The thermal decomposition of the benzyl radical in a heated micro-reactor. I. Experimental findings
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Buckingham, Grant T.↗
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Research, Development and Demonstration (RD&D) Needs for Light Water Reactor (LWR) Technologies A Report to the Reactor Technology Subcommittee of the Nuclear Energy Advisory Committee (NEAC) Office of Nuclear Energy U.S. Department of Energy
The LWR RD&D Working Group developed a detailed list of RD&D suggestions and recommendations, which are provided in Appendix D. The Working Group then undertook a systematic ranking process, described in Appendix E. The results of the ranking process are not meant to be a strict set of priorities, but rather should provide insight into how the items generally ranked within the Working Group. Future discussions and investigation into these items could provide information that would support a change in these priorities or in their emphasis. The results of this prioritization are provided below. Note that in general, many RD&D ideas are applicable to both new Advanced Light Water Reactor (ALWR) plants and currently operating plants.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
Gamma-ray Analysis of the Pressurized-Water-Reactor and Boiling-Water-Reactor Assemblies
Conclusions: Passive gamma analysis can be used to determine BU, CT, and IE of spent fuel assembly. Assemblies with small CT give best results.; Without any operator declaration, a 10 minutes measurement time of a PWR assembly can give the results for BU, CT, and IE with about 3% accuracy.; BWR analysis is more complicated and less effective than PWR and the results are somewhat less accurate.; A set of 4 measurements at 4 corners of an assembly can average out the variations of the assembly positions in the reactor during the burn cycles and can result in a better accuracy.
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
Nuclear reactor target assemblies, nuclear reactor configurations, and methods for producing isotopes, modifying materials within target material, and/or characterizing material within a target material
Target assemblies are provided that can include a uranium-comprising annulus. The assemblies can include target material consisting essentially of non-uranium material within the volume of the annulus. Reactors are disclosed that can include one or more discrete zones configured to receive target material. At least one uranium-comprising annulus can be within one or more of the zones. Methods for producing isotopes within target material are also disclosed, with the methods including providing neutrons to target material within a uranium-comprising annulus. Methods for modifying materials within target material are disclosed as well as are methods for characterizing material within a target material.
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
Summary of Thermocouple Performance in the Advanced Gas Reactor Experiment AGR-5/6/7 During Irradiation in the Advanced Test Reactor
The Advanced Gas Reactor -5/6/7 (AGR-5/6/7) experiment was the fourth and final experiment in the AGR experiment series and completed irradiation in July 2020. It serves as the formal fuel qualification test for the TRISO fuels under development by the US Department of Energy. This experiment was designed to irradiate fuel particles at temperatures ranging from 800°C ? 1500°C. The high end of the range created unique challenges for thermocouple-based temperature measurements. Commercially available high-temperature platinum-rhodium thermocouples (Types S, R, and B) and tungsten-rhenium thermocouples (Type C) suffer rapid decalibration due to transmutation of the thermoelements from neutron absorption. A special low neutron cross-section thermocouple system based on molybdenum/niobium thermoelements called High Temperature Irradiation Resistant thermocouple (HTIR-TC) has been under development at INL since circa 2004. Several examples of this thermocouple type were incorporated into regions of the test operating above 1200°C. For regions in the test operating in the 1000°C ? 1200°C range, high-performance versions of Type N thermocouples recently developed at Cambridge University were installed. Standard Type N thermocouples were used in regions of the test operating below 1000°C. A total of 54 thermocouples were incorporated into the test. A report of the performance of this large heterogenous set of thermocouples over the first third of the irradiation was previously provided (ANIMMA 2019). This follow-on paper discusses results from the balance of the experiment (Feb 2019 - July 2020). Special attention is focused on potential drift of thermocouples operating in the higher temperature regions.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Summary of Thermocouple Performance in the Advanced Gas Reactor Experiment AGR-5/6/7 During Irradiation in the Advanced Test Reactor
This is a conference presentation ppt file. The following abstract is for the entire conference paper - which will later be the subject of a PRS artifact The Advanced Gas Reactor -5/6/7 (AGR-5/6/7) experiment was the fourth and final experiment in the AGR experiment series and completed irradiation in July 2020. It serves as the formal fuel qualification test for the TRISO fuels under development by the US Department of Energy. This experiment was designed to irradiate fuel particles at temperatures ranging from 800°C ? 1500°C. The high end of the range created unique challenges for thermocouple-based temperature measurements. Commercially available high-temperature platinum-rhodium thermocouples (Types S, R, and B) and tungsten-rhenium thermocouples (Type C) suffer rapid decalibration due to transmutation of the thermoelements from neutron absorption. A special low neutron cross-section thermocouple system based on molybdenum/niobium thermoelements called High Temperature Irradiation Resistant thermocouple (HTIR-TC) has been under development at INL since circa 2004. Several examples of this thermocouple type were incorporated into regions of the test operating above 1200°C. For regions in the test operating in the 1000°C ? 1200°C range, high-performance versions of Type N thermocouples recently developed at Cambridge University were installed. Standard Type N thermocouples were used in regions of the test operating below 1000°C. A total of 54 thermocouples were incorporated into the test. A report of the performance of this large heterogenous set of thermocouples over the first third of the irradiation was previously provided (ANIMMA 2019). This follow-on paper discusses results from the balance of the experiment (Feb 2019 - July 2020). Special attention is focused on potential drift of thermocouples operating in the higher temperature regions.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Comparison between Point Reactor Kinetics and Spatial Dynamics for the NRAD Reactor
This memo reviews analysis of the kinetics behavior of the INL NRAD reactor.
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
On the Interpretation and Correlation of High-Temperature Ignition Delays in Reactors with Varying Thermodynamic Conditions
Ignition delay time (IDT) is a useful global metric for fuel performance screening and a major target for kinetic modeling. Measurements of IDT are conceptually straightforward, however interpretation could be complicated, especially for systems with changing temperature and pressure. Some experimental conditions in the high repetition rate miniature shock tube (HRRST) exhibit complex temperature and pressure state histories. To better interpret and correlate IDTs, especially those obtained in reactors with varying thermodynamic conditions, an inverse Livengood-Wu (L-W) integral technique is applied to de-convolve the constant condition IDTs from measured IDTs in the HRRST using information on the varying state history. In this paper, the approximate problem is demonstrated using only the measured pressure history leading up to ignition, where the temperature history is estimated based on an isentropic assumption. The IDTs of several fuels were first measured in the HRRST including isooctane and acetone to represent those fuels without strong low temperature chemistry effects. Based on the measured pressure and approximated temperature history, measurements of IDTs in the HRRST compare very favorably with those measured using more conventional techniques, including conventionally sized shock tubes, via the inverse L-W correlation with relaxed Newton iteration and Genetic Algorithm (GA). Furthermore, this study demonstrates the feasibility of using a high throughput ignition testing facility, like the HRRST to extract the constant state IDT measured in regular shock tubes, assisted by the inverse L-W correlation. It is expected with an independent temperature measurement available in the future, IDTs in a broader range of thermodynamic conditions and effects of heat loss could be better resolved.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Fully Ceramic Microencapsulated fuel in prismatic high-temperature gas-cooled reactors: Sensitivity of reactor behavior during design basis accidents to fuel properties and the potential impact of the SiC defect annealing process
We conducted reactor performance calculations to assess the potential design basis accident performance of HTGR fuel designs. Three Fully Ceramic Microencapsulated (FCM) fueled HTGR designs were developed in a previous work (Lu et al., 2018). The maximum fuel temperature in the cores fueled by these three FCM fuels was predicted to be higher than that in the reference 350-MWt mHTGR core in both normal operating conditions and during representative design basis accidents (Lu and Brown, 2019). To better understand the potential safety margins in mHTGR design basis accidents, we performed thermal-hydraulics sensitivity studies to investigate how maximum fuel temperature varies considering various parameters, e.g. thermal properties, within the ranges corresponding to the differences between the FCM-fueled prismatic mHTGR cores and the reference core with conventional fuel compacts. We found that the difference in the steady-state axial power distribution contributed the most to the difference in the maximum fuel temperature, in both normal operation and design basis accidents.Experimental data suggested that the annealing process of irradiation defects in SiC would be rapid at mHTGR relevant fuel temperatures. The bounding potential impact of the SiC annealing on the maximum fuel temperature was analyzed considering both the thermal conductivity recovery and the Wigner energy release due to the annealing of SiC. We found that the defect annealing process in SiC would at most increase the peak maximum fuel temperature of an FCM-fueled core by 40 K in loss of forced cooling accidents and by 10 K in a control rod withdrawal accident. Finally, additional experiments on the SiC defect annealing kinetics and Wigner energy release in more relevant conditions are needed.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Volatility and Viscosity Are Correlated in Terpene Secondary Organic Aerosol Formed in a Flow Reactor
Secondary organic aerosol (SOA) is a complex mixture of largely unspeciated compounds. Volatility and viscosity of the bulk organic aerosol influence new particle formation, processing, and lifetime in the atmosphere. Relationships between these properties are well-defined for pure compounds, but currently unavailable for bulk organic aerosol. In this survey study, we characterized SOA formed from a range of biogenic precursors and conditions in an oxidation flow reactor for volatility (thermodenuder), viscosity (dimer coagulation, isolation, and coalescence), and oxidation state (aerosol chemical speciation monitor). We find linear trends in log-linear and log-log plots of single-parameter representations of volatility and viscosity, with higher condensed phase fractions of extremely low and low volatility material associated with increased viscosity (R=0.69). Per this relationship, a 10% increase in the contribution of these fractions (i.e., lower volatility) results in an increase in viscosity of approximately 200%. The viscosity (at 30°C) of SOA fell between $6.2 × 10^5$ to $8.0 × 10^8$ Pa s, and thus in the semi-solid range. SOA oxidation state ranged from -1.0 and 0.1, and was weakly anti-correlated with volatility (but not viscosity). We found larger SOA mass loadings generally associated with increased volatility and decreased viscosity. Overall, the results of this preliminary study are consistent with “molecular corridor”-style frameworks employing molecular mass and volatility to estimate viscosity to bulk real-world SOA.
54 ENVIRONMENTAL SCIENCES↗
Examination of Molten Salt Reactor Relevant Elements Using Hydrothermal Synthesis
The structural chemistry of elements relevant to the FLiBe molten salt reactor, Th, U, Np, and Zr, including Ce andNd (as analogues for Pu and Am, respectively), have been examined using hydrothermal synthesis at 200 °C. These reactions serve to model the reaction of molten salts under hydrolysis conditions. The results show that U and Np formed LiAnF 5 , while Ce formed Li 4 CeF 8 . The source of U also controlled the crystal quality, where UO 2 gave small crystals, while UO 3 ·2H 2 O gave very large crystals. It is likely that Be incorporation was not observed because of the high solubility of [BeF 4 ] 2– in water. Zr formed a third product, Li 6 BeF 4 ZrF 8 , which features isolated [BeF 4 ] 2– and [ZrF 8 ] 4– units bridged by Li + . Additionally, Li 2 BeF 4 was regularly isolated. As a result, when little to no alkali metal was included in the reaction, M 3 F 12 (H 2 O) was isolated for Np, U, and Ce.
Anions↗
Synthesis of 1 nm Pd Nanoparticles in a Microfluidic Reactor: Insights from in Situ X ray Absorption Fine Structure Spectroscopy and Small-Angle X ray Scattering
In this paper we show that the temporal separation of nucleation and growth is not a necessary condition for the colloidal synthesis of monodisperse nanoparticles. The synthesis mechanism of Pd nanoparticles was determined by in situ XAFS and SAXS in a microfluidic reactor capable of millisecond up to an hour time resolution. The SAXS results showed two autocatalytic growth phases, a fast growth phase followed by a very slow growth phase. The steady increase in the number of particles throughout the two growth phases indicates the synthesis is limited by slow continuous nucleation. The transition from fast to slow growth was caused by rapid increase in bonding with the capping agent as shown by XAFS. Based on this fundamental understanding of the synthesis mechanism, we show that 1 nm monodisperse Pd nanoparticles can be synthesized at low temperature using a strong binding capping agent such as trioctylphosphine (TOP).
Environmental Molecular Sciences Laboratory↗
TRISO SiC Failure Probability for Reactivity Initiated Accidents in High-Temperature Gas-Cooled Reactors
This work analyzes the failure process of the silicon carbide (SiC) layer in tristructural isotropic (TRISO) during reactivity-initiated accident scenarios for a high-temperature gas-cooled reactor (HTGR) with BISON. Two cases are considered—a group control rod withdrawal (CRW) and a control rod ejection (CRE)—reproduced from a previous study. Failure probability is modeled using Weibull statistics, and worst-case scenario Weibull parameters are adopted to simulate the envelopes in BISON with a one-dimensional TRISO model. CRW scenario results are characterized by higher values of maximum energy deposition and final temperature and volumetric strain with respect to the CRE ones, but the latter have remarkably higher SiC failure probability, mainly due to the offset in strain rates between the two cases. This work also confirms the validity and conservatism of the performance envelopes produced in a previous work by replicating the envelope formulation using RELAP5-3D and RAVEN with a different sampling technique and obtaining consistent results. A sensitivity analysis using the Sobol variance decomposition method on SiC failure probability is then performed involving a set of inputs on both CRW and CRE. The two most important parameters are Weibull modulus and characteristic stress, and their relative importance depends on the specific case. The proposed interpretation of the results is that both energy deposition and strain rate influence the relative degree of importance of the failure parameters. Computation of 95% confidence intervals around worst-case scenario SiC failure probability values is also carried out for four different sets of Weibull parameters. Heren a new criterion for SiC TRISO quality classification built upon safety-based ranges of Weibull parameters is proposed to be integrated in future Fuel-Production Quality Assurance Plans.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Enabling liquid solvent structure analysis using hard x-ray absorption spectroscopy with a transferrable microfluidic reactor
In this study, a vacuum compatible microfluidic device, system for analysis at the liquid vacuum interface, is integrated to hard x-ray absorption spectroscopy to obtain the local structure of K 3 [Fe(CN) 6 ] in aqueous solutions with three concentrations of 0.5 M, 0.05 M, and 0.005 M. The solutions were sealed in a microchannel 500 µm wide and 300 µm deep in a portable microfluidic device. The Fe K-edge x-ray absorption spectra indicate a presence of Fe(III) in the complex in water, with an octahedral geometry coordinated with 6 C atoms in the first shell with a distance of ~1.92 Å and 6 N atoms in the second shell with a distance of ~3.10 Å. Varying the concentration has no observable influence on the structure of K 3 [Fe(CN) 6 ]. Our results demonstrate the feasibility of using microfluidic based liquid cells in large synchrotron facilities. Using portable microfludic reactors provides a viable approach to enable multifaceted measurements of liquids in the future.
25 ENERGY STORAGE↗
Unfolding neutron spectrum with Markov Chain Monte Carlo at MIT research Reactor with He-3 Neutral Current Detectors [Measuring neutron spectrum at MIT research reactor utilizing He-3 Bonner Cylinder Approach with an unfolding analysis]
Here, the Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering (CEνNS) using dark-matter-style detectors with sub-keV thresholds placed near a neutrino source, such as the MIT (research) Reactor (MITR), which operates at 5.5 MW generating approximately 2.2 × 10 18 ν/second in its core. Currently, Ricochet is characterizing the backgrounds at MITR, the main component of which comes in the form of neutrons emitted from the core simultaneous with the neutrino signal. To characterize this background, we wrapped Bonner cylinders around a 3 2 He thermal neutron detector, whose data was then unfolded via a Markov Chain Monte Carlo (MCMC) to produce a neutron energy spectrum across several orders of magnitude. We discuss the resulting spectrum and its implications for deploying Ricochet at the MITR site as well as the feasibility of reducing this background level via the addition of polyethylene shielding around the detector setup.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Reactor Design And Fuel Management For Pebble Bed High Temperature Reactors
PEBBED is an integrated code performing core neutron diffusion, thermal fluid, and associated cross section generation for pebble bed high temperature reactors. The code specializes in equilibrium core cycle analysis.
Gougar, HansD↗