Determination of the Specific Heat Transfer Between Fuel and Canning from Reactivity Measurements at the Nuclear Pow er Plant KCB

The reactivity transient following a control rod step strongly depends on quantities that determine the thermal reactivity feedback. For the special case of a pressurized water reactor, these quantities are the reactivity temperature coefficients and the heat transfer between fuel and coolant. Therefore, it is possible to determine these quantities by fitting appropriate model calculations to measured reactivity transients. This so-called “rod step method” was extensively applied for the first time in the first cycle of the nuclear power plant KCB at Borssele in the Netherlands. The values of the heat transfer between fuel and coolant and those of the fuel temperature coefficient that are obtained by this method agree well with the theoretically expected behavior with increasing core burnup.