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DOE OSTI2016

Parameterization of a Cookoff Model for LX-07

A thermal decomposition model for PBX 9501 (95% HMX, 2.5% Estane® binder, 2.5% BDNPA/F nitro-plasticizer) was implemented by Dickson, et. al. The objective in this study is to estimate parameters associated with this kinetics model so it can be applied to carry out thermal ignition predictions for LX-07 (90% HMX, 10% Viton binder). LX-07 thermal ignition experiments have been carried out using the “Sandia Instrumented Thermal Ignition Apparatus”, SITI. The SITI design consists of solid cylinders (1” diameter × 1” height) of high explosive (HE) confined by a cylindrical aluminum case. An electric heater is wrapped around the outer surface of the case. This heater produces a temperature heating ramp on the outer surface of the case. Internal thermocouples measure the HE temperature rise from the center to locations close to the HE-aluminum interface. The energetic material is heated until thermal ignition occurs. A two–dimensional axisymmetric heat conduction finite element model is used to simulate these experiments. The HE thermal decomposition kinetics is coupled to a heat conduction model trough the definition of an energy source term. The parameters used to define the HE thermal decomposition model are optimized to obtain a good agreement with the experimental time to thermal ignition and temperatures. Also, heat capacity and thermal conductivity of the LX-07 mixture were estimated using temperatures measured at the center of the HE before the solid to solid HMX phase transition occurred.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗

DOE OSTI2017

Triple Plate Mold Final Report: Optimization of the Mold Design and Casting Parameters for a Thin U-10mo Fuel Casting

This work describes the experiments and modeling that have been performed to improve and try to optimize the simultaneous casting of three plates of U-10wt%Mo in a single coil vacuum induction melting (VIM) furnace. The plates of interest are 280 mm wide by 203 mm tall by 5 mm thick (11" x 8" x 0.2"). The initial mold design and processing parameters were supplied by Y-12. The mold and casting cavity were instrumented with a number of thermocouples, and the casting performed to determine the thermal history of the mold and casting. The resulting cast plates were radiographed and numerous defects identified. Metallography was performed to help identify the nature of the radiographically observed defects. This information was then used to validate a mold filling and solidification model of that casting. Based on the initial casting, good casting design practice, and process simulation of several design alternatives, a revised design was developed with the goal of minimizing casting defects such as porosity. The redesigned mold had a larger hot-top and had its long axis along the horizontal direction. These changes were to try to develop a strong thermal gradient conducive to good feeding and minimization of micro- and macroporosity in the cast plates. An instrumented casting was then performed with the revised mold design and a linear distributor. This design yielded cast plates with significantly less radiographically identified defects. Unfortunately, there was significant variation in plate weight and metal content in their hot-tops. Fluid flow simulations were then performed on this mold/distributor design. This helped identify the issue with this linear distributor design. Additional simulations were then performed on candidate distributor redesigns and a preferred distributor annular design was identified. This improved annular design was used to produce a third instrumented casting with favorable results. These refined designs and their radiographic characterization are compared to the initial design.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Results of thermal test of metallic molybdenum disk target and fast-acting valve testing

This report describes the irradiation conditions for thermal testing of helium-cooled metallic disk targets that was conducted on March 9, 2016, at the Argonne National Laboratory electron linac. The four disks in this irradiation were pressed and sintered by Oak Ridge National Laboratory from molybdenum metal powder. Two of those disks were instrumented with thermocouples. Also reported are results of testing a fast-acting-valve system, which was designed to protect the accelerator in case of a target-window failure.

36 MATERIALS SCIENCE↗

DOE OSTI2016

NEET Enhanced Micro-Pocket Fission Detector for High Temperature Reactors - FY16 Status Report

A collaboration between the Idaho National Laboratory (INL), the Kansas State University (KSU), and the French Atomic Energy Agency, Commissariat à l'Énergie Atomique et aux Energies Alternatives, (CEA), has been initiated by the Nuclear Energy Enabling Technologies (NEET) Advanced Sensors and Instrumentation (ASI) program for developing and testing High Temperature Micro-Pocket Fission Detectors (HT MPFD), which are compact fission chambers capable of simultaneously measuring thermal neutron flux, fast neutron flux and temperature within a single package for temperatures up to 800 °C. The MPFD technology utilizes a small, multi-purpose, robust, in-core fission chambers and thermocouple. As discussed within this report, the small size, variable sensitivity, and increased accuracy of the MPFD technology represent a revolutionary improvement over current methods used to support irradiations in US Material Test Reactors (MTRs). Previous research conducted through NEET ASI1-3 has shown that the MPFD technology could be made robust and was successfully tested in a reactor core. This new project will further the MPFD technology for higher temperature regimes and other reactor applications by developing a HT MPFD suitable for temperatures up to 800 °C. This report summarizes the research progress for year two of this three year project. Highlights from research accomplishments include: • Continuation of a joint collaboration between INL, KSU, and CEA. Note that CEA is participating at their own expense because of interest in this unique new sensor. • An updated parallel wire HT MPFD design was developed. • Program support for HT MPFD deployments was given to Accident Tolerant Fuels (ATF) and Advanced Gas-cooled Reactor (AGR) irradiation test programs. • Quality approved materials for HT MPFD construction were procured by irradiation test programs for upcoming deployments. • KSU improved and performed electrical contact and fissile material plating. • KSU delivered fissile HT MPFD parts to INL for final construction of HT MPFD prototype. • A prototype HT MPFD was constructed and analyzed at INL. • The HT MPFD has been modeled in MCNP to optimize the amount of fissile material deposition. • The HT MPFD has been modeled in MCNP to optimize the sensor location in the irradiation test. • The fissile material deposition is undergoing independent verifications. • Detector amplifier electronics have been revised and tested by KSU. • Several project meetings were held at INL and KSU to discuss the roles and responsibilities between INL, KSU, and CEA for development and deployment of the HT MPFDs. As documented in this report, FY16 funding has allowed the project to meet year two planned accomplishments to develop a HT MPFD. In addition, the accomplishments of this project have attracted independent funding from other Department of Energy Office of Nuclear Energy (DOE-NE) programs for MTR irradiations of the MPFD technology. These are significant opportunities for this NEET Enhanced Micro-Pocket Fission Detector for High Temperature Reactors project because the irradiation expense of these experiments could not be included in the original project scope.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2017

Mock Target Window OTR and IR Design and Testing

In order to fully verify temperature measurements made on the target window using infrared (IR) optical non-contact methods, actual comparative measurements are made with a real beam distribution as the heat source using Argonne National Laboratory’s (ANL) 35 MeV electron accelerator. Using Monte Carlo N-Particle (MCNP) simulations and thermal Finite Element Analysis (FEA), a cooled mock target window with thermocouple implants is designed to be used in such a test to achieve window temperatures up to 700°C. An uncoated and blackcoated mock window is designed to enhance the IR temperature measurements and verify optical transmitted radiation (OTR) imagery. This allows us to fully verify and characterize our temperature accuracy with our current IR camera method and any future method we may wish to explore using actual production conditions. This test also provides us with valuable conclusions/concerns regarding the calibration method we developed using our IR test stand at TA-53 in MPF-14.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2017

FY 2017 Status of Sodium Freezing and Remelting Tests

The Sodium Freezing and Remelting experiment facility at Argonne National Laboratory has been significantly modified and improved. The main improvement was replacement of the two original stainless steel test sections that had strain gages limited by their bonds to the stainless steel to maximum temperatures of 350°C with a single new test section with strain gages that can be utilized up to 980°C and a thin wall to enhance measured strains. Wetting of stainless steel by sodium within a practical time of one to a few days is expected to require temperatures of 450°C or greater. Thus, the higher temperature strain gages enable wetting in a short time of a few days. Wetting below 350°C would have required an impractically long time of at least weeks. Other improvements included upgrading of the loop configuration, incorporation of a cold finger to purify sodium, a new data acquisition system, and reinstallation of the many heaters, heater controllers, and thermocouples. After the loop had been heated to 400°C for about two hours, an initial sodium freezing test was conducted. It is thought that the sodium might have at least partially wetted the stainless steel wall under these conditions. The strain gage measurements indicate that an incremental step inward deformation of the test section thin wall occurred as the temperature decreased through the sodium freezing temperature. This behavior is consistent with sodium initially adhering to the stainless steel inner wall but breaking away from the wall as the freezing sodium contracted. Conduct of additional sodium freezing tests under well wetted conditions was prevented as a result of stoppage of all electrical work at Argonne by the Laboratory Director on July 25, 2017. A pathway to resuming electrical work is now in place at Argonne and additional sodium freezing testing will resume next fiscal year.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Argonne Bubble Experiment Thermal Model Development III

This report describes the continuation of the work reported in “Argonne Bubble Experiment Thermal Model Development” and “Argonne Bubble Experiment Thermal Model Development II”. The experiment was performed at Argonne National Laboratory (ANL) in 2014. A rastered 35 MeV electron beam deposited power in a solution of uranyl sulfate, generating heat and radiolytic gas bubbles. Irradiations were performed at beam power levels between 6 and 15 kW. Solution temperatures were measured by thermocouples, and gas bubble behavior was recorded. The previous report2 described the Monte-Carlo N-Particle (MCNP) calculations and Computational Fluid Dynamics (CFD) analysis performed on the as-built solution vessel geometry. The CFD simulations in the current analysis were performed using Ansys Fluent, Ver. 17.2. The same power profiles determined from MCNP calculations in earlier work were used for the 12 and 15 kW simulations. The primary goal of the current work is to calculate the temperature profiles for the 12 and 15 kW cases using reasonable estimates for the gas generation rate, based on images of the bubbles recorded during the irradiations. Temperature profiles resulting from the CFD calculations are compared to experimental measurements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2017

Enhanced Micro-Pocket Fission Detector for High Temperature Reactors - FY17 FInal Project Report

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2018

Zr Recycle Installation of Out-of-Cell Accessory Facilities

Design, fabrication, and installation of the out-of-cell accessory equipment for the Zr Recycle Project tests with actual used nuclear fuel (UNF) cladding was completed on September 9, 2016, shortly before installation of the hot cell equipment. As indicated in Figures 1 and 2, the out -of- cell equipment includes (1) a gas cabinet for a chlorine cylinder, (2) piping and valves, (3) flow control valves, and (4) two shielded plugs in the hot cell walls, one for gas flow piping from the Charging Area and one for electric power and thermocouple instrumentation from the Operating Area. In addition, wiring for flow control signals and piping for Argon gas transfer were run through the existing pass-through tube underneath the hot cell to enable operation of flow controller signals in the Operating Area to the control valves and piping located in the Charging Area. The shielded plug from the Charging Area into the hot cell contains spare lines that can be used in the future for transferring off-gas from the test equipment to tritium traps located in the Charging Area, and then back into the hot cell for caustic scrubbing and venting.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2018

Resistively Heated Target Tests Using Helium Flow Loop

A helium flow and heat transfer experiment has been conducted using the helium flow loop facility at the Los Alamos National Laboratory. In order to replicate the helium cooled Mo-100 plant design disks during beam heating, an array of resistive heaters were placed within the helium flow loop, and cooled via helium. The resistively heated test piece is comprised of seven ceramic electric heaters with embedded thermocouples allowing temperature measurements of each heater.Computation fluid dynamic (CFD) simulations and analysis from theory are compared to the experiment results in order to have predictable capabilities for future experiments.

42 ENGINEERING↗

DOE OSTI2018

Metal 3D Printing of Low-NOX Fuel Injectors with Integrated Temperature Sensors (Final Technical Report)

This technical report presents the exploration of design and prototyping of an Oxy-fuel injector with integrated temperature sensing capabilities using Additive Manufacturing (AM) technology. The AM process has proven itself as a viable method to fabricate complex shapes for custom-designed metallic components rapidly. The lack of assembly requirements and the virtually unlimited geometrical complexity renders the AM process particularly attractive for fabricating complex energy system components. The unique layer-by-layer fabrication technique allows the embedding of sensors within complex components early in the design process. Sensors can be embedded (without post-production component modifications) in AM-fabricated components through two distinct processes: Stop and Go or Post-Integration. The Stop and Go fabrication process allows sensor placement within a cavity during fabrication; where the process is allowed to continue upon sensor placement. Post-integration process supports selective build of customized compartments for sensors within the part. The Stop and Go process requires an extremely accurate re-alignment of the powder-bed during the restart process. Additionally, metallization and shorting of sensors due to a considerably high temperature of the AM process creates significant fabrication challenges and limit the types of sensors that can be embedded. The Post-Integration of sensors is a practical alternative for components that can be effectively designed and fabricated with pre-built complex sensor compartments without the need for post-production component modifications. The proposed effort aimed at exploring the fabrication of an oxy-fuel injector designed for high-pressure Oxy-Combustion applications (Combustor for Directly Heated Supercritical Power Cycle) with integrated temperature measurement capabilities using the AM technique. Since the current design methodology of injectors is based on conventional fabrication techniques (e.g., multi-step machining and welding processes), a new paradigm of design methodology needs to be developed for their adaptation in the AM fabrication process. One of the most challenging issues addressed in powder bed fusion is the removal of powder from internal channels/cavities as the powder to be removed has been lightly sintered during the fabrication process. In this research, a major task has been assigned to developing and evaluating powder removal techniques that will ultimately be used when removing sintered powder from cavities/channels used for sensor placement. Achieving thorough powder removal will permit the incorporation of intricate cavities, integrated fasteners, or other novel features to incorporate sensors into parts directly post-fabrication – allowing for the novel, AM-based design practices to be developed and employ for sensor integration. The designed injector was initially tested at atmospheric conditions to review its successful operation. The tests were carried out for different firing inputs; with a minimum of 55 kW and a maximum of 275 kW. Later tests were carried out for pressurized conditions between 82 kW to 275 kW firing input. A pressure of 16.35bar was observed in the combustion chamber pressure during the pressurized test of 275 kW firing input; test duration was 15 seconds. Integrated thermocouples within the injector provided temperature data for test operations. The data revealed during the atmospheric condition the injector temperature is almost unaffected by the combustion. However, during the pressurized condition, the injector temperature rapidly up to 205°C within 15 seconds; at a 275 kW firing input.

42 ENGINEERING↗

DOE OSTI2014

AGR-2 Daily As-run Thermal Analyses

This report documents the daily as-run thermal analyses performed on Advanced Gas-cooled Reactor (AGR) experiment AGR-2 in the Advanced Test Reactor (ATR) for capsules 2,3,5, and 6. Capsule 1 (French) results are in Appendix F, while Capsule 4 (South African) results are in Appendix G. Appendix F, and G are separate documents Several fuel and material irradiation experiments, which support the development of the Next Generation Nuclear Plant (NGNP), are planned for the Advanced Gas Reactor Fuel Development and Qualification Program. The goals of these experiments are to provide irradiation performance data to support fuel process development, to qualify fuel for normal operating conditions, to support development and validation of fuel performance and fission product transport models and codes, and to provide irradiated fuel and materials for post-irradiation examination (PIE) and safety testing. AGR-2 was the second in this series of planned experiments to test tristructural-isotropic (TRISO)-coated, low enriched uranium oxycarbide (LEUCO) fuel. The AGR-2 experiment was intended to serve as a follow-on to the AGR-1 experiment. The AGR-2 experiment is a high temperature fuel particle test. The test train planned for AGR-2 is based on the experience gained from previous irradiations in the ATR, using instrumented lead experiments. Instrumented lead experiments are used for irradiations requiring a controlled environment and monitored parameters. The experiment test train positions the fuel within the test location and contains sweep gas lines and thermocouple wiring that is routed through access ports to external support systems. The AGR-2 experiment is comprised of six individual capsules, approximately 1.375-in. in diameter by 6-in. long, stacked on top of each other to form the test train. Each capsule contains 12 fueled compacts that are approximately 0.5-in. in diameter by 1-in. long. The compacts are composed of fuel particles bound together by a carbon matrix. Each compact contains approximately 4,150 fissile particles (35 vol% particle packing fraction). Each capsule will be supplied with a flowing helium/neon gas mixture to control the test temperature and to sweep any fission gases that are released to the fission product monitoring system. Temperature control is accomplished by adjusting the gas mixture ratio of the two gases (helium and neon) with differing thermal conductivities. Many similarities exist between this thermal analysis for AGR-2 with the AGR-1 daily as-run report in [1]. Gas gaps were taken from as built drawings in Reference [2]. The finite element heat transfer code ABAQUS [3] was used to perform the thermal analysis. The AGR-2 experiment was placed in the B-12 position in the ATR core as shown in Figure 1. The AGR-2 experiment capsule assembly consists of six capsules axially stacked. Each capsule contains a graphite holder with three equally spaced fuel compact holder openings as shown in Figure 2. Each holder opening accommodates four axially stacked fuel compacts. Thus, each capsule has three stacks by four fuel compacts per stack for a total of 12 fuel compacts per capsule. So, within the entire AGR-2 experiment capsule assembly, there are six capsules by 12 fuel compacts per capsule for a total of 72 fuel compacts. Six finite element heat transfer models were created (one for each capsule), each with a corresponding gas gap.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2019

Thermal Analysis Of Saltstone Disposal Units

SRR requested that SRNL develop a two-dimensional computer simulation model to be capable of predicting grout temperatures attained in Saltstone Disposal Units (SDUs) during the transient addition of saltstone grout and its subsequent storage period. A simulation model was developed to calculate the transient grout temperatures of the SDU facility by taking an axisymmetric and two-dimensional Computational Fluid Dynamics (CFD) approach. The final performance calculations were based on the conduction and radiation model without a convection cooling mechanism for conservative estimate of the grout temperatures and computational efficiency. While convection within the SDU is disabled in the current calculations, the simulation model has the capability of turning convection back on if desired by the user. Hence, the thermal model in its current configuration is best characterized as a finite-volume heat transfer model. However, given that the model can account for convection if desired by the user, it will be referred to as a CFD model. The grout material contains a transient heat source due to the exothermic hydration reactions of the cementitious material mixed with salt solution. The model can predict the transient temperatures at point locations within the poured grout and the overlying vapor space, and at the interior and exterior surfaces of the structure. The thermal model has been developed for two SDUs at the Savannah River Site (SRS); namely, SDU 2A and SDU 6. SDU 2A is a cylindrical unit measuring 150 feet (ft) in diameter, 22 ft tall, and holds approximately three million gallons of grout. SDU 6 is 375 ft in diameter and 43 ft high with a capacity of over thirty million gallons. Prior to performing the thermal calculations for the SDU 6 facility, the benchmarking test for the smaller SDU 2A unit was performed to establish the solution method and to verify the computational results using existing thermocouple data. Based on the Lagrangian discrete method and boundary conditions established by the SDU 2A benchmarking test, the CFD calculations were performed to predict the transient temperatures at local positions of the poured grout and air spaces within the SDU 6 structure.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2018

Thermal evaluations for mixed organic and nitrate salt drums in interim storage at the WCS Federal Waste Facility

Waste Control Specialists LLC (WCS) operates the Federal Waste Facility (FWF) in Texas that is licensed to process and store certain types of mixed low-level radioactive waste packages. The specific waste currently housed at WCS includes some of the transuranic (TRU) waste that originated at the DOE Los Alamos National Laboratory (LANL) and are destined for disposal at the DOE Waste Isolation Pilot Plant (WIPP) facility. The TRU waste within each Standard Waste Box (SWB) was packaged in 55-gallon drums at LANL. Some of the drums contain mixed organic and nitrate salt contents suspected of experiencing a chemical reaction. The drums (up to four drums in a SWB) were then overpacked in a SWB prior to shipment to WCS. In the most common configuration, WCS placed the SWB containing the drums on metal pallets and stored two SWBs into Modular Concrete Canisters (MCCs) in a double stacked array. The MCCs were placed in a staggered array at a segregated area of the FWF and covered with sand to mitigate the heating that occurred when stored above ground on waste pads. The temporary interment is also intended to provide additional containment of the suspect reactive waste to mitigate release of radioactivity in an incident such as that which occurred at WIPP for one such drum. Void space of each MCC was filled with 1-inch pea gravel to facilitate retrievability. Thermocouple probes were placed within each MCC to monitor heat generation from the SWBs and the MCC lids were closed. The primary objective of this analysis was to estimate the heat generation of the SWB drum contents when the SWB package temperature inside the MCC and the FWF ambient temperature were monitored.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2019

Phase separation and crystallization of complex borosilicate melts for glass-ceramic waste forms

Waste loadings of reprocessed spent nuclear fuel vitrified into borosilicate glass can be increased by precipitating environmentally stable phases concentrated with waste components in a chemically stable glass matrix. The principal objective of this study was to characterize the development of crystalline powellite (CaMoO 4 and related phases) and oxyapatite (Ca 2 LN 8 Si 6 O 26 ) in borosilicate glass-ceramics and to determine how the formation of those phases affected its chemical durability. Borosilicate glasses provided by PNNL were re-melted and quenched at rates from over 300°C/s to ~0.05°C/s. Isothermal heat treatment experiments were conducted by quenching melts in a molten tin bath at various temperatures, holding for periods of time, and then quenching in a water bath. Analytical electron microscopy and x-ray diffraction provided information about the kinetics of the phase separation and crystallization processes responsible for microstructural development. Powellite and oxyapatite crystals formed during slower quench rates and longer isothermal times, and time-temperature-transformation (TTT) diagrams were developed from the latter experiments. A hot thermocouple test (HTT) system was built to rapidly quench melts and hold them at set times to provide supplementary TTT information, but that system was not as sensitive to the phase transformations as other tests. Corrosion tests were performed to understand how the individual phases in the glass-ceramic affect its overall chemical durability. Product consistency tests, performed at Missouri S&T and at Savannah River National Lab, provided release rates of major elements from samples as a function of cooling rate, and atomic force microscopy and profilometry measurements of surface topology determined the relative corrosion rates of the residual glass and oxyapatite phases. Faster dissolution rates were measured from samples cooled more slowly and these were explained by the greater fractions of B 2 O 3 in the residual glass phase after the formation of oxyapatite and powellite. Oxyapatite was found to be more durable than the residual glass.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2019

Development of the Ultimate One-Dimensional Time to Explosion (UODTX) Apparatus

With recent advancements in experimental capabilities and worldwide improvement of digital data acquisition and control, there is sufficient justification to develop a new version of the One Dimensional Time to eXplosion (ODTX) system to allow for additional diagnostics and improved control to increase sample throughput and increase the adaptability of future experiments. The legacy ODTX system was designed to measure time to explosion (TTX) for a given temperature, which it does well, but it was not equipped to handle the recent experimental advances of Pressure-ODTX (PODTX) and Composition-ODTX (CODTX). PODTX involves fielding a pressure transducer as an additional diagnostic and applying arbitrary heating-profiles to the system anvils. CODTX furthers this concept by including in-situ gas-composition analysis via infrared (IR) absorption techniques with plans to extend CODTX to solid composition detection and in-situ mass spectrometry (MS). The legacy ODTX system was not built with these experiments in mind and performing them involves substantial modifications and downtime to the existing machine. Developing a standalone system that can perform all C/P/ODTX experiments and is adaptable to unconceived experiments would allow for the continued use of ODTX as a work-horse for Small Scale Safety Testing (SSST), but also provide a testbed for new explosive safety research. This system would ultimately be housed in the neighboring ODTX cell and would live at the High Explosive Application Facility (HEAF) until the end of its service life. HEAF, Chemistry, and Engineering would be the primary stakeholders for the system’s design as they all have experiments that they want to perform. Engineering would be responsible for the system development and would work closely with HEAF to ensure that the system is built with high explosive (HE) safety in mind. By the end of development and after product realization, HEAF/Chemistry would be the system owner, operator, and primary user. The proposed system design is highly influenced by the existing ODTX design. The system will have load frame to support the experiment, anvils to confine the explosive, and some means of applying confining pressure. The samples will be able to be heated and cooled through the confining the anvils. The biggest change from the legacy design is the ability to add diagnostics to the experiment as needed: thermocouples (TCs), resistance temperature detectors (RTDs), pressure transducers (PTs), infrared transmittance/absorbance (IR), mass spectrometry (MS), strain gages (SGs), photonic doppler velocimeter (PDV), as well as arbitrary 4-20 mV signals and +/- 10 VDC signals. The current design does not allow for flexibility in that respect and is hardwired with a few diagnostic channels. The onus will fall on designing a load frame that can support system modifications as well as a data acquisition system that can handle the multitude of signal types.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Off-Normal Scenarios Using Resistively Heated Targets

This report describes the continuation of thermal experiments using the resistively heated target assembly within the helium flow loop at LANSCE that is described in the report, Resistively Heated Target Tests Using Helium Flow Loop, by Alexander Wass et al. In order to replicate off-normal operating scenarios of the helium cooled Mo-100 plant design disks during beam heating, an array of resistive heaters were placed within the helium flow loop, cooled via helium, and modified slightly. The resistively heated test piece is comprised of seven ceramic electric heaters with embedded thermocouples allowing temperature measurements of each heater. A total of three scenarios were performed. One unmodified scenario, and two off-normal scenarios were conducted to simulate a blocked cooling channel due to debris within the flow loop and a broken disk during in-beam heating at the Mo-99 production facility. A removable insert was placed within a cooling channel to block the flow of helium, and a resistive heater was removed to simulate a broken disk that had been evacuated from the target assembly. The inlet and outlet cooling pipe employs rectangular tubing to make a 90° bend at a radius consistent with and practical for the actual plant design.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Embedment of sensors in ceramic structures

Ceramic materials such as silicon carbide (SiC) are attractive for many nuclear applications due to their ability to withstand high temperatures, which inherently improve the thermal efficiency of the power conversion cycle and can in some cases provide high-temperature process heat. SiC is particularly attractive because of its high-temperature strength retention, stability under neutron irradiation, and low neutron absorption. The TCR program has recently demonstrated the ability to fabricate monolithic SiC components with complex geometries using a binder jet additive manufacturing technique followed by densification using chemical vapor infiltration (CVI). This technology presents an opportunity to embed sensors within ceramic components at critical locations that allow for enhanced process monitoring and control of advanced nuclear energy systems. The challenges with embedding sensors in ceramic components are to identify appropriate materials that can survive the CVI process, remain embedded after cooling to room temperature, and be suitable for operation in a high-temperature nuclear environment. This report summarizes the sensors that are being considered for embedding within ceramics, the sensor embedding process, material compatibility studies, and characterization of the embedded components. Material selection is first guided by computational thermodynamics and is confirmed by embedding coupons and examining material interactions using electron microscopy. This work shows that a wide range of refractory metals, as well as certain fiber optic sensors, can be successfully embedded in 3D-printed SiC. Future work will involve testing of functional sensors including thermocouples and optical fiber-based, spatially distributed temperature/strain sensors.

36 MATERIALS SCIENCE↗