Date of Award:
Master of Science (MS)
Mechanical and Aerospace Engineering
Thermal conductivity is an important thermophysical property needed for effectively predicting fuel performance. As part of the Next Generation Nuclear Plant (NGNP) program, the thermal conductivity of tri-isotropic (TRISO) fuel needs to be measured over a temperature range characteristic of its usage. The composite nature of TRISO fuel requires that measurement be performed over the entire length of the compact in a non-destructive manner. No existing measurement system is capable of performing such a measurement.
A measurement system has been designed based on the steady-state, guarded-comparative-longitudinal heat flow technique. The system as currently designed is capable of measuring cylindrical samples with diameters ~12.3-mm (~0.5″) with lengths ~25-mm (~1″). The system is currently operable in a temperature range of 400 K to 1100 K for materials with thermal conductivities on the order of 10 W/m/K to 70 W/m/K. The system has been designed, built, and tested. An uncertainty analysis for the determinate errors of the system has been performed finding a result of 5.5%. Finite element modeling of the system measurement method has also been accomplished demonstrating optimal design, operating conditions, and associated bias error.
Measurements have been performed on three calibration/validation materials: SS304, 99.95% pure iron, and inconel 625. In addition, NGNP graphite with ZrO2 particles and NGNP AGR-2 graphite matrix only, both in compact form, have been measured. Results from the SS304 sample show agreement of better than 3% for a 300–600°C temperature range. For iron between 100–600°C, the difference with published values is < 8% for all temperatures. The maximum difference from published data for inconel 625 is 5.8%, near 600°C. Both NGNP samples were measured from 100–800°C. All results are presented and discussed.
Finally, a discussion of ongoing work is included as well as a brief discussion of implementation under other operating conditions, including higher temperatures and adaptation for use in a glovebox or hot cell.
Jensen, Colby, "TRISO Fuel Compact Thermal Conductivity Measurement Instrument Development" (2010). All Graduate Theses and Dissertations. 838.
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