The moderator temperature coefficient (MTC) is an important safety parameter in a Pressurized Water Reactor (PWR). It reflects the reactivity feedback of a change in temperature of the water. For safety reasons, this MTC is to be kept negative at all times. An increase in temperature (for example, due to an accidental situation) would hence reduce the reactivity of the core and will lead to a stabilization of the temperature excursion. On the other hand, a reduction of the temperature (over-cooling) would lead to an increase of the reactivity of the core. Reactor operators have to measure the MTC at least twice: once at the beginning of the fuel cycle and once near the end of the cycle. Measurements of MTC near the end of the cycle are difficult. The reactor is then at full power and the conventional measurements all involve a perturbation of the reactor configuration (for example, boron dilution method). Hence the interest of using reactor noise analysis for the MTC measurement. Reactor noise analysis relies on the normally occurring fluctuations of the temperature of the water (moderator) in the reactor and the way this induces neutron fluctuations. Since also other phenomena may cause neutron fluctuations, correlations between temperature and neutron signals in an appropriate frequency window are used to filter for the signals of interest. The motivation to study reactor noise analysis for the determination of MTC is because this method would allow to estimate the MTC on-line (and at any moment during the cycle) without the need to perturb the reactor and hence would allow to constantly monitor this safety parameter. We are currently studying how meaningful neutron noise measurements could be performed using the standard neutron and temperature sensors of the reactor. A key issue in this study is the understanding of the relations between local and global fluctuations of neutron and temperature signals.
|Title of host publication||3rd Strategic Energy Forum, Autoworld Brussels, 16 December 2008|
|Publication status||Published - 16 Dec 2008|
- Pressurized Water Reactor