Computational-Experimental Investigation of a Fission Thermal Probe in TREAT

Abstract

The development of nuclear fuels requires unsteady/transient testing for design process and qualification under postulated accident conditions. Breach, rupture, fracture, melting, and other fuel failure modes may occur during the use of nuclear fuels or when they are exposed to extreme overpower conditions. Therefore, it is crucial for the fuel to retain reasonable structural integrity and coolable geometry. The experimental facility of Transient Reactor Test (TREAT) was designed and constructed in November 1958 to conduct transient testing of fuels and structural materials. The magnitude of nuclear heating is one of the most important key parameters in test design, analysis, and data interpretation in TREAT. Some steady-state tests are able to measure heating directly via enthalpy rise of coolant in thermally-isolated loops, but an enormous number of important tests must rely upon nuclear modeling to correlate core operating parameters to specimen nuclear heating. Uncertainties of these models and their inputs can prevent experimenters from achieving desired conditions and hamper advanced models from describing the phenomena to the level of confidence needed. The situation can be even more difficult for unsteady/transient tests where nuclear heating is intentionally varied over short time scales. This research develops a novel nuclear heating sensor technology which directly measures the parameters of interest using spatially-resolved real-time thermometry of fissionable instrument materials, demonstrate the instruments' use in TREAT, and perform data comparisons to nuclear models to facilitate an advanced understanding of transient power coupling. Here we present our results of the designed probe and its testing outcome.