CLAD TEMPERATURE CONTROL IN LIGHT WATER REACTORS.

It has been found that the control principles used for an electric heater can be applied to controlling the LWR fuel cladding temperature, with proper considerations given to the physical arrangement and operating conditions of the reactor core. A study of the heat-transfer process around an electric heater has led to the idea of an incremental heat transfer coefficient,. A 2 zero/3 poles transfer function was found to represent the dynamics of an LWR fuel element. The temperature control system consists of a bridge circuit and demodulating and amplifying components arranged to provide negative feedback. It was necessary to incorporate a compensating network in the system to obtain stable operation and the desired performance. Work now is under way on a study of the temperature dynamics required to achieve the desired temperature control in an LWR. It is estimated that the proposed clad temperature control system, when perfected, could enable the power level of a reactor to be increased by at least 10%. Thus, a 1000-MWe plant might be increased in power level to 1100 MWe for about 2 million in 1975 dollars.