JPS63221293A - Decay-heat removal device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a reactor decay heat removal device using a sodium-heated steam generator in a fast breeder reactor power plant.

(Prior Art) A nuclear power plant is provided with a decay heat removal device for removing core decay heat after the nuclear reactor is shut down. There are various types and system configurations of decay heat removal equipment, and one type uses a steam generator.

A typical decay heat removal device using a steam generator will be explained with reference to FIGS. 2 and 3.

FIG. 2 is a system diagram of a nuclear power plant equipped with a recirculating steam generator. In this figure, the coolant whose temperature has been raised by the thermal energy generated in the reactor 1 is transferred to the intermediate heat exchanger 2.
There, the intermediate heat medium exchanges heat with the intermediate heat medium, and the heated intermediate heat medium is transferred to the evaporator 3 and superheater 4. On the other hand, water in the water/steam system exchanges heat with the intermediate heat medium in the evaporator 3 to become a two-phase stream of steam and water, and flows into the steam drum 5. This two-phase flow is separated here into saturated steam and saturated water.

The saturated water is mixed with the feed water from the high-pressure feed water heater 6 and returned to the evaporator 3, and the saturated steam is sent to the superheater 4 to become superheated steam and sent to the steam turbine 7. The steam that has done work in the steam turbine 7 is condensed in a condenser 8, and this condensate is superheated in a low-pressure feedwater heater 9, degassed in a deaerator 1o, and passed through the low-pressure feedwater heater 6 to steam. It is injected into drum 5.

In the figure, 11 is a primary cooling system main circulation pump, 12 is a condensate pump, 13 is a water supply pump, 14 is a steam recirculation pump, and 15 is a secondary cooling system main circulation pump.

16 indicates a generator, respectively.

In the conventional nuclear power plant with the above configuration, even if the recirculation pump is stopped after the reactor is shut down, there is natural circulation from the steam drum 5 to the steam generator 3 to the steam drum 5, so a stable state is maintained. Heat is removed. Moreover, in this case, the final settling temperature becomes the saturation temperature according to the pressure of the steam drum 5, so the temperature drop from the reactor operating temperature is kept small, and the thermal shock to each equipment is alleviated. This will ensure structural integrity.

However, the nuclear power plant with the above configuration requires a steam drum 5 and a recirculation pump, and also has the disadvantage that it requires a larger heat transfer area than the once-through steam generator described later due to thermal balance conditions. .

FIG. 3, in which the same parts as in FIG. 2 are given the same reference numerals, is a system diagram of a nuclear power plant equipped with a once-through steam generator. In this nuclear power plant, the steam generator 3, superheater 4. In place of the steam drum 5, an integral once-through steam generator 17 is installed. In this integrated once-through steam generator 17, the high pressure feed water heater 6
The water supplied from the water/steam system becomes superheated steam by the time it exits the integrated once-through steam generator 17, and then flows into the steam turbine 16.
is supplied to

A power plant with this configuration has simplified equipment compared to the power plant shown in Figure 2, which is equipped with a recirculating steam generator.
Moreover, since the required heat transfer area is small, it is economically advantageous.

However, for stable operation of an integrated once-through steam generator, there is a limit to the lower limit of the flow rate of the water/steam system, and this limit value is generally much larger than the value required for decay heat removal operation. The operational advantages described above for circulating steam generators cannot be obtained.

(Problems to be Solved by the Invention) As mentioned above, the recirculation type and integrated once-through type generators each have their own merits and demerits. However, there are some unsatisfactory points in ensuring stable operation.

The present invention has been made based on the above-mentioned circumstances, and provides a decay heat removal device that can ensure stable operation during decay heat removal operation while maintaining the economic efficiency that is an advantage of the once-through type generator. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) The decay heat removal device of the present invention includes a once-through steam generator and a steam generator capacity of 11 in the piping leading from the outlet of the once-through steam generator to the steam turbine. A steam-water separator is installed upstream of the valve, and the gas phase is communicated through the vessel inlet stop valve, and upstream of the main water supply control valve of the piping from the deaerator to the steam generator via the steam-water separator water level control valve. In addition, a steam separator having a liquid phase communicated with the inlet side of the steam generator via a check valve, and a pipe connecting the gas phase of the steam separator and the deaerator of the deaerator are installed. a deaerator heating control valve, a main steam atmosphere release valve provided upstream of the deaerator heating control valve, and a steam/water separator provided in a pipe communicating the deaerator and the steam/water separator during standby. During normal operation, the steam separator inlet stop valve is closed to isolate it from the main steam circuit, and after the reactor is shut down when the condenser can be used, the steam After reactor shutdown when the condenser is unusable, the separator inlet stop valve is opened and the steam generator outlet stop valve is closed to generate natural circulation through the steam separator and steam generator to remove heat. In this case, the steam separator pressure control valve is closed, the steam separator inlet stop valve is opened, and the steam generator outlet stop valve is closed, and the water in the steam separator is converted into steam by the steam generator while heat is removed. It is characterized by being made to do.

(Function) In the decay heat removal apparatus of the present invention having the above configuration, by operating the various valves described above, the steam separator can be cut off from the main steam circuit, and the natural circulation of water through the steam water separator and the steam generator can be stopped. The decay heat can be removed by generating heat, or the water retained in the steam-water separator can be sent to the steam generator and the heat can be removed for a short time by evaporation. During normal operation of the nuclear reactor, the steam generator operates as an integral once-through type, so the required heat transfer area is small.

(Example) The same parts as in Figs. 2 and 3 are given the same reference numerals. Fig. 1 shows a system diagram of a nuclear power plant using an embodiment of the present invention. 0 Decay heat removal of the present invention. In the device, a steam separator 18 is provided. The gas phase part of the steam/water separator 18 is connected to the upstream side of the steam generator 17 internal valve v1 of the piping from the steam generator 17 to the turbine 7 via the steam separator inlet stop valve v2, and The bottom of the separator 18 is connected to the water inlet side of the steam generator 17 via a check valve V. Moreover, the upstream side of the main feed water control valve v4 of the pipeline from the high pressure feed water heater 6 to the steam generator 17 is as follows.

It is connected to the liquid phase of the steam/water separator L8 via the steam/water separator water level control valve 5. Further, the gas phase of the steam/water separator 18 is passed through the deaerator heating control valve v6 to the deaerator 10 of the deaerator 10.
a, and is connected to the condenser 8 via a steam separator pressure control valve v7.

The steam separator 18 also has a water level control valve V when the steam separator is on standby.
, is connected to the desiccant reservoir 10a.

Further, there is a water level control valve V on standby for the steam separator in the piping from the gas phase of the steam separator 18 to the deaerator 10a.

A main steam atmosphere release valve vg is provided on the upstream side of the main steam atmosphere release valve vg.

The decay heat removal apparatus of the present invention having the above structure operates as follows. That is, during normal operation of the nuclear reactor, the feed water from the high pressure feed water heater 6 is directly supplied to the steam generator 17,
It is heated while flowing L'r through the steam generator j7, becomes superheated steam at the outlet, and is supplied to the steam turbine 7.

At this time, the steam separator 18 includes a steam separator water level control valve V,
The water supply is supplied through the water separator, and the water level is determined by the water level control valve V when the water separator is on standby.

First, a decay heat removal operation after the nuclear reactor is shut down while the condenser 8 is usable will be described. In this case, water and steam at the outlet of the steam generator 17 are introduced into the steam separator 18 by opening the steam separator inlet stop valve ■2 and closing the steam generator outlet stop valve V. do. A part of the steam separated from this water/steam in the steam separator 18 is recovered during degassing via the deaerator heating control valve V, and the other part is recovered during deaeration via the steam separator pressure control valve V7. is discharged to the condenser 7 via the

Adjust the pressure inside the steam/water separator to a predetermined pressure. The saturated water separated in the steam separator 18 is mixed with water supplied through the steam separator water level control valve vs, and then passed through a check valve v3 through a pipe connected to the inlet side of the steam generator 17.
is returned to the steam generator 17 by natural circulation.

Since heat removal in the steam generator 17 involves boiling, a two-phase flow is generated within the steam generator 17. The above-mentioned circulation force of natural circulation is caused by the density difference between the two-phase flow and the subcooled water returned from the steam-water separator to the steam generator 17, but the density difference is sufficient and the steam generator 17
The amount of circulating water necessary for stable operation can be secured.

Next, a description will be given of the decay heat removal operation after reactor shutdown in a state where the condenser is unusable due to loss of on-site power supply, etc. In this case, the steam separator pressure control valve v7 is closed, and the main steam is released into the atmosphere from the main steam atmosphere release valve V. At this time, open the steam separator inlet stop valve ■2, and open the steam generator outlet stop valve V.
By closing □, the water held in the steam-water separator 18 is sent to the steam generator 17. Steam generator 17
While releasing steam from the main steam atmosphere release valve V, converts the fed water into steam, and performs heat removal for a short period of time until the water is completely consumed.

[Effects of the Invention] As is clear from the above, the decay heat removal device of the present invention does not require a steam drum or a recirculation pump unlike a recirculation type decay heat removal device, and moreover, during normal operation, the decay heat removal device does not require steam drums or recirculation pumps. Since the generator is operated as an integral once-through type, the required heat transfer area is small and therefore economical. Furthermore, during the decay heat removal operation, natural circulation occurs through the attached steam/water separator and steam generator, which removes heat and enables high-temperature shutdown. Furthermore, even if the condenser cannot be used due to a loss of on-site power supply, heat can be removed for a short period of time using only the water held by the steam-water separator. As a result, thermal shock to the nuclear reactor, its constituent members, etc. can be alleviated, and the economic efficiency and reliability of the nuclear reactor can be improved.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a nuclear power plant using an embodiment of the present invention, and FIG. 2 is a system diagram of a nuclear power plant using a conventional recirculating steam generator. FIG. 73 is a system diagram of a nuclear power plant using a conventional integrated once-through steam generator.

Claims (1)

[Claims] The gas phase is communicated between the once-through steam generator and the steam separator inlet stop valve upstream of the steam generator outlet stop valve of the piping from the once-through steam generator outlet to the steam turbine, and the steam separator A steam-water separator that communicates the liquid phase upstream of the main water control valve of the piping from the deaerator to the steam generator via a water level control valve, and to the inlet side of the steam generator via a check valve. , a deaerator heating control valve provided in the piping that communicates the gas phase of the steam/water separator with the deaerator reservoir of the deaerator, and a main steam atmospheric release device provided upstream of the deaerator heat control valve. and a steam separator standby water level control valve provided in a pipe that communicates the deaeration reservoir and the steam separator, and during normal operation, the water separator inlet stop valve is closed and this is the main valve. It is shut off from the steam circuit, and after the reactor is shut down when the condenser is usable, the steam separator inlet stop valve generates natural circulation through the steam generator to remove heat, making the condenser unusable. After the reactor is shut down, the steam separator pressure control valve is closed, the steam separator inlet stop valve is opened, the steam generator outlet stop valve is closed, and the water in the steam separator is transferred to the steam generator. A decay heat removal device characterized by removing heat while converting it into steam.