Current generation water-cooled Nuclear Power Plants (NPPs) have significantly lower thermal efficiencies than their thermal counterparts; due, partially, to their lower turbine-inlet steam temperature. Nuclear steam superheat can be implemented in a generic pressure-channel nuclear reactor to increase the temperature of the steam at the inlet of the turbine, and thus increase the thermal efficiency of a NPP.
A heat flux is computed specifically for a stable SuperHeated Steam (SHS) and Pressurized Water (PW) 520 pressure-channel reactor core configuration, from which a unique temperature profile for each coolant (as a bulk fluid) is calculated. Using the coolant temperature profile of each coolant, the sheath temperature distribution is calculated, using Fourier’s law, and the fuel pellets’ axial and radial temperature profiles are determined using an analytical solution to the temperature distribution in a solid with uniform heat generation.
Properties of the coolant, sheath, and fuel were calculated based on the temperature (and pressure, in the case of coolant) along the heated length of a channel. The effects on the flow rates and the differences in the required channel powers, due to the addition of the SHS channels, were also considered. To ensure safe operating parameters, the maximum sheath and fuel centerline temperatures were shown to be much lower than the operating limits.
The implementation of steam superheat in a generic 1200-MWel pressure-channel nuclear reactor allows for an increase in the temperature of steam at the inlet of a turbine from ∼319°C to ∼550°C, and ultimately an increase in the thermal efficiency of the NPP by about 5–7%.
