JP6422103B2 - Decay heat removal system for fast breeder reactor - Google Patents

Description

  The present invention relates to a decay heat removal system facility for a fast breeder reactor.

  In fast breeder reactors, decay heat removal system equipment is installed in the primary cooling system in order to remove decay heat (residual heat) generated even after the reactor is shut down. The decay heat removal system facility is in a standby state during plant operation.

Conventionally, as such decay heat removal system equipment, for example, without installing dynamic equipment in the primary cooling system shown in FIG. 2, the heat exchanger is directly immersed in the reactor vessel to cool the coolant in the reactor vessel. Direct Reactor Auxiliary Cooling System (DRACS) 51, Primary Reactor Auxiliary Cooling System (PRACS) 52 that cools by incorporating an auxiliary cooler in the primary cooling system, Secondary Cooling System There are known decay heat removal system facilities such as an intermediate reactor auxiliary cooling system (IRACS) 53 which is provided with an auxiliary cooler to cool it (see Non-Patent Documents 1 and 2 below). In FIG. 2, 10 is a reactor vessel, 11 is a core, 51a, 52a and 53a are air coolers, 61 is an intermediate heat exchanger (IHX), 62 is a steam generator (SG), and 63 is a turbine. .
An auxiliary core cooling type decay heat removal facility that cools the core without using the main cooling system is also known (see Patent Document 1 below).

  Such decay heat removal system equipment is activated by a reactor trip signal, etc., when an abnormality occurs in the plant and the reactor is shut down urgently (reactor trip), and the decay heat generated in the core after the reactor trip is generated. It is designed to remove and safely bring the plant to a low temperature state, and extremely high reliability is required.

  FIG. 3 shows an example of a decay heat removal system facility of a conventional auxiliary core cooling system. In the decay heat removal system facility of the auxiliary core cooling system shown in FIG. 3, during the decay heat removal operation, the primary coolant 17 in the reactor vessel upper plenum 14 is intermediately heated via the primary system hot leg piping 22 by the primary system electromagnetic pump 26. After circulating through the exchanger 21 and cooling it with the secondary coolant cooled by the cooler 31 of the secondary cooling system, the cooled primary coolant 17 is passed through the primary cold leg piping 23 to the lower part of the reactor vessel. The core 11 is cooled by returning to the plenum 16.

  Here, the decay heat removal system equipment is in a standby state during the rated power operation of the reactor. At this time, the primary cold leg piping 23, the intermediate heat exchanger 21, and the primary hot leg from the high-pressure reactor vessel lower plenum 16 are put on standby. In order to prevent the primary coolant 17 from flowing into the reactor vessel upper plenum 14 through the piping 22 to prevent the coolant flow rate in the reactor core 11 from decreasing, a check valve 27 is provided in the primary cold leg piping 23. It has been.

  By the way, while the atmospheric temperature in the reactor containment vessel 40 is around 55 ° C., for example, the melting point of liquid sodium used as the primary coolant 17 is about 100 ° C. Therefore, if the state where the primary coolant 17 stays in the primary hot leg piping 22 and the primary cold leg piping 23 continues for a long time, the primary coolant 17 in the primary hot leg piping 22 and the primary cold leg piping 23 during standby. The temperature becomes lower than the melting point due to the dissipated heat, and the primary coolant 17 may freeze.

  Therefore, in the decay heat removal system facility of the auxiliary core cooling system, a bypass line 28 that bypasses the check valve 27 is provided, and the primary cold leg pipe 23 is connected from the high-pressure reactor vessel lower plenum 16 during the rated power operation of the reactor. (Bypass line 28), intermediate heat exchanger 21, primary hot leg piping 22, primary coolant 17 is circulated to the reactor vessel upper plenum 14 through a minute flow rate, and in the primary hot leg piping 22 and primary cold leg piping 23. The coolant is prevented from freezing. Since the pressure in the reactor vessel lower plenum 16 is higher than the pressure in the reactor vessel upper plenum 14 by the pressure loss of the core 11, the auxiliary core cooling type decay heat removal equipment has a flow of the primary coolant 17 during standby. The reverse of the decay heat removal operation.

  When the flow rate of the primary coolant 17 that bypasses the core 11 during the rated power operation of the reactor increases, the flow rate of the coolant passing through the core 11 decreases. Therefore, an adjustment valve (bypass valve) 29 is provided in the bypass line 28 so that the flow rate of the primary coolant 17 that bypasses the core 11 can be adjusted.

JP 59-222790 A JP 2002-341080 A

Masao Hori, Basic Fast Reactor Engineering Editorial Committee (edition), "Basic Fast Reactor Engineering", Nikkan Kogyo Shimbun, October 1993, p. 172 “Reactor Encyclopedia ATOMICA”, [online], September 2010, Research Organization for Advanced Information Science and Technology (RIST), [searched on July 28, 2014], Internet <URL: http: // www .rist.or.jp / atomica / data / dat_detail.php? Title_No = 03-01-02-12>

  However, as described above, in the conventional auxiliary core cooling type decay heat removal system facility, a part of the primary coolant 17 bypasses the core 11 during plant operation. For this reason, it is necessary to fix the opening of the adjusting valve 29 in order to limit the flow rate of the coolant that bypasses the core 11 to a minute flow rate by adjusting the opening of the adjusting valve 29 in the initial stage of operation. Equipment to be added. Furthermore, in order to secure the flow rate through the core 11, it is necessary to increase the flow rate of the primary coolant 17 by the core bypass flow rate by a primary pump of the main cooling system (not shown). It was.

  In addition, when the flow rate of the primary coolant 17 flowing through the bypass line 28 increases due to the opening of the regulating valve 29 due to a malfunction or the like during rated power operation of the reactor, the flow rate of the primary coolant 17 passing through the core 11 is increased. It is necessary to stop the plant because of the shortage. Accordingly, it has been necessary to constantly monitor the flow rate of the primary coolant 17 flowing through the bypass line 28 and to reliably transmit a signal for stopping the plant when necessary.

  When the decay heat removal operation is started, the primary electromagnetic pump 26 is energized so that the primary coolant 17 passes from the intermediate heat exchanger 11 through the primary cold leg pipe 23 (check valve 27) to the lower part of the reactor vessel. Flow to plenum 16. Therefore, if a malfunction occurs in the opening operation of the check valve 27 such that the check valve 27 is not fixed and does not operate, it becomes impossible to secure the flow rate of the primary coolant 17 necessary for removing the decay heat of the core 11. There is also a problem that the function of cooling the core may be lost.

  In other words, in the conventional auxiliary core cooling type decay heat removal system equipment, it is essential to drive the primary system dynamic device (primary system electromagnetic pump 26) and valve operation (operation of the check valve 27), in other words, the core. There is a risk that the core cannot be cooled due to the malfunction or failure of the primary cooling system dynamic equipment, because it is impossible to eliminate the possibility of malfunctions in the primary system dynamic equipment and valve operation necessary for cooling the heat exchanger 11 There was a problem, and further improvement in reliability was demanded.

  In contrast to the auxiliary core cooling type decay heat removal system facility shown in FIG. 3, the direct core auxiliary cooling type decay heat removal system facility 51 shown in FIG. 2 is configured such that the primary coolant is a secondary coolant in the heat exchanger. It is cooled by heat exchange and flows downward due to the density difference of the coolant. Therefore, the primary coolant flowing in from the inlet provided in the upper part of the heat exchanger by natural circulation is cooled by the heat exchanger to form a flow that flows out from the outlet provided in the lower part of the heat exchanger. The The primary coolant in the reactor vessel upper plenum cooled by the heat exchanger flows through a shield (not shown) surrounding the non-heated core opposite to that in normal operation and flows into the lower part of the reactor core. The core is cooled by flowing into the upper plenum of the reactor vessel.

  In this system, a heat exchanger is installed in the upper plenum of the reactor vessel, and even when liquid sodium is used as the primary coolant, this heat is exchanged with the primary coolant during plant operation. It is possible to prevent the secondary coolant from freezing. However, since the heat exchanger is installed in the reactor vessel, it is necessary to shield around the heat exchanger in order to avoid activation of the coolant on the secondary side of the heat exchanger. A large heat exchanger needs to be installed in the reactor vessel. For this reason, there has been a problem that the diameter of the reactor vessel is increased, the reactor vessel and the reactor building are increased, and the construction cost of the plant is increased.

  Accordingly, an object of the present invention is to provide a decay heat removal system facility that can improve the reliability without increasing the size of the facility.

The decay heat removal system facility according to the first invention for solving the above-mentioned problems is
An intermediate heat exchanger disposed outside the reactor vessel, a primary hot leg pipe and a primary cold leg pipe connecting the reactor vessel and the intermediate heat exchanger, and the primary hot leg pipe and the primary cold leg pipe. In the decay heat removal system equipment having a primary cooling system provided with a primary hot leg piping heat insulating material and a primary cold leg piping heat insulating material, respectively covering,
The intermediate heat exchanger is installed at a position higher than the liquid level of the primary coolant in the reactor vessel;
An end of the primary system cold leg pipe on the reactor vessel side is disposed in a partition wall side that divides the upper plenum and the intermediate plenum in the upper plenum of the reactor vessel,
An end of the primary system hot leg piping on the reactor vessel side is in the upper plenum of the reactor vessel and is lower than the liquid level of the primary coolant, and on the reactor vessel side of the primary system cold leg piping. It is arranged at a position higher than the tip,
And the said primary type | system | group cold leg piping heat insulating material is heat dissipation higher than the said primary type | system | group hot leg piping heat insulating material, It is characterized by the above-mentioned.

Moreover, the decay heat removal system equipment according to the second invention for solving the above problems is the decay heat removal system equipment according to the first invention,
The primary hot leg piping heat insulating material and the primary cold leg piping heat insulating material are made of the same material, and the thickness of the primary cold leg piping heat insulating material is smaller than the thickness of the primary hot leg piping heat insulating material, To do.

In addition, the decay heat removal system facility according to the third invention for solving the above problems is the decay heat removal system facility according to the first or second invention,
The primary cooling system does not have a pump.

Further, the decay heat removal system facility according to the fourth invention for solving the above-mentioned problems is any one of the first to third inventions,
The material and thickness of the primary cold leg piping heat insulating material are set so that the surface temperature of the primary cold leg piping heat insulating material is equal to or lower than a predetermined temperature when the primary coolant is in a preset high temperature state. It is characterized by that.

  According to the decay heat removal system facility according to the present invention described above, since the intermediate heat exchanger can be installed outside the reactor vessel, it has been conventionally installed in the primary cooling system without increasing the diameter of the reactor vessel. Since dynamic devices such as electromagnetic pumps and check valves can be eliminated, it is possible to improve the reliability of decay heat removal system facilities and rationalize the facilities by not requiring these dynamic devices. Can also be planned.

It is a mimetic diagram showing decay heat removal system equipment concerning one example of the present invention. It is a schematic diagram which shows an example of the conventional decay heat removal system equipment. It is a schematic diagram which shows an example of the decay heat removal system equipment of the conventional auxiliary core system cooling system.

  Hereinafter, the details of the decay heat removal system facility according to the present invention will be described with reference to the drawings.

A decay heat removal system facility according to an embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, the reactor vessel 10 has a core 11 inside. In the reactor vessel 11, a reactor vessel upper plenum 14, a reactor vessel intermediate plenum 15, and a reactor vessel lower plenum 16 that are vertically divided by a partition wall 12 and a skirt portion 13 that supports the core 11 are formed. Has been.

  And the primary cooling system 20 of the decay heat removal system equipment which concerns on a present Example is the upper nozzle 21a provided in the upper part of the intermediate heat exchanger 21 arrange | positioned outside the reactor vessel 10, and the intermediate heat exchanger 21. A primary hot leg pipe 22 connecting the reactor vessel upper plenum 14 and a primary cold leg pipe 23 connecting the lower nozzle 21b provided at the lower portion of the intermediate heat exchanger 21 and the reactor vessel upper plenum 14. Yes.

  In the intermediate heat exchanger 21, the position of the lower nozzle 21b is the liquid level of the primary coolant 17 in the reactor vessel upper plenum 14 (more specifically, the primary in the reactor vessel upper plenum 14 shown by a solid line in FIG. 1). The coolant 17 is disposed so as to be higher than the liquid surface 17a of the primary coolant 17 when the coolant 17 is in a high temperature state. As the intermediate heat exchanger 21, for example, the one disclosed in Patent Document 2 can be used.

  The primary system hot leg pipe 22 has an end on the reactor vessel upper plenum 14 side at the liquid level of the primary coolant 17 in the reactor vessel 10 (more specifically, the reactor vessel upper plenum 14 shown by a one-dot chain line in FIG. (The liquid level of the primary coolant 17 when the primary coolant 17 in the inside is in a low temperature state) is not exposed from the 17a and is higher than the end of the primary cold leg pipe 23 on the reactor vessel upper plenum 14 side. It is arranged. Further, the primary hot leg piping 22 is covered with a primary hot leg piping heat insulating material 24 in order to maintain the temperature of the primary coolant 17 and reduce the burden on air conditioning.

  Here, the material, thickness, density, and the like of the primary system hot leg piping heat insulating material 24 are at least when the primary coolant 17 reaches a preset high temperature state (for example, 650 ° C.). The ambient temperature in the reactor containment vessel 40 can be maintained at a predetermined temperature (for example, 55 ° C.) or lower, such that the surface temperature of 24 is set to a predetermined temperature (for example, 70 ° C.) or lower. Material, thickness, density, etc.

  In addition, the primary cold leg pipe 23 is disposed near the partition wall 12 between the reactor vessel upper plenum 14 and the reactor vessel intermediate plenum 15 at the end on the reactor vessel upper plenum 14 side. That is, in the present embodiment, the primary cold leg pipe 23 does not penetrate the reactor vessel intermediate plenum 15. Further, the primary cold leg piping 23 is covered with a primary cold leg piping heat insulating material 25 in order to maintain the temperature of the coolant and reduce the burden on the air conditioning.

  Here, the material, thickness, density, and the like of the primary cold leg piping heat insulating material 25 are larger in heat dissipation than the heat dissipation of the primary hot leg piping heat insulating material 24, and the primary coolant 17 in the primary cold leg piping 23. Can be maintained at a temperature that does not freeze, and even when the primary coolant 17 reaches a preset high temperature state (for example, 650 ° C.), the surface temperature of the cold leg pipe heat insulating material 24 is maintained at the primary hot leg pipe heat insulating material 24. A material that can maintain the atmospheric temperature in the reactor containment vessel 40 at a predetermined temperature (for example, 55 ° C.) or less, such as a predetermined temperature (for example, 70 ° C.) or less that is equivalent to The thickness and density.

  In this embodiment, the secondary cooling system 30 of the decay heat removal system equipment is cooled from a cooler 31 (the final heat removal source is seawater or air) 31 provided outside the reactor containment vessel 40 and the intermediate heat exchanger 21. A secondary hot leg pipe 32 for discharging the secondary coolant to the cooler 31, and a secondary cold leg pipe 33 for supplying the secondary coolant cooled by the cooler 31 from the cooler 31 to the intermediate heat exchanger 21. ing.

  When the reactor is operating at rated power, the primary coolant 17 in the reactor vessel upper plenum 14 is at about 550 ° C., and the decay heat removal system equipment is in standby operation. The primary hot leg piping 22 and the primary cold leg piping 23 of the decay heat removal system equipment have an outer diameter of 318.5 mm, the length of each of the pipings 22 and 23 is 30 m, and the thickness of the primary hot leg piping heat insulating material 24. Is 1.5 times as thick as the primary cold leg piping heat insulating material 25 (for example, when the thickness of the primary cold leg piping heat insulating material 25 is 80 mm, the thickness of the primary hot leg piping heat insulating material 24 is 120 mm), When the difference between the heat transfer center of the intermediate heat exchanger 21 and the liquid level of the primary coolant 17 in the reactor vessel upper plenum 14 is 10 m, the standby operation state is as follows when the primary coolant 17 is liquid sodium. It becomes.

  That is, the 550 ° C. primary coolant 17 in the reactor vessel upper plenum 14 flows from the primary hot leg piping 22 to the primary cold leg piping 23 at a flow rate of about 13.6 t / h, and the temperature in the primary hot leg piping 22 is increased. In the primary cold leg piping 23, the temperature decreases due to heat dissipation and flows out to the reactor vessel upper plenum 14 at about 547 ° C.

  In short, the primary hot leg piping insulation material 24 is 1.5 times thicker than the primary cold leg piping insulation material 25, and the thickness of the primary cold leg piping insulation material 25 is thinner than the primary hot leg piping insulation material 24. Therefore, the amount of heat dissipated in the primary system cold leg piping 23 is larger than the amount of heat dissipated in the primary system hot leg piping 22, thereby causing the temperature in the primary system cold leg piping 23 to be higher than the temperature of the primary coolant 17 in the primary system hot leg piping 22. The temperature of the primary coolant 17 becomes lower. Therefore, even if there is no heat dissipation in the intermediate heat exchanger 21, the primary system is caused by the difference in density due to the temperature difference between the primary coolant 17 in the primary system hot leg piping 22 and the primary coolant 17 in the primary system cold leg piping 23. The primary coolant 17 naturally circulates from the hot leg pipe 22 to the primary cold leg pipe 23.

  The liquid sodium that has flowed into the reactor vessel upper plenum 14 from the primary cold leg pipe 23 flows into the lower part of the core 11 through a shield (not shown) surrounding the core 11, passes through the core 11, and cools the core 11. Return to the reactor vessel upper plenum 14.

  In this case, the temperature drop of the primary coolant 17 is as small as about 3 ° C. and does not adversely affect the equipment of the reactor vessel upper plenum 14. Further, the total heat dissipated by the primary hot leg piping 22 and the primary cold leg piping 23 is about 16 kW, and the influence on the heat load of the ventilation air conditioning system in the reactor containment vessel 40 is small.

  In this way, the primary cold leg piping heat insulating material 25 is configured to have higher heat dissipation than the primary hot leg piping heat insulating material 24, and the primary hot leg piping heat insulating material 24 and the primary cold leg piping heat insulating material 25 are made of the same material. And compared with the case where it is the same thickness, since the amount of heat dissipated in the primary system hot leg piping 22 and the primary system cold leg piping 23 is different, there is no possibility that the temperature of the primary coolant 17 is lowered to the ambient temperature in a stopped state without flowing. . For this reason, even when liquid sodium is used as the primary coolant 17, it is possible to prevent the liquid sodium from having a melting point (about 100 ° C.) or less, and a heater or the like so that it can be driven during the decay heat removal operation. Therefore, it is not necessary to maintain the temperature of the liquid sodium at a high temperature.

In the fast breeder reactor, equipment maintenance is performed in a low temperature stop state of about 200 ° C. In this case, the standby operation state of the decay heat removal system equipment is as follows under the above-described conditions.
That is, the primary coolant 17 at 200 ° C. in the reactor vessel upper plenum 14 naturally circulates from the primary system hot leg piping 22 to the primary system cold leg piping 23 at a flow rate of about 7.9 t / h, and in the primary system hot leg piping 22. Then, the temperature is substantially maintained, while the temperature in the primary system cold leg pipe 23 decreases due to heat dissipation and flows out to the reactor vessel upper plenum 14 at about 199 ° C. The liquid sodium that has flowed into the reactor vessel upper plenum 14 from the primary cold leg pipe 23 flows into the lower part of the core 11 through the shield surrounding the reactor core 11, passes through the reactor core 11, cools the reactor core 11, and then enters the reactor vessel upper part. Return to Plenum 14.
Also in this case, the temperature drop of the primary coolant 17 is small, and the primary coolant 17 can be prevented from freezing without adversely affecting the equipment of the reactor vessel upper plenum 14.

  During the decay heat removal operation, the primary coolant is cooled in the intermediate heat exchanger 21 by the secondary coolant cooled by the cooler 31 of the secondary cooling system, and the primary coolant 17 having a low temperature is primary. It flows out to the reactor vessel upper plenum 14 through the system cold leg piping 23. The liquid sodium that has flowed into the reactor vessel upper plenum 14 from the primary cold leg pipe 23 flows into the lower part of the core 11 through the shield surrounding the reactor core 11, passes through the reactor core 11, cools the reactor core 11, and then enters the reactor vessel upper part. Return to Plenum 14.

  As described above, according to the decay heat removal system facility according to the present embodiment, even if the primary cooling system includes the intermediate heat exchanger 21 provided outside the reactor vessel 10, the primary cooling is performed. The primary coolant 17 is circulated by natural circulation between the reactor vessel 10 and the intermediate heat exchanger 21 during standby operation without installing dynamic devices such as an electromagnetic pump, a check valve, and a regulating valve in the system. Freezing of the coolant 17 can be prevented. Therefore, the diameter of the reactor vessel 10 can be made smaller than the reactor vessel cooling method, and the auxiliary core cooling method, the primary system core auxiliary cooling method, the secondary system that require the installation of conventional dynamic equipment, and the secondary Compared with the system core auxiliary cooling method and the like, there is no need to install dynamic equipment and there is no risk of malfunction of the dynamic equipment, so reliability is improved. Furthermore, since there is no need to install dynamic equipment, it is possible to rationalize the equipment.

  In the above-described embodiment, the primary hot leg piping heat insulating material 24 and the primary cold leg piping heat insulating material 25 are made of the same material, and the primary hot leg piping heat insulating material 24 is 1.5 times as large as the primary cold leg piping heat insulating material 25. Although an example of thickness is shown, the present invention is not limited to the above-described embodiment.

  As an example, Table 1 shows that the lengths of the primary system hot leg piping 22 and the primary system cold leg piping 23 are 30 m, respectively, and the primary system cold leg piping heat insulating material 25 has a heat insulating material surface temperature of 70 ° C. or less at a coolant temperature of 650 ° C. Using a microtherm having a thickness of 80 mm (trade name, manufactured by Nippon Microtherm Co., Ltd.), the primary hot leg piping heat insulating material 24 is made of the same material as the primary cold leg piping heat insulating material 25, and the thickness thereof is changed to the primary cold leg piping. The simulation result of the standby operation state when the heat insulating material 25 is changed to 1.25 times, 1.5 times, and 2 times is shown.

  As can be seen from Table 1, when the thickness of the primary hot leg piping heat insulating material 24 is 1.25 to 2 times the thickness of the primary cold leg piping heat insulating material 25, the reactor vessel 10 is preferably used during standby operation. And the intermediate heat exchanger 21 can circulate the primary coolant 17 by natural circulation. Here, as a material for the primary hot leg piping heat insulating material 24 and the primary cold leg piping heat insulating material 25, in addition to microtherm, heat-resistant rock wool, glass wool, or the like may be applied.

  Further, the heat dissipation of the primary cold leg piping insulation material 25 is higher than that of the primary hot leg piping insulation material 24, and the primary coolant 17 is naturally circulated between the reactor vessel 10 and the intermediate heat exchanger 21 during standby operation. If it can be circulated, the primary hot leg piping heat insulating material 24 and the primary cold leg piping heat insulating material 25 may be made of different materials with the same thickness, different materials and different thicknesses, or the same material with the same Needless to say, the thickness and the density of the heat insulating material may be changed, and various changes can be made without departing from the spirit of the present invention.

  The present invention is suitable for application to decay heat removal system equipment for fast breeder reactors.

DESCRIPTION OF SYMBOLS 10 Reactor vessel 11 Core 12 Bulkhead 13 Skirt part 14 Reactor vessel upper plenum 15 Reactor vessel middle plenum 16 Reactor vessel lower plenum 17 Primary coolant 17a Liquid level of primary coolant 20 Primary cooling system 21 Intermediate heat exchanger 21a Upper nozzle 21b Lower nozzle 22 Primary system hot leg piping 23 Primary system cold leg piping 24 Primary system hot leg piping thermal insulation material 25 Primary system cold leg piping thermal insulation material 30 Secondary cooling system 31 Secondary cooler 32 Secondary system hot leg piping 33 Secondary system cold leg Piping 40 Primary containment vessel

Claims (4)

An intermediate heat exchanger disposed outside the reactor vessel, a primary hot leg pipe and a primary cold leg pipe connecting the reactor vessel and the intermediate heat exchanger, and the primary hot leg pipe and the primary cold leg pipe. In the decay heat removal system equipment having a primary cooling system provided with a primary hot leg piping heat insulating material and a primary cold leg piping heat insulating material, respectively covering,
The intermediate heat exchanger is installed at a position higher than the liquid level of the primary coolant in the reactor vessel;
An end of the primary system cold leg pipe on the reactor vessel side is disposed in a partition wall side that divides the upper plenum and the intermediate plenum in the upper plenum of the reactor vessel,
An end of the primary system hot leg piping on the reactor vessel side is in the upper plenum of the reactor vessel and is lower than the liquid level of the primary coolant, and on the reactor vessel side of the primary system cold leg piping. It is arranged at a position higher than the tip,
And the decay heat removal system facility characterized in that the primary cold leg piping heat insulating material has higher heat dissipation than the primary hot leg piping heat insulating material. The primary hot leg piping heat insulating material and the primary cold leg piping heat insulating material are made of the same material, and the thickness of the primary cold leg piping heat insulating material is smaller than the thickness of the primary hot leg piping heat insulating material, The decay heat removal system facility according to claim 1. The decay heat removal system facility according to claim 1 or 2, wherein the primary cooling system does not have a pump. The primary cold leg piping heat insulating material is set to a material and thickness that can maintain the surface temperature of the primary cold leg piping heat insulating material below a predetermined temperature set in advance when the primary coolant reaches a preset high temperature state. The decay heat removal system facility according to any one of claims 1 to 3, wherein the decay heat removal system facility is provided.

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