Operation method of nuclear power plant

1. An operation method of a nuclear power plant comprising:

a nuclear reactor;

a high pressure steam system supplied with steam generated in said nuclear reactor and extending from an outlet of said nuclear reactor to an inlet of a low pressure turbine via a high pressure turbine;

a low pressure steam system extending from the inlet of said low pressure turbine to an inlet of a condenser for condensing the steam discharged from said low pressure turbine; and

a feedwater system including a feedwater heater for heating feedwater supplied from said condenser and introducing the feedwater discharged from said feedwater heater to said nuclear reactor, the operation method comprising the steps of:

uprating second nuclear thermal power in a second operation cycle of said nuclear reactor from first nuclear thermal power in a first operation cycle before the second operation cycle; and

reducing a proportion of a mass flow rate of steam extracted from said high pressure steam system and introduced to said feedwater heater in the second operation cycle with respect to a mass flow rate of main steam at the outlet of said nuclear reactor in comparison with a proportion of a mass flow rate of steam extracted from said high pressure steam system and introduced to said feedwater heater in the first operation cycle with respect to the mass flow rate of main steam at the outlet of said nuclear reactor, such that temperature of the feedwater discharged from said feedwater heater lowers in the range of 1° C. to 40° C. in the second operation cycle from the feedwater temperature in the first operation cycle.

2. An operation method of a nuclear power plant comprising:

a nuclear reactor;

a high pressure steam system supplied with steam generated in said nuclear reactor and extending from an outlet of said nuclear reactor to an inlet of a low pressure turbine via a high pressure turbine;

a low pressure steam system extending from the inlet of said low pressure turbine to an inlet of a condenser for condensing the steam discharged from said low pressure turbine; and

a feedwater system including a feedwater heater for heating feedwater supplied from said condenser and introducing the feedwater discharged from said feedwater heater to said nuclear reactor, the operation method comprising the steps of:

uprating second nuclear thermal power in a second operation cycle of said nuclear reactor from first nuclear thermal power in a first operation cycle before the second operation cycle; and

reducing a proportion of a mass flow rate of steam extracted from each of said high pressure steam system and said low pressure steam system and introduced to said feedwater heater in the second operation cycle with respect to a mass flow rate of main steam at the outlet of said nuclear reactor in comparison with a proportion of a mass flow rate of steam extracted from each of said high pressure steam system and said low pressure steam system and introduced to said feedwater heater in the first operation cycle with respect to the mass flow rate of main steam at the outlet of said nuclear reactor, and setting a decrease of the proportion of the mass flow rate of steam extracted from said high pressure steam system in the second operation cycle with respect to the mass flow rate of main steam at the outlet of said nuclear reactor from the proportion in the first operation cycle to be larger than a decrease of the proportion of the mass flow rate of steam extracted from said low pressure steam system in the second operation cycle with respect to the mass flow rate of main steam at the outlet of said nuclear reactor from the proportion in the first operation cycle, such that temperature of the feedwater discharged from said feedwater heater lowers in the range of 1° C. to 40° C. in the second operation cycle from the feedwater temperature in the first operation cycle.

3. An operation method of a nuclear power plant comprising:

a nuclear reactor;

a high pressure steam system supplied with steam generated in said nuclear reactor and extending from an outlet of said nuclear reactor to an inlet of a low pressure turbine via a high pressure turbine;

a low pressure steam system extending from the inlet of said low pressure turbine to an inlet of a condenser for condensing the steam discharged from said low pressure turbine; and

a feedwater system including a feedwater heater for heating feedwater supplied from said condenser and introducing the feedwater discharged from said feedwater heater to said nuclear reactor, the operation method comprising the steps of:

uprating second nuclear thermal power in a second operation cycle of said nuclear reactor from first nuclear thermal power in a first operation cycle before the second operation cycle; and

reducing a mass flow rate of steam extracted from said high pressure steam system and introduced to said feedwater heater in the second operation cycle in comparison with a proportion of a mass flow rate of steam extracted from said high pressure steam system and introduced to said feedwater heater in the first operation cycle, such that temperature of the feedwater discharged from said feedwater heater lowers in the range of 1° C. to 40° C. in the second operation cycle from the feedwater temperature in the first operation cycle.

4. An operation method of a nuclear power plant comprising:

a nuclear reactor;

a high pressure steam system supplied with steam generated in said nuclear reactor and extending from an outlet of said nuclear reactor to an inlet of a low pressure turbine via a high pressure turbine;

a low pressure steam system extending from the inlet of said low pressure turbine to an inlet of a condenser for condensing the steam discharged from said low pressure turbine; and

a feedwater system including a feedwater heater for heating feedwater supplied from said condenser and introducing the feedwater discharged from said feedwater heater to said nuclear reactor, the operation method comprising the steps of:

uprating second nuclear thermal power in a second operation cycle of said nuclear reactor from first nuclear thermal power in a first operation cycle before the second operation cycle; and

reducing a mass flow rate of steam extracted from each of said high pressure steam system and said low pressure steam system and introduced to said feedwater heater in the second operation cycle in comparison with a proportion of a mass flow rate of steam extracted from each of said high pressure steam system and said low pressure steam system and introduced to said feedwater heater in the first operation cycle, and setting a decrease of the mass flow rate of steam extracted from said high pressure steam system in the second operation cycle from the mass flow rate of the extracted steam in the first operation cycle to be larger than a decrease of the mass flow rate of steam extracted from said low pressure steam system in the second operation cycle from the mass flow rate of the extracted steam in the first operation cycle, such that temperature of the feedwater discharged from said feedwater heater lowers in the range of 1° C. to 40° C. in the second operation cycle from the feedwater temperature in the first operation cycle.

5. An operation method of a nuclear power plant comprising:

a nuclear reactor;

a steam system including a high pressure steam system and a low pressure steam system, which are supplied with steam generated in said nuclear reactor;

a condenser for condensing the steam discharged from said low pressure turbine; and

a feedwater system including a low pressure feedwater heater installed downstream of said condenser and upstream of a main feedwater pump and heating the feedwater supplied from said condenser, and a high pressure feedwater heater installed downstream of said main feedwater pump and upstream of the nuclear reactor and introducing the feedwater discharged from said high pressure feedwater heater to said nuclear reactor, the operation method comprising the steps of:

uprating second nuclear thermal power in a second operation cycle of said nuclear reactor from first nuclear thermal power in a first operation cycle before the second operation cycle; and

reducing a temperature rise obtained by said high pressure feedwater heater in the second operation cycle in comparison with a temperature rise obtained by said high pressure feedwater heater in the first operation cycle, such that temperature of the feedwater discharged from said high pressure feedwater heater lowers in the range of 1° C. to 40° C. in the second operation cycle from the feedwater temperature in the first operation cycle.

6. An operation method of a nuclear power plant comprising:

a nuclear reactor;

a steam system including a high pressure steam system and a low pressure steam system, which are supplied with steam generated in said nuclear reactor;

a condenser for condensing the steam discharged from said low pressure turbine; and

a feedwater system including a low pressure feedwater heater installed downstream of said condenser and upstream of a main feedwater pump and heating the feedwater supplied from said condenser, and a high pressure feedwater heater installed downstream of said main feedwater pump and upstream of the nuclear reactor and introducing the feedwater discharged from said high pressure feedwater heater to said nuclear reactor, the operation method comprising the steps of:

uprating second nuclear thermal power in a second operation cycle of said nuclear reactor from first nuclear thermal power in a first operation cycle before the second operation cycle; and

reducing a proportion of a temperature rise obtained by said high pressure feedwater heater in the second operation cycle with respect to a total temperature rise obtained by said high pressure feedwater heater and said low pressure feedwater heater in comparison with a proportion of a temperature rise obtained by said high pressure feedwater heater in the first operation cycle with respect to the total temperature rise obtained by said high pressure feedwater heater and said low pressure feedwater heater, such that temperature of the feedwater discharged from said high pressure feedwater heater lowers in the range of 1° C. to 40° C. in the second operation cycle from the feedwater temperature in the first operation cycle.

7. An operation method of a nuclear power plant comprising:

a nuclear reactor;

a steam system including a high pressure steam system and a low pressure steam system, which are supplied with steam generated in said nuclear reactor, said steam system further including at least one of a moisture separator, a moisture separator and heater, and a moisture separator and reheater between said high pressure steam system and said low pressure steam system;

a condenser for condensing the steam discharged from said low pressure turbine; and

a feedwater system including a pressure feedwater heater for heating the feedwater supplied from said condenser and introducing the feedwater discharged from said feedwater heater to said nuclear reactor; and

at least one high pressure extraction line for extracting steam from an intermediate point of said high pressure turbine and a point downstream of an outlet of said high pressure turbine and upstream of an inlet of one of said moisture separator, said moisture separator and heater, and said moisture separator and reheater, and for introducing the extracted steam to said feedwater heater, the operation method comprising the steps of:

uprating second nuclear thermal power in a second operation cycle of said nuclear reactor from first nuclear thermal power in a first operation cycle before the second operation cycle; and

in said at least one high pressure extraction line through which the extracted steam flows in the first operation cycle, stopping the flow of the extracted steam in the second operation cycle or adjusting a flow rate of the extracted steam in the second operation cycle by extracted flow adjusting means disposed in said at least one high pressure extraction line, such that temperature of the feedwater discharged from said feedwater heater lowers in the range of 1° C. to 40° C. in the second operation cycle from the feedwater temperature in the first operation cycle.

8. An operation method of a nuclear power plant comprising:

a steam system including a high pressure turbine supplied with steam generated by heat of a nuclear reactor and a lower pressure turbine for introducing the steam discharged from said high pressure turbine;

a condenser for condensing the steam discharged from said low pressure turbine;

a feedwater system including a feedwater heater for heating feedwater supplied from said condenser and introducing the feedwater discharged from said feedwater heater to said nuclear reactor; and

a feedwater heater bypassing line for extracting a part of the feedwater from an intermediate point of the feedwater system and returning the extracted feedwater to said feedwater system after bypassing at least one unit of said feedwater heater, the operation method comprising the steps of:

uprating second nuclear thermal power in a second operation cycle of said nuclear reactor from first nuclear thermal power in a first operation cycle before the second operation cycle; and

lowering temperature of the feedwater discharged from said feedwater heater in the range of 1° C. to 40° C. in the second operation cycle from the feedwater temperature in the first operation cycle.

9. The operation method of the nuclear power plant according to claim 1 , wherein the following formulae are satisfied;

0<A≦5, and

T 2≦ T 1−7.7×( Q 2− Q 1)/(4.5 ×W )

where temperature of the feedwater discharged from said feedwater heater in the first operation cycle is T 1 (° C.), temperature of the feedwater discharged from said feedwater heater in the second operation cycle is T 2 (° C.), core thermal power of said nuclear reactor in the first operation cycle is Q 1 (KW), core thermal power of said nuclear reactor in the second operation cycle is Q 2 (kW), a core flow rate of said nuclear reactor in the second operation cycle is W (kg/s), and a rate of the power uprate is A (%).

10. The operation method of the nuclear power plant according to claim 1 , wherein the following formulae are satisfied;

5<A≦10, and

T 2≦ T 1−7.7×( Q 2×( A+ 95)/100− Q 1)/(4.5 ×W )

where temperature of the feedwater discharged from said feedwater heater in the first operation cycle is T 1 (° C.), temperature of the feedwater discharged from said feedwater heater in the second operation cycle is T 2 (° C.), core thermal power of said nuclear reactor in the first operation cycle is Q 1 (kW), core thermal power of said nuclear reactor in the second operation cycle is Q 2 (kW), a core flow rate of said nuclear reactor in the second operation cycle is W (kg/s), and a rate of the power uprate is A (%).

11. The operation method of the nuclear power plant according to claim 1 , wherein the following formulae are satisfied;

10<A<30, and

T 2≦ T 1−7.7×( Q 2×( A+ 90)/100− Q 1)/(4.5 ×W )

where temperature of the feedwater discharged from said feedwater heater in the first operation cycle is T 1 (° C.), temperature of the feedwater discharged from said feedwater heater in the second operation cycle is T 2 (° C.), core thermal power of said nuclear reactor in the first operation cycle is Q 1 (kW), core thermal power of said nuclear reactor in the second operation cycle is Q 2 (kW), a core flow rate of said nuclear reactor in the second operation cycle is W (kgls), and a rate of the power uprate is A (%).

12. The operation method of the nuclear power plant according to claim 1 , wherein the first operation cycle is an operation cycle that is performed for the first time after installation of said nuclear power plant, the second operation cycle is an operation cycle after the first operation cycle, and at least one operation cycle is interposed between the first operation cycle and the second operation cycle.