[en] Pressurised Heavy Water Reactors (PHWR) are channel type reactors and a typical reactor is having more than 300 channels with two temperature measurements per channel. In certain cases, degradation of the channel temperature monitoring sensors has been reported. These degradations results in availability factor of the reactors. Thus, root cause analysis for the sensor degradation has been carried out. Further, in order to ascertain no degradations in the future, certain improvements are suggested in the sensor design. This paper elaborates the nature of the degradations, root cause for the degradations and suggested modifications based on the analysis in order to improve reliability of the measurements. (author)