Assessment of load-following capability of VHTR cogeneration systems

A newly-proposed control system design for the GTHTR300C, a nuclear power and heat cogeneration system employing a Very High Temperature Reactor (VHTR), offering load-following capability is presented. The system is designed to follow significant seasonal variations of electric load demand. It combines several fundamental control methods including inventory control used to adjust primary coolant pressure, flow bypass control used to regulate the coolant flow rate and turbine inlet temperature, and additional flow control to vary the IHX heat rate. The goal of the control system design is such that the wide range of load-following capability can be performed at constant reactor power and thermal efficiency, which maximizes plant economics, while minimizing transient thermal stresses in the reactor equipment. The control simulation of a representative load-following operation is carried out using a system analysis code and discussed in the paper. The results of the simulation show that the design goal can be effectively met by monitoring and controlling constant a few selected operating parameters of reactor and gas turbine including reactor outlet temperature, turbine inlet temperature and speed. The original control system design shows that load-following operation at constant reactor power and thermal efficiency by a VHTR power and heat cogeneration system is feasible.

► A control scheme of electric load-following operation for VHTR cogeneration system is proposed.
► The control integrates inventory, reactor bypass flow and secondary loop flow rate controls.
► The scheme enables load-following with constant reactor power and power generation efficiency.