JP5058016B2 - Non-condensable gas accumulation combustion prevention system - Google Patents

Description

  The present invention relates to a non-condensable gas accumulation combustion prevention system applied to a portion of a nuclear power plant where non-condensable gas may be accumulated.

  In the nuclear power plant, the reactor pressure vessel is accommodated in the reactor containment vessel. The reactor cooling water in the reactor pressure vessel is heated by neutron irradiation accompanying the nuclear reaction in the reactor core and becomes a gas-liquid two-layer flow. On the other hand, a part of the cooling water is decomposed to generate hydrogen gas and oxygen gas. Is generated. In some cases, a small amount of radioactive noble gas such as krypton or xenon leaks from the fuel rod. For this reason, the nuclear power plant is provided with a gas waste treatment system for treating non-condensable gases such as hydrogen gas, oxygen gas, krypton, and xenon.

  On the other hand, the steam generated in the reactor pressure vessel becomes main steam (reactor main steam), is sent to the steam turbine through the main steam system, and the steam turbine works to drive the generator. The main steam pipe constituting the main steam system is branched with a dead-end branch pipe (branch pipe) having no flow considering the safety of the nuclear reactor. This dead end branch has hundreds of lines per nuclear plant. Furthermore, a reactor pressure vessel top vent facility such as a reactor pressure vessel vent system and a reactor pressure vessel head spray system is provided from the top of the reactor pressure vessel.

  The reactor main steam contains a combustible non-condensable gas generated by radioactive decomposition, and this non-condensable gas flows together with the reactor main steam flowing through the main steam system. If there is a stagnant part such as a rising branch pipe or rising branch part in the main steam pipe or vessel containing the reactor main steam, this stagnant part becomes a place where non-condensable gas can accumulate, and the non-condensable gas is Accumulated. An example of rapid combustion by igniting the accumulated non-condensable gas for some reason has been reported.

FIG. 9 explains the mechanism of non-condensable gas accumulation. In general, a main steam pipe (mother pipe) or container (hereinafter referred to as “pipe (mother pipe)”) 1 containing the reactor main steam and a gate valve 3 provided on a rising branch pipe 2 branched therefrom. There is a high possibility that the non-condensable gas 5 is accumulated in the space 4 (location where gas can be accumulated). Reactor main steam flows through the mother pipe (pipe) 1. Since the branch pipe 2 is partitioned by the gate valve 3 and has a dead end, the inflowing reactor main steam is condensed by heat radiation to become water. Then, it is known that the non-condensable gas 5 is left in the branch pipe 2 and the non-condensable gas 5 having a specific gravity lighter than that of the vapor is sequentially accumulated at the branch pipe rising portion (see, for example, Patent Document 1).
JP 2004-12145 A

  In a nuclear power plant, a non-condensable gas 5 stagnates in a gas accumulation location 4 such as a rising branch pipe among branch pipes 2 branched from a main pipe (piping) 1 containing a reactor main steam. The stagnant non-condensable gas 5 may be ignited and burned for some reason.

  In order to prevent the non-condensable gas 5 from being ignited and burned in advance, the generation of the non-condensable gas 5 is suppressed, the gas accumulation of the non-condensable gas 5 is prevented, or the gas accumulation location 4 It is necessary to construct conditions that do not make the combustion environment conditions.

  Patent Document 1 discloses an invention in which a vent hole is provided in the valve body of the gate valve 3, but there is a problem from the viewpoint of protecting the valve and the valve function because it requires processing into the gate valve 3 itself.

  In order to solve these problems, the present invention prevents non-condensable gas from accumulating and burning in advance, ensures the soundness of nuclear power plant equipment and piping, and improves the reliability. An object is to provide a gas accumulation combustion prevention system.

In order to solve the above-described problems, in the present invention, a bypass pipe that connects the upstream side and the downstream side of the on-off valve provided in the gas accumulation-possible location where the non-condensable gas of the nuclear power plant may stay, A bypass pipe opening / closing valve provided in the middle of the bypass pipe, and using a material having lower thermal conductivity than the pipe material other than the gas accumulable location, as the pipe material of the gas accumulable location , Non-condensable gas accumulation combustion prevention characterized in that a magnetic field generator is disposed at a gas accumulable location and the non-condensable gas flows using the paramagnetism of oxygen gas contained in the non-condensable gas. Provide a system.

  ADVANTAGE OF THE INVENTION According to this invention, the accumulation combustion of noncondensable gas can be prevented beforehand and reliably, the soundness of the apparatus and piping in a nuclear power station can be ensured, and reliability can be improved.

  Embodiments of a non-condensable gas accumulation combustion prevention system according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
A first embodiment of a non-condensable gas accumulation combustion prevention system according to the present invention will be described with reference to FIGS.

  FIG. 1 shows a schematic system diagram of a boiling water nuclear plant 10 equipped with a non-condensable gas accumulation combustion prevention system according to the present invention.

  The boiling water nuclear power plant 10 stores a reactor pressure vessel 12 in a reactor containment vessel 11. In the reactor containment vessel 11, the periphery of the reactor pressure vessel 12 is configured as a dry well 13. A reactor core 14 is stored in the reactor pressure vessel 12. The core 14 is immersed in reactor cooling water 15 as reactor water. A liquid phase part (reactor lower plenum) storing reactor cooling water 15 is formed at the lower part of the reactor pressure vessel 12, and a gas phase part (upper core plenum) 16 is formed above the liquid phase part. Is done.

  The reactor cooling water 15 in the reactor pressure vessel 12 is heated and vaporized by heat generated by a nuclear reaction when passing through the core 14. The generated gas-liquid two-layer reactor water vapor is separated into steam and water in the reactor pressure vessel 12 and dried, and then sent to the steam turbine 18 through the main steam system 17. The reactor steam works in the steam turbine 18 to drive a generator (not shown). Main steam isolation valves 19a and 19b are provided on the main steam pipe 17a constituting the main steam system 17 so as to isolate the inside of the reactor containment vessel 11 upstream and downstream of the reactor containment vessel 11, respectively. The reactor water vapor that has expanded by working in the steam turbine 18 is condensed in a condenser (not shown) and then recirculated into the reactor pressure vessel 12 through the reactor condensate / feed water system.

  The reactor pressure vessel 12 of the boiling water nuclear plant 10 is provided with a reactor pressure vessel top vent facility 20. The vent facility 20 includes a reactor pressure vessel vent system 21 and a branch vent system 23 branched from the reactor pressure vessel head spray system 22.

  The reactor pressure vessel vent system 21 has a reactor pressure vessel vent pipe 25 connected to the top of the reactor pressure vessel 12. The reactor pressure vessel vent pipe 25 is connected to a reactor pressure vessel head vent nozzle 26 formed at the top of the reactor pressure vessel 12, and an electric valve 27 that is remotely operated as an on-off valve is provided in the middle. The downstream side of the electric valve 27 is connected to the main steam pipe 17a on the upstream side of the main steam isolation valve 19a in the reactor containment vessel 11.

  Further, the branch vent system 23 includes a vent branch pipe 31 branched from the check valve of the reactor pressure vessel head spray pipe 28 or the downstream side of the injection valve 30. The vent branch pipe 31 is provided with an electric valve (open / close valve) 33 as a remote control valve. The downstream side of the electric valve 33 is connected to the reactor pressure vessel vent pipe 25 of the reactor pressure vessel vent system 21 on the upstream side of the electric valve 27. The branch portion of the vent branch pipe 31 is provided at the top position of the reactor pressure vessel head spray pipe 28 so as to rise from the downstream side of the check valve 30. The branch portion of the vent branch pipe 31 is provided at a position as close as possible to the check valve 30.

  Further, the reactor pressure vessel head spray system 22 is connected to a reactor pressure vessel head spray nozzle 35 provided at the top of the reactor pressure vessel 12 with a reactor pressure vessel head spray pipe 28. The reactor pressure vessel head spray piping 28 of the reactor pressure vessel head spray system 22 may also serve as the cooling water injection piping of the reactor isolation cooling equipment 38. The reactor isolation cooling facility 38 uses the cooling water in the shutdown cooling system to reduce the residual pressure in the upper dome of the reactor pressure vessel 12 when the boiling water reactor is shut down. This is a facility for cooling the gas phase portion 16 of the gas.

  On the other hand, the reactor pressure vessel head spray piping 28 of the reactor pressure vessel head spray system 22 is provided with a check valve (injection valve) 30 and reactor containment isolation valves 39a and 39b in the middle. The reactor containment isolation valves 39a and 39b are installed inside and outside the reactor containment vessel 11, respectively, and are normally closed during the operation of the reactor.

  By the way, the reactor pressure vessel vent system 21 constituting the reactor pressure vessel top vent facility 20 and the branch vent system 23 using the reactor pressure vessel head spray system 22 cooperate to operate around the reactor pressure vessel 12. The non-condensable gas can be derived from the non-condensable gas accumulation location 40 and discharged to the main steam pipe 17a.

  By providing the reactor pressure vessel vent system 21 and the branch vent system 23 using the reactor pressure vessel head spray system 22 at the top of the reactor pressure vessel 12 and causing them to cooperate, during normal operation of the nuclear power plant The non-condensable gas such as oxygen gas, hydrogen gas, krypton, and xenon radioactive noble gas at the gas accumulating location 40 that may accumulate near the top of the reactor pressure vessel 12 is smoothly supplied to the main steam pipe 17a side. And it can be discharged smoothly. That is, the non-condensable gas is prevented from being accumulated around the top of the reactor pressure vessel 12 without fail.

  In FIG. 1, the vent branch pipe 31 of the branch vent system 23 may be directly connected to the main steam pipe 17 a, or an orifice may be provided instead of the motor-operated valve 33, or on the upstream side of the motor-operated valve 33. Orifices may be provided.

  By the way, in the main steam system 17 for guiding the main steam generated in the reactor pressure vessel 12 to the steam turbine 18, a number of branch pipes 43 are branched from the main steam pipe 17a. For example, a reactor isolation cooling system, an emergency safety valve system, a turbine bypass system, and the like are branched. The branch pipe 43 exists in addition to the main steam system 17, and there are hundreds of lines per one nuclear power plant.

  In the branch pipe 43, as shown in FIG. 2, there is a dead end branch pipe (branch pipe) 45 that branches off from the main pipe 44 such as a main steam pipe. The branch pipe 45 is provided with an open / close valve 46 as a gate valve or a stop valve, and the open / close valve 46 isolates the mother pipe 44 and the branch pipe 45 from the surroundings.

  In the dead end branch pipe 45 that branches off from the mother pipe 44 and rises, a gas accumulation capable location 50 where the non-condensable gas 47 may accumulate is formed. The branch pipe 45 is provided with a bypass pipe 53 that bypasses the upstream and downstream of the on-off valve 46. The bypass pipe 53 is a pipe having a smaller diameter than the branch pipe 45. A bypass piping on / off valve 54 as a gate valve or a stop valve is provided in the middle of the bypass piping 53 to constitute a non-condensable gas accumulation combustion prevention system 55.

  The non-condensable gas accumulation combustion prevention system 55 configured as described above can constantly vent the vapor in the gas accumulation location 50 by the pressure difference between the upstream and downstream of the on-off valve 46, and is based on the condensation of the reactor water vapor. Accumulation of non-condensable gas 47 can be prevented.

  Next, treatment of non-condensable gas generated in the boiling water nuclear power plant 10 will be described.

  Non-condensable gases such as hydrogen gas and oxygen gas generated by neutron irradiation in the reactor pressure vessel 12 by the operation of the boiling water nuclear power plant 10 and decomposition of the cooling water are combined with the main steam system along with the reactor main steam. 17 is sent to the steam turbine 18. The main steam sent to the steam turbine 18 works here to drive a generator (not shown), while the non-condensable gas sent to the steam turbine 18 together with the main steam is subsequently guided to the condenser. The condenser is sent to a gas waste treatment system (not shown) for processing.

  By the way, during the operation of the boiling water nuclear power plant 10, the main steam is also caused to flow in the mother pipe 44 such as the main steam pipe shown in FIG. 2 (reactor steam flow). In the pipe connection structure of FIG. 2, since the dead end branch pipe 45 rising from the mother pipe 44 is connected, part of the main steam also flows into the branch pipe 45 branched from the mother pipe 44. The steam that has flowed into the branch pipe 45 tends to dissipate heat to the surrounding piping and the like to condense.

  However, in the non-condensable gas accumulation combustion prevention system 55 shown in FIG. 2, a bypass pipe 53 is provided in the rising branch pipe 45 branched from the mother pipe 44, and the bypass pipe on / off valve 54 is provided in the bypass pipe 53. Thus, it is possible to constantly vent the vapor of the gas accumulation location 50 by the pressure difference between the upstream and downstream of the on-off valve 46, and the accumulation of the non-condensable gas 47 due to the condensation of the reactor water vapor can be prevented.

  Therefore, since the vapor flowing into the gas accumulable location 50 is not condensed and liquefied, the generation amount of the non-condensable gas 47 at the gas accumulatable location 50 can be greatly reduced and suppressed. For this reason, it is possible to effectively and effectively prevent non-condensable gas from accumulating in the gas accumulable location 50, and to prevent the occurrence of combustion due to gas accumulation of non-condensable gas in advance. A high non-condensable gas accumulation combustion prevention system can be provided.

[Second Embodiment]
A second embodiment of the non-condensable gas accumulation combustion prevention system according to the present invention will be described with reference to FIG.

  In this embodiment, the same code | symbol is attached | subjected to the same structure as the non-condensable gas accumulation combustion prevention system of 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 3, in the dead end branch 45 that branches off from the mother pipe 44 and rises, a gas accumulation potential 50 in which the noncondensable gas 47 may accumulate is formed. A bypass pipe 53 that bypasses the upstream and downstream of the on-off valve 46 is provided in the branch pipe 45 of the gas accumulating location 50. The bypass pipe 53 is a pipe having a smaller diameter than the branch pipe 45. A bypass piping orifice 57 for adjusting the flow rate of the reactor water vapor is provided in the middle of the bypass piping 53 to constitute a non-condensable gas accumulation combustion prevention system 55A. The bypass piping orifice 57 can suppress an increase in leak potential by using, for example, a welding-type orifice.

  The non-condensable gas accumulation combustion prevention system 55A configured as described above can always ventilate the vapor of the gas accumulation location 50 by adjusting the flow rate by the pressure difference between the upstream and downstream of the on-off valve 46. Accumulation of non-condensable gas 47 due to condensation of water vapor can be prevented.

  Therefore, since the vapor flowing into the gas accumulable location 50 is not condensed and liquefied, the generation amount of the non-condensable gas 47 at the gas accumulatable location 50 can be greatly reduced and suppressed. For this reason, it is possible to effectively and effectively prevent non-condensable gas from accumulating in the gas accumulable location 50, and to prevent the occurrence of combustion due to gas accumulation of non-condensable gas in advance. A high non-condensable gas accumulation combustion prevention system can be provided.

[Third Embodiment]
A third embodiment of the non-condensable gas accumulation combustion prevention system according to the present invention will be described with reference to FIG.

  In this embodiment, the same code | symbol is attached | subjected to the same structure as the non-condensable gas accumulation combustion prevention system of 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 4, an open / close valve 46 is provided in a dead end branch pipe 45 that branches off from the main pipe 44, and the gas upstream side of the open / close valve 46 has a gas accumulation location 50 where non-condensable gas 47 can be accumulated. Configured as The piping material of the branch pipe 45 in the range A in which the gas accumulating portion 50 is configured among the pipe upstream side of the on-off valve 46 of the branch pipe 45 is made of a material having low thermal conductivity, so that non-condensable gas is used. An accumulated combustion prevention system 55B is configured.

  In the non-condensable gas accumulation combustion prevention system 55B configured in this way, in the pipe portion of the range A constituted by the material having low thermal conductivity in the branch pipe 45, the heat transfer from the steam transmitted through the pipe (steam Heat dissipation).

  Therefore, since the vapor | steam which flowed into the gas accumulation possible location 50 can suppress condensation, the generation amount of the non-condensable gas 47 of the gas accumulation possible location 50 can be reduced and suppressed significantly. For this reason, it is possible to effectively and effectively prevent non-condensable gas from accumulating in the gas accumulable location 50, and to prevent the occurrence of combustion due to gas accumulation of non-condensable gas in advance. A high non-condensable gas accumulation combustion prevention system can be provided.

[Fourth Embodiment]
A fourth embodiment of the non-condensable gas accumulation combustion prevention system according to the present invention will be described with reference to FIG.

  In this embodiment, the same code | symbol is attached | subjected to the same structure as the non-condensable gas accumulation combustion prevention system of 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 5, in the dead end branch 45 that branches off from the mother pipe 44 and rises, a gas accumulation capable location 50 in which the noncondensable gas 47 may accumulate is formed. A magnetic field generator 59 is provided outside the branch pipe 45 and in the vicinity of the gas storage location 50 to form a non-condensable gas storage combustion prevention system 55C.

  In addition, the piping material of the branch pipe 45 in the range where the gas accumulating portion 50 is configured in the pipe upstream side of the on-off valve 46 of the branch pipe 45 may be a material having low thermal conductivity.

  The non-condensable gas accumulation combustion prevention system 55C configured as described above provides the paramagnetism of the oxygen gas contained in the non-condensable gas 47 by applying a magnetic field to the condensable gas 47 by the magnetic field generator 59 from the outside of the pipe. The oxygen gas contained in the non-condensable gas 47 inside the pipe is convected to cause a flow in the non-condensable gas 47 mixed with the oxygen gas and reach the convection range of the mother pipe 44. Thus, the non-condensable gas 47 can be discharged to the mother pipe 44 side.

  Therefore, even if the non-condensable gas 47 is generated at the gas accumulable portion 50 by condensing and liquefying the vapor flowing into the gas accumulable portion 50, the non-condensable gas 47 can be discharged to the mother pipe 44. . For this reason, it is possible to effectively and effectively prevent non-condensable gas from accumulating in the gas accumulable location 50, and to prevent the occurrence of combustion due to gas accumulation of non-condensable gas in advance. A high non-condensable gas accumulation combustion prevention system can be provided.

[Fifth Embodiment]
A fifth embodiment of the non-condensable gas accumulation combustion prevention system according to the present invention will be described with reference to FIGS.

  In this embodiment, the same code | symbol is attached | subjected to the same structure as the non-condensable gas accumulation combustion prevention system of 1st Embodiment, and the overlapping description is abbreviate | omitted.

  The non-condensable gas accumulation combustion prevention system 55 </ b> D is an improvement of the on-off valve 55 provided in the branch pipe 45.

  As shown in FIG. 6, an opening / closing valve 46 </ b> A is provided in a dead end branch pipe 45 that branches off from the mother pipe 44 and the upstream side of the opening / closing valve 46 </ b> A has a gas accumulation location 50 where non-condensable gas 47 can be accumulated. Configured as As shown in FIG. 7, the on-off valve 46 </ b> A includes a valve body 62 housed in a valve casing 61, and the valve body 62 is opened and closed via a valve rod 64 by a valve operating portion 63. A catalyst 65 is provided on the valve upstream side of the valve body 62 of the on-off valve 46A to constitute a non-condensable gas accumulation combustion prevention system 55D.

  In addition, the piping material of the branch pipe 45 in the range in which the gas accumulating location 50 is configured in the piping upstream side of the on-off valve 46A of the branch pipe 45 is more than the piping material other than the gas accumulating location 50. A material having a low thermal conductivity can also be used.

  By this catalyst 65, the hydrogen gas and the oxygen gas contained in the non-condensable gas 47 accumulated in the gas accumulating location 50 are reacted and combined to return to water, thereby suppressing the accumulation of the high-concentration non-condensable gas 47. it can. The catalyst 65 can be a catalyst such as platinum.

  It should be noted that when the catalyst 65 is provided in the piping portion where the non-condensable gas 47 may accumulate, it is necessary to take measures such as making the piping a flange structure for maintenance of the catalyst 65. Since the on-off valve 46A itself requires maintenance at the time of regular inspection or the like, the catalyst 65 can be maintained along with the maintenance of the on-off valve 46A, and there is no influence such as an increase in leak potential on the piping side.

  Therefore, even if the non-condensable gas 47 is generated in the gas accumulable portion 50 by condensing and liquefying the vapor flowing into the gas accumulable portion 50, the non-condensable gas 47 is made non-condensable by the catalyst 65. Hydrogen gas or oxygen gas contained in the gas 47 does not burn rapidly. For this reason, it is possible to effectively and effectively prevent non-condensable gas from accumulating in the gas accumulable location 50, and to prevent the occurrence of combustion due to gas accumulation of non-condensable gas in advance. A high non-condensable gas accumulation combustion prevention system can be provided.

[Sixth Embodiment]
A sixth embodiment of the non-condensable gas accumulation combustion prevention system according to the present invention will be described with reference to FIG.

  In the present embodiment, the same components as those of the non-condensable gas accumulation combustion prevention system of the third embodiment and the fourth embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 8, an opening / closing valve 46 is provided in a closing branch pipe 45 </ b> A that branches off from the mother pipe 44, and the upstream side of the opening / closing valve 46 has a gas accumulation location 50 where non-condensable gas 47 can be accumulated. Configured as A pipe part upstream of the on-off valve 46 of the branch pipe 45A is a rising pipe part 67 that branches off from the main pipe 44 and rises, a substantially horizontal pipe part 68 that is connected to the rising part by an elbow, and this substantially horizontal pipe part. It is comprised by the piping part and the trap piping part 69 which is connected by the elbow and whose horizontal level is located below. The trap pipe section 69 is filled with water by condensed water of steam flowing into the branch pipe 45 or a water replenishment system (not shown) provided separately, thereby forming a non-condensable gas accumulation combustion prevention system 55E.

  The pipe portion on the upstream side of the on-off valve 46 of the branch pipe 45A may be formed by fixing the straight pipe member and the elbow member by a fixing method such as welding or by forming the integrated pipe by a forming process such as bending. Is also possible.

  In addition, the piping material of the substantially horizontal piping portion 68 of the branch pipe 45 in the range where the gas accumulating location 50 is configured in the pipe upstream side of the on-off valve 46 of the branch pipe 45 is made of a material having low thermal conductivity. It can also be used. In addition, a magnetic field generator 59 can be provided outside the branch pipe 45 and in the vicinity of the gas storage location 50.

  The non-condensable gas accumulation combustion prevention system 55E configured as described above can prevent the non-condensable gas 47 from entering the valve body of the on-off valve 46.

  Therefore, even if the non-condensable gas 47 is generated in the gas accumulable portion 50 by condensing and liquefying the vapor flowing into the gas accumulable portion 50, hydrogen gas or oxygen contained in the non-condensable gas 47 is generated. Gas does not flow into and accumulate in the valve body of the on-off valve 46, and ignition energy is applied in accordance with the operation of the on-off valve 46 so that rapid combustion does not occur. Further, when the on-off valve 46 is a check valve, the possibility of non-condensable gas 47 leaking to the upstream side of the check valve (downstream of the branch pipe 45A) by the seat path of the check valve is eliminated, and non-condensing is performed. Expansion of the accumulation range of the property gas 47 can be suppressed. Therefore, it is possible to reliably prevent the occurrence of combustion due to gas accumulation of non-condensable gas, and to provide a highly reliable non-condensable gas accumulation combustion prevention system.

1 is a system diagram schematically showing a boiling water nuclear power plant equipped with a non-condensable gas accumulation combustion prevention system according to the present invention. The figure which shows 1st Embodiment of the non-condensable gas accumulation combustion prevention system which concerns on this invention. The figure which shows 2nd Embodiment of the non-condensable gas accumulation combustion prevention system which concerns on this invention. The figure which shows 3rd Embodiment of the non-condensable gas accumulation combustion prevention system which concerns on this invention. The figure which shows 4th Embodiment of the non-condensable gas accumulation combustion prevention system which concerns on this invention. The figure which shows 5th Embodiment of the non-condensable gas accumulation combustion prevention system which concerns on this invention. The pipe axial direction longitudinal cross-sectional view which shows the outline of the on-off valve provided in the branch pipe of 5th Embodiment of the non-condensable gas accumulation combustion prevention system which concerns on this invention. The figure which shows 6th Embodiment of the non-condensable gas accumulation combustion prevention system which concerns on this invention. The figure which shows the piping connection structure which branches off from the conventional mother pipe and stands up.

Explanation of symbols

1, 44 Mother pipe 2, 45, 45A Branch pipe 3, 46, 46A On-off valve 5, 47 Non-condensable gas 4, 50 Gas storage location 10 Boiling water nuclear plant 11 Reactor containment vessel 12 Reactor pressure vessel 13 Drywell 14 Core 15 Reactor cooling water (liquid phase part)
16 Gas phase section 17 Main steam system 17a Main steam pipe 18 Steam turbine 19a, 19b Main steam isolation valve 20 Reactor pressure vessel vent facility 21 Reactor pressure vessel vent system 22 Reactor pressure vessel head spray system 23 Branch vent system 25 atoms Furnace pressure vessel vent piping 27, 33 Electric valve (remote control valve)
28 Reactor pressure vessel head spray piping 30 Check valve 31 Vent branch piping 38 Reactor isolation cooling equipment 39a, 39b Reactor containment isolation valve 40 Gas accumulation location 43 Branch pipe 53 Bypass pipe 54 Bypass pipe on / off valve 55, 55A, 55B, 55C, 55D, 55E Non-condensable gas accumulation combustion prevention system 57 Bypass piping orifice 59 Magnetic field generator 61 Valve casing 62 Valve body 63 Valve operation section 64 Valve rod 65 Catalyst 67 Rising piping section 68 Substantially horizontal piping section 69 Trap piping section

Claims (3)

A bypass pipe that connects the upstream side and the downstream side of the on-off valve provided in a gas accumulation-possible location where the non-condensable gas of the nuclear power plant may accumulate,
A bypass pipe opening / closing valve provided in the middle of the bypass pipe,
Use a material having a lower thermal conductivity than the piping material other than the gas accumulating location, to the piping material of the gas accumulating location,
By placing a magnetic field generator to the gas accumulation possible locations, the non-condensable gas by using the paramagnetic oxygen gas contained you characterized by flowing the said non-condensable gas non-condensable gases accumulate Combustion prevention system. The non-condensable gas accumulation combustion prevention system according to claim 1, wherein a catalyst is provided on a gas accumulating location side of a valve body of an on-off valve provided at the gas accumulating location. A part of the pipe on the gas accumulating location side of the on-off valve is configured at a position where the horizontal level is lower than the other part of the pipe, and water is supplied to the pipe part at a position where the horizontal level is lower than the other part. The non-condensable gas accumulation combustion prevention system according to claim 1 or 2 , characterized by satisfying.

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