Comparison of Measured and Predicted Sensitivities of In-Core Flux Detectors

Abstract

In-core flux detectors (ICFDs), also known as self-powered neutron detectors, are key elements in CANDU reactor control and safety. One of the key performance characteristics of ICFDs is their sensitivity, which changes with burnup of the current-producing materials in the detector. Sensitivity measurements on thirteen Straight Individually Replaceable (SIR) ICFDs that were irradiated in NRU for over 10 years showed some significant discrepancies with the predictions. As well, a study of the change of sensitivity of platinum-coiled detectors from Bruce A and Pickering B shows that these detectors are not burning up as fast as expected.