Search NASA⌕ Search

SEARCH · Search NASA

Results for “Nuclear Data Evaluation Methods”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Report on the Integration of Experimental and Modeling Data for Initial Equivalence Study of Microstructural Evolution in Irradiated LPBF 316SS

Advanced materials and manufacturing technologies are poised to improve the safety and design characteristics of nuclear technologies and meet US energy, environmental, and economic needs. In particular, metal additive manufacturing (AM) provides an opportunity to produce novel materials and component geometries, but their use is not without hurdles arising from the inherent microstructure variability that can result from the layer-by-layer build approach. Given the greater possible microstructure variability in AM materials—and the dearth of materials test reactors—it is impractical to rely solely on neutron irradiation studies to produce data for materials qualification for every possibility. This work within the Advanced Materials and Manufacturing Technologies (AMMT) Environmental Effects technical area contributes to the rapid qualification framework by developing a science-driven framework for the accelerated qualification of materials for nuclear environments. A key product of the Environmental Effects technical area of the AMMT program is the Licensing Approach with Ions and Neutrons (LAIN). This approach recognizes that whether using existing materials in new environments, newly developed materials tailored for these environments, or new manufacturing methods, the traditional decades-long approach for materials qualification does not facilitate rapid deployment. In FY 2023, the AMMT program presented a conceptual framework of specific steps to fulfill several technical challenges associated with qualifying materials for performance in radiation environments on an accelerated time frame informed by the state of the art in materials science and a review of the current regulatory landscape. The objective of this section of the Environmental Effects technical area is to critically evaluate and refine the proposed qualification framework presented under AMMT by integrating the research results of the neutron irradiations, the ion irradiations, and modeling efforts. These ongoing efforts span across Argonne National Laboratory (ANL), Idaho National Laboratory (INL), and Oak Ridge National Laboratory (ORNL) and are closely coordinated.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Initial Application of TSUNAMI for Validation of Advanced Fuel Systems

A number of advanced reactor concepts and accident-tolerant fuels (ATFs) are under development or in the initial stages of deployment and testing in the nuclear power industry. Many of these concepts incorporate chemical or material forms that have not traditionally been used in the nuclear industry and may present challenges for nuclear criticality safety validation. Sensitivity/uncertainty methods are ideally suited for assessing the applicability of existing critical experiments to these potentially challenging applications. This paper presents two case studies recently completed at Oak Ridge National Laboratory (ORNL) which investigated the use of the TSUNAMI tools within the SCALE code system to perform such assessments.Many advanced reactor concepts include uranium enrichments above 5 wt% 235U but below the 20 wt% limit of low-enriched uranium (LEU). This material, referred to as high assay LEU (HA-LEU), poses difficulties across the entire infrastructure of nuclear power, including enrichment, transportation, fabrication, and storage. A potentially representative transportation package was selected to perform a criticality safety validation assessment for UF6 containing HA-LEU. Sensitivity data were generated using the TSUNAMI-3D sequence, and an assessment of the applicability of a range of critical experiments was performed using the TSUNAMI-IP tool. The critical experiments were drawn from the set of available sensitivity data files distributed with the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook. The results indicate that a sufficient number of available experiments may be available to perform validations for these systems.Many different cladding materials and fuel dopants are included in ATFs to mitigate the consequences of a loss of coolant accident. Some of these systems have already been fabricated and introduced as lead test assemblies in commercial reactors, while others are still being developed. Several concepts were considered for pressurized-water reactors (PWRs) and boiling-water reactors (BWRs) in comparison to the current Zircaloy and UO2 fuel system. In most of these cases, the ATF materials did not significantly impact the number of applicable experiments for validation. Some fuel and cladding materials were identified, however, which may reduce the number of available experiments and which will increase the nuclear data–induced uncertainty in neutron multiplication.

Marshall, William (B.J.)↗
DOE OSTI2013

Monte Carlo investigation of I-125 interseed attenuation for standard and thinner seeds in prostate brachytherapy with phantom validation using a MOSFET

Purpose: In permanent seed implant prostate brachytherapy the actual dose delivered to the patient may be less than that calculated by TG-43U1 due to interseed attenuation (ISA) and differences between prostate tissue composition and water. In this study the magnitude of the ISA effect is assessed in a phantom and in clinical prostate postimplant cases. Results are compared for seed models 6711 and 9011 with 0.8 and 0.5 mm diameters, respectively. Methods: A polymethyl methacrylate (PMMA) phantom was designed to perform ISA measurements in a simple eight-seed arrangement and at the center of an implant of 36 seeds. Monte Carlo (MC) simulation and experimental measurements using a MOSFET dosimeter were used to measure dose rate and the ISA effect. MC simulations of 15 CT-based postimplant prostate treatment plans were performed to compare the clinical impact of ISA on dose to prostate, urethra, rectum, and the volume enclosed by the 100% isodose, for 6711 and 9011 seed models. Results: In the phantom, ISA reduced the dose rate at the MOSFET position by 8.6%-18.3% (6711) and 7.8%-16.7% (9011) depending on the measurement configuration. MOSFET measured dose rates agreed with MC simulation predictions within the MOSFET measurement uncertainty, which ranged from 5.5% to 7.2% depending on the measurement configuration (k= 1, for the mean of four measurements). For 15 clinical implants, the mean ISA effect for 6711 was to reduce prostate D90 by 4.2 Gy (3%), prostate V100 by 0.5 cc (1.4%), urethra D10 by 11.3 Gy (4.4%), rectal D2cc by 5.5 Gy (4.6%), and the 100% isodose volume by 2.3 cc. For the 9011 seed the mean ISA effect reduced prostate D90 by 2.2 Gy (1.6%), prostate V100 by 0.3 cc (0.7%), urethra D10 by 8.0 Gy (3.2%), rectal D2cc by 3.1 Gy (2.7%), and the 100% isodose volume by 1.2 cc. Differences between the MC simulation and TG-43U1 consensus data for the 6711 seed model had a similar impact, reducing mean prostate D90 by 6 Gy (4.2%) and V100 by 0.6 cc (1.8%). Conclusions: ISA causes the delivered dose in prostate seed implant brachytherapy to be lower than the dose calculated by TG-43U1. MC simulation of phantom seed arrangements show that dose at a point can be reduced by up to 18% and this has been validated using a MOSFET dosimeter. Clinical simulations show that ISA reduces DVH parameter values, but the reduction is less for thinner seeds.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

The Effect of Kr-85 Decay to Rb-85 on Waste Forms - 17105

Krypton-85 (Kr-85) is a volatile radionuclide released during the reprocessing of used nuclear fuel (UNF). Prior to discharge of process off-gas streams to the environment, removal of Kr-85 is required to meet emission regulations. Once removed from the off-gas streams, Kr (containing stable Kr in addition to Kr-85) must be placed in storage until the Kr-85 has decayed to levels such that its potential release would meet regulatory guidelines. The current method of storage is high-pressure metal canisters. Historically, concerns have been expressed that the decay product of Kr-85, Rubidium-85 (Rb-85), could cause corrosion and weakening in the canisters that would ultimately lead to premature failure and release of Kr-85. Alternate methods and materials, such as matrix isolation in a vapor deposited metal and immobilization in zeolites, have been investigated as storage approaches for Kr. However, even these storage methods may become compromised due to the chemical effects of Rb-85 arising from the decay of Kr-85. A review was conducted of the available literature to examine topics relevant to the effects of Rb on the long-term storage of Kr-85, examine the source terms in the context of this concern, and suggest a path forward to resolve outstanding knowledge gaps. In the course of this analysis, several knowledge gaps were identified. Examples include: o The use of solid sorbents to potentially permit more Kr-85-bearing gas to be loaded into canisters, either at the pressures used in the current method or at significantly lower pressures. o A cost-to-benefit analysis is needed to ascertain the practicality of manufacturing waste forms for Kr-85 storage with solid sorbents. o The effects of radiation and chemical transmutation in solid sorbents or matrices for this application are virtually unknown. o Fundamental data are needed on corrosion rates and mechanisms as functions of Rb concentration, storage temperature, etc., for various storage approaches (e.g., as compressed gas or encapsulated in a getter material) and storage container materials. The present analysis focused on the available information regarding storage of Kr-85 in high-pressure containers. It was judged unlikely that such containers would be compromised by corrosion from the Rb decay product, especially if the Kr recovery operations result in a gas composition with very low oxygen content. However, this conclusion should be revisited based on preliminary data gathered from analysis of legacy Kr waste forms. These legacy waste forms are a result of experiments conducted at Idaho National Laboratory over 30 y ago and have been stored for more than three Kr-85 half-lives. Evaluation of these forms indicates significant corrosion, the cause of which has not been conclusively determined. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Development of Novel Sorbents for Uranium Extraction from Seawater

As the uranium resource in terrestrial ores is limited, it is difficult to ensure a long-term sustainable nuclear energy technology. The oceans contain approximately 4.5 billion tons of uranium, which is one thousand times the amount of uranium in terrestrial ores. Development of technologies to recover the uranium from seawater would greatly improve the uranium resource availability, sustaining the fuel supply for nuclear energy. Several methods have been previously evaluated including solvent extraction, ion exchange, flotation, biomass collection, and adsorption; however, none have been found to be suitable for reasons such as cost effectiveness, long term stability, and selectivity. Recent research has focused on the amidoxime functional group as a promising candidate for uranium sorption. Polymer beads and fibers have been functionalized with amidoxime functional groups, and uranium adsorption capacities as high as 1.5 g U/kg adsorbent have recently been reported with these types of materials. As uranium concentration in seawater is only ~3 ppb, great improvements to uranium collection systems must be made in order to make uranium extraction from seawater economically feasible. This proposed research intends to develop transformative technologies for economic uranium extraction from seawater. The Lin group will design advanced porous supports by taking advantage of recent breakthroughs in nanoscience and nanotechnology and incorporate high densities of well-designed chelators into such nanoporous supports to allow selective and efficient binding of uranyl ions from seawater. Several classes of nanoporous materials, including mesoporous silica nanoparticles (MSNs), mesoporous carbon nanoparticles (MCNs), meta-organic frameworks (MOFs), and covalent-organic frameworks (COFs), will be synthesized. Selective uranium-binding liagnds such as amidoxime will be incorporated into the nanoporous materials to afford a new generation of sorbent materials that will be evaluated for their uranium extraction efficiency. The initial testing of these materials for uranium binding will be carried out in the Lin group, but more detailed sorption studies will be carried out by Dr. Taylor-Pashow of Savannah River National Laboratory in order to obtain quantitative uranyl sorption selectivity and kinetics data for the proposed materials. The proposed nanostructured sorbent materials are expected to have higher binding capacities, enhanced extraction kinetics, optimal stripping efficiency for uranyl ions, and enhanced mechanical and chemical stabilities. This transformative research will significantly impact uranium extraction from seawater as well as benefit DOE’s efforts on environmental remediation by developing new materials and providing knowledge for enriching and sequestering ultralow concentrations of other metals.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

Comparing deflection measurements of a magnetically steerable catheter using optical imaging and MRI

Purpose: Magnetic resonance imaging (MRI) is an emerging modality for interventional radiology, giving clinicians another tool for minimally invasive image-guided interventional procedures. Difficulties associated with endovascular catheter navigation using MRI guidance led to the development of a magnetically steerable catheter. The focus of this study was to mechanically characterize deflections of two different prototypes of the magnetically steerable catheterin vitro to better understand their efficacy. Methods: A mathematical model for deflection of the magnetically steerable catheter is formulated based on the principle that at equilibrium the mechanical and magnetic torques are equal to each other. Furthermore, two different image based methods for empirically measuring the catheter deflection angle are presented. The first, referred to as the absolute tip method, measures the angle of the line that is tangential to the catheter tip. The second, referred to the base to tip method, is an approximation that is used when it is not possible to measure the angle of the tangent line. Optical images of the catheter deflection are analyzed using the absolute tip method to quantitatively validate the predicted deflections from the mathematical model. Optical images of the catheter deflection are also analyzed using the base to tip method to quantitatively determine the differences between the absolute tip and base to tip methods. Finally, the optical images are compared to MR images using the base to tip method to determine the accuracy of measuring the catheter deflection using MR. Results: The optical catheter deflection angles measured for both catheter prototypes using the absolute tip method fit very well to the mathematical model (R{sup 2} = 0.91 and 0.86 for each prototype, respectively). It was found that the angles measured using the base to tip method were consistently smaller than those measured using the absolute tip method. The deflection angles measured using optical data did not demonstrate a significant difference from the angles measured using MR image data when compared using the base to tip method. Conclusions: This study validates the theoretical description of the magnetically steerable catheter, while also giving insight into different methods and modalities for measuring the deflection angles of the prototype catheters. These results can be used to mechanically model future iterations of the design. Quantifying the difference between the different methods for measuring catheter deflection will be important when making deflection measurements in future studies. Finally, MR images can be used to reliably measure deflection angles since there is no significant difference between the MR and optical measurements.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Poster — Thur Eve — 06: Dose assessment of cone beam CT imaging protocols as part of SPECT/CT examinations

Purpose: To assess radiation dose from the cone beam CT (CBCT) component of SPECT/CT studies and to compare with other CT examinations performed in our institution. Methods: We used an anthropomorphic chest phantom and the 6 cc ion chamber to measure entrance breast dose for several CBCT and diagnostic CT acquisition protocols. The CBCT effective dose was calculated with ImPACT software; the CT effective dose was evaluated from the DLP value and conversion factor, dependent on the anatomic region. The RADAR medical procedure radiation dose calculator was used to assess the nuclear medicine component of exam dose. Results: The entrance dose to the breast measured with the anthropomorphic phantom was 0.48 mGy and 9.41 mGy for cardiac and chest CBCT scans; and 4.59 mGy for diagnostic thoracic CT. The effective doses were 0.2 mSv, 3.2 mSv and 2.8 mSv respectively. For a small patient represented by the anthropomorphic phantom, the dose from the diagnostic CT was lower than from the CBCT scan, as a result of the exposure reduction options available on modern CT scanners. The CBCT protocols used the same fixed scanning techniques. The diagnostic CT dose based on the patient data was 35% higher than the phantom dose. For most SPECT/CT studies the dose from the CBCT component was comparable with the dose from the radiopharmaceutical. Conclusions: The patient radiation dose from the cone beam CT scan can be higher than that from a diagnostic CT and should be taken into consideration in evaluating total SPECT/CT patient dose.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

The Need for Precise and Well-documented Experimental Data on Prompt Fission Neutron Spectra from Neutron-induced Fission of {sup 239}Pu

The spectrum of neutrons emitted promptly after {sup 239}Pu(n,f)—a so-called prompt fission neutron spectrum (PFNS)—is a quantity of high interest, for instance, for reactor physics and global security. However, there are only few experimental data sets available that are suitable for evaluations. In addition, some of those data sets differ by more than their 1-σ uncertainty boundaries. We present the results of MCNP studies indicating that these differences are partly caused by underestimated multiple scattering contributions, over-corrected background, and inconsistent deconvolution methods. A detailed uncertainty quantification for suitable experimental data was undertaken including these effects, and test-evaluations were performed with the improved uncertainty information. The test-evaluations illustrate that the inadequately estimated effects and detailed uncertainty quantification have an impact on the evaluated PFNS and associated uncertainties as well as the neutron multiplicity of selected critical assemblies. A summary of data and documentation needs to improve the quality of the experimental database is provided based on the results of simulations and test-evaluations. Given the possibly substantial distortion of the PFNS by multiple scattering and background effects, special care should be taken to reduce these effects in future measurements, e.g., by measuring the {sup 239}Pu PFNS as a ratio to either the {sup 235}U or {sup 252}Cf PFNS.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Development of Real-Time Quantitative Safety Evaluation Method for Nuclear Power Plants

Human operators involved with large process control systems such as nuclear power plants (NPPs) perform significant roles in the operation of systems. In this reason, deficiencies in human factors such as poor HSI (Human System Interface) design, procedure, and training, are significant contributing factors to NPPs incidents and accidents. In this regard, many kinds of studies including human reliability analysis (HRA), operation support system, automation, have been conducted in order to reduce human errors. Among these fields of studies, automation has its own specialty since it mainly focuses on eliminating the human error-inducing tasks to reduce human error, while other topics are primarily focusing on reducing human error by aiding human operators during operation. It is commonly believed that replacing human operators to the automated system would guarantee greater efficiency, lower workloads, and fewer human errors. However, these beliefs are not always true in large and complex systems such as NPP, since excessive automation can generate new roles for human operators, change human operators' activities in unexpected ways, and inducing 'out-of-the-loop' (OOTL) problem. Especially, although human error probability drastically increases during abnormal situations in NPP due to overload of information, high workload, and short time available for diagnosis, automation is not actively adopted since conventional machine learning techniques are neither capable nor reliable to handle overwhelmingly complex abnormal situations in NPP. Recently, newly developed 'deep learning' techniques have been actively applied to many fields, and some of these studies proved that the artificial intelligences (AI) based on deep learning techniques show better performance than that of human being. In 2015, deep Q-network (DQN) which is one of the deep learning techniques was developed and applied to train AI that automatically plays various Atari 2800 games, and this AI surpassed the human-level playing in many kind of games. Also in 2016, 'AlphaGo', which was developed by 'Google Deepmind' based on deep learning technique to play the game of Go, was defeated Se-dol Lee who is the World Go champion with score of 4:1. In the point of view that the game of Go is considered as one of the challenging area in machine learning field, it is verified that these new machine learning techniques can perform well, even better than the human being in high-complexity tasks. Previously, most of AI applications in nuclear field were focusing on supporting human operators' tasks such as diagnosis and decision making by rapid classification and prediction, based on fixed training data sets. However, it is expected that AI can be applied to solve more complicated problems (i.e. automation during abnormal states in NPP) by adopting advanced machine learning methodologies. In order to apply the automation system in NPP, firstly it is needed to evaluate the status of the plant quantitatively in real-time, since the information about which state is better (i.e. safe) or worse (i.e. unsafe) is essential for training properly working automation AI. Currently, there are several methodologies for NPP safety evaluation such as probabilistic safety assessment (PSA), safety performance indicator (SPI). However, existing methodologies are not feasible for development of automated system since they are not capable for the cases which are not included in the underlying model, not able to consider delicate changes in the NPP, and hard to evaluate in real-time. Therefore, development of new NPP safety evaluation methodology which can cover previously mentioned requirements is needed to conduct the study on NPP automation further. In this study, the concept of early warning score (EWS) in medical field was adopted to develop the methodology which can evaluate the safety level of the NPP quantitatively and in real-time. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2015

Rod internal pressure quantification and distribution analysis using Frapcon

This report documents work performed supporting the Department of Energy (DOE) Office of Nuclear Energy (NE) Fuel Cycle Technologies Used Fuel Disposition Campaign (UFDC) under work breakdown structure element 1.02.08.10, ST Analysis. In particular, this report fulfills the M4 milestone M4FT- 15OR0810036, Quantify effects of power uncertainty on fuel assembly characteristics, within work package FT-15OR081003 ST Analysis-ORNL. This research was also supported by the Consortium for Advanced Simulation of Light Water Reactors (http://www.casl.gov), an Energy Innovation Hub (http://www.energy.gov/hubs) for Modeling and Simulation of Nuclear Reactors under U.S. Department of Energy Contract No. DE-AC05-00OR22725. The discharge rod internal pressure (RIP) and cladding hoop stress (CHS) distributions are quantified for Watts Bar Nuclear Unit 1 (WBN1) fuel rods by modeling core cycle design data, operation data (including modeling significant trips and downpowers), and as-built fuel enrichments and densities of each fuel rod in FRAPCON-3.5. A methodology is developed which tracks inter-cycle assembly movements and assembly batch fabrication information to build individual FRAPCON inputs for each evaluated WBN1 fuel rod. An alternate model for the amount of helium released from the zirconium diboride (ZrB2) integral fuel burnable absorber (IFBA) layer is derived and applied to FRAPCON output data to quantify the RIP and CHS for these types of fuel rods. SCALE/Polaris is used to quantify fuel rodspecific spectral quantities and the amount of gaseous fission products produced in the fuel for use in FRAPCON inputs. Fuel rods with ZrB2 IFBA layers (i.e., IFBA rods) are determined to have RIP predictions that are elevated when compared to fuel rod without IFBA layers (i.e., standard rods) despite the fact that IFBA rods often have reduced fill pressures and annular fuel pellets. The primary contributor to elevated RIP predictions at burnups less than and greater than 30 GWd/MTU is determined to be the total fuel rod void volume and the amount of released fission gas in the fuel rod, respectively. Cumulative distribution functions (CDFs) are prepared from the distribution of RIP and CHS predictions for all standard and IFBA rods. The provided CDFs allow for the determination of the portion of WBN1 fuel rods that exceed a specified RIP or CHS limit. Results are separated into IFBA and standard rods so that the two groups may be analyzed individually. FRAPCON results are provided in sufficient detail to enable the recalculation of the RIP while considering any desired plenum gas temperature, total void volume, or total amount of gas present in the void volume. A method to predict the CHS from a determined or assumed RIP is also proposed, which is based on the approximately linear relationship between the CHS and the RIP. Finally, improvements to the computational methodology of FRAPCON are proposed.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2024

Metrics and Methods for Radiation Detection Algorithm Characterization for Nuclear/Radiological Source Search

This report presents a series of recommendations for data to train and evaluate radiation detection algorithms and performance metrics to evaluate these algorithms. These recommendations were formed through a community consensus approach through the Detection Radiation Algorithms Group (DRAG), a multi-institution collaboration spanning eight Department of Energy laboratories and John Hopkins Applied Physics Laboratory. This report includes recommendations on background data variability, and metrics to quantify variability, sources and shielding configurations to include in data collection campaigns and detector response variability. In addition, this report describes several anomaly detection and identification algorithms and recommends metrics to report their performance. Finally, this report ends with a discussion on machine learning algorithms.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

DETECTING FIRE WITH MACHINE LEARNING-ENABLED VISUAL MONITORING FOR NUCLEAR POWER PLANT ENVIRONMENTS

Nuclear power plants are experiencing significant cost challenges to remain competitive with other energy-generation utilities. Unlike other industries, the cost of operation and maintenance activities is mostly attributed to workforce costs. To mitigate this, nuclear power plant stakeholders are increasingly interested in the development and deployment of machine learning methods to potentially automate or augment manually intensive tasks to reduce costs, especially for monitoring activities. One monitoring function that is visually demanding and that can occur frequently to meet the requirements of a fire protection program is visually monitoring an area for fire occurrence. Currently, fire watch activities consist of a worker physically stationed at a given location with the sole responsibility of observing a given area to ensure a fire is detected and mitigated promptly. This effort focused on the development and evaluation of a suitable deep convolutional neural network to classify individual video frames at a sub-second frequency for the occurrence of “fire” and “no fire” in varying industrial environments similar to nuclear power plants. It is believed that a trained neural network model could be integrated with existing facility video surveillance camera feeds to generate alerts when fire inferences occur in individual frames captured at sub-second temporal resolutions. Extensive effort was dedicated to identifying and curating suitable imagery training data representing varying environments and scene settings with and without flame features to maximize generalization in nuclear power plant environments. The data collection effort resulted in the aggregation of a large, labeled image library exceeding 12,000 images to support model training for diverse industrial environments. A deep neural network model incorporating parallel multi-scale capabilities was developed and trained to support accurate image-based detection of flame incidents of varying sizes and spectral feature properties within heterogeneous scenes. Analysis results show that the trained model can achieve high inference accuracy despite heterogeneous scene environments and components. Testing accuracy exceeded 95.0 percent with very low false positive and false negative inferences.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRSDate not supplied

Application of Analytical Hierarchy Process for Narrowing Down Nep Candidate Reactor Designs

Nuclear electric propulsion (NEP)-powered vehicles have been contemplated for human Mars missions. The nuclear power system contemplates using a high temperature light-weight nuclear reactor for the production of electrical power in the range of 2-5 MWe with a 3-10 year service life. A myriad of technology options exist for achieving these mission objectives. The analytic hierarchy process (AHP), a multi-attribute decision method, is being used to narrow down the candidate designs. The AHP is a structured decision process that fuses model-supplied quantitative data with subjective assessments to facilitate decisions that involve multiple competing criteria. Proven end-to-end nuclear design and systems analysis tools will be used to provide quantitative performance data such as end-to-end system reliability, system robustness to recover from off-normal conditions, system specific weight (α in kg/kWe), and the ability to meet the service life-time and power level requirements. Three high assay low enriched uranium (HALEU) reactor concepts, namely, gas-, heat pipe- and pumped liquid-cooled nuclear cores coupled to a He/Xe gas or supercritical CO2- Brayton power conversion system are being modeled using the AHP to understand the trade-offs associated with these design combinations. In addition to the reactor and power conversion options, there are a myriad of additional components and subsystems – e.g., radiators, heat exchangers, and recuperators – that also figure into the evaluation process. The choice of the right overall system is a multidimensional problem that has to include not only quantitative data, but also the so called “external factors”, examples of which include the component and subsystem Technology Readiness Levels (TRLs), the associated Advancement Degrees of Difficulty (AD2), the cost and schedule required to achieve a technical maturity consistent with mission infusion, alignment with the priorities of NASA’s Space Nuclear Propulsion program, and alignment with other ongoing government and commercial investments in micro reactors. Focused expert elicitations form the basis for qualitative data set. As a final step, decision-makers individually express their opinions regarding the relative importance of the criteria and preferences among the alternatives through pairwise comparisons. The paper will describe the AHP approach, progress to-date applying it to the NEP human Mars mission problem, and preliminary results. Use of AHP provides sufficient flexibility for incorporating industry input at different stages as the technologies evolve through additional research and development. It is expected that the decision process will be ongoing and expanded to examine additional options and technology choices, culminating in a defensible set of candidate reactor concepts that will form the basis for developing a multi-year NEP technology maturation strategy. .

Dasari V Rao↗
DOE OSTI2017

A Point Kinetics Model for Estimating Neutron Multiplication of Bare Uranium Metal in Tagged Neutron Measurements

An extension of the point kinetics model is developed in this paper to describe the neutron multiplicity response of a bare uranium object under interrogation by an associated particle imaging deuterium-tritium (D-T) measurement system. This extended model is used to estimate the total neutron multiplication of the uranium. Both MCNPX-PoliMi simulations and data from active interrogation measurements of highly enriched and depleted uranium geometries are used to evaluate the potential of this method and to identify the sources of systematic error. The detection efficiency correction for measured coincidence response is identified as a large source of systematic error. If the detection process is not considered, results suggest that the method can estimate total multiplication to within 13% of the simulated value. Values for multiplicity constants in the point kinetics equations are sensitive to enrichment due to (n, xn) interactions by D-T neutrons and can introduce another significant source of systematic bias. This can theoretically be corrected if isotopic composition is known a priori. Finally, the spatial dependence of multiplication is also suspected of introducing further systematic bias for high multiplication uranium objects.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Grating-based x-ray differential phase contrast imaging with twin peaks in phase-stepping curves—phase retrieval and dewrapping

Purpose: X-ray differential phase contrast CT implemented with Talbot interferometry employs phase-stepping to extract information of x-ray attenuation, phase shift, and small-angle scattering. Since inaccuracy may exist in the absorption grating G{sub 2} due to an imperfect fabrication, the effective period of G{sub 2} can be as large as twice the nominal period, leading to a phenomenon of twin peaks that differ remarkably in their heights. In this work, the authors investigate how to retrieve and dewrap the phase signal from the phase-stepping curve (PSC) with the feature of twin peaks for x-ray phase contrast imaging. Methods: Based on the paraxial Fresnel–Kirchhoff theory, the analytical formulae to characterize the phenomenon of twin peaks in the PSC are derived. Then an approach to dewrap the retrieved phase signal by jointly using the phases of the first- and second-order Fourier components is proposed. Through an experimental investigation using a prototype x-ray phase contrast imaging system implemented with Talbot interferometry, the authors evaluate and verify the derived analytic formulae and the proposed approach for phase retrieval and dewrapping. Results: According to theoretical analysis, the twin-peak phenomenon in PSC is a consequence of combined effects, including the inaccuracy in absorption grating G{sub 2}, mismatch between phase grating and x-ray source spectrum, and finite size of x-ray tube’s focal spot. The proposed approach is experimentally evaluated by scanning a phantom consisting of organic materials and a lab mouse. The preliminary data show that compared to scanning G{sub 2} over only one single nominal period and correcting the measured phase signal with an intuitive phase dewrapping method that is being used in the field, stepping G{sub 2} over twice its nominal period and dewrapping the measured phase signal with the proposed approach can significantly improve the quality of x-ray differential phase contrast imaging in both radiograph and CT. Conclusions: Using the phase retrieval and dewrapping methods proposed to deal with the phenomenon of twin peaks in PSCs and phase wrapping, the performance of grating-based x-ray differential phase contrast radiography and CT can be significantly improved.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Challenges of Using Indistinguishable from Background as a Release Criterion at FUSRAP Projects - 18157

The US Army Corps of Engineers (USACE) utilizes the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) approach to site release on Formerly Utilized Sites Remedial Action Program (FUSRAP) projects. Use of Indistinguishable from Background (IFB) as a release criterion is discussed in MARSSIM as Scenario B; however, the discussion is arguably limited and refers the user to other documents. USACE has utilized the IFB approach at select FUSRAP projects. USACE experience is that use of IFB as a release criterion has been difficult to implement at best. There are many challenges in using the IFB approach. These include: release criterion is required per MARSSIM; multiple reference areas need to be established; and data presentation. Potential methods to overcome these challenges are discussed. USACE has utilized alternative statistical approaches as well as the IFB approach discussed in MARSSIM for specific purposes at FUSRAP sites. Alternatives to the IFB approach discussed in this paper include other statistical tests such as the Tukey Kramer test. These alternatives may be better suited to release an area of a property prior to the development of release criteria. USACE has found using the IFB criterion useful in certain specific circumstances. These include post MARSSIM Scenario A final status survey data evaluations and for review of historical data. The challenges, alternatives, and circumstances to use the IFB approach are discussed. Other environmental remediation projects attempting to utilize IFB as a criterion may benefit from the USACE experiences as discussed herein. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Neurohumoral indicators of efficacy radiofrequency cardiac denervation

In this study, we compared pre- and postoperative parameters of the cardiac sympathetic innervation. The aim of the study was to examine the approaches to evaluating the quality of radiofrequency (RF)-induced cardiac denervation by using non-invasive and laboratory methods. The study included 32 people with long-lasting persistent atrial fibrillation (AF). The patients were divided into 2 groups according to the objectives of the study: group 1 (main) - 21 patients with mitral valve diseases, which simultaneously with radiofrequency ablation (RFA) AF carried out on the effects of the paraganglionic nervous plexuses by C. Pappone (2004) and N. Doll (2008) schemes. The second group (control) contained 11 patients with heart diseases in sinus rhythm (the RF denervation not been performed). All patients, who underwent surgical treatment, were received examination of cardiac sympathetic tone by using {sup 123}I-MIBG. All of them made blood analysis from ascending aorta and coronary sinus to determine the level of norepinephrine and its metabolites before and after cardiac denervation. Data of radionuclide examination are correlating with laboratory data.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Are We Appropriately Selecting Therapy For Patients With Cervical Cancer? Longitudinal Patterns-of-Care Analysis for Stage IB-IIB Cervical Cancer

Purpose: We performed a patterns-of-care analysis evaluating the effects of newer technology and recent research findings on treatment decisions over 26 years to determine whether patients with cervical cancer are being appropriately selected for treatment to optimize the therapeutic ratio. Methods and Materials: A retrospective analysis was conducted using the Surveillance, Epidemiology and End Results (SEER) program from 1983 to 2009. We identified 10,933 women with stage IB-IIB cervical carcinoma. Results: Of the 10,933 subjects identified, 40.1% received surgery, 26.8% received radiation (RT), and 33.1% received surgery plus RT. RT use increased after 2000 compared to prior to 2000, with a corresponding decrease in surgery and surgery plus RT. Among patients with risk factors including tumor size >4 cm, positive parametria, and positive lymph nodes, declining use of surgery plus RT was observed. However, 23% of patients with tumors >4 cm, 20% of patients with positive parametria, and 55% of node-positive patients continued to receive surgery plus RT as of 2009. Factors associated with increased use of surgery plus RT included patient age <50 and node-positive status. Conclusions: In this largest patterns-of-care analysis to date for patients with locally advanced cervical cancer, we found a substantial proportion of patients continue to undergo surgery followed by radiation, despite randomized data supporting the use of definitive radiation therapy, with lower morbidity than surgery and radiation.

62 RADIOLOGY AND NUCLEAR MEDICINE↗