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DOE OSTI2018

Calcined Waste Storage at the Idaho Nuclear Technology and Engineering Center

This comprehensive report provides definitive information regarding the volume, mass, and composition (chemical and radioactivity) of the calcined waste stored at the Idaho Nuclear Technology and Engineering Center on the Idaho National Laboratory Site. The calcine composition data are required for current regulatory compliance and safe operation of the INTEC’s six Calcined Solids Storage Facilities (CSSFs), as well as future retrieval, treatment, and shipping the calcine to an off-Site facility (such as a geologic repository). This report also contains a description of the calcine storage bins that compose each of the CSSFs, emphasizing the features that may be of concern to future calcine retrieval. The CSSFs were designed by different architectural engineering firms and built at different times. Each CSSF has a unique design, reflecting varying design criteria and lessons learned from historical CSSF operation. The varying CSSF designs will affect future calcine retrieval processes and equipment. This revision (5) of the report presents refinements of the databases used to calculate the volume, mass, chemical content, and radioactivity of calcined waste produced and stored within the CSSFs. This revision corrects minor errors and inconsistencies noted in an extensive validation and verification effort of the prior version of the Microsoft Excel workbooks upon which the calcine composition described in this report is based. Historical calcine samples are insufficient in number and scope of analysis to fully characterize the entire inventory of calcine in the CSSFs. Sample data exist for all of the liquid wastes that were calcined. This report provides calcine composition data based on liquid waste sample analyses, the volume of liquid waste calcined, calciner operating data, and CSSF operating data using several large Microsoft Excel (Microsoft 2010) databases and spreadsheets. The Excel spreadsheets are collectively called the Historical Processing Model (HPM). The calcine composition determined by this method compares favorably with historical calcine sample data.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2012

Markov Model of Accident Progression at Fukushima Daiichi

On March 11, 2011, a magnitude 9.0 earthquake followed by a tsunami caused loss of offsite power and disabled the emergency diesel generators, leading to a prolonged station blackout at the Fukushima Daiichi site. After successful reactor trip for all operating reactors, the inability to remove decay heat over an extended period led to boil-off of the water inventory and fuel uncovery in Units 1-3. A significant amount of metal-water reaction occurred, as evidenced by the quantities of hydrogen generated that led to hydrogen explosions in the auxiliary buildings of the Units 1 & 3, and in the de-fuelled Unit 4. Although it was assumed that extensive fuel damage, including fuel melting, slumping, and relocation was likely to have occurred in the core of the affected reactors, the status of the fuel, vessel, and drywell was uncertain. To understand the possible evolution of the accident conditions at Fukushima Daiichi, a Markov model of the likely state of one of the reactors was constructed and executed under different assumptions regarding system performance and reliability. The Markov approach was selected for several reasons: It is a probabilistic model that provides flexibility in scenario construction and incorporates time dependence of different model states. It also readily allows for sensitivity and uncertainty analyses of different failure and repair rates of cooling systems. While the analysis was motivated by a need to gain insight on the course of events for the damaged units at Fukushima Daiichi, the work reported here provides a more general analytical basis for studying and evaluating severe accident evolution over extended periods of time. This work was performed at the request of the U.S. Department of Energy to explore 'what-if' scenarios in the immediate aftermath of the accidents.

08 HYDROGEN↗

DOE OSTI2016

Low-Carbon City Policy Databook: 72 Policy Recommendations for Chinese Cities from the Benchmarking and Energy Savings Tool for Low Carbon Cities

This report is designed to help city authorities evaluate and prioritize more than 70 different policy strategies that can reduce their city’s energy use and carbon-based greenhouse gas emissions of carbon dioxide (CO 2 ) and methane (CH 4 ). Local government officials, researchers, and planners can utilize the report to identify policies most relevant to local circumstances and to develop a low carbon city action plan that can be implemented in phases, over a multi-year timeframe. The policies cover nine city sectors: industry, public and commercial buildings, residential buildings, transportation, power and heat, street lighting, water & wastewater, solid waste, and urban green space. See Table 1 for a listing of the policies. Recognizing the prominence of urban industry in the energy and carbon inventories of Chinese cities, this report includes low carbon city policies for the industrial sector. The policies gathered here have proven effective in multiple locations around the world and have the potential to achieve future energy and carbon savings in Chinese cities.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

NASA NTRS2012

Amino Acids in Asteroids and Comets: Implications for the Origin of Life on Earth and Possibly Elsewhere

Meteorites provide a record of the chemical processes that occurred in the early solar system before life began on Earth. The delivery of organic matter by asteroids, comets, and their fragments to the Earth and other planetary bodies in our solar system could have been an important source of the prebiotic organic inventory needed for the emergence of life. Amino acids are essential components of proteins and enzymes in life on Earth and these prebiotic organic compounds have been detected in a wide variety of carbon-rich meteorites, the majority of which have been determined to be extraterrestrial in origin. In addition, many amino acids are structurally chiral (they possess handedness) and with a few very rare exceptions, only left handed (L) amino acids are found in biology, while all known abiotic syntheses of amino acids result in equal mixtures of left and right handed (L~D) amino acids. The discovery of a significant left handed amino acid imbalance of up to 20% in several different carbonaceous meteorites, could point toward a possible prebiotic contribution to the origin of biological homochirality by the exogenous delivery of extraterrestrial organic material to the early Earth. In this talk, I will focus on recent state-of-the-art measurements of the distribution, chirality, and isotopic composition of amino acids in meteorites and cometary samples carried out at the Goddard Astrobiology Analytical Laboratory. Results from the analyses of a variety of Antarctic meteorites, samples from comet Wild 2 returned by the STARDUST mission, and meteorite fragments of asteroid 2008 TC3 called Almahata Sitta recovered from northern Sudan will be discussed

Glavin, Daniel↗

DOE OSTI2018

Integrated Component-Specific Measurements to Develop Emission Factors for Compressors and Gas Gathering Lines

The Department of Energy (DOE) National Energy Technology Laboratory (NETL) and other critical stakeholders (e.g., U.S. Environmental Protection Agency (USEPA), state regulators, and industry) seek to more accurately characterize and quantify methane emissions from compressors and gathering lines within the Gathering and Boosting (G&B) segment of the natural gas system network. These efforts will reduce uncertainties in emissions estimates in USEPA’s current Green House Gas Inventory (GHGI) under their Greenhouse Gas Reporting Program (GHGRP). For this study, four G&B stations in the Gulf Coast Area were visited four times over the course of one year. Components were classified according to equipment and component type and emissions from select components were measured using multiple measurement technologies. The following major equipment types were considered: i) compressors, ii) separators, iii) dehydrators, iv) coalescers, v) slug catchers, vi) yard piping, vii) tanks, and viii) gathering lines. Individual components on each equipment type were further divided into the following main categories: i) connectors, ii) valves, iii) pressure relief valves (PRV), iv) meters, v) gauges, vi) regulators, vii) pneumatic device vents, and viii) compressor vents (e.g., distance piece vents [DPVs] and rod packing vents [RPVs]). Components were screened for the presence of leaks and venting emissions with an optical gas imaging (OGI) camera, and methane emission rates were measured using a microdilution high volume sampler. Downwind emissions were measured using an Open Path Fourier Transform Infrared (OP-FTIR) Spectrometer. Data were evaluated to assess correlation with site, equipment, time, and operational variables. Key findings and recommendations from the study include: A) Different counting methodologies can result in vastly different component counts, thus influencing total emissions calculations using Subpart W population EFs. A standard methodology should be adopted for classifying and counting components in order to minimize inconsistencies across studies and instruct stakeholders responsible for GHGI reporting. B) Results support current component subcategories listed in USEPA Subpart W, including the subdivision of connectors (flanged and “other”) and pneumatic device vents (intermittent, continuous low bleed, and continuous high bleed). C) Emission rates vary across sites and a relationship between higher emissions and compressor age was observed for some components. D) Component emission rates varied between field campaigns. The type of components contributing to overall measured emissions also varied among field campaigns. However, the emission rate variability was larger between different components (of the same category) than the variability in one component over the four field campaigns. Therefore, when calculating emission factors, it is not necessary to take repeat measurements to capture component variability. E) Measuring the emission rate of a sample for an extended period of time is not necessary to capture the average component emission rate. F) For reporting purposes, excluding liquid lines from site-wide screening may have a negligible effect on component-related emissions. However, from a site management perspective, malfunctioning components were not uncommon on liquid lines and contributed substantially to fugitive emissions at some sites. G) Population EFs, whether including or excluding liquid lines, were a conservative estimate of fugitive emissions. Leaker EFs consistently underestimated emissions at the field sites. Measurements at more sites, particularity sites in other areas of the country, need to be completed before determining the accuracy of EFs.

03 NATURAL GAS↗

DOE OSTI2025

Biomass burning emission analysis based on MODIS aerosol optical depth and AeroCom multi-model simulations: implications for model constraints and emission inventories

We assessed the biomass burning (BB) smoke aerosol optical depth (AOD) simulations of 11 global models that participated in the AeroCom phase III BB emission experiment. By comparing multi-model simulations and satellite observations in the vicinity of fires over 13 regions globally, we (1) assess model-simulated BB AOD performance as an indication of smoke source–strength, (2) identify regions where the common emission dataset used by the models might underestimate or overestimate smoke sources, and (3) assess model diversity and identify underlying causes as much as possible. Using satellite-derived AOD snapshots to constrain source strength works best where BB smoke from active sources dominates background non-BB aerosol, such as in boreal forest regions and over South America and southern hemispheric Africa. The comparison is inconclusive where the total AOD is low, as in many agricultural burning areas, and where the background is high, such as parts of India and China. Many inter-model BB AOD differences can be traced to differences in values for the mass ratio of organic aerosol to organic carbon, the BB aerosol mass extinction efficiency, and the aerosol loss rate from each model. The results point to a need for increased numbers of available BB cases for study in some regions and especially to a need for more extensive regional-to-global-scale measurements of aerosol loss rates and of detailed particle microphysical and optical properties; this would both better constrain models and help distinguish BB from other aerosol types in satellite retrievals. More generally, there is the need for additional efforts at constraining aerosol source strength and other model attributes with multi-platform observations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1997

Sulfur in Cometary Dust

The computer-intensive project consisted of the analysis and synthesis of existing data on composition of comet Halley dust particles. The main objective was to obtain a complete inventory of sulfur containing compounds in the comet Halley dust by building upon the existing classification of organic and inorganic compounds and applying a variety of statistical techniques for cluster and cross-correlational analyses. A student hired for this project wrote and tested the software to perform cluster analysis. The following tasks were carried out: (1) selecting the data from existing database for the proposed project; (2) finding access to a standard library of statistical routines for cluster analysis; (3) reformatting the data as necessary for input into the library routines; (4) performing cluster analysis and constructing hierarchical cluster trees using three methods to define the proximity of clusters; (5) presenting the output results in different formats to facilitate the interpretation of the obtained cluster trees; (6) selecting groups of data points common for all three trees as stable clusters. We have also considered the chemistry of sulfur in inorganic compounds.

Fomenkova, M. N.↗

NASA NTRS2013

Historical and Future Black Carbon Deposition on the Three Ice Caps: Ice Core Measurements and Model Simulations from 1850 to 2100

Ice core measurements in conjunction with climate model simulations are of tremendous value when examining anthropogenic and natural aerosol loads and their role in past and future climates. Refractory black carbon (BC) records from the Arctic, the Antarctic, and the Himalayas are analyzed using three transient climate simulations performed with the Goddard Institute for Space Studies ModelE. Simulations differ in aerosol schemes (bulk aerosols vs. aerosol microphysics) and ocean couplings (fully coupled vs. prescribed ocean). Regional analyses for past (1850-2005) and future (2005-2100) carbonaceous aerosol simulations focus on the Antarctic, Greenland, and the Himalayas. Measurements from locations in the Antarctic show clean conditions with no detectable trend over the past 150 years. Historical atmospheric deposition of BC and sulfur in Greenland shows strong trends and is primarily influenced by emissions from early twentieth century agricultural and domestic practices. Models fail to reproduce observations of a sharp eightfold BC increase in Greenland at the beginning of the twentieth century that could be due to the only threefold increase in the North American emission inventory. BC deposition in Greenland is about 10 times greater than in Antarctica and 10 times less than in Tibet. The Himalayas show the most complicated transport patterns, due to the complex terrain and dynamical regimes of this region. Projections of future climate based on the four CMIP5 Representative Concentration Pathways indicate further dramatic advances of pollution to the Tibetan Plateau along with decreasing BC deposition fluxes in Greenland and the Antarctic.

Antarctic Regions↗

DOE OSTI2020

High Synteny and Sequence Identity between Genomes of Nitrosococcus oceani Strains Isolated from Different Oceanic Gyres Reveals Genome Economization and Autochthonous Clonal Evolution

The ammonia-oxidizing obligate aerobic chemolithoautotrophic gammaproteobacterium, Nitrosococcus oceani, is omnipresent in the world’s oceans and as such important to the global nitrogen cycle. We generated and compared high quality draft genome sequences of N. oceani strains isolated from the Northeast (AFC27) and Southeast (AFC132) Pacific Ocean and the coastal waters near Barbados at the interface between the Caribbean Sea and the North Atlantic Ocean (C-27) with the recently published Draft Genome Sequence of N. oceani Strain NS58 (West Pacific Ocean) and the complete genome sequence of N. oceani C-107, the type strain (ATCC 19707) isolated from the open North Atlantic, with the goal to identify indicators for the evolutionary origin of the species. The genomes of strains C–107, NS58, C-27, and AFC27 were highly conserved in content and synteny, and these four genomes contained one nearly sequence-identical plasmid. The genome of strain AFC132 revealed the presence of genetic inventory unknown from other marine ammonia-oxidizing bacteria such as genes encoding NiFe-hydrogenase and a non-ribosomal peptide synthetase (NRPS)-like siderophore biosynthesis module. Comparative genome analysis in context with the literature suggests that AFC132 represents a metabolically more diverse ancestral lineage to the other strains with C-107 and NS58 potentially being the youngest. The results suggest that the N. oceani species evolved by genome economization characterized by the loss of genes encoding catabolic diversity while acquiring a higher redundancy in inventory dedicated to nitrogen catabolism, both of which could have been facilitated by their rich complements of CRISPR/Cas and Restriction Modification systems.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS2011

Portable Multigas Monitors for International Space Station

The Environmental Health System (EHS) on International Space Station (ISS) includes portable instruments to measure various cabin gases that acutely impact crew health. These hand-held devices measure oxygen, carbon dioxide, carbon monoxide, hydrogen chloride and hydrogen cyanide. The oxygen and carbon dioxide units also serve to back up key functions of the Major Constituent Analyzers. Wherever possible, commercial off-the-shelf (COTS) devices are employed by EHS to save development and sustaining costs. COTS hardware designed for general terrestrial applications however has limitations such as no pressure compensation, limited life of the active sensor, calibration drift, battery issues, unpredictable vendor support and obsolescence. The EHS fleet (inflight and ground inventory) of instruments is both aging and dwindling in number. With the retirement of the US Space Shuttle, maintenance of on-orbit equipment becomes all the more difficult. A project is underway to search for gas monitoring technology that is highly reliable and stable for years. Tunable Diode Laser Spectroscopy (TDLS) seems to be the front-runner technology, but generally is not yet commercially available in portable form. NASA has fostered the development of TDLS through the Small Business Innovative Research (SBIR) program. A number of gases of interest to the aerospace and submarine communities can be addressed by TDLS including the list mentioned above plus hydrogen fluoride, ammonia and water (humidity). There are several different forms of TDLS including photoacoustic and direct absorption spectroscopy using various multipass cell geometries. This paper describes the history of portable gas monitoring on NASA spacecraft and provides a status of the development of TDLS based instruments. Planned TDLS flight experiments on ISS could lead both to operational use on ISS and important roles in future Exploration spacecraft and habitats.

Mudgett, Paul D.↗

NASA NTRS2012

Use of Heritage Hardware on Orion MPCV Exploration Flight Test One

Due to an aggressive schedule for the first space flight of an unmanned Orion capsule, currently known as Exploration Flight Test One (EFT1), combined with severe programmatic funding constraints, an effort was made within the Orion Program to identify heritage hardware, i.e., already existing, flight-certified components from previous manned space programs, which might be available for use on EFT1. With the end of the Space Shuttle Program, no current means exists to launch Multi-Purpose Logistics Modules (MPLMs) to the International Space Station (ISS), and so the inventory of many flight-certified Shuttle and MPLM components are available for other purposes. Two of these items are the MPLM cabin Positive Pressure Relief Assembly (PPRA), and the Shuttle Ground Support Equipment Heat Exchanger (GSE HX). In preparation for the utilization of these components by the Orion Program, analyses and testing of the hardware were performed. The PPRA had to be analyzed to determine its susceptibility to pyrotechnic shock, and vibration testing had to be performed, since those environments are predicted to be more severe during an Orion mission than those the hardware was originally designed to accommodate. The GSE HX had to be tested for performance with the Orion thermal working fluids, which are different from those used by the Space Shuttle. This paper summarizes the activities required in order to utilize heritage hardware for EFT1.

Rains, George Edward↗

DOE OSTI2025

First experimental determination of the ⁴⁰Ar(𝑛, 2𝑛)³⁹Ar reaction cross section and ³⁹Ar production in Earth’s atmosphere

The cosmogenic ³⁹Ar(t1∕2 = 268 years) isotope of argon is used for geophysical dating and tracing of underground and ocean water, as well as ice owing to its appropriate half-life and chemical inertness as a noble gas; ³⁹Ar serves also in nuclear weapon test monitoring. We measured for the first time the total cross section of the main ³⁹Ar cosmogenic production reaction in the atmosphere, namely ⁴⁰Ar(𝑛, 2𝑛)39 Ar, using 14.8 ± 0.3 MeV neutrons. The neutrons, produced by a deuterium-tritium generator, impinged on a stainless steel sphere filled with Ar gas highly enriched in the ⁴⁰Ar isotope and were monitored by a stack of fast-neutron activation foils. The reaction yield was measured by atom counting of long-lived ³⁹Ar with noble gas accelerator mass spectrometry and, independently, by decay counting relative to atmospheric argon (³⁹Ar/Ar= 8.12 × 10−16 ). A total ⁴⁰Ar(𝑛, 2𝑛)39 Ar cross section of 610 ± 100 mb was determined at 14.8 ± 0.3 MeV incident neutron energy. This result serves as a benchmark for recent theoretical calculations and evaluations, found to reproduce well the experimental total cross section. We use these energy-dependent theoretical cross sections together with experimental spectra of cosmogenic neutrons at different altitudes to calculate the global average rate of neutron-induced ³⁹Ar atmospheric production, resulting in 770 ± 240 39 Ar atoms/cm²/day. The secular equilibrium between the ³⁹Ar calculated production rate and radioactive decay rate leads to a partial isotopic abundance ³⁹Ar/Ar = (5.9 ± 1.8) × 10−16 , showing that ≈73% of atmospheric ³⁹Ar is produced by cosmogenic neutrons, the remaining part believed to be induced by muons and high-energy 𝛾 rays. The ⁴⁰Ar(𝑛, 2𝑛)³⁹Ar cross section at 14 MeV is also a key parameter for quantifying the anthropogenic contribution to atmospheric 39 Ar produced during the thermonuclear tests of the 1960s. We estimate that anthropogenic ³⁹Ar accounts for roughly 20% of the present atmospheric inventory.

39 Ar atmospheric production↗

NASA NTRS2011

Use of Heritage Hardware on MPCV Exploration Flight Test One

Due to an aggressive schedule for the first orbital test flight of an unmanned Orion capsule, known as Exploration Flight Test One (EFT1), combined with severe programmatic funding constraints, an effort was made to identify heritage hardware, i.e., already existing, flight-certified components from previous manned space programs, which might be available for use on EFT1. With the end of the Space Shuttle Program, no current means exists to launch Multi Purpose Logistics Modules (MPLMs) to the International Space Station (ISS), and so the inventory of many flight-certified Shuttle and MPLM components are available for other purposes. Two of these items are the Shuttle Ground Support Equipment Heat Exchanger (GSE Hx) and the MPLM cabin Positive Pressure Relief Assembly (PPRA). In preparation for the utilization of these components by the Orion Program, analyses and testing of the hardware were performed. The PPRA had to be analyzed to determine its susceptibility to pyrotechnic shock, and vibration testing had to be performed, since those environments are predicted to be significantly more severe during an Orion mission than those the hardware was originally designed to accommodate. The GSE Hx had to be tested for performance with the Orion thermal working fluids, which are different from those used by the Space Shuttle. This paper summarizes the certification of the use of heritage hardware for EFT1.

Rains, George Edward↗

NASA NTRS2009

An Algorithm for Obtaining the Distribution of 1-Meter Lightning Channel Segment Altitudes for Application in Lightning NOx Production Estimation

An algorithm has been developed to estimate the altitude distribution of one-meter lightning channel segments. The algorithm is required as part of a broader objective that involves improving the lightning NOx emission inventories of both regional air quality and global chemistry/climate models. The algorithm was tested and applied to VHF signals detected by the North Alabama Lightning Mapping Array (NALMA). The accuracy of the algorithm was characterized by comparing algorithm output to the plots of individual discharges whose lengths were computed by hand; VHF source amplitude thresholding and smoothing were applied to optimize results. Several thousands of lightning flashes within 120 km of the NALMA network centroid were gathered from all four seasons, and were analyzed by the algorithm. The mean, standard deviation, and median statistics were obtained for all the flashes, the ground flashes, and the cloud flashes. One-meter channel segment altitude distributions were also obtained for the different seasons.

Peterson, Harold↗

DOE OSTI2022

Choosing the Best Carbon Factor for the Job: Exploring Available Carbon Emissions Factors and the Impact of Factor Selection

Over 600 local governments in the United States, including nearly half of the largest 100 cities, have enacted climate action plans that include carbon reduction goals and greenhouse gas inventories (Markolf et al. 2020). The magnitude of these goals ranges from modest reduction targets to carbon neutrality. None will be met without significant contributions from the buildings sector. Understanding how energy efficiency and building electrification impact greenhouse gas emissions requires local, time-sensitive, and forward-looking carbon emissions factors for electricity use in buildings. There are a variety of emissions factors currently available from various sources, including average emissions factors and historical short-run marginal emissions factors. Long-run marginal emissions factors and future-year short-run marginal emissions factors are also now available from the National Renewable Energy Laboratory's (NREL's) Cambium data sets. In this paper, we describe the different carbon emissions factors available, including both conventional sources and newly available options. We discuss the types of analyses each emissions factor is best suited to support. Then, using residential energy efficiency and electrification load profiles, we demonstrate how different conclusions result from different choices of carbon emissions factors. For two grid regions, we explore takeaways of using current versus future-year emissions, short-run versus long-run, and levelized versus single-year values. We include a framework for selecting the best carbon emissions factor for the job.

carbon emissions factors↗

DOE OSTI2017

Opportunities and limits of Decay storage based on Dismantled Materials in Nuclear Power Plants - 17650

We investigate the potential of decay storage of low and intermediate radioactive waste for release procedures. We present the Safetec software tool HL3 and its application to data from the German nuclear power plant at the site in Stade. In general, during the dismantling process of nuclear power plants, waste of slightly contaminated and/or activated systems is produced in large amounts. These are in particular demolition rubble from concrete structures and ingots from the melting process of metals. If, at the time of disposal, the nuclear inventory is near or slightly above federal clearance limits, the material cannot be released as conventional waste. However, due to the decline of the nuclear inventory over time, a significant amount of that waste could qualify for the release procedure in the future. Although this concept of decay storage is well known, specific predictions of the mass flow to be released is non-trivial. The mass flow over time depends on the composition of known and assumed nuclides (nuclide vector), as well as on the underlying threshold values for release. To handle the waste stream as a function of time, the nuclide composition and specific threshold values, Safetec developed a bespoke software tool named HL3. Its primary function is to visualize and to test/analyze various nuclide vectors and its decompositions over time. For the application within German law, threshold values according to the different disposal routes can be considered. Using the batch interface in the software tool HL3, large amounts of data can be automatically analyzed in a traceable and quick way. To test both, the tool and the benefit for the concept of decay storage, we have applied our code HL3 to material from the dismantling of the pressurized-water reactor at the site in Stade, Germany. We set the focus on concrete debris and metal ingots, which in principle are best suited for decay storage over years. The assignment and the packaging of that waste from Stade were based on application documents for decommissioning of the Year 2000 and according to the state of art conditioning technique at that time. Based on the data of that waste and the appropriate disposal routes, we calculate and discuss the amount of waste releasable after decay storage. As for the situation in Germany, we find that only a negligible amount would be releasable, mainly due to other reasons. These are the deterioration of detectability of radionuclides with time, and other regulatory conditions. However, on an international scale, a different assessment can be drawn. Our results thus motivate to reconsider the option of interim decay storage to reduce radioactive waste in large amounts. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2024

Choosing the Best Carbon Factor for the Job: Exploring Available Carbon Emissions Factors and the Impact of Factor Selection: Preprint

carbon emissions factors↗

DOE OSTI2022

SCALE Analysis of a Fluoride Salt-Cooled High-Temperature Reactor in Support of Severe Accident Analysis

As part of a US Nuclear Regulatory Commission–sponsored project to assess the modeling and simulation capabilities for accident progression, source term, and consequence analysis for advanced reactor technologies with SCALE and MELCOR, SCALE was used for the modeling and simulation of a fluoride salt-cooled high-temperature reactor (FHR). Based on the preconceptual design for a small modular 236 MWth FHR developed by the University of California, Berkeley (PB-FHR-Mk1), a SCALE model of the PB-FHR-Mk1 reactor core was developed. The reactor was modeled at equilibrium state with different fuel compositions in different regions of the reactor. An iterative approach was used to interpolate and mix the burnup-dependent fuel compositions obtained through the depletion calculation of a core slice model. After demonstrating the applicability of SCALE’s multigroup (MG) approach for the simulation of the PB-FHR-Mk1, the resulting equilibrium core was studied in terms of the power profile, the flux profile, temperature reactivity coefficients, and the xenon reactivity. Furthermore, the tritium production rate in the salt coolant was determined, and the dependence of the one-group cross sections on the burnup and location in the reactor core was studied. The results obtained with SCALE were post-processed to provide the MELCOR team with the core inventory and decay heat of the equilibrium core, a zone-wise power profile, temperature feedback coefficients, the tritium production rate, and the xenon worth.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗