Development of BWR Power Uprate Method Based on “Heat Balance Shift” Concept

We have developed an innovative power uprate method for boiling water reactors (BWRs) that will increase thermal power by more than 5% without having to replace the high-pressure turbine. Reactor power uprate of nuclear power plants is an efficient plant operating method. Most BWR plants need to replace high-pressure turbines when thermal power is increased to over 5% because the main steam flow rate exceeds the inlet steam flow rate limit of the high-pressure turbine. A conventional power uprate method increases the feedwater and main steam flow rate in proportion to increase in thermal power. We examined a decrease in feedwater temperature instead of an increase in the feedwater and main steam flow rate. Since a decrease in feedwater temperature leads to a smaller main steam flow rate, a power uprate of over 5% can be achieved without replacing the high-pressure turbine. We call this power uprate method the “heat balance shift” method. In the present study, we evaluated the heat balance shift method to determine if it can increase electric power to a level higher than that of the conventional power uprate method without replacing the high-pressure turbine.