JPS5848880B2 - pressure tube reactor - Google Patents

Description

[Detailed description of the invention] The present invention relates to feed water heating for pressure tube nuclear reactors.

Conventionally, feed water in a nuclear reactor is heated by heating water (feed water) from a condenser using steam extracted from a turbine.

Figure 1&'! This shows the main steam system and water supply system of a 550 MWt class pressure tube reactor, including a high pressure turbine 1, low pressure turbines 2 and 3, a generator 4, a moisture separator 5, a condenser 6, an air extractor 7, Gland steam condenser 8, low pressure feed water heater 9
, 10, 11, high-pressure feed water heaters 12, 13, a condensate pump 14, and a water feed pump 15.

The high-pressure steam 16 coming out of the steam drum then enters the high-pressure turbine 1, and a portion of the low-pressure steam 1 that comes out of this high-pressure turbine 1
7 enters the low pressure turbines 2 and 3 after moisture is removed by the moisture separator 5.

Steam 18 discharged from the low pressure turbines 2 and 3 and a portion of steam 19 discharged from the high pressure turbine 1 are sent to a condenser 6.

Also, in order to heat the feed water 25, steam 20, 21, 22, 23 is generated from the high pressure turbine 1 and the low pressure turbines 2, 3.
, 24 are bled and the corresponding low pressure feed water heaters 9, 10,
11 and high-pressure feed water heaters 12 and 13, the steam 20 to 24 heats the feed water, becomes water 26, and is sent to the condenser 6.
to go into.

At the rated output of the 550 MWt class pressure tube nuclear reactor, about 910 t/h of feed water is heated from about 35°C to about 59°C in the first stage low pressure feed water heater 9, The feed water heaters 10 to 13 in the second and subsequent stages heat the water to about 182°C.

On the other hand, in a pressure tube reactor, about 6% of the thermal energy generated by nuclear fission is generated in the moderator (heavy water) outside the pressure tube.

That is, in a 550 MWt class nuclear reactor, approximately 33 MW of heat is generated in heavy water at the rated output.

This heat raises the temperature of heavy water at a flow rate of 1400 t/h by about 20°C, making the core exit temperature of the heavy water about 70°C.

Figure 2 shows the heavy water circulation and system of a 550MWt class pressure tube reactor.

The heavy water circulation system shown in FIG. 2 includes a reactor core 27, a center of gravity dump tank 28, a heavy water circulation pump 29, and a heavy water cooler 3.
0, and the temperature of heavy water 3 rose to approximately 70°C in the core 27.
1 is cooled to about 49° C. by two heavy water coolers 30 (heat transfer area per one is about 100077 L″).

A portion 33 of the low-temperature heavy water 32 discharged from the heavy water cooler 30 is sent to the poison supply/removal system, and the other portion is returned to the reactor core 2T.

Heavy water 34 is returned to the heavy water dump 28 from the poison supply/removal system.

The heat of the high-temperature heavy water 31 entering the heavy water cooler 30 is dissipated into seawater via the auxiliary equipment cooling water 35.

The purpose of the present invention is to use the heat generated in heavy water to heat feed water,
The object of the present invention is to provide a pressure tube nuclear reactor with high power generation efficiency by reducing the amount of steam extracted from the turbine.

The feature of the present invention is that in a pressure tube nuclear reactor in which the coolant and the moderator are separated, a heat exchanger is provided at the front stage of the low-pressure feed water heater row, and the moderator or the moderator is provided on the primary side of the heat exchanger. The fluid heated by the moderator is passed through the secondary side, and the feed water is passed through the secondary side, and the feed water is heated by the heat of the moderator heated in the core or the fluid heated by the moderator, and air is extracted from the turbine. This configuration reduces the amount of steam extracted from the turbine, resulting in a pressure tube nuclear reactor with high power generation efficiency.

The present invention will be explained below based on the drawings.

FIG. 3 shows an embodiment of the present invention, in which a heat exchanger 36
This reactor is similar to the pressure reactor shown in FIG. 1, except that a heavy water cooler 37 is installed.

The heat exchanger 36 is installed at the front stage of the row of low-pressure feed water heaters, that is, at the installation position of the first stage feed water heater 9 shown in FIG. High-temperature heavy water 31 whose temperature has been raised in the shown reactor core 27 is passed through, and on the secondary side, water is supplied from the grand steam condenser 8 to a row of low-pressure feedwater heaters including low-pressure feedwater heaters 10, 11, . . . 25 is allowed to pass.

The cooler 37 is provided on the downstream side of the heat exchanger 36 in the flow direction of the heavy water 31, and the heavy water discharged from the heat exchanger 36 is passed through the primary side of the heavy water cooler 37, and the secondary Auxiliary cooling water 35 is sent to the side.

The heavy water cooler 37 detects the heavy water cooler outlet temperature and adjusts the flow rate of the auxiliary equipment cooling water 35 to maintain the temperature of the heavy water 32 at the heavy water cooler outlet and core inlet at a set temperature.

Naturally, the heat exchange amount of the heavy water cooler 37 is smaller than that of the heat exchanger 36.

In the pressure tube nuclear reactor of the present invention having the above-mentioned configuration, the steam 20 for heating the low-pressure feedwater in the first stage, which was conventionally extracted from the low-pressure turbine to heat the feedwater 25, no longer needs to be extracted.
Since it can be used to rotate a turbine, power generation efficiency can be improved.

As an example, consider a 550 MWt class pressure tube reactor.

The heat exchanger 36 has a heat transfer area of 1500 m'' and a heat transfer rate of 1.
By using a counterflow type with a flow rate of 0.3 Kcal/m h'C, the temperature of the water supply 25 with a flow rate of 910 t/h can be raised from approximately 35°C to approximately 58.5°C at the rated output, and the flow rate is 400 t/h. It becomes possible to lower the temperature of the heavy water 31 (heat exchanger outlet temperature) from 69°C to about 53.8°C.

In addition, at 25% output, the temperature of the 256 t/h water supply 25 was increased from 40°C to approximately 54.9°C, and the temperature was increased to 1400°C.
The temperature of heavy water 31 per t/h can be lowered from 55°C to about 52.3°C.

In a conventional pressure tube nuclear reactor that heats only with steam extracted from the turbine, the outlet temperature of the first stage low-pressure feedwater heater is approximately 59°C at rated output and 41'C at 25% output. The pressure tube type nuclear reactor of the present invention can obtain temperatures almost equivalent to those of conventional reactors at rated output.

Also, at low output, the feed water temperature is higher than the conventional one, but at rated output the first stage feed water heater outlet temperature is 58.5℃.
Because it is lower than the above, problems such as cavitation of the water supply pump do not occur.

Also, on the core side, even if the feed water temperature increases by 20°C at 25% power, the core population enthalpy will be 2 8 3.
5 Kcal/kg to 2 8 4. 8 Kcan
/kg, the influence on the output distribution and thermal limit value is small and there is no problem.

From the above results, the same effect as the conventional system can be obtained regarding the water supply temperature.

Next, let's consider the temperature of heavy water.

The heavy water temperature at the outlet of the heat exchanger 36 varies depending on the reactor output, and at rated output and 25% output, the outlet temperature of the heavy water cooler of a conventional pressure tube reactor (the set temperature 4 depending on the flow rate of auxiliary cooling water)
The temperatures are approximately 5°C and 3°C higher than the 9°C control temperature, respectively.

Therefore, the heavy water cooler 37 adjusts the temperature at the outlet of the heavy water cooler and the inlet of the core by changing the flow rate of the auxiliary cooling water 35 so that it reaches the set temperature.

The heat transfer area of the counter-current heavy water cooler is 30 Om, the heat transfer rate is 103 Kcal/mh'c, and by flowing auxiliary cooling water 35 at +250 t/h at rated output, the heavy water temperature can be reduced from 53.8°C to approximately It can be brought to 49°C.

Furthermore, at 25% output, the heavy water temperature can be raised from 52.3°C to about 49°C by flowing about 250 t/h.

Next, we will discuss the amount of increase in power generation output when the amount of steam extracted from the turbine is reduced.

At rated output, the low pressure feed water heater 9 of stage I in Fig. 1
The enclosing power of 20 steam to be extracted is 566 KCal/k.
g, the flow rate is approximately 29 t/h.

This steam is used to rotate the turbine 5 3 4.
When the steam 18 has an enthalpy of 9 Kcal/kg (assuming that the enthalpy of the steam discharged from the turbine does not change even if the amount of extracted steam from the turbine is reduced), the generated electricity output is equal to the conventional generator output 1 6 5 M
It increases by about 0.6% compared to We.

Note that the same members are designated by the same reference numerals in FIGS. 1, 2, and 3 for explanation.

FIG. 4 shows another embodiment of the present invention, in which the heavy water system and the water supply system are installed in separate buildings.

In a pressure tube reactor, the heavy water system is usually located in the reactor building, and the feedwater heater is located in the turbine building.

Therefore, in the embodiment shown in FIG. 4, a closed-loop light water circulation system including a light water circulation pump 39 is connected between the heavy water cooler 30 and the heat exchanger 36 for heating the water supply 25.

The light water 38 flowing through the light water circulation system is heat exchanged with high temperature heavy water 31 in the heavy water cooler 30 of the heavy water system, and the water supply 25 is heated by the light water 38 whose temperature has been raised.

This makes it possible to heat the feed water 25 with the heavy water 31 by arranging the heavy water system in the reactor building and the feed water heater in the turbine building.

The present invention has the above-described structure and function, and uses high-temperature heavy water to heat the water supply, thereby reducing the amount of air extracted from the turbine, thereby improving power generation efficiency.

[Brief explanation of the drawing]

Figure 1 is a system diagram of the main steam system and water supply system of a pressure tube reactor, and Figure 2 is a system diagram of the heavy water system. FIG. 3 is a system diagram of feed water heating according to the present invention, and FIG. 4 is a system diagram of feed water heating according to the present invention in which the heavy water system and the water supply system are arranged in separate buildings. io, 1i...Low pressure water heater, 21, 22.
...Steam extracted from the low pressure turbine, 25...
... Water supply, 26 ... Water after heating the water supply, 27.
...Reactor core, 30,37...Heavy water coming out of the heavy water cooler, 35...Auxiliary equipment cooling water, 36...
...Heat exchanger, 38...Light water.

Claims (1)

[Claims] 1. In a pressure tube nuclear reactor in which the coolant and moderator are separated, a heat exchanger is provided upstream of a row of low-pressure feed water heaters, and a moderator is provided on the primary side of the heat exchanger. The fluid heated by the moderator or the moderator is passed through the secondary side, and the feedwater is heated by the heat of the moderator heated in the core or the fluid heated by the moderator. A pressure tube nuclear reactor characterized by reduced steam extraction. 2. A closed-loop light water circulation system connected to a heavy water cooler is connected to the heat exchanger, and the water supply is heated by the heat of the light water heated by the heavy water cooler. A pressure tube nuclear reactor according to claim 1.