Options Study is a comprehensive consideration and review of fuel cycle and technology options, including those for disposal, and is not constrained by any limitations that may be imposed by economics, technical maturity, past policy, or speculated future conditions. This Phase II report is intended to be used in conjunction with the Phase I report, and much information in that report is not repeated here, although some information has been updated to reflect recent developments. The focus in this Options Study was to identify any nuclear fuel cycle technology or option that may result in a significant beneficial impact to the issues as compared to the current U.S. approach of once-through use of nuclear fuel in LWRs or similar reactors followed by direct disposal of UNF. This approach was taken because incremental differences may be difficult to clearly identify and justify due to the large uncertainties that can be associated with the specific causes of the issues. Phase II of this Options Study continued the review of nuclear fuel cycle options that was initiated and documented during Phase I, concentrating on reviewing and summarizing the potential of integrated nuclear fuel cycles. However, based on the reviews of previous studies and available data, it was not always possible to clearly determine sufficiently large differences between the various fuel cycle and technology options for some of the issues or evaluation measures, for example, in cases where only incremental differences with respect to the issues might be achieved regardless of the fuel cycle option or technologies being considered, or where differences were insufficient to clearly rise above the uncertainties.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Natural Tracers and Multi-Scale Assessment of Caprock Sealing Behavior: A Case Study of the Kirtland Formation, San Juan Basin

The assessment of caprocks for geologic CO{sub 2} storage is a multi-scale endeavor. Investigation of a regional caprock - the Kirtland Formation, San Juan Basin, USA - at the pore-network scale indicates high capillary sealing capacity and low permeabilities. Core and wellscale data, however, indicate a potential seal bypass system as evidenced by multiple mineralized fractures and methane gas saturations within the caprock. Our interpretation of {sup 4}He concentrations, measured at the top and bottom of the caprock, suggests low fluid fluxes through the caprock: (1) Of the total {sup 4}He produced in situ (i.e., at the locations of sampling) by uranium and thorium decay since deposition of the Kirtland Formation, a large portion still resides in the pore fluids. (2) Simple advection-only and advection-diffusion models, using the measured {sup 4}He concentrations, indicate low permeability ({approx}10-20 m{sup 2} or lower) for the thickness of the Kirtland Formation. These findings, however, do not guarantee the lack of a large-scale bypass system. The measured data, located near the boundary conditions of the models (i.e., the overlying and underlying aquifers), limit our testing of conceptual models and the sensitivity of model parameterization. Thus, we suggest approaches for future studies to better assess the presence or lack of a seal bypass system at this particular site and for other sites in general.

03 NATURAL GAS↗

The Ames Laboratory Annual Site Environmental Report: Calendar Year 2010

This report summarizes the environmental status of Ames Laboratory for calendar year 2010. It includes descriptions of the Laboratory site, its mission, the status of its compliance with applicable environmental regulations, its planning and activities to maintain compliance, and a comprehensive review of its environmental protection, surveillance and monitoring activities. In 2010, the Laboratory accumulated and disposed of waste under U.S. Environmental Protection Agency (EPA) issued generator numbers. All waste is handled according to all applicable EPA, State, Local regulations and DOE Orders. In 2006 the Laboratory reduced its generator status from a Large Quantity Generator (LQG) to a Small Quantity Generator (SQG). EPA Region VII was notified of this change. The Laboratory's RCRA hazardous waste management program was inspected by EPA Region VII in April 2006. There were no notices of violations. The inspector was impressed with the improvements of the Laboratory's waste management program over the past ten years. The Laboratory was in compliance with all applicable federal, state, local and DOE regulations and orders in 2010. There were no radiological air emissions or exposures to the general public due to Laboratory activities in 2010. See U.S. Department of Energy Air Emissions Annual Report in Appendix B. As indicated in prior SERs, pollution awareness, waste minimization and recycling programs have been in practice since 1990, with improvements implemented most recently in 2010. Included in these efforts were battery and CRT recycling, miscellaneous electronic office equipment, waste white paper and green computer paper-recycling and corrugated cardboard recycling. Ames Laboratory also recycles/reuses salvageable metal, used oil, foamed polystyrene peanuts, batteries, fluorescent lamps and telephone books. Ames Laboratory reported to DOE-Ames Site Office (AMSO), through the Laboratory's Performance Evaluation Measurement Plan, on its Affirmative Procurement Performance Measure. A performance level of 'A-' was achieved in 2010 for Integrated Safety, Health and Environmental Protection. As reported in Site Environmental Reports for prior years, the Laboratory's Environmental Management System (EMS) has been integrated into the Laboratory's Integrated Safety Management System since 2005. The integration of EMS into the way the Laboratory does business allows the Laboratory to systematically review, address and respond to the Laboratory's environmental impacts. The Laboratory's EMS was audited in April 2009 by DOE-CH. There were four 'Sufficiently in Conformity' findings as a result of the audit. All four findings were tracked in the Laboratory's corrective action database for completion. Beryllium was used routinely at Ames Laboratory in the 1940's and 1950's in processes developed for the production of highly pure uranium and thorium in support of the historic Manhattan Project. Laboratory metallurgists also worked on a process to produce pure beryllium metal from beryllium fluoride. In the early 1950's, beryllium oxide powder was used to produce shaped beryllium and crucibles. As a result of that work, beryllium contamination now exists in many interstitial spaces (e.g., utility chases) and ventilation systems in Wilhelm, Spedding and Metals Development buildings. Extensive characterization and remediation efforts have occurred in 2009 and 2010 in order to better understand the extent of the contamination. Analysis of extensive sampling data suggests that a fairly wide dispersion of beryllium occurred (most likely in the 1950's and 60's) in Wilhelm Hall and in certain areas of Spedding Hall and Metals Development. Area air-sampling results and work-area surface characterizations indicate the exposure potential to current workers, building visitors and the public remains extremely low. This information is now used to guide cleaning efforts and to provide worker protection during remodeling and maintenance activities. Results were shared with the DOE's Former Worker Program to support former worker medical testing and compensation programs. A complete discussion of the Laboratory's beryllium characterization and remediation efforts can be found at: http://www.ameslab.gov/operations/esha/beryllium-information.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Preserving Ultra-Pure Uranium-233

Uranium-233 ( 233 U) is a synthetic isotope of uranium formed under reactor conditions during neutron capture by natural thorium ( 232 Th). At high purities, this synthetic isotope serves as a crucial reference material for accurately quantifying and characterizing uranium-bearing materials assays and isotopic distributions for domestic and international nuclear safeguards. Separated, high purity 233 U is stored in vaults at Oak Ridge National Laboratory (ORNL). These materials represent a broad spectrum of 233 U from the standpoint of isotopic purity - the purest being crucial for precise analyses in safeguarding uranium.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Toward an Improved Understanding of Structure and Magnetism in Neptunium and Plutonium Phosphonates and Sulfonates

This grant supported the exploratory synthesis of new actinide materials with all of the actinides from thorium to californium with the exceptions of protactinium and berkelium. We developed detailed structure-property relationships that allowed for the identification of novel materials with selective ion-exchange, selective oxidation, and long-range magnetic ordering. We found novel bonding motifs and identified periodic trends across the actinide series. We identified structural building units that would lead to desired structural features and novel topologies. We also characterized many different spectroscopic trends across the actinide series. The grant support the preparation of approximately 1200 new compounds all of which were structurally characterized.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Lead Slowing Down Spectrometer Status Report

This report documents the progress that has been completed in the first half of FY2012 in the MPACT-funded Lead Slowing Down Spectrometer project. Significant progress has been made on the algorithm development. We have an improve understanding of the experimental responses in LSDS for fuel-related material. The calibration of the ultra-depleted uranium foils was completed, but the results are inconsistent from measurement to measurement. Future work includes developing a conceptual model of an LSDS system to assay plutonium in used fuel, improving agreement between simulations and measurement, design of a thorium fission chamber, and evaluation of additional detector techniques.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Pebble Fuel Handling and Reactivity Control for Salt-Cooled High Temperature Reactors

This report documents the work completed on the X-PREX facility under NEUP Project 11- 3172. This project seeks to demonstrate the viability of pebble fuel handling and reactivity control for fluoride salt-cooled high-temperature reactors (FHRs). The research results also improve the understanding of pebble motion in helium-cooled reactors, as well as the general, fundamental understanding of low-velocity granular flows. Successful use of pebble fuels in with salt coolants would bring major benefits for high-temperature reactor technology. Pebble fuels enable on-line refueling and operation with low excess reactivity, and thus simpler reactivity control and improved fuel utilization. If fixed fuel designs are used, the power density of salt- cooled reactors is limited to 10 MW/m 3 to obtain adequate duration between refueling, but pebble fuels allow power densities in the range of 20 to 30 MW/m 3 . This can be compared to the typical modular helium reactor power density of 5 MW/m3. Pebble fuels also permit radial zoning in annular cores and use of thorium or graphite pebble blankets to reduce neutron fluences to outer radial reflectors and increase total power production. Combined with high power conversion efficiency, compact low-pressure primary and containment systems, and unique safety characteristics including very large thermal margins (>500°C) to fuel damage during transients and accidents, salt-cooled pebble fuel cores offer the potential to meet the major goals of the Advanced Reactor Concepts Development program to provide electricity at lower cost than light water reactors with improved safety and system performance.This report presents the facility description, experimental results, and supporting simulation methods of the new X-Ray Pebble Recirculation Experiment (X-PREX), which is now operational and being used to collect data on the behavior of slow dense granular flows relevant to pebble bed reactor core designs. The X-PREX facility uses novel digital x-ray tomography methods to track both the translational and rotational motion of spherical pebbles, which provides unique experimental results that can be used to validate discrete element method (DEM) simulations of pebble motion. The validation effort supported by the X-PREX facility provides a means to build confidence in analysis of pebble bed configuration and residence time distributions that impact the neutronics, thermal hydraulics, and safety analysis of pebble bed reactor cores. Experimental and DEM simulation results are reported for silo drainage, a classical problem in the granular flow literature, at several hopper angles. These studies include conventional converging and novel diverging geometries that provide additional flexibility in the design of pebble bed reactor cores. Excellent agreement is found between the X-PREX experimental and DEM simulation results. This report also includes results for additional studies relevant to the design and analysis of pebble bed reactor cores including the study of forces on shut down blades inserted directly into a packed bed and pebble flow in a cylindrical hopper that is representative of a small test reactor.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

AIR AND RADON PATHWAY MODELING FOR THE F AREA TANK FARM

An air and radon pathways analysis was conducted for the F-Area Tank Farm (FTF) to estimate the flux of volatile radionuclides and radon at the ground surface due to residual waste remaining in the tanks following closure. This analysis was used as the basis to estimate the dose to the maximally exposed individual (MEI) for the air pathway per Curie (Ci) of each radionuclide remaining in the combined FTF waste tanks. For the air pathway analysis, several gaseous radionuclides were considered. These included carbon-14 (C-14), chlorine-36 (Cl-36), iodine-129 (I-129), selenium-79 (Se-79), antimony-125 (Sb-125), tin-126 (Sn-126), tritium (H-3), and technetium-99 (Tc-99). The dose to the MEI was estimated at the SRS Boundary during the 100 year institutional control period. For the 10,000 year post closure compliance period, the dose to the MEI was estimated at the 100 m compliance point. Additionally, the dose to the MEI was estimated at a seepage outcrop located 1600 m from the facility. For the radon pathway analysis, five parent radionuclides and their progeny were analyzed. These parent radionuclides included uranium-238 (U-238), plutonium-238 (Pu-238), uranium-234 (U-234), thorium-230 (Th-230), and radium-226 (Ra-226). The peak flux of radon-222 due to each parent radionuclide was estimated for the simulation period of 10,100 years.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗

Simulation and Modeling of Optical Properties of U, Th, Pb, and Co Nanoparticles of Interest to Nuclear Security Using Finite Element Analysis

In this work, the optical characteristics of uranium (U), lead (Pb), cobalt (Co), and thorium (Th) nanoparticles are fashioned and simulated employing the finite element analysis (FEA) approach concerning multiple particle sizes. Applying finite element analysis, it was found that the simulated absorption peaks of electronic excitations of nuclear nanoparticles are red-shifted from 365 nm to 555 nm for U; from 355 nm to 550 nm for Pb; from 415 nm to 610 nm for Co; and from 350 nm to 540 nm for Th, comparing expanding particle sizes from 60 nm to 100 nm (except for Co, which varied from 70 nm to 100 nm). The FEA-simulated optical band gap energies and far-field radiation patterns were also obtained for nuclear materials. The simulation approach in this research enables the prediction of optical properties and design of nuclear materials before manufacture for nuclear security applications.

36 MATERIALS SCIENCE↗

RAVE J203843.2–002333: The First Highly R-process-enhanced Star Identified in the RAVE Survey

We report the discovery of RAVE J203843.2−002333, a bright (V = 12.73), very metal-poor ([Fe/H] = −2.91), r-process-enhanced ([Eu/Fe] = +1.64 and [Ba/Eu] = −0.81) star selected from the RAVE survey. This star was identified as a metal-poor candidate based on its medium-resolution (R ∼ 1600) spectrum obtained with the KPNO/Mayall Telescope, and followed up with high-resolution (R ∼ 66,000) spectroscopy with the Magellan/Clay Telescope, allowing for the determination of elemental abundances for 24 neutron-capture elements, including thorium and uranium. RAVE J2038−0023 is only the fourth metal-poor star with a clearly measured U abundance. The derived chemical abundance pattern exhibits good agreement with those of other known highly r-process-enhanced stars, and evidence suggests that it is not an actinide-boost star. Age estimates were calculated using U/X abundance ratios, yielding a mean age of 13.0 ± 1.1 Gyr.

79 ASTRONOMY AND ASTROPHYSICS↗

Nuclear Data Performance Testing Using Sensitive, but Less Frequently Used ICSBEP Benchmarks

The International Criticality Safety Benchmark Evaluation Project (ICSBEP) has published the International Handbook of Evaluated Criticality Safety Benchmark Experiments annually since 1995. The Handbook now spans over 51,000 pages with benchmark specifications for 4,283 critical, near critical, or subcritical configurations; 24 criticality alarm placement/shielding configurations with multiple dose points for each; and 200 configurations that have been categorized as fundamental physics measurements relevant to criticality safety applications. Benchmark data in the ICSBEP Handbook were originally intended for validation of criticality safety methods and data; however, the benchmark specifications are now used extensively for nuclear data testing. There are several, less frequently used benchmarks within the Handbook that are very sensitive to thorium and certain key structural and moderating materials. Calculated results for many of those benchmarks using modern nuclear data libraries suggest there is still room for improvement. These and other highly sensitive, but rarely quoted benchmarks are highlighted and data testing results provided using the Monte Carlo N-Particle Version 5 (MCNP5) code and continuous energy ENDF/B-V, VI.8, and VII.0, JEFF-3.1, and JENDL-3.3 nuclear data libraries.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

On the Cycling of 231 Pa and 230 Th in Benthic Nepheloid Layers

The naturally-occurring radionuclides protactinium-231 ( 231 Pa) and thorium-230 ( 230 Th) are produced at approximately uniform rates in the ocean and thought to be removed from the water column through a reversible exchange with settling particles. Recent measurements along the U.S. GEOTRACES North Atlantic transect (GA03) revealed two features which are at odds with current understanding about 231 Pa and 230 Th cycling in the ocean: (i) a sharp decrease in dissolved 231 Pa ( 231 Pa d ) and 230 Th ( 230 Th d ) activities with depth below 2000-4000 m and (ii) very high particulate 231 Pa ( 231 Pa p ) and 230 Th ( 230 Th p ) activities near the bottom, at a number of stations between the New England continental shelf and Bermuda. Concomitant measurements of light attenuation from beam transmissometry showed that both features occur in benthic nepheloid layers (BNLs), which suggests that these features may stem, at least partly, from the presence of resuspended sediment in the deep water column. Here we explore the behaviour of 231 Pa and 230 Th in BNLs by using (i) radionuclide, optical, and hydrographic data from the western segment of GA03 (west of Bermuda) and (ii) a simplified model of particle and radionuclide cycling that includes a lateral particle source. First, the BNLs observed at GA03 stations are characterized from measurements of the beam attenuation coefficient converted to particle concentrations. At all stations, particle concentrations below the clear water minimum were the highest in the bottom mixed layer, whose thickness ranged from 95 to 320 m, and decreased generally with height above the bottom. The thickness of strong BNLs varied from 482 to 1358 m and the vertical integral of particle concentration in excess to that at the clear water minimum varied from 1 x 10 4 to 2 x 10 6 mg m −2 , among different stations. Second, the particle-radionuclide model is fitted to data from stations GT11-04 (New England continental rise) and GT11-08 (Hatteras abyssal plain), where samples for radionuclide analyses were collected in the BNL. The model can reproduce simultaneously the increase of particle concentration with depth, the low 231 Pa d and 230 Th d in the BNLs, and the high 231 Pa p and 230 Th p near the bottom. According to the model, at heights less than about 300 m above the seafloor, the dissolved phase was set primarily by a balance between adsorption and desorption, with vertical turbulent mixing playing a secondary role, whilst the particulate phase behaved largely as a non-reactive constituent supplied laterally and transported vertically by particle settling and turbulent mixing. Sensitivity tests with the model suggest that lateral particle sources near continental slopes and similar reliefs can produce significant biases both in the 230 Th normalization method and in the interpretation of sediment 231 Pa/ 230 Th records. Our findings yield insights into the influence of sediment resuspension and transport on 231 Pa and 230 Th in the deep ocean and highlight the need for considering these processes in paleoceanographic applications.

Nepheloid layer↗

Exploring new energy alternatives.

What is most likely to satisfy our energy needs in the future - wind farms and photovoltaic arrays, or something yet to be invented? Options for the world's energy future may include surprises, thanks to innovative research under way around the world. The article focuses on the energy sources alternatives in the U.S. It explores innovations for energy sources such as wind farms, solar thermal concentrators, solar cells, and geothermal energy production. It states that the attainment of energy efficiency through conversation or improved technology allows to extract more applied energy. It points out that techniques are being explored to expand the possible fuel materials to includes other types of uranium and thorium. Furthermore, it discusses the capability of nanotechnology in offering a tool which could help create designs that convert energy more efficiently.

14 SOLAR ENERGY↗