Energy National Nuclear Security Administration Research Articles

A review of criticality dosimetry at the Y-12 National Security Complex and practical importance of dose accuracy in emergency response

A nuclear criticality results in the emission of both neutron and gamma radiation and can produce doses to personnel near the event that exceed 0.1 Gy (10 rad). The primary purpose of nuclear accident dosimetry is to rapidly identify affected personnel in need of prompt medical treatment and to reassure personnel who have been only minimally exposed. While accurate dosimetry is desired, it must be recognized that dose determinations made from whole-body dosimeters or simple triage methods are very rough estimates and contain significant uncertainties. Even when accounting for factors like varying neutron energy spectra, mean photon energies, body orientation within the radiation field, and transient effects on dosimeter response, etc., the end value is a dosimetric quantity defined for very specific radiological conditions and determined within a simple phantom usually at a single depth. Of more importance is the biological response to the radiation, which will vary by person and can be affected by the individual's radiation sensitivity, age, gender, mass, and underlying health conditions. The overall biological, person-specific response to a given dose cannot be precisely determined except by patient symptom observation and individual biological dosimetry (e.g. chromosome analysis, lymphocyte ratios, etc.). This work describes and discusses the criticality accident dosimetry program at the Y-12 National Security Complex, a United States Department of Energy National Nuclear Security Administration facility. The primary goals of the Y-12 accident dosimetry program are, among others, the rapid identification of significantly exposed persons, prompt routing of exposed workers for medical evaluation and treatment, and the ultimate processing of dosimeters to assign doses to personnel.

Estimation of Grouped Parameters Using Tanks-in-Series Lithium-Ion Battery Model

Parameter estimation is critical for efficient Battery Management System (BMS) performance. The accuracy and predictability of a model depends on the precision of its parameters. Moreover, model parameters tend to change with battery aging. Efficient BMS performance requires accurate tracking and updating of relevant parameters as the battery ages. Estimating parameters for electrochemical models is challenging due to the complexity of the governing equations, and the possibility of degeneracy, with multiple sets of parameter values that give the same accuracy for fitting charge/discharge data. Parameter estimation of various lithium-ion battery systems has been attempted with different model types, including equivalent circuit model2, single particle model3 and pseudo 2D (P2D) model.4,5 Estimation approaches reported in literature, such as, GA6, heuristic algorithms7, etc., are difficult to implement in real-time due to computational complexity. In the past, we proposed and implemented reformulated p2D models for real-time parameter estimation.8,9 While the reformulated models are computationally inexpensive, the large set of parameters and resulting likelihood of degeneracy introduce substantial complexity. Recently, we proposed lithium-ion Tanks-in-Series battery model10. This model is generated by systematic volume-averaging of the p2D model that enables efficient and real-time simulation with reduced set of parameters.In this presentation, we propose to estimate non-dimensional grouped parameters using non-dimensional Tanks-in-Series battery model. The grouping of parameters further reduces the number of parameters that needs to be estimated. This also reduces the computational effort required to perform optimization. The non-dimensional model captures resistances offered due to transport, reaction kinetics, and ohmic drop in electrolyte based on the non-dimensional grouped parameters that absorb constitutive expressions and parameters, such as electrolyte diffusivity, ionic conductivity, reaction rate constants and solid phase diffusivity. The estimation is performed on experimental charge/discharge data obtained from cylindrical cells having NCA and NMC cathode chemistries. The accuracy of the estimated parameters is validated using experimental cycling data obtained at different c-rates by calculating the error in voltage-time curves between the model prediction using estimated parameters and the experimental data. Acknowledgements The authors acknowledge funding from the U.S. Department of Energy Office of Electricity Energy Storage Program through Sandia National Laboratories, under the guidance of Dr. Imre Gyuk, and the Texas Materials Institute at The University of Texas at Austin. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy National Nuclear Security Administration under contract DE-NA-0003525. SAND2020-14131 A References V. Ramadesigan, P. W. C. Northrop, S. De, S. Santhanagopalan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 159, R31–R45 (2012).Y. Hu, S. Yurkovich, Y. Guezennec, and B. J. Yurkovich, Control Eng. Pract., 17, 1190–1201 (2009).A. P. Schmidt, M. Bitzer, Á. W. Imre, and L. Guzzella, IFAC Proc. Vol., 43, 198–203 (2010).J. C. Forman, S. J. Moura, J. L. Stein, and H. K. Fathy, in 5th Annual Dynamic Systems and Control Conference,, p. 1–8 (2012).S. Santhanagopalan, Q. Guo, and R. E. White, J. Electrochem. Soc., 154, 198–206 (2007).A. Jokar, B. Rajabloo, M. Désilets, and M. Lacroix, J. Electrochem. Soc., 163, A2876–A2886 (2016).J. Li, L. Zou, F. Tian, X. Dong, Z. Zou, and H. Yang, J. Electrochem. Soc., 163, A1646–A1652 (2016).V. Boovaragavan, S. Harinipriya, and V. R. Subramanian, J. Power Sources, 183, 361–365 (2008).V. Ramadesigan, K. Chen, N. A. Burns, V. Boovaragavan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 158, A1048–A1054 (2011).A. Subramaniam, S. Kolluri, C. D. Parke, M. Pathak, S. Santhanagopalan, and V. R. Subramanian, J. Electrochem. Soc., 167, 013534-013534–18 (2020).

CONCEPTUAL FUEL ELEMENT DESIGN CANDIDATES FOR CONVERSION OF HIGH FLUX ISOTOPE REACTOR WITH LOW-ENRICHED URANIUM SILICIDE DISPERSION FUEL*

Engineering design studies are underway to assess the feasibility of converting the High Flux Isotope Reactor (HFIR) to operate with low-enriched uranium silicide dispersion (LEU3Si2-Al) fuel. These studies are supported by the U.S. Department of Energy National Nuclear Security Administration’s Office of Material Management and Minimization. A systematic approach employing neutronic and thermal-hydraulic analyses has been performed with the ORNL Shift and HFIR Steady State Heat Transfer Code tools, respectively, to predict reactor performance and thermal safety margins for proposed LEU3Si2-Al fuel designs. The design process was initiated by generating an optimized design with fabrication features identified from previous studies that result in excellent performance and safety metrics. The approach continued by substituting a single fabrication feature anticipated to be difficult to manufacture with another feature expected to perform an analogous function to that of the removed feature. Four conceptual fuel element design candidates, with various fabrication features, for conversion of HFIR with 4.8 gU/cm3 LEU3Si2-Al fuel have been generated and shown to meet pre-defined performance and safety metrics. Results to date indicate that HFIR could convert with the subject fuel system and meet performance and safety requirements if, among other considerations, fabrication of the specific design features are demonstrated and qualification of the fuel is complete under HFIR-specific conditions.

Kilopower Project: The KRUSTY Fission Power Experiment and Potential Missions

The Kilopower Project was initiated by NASA’s Space Technology Mission Directorate/Game Changing Development Program in fiscal year 2015 to demonstrate subsystem-level technology readiness of small space fission power in a relevant environment (Technology Readiness Level 5) for space science and human exploration power needs. The Kilopower Project centerpiece is the Kilowatt Reactor Using Stirling TechnologY (KRUSTY) test, which consists of the development and testing of a ground technology demonstrator of a 1-kW(electric)–class fission power system (FPS). The technologies to be developed and validated by KRUSTY are extensible to space FPSs from 1 to 10 kW(electric), which can enable modular surface FPSs for human exploration as well as higher-power future potential deep space science missions. The KRUSTY demonstration is cofunded by NASA and the U.S. Department of Energy National Nuclear Security Administration. The KRUSTY demonstration in the National Critical Experiment Research Center’s Device Assembly Facility was completed in the first quarter of 2018.

Heat deposition analysis for the High Flux Isotope Reactor’s HEU and LEU core models

The High Flux Isotope Reactor at Oak Ridge National Laboratory is an 85MWth pressurized light-water-cooled and -moderated flux-trap type research reactor. The reactor is used to conduct numerous experiments, advancing various scientific and engineering disciplines. As part of an ongoing program sponsored by the US Department of Energy National Nuclear Security Administration Office of Material Management and Minimization, studies are being performed to assess the feasibility of converting the reactor’s highly enriched uranium fuel to low-enriched uranium fuel. To support this conversion project, reference models with representative experiment target loading and explicit fuel plate representation were developed and benchmarked for both fuels to (1) allow for consistent comparison between designs for both fuel types and (2) assess the potential impact of low-enriched uranium conversion. These high-fidelity models were used to conduct heat deposition analyses at the beginning and end of the reactor cycle and are presented herein.This paper (1) discusses the High Flux Isotope Reactor models developed to facilitate detailed heat deposition analyses of the reactor’s highly enriched and low-enriched uranium cores, (2) examines the computational approach for performing heat deposition analysis, which includes a discussion on the methodology for calculating the amount of energy released per fission, heating rates, power and volumetric heating rates, and (3) provides results calculated throughout various regions of the highly enriched and low-enriched uranium core at the beginning and end of the reactor cycle.These are the first detailed high-fidelity heat deposition analyses for the High Flux Isotope Reactor’s highly enriched and low-enriched core models with explicit fuel plate representation. These analyses are used to compare heat distributions obtained for both fuel designs at the beginning and end of the reactor cycle, and they are essential for enabling comprehensive thermal hydraulics and safety analyses that require detailed estimates of the heat source within all of the reactor’s fuel element regions.

MO-FG-CAMPUS-JeP1-01: Prompt Gamma Imaging with a Multi-Knife-Edge Slit Collimator: Evaluation for Use in Proton Beam Range Verification

Purpose: To evaluate and characterize a multi-slit collimated imaging system for use in prompt gamma range verification of proton therapy. Methods: Acrylic (PMMA) targets were irradiated with a 50 MeV proton beam. With the collimator placed 13 cm from the beam axis, photons of energy from 2–7 MeV were measured. Image reconstruction provided 2-dimensional distribution of gamma rays. Estimated Bragg peak location was compared with 1-dimensional profiles of photon images. Shifts in Bragg peak were simulated by physically moving the targets in 1 mm increments. Results: The imaging system measured prompt gamma emissions resulting from a 50 MeV proton beam, at currents up to 2 nA, incident on a PMMA target. Overall system detection efficiency was approximately 2.6×10−5 gamma/proton. With delivery of 1×1011 protons, shifts of 1 mm in the target location were detected in 2D prompt gamma images and 1D profiles. With delivery of 1×108 protons, shifts of approximately 3 mm were detectable. Conclusion: This work has characterized the performance of a prototype multi-slit collimated imaging system. The system can produce 2D images of prompt gamma distributions and detect shifts in Bragg peak location down to 1 mm. These results encourage further development and optimization of the system for clinical proton beam applications. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number: DEN979 through the Nuclear Science and Security Consortium.

Rotational band structure inMg32

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contracts No. DE-AC02-05CH11231 (LBNL) and No. DE-AC02-06CH11357 (ANL), by the Department of Energy National Nuclear Security Administration under Award No. DE-N979 and the National Science Foundation (NSF) under PHY-1102511. GRETINA was funded by the U.S. DOE Office of Science. Operation of the array at NSCL is supported by NSF under Cooperative Agreement PHY11-02511 (NSCL) and DOE under Grant No. DE-AC02- 05CH11231 (LBNL). A.P. is partly supported by MINECO (Spain) Grant FPA2014-57196 and Programme “Centros de Excelencia Severo Ochoa” SEV-2012-0249

Pressure-induced solidifications of liquid sulfur below and above λ-transition**Project supported by the Joint Funds of the National Natural Science Foundation of China (Grant No. U1530402), the National Natural Science Foundation of China (Grant No. 11004163), the Fundamental Research Funds for the Central Universities, China (Grant No. 2682014ZT31), the Department of Energy National Nuclear Security Administration (Grant No. DE-NA0001974), and the

Two kinds of glassy sulfurs are synthesized by the rapid compression method from liquid sulfur at temperatures below and above the λ -transition point. The glassy sulfur has different colors and transparencies, depending on temperature, which may inherit some structural information from the λ -transition. Raman spectrum studies of these samples show that a large fraction of polymeric chains exist in the glassy sulfur, even in the one solidified from T < Tλ. We find that a higher compression rate instead of a higher temperature of the parent liquid captures more polymeric chains. Pressure-induced glassy sulfur presents high thermal stability compared with temperature quenched glassy sulfur and could transform into liquid sulfur directly without crystallization through an abnormal exothermic melting course. High energy x-ray diffraction is utilized to study the local order of the pressure-induced glassy sulfur.

WE‐EF‐303‐03: A New Aperture‐Based Imaging System for Prompt‐Gamma Range Verification of Proton Beam Therapy

Purpose:To develop and characterize a novel aperture‐based imaging system for high‐energy gamma‐rays. This collimated system will provide 2‐dimensional imaging capability for verification of proton beam range and Bragg peak dose via prompt‐gamma detection.Methods:A multi‐knife‐edge slit collimator has been designed, constructed, and characterized via simulations and experimental measurements. The 20×20×7.5 cm3 tungsten collimator and accompanying LSO scintillation detector were simulated using the TOPAS Geant4 ‐based Monte Carlo package. Iterative reconstruction methods were combined with point response functions to characterize the imaging performance of the system. The response of the system has begun to be characterized experimentally as well, using 2.6 MeV gamma‐rays from Th‐228.Results:Both simulation and experimental results indicate that this collimated system provides 2‐D imaging capability in the energy range of interest for prompt‐gamma dose verification. In the current configuration, with collimator to source distance of 13 cm, image reconstruction of point sources resulted in spatial resolution (FWHM) of approximately 4 mm in both x‐and y‐directions in the imaging plane. The accuracy of positioning the point sources is less than 1 mm.Conclusion:This work has characterized, via simulation and measurements, a novel multi‐knife‐edge slit collimator in front of a more conventional position‐sensitive LSO scintillator detector. The multi‐slit pattern is designed to increase detection efficiency and provide spatial information in 2‐dimensions ‐‐ an improvement over a single‐slit collimator design. The thickness and density of the collimator will allow this detection system to perform well in an environment with high gamma flux, while ultimately providing peak determination accuracy on the order of 1 mm.This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number: DE‐NA0000979 through the Nuclear Science and Security Consortium.

Distribution of radionuclides in surface seawater obtained by an aerial radiological survey

We investigated the distribution in seawater of anthropogenic radionuclides from the Fukushima Daiichi Nuclear Power Plant (FNPP1) as preliminary attempt using a rapid aerial radiological survey performed by the U.S. Department of Energy National Nuclear Security Administration on 18 April 2011. We found strong correlations between in-situ activities of 131I, 134Cs, and 137Cs measured in surface seawater samples and gamma-ray peak count rates determined by the aerial survey (correlation coefficients were 0.89 for 131I, 0.96 for134Cs, and 0.92 for137Cs). The offshore area of high radionuclide activity extended south and southeast from the FNPP1. The maximum activities of 131I, 134Cs, and 137Cs were 329, 650, and 599 Bq L−1, respectively. The 131I/137Cs ratio in surface water of the high-activity area ranged from 0.6 to 0.7. Considering the radioactive decay of 131I (half-life 8.02 d), we determined that the radionuclides in this area were directly released from FNPP1 to the ocean. We confirm that aerial radiological surveys can be effective for investigating the surface distribution of anthropogenic radionuclides in seawater. Our model reproduced the distribution pattern of radionuclides derived from the FNPP1, although results simulated by a regional ocean model were underestimated.

Enhanced Analysis Methods to Derive the Spatial Distribution of 131I Deposition on the Ground by Airborne Surveys at an Early Stage after the Fukushima Daiichi Nuclear Power Plant Accident

This paper applies both new and well tested analysis methods to aerial radiological surveys to extract the I ground concentrations present after the March 2011 Fukushima Daiichi nuclear power plant (NPP) accident. The analysis provides a complete map of I deposition, an important quantity incalculable at the time of the accident due to the short half-life of I and the complexity of the analysis. A map of I deposition is the first step in conducting internal exposure assessments, population dose reconstruction, and follow-up epidemiological studies. The short half-life of I necessitates the use of aerial radiological surveys to cover the large area quickly, thoroughly, and safely. Teams from the U.S. Department of Energy National Nuclear Security Administration (DOE/NNSA) performed aerial radiological surveys to provide initial maps of the dispersal of radioactive material in Japan. This work reports on analyses performed on a subset of the initial survey data by a joint Japan-U.S. collaboration to determine I ground concentrations. The analytical results show a high concentration of I northwest of the NPP, consistent with the previously reported radioactive cesium deposition, but also shows a significant I concentration south of the plant, which was not observed in the original cesium analysis. The difference in the radioactive iodine and cesium patterns is possibly the result of differences in the ways these materials settle out of the air.

EFRMAC Overview: Data Management and Enabling Technologies for Characterization of a Radiological Release.

The eFRMAC enterprise is a suite of technologies and software developed by the U.S. Department of Energy National Nuclear Security Administration's Office of Emergency Response to coordinate the rapid data collection, management, and analysis required during a radiological emergency. This enables the Federal Radiological Monitoring and Assessment Center assets to evaluate a radiological or nuclear incident efficiently to facilitate actions to protect public health and the environment. This document identifies and describes eFRMAC methods including: (1) data acquisition, (2) data management, (3) data analysis, (4) product creation, (5) quality control, and 6) product dissemination.

Adapting the U.S. Domestic Radiological Emergency Response Process to an Overseas Incident

The earthquake and resulting tsunami in Japan led to a radiological release from the Fukushima Daiichi Nuclear Power Plan, which in turn resulted in the rapid activation and deployment by the U.S. Department of Energy National Nuclear Security Administration (DOE/NNSA) emergency response teams. These teams and those from other federal agencies are typically coordinated through the Federal Radiological Monitoring and Assessment Center (FRMAC) when responding to radiological incidents in the U.S. FRMAC is the body through which the collection, analysis, and assessment of environmental radiological data are coordinated and products released to decision makers. This article discusses DOE/NNSA’s role in the U.S. response to the Fukushima accident as it implemented its components of FRMAC in a foreign country, coordinated its assets, integrated with its federal partners, and collaborated with the Government of Japan. The technical details of the various data collections and analyses are covered in other articles of this issue.

Introduction to the Special Issue on the U.S. Response to the Fukushima Accident

Provides an introduction to the May 2012 issue of Health Physics, based on a special session at the 2011 Health Physics Society (HPS) annual meeting that focused on the United States' radiological response to the Fukushima Daiichi Nuclear Power Plant accident. This introduction outlines the papers in this important issue and describes the activities of the U.S. response participants, including the U.S. Department of Energy National Nuclear Security Administration (DOE/NNSA), Department of Defense, the U.S. Nuclear Regulatory Commission (NRC) and other organizations. Observations are provided and the stage is set for the articles in this issue which document many of the activities undertaken during the Fukushima accident and which describe challenges faced and valuable lessons learned.