Enriched Uranium Research Articles

Geochemical and U-Pb isotopic insights into uranium (U) enrichment in the soil around a nuclear fuel element plant, in Southwest China

To assess the impact of nuclear fuel element processing on uranium(U) in the soil environment, a geochemical survey was conducted. The survey provided data on U concentration, speciation, Th/U ratio, and U and Pb isotopic composition in the soil around a nuclear fuel processing plant in Southwest China, which has been operational since 1965, to reveal the enrichment status and sources of U in the soil. The concentrations of Th and Pb in the soil were also compared. The average U concentration was 1.01-1.43 times that of the local background, and U existed primarily as residual U. The enrichment factor value indicates that U is slightly enriched in the soil. The Th/U ratio was higher than the crustal ratio and the world soil average value, indicating that some of the U in the soil has been lost due to surface runoff. The 235U/238U ratio distribution shows that a certain amount of 235U-enriched particles have sedimentation in the downwind direction of the plant soil, which results in a higher 235U/238U ratio in this direction. However, in general, the 235U/238U ratios were observed to be typical natural values. The 207Pb/206Pb ratio indicates that the U in the U ore enters the soil during nuclear fuel processing.

Abstract P37: Decoding Cancer Dependency and Molecular Pathways of Long Noncoding RNAs with a Novel CRISPR-Cas13d Platform

Abstract Long noncoding RNAs (lncRNAs) constitute a significant portion of the human transcriptome, yet their precise role in tumor cells remains elusive. In our study focusing on multiple myeloma (MM), we employed the CRISPR-Cas13d endonuclease's RNA-targeting capabilities to establish an innovative functional transcriptomics screening platform. This platform facilitated the comprehensive identification of tumor-promoting lncRNAs (tp-lncRNAs) in MM cells and provided mechanistic insights. Utilizing RNA-seq data from 319 MM patients, we identified 5,304 expressed lncRNAs. Subsequently, we designed and implemented a pooled lentiviral library incorporating nine single-guide RNAs (sgRNAs) per identified lncRNA, alongside 500 non-targeting sgRNAs as negative controls and nine sgRNAs targeting established protein-coding oncogenes in MM (e.g., IRF4) as positive controls. This library was introduced at a low multiplicity of infection (MOI < 0.3) across five MM cell lines, each expressing a Cas13d-GFP fusion protein. After three weeks, deep sequencing and MAGeCK assessed sgRNA depletion/enrichment in MM cells. Our findings revealed ~600 tp-lncRNAs upon which MM cell lines demonstrated significant growth dependency, constituting around 12% of the identified lncRNA transcriptome. Notably, this surpassed the previous estimation of 3–5%, with considerable overlap across MM cell lines. The dependency score of numerous tp-lncRNAs rivaled or exceeded that of the positive control IRF4. To validate dependencies, we employed a library of 3,500 sgRNAs to target 314 tp-lncRNAs in vitro and in xenograft models. This approach was also applied to a panel of six non-MM cancer cell lines, identifying a broad tumor-dependency on >59 lncRNAs and a specific MM-dependency on a smaller subset of lncRNAs. We explored the sub-cellular localization and site-of-function of tp-lncRNAs using a Cas13d variant accumulating either in the cytosol or in the nucleus, coupled with sub-cellular RNA-seq and single-molecule RNA FISH. Confirming the functionality and nuclear enrichment of most tp-lncRNAs, we identified >20 hits providing dependency in the cytosol. Our investigation also unveiled multiple transcript variants within the lncRNA transcriptome, originating from the same lncRNA genes but differing in sequences, structures, and likely functions. Crucially, our screening platform precisely identified tp-lncRNA isoform(s) conferring dependencies. Finally, we combined short-term Cas13d screens with single-cell RNA-seq in H929 MM cells. Analysis of over 20,000 cells for gRNA and transcript expression enabled us to delineate molecular pathways linked to individual perturbations of over 30 lncRNAs in a single experiment. The modulated pathways included therapeutically relevant ones, such as the unfolded protein response or mitochondrial homeostasis, further suggesting a potential therapeutic benefit from targeting tp-lncRNAs. In summary, our novel platform offers a comprehensive delineation of tumor dependency on lncRNAs in MM, providing valuable insights to guide further mechanistic inquiries. Citation Format: Eugenio Morelli, Anil Aktas-Samur, Domenico Maisano, Claire Gao, Na Liu, Vanessa Favasuli, Marcello Turi, Pietro Folino, Liang Chen, Francesca Barello, Mariateresa Fulciniti, Annamaria Gulla, Kenneth Anderson, Mehmet Kemal Samur, Nikhil Munshi. Decoding Cancer Dependency and Molecular Pathways of Long Noncoding RNAs with a Novel CRISPR-Cas13d Platform [abstract]. In: Proceedings of the Blood Cancer Discovery Symposium; 2024 Mar 4-6; Boston, MA. Philadelphia (PA): AACR; Blood Cancer Discov 2024;5(2_Suppl):Abstract nr P37.

Bioinspired electrostatic layer-by-layer assembly membranes constructed based on mild strategy for uranium extraction from seawater

Developing simple and efficient new strategies for uranium extraction from seawater (UES) is crucial for addressing the energy crisis. Here, we proposed a mild strategy to prepare a layer-by-layer assembly membrane (LAM) by polydopamine (PDA) and polyethyleneimine (PEI) co-deposition coupled with polyethyleneimine/phytic acid self-assembly for efficient uranium extraction. By regulating the number of self-assemblies, the performance of the membrane could be easily adjusted. The functional coating’s rich active groups (–NH2, -PO43-, –OH) provided a good adsorption performance for the modified membrane, with a static adsorption capacity of 142.25 mg·g−1. Meanwhile, it possessed excellent dynamic removal rate, which could achieve over 90 % uranium removal within 90 min. The LAM also exhibited exceptional adsorption selectivity, boasting a remarkable 9:1 ratio in extracting uranium and vanadium. Furthermore, the strong adhesion of PDA endowed the material with good stability, and the adsorption capacity only decreased by 23 % after 5 cycles. DFT calculations proved that PEI/PA-U was the most stable model. Particularly, the adsorption capacity of LAM in natural seawater can reach 0.99 mg·g−1. With the simple and mild preparation process, along with the excellent adsorption performance, the LAM membrane holds great promise for seawater uranium enrichment.

Neutronic performance of 208Pb-Bi eutectic-cooled fast reactor with uranium nitride fuel (enriched 15N)

Fast reactors (FRs) require more uranium enrichment than LWRs and fuel reprocessing. The solution proposed to address these issues is to use the modified CANDLE burnup scheme on the reactor core. The use of uranium nitride (UN) as fuel was proposed because the UN fuel has several advantages, such as high melting point, high heavy metal density, and large thermal conductivity. However, using UN as a fuel can produce the radioactive isotope 14C via the reaction 14N (n, p)14C. Therefore, in this study, a neutronic analysis was performed in a modified CANDLE fast reactor employing UN and UN (enriched 15N) as fuel using SRAC. The modified CANDLE fast reactor fuelled with UN (99% 15N) has a higher keff than the UN-fuelled reactor with similar parameters. Similarly, the atomic density of fissile nuclides and power density are higher because the 15N isotope has a smaller neutron capture cross-section than the 14N isotope.

Abstract PR008: Location, location, location: Why cellular localization of mutant β-catenin matters in endometrial cancer

Abstract The present study aims to understand the mechanisms of mutant β-catenin in endometrial cancer (EC) patients with exon 3 CTNNB1 mutations. Endometrial cancer patients with exon 3 CTNNB1 mutations tend to be younger in age and have low cancer grades, but they exhibit worse recurrence-free survival than patients with similar clinical characteristics. It is unknown why EC patients with CTNNB1 mutations have worse survival. CTNNB1 encodes the protein β-catenin, which functions primarily at the cell membrane in the adherens junction complex and in the Wnt signaling pathway, where it localizes in the cytoplasm or nucleus. Exon 3 CTNNB1 mutations in EC are classically thought to promote nuclear localization of β-catenin. In this study, we conducted immunohistochemistry for β-catenin localization on 53 EC cases with an exon 3 CTNNB1 mutation from the UNCseq project. Surprisingly, 32 cases had primarily non-nuclear, either cytoplasmic or membranous, localization and 21 cases had primarily nuclear localization. Additionally, we identified 16 cases with intratumoral heterogeneity containing both nuclear and non-nuclear β-catenin localization. To investigate the functional consequences of this differential localization, we performed spatial transcriptomics using the Nanostring GeoMx Whole Transcriptome Analysis. Nuclear and non-nuclear regions of interest (ROI) were selected from 16 CTNNB1 mutant EC cases exhibiting heterogenous β-catenin localization within the same tissue (n=95 total ROIs). We hypothesize that β-catenin nuclear and non-nuclear ROIs will have differing transcriptional outputs in CTNNB1 mutant EC. Differential expression analysis of all ROIs yielded distinct transcriptional profiles based on localization of mutant β-catenin. Gene Set Enrichment Analysis revealed enrichment for Wnt-signaling and the epithelial-to-mesenchymal transition pathways in nuclear ROIs and enrichment for estrogen and androgen signaling pathways in non-nuclear ROIs. Hierarchical clustering of all ROIs yielded two genetically distinct clusters comprised of entirely nuclear or non-nuclear ROIs, with the exception of four ROIs. Higher expression of TACSTD2, encoding the protein Trop2, was enriched in the nuclear ROI cluster. Trop2 is the target of Sacituzumab Govitecan (SG), a drug conjugate with recent success in metastatic triple negative breast cancer patients. Additionally, studies have shown Trop2 to induce nuclear localization of β-catenin in other cancer types. Therefore, we hypothesize that CTNNB1 mutant EC patients with nuclear localization of β-catenin will respond better to SG treatment. To conclude, we established gene expression profiles for areas of nuclear and non-nuclear β-catenin in CTNNB1 mutant EC tissues and identified a novel gene with implications in mechanisms of β-catenin localization which may allow therapeutic targeting of advanced disease. Citation Format: Molly L. Parrish, Andrew B. Gladden, Russell R. Broaddus. Location, location, location: Why cellular localization of mutant β-catenin matters in endometrial cancer [abstract]. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(5_Suppl):Abstract nr PR008.

Neutronics Analysis of SMART Reactor Fuel Cell and Fuel Assemblies with Two Absorber Materials: Gd2O3 – UO2 and Al2O3 – B4C Using SRAC Code and JENDL 3.3 and 4.0 Data Libraries

The SMART is a small modular nuclear reactor which has been developed by South Korea’s KAERI, utilizes 4.95% enriched uranium fuel and two types of absorber materials: Gd2O3 - UO2 and Al2O3 - B4C. This research focuses on the neutronic analysis of SMART at the fuel cell and fuel assembly levels using SRAC 2006 with JENDL 3.3 and 4.0 Nuclear Data Libraries. The study aims to compare the neutronic performance of the SMART fuel assembly using these two absorber materials. At the fuel level, three types of enrichment are considered: 2.82%, 3.25%, and 4.95%. Meanwhile, at the fuel assembly level, three types (A, B, and C) are investigated, based on the composition of fuel rods and absorber material rods. The results indicate that the SMART reactor with the KAERI design (enrichment of 4.95% and 3 types of fuel assemblies) can maintain critical conditions for 990 days (equivalent to 3 years) of operation for small modular reactor types. The two types of absorber materials are effective in absorbing excess positive reactivity from the fuel effectively. The use of absorbing materials greatly determines the neutronic characteristics and costs in the construction of nuclear reactors, It can be compared that using 2 absorbing materials can reduce the value of the effective multiplication factor and the infinitive neutron production in the core compared to using 1 absorbing material.

Irregular, Backward-Compatible PWR Assembles with More Pins to Facilitate Uprates

Increasing the number of pins within a pressurized water reactor (PWR) assembly reduces pin temperature for a given assembly power. In conjunction with a core retrofit, this presents a potential route to PWR uprate, which is of growing interest given recent increases in electricity prices. However, most PWRs utilize regular lattice designs with fixed guide tube positions, such as the very common 17 × 17 lattice design with 25 guide/instrumentation tubes. These tubes are aligned with penetrations in the reactor pressure vessel, which presents a prohibitive obstacle to retrofit, and more widely, may “lock” many PWRs to this particular fuel configuration. In this paper, an irregular PWR fuel assembly is proposed. It is shown that a backward-compatible lattice with 324 fuel pins per assembly (BL324), uniform enrichment, and the same hydrogen-to–heavy metal ratio as a reference 17 × 17 assembly with 264 fuel pins can achieve within-assembly power peaking within 2% of the reference assembly under equivalent conditions while fixing the guide tube positions. Power peaking can be further reduced to reach that of the existing fuel assembly by reducing the enrichment of 36 of the pins by 0.2 wt%. The fuel assembly could potentially either support a significant uprate of up to ~20% in conjunction with low-enriched uranium plus (LEU+) fuel or a more aggressive cycle design, and hence, improved discharge burnup at the same power and batch strategy. A subchannel analysis shows that the coolant heat-up distribution is comparable to the reference assembly. However, the pressure drop is estimated to be 4% higher, which would challenge the performance of transition cores containing both 17 × 17s and BL324s. Further incremental changes to BL324 may be attractive, either to improve manufacturability or to slightly improve performance through formal optimization.

Enrichment measurement by passive γ-ray spectrometry of uranium dioxide fuel pellets using a europium-doped, strontium iodide scintillator

The performance of a europium-doped strontium iodide scintillator for uranium enrichment measurement of a variety of sintered uranium dioxide fuel pellets is described and compared to that of caesium iodide and sodium iodide. Enrichment has been determined via passive γ-ray spectrometry of the 186 keV line from uranium-235 using gross count, net count, and peak ratio analyses. The 38 mm Ø x 38 mm strontium iodide crystal demonstrates superior energy resolution (3.43 ± 0.03% at 662 keV) and competitive detection efficiency for its size in the energy range of interest for uranium enrichment analysis (<250 keV). It demonstrates better χv2 and coefficient of determination values than caesium iodide and sodium iodide when measuring uranium enrichment using the gross- and net-count from the 186 keV emission. It is shown to have the least measurement variance of the three scintillators studied in determining the uranium enrichment of pellets in a blind test, with a relative error comparative to sodium iodide and smaller than caesium iodide. This research heralds the potential of strontium iodide in passive γ-ray uranium enrichment applications.

Preliminary analysis of the core design for Indonesia Micro Reactor (IMR-13)

The development of microreactor technology can meet the energy needs of specific regions of Indonesia’s underdeveloped, foremost, and outermost areas. One of the latest microreactor designs is the Indonesia Micro Reactor (IMR-13), which has seed and blanket fuel and 5MWt power generation. The IMR-13 reactor has characteristic design features for operation for as many as ten years without refuelling. The reactor core comprises integral fuel elements consisting of a heat pipe, fuel matrix, fuel cladding, and graphite moderator. There are two fuel element types: seed fuel elements with 19.75 % low-enriched uranium oxide and blanket fuel elements with thorium oxide – graphite reflectors on the bottom, sides, and top surround the reactor core. Side reflectors have moving parts that function to regulate reactor power. There are no active components in this reactor. Heat transfer occurs by natural circulation in the heat pipe to the molten salt pool and then from the molten salt pool to the steam generator. This research focuses on the neutronic aspect of the reactor, particularly in calculating the seed and blanket ratio to allow the reactor to operate for ten years with minimal power peaking factor. The selected variant model has 979 seeds and 294 blankets. The variation model has a value of excess reactivity at the beginning of the life of 937 pcm. Each value of the shutdown margin for system first and system second sequentially is 3020 pcm and 2994 pcm. The temperature reactivity coefficient is negative, implying inherent safety. At the end of life, the burnup value was achieved at 4.97 GWd/MTU with an excess reactivity of 271 pcm. A parameter analysis of the burnup characteristics will follow in the selected variant model. The parameters examined were the core power distribution, delayed neutrons, the fast fission factor, conversion ratio, and decay heat.

Analysis of variation minor actinide pin configurations Np-237, AM-241, and Cm-244 in UN-PuN fueled pressurized water reactor

Actinide minor is a reactor waste with high toxicity and a long half-life. Minor actinides can be reduced by reusing them as fuel mixtures in reactors. This research uses PWR reactors with the primary fuel UN-PuN or Uranium Plutonium Nitride with a burning time of 5 years. The fuel consists of enriched Uranium, reactor-grade Plutonium from LWR waste, and minor actinides including Neptunium-237, Americium-241, and Curium-244. The purpose of this study was to find a design that is effective in reducing minor actinide waste. There are six designs or cases used in the addition of minor actinides. Each case has six minor actinide pins in each assembly. The addition of minor actinides is arranged in heterogeneous cores. The analysis was carried out by observing the values of k-eff, excess reactivity, and mass of minor actinides obtained from simulations using OpenMC code 0.13.2 and the ENDF/B-VIII library. The homogeneous core obtained an excess reactivity of 9.7 % with a percentage of plutonium of 8 %. The results of the homogeneous core are used as a reference for preparing a heterogeneous core. The heterogeneous core obtained an excess reactivity of 9.9 % with a percentage of plutonium F1: 5.5 %, F2: 8 %, and F3: 10.5 %. Np-237 can be reduced by 53 kg, and Am-241 can be reduced by 61 kg with minor actinide pins in case 1. Cm-244 can be reduced by 363 kilograms with minor actinide pins in case 6. Excess reactivity in the addition of Np-237 and Am-241 decreased to 5.3 %, while the accumulation of Cm-244 increased to 12.1 %.

Nuclear and cytoplasmic specific RNA binding proteome enrichment and its changes upon ferroptosis induction

The key role of RNA-binding proteins (RBPs) in posttranscriptional regulation of gene expression is intimately tied to their subcellular localization. Here, we show a subcellular-specific RNA labeling method for efficient enrichment and deep profiling of nuclear and cytoplasmic RBPs. A total of 1221 nuclear RBPs and 1333 cytoplasmic RBPs were enriched and identified using nuclear/cytoplasm targeting enrichment probes, representing an increase of 54.4% and 85.7% compared with previous reports. The probes were further applied in the omics-level investigation of subcellular-specific RBP-RNA interactions upon ferroptosis induction. Interestingly, large-scale RBPs display enhanced interaction with RNAs in nucleus but reduced association with RNAs in cytoplasm during ferroptosis process. Furthermore, we discovered dozens of nucleoplasmic translocation candidate RBPs upon ferroptosis induction and validated representative ones by immunofluorescence imaging. The enrichment of Tricarboxylic acid cycle in the translocation candidate RBPs may provide insights for investigating their possible roles in ferroptosis induced metabolism dysregulation.

Evaluating Hydrogen-based Moderators in High-Temperature Gas-cooled Reactors with 5 wt% Enriched Uranium Annular Fuel Rods

Abstract Small Modular Reactors (SMRs) based on high temperature gas-cooled reactor (HTGR) technology are being developed for providing high-temperature process heat and high-efficiency (&amp;amp;gt;40%) electrical power generation. However, most of the HTGR-SMR concepts require high assay low enriched uranium (HALEU) fuel, with enrichments typically above 10 wt% 235U/U, to get sufficiently high burnup levels and fuel lifetime. The need for HALEU is primarily a consequence of the low volumetric density of fissionable material in tri-structural isotropic (TRISO) fuel particles, and also the use of graphite as a moderator/reflector. A previous study has shown that a modified prismatic HTGR fuel assembly with hydrogen-based moderator (7LiH) and cylindrical fuel elements of 5 wt% 235U/U enriched uranium can greatly reduce fuel consumption of a HTGR. However, such a design concept could lead to positive temperature reactivity coefficients (TRCs), making reactor control more challenging, with reduced passive safety. The purpose of this study is to evaluate variations of the hydrogen-based moderator in this alternative fuel assembly concept to identify configurations that achieve negative TRCs, thus improving passive safety characteristics. Calculation results demonstrate that negative TRCs can be achieved with reduced hydrogen mass such that natural uranium consumption is substantially less than that of the TRISO fuel concept, with comparable or higher core life. This study also explores the option of using 7LiOH and NaOH as hydrogen-based moderators, instead of 7LiH, thus allowing operation at higher temperatures, where hydrogen TRCs are lower.

Supply security and the reliability of the Spanish generator system in the next two decades based on the costs of fossil fuels and nuclear option.

The supply security of the primary energy sources (coal, natural gas, enriched uranium…) and the reliability of the system in terms of the oscillations of the frequency and voltage are two aspects to assess in the Generation Expansion Planning. In this article, for the first criterion, the evolution of vulnerability and degree of independence of the generator system with respect to primary energy sources has been assessed by the indexes of Shannon-Weiner and energy independence, respectively. For the second approach, the evolution of the reserve margin by means the coverage index and the progression of the inertia and regulation capacity by means of its percentage regarding the total installed capacity. These four indexes have been applied on the obtained results of a stochastic lineal model developed with the software GAMS. In this model the nuclear technology has been considered as generation option in several scenarios of costs of the fossil fuels, coal and natural gas. Also, two of clean coal technologies with greater possibility of putting into service have been taken into account. The final conclusion would be that each technology carries out several functions in the generator system but not all them. That is, a generator system should have the greatest possible number of types of generation to be reliable and have supply security.

Geochemistry of iron and trace metals in seep carbonates of the middle Okinawa Trough impacted by hydrothermal plumes

Geochemistry of iron and trace metals in seep carbonates and its dependence on anaerobic oxidation of methane (AOM)-driven diagenesis in cold seeps are not well documented. Here we characterize geochemistry of Fe and trace metals in carbonate nodules collected at an active cold seep in the middle Okinawa Trough (OT) impacted by hydrothermal plumes. The carbonate nodules in the studied core are dominated by aragonite even at sulfate-low core bottom. Most aragonite at the core bottom may have formed much earlier close to the seafloor under high sulfate concentration. Additionally, porewater at the depth may not be developed to a condition for the formation of calcite dominating over aragonite due to constant downward replenishment of sulfate across through shallow SMTZ (40 cm below sediment surface). As indicated by δ13C and δ18O of the carbonates, anaerobic oxidation of thermogenic methane from gas hydrate dissociation is the dominant fluid source for carbonate precipitation. It can be inferred from the existence of vivianite that Fe reduction coupled to AOM (Fe-AOM) may have ever been prevalent at the hydrothermal Fe-impacted seep site. Enhanced inputs of Mo, Co, Cu, Ni, and Zn associated with hydrothermal Fe-oxyhydroxides-organic colloids is the main source for their high enrichment in the carbonate nodules, and clay minerals and AOM-related microbial organics may have played an important role in their partitioning in the nodules. Uranium enrichment in the carbonate nodules is mainly through enhanced U delivery associated with Fe-oxyhydroxides-scavenged organic colloids and additional U enrichment induced by U(VI) reduction. U(IV) incorporation into carbonate lattices dominates U partitioning in the carbonate nodules over the upper 60 cm of the seep sediments, but the incorporation is substantially dampened at depth due to an increase in concentration of dissolved inorganic carbon, which consequently may have rendered U(IV) adsorption on clay minerals as the important U sink in the nodules. Our results suggest that the exceptional enrichments of Co, Cu, Ni, Zn, Mo, and U in seep carbonates may be used as a paleo-proxy to differentiate cold-seep carbonates whose formation has been co-impacted by hydrothermal plumes.

A reductive strategy with ultrahigh selectivity for sequential recovery of uranium from radioactive wastewater

Uranium is valuable metal, and it is of great significance to develop a simultaneous separation process of uranium and cesium from radioactive wastewater. Herein, a process was designed to separate sequentially uranium and cesium from wastewater. By comparing the limiting ability of OH− and CO32− to Co2+, Cd2+, and Sr2+ ions, it was found that CO32− could effectively limit the above ions to the solid phase. The result of X-ray photoelectron spectroscopy (XPS) and species analysis revealed that the restriction was achieved through complexation. Through this property, more than 99.9 % of cobalt and cadmium were limited in the solid phase, and U-Cs co-separation was realized. Furthermore, the results of cyclic voltammetry and XPS indicated that U(VI) could be reduced in the liquid phase, but Cs(I) could not, which was the basis for uranium and cesium separation. And more than 99.5 % of uranium was separated from cesium by the electrochemical separation process. Simultaneously, effective separation of uranium and cesium under different pHs has been achieved via selective uranium leaching using carbonate. The co-separation combined with electrochemical separation realized the recovery of pure uranium products, indicating a large potential for realizing uranium resources in wastewater.

Forty-eight-year follow-up of a female worker exposed to highly enriched uranium via chronic and acute inhalation.

The United States Transuranium and Uranium Registries (USTUR) is a unique resource of data and materials for studying biokinetics of uranium in the human body. In this study, bioassay data and post-mortem organ activities from a female whole-body USTUR donor who was exposed to highly enriched uranium were analyzed using the IMBA Professional Plus® software to derive the best estimate of the total intake. The resulting radiation doses delivered to this individual's whole body and major target organs were calculated from estimated intake based on case-specific dose coefficients derived using the AIDE® software. Both intake and dose calculations were carried out using the biokinetic and dosimetric models recommended by the International Commission on Radiological Protection (ICRP) in its Occupational Intakes of Radionuclides publication series. Different exposure scenarios including chronic and acute inhalation intakes were tested. A combination of a chronic inhalation intake and two acute inhalation intakes appears to best describe the bioassay data. To fit this female individual's autopsy data, the transfer rate from the liver to the blood was increased by a factor of 8 and the transfer rate from the kidneys to the blood was decreased by a factor of 2.2. This resulted in the best fit to all data (p=0.519). The total intake was estimated to be 44.1kBq, and the committed effective dose was 211mSv with 96.8% contributed by 234U. 96.6% of the committed effective dose was contributed by the lungs. The remaining 3.4% of the committed effective dose was contributed by all systemic tissues and organs with the highest contribution (0.40%) from the red bone marrow. It is concluded that the current ICRP models, with the adjustment for smoking status, adequately describe uranium biokinetics for this individual except retention in the liver and kidneys. However, this study was based on a single case and may not be sufficient to identify any apparent sex-specific differences in uranium biokinetics.

HAXPES reference spectra of UO2 generated with Ga Kα x-ray source

HAXPES measurements were carried out using a Scienta Omicron HAXPES instrument to provide reference spectra for depleted uranium dioxide. High purity uranium dioxide, as confirmed by trace elemental analysis and x-ray diffraction, was synthesized via the integrated dry route from uranium hexafluoride. The material was fixed on double sided carbon tape for the analysis with charge control measures in place. The expanded energy range, using a Ga Kα x-ray source, presents core level photoelectrons not observed in traditional XPS. In addition, a region associated with the x-ray induced Auger transitions MNN is evident at binding energies only achievable with HAXPES. The reference spectra presented here act as the first in a line of proposed investigations into the comparison of XPS and HAXPES from surface to bulk as well as a fundamental understanding of the electronic structure of uranium materials.

JENDL-5.0 nuclear data sensitivity, uncertainty, and similarity analyses on the criticality of RSG GAS multipurpose research reactor

The criticality, sensitivity, uncertainty and similarity analysis of the clean, first core of the G. A. Siwabessy Multipurpose Reactor (RSG GAS), using the newly released Japanese Nuclear Data Library version 5 (JENDL-5) was conducted to contribute the validation effort of the JENDL-5, especially for the application on beryllium reflected, light-water moderated, low-enriched uranium (19.75 wt%) fueled material testing reactors. The JENDL-5 sensitivity coefficients and covariance matrices were prepared by MCNP6 and AMPX-6, respectively. The keff uncertainty was then evaluated with TSUNAMI-IP module of SCALE-6. The same module was used for similarity analysis by comparing the sensitivity data of 3,690 criticality experiments. The criticality (keff) analysis results ([C/E-1]) showed maximum overestimation of 801 pcm, 477 pcm and 547 pcm, for JENDL-5, JENDL-4.0 and ENDF/B-VIII.0, respectively. The keff uncertainty originated from the nuclear data was estimated to be 620 pcm, 644 pcm and 637 pcm for JENDL-5 only, JENDL-5 & ENDF/B-VIII.0, and ENDF/B-VIII.0 covariance data, respectively, which are comparable with the keff ([C/E-1]) values. About 125 experiment cases were found to have correlation factors of > 0.8, however, no experiment showed a strong correlation factor (>0.9), therefore, in the future criticality experiments similar to the RSG GAS should be conducted.

Design of an optimized nuclear fuel pellet

Background The design of an improved nuclear fuel pellet for use in the Westinghouse AP1000 reactor that is more powerful than existing pellets, is less expensive to manufacture, and meets Nuclear Regulatory Commission requirements for certification was undertaken to complete a senior design course in the ABET-certified nuclear engineering curriculum of Rensselaer Polytechnic Institute, Troy, NY. Methods The modeling team selected the Monte Carlo N-Particle (MCNP) program for assessing how well the pellet design achieves a k-effective value of 1, designed the base model consisting of a fuel pin inside a boron-water moderator with reflector, and ran MCNP tests on the base pellet. The design team modified the base pellet and tested it at different uranium-235 enrichments, with void spheres of varying volume and silicon carbide inclusions in the void volume. The simulation team selected K-code for testing the fuel pellets. The economics team analyzed the cost of manufacturing the improved pellet from cost of raw material through its tail assay in the form of Separative Work Unit (SWUs). The impacts team researched environmental, societal, governmental, political, and public affairs aspects of nuclear fuel production. Results Multiple configurations of uranium enrichment and silicon carbide volume inclusions in the nuclear fuel pellet achieved a k eff of 1, and the price per pellet, assuming fabrication costs comparable to existing manufacturing processes, was reduced by as much as about 50% when the volume of uranium oxide replaced by silicon carbide is 0.27 cm3. At smaller replacement volumes, the price per pellet is reduced by as little as 5%. Conclusions The goal of designing an optimized fuel pellet was met. Replacing a 0.27 cm3-volume sphere of uranium oxide with silicon carbide from the center of a pellet of 4%, 5%, or 6% uranium-235 enrichment reduced the cost of the pellet by approximately 50%.

A proposed refueling scheme for the modular pebble bed reactor

In this paper, a suggested design of the fuel pebble and loading pattern in the MIT Modular Pebble Bed HTGR (MPBR) using thorium (232Th) is presented. Using the MCNP5 code model for the MPBR reactor, different compositions of Thorium Low Enriched Uranium (ThLEU) with different Heavy Metal (HM) loading and 235U enrichment were investigated to achieve the maximum thorium utilization with relatively minimum reactivity insertion in case of water ingress accident. Using pure Low Enriched Uranium (LEU) pebbles and ThLEU pebbles with the same HM loading and 235U enrichment, different pebbles loading patterns were studied. One loading pattern was selected to achieve the criticality with enough excess reactivity compensating for the poisoning effect of xenon build-up at the startup of the reactor operation and the negative effect of fuel and reflector temperature coefficients of reactivity. This loading pattern aims also to reduce the radial power peaking in the core and to minimize the axial Power Peaking Factor (PPF) in the central hot channel, with a minimum number of pure LEU fuel batches. A calculation procedure was developed that combines fuel pebble depletion and full core calculations to investigate the impact of a proposed online refueling scheme for the MPBR reactor and to simulate the multicycle refueling mechanism. Using SERPENT 1.1.7, the nuclide concentrations were calculated as a function of pebble burnup for both LEU and ThLEU pebbles. A multicycle online refueling scheme was proposed and the average number of passes required for LEU and ThLEU pebbles to reach their maximum burnup was estimated.