Efforts to eliminate plant transient: End-of-life moderator temperature coefficient measurement

The response of the reactor core to changing plant conditions is determined by its kinetic characteristics. These characteristics are quantified through the use of reactivity coefficients that reflect changes in core neutron population. The moderator temperature coefficient (MTC) of reactivity is defined as the change in reactivity per unit change in the moderator temperature. It is an important reactor parameter in pressurized water reactors. It is monitored to ensure the plant operates within the limits assumed in the plant safety analysis. Because the value of the MTC varies over the fuel cycle, it must be measured initially at zero power to verify core design and at nominal power levels at end of life when there is a concern that a main steam line rupture and the ensuing primary-side cooldown might result in an undesirable power excursion. Duke Power Company, in conjunction with the Electric Power Research Institute and Virginia Polytechnic Institute, is working to develop a new method of monitoring the MTC at power using neutron noise analysis techniques. If successful, the final result of this program will be the development of a new method of calculating the MTC at any point in core life that does not induce a plant transient. This project is to be completed by March 1990