JPS607167B2 - feed water heater system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to feedwater heater systems, and more particularly to feedwater heater systems suitable for use in boiling water nuclear power plants.

As shown in Figure 1, the feedwater heater system used in conventional boiling water nuclear power plants extracts reactor steam generated in a nuclear reactor 1 from a high-pressure turbine 2 and uses it as a heating source for reactor feedwater. high-pressure first and second feed water heaters 8 and 9, and a low-pressure first feed water heater that uses aqueous air from the low-pressure turbine 4 as a heating source.
~Fourth feedwater heaters 10 to 13, and the reactor steam solidified in these feedwater heaters is sequentially guided to the next stage of feedwater heaters and sent to the turbine main condensate by the feedwater heater drain pump 14. In addition, non-condensable gases such as oxygen, hydrogen, and rare gases contained in the reactor steam are also successively introduced to the feedwater heater in the next stage, and finally, It is designed to lead to the space of

In Fig. 1, 3 is a moisture separator, 6 is a condensate demineralizer, 7 is a condensate pump, and 15 is a water supply pump, the dotted line arrow indicates the flow of steam or non-condensable gas, and the solid line arrow indicates the flow of water supply or water supply. It shows the flow of condensed steam. However, in a feed water heater system connected in this way, for example, condensed water and non-condensable gas generated in the high pressure first feed water heater 8 are transferred to the high pressure second feed water heater system.
Since it is used again for heating the feedwater in the feedwater heater 9, it occurs that the non-condensable gas is forced to dissolve into the condensate water in the heater body 17 of the feedwater heater shown in FIG.

Therefore, when high radioactivity flows into the feed water heater in the previous stage, the equipment surface dose rate of the feed water heaters in the subsequent stages into which low radioactivity flows becomes equal to that of the previous stage into which high radioactivity flows. Therefore, a phenomenon occurs in which the device surface dose rate of the low-pressure feedwater heaters 10 to 13 becomes the same as that of the high-pressure feedwater heaters 8 and 9 into which high radioactivity flows. This creates the problem that when operators get close to the feedwater heater to check its operating status, they are exposed to radiation. In addition,
In Fig. 2, 16 is a water chamber, 18 is a heat exchange tube,
19 is a partition plate, 20 is a feed water inflow nozzle, 21 is a feed water outflow nozzle, 22 is a steam inflow nozzle, 23 is a condensed water outflow nozzle, and 24 is a pent nozzle. The present invention has been made in view of the above, and an object of the present invention is to provide a feed water heater system that can reduce the equipment surface dose rate.

A feature of the present invention is that the pent nozzle of each feedwater heater is directly connected to the turbine main condenser, which reduces the dissolution of non-condensable gas into the condensed water and is independent of the non-condensable gas of the preceding feedwater heater. The main point is that the dose rate on the surface of the feed water heater is reduced.

The present invention will be described in detail below with reference to the embodiment shown in FIG. 3 and FIG. 4.

FIG. 3 is a configuration diagram showing an embodiment of the feed water heater system of the present invention. In FIG. 3, the same parts as in FIG.

The difference from Figure 1 is that the high pressure first and second feed water heaters 8
. This is to reduce the dissolution of non-condensable gas into the water heater, and to prevent the once-separated non-condensable gas from dissolving into the condensed water in the next-stage feed water heater. In the case of a feedwater heater system such as the one in the entrusted example, the negative pressure in the turbine main condenser 5 also creates negative pressure in each of the feedwater heaters 8 to 13, which reduces the pressure inside the feedwater heater body and the radiation dose on the surface of the equipment. Since there is a relationship shown in Figure 4 between the penetration amount of radioactive N16, which is the main source of radiation, the NI
The amount of B dissolved into condensed water can be reduced.
Therefore, the feedwater heater surface dose rate decreases, and the feedwater heater surface dose rate decreases, and the feedwater heater surface dose rate decreases. When high radioactivity flows in, there is no possibility that the surface dose rate of the feed water heaters of the next stage and subsequent stages into which low radioactivity flows will be the same as that of the feed water heaters into which high radioactivity flows. Therefore, the radioactivity concentration in the air in the room where the feedwater heater is installed (due to leakage from the valve installed in the feedwater heater) is also reduced, making it possible to reduce the radiation exposure of operators. Note that the magnitude of the negative pressure within the feed water heater can be easily set by the diameter and length of the pent nozzle 24 of the feed water heater, and this can also be done using the flow rate control valve 25.
Since the reactor steam flowing into the feedwater heater has a constant flow rate during normal operation, even if the pent nozzles 24 of the feedwater heaters 8 to 13 are directly connected to the turbine main condenser 5, the vent nozzles 24 The flow rate of the flowing non-condensable gas is almost constant, and does not cause any trouble in the operation of the turbine main condenser 5. As explained above, according to the present invention, it is possible to reduce the amount of non-condensed gas containing radioactive substances that dissolves in condensed water, which reduces the surface dose rate of the feed water heater, which is a radiation source, and increases radioactivity. It has the remarkable effect of reducing radiation exposure.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional feed water heater system, Fig. 2 is a schematic structural diagram of a feed water heater system, Fig. 3 is a block diagram showing an embodiment of the feed water heater system of the present invention, and Fig. 4 is a block diagram of a conventional feed water heater system. It is a relationship diagram between the pressure inside the feed water heater body and the amount of N16 dissolved into condensed water. 1...Nuclear reactor, 2...High pressure turbine,
4...Low pressure turbine, 5...Turbine main condenser, 7...Condensate pump, 8, 9...High pressure first and second feed water heaters, 10 ~13...Low pressure 1st
~4th water supply radiator, 14...Drain pump, 1
5... Water supply pump, 17... Water heater body, 24... Vent nozzle. Ito'zu Ito Z Zushu 3 Zumuzu

Claims (1)

[Claims] 1. A feedwater heater system comprising a plurality of feedwater heaters, characterized in that a vent nozzle of each of the feedwater heaters is directly connected to a turbine condenser.