  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.
