Ultrasonic Thermometry for In-Pile Temperature Detection

Conference · Fri Nov 01 00:00:00 EST 2002

OSTI ID:1004265

Daw, J E; Rempe, J L; Wilkins, S C

The Idaho National Laboratory has recently initiated a new effort to evaluate the viability of using ultrasonic thermometry technology as an improved sensor for detecting temperature during irradiation testing. Ultrasonic thermometers (UTs) work on the principle that the speed at which sound travels through a material (acoustic velocity) is dependant on the temperature of the material. By introducing an acoustic pulse to the sensor and measuring the time delay of echoes, temperature may be derived. UTs have several advantages over other sensor types. UTs can be made very small, as the sensor consists only of a small diameter rod which may or may not require a sheath. Measurements may be made near the melting point of the sensor material, as no electrical insulation is required; and shunting effects are avoided. Most attractive, however, is the ability to introduce acoustic discontinuities to the sensor, as this enables temperature measurements at several points along the sensor length (allowing temperature profiling with a single sensor). A typical multi-sensor UT system, with key components identified, is shown in Figure 1. As indicated in this figure, a narrow ultrasonic pulse is generated in a magnetostrictive rod by an excitation coil. The ultrasonic pulse propagates to the sensor wire, where a fraction of the pulse energy is reflected at each discontinuity (notches or diameter change). Each reflected pulse is received by the excitation coil, transformed into an electrical signal, amplified and evaluated in a start/stop counter system. The time interval between two adjacent echoes is evaluated and compared to a calibration curve to give the average temperature in the corresponding sensor segment. When a number of notches are available on the wire sensor, the various measurements give access to a temperature profile along the probe. UTs have been used successfully for several applications; however, several problems have limited the success of these sensors. For example, signal processing can be very complicated, as multiple echoes may overlap. Contact between the sensor and solid materials can cause extraneous echoes. If a sheath is required, contact bonding at high temperatures may cause extraneous echoes or attenuation of primary echoes. The most successful materials used in previous studies, tungsten and rhenium, are unattractive for nuclear applications due to material transmutation. Clearly, in order for ultrasonic thermometers to be viable for an in-pile sensor, these issues must be resolved through the use of modern signal processing and materials technologies. As part of the INL feasibility study, all of the issues associated with UT use and proposed resolution options will be identified and evaluated. Once most promising options are proven, it is planned to produce one or more prototype ultrasonic temperature sensors for evaluation. Ultimately, a full test should include a long term installation in a high temperature test assembly installed in a high neutron flux environment, such as that found in the Idaho National Laboratory’s Advanced Test Reactor.

• Research Organization: Idaho National Lab. (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: DOE - NE
• DOE Contract Number: DE-AC07-05ID14517
• OSTI ID: 1004265
• Report Number(s): INL/CON-10-18293; TRN: US1100646
• Resource Relation: Conference: NPIC and HMIT 2010,Las Vegas, Nevada, USA,11/07/2010,11/11/2010
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ACOUSTICS
ATTENUATION
BONDING
CALIBRATION
DETECTION
ELECTRICAL INSULATION
EXCITATION
IRRADIATION
MELTING POINTS
NEUTRON FLUX
RESOLUTION
RHENIUM
TEMPERATURE MEASUREMENT
TEST REACTORS
TIME DELAY
TRANSMUTATION
TUNGSTEN
ULTRASONIC WAVES
High Temperature
Ultrasonic Thermometry