Evidence for a Time-Dependent Neutron Flux/Spectrum Anomaly at the Transient Reactor Test Facility

An anomalous, transient increase in signals from a test fuel pin was detected by the Los Alamos National Laboratory Pinhole Experiment system during an experiment at the Transient Reactor Test Facility. The high resolution image data show that the anomalous increase is definitely not related to internal fuel motion, but appears to correlate with the motion of a transient control rod and related effects. The significance of this observation lies in the effect's magnitude and in the potential for misinterpretation of such an effect as fuel motion within the test capsule, an issue of primary concern in reactor safety studies.