Reactor-turbine control for low steam pressure operation in a pressurized water reactor

A control system for a nuclear steam turbine power plant having a pressurized water reactor element and a steam generator element supplying a flow of pressurized steam to a closed loop turbine arrangement, said closed loop turbine arrangement having a high pressure turbine element and a low pressure turbine element, said control system comprising:

• temperature sensing means for monitoring the temperature levels within said nuclear reactor, and,
• flow interruption means for diverting a portion of said flow of pressurized steam in response to a predetermined signal from said temperature sensing means, said flow interruption means comprising a valve member disposed in a conduit bypassing said high pressure turbine element, said flow interruption means opening said valve member in response to said predetermined signal from said temperature sensing means to conduct said flow of pressurized steam from said steam generator element through said bypass conduit directly into said low pressure turbine element, bypassing said high pressure turbine element.

A method for extending operation of a pressurized water reactor power plant beyond the end of a predetermined fuel cycle, the plant having a reactor element having a predetermined reactivity level therein, the plant having a turbine loop with a predetermined motive fluid flow rate therein associated with said reactor, the turbine loop including a high pressure turbine element passing a predetermined flow rate and a low pressure turbine element passing a greater predetermined flow rate, said method comprising the steps of:

• changing said reactivity level in said reactor element from said predetermined level to another predetermined level and,
• modifying the flow rate in said turbine loop to compensate for the change in reactivity level in said reactor by bypassing said high pressure turbine element.

A method for extending operation of a pressurized water reactor power plant having a first closed reactor loop and a second closed turbine loop having a motive fluid therein beyond the end of a predetermined fuel cycle, said reactor loop having a pressurized water reactor element with a first predetermined reactivity level therein, said method comprising the steps:

• changing said reactivity level in said reactor element from said first predetermined level to a second predetermined level to change the pressure of the motive fluid within said turbine loop, and,
• modifying said turbine loop by diverting said motive fluid flow therein to compensate for said change in motive fluid pressure generated by said change in said reactivity level within said reactor element.