Hello please share information about any accidents/incidents related to the misreadings/malfunctioning/wrong interpretation of ex-core detectors ( for any reasons) I searched and found one incident of Calvert-Cliff Nuclear power plant in 1988. LINK. (Page 2, at Clueless at Calvert Cliffs ) Though it is very old and doesn't entitle for malfunctioning of detector, but it is important to analyze, as the power measurement at higher level is based on ex-core detector. The detector need not be malfunctioned necessarily. But any wrong readings from it has a serious consequence. Thanks.