Thermocouples for High-Temperature In-Pile Testing

Abstract

INTRODUCTIONMany advanced nuclear reactor designs require new fuel, cladding, and structural materials. Data are needed to characterize the performance of these new materials in high temperature, oxidizing, and radiation conditions. To obtain this data, robust instrumentation is needed that can survive proposed test conditions. Traditional methods for measuring temperature in-pile degrade at temperatures above 1080 ºC. Hence, a project was initiated to develop specialized thermocouples for high temperature in-pile applications (see Rempe and Wilkins, 2005). This paper summarizes efforts to develop, fabricate, and evaluate these specialized thermocouples. BACKGROUND

TMI-2 - A Case Study for PWR Instrumentation Performance during a Severe Accident

“…In general, Type K thermocouple evaluations indicate that significant decalibration may occur at temperatures greater than 1100°C. 55 After cooldown, tests found that open circuit thermocouples can reform physical junctions, but data from such junctions are questionable due to their unknown location, changes in the metallurgical properties, changes in the chemical composition of thermoelement wires, and insulation degradation. Thermocouple loop resistance measurements were made to infer the location of core damage by the location where virtual junctions formed in the thermocouples.…”

Enhancements to High Temperature In-Pile Thermocouple Performance

“…Task 1. 3 Longer duration higher temperature tests to assess the impact of alternate alloys on thermocouple reliability. Based on the results of these evaluations, recommendations were formulated with respect to materials and heat treatments for optimizing thermocouple performance.…”

Assessment of High-Temperature Measurements for Use in the Gas Test Loop

“…The classic method uses the addition of small quantities of silicon, tungsten, and potassium, and recent efforts rely on the addition of lanthanum oxide. Recent work at the INL [36] showed undoped Mo to be brittle in mandrel-wrap tests after 30 minutes at 1300˚C in argon, and Mo wires doped by both of the above techniques were still ductile after 30 minutes at 1600˚C when wrapped on a mandrel of twice the wire diameter. In continuing work, mandrel-wrap tests performed on 0.010 inch-diameter.…”