Keith G. Condie

Thermocouples for High-Temperature In-Pile Testing

Traditional methods for measuring in-pile temperatures degrade above 1100°C. Hence, the Idaho National Laboratory (INL) initiated a project to explore the use of specialized thermocouples for high temperature in-pile applications. Efforts to develop, fabricate, and evaluate specialized high-temperature thermocouples for in-pile applications suggest that several material combinations are viable. Tests show that several low-neutron cross-section candidate materials resist material interactions and remain ductile at high temperatures. In addition, results indicate that the candidate thermoelements have a thermoelectric response that is single-valued and repeatable with acceptable resolution. The selection of the thermocouple materials depends on desired peak temperature and accuracy requirements. For applications at or above 1600°C, tests indicate that thermocouples having doped molybdenum and Nb-1%Zr thermoelement wires, HfO2 insulation, and a Nb-1%Zr sheath could be used. INL has worked to optimize this thermocouple’s stability. With appropriate heat treatment and fabrication approaches, results indicate that thermal cycling effects on this thermocouple’s calibration is minimized. INL initiated a series of high-temperature (1200 to 1800°C) long-duration (up to 6 months) tests to assess the long-term stability of these thermocouples. Initial results indicate that the INL-developed thermocouple’s thermoelectric response is very stable. Typically, <20°C drift was observed in a 4000-h test at 1200°C. In comparison, commercially available types K and N thermocouples included in these 1200°C tests experienced drifts up to 110°C.

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.

The High-Temperature Electrolysis Integrated Laboratory-Scale Experiment

Abstract The High-Temperature Electrolysis Integrated Laboratory-Scale experiment was designed at the Idaho National Laboratory (INL) and Ceramatec during 2006 and early 2007 and constructed in the spring and summer of 2007. A “half-module,” two stacks of 60 cells each, was tested at Ceramatec for 2040 h in June–September 2006 and a full module, four stacks of 60 cells each, was completed in March 2007. Initial shakedown testing of the INL Integrated Laboratory-Scale (ILS) experimental facility commenced on August 22, 2007. Heatup of the first ILS module started at 4:10 PM on September 24, 2007, and ran for 420 h. The test average H2 production rate was ~1.3 N.m3/h (Normal cubic meters per hour, where Normal conditions are 273 K and 1 atm) (0.116 kg H2/h), with a peak measured H2 production rate of over 2 N.m3/h (0.179 kg H2/h). Significant module performance degradation was observed over the first 250 h, after which no further degradation was noted for the remainder of the test. Once all test objectives had been successfully met, the test was terminated in a controlled fashion.

LDA-Measurements of Transitional Flows Induced by a Square Rib

New fundamental measurements are presented for the transition process in flat plate boundary layers downstream of two-dimensional square ribs. By use of laser Doppler anemometry (LDA) and a large Matched-Index-of-Refraction (MIR) flow system, data for wall-normal fluctuations and Reynolds stresses were obtained in the near wall region to y+<0.1 in addition to the usual mean streamwise velocity component and its fluctuation. By varying velocity and rib height, the experiment investigated the following range of conditions: k+ = 5.5 to 21, 0.3

Comparison Measurements of Silicon Carbide Temperature Monitors

As part of a process initiated through the Advanced Test Reactor (ATR) National Scientific User Facility (NSUF) program to make Silicon Carbide (SiC) temperature monitors available for experiments, a capability was developed at the Idaho National Laboratory (INL) to complete post-irradiation evaluations of these monitors. INL selected the resistance measurement approach for detecting peak irradiation temperature from SiC temperature monitors. To demonstrate this new capability, comparison measurements were completed by INL and Oak Ridge National Laboratory (ORNL) on identical samples subjected to identical irradiation conditions. Results reported in this paper indicate that the resistance measurement approach yields similar peak irradiation temperatures if appropriate equipment is used and appropriate procedures are followed.

Enhanced In-Pile Instrumentation at the Advanced Test Reactor

Many of the sensors deployed at materials and test reactors cannot withstand the high flux/high temperature test conditions often requested by users at U.S. test reactors, such as the Advanced Test Reactor (ATR) at the Idaho National Laboratory. To address this issue, an instrumentation development effort was initiated as part of the ATR National Scientific User Facility in 2007 to support the development and deployment of enhanced in-pile sensors. This paper provides an update on this effort. Specifically, this paper identifies the types of sensors currently available to support in-pile irradiations and those sensors currently available to ATR users. Accomplishments from new sensor technology deployment efforts are highlighted by describing new temperature and thermal conductivity sensors now available to ATR users. Efforts to deploy enhanced in-pile sensors for detecting elongation and real-time flux detectors are also reported, and recently-initiated research to evaluate the viability of advanced technologies to provide enhanced accuracy for measuring key parameters during irradiation testing are noted.

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.

Experimental Modeling of VHTR Plenum Flows during Normal Operation and Pressurized Conduction Cooldown

The Very High Temperature Reactor (VHTR) is the leading candidate for the Next Generation Nuclear Power (NGNP) Project in the U.S. which has the goal of demonstrating the production of emissions free electricity and hydrogen by 2015. The present document addresses experimental modeling of flow and thermal mixing phenomena of importance during normal or reduced power operation and during a loss of forced reactor cooling (pressurized conduction cooldown) scenario. The objectives of the experiments are, 1), provide benchmark data for assessment and improvement of codes proposed for NGNP designs and safety studies, and, 2), obtain a better understanding of related phenomena, behavior and needs. Physical models of VHTR vessel upper and lower plenums which use various working fluids to scale phenomena of interest are described. The models may be used to both simulate natural convection conditions during pressurized conduction cooldown and turbulent lower plenum flow during normal or reduced power operation.

IN-SITU CREEP TESTING CAPABILITY FOR THE ADVANCED TEST REACTOR

An instrumented creep testing capability is being developed for specimens irradiated in pressurized water reactor coolant conditions at the Advanced Test Reactor (ATR). A test rig has been developed such that samples will be subjected to stresses up to 350 MPa at temperatures up to 370°C in pile. Initial Idaho National Laboratory (INL) efforts to develop this creep testing capability for the ATR are summarized. In addition to providing an overview of in-pile creep test capabilities available at other test reactors, this paper reports efforts by the INL to evaluate a prototype test rig in an autoclave at INL’s High Temperature Test Laboratory. Data from autoclave tests with Type 304 stainless steel and copper specimens are reported.

New Sensors for In-Pile Temperature Measurement at the Advanced Test Reactor National Scientific User Facility

Abstract The U.S. Department of Energy designated the Advanced Test Reactor (ATR) a National Scientific User Facility (NSUF) in April 2007 to support U.S. research in nuclear science and technology. As a user facility, the ATR is supporting new users from universities, laboratories, and industry, as they conduct basic and applied nuclear research and development to advance the nation’s energy security needs. A key component of the ATR NSUF effort is to develop and evaluate new in-pile instrumentation techniques that are capable of providing measurements of key parameters during irradiation. This paper describes the strategy for determining what instrumentation is needed and the program for developing new or enhanced sensors that can address these needs. Accomplishments from this program are illustrated by describing new sensors now available and under development for in-pile measurement of temperature at various irradiation locations in the ATR.