THERMAL BEHAVIOUR CORRELATION FOR THERMAL COLUMN IN THE NATIONAL RESEARCH UNIVERSAL (NRU) REACTOR

The National Research Universal (NRU) reactor is a major research facility that provides a beam of slow neutrons with a minimum of gamma rays and other types of radiation for experimental purposes. The thermal column consists of 5 graphite radial sections separated with an air gap for cooling. The graphite components require continuous monitoring to ascertain that temperatures are controlled within safe margins. Wall temperatures of the graphite sections are obtained via thermocouples affixed to the column walls. The safety margins for operation of the thermal column are driven by the temperatures of the closest radial section to the reactor core (HG1). Although, most of the thermocouples in HG1 are no longer functional, the thermocouples are functional in the adjacent graphite section (HG2). This study relied on the historical data of the graphite temperatures over a few years to develop an empirical correlation that relates temperatures in HG1 to those of HG2. The correlation sets limits on the functional thermocouples in HG2 to ensure HG1 remains within the prescribed limits (149–232 °C). Correlations were developed using statistical analysis of the historical data. A control band of approximately 40 °C for HG2 with confidence levels of 68% and 95%, respectively, were established.