Measurements of the fuel temperature coefficient of reactivity at Hinkley Point 'B': 1981

Measurements of the fuel temperature coefficient of reactivity made at Hinkley Point 'B' AGR in 1981 are described. These measurements follow earlier tests reported in e.g. RD/B/N4846 and are part of a series of measurements designed to support theoretical estimates of the change of fuel temperature coefficient as a function of core irradiation. Low and high power measurements were made at a mean core irradiation of 1170GWD. As previously, the measurements at both power levels show agreement with theoretical predictions to within the estimated experimental errors. Recent measurements (mean core irradiation >500GWD) show evidence of a small systematic difference between measured and theoretical values with the experimental values being approximately equal to 0.1mN/0C more positive than the theoretical ones. The measured value of αsub(U) at high power was -0.64+-0.10mN/0C and the low power value, corrected theoretically to normal operating conditions, was also -0.64+-0.10mN/0C. (author)