Sub-critical moderator temperature reactivity coefficient: measurement at Edwin I. Hatch unit 2 BWR nuclear power plant

In order to qualify the PATRC code, data were collected from the Edwin I. Hatch Unit 2 (Cycle 16) BWR nuclear power plant using the standard core monitoring system. By matching control rod position vs. time two periods of time were noted where there were no control rod movements, yet there was a coincidental decrease of the average source range detector reading simultaneously with an increase of the reactor moderator temperature. By evaluating the data, sub-critical moderator temperature coefficients were obtained which compared well with PATRC calculations performed in this report. By reproducing similar reactor conditions during the start-up of future cycles, the moderator temperature coefficient can be determined before achieving criticality, such information can be valuable for reactor operators.