Joshua Daw

Options Extending the Applicability of High-Temperature Irradiation-Resistant Thermocouples

Abstract Several options have been identified that could further enhance the reliability and extend the applicability of high-temperature irradiation-resistant thermocouples (HTIR-TCs) developed by the Idaho National Laboratory (INL) for in-pile testing, allowing their use in temperature applications as high as 1800%C.The INL and the University of Idaho (UI) investigated these options with the ultimate objective of providing recommendations for alternate thermocouple designs that are optimized for various applications. This paper reports results from INL/UI investigations. Results are reported from tests completed to evaluate the ductility, resolution, transient response, and stability of thermocouples made from specially formulated alloys of molybdenum and niobium,not considered in initial HTIR-TC development. In addition, this paper reports insights gained by comparing the performance of HTIR-TCs fabricated with various heat Ntreatments and alternate geometries.

ATR NSUF Instrumentation Enhancement Efforts

Abstract A key component of the Advanced Test Reactor (ATR) National Scientific User Facility (NSUF) effort is to expand instrumentation available to users conducting irradiation tests in this unique facility. In particular, development of sensors capable of providing real-time measurements of key irradiation parameters is emphasized because of their potential to increase data fidelity and reduce posttest examination costs. This paper describes the strategy for identifying new instrumentation needed for ATR irradiations and the program underway to develop and evaluate new sensors to address these needs. Accomplishments from this program are illustrated by describing new sensors now available to users of the ATR NSUF. In addition, progress is reported on current research efforts to provide improved in-pile instrumentation to users.

Hot Wire Needle Probe for In-Reactor Thermal Conductivity Measurement

Thermal conductivity is a key property that must be known for proper design, test, and application of new fuels and structural materials in nuclear reactors. Thermal conductivity is highly dependent on the physical structure, chemical composition, and the state of the material. Typically, thermal conductivity changes that occur during irradiation are measured out-of-pile using a “cook and look” approach. Repeatedly removing samples from a test reactor to measurements is expensive, has the potential to disturb phenomena of interest, and only provides understanding of the samples end state when each measurement is made. There are also limited thermophysical property data for advanced fuels. Such data are needed for simulation design codes, the development of next generation reactors, and advanced fuels for existing nuclear plants. Being able to quickly characterize fuel thermal conductivity during irradiation can improve the fidelity of data, reduce costs of post-irradiation examinations, increase understanding of how fuels behave under irradiation, and confirm or improve existing thermal conductivity measurement techniques. This paper discusses efforts to develop and evaluate an in-pile thermal conductivity sensor based on a hot wire needle probe. Testing has been performed on samples with thermal conductivities ranging from 0.2 to 22 W/m·K at temperatures ranging from 20 °C to 600 °C. Thermal conductivity values measured using the needle probe match data found in the literature to within 5% for samples tested at room temperature, 6% for low thermal conductivity samples tested at high temperatures, and 10% for high thermal conductivity samples tested at high temperatures.

Extension wire for high temperature irradiation resistant thermocouples

In an effort to reduce production costs for the doped molybdenum/niobium alloy high temperature irradiation resistant thermocouples (HTIR-TCs) recently developed by the Idaho National Laboratory, a series of evaluations were completed to identify an optimum compensating extension cable. Results indicate that of those combinations tested, two inexpensive, commercially-available copper–nickel alloy wires approximate the low temperature (0 °C to 500 °C) thermoelectric output of KW–Mo (molybdenum doped with tungsten and potassium silicate) versus Nb–1%Zr in HTIR-TCs. For lower temperatures (0 °C to 150 °C), which is the region where a soft extension cable is most often located, results indicate that the thermocouple emf is best replicated by the Cu–3.5%Ni versus Cu–5%Ni combination. At higher temperatures (300 °C to 500 °C), data suggest that the Cu–5%Ni versus Cu–10%Ni combination may yield data closer to those obtained with KW–Mo versus Nb–1%Zr wires.

Type C thermocouple performance at 1500 °C

Experience with Type C thermocouples operating for extended times in the 1400–1600 °C temperature range indicates that significant decalibration occurs, often leading to expensive downtime and material waste. As part of an effort to understand the mechanisms causing drift in these thermocouples, the Idaho National Laboratory conducted a long duration (3000 h) test at 1500 °C containing eight Type C thermocouples. As reported in this paper, results from this long duration test were adversely affected due to oxygen ingress. Nevertheless, results provide important insights about the impact of precipitate formation due to material phase changes on thermoelectric response. Post-test examinations indicate that the thermocouple signal was not adversely impacted by the formation of precipitates detected after 1000 h of heating at 1500 °C and suggest that the signal would not be adversely impacted by these precipitates for longer durations.

Progress towards developing neutron tolerant magnetostrictive and piezoelectric transducers

Current generation light water reactors (LWRs), sodium cooled fast reactors (SFRs), small modular reactors (SMRs), and next generation nuclear plants (NGNPs) produce harsh environments in and near the reactor core that can severely tax material performance and limit component operational life. To address this issue, several Department of Energy Office of Nuclear Energy (DOE-NE) research programs are evaluating the long duration irradiation performance of fuel and structural materials used in existing and new reactors. In order to maximize the amount of information obtained from Material Testing Reactor (MTR) irradiations, DOE is also funding development of enhanced instrumentation that will be able to obtain in-situ, real-time data on key material characteristics and properties, with unprecedented accuracy and resolution. Such data are required to validate new multi-scale, multi-physics modeling tools under development as part of a science-based, engineering driven approach to reactor development. It is n...

ICONE15-10842 INITIAL RESULTS FROM INVESTIGATIONS TO ENHANCE THE PERFORMANCE OF HIGH TEMPERATURE IRRADIATION-RESISTANT THERMOCOUPLES

Several options have been identified that could further enhance the lifetime and reliability of thermocouples developed by the Idaho National Laboratory (INL) for in-pile testing, allowing their use in higher temperatures applications (up to at least 1700 ̊C). A joint project between the INL and the University of Idaho (UI) is underway to investigate these options and, ultimately, provide recommendations for an enhanced thermocouple design. This paper presents preliminary results from this UI/INL effort. Tests show that unalloyed, but doped, molybdenum wires (ODS-Momolybdenum doped with lanthanum oxide and KW-Mo – molybdenum doped with silicon, tungsten and potassium) better retain ductility at higher temperatures than evaluated candidate undoped developmental alloys (Mo-1.6%Nb and Mo-3%Nb). Thermocouples that contain unalloyed molybdenum were also observed to have better high temperature resolution. Candidate niobium alloys (Nb-1%Zr, Nb-4%Mo, Nb-6%Mo, and Nb-8%Mo) became brittle at lower heating temperatures and shorter durations than any of the wires primarily containing molybdenum. Hence, results indicate that a combination of either ODS-Mo or KW-Mo with Nb-1%Zr appear to be the most favorable configuration. Initial results also show that thermocouple stability can also be improved by using larger diameter wires.

HTIR-TC Compensating Extension Wire Evaluations

In an effort to reduce production costs for the doped molybdenum/niobium alloy High Temperature Irradiation Resistant Thermocouples (HTIR-TCs) recently developed by the Idaho National Laboratory, a series of evaluations were completed to identify an optimum compensating extension cable. As documented in this report, results indicate that of those combinations tested, two inexpensive, commercially-available copper nickel alloy wires approximate the low temperature (0 to 500 °C) thermoelectric output of KW-Mo (molybdenum doped with tungsten and potassium silicate) versus Nb-1%Zr in HTIR-TCs. For lower temperatures (0 to 150 °C), which is the region where soft extension cable is most often located, results indicate that the thermocouple emf is best replicated by the Cu-3.5%Ni versus Cu-5%Ni combination (measured emfs were within 4% at 100 and 150 °C). At higher temperatures (300 to 500 °C), data suggest that the Cu-5%Ni versus Cu-10%Ni combination may yield data closer to that obtained with KWMo versus Nb-1%Zr wires (measured emfs were within 8%).