JPS59120993A - Reactor cooling 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] [Technical Field of the Invention] The present invention is directed to a direct core cooler that directly cools two cores in order to ensure the health of a nuclear reactor even in the event of an abnormality in a nuclear reactor plant such as a total loss of power. This invention relates to a nuclear reactor cooling system equipped with a

[Technical background of the invention and its problems] The basics of nuclear reactor safety are ensuring that the reactor is stopped under any conditions (2. Smooth cooling of the nuclear heat generated within the reactor). For example, in many nuclear reactors, multiple safety protection devices are installed on the control rods that shut down the reactor, allowing them to respond accurately to various accident events.On the other hand, the heat removal system Since decay heat is generated within the furnace even after the furnace is shut down, a dedicated cooling system is often installed independent of the normal heat removal system in order to reliably cool down the decay heat.For example: Direct core coolers are provided to remove decay heat generated within the reactor even after the reactor has scrammed due to an abnormal situation in the reactor plant such as a total power loss accident.

A nuclear reactor with a conventional direct core cooler will be described with reference to FIG. As shown in the figure, the reactor vessel! A reactor core 2 is disposed inside the reactor core 2, and the coolant 3 is passed through the inlet pipe 4, the lower plenum, the inlet lower of the flow adjustment section 8, and then the reactor core support structure 6 and the reactor core 2.
The core 2 is cooled by a circulation system that extends from the upper plenum to the outlet pipe 5, and further to the inlet pipe 4 via an external heat exchanger (not shown). A shielding plug 9 is provided at the upper end of the reactor vessel l, while a direct core cooler 10
is composed of an in-furnace cooler 11 and an out-of-furnace cooler 12, the in-furnace cooler 11 is located in the upper blenheim of the furnace vessel l and is immersed in the coolant 3, and the out-of-furnace cooler 12 is located in the upper blenheim of the furnace vessel l. The coolers 11 and 12 are located outside the container 1, and are connected by a pipe that passes through a shielding plug 9. Direct core cooler 1
The coolant to be filled in the reactor is selected from one that has excellent heat transport properties and is chemically stable even if it comes into contact with the reactor coolant. For example, in a liquid metal cooled fast breeder reactor, the reactor coolant is liquid sodium, so liquid sodium or a mixed fluid of sodium and potassium is used also in the direct core cooler. Furthermore, the coolant in the direct core cooler is generally driven by natural circulation force in many cases. The reason for this is that in an event where the direct core cooler is forced to operate, it is expected that external driving force cannot be relied upon, such as in a total power loss accident.

On the other hand, the outside cooler 12 is cooled with air or inert gas, but the flow of the inert gas here is often provided by natural convection force for the reasons mentioned above.

In a nuclear reactor equipped with such a direct core cooler, the first problem is heat loss from the direct core cooler during normal operation of the reactor, that is, when the direct core cooler is in a rest state. Therefore, during normal operation, a large temperature difference occurs in the direct core cooler due to the flow of coolant, and when the direct core cooler is activated in an emergency, it causes a large thermal shock to the heat transfer tubes, causing a large temperature difference in the direct core cooler. There are concerns that this may damage the health of the company. On the other hand, if the external cooler is covered with an electric heater, etc. to uniform the temperature distribution inside the direct core cooler and maintain insulation, the direct core cooler will not be able to start up quickly, and temporary It is conceivable that the reactor core could become overheated, impairing the integrity of the reactor.

[Purpose of the invention]

The present invention has been made to solve the above conventional problems, and its purpose is to prevent heat release from the direct core cooler during normal operation and to smoothly start up the direct core cooler. The aim is to provide a nuclear reactor cooling system that has been developed.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention allows a coolant to flow through an inflow pipe of a lower plenum of a reactor vessel, passes through a reactor core, and flows out of an outflow pipe of an upper plenum of a reactor vessel, In a reactor cooling system, in which gas is sealed in the upper plenum of the reactor vessel, a shielding plug is disposed at the upper end of the reactor vessel, and a core cooler is provided directly passing through the shielding plug, one end of the pressure pipe is The pressure tube is fixed to the shielding plug, the other end is immersed in the coolant, and a directional flow path breaker is provided on the side wall of the pressure tube, and the gas pressure in the upper plenum space where the direct core cooler is arranged is controlled. A gas pressure adjustment device is provided to adjust the pressure, and the direct core cooler is configured to exist in a gas atmosphere when it is inactive and in a coolant atmosphere when it is in operation,
Further, a check valve is used as the directional flow path breaker.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a longitudinal cross-sectional view of a nuclear reactor cooling system according to the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals. That is, as shown in FIG. 2, the reactor core 2 is disposed in the reactor vessel l, and the coolant 3 is supplied from the inlet pipe 4 of the reactor vessel l and the inflow lower of the coolant flow adjustment section 8 located in the lower plenum. Exit piping 5 passes through the core support structure 6, the core 2, and from the upper plenum.
The reactor core 2 is cooled by a circulation system that flows through the reactor to the inlet pipe 4 via an external heat exchanger (not shown). A shielding plug 9 is provided at the upper end of the furnace vessel l. The direct core cooler 10 is composed of an in-core cooler 11 and an external cooler 12. It is airtightly fixed to the shielding plug 9 and surrounded by a pressure pipe 13 whose other end is open and immersed in the coolant 3. This pressure pipe 1
A directional flow path breaker 14 such as a check valve is disposed on the side wall of 3. As shown in the enlarged view of FIG. 3, when the internal pressure of the pressure pipe 13 is higher than the gas pressure in the upper furnace plenum, the flow path breaker 14 overcomes the spring 2o and closes the flow path breaker 1.
Close 4. Note that 21 is Patsukin. However, when the internal pressure of the pressure pipe 13 decreases to the same level as the pressure in the upper furnace plenum, the flow path breaker 1 is closed due to the repulsive force of the spring 20.
4 is in an open state, and the coolant flows into the pressure pipe 10 through the flow hole 19. FIG. 4 shows a modification of the flow path breaker. As shown in this figure, a small chamber 23 is formed by a wall 22 having an angular cross section so as to surround the communication hole 19 of the pressure pipe 13.
make. A flow path breaker 25 is formed at the upper end of the small chamber 23 and is opened and closed by a spring 24 . Now, if the internal pressure of the pressure pipe 13 is higher than the gas pressure in the upper furnace brenum, it overcomes the spring 24 and closes the flow path breaker 25. On the other hand, when the internal pressure of the pressure pipe 13 decreases and becomes comparable to the pressure in the upper furnace plenum, the flow path breaker 25 is opened due to the repulsive force of the spring 24 and gravity, and the coolant passes through the flow holes 26.19. and flows into the pressure pipe 13. Further, the pressure pipe 13 is connected to a gas storage tank 15 arranged outside the furnace vessel l, as shown in FIG. A gas supply valve 17 is provided between the gas storage tank 15 and the pressure pipe 13, and an exhaust valve 18 is provided in the branch pipe.

Here, a branch pipe (two exhaust valves 18) communicates with the cover gas of the reactor.

Next, the operation of the nuclear reactor cooling system of the present invention will be explained.

First, during reactor operation, the gas supply valve 17 is opened and the exhaust valve 18 is closed, thereby supplying gas from the gas storage tank 15 into the pressure pipe 13. As a result, the internal pressure of the pressure pipe 13 increases, so that the liquid level of the coolant in the pressure pipe 13 becomes lower than the liquid level L2 of the coolant in the upper furnace blennium, as shown in FIG. That is, the control of the coolant liquid level in the pressure pipe 13 can be arbitrarily changed by the volume of the gas storage tank 15 and the gas filling pressure, and the temperature of the filling gas is adjusted by the electric heater 16 built into the gas storage tank 15. Ru.

During reactor operation, the liquid level of the coolant in the pressure pipe 13 is lowered to isolate the reactor cooler 11 from the reactor coolant 3 as described above. Since the gas is present between the in-furnace cooler 11 and the coolant 3 in this way, heat exchange between the in-furnace cooler 11 and the coolant 3 is suppressed. In such a state, the heat insulation properties can be further improved by heating the gas to the reactor coolant temperature. Moreover, the thermal energy required to heat the gas is not used in the outside cooler 12 as in the conventional case.
The amount of heat required is significantly less than that required when maintaining heat insulation by preheating. Furthermore, natural circulation of the coolant in the direct core cooler IO can be maintained based on heat transport from the gas filled in the pressure pipe 13. That is, even when the direct core cooler 0 is inactive, the coolant continues to flow in the direct core cooler 10. Therefore, in the event of an abnormality in the reactor, the direct core cooler 10 is activated immediately,
Able to demonstrate predetermined abilities.

FIG. 5 shows the state in which the nuclear reactor cooling system of the present invention is in operation, ie, when all power is lost, for example.

When directly operating the core cooler IO, the pressure pipe 13 is closed by closing the gas supply valve 17 and opening the exhaust valve 18.
Make the cover gas pressure in the reactor vessel the same as the cover gas pressure in the reactor vessel. As a result, the liquid level in the pressure pipe I3 rises, the flow path breaker 14 also opens, and natural circulation heat removal is performed in the reactor vessel via the in-core cooler L1 of the direct core cooler IO.

As explained above, during normal operation of the reactor, the gas supply valve 17 is opened and the exhaust valve L8 is closed, and when all power is lost, the gas supply valve 17 is closed and the exhaust valve ``8'' is opened. It is possible to perform the functions of .

FIG. 6 shows another embodiment of the invention. The same parts as in FIG. 2 are given the same reference numerals. As shown in the figure, the pressure pipe 27 is located in the center of the upper plenum of the furnace, one end of which is airtightly fixed to the shielding platen, and the other end immersed in the coolant 3. Due to this arrangement of the pressure tubes, the gas-filled space in the upper plenum of the reactor vessel is divided into the inside of the pressure tube 27 and the outside of the pressure tube 27, that is, an annular portion surrounded by the pressure tube 27 and the reactor vessel. The in-core cooler 11 of the direct core cooler IO is arranged in the annular portion as shown. In addition, coolant 3
Cools the reactor core 2 through the inlet pipe 4 of the reactor vessel and the inlet lower of the flow adjustment section 8, and flows from the upper plenum to the outlet pipe 5 of the reactor vessel.

12 is an external cooler of the direct core cooler 10; 15 is a gas storage tank; the temperature of the filling gas is regulated by a heater 16; 28 is a flow path breaker.

During normal operation of the reactor, the gas supply valve 17 is opened and the exhaust valve 18 is closed to supply the gas in the gas storage tank 15 to the annular portion, and to drain the coolant in the annular portion, as in the previous embodiment. When pushed downward, the in-furnace cooler 11 becomes exposed from the coolant 3.

Then, heat exchange between the in-core cooler 11 and the coolant 3 is suppressed, and even when the direct core cooler IO is inactive, the coolant continues to flow in this cooler, so in the event of a reactor abnormality, Direct core cooler lO can be activated immediately.

〔Effect of the invention〕

According to the nuclear reactor cooling system of the present invention, not only the heat insulation properties of the direct core cooler when it is inactive is improved, but also its startup can be performed smoothly, so that the reliability of the nuclear reactor can be further improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a conventional reactor cooling system, FIGS. 2 and 5 are vertical cross-sectional views of the reactor cooling system of the present invention during shutdown and operation, respectively, and FIG. 3 is a vertical cross-sectional view of a conventional nuclear reactor cooling system. FIG. 4 is a longitudinal sectional view of a modified example of the flow path breaker according to the present invention, and FIG. 6 is a longitudinal sectional view of another embodiment of the present invention. 1... Reactor vessel 2... Core 3... Coolant 4, 5... Piping 6... Core support structure
9...Shielding plug IO...Direct core cooler 13.
27...Pressure pipe 14.25.28...Flow path breaker [5...191 tank 16...Heater 17.
...Gas supply valve 18...Exhaust valve 19.26...
- Distribution hole (8733) Agent Patent attorney Yoshiaki Inomata (
(and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] +1) Inflow from the inflow pipe of the lower blennium of the furnace vessel,
Coolant is made to flow through the reactor core and flows out from the outflow piping of the upper blemish of the reactor vessel, gas is sealed in the upper blemish of the reactor vessel, and a shielding plug is disposed at the upper end of the reactor vessel. In a reactor cooling system equipped with a direct core cooler that penetrates the plug, one end of the pressure pipe is fixed to the shielding plug, the other end is immersed in the coolant, and a directional flow path shield is installed on the side wall of the pressure pipe. A nuclear reactor cooling system, further comprising: a gas pressure adjustment device for adjusting the gas pressure in the upper brenum space in which the direct core cooler is disposed. (2) The nuclear reactor according to claim 1, wherein the direct core cooler exists in a gas atmosphere when the cooler is inactive, and in the cooling environment when it is in operation. Cooling system. (3) The reactor cooling system according to claim 1, wherein the directional flow path breaker is a check valve.