JP5773710B2 - Reactor vessel structure and reactor operation method - Google Patents

Description

  The present invention relates to a reactor vessel structure applied to a fast reactor such as a fast breeder reactor (FBR) and a method for operating the reactor, and more particularly to a reactor vessel structure and a reactor suitable for a hot vessel. Relates to the driving method.

  Conventionally, a fast reactor such as a fast breeder reactor has a reactor vessel structure called a hot vessel as shown in FIG. In this reactor vessel 10, a liquid metal such as sodium is used as a coolant, and the liquid sodium Na flowing into the lower plenum 19 of the reactor vessel 10 from the cold leg pipe 17 </ b> C connected to the cooling system is shown in the figure. As shown by an arrow F in FIG. 2, it is heated while passing through the core 11 from the bottom to the top, and is used at a high temperature (about 550 ° C.) during rated operation. The heated liquid sodium Na is returned from the upper plenum 14 to the cooling system through the hot leg piping 17H.

  The illustrated reactor vessel 10 is an important device that constitutes the coolant boundary, and liquid sodium is used as an example of the coolant. In such a reactor vessel 10, in order to prevent sodium, which is a chemically active coolant, from coming into contact with air, an inert gas such as argon (Ar) is filled on top of liquid sodium Na. It has a liquid surface structure in which an active gas filling space G is provided. In addition, the code | symbol L in a figure has shown the liquid level of liquid sodium Na.

Further, the inside of the nuclear reactor vessel 10 described above is partitioned vertically by a partition wall 13 to form an upper plenum 14 and an intermediate plenum 18. The partition wall 13 prevents the high-temperature liquid sodium Na flowing into the upper plenum 14 from being heated from the core 11 from bypassing to the intermediate plenum 18, and lowering the installation part such as the skirt part 12 that supports the core 11 at a low temperature. Keep on.
The above-described inert gas is filled in the upper plenum 14. That is, the upper plenum 14 becomes a liquid surface space in the reactor vessel 10.
The roof deck 15 is cooled in order to keep the installation part of the reactor vessel 10 at a low temperature.
Further, reference numeral 30 in the drawing denotes an inert gas supply (filling) system that supplies an inert gas such as argon to the inert gas filling space G.

  For this reason, in the reactor wall 10a of the reactor vessel 10, as shown in “in the case of liquid level rise” in FIG. 7, the coolant wetted part where the liquid sodium Na exists and the inert gas filling space G In the meantime, a large temperature gradient is generated in the axial direction, and a high thermal stress is generated near the liquid surface of the coolant. This thermal stress becomes particularly large at the start-up of the reactor for the reasons explained below.

When the reactor is shut down, the liquid sodium Na is kept at about 200 ° C. for the purpose of preventing freezing of the liquid sodium Na used as a coolant.
On the other hand, when the nuclear reactor is started up, the temperature of the liquid sodium Na rises due to the heating from the core 11, so that the liquid level of the liquid sodium Na rises from L2 to L3 along with the volume expansion. In this case, the liquid level L3 is the coolant level during normal (steady) operation of the reactor.

  However, since the austenitic stainless steel, which is the material of the reactor vessel, has low thermal conductivity, the temperature follows in the region above the surface of the liquid sodium Na, that is, the region not in contact with the liquid sodium Na. Become slow. Accordingly, as indicated by the solid line in “in the case of rising of the liquid level” in FIG. 7, the reactor wall 10a of the reactor vessel 10 has a large temperature in the vicinity of the liquid level (a region slightly above the liquid level of the liquid level L3). Gradients create high thermal stresses.

As a conventional technique for relaxing the thermal stress generated on the wall surface of the reactor vessel (the reactor wall 10a described above), for example, as disclosed in Patent Document 1, an inner cylinder is installed inside the reactor vessel, and the vessel There is a reactor that cools the thermal stress on the reactor vessel wall (cold vessel) by flowing the coolant on the reactor core side between the inner cylinder and the inner cylinder and adjusting the flow rate of the coolant.
In Patent Document 2, in order to prevent the occurrence of the liquid surface thermal ratchet phenomenon, the electromagnetic pump installed in the reactor vessel is operated at the time of starting the reactor, and the liquid level of the liquid metal serving as the coolant is changed. A fast reactor is disclosed.

  Moreover, the following patent documents 3 to 5 disclose a method of reducing thermal stress by providing a storage bucket for storing coolant (liquid sodium) in the vicinity of the coolant level of the reactor vessel. There are also a structure in which a plurality of thermal resistors are accommodated in the storage bucket and a structure in which the cross-sectional area of the storage bucket is different between the upper part and the lower part.

JP-A-10-160883 JP-A-8-15487 JP 59-163588 A JP 60-247191 A JP 61-47581 A

  As described above, in the reactor vessel structure of the hot vessel, the temperature of the liquid sodium Na rises at the time of startup of the nuclear reactor, and the liquid level L of the liquid sodium Na also rises due to the thermal expansion associated therewith. In such a reactor wall 10a of the nuclear reactor vessel 10, in the case of “increase in liquid level” shown in FIG. 7, a large temperature gradient is generated in the axial direction in the vicinity of the liquid level of liquid sodium Na. Will be big.

For this reason, during the operation period of the nuclear reactor, the above-described thermal stress is repeatedly generated in the nuclear reactor vessel 10 by repeatedly starting and stopping. Therefore, when this thermal stress is large, there is a concern about the deformation (liquid level ratchet) in which the diameter of the reactor vessel 10 is reduced every time the reactor vessel 10 is started up or the occurrence of breakage due to creep fatigue.
Furthermore, in order to ensure the soundness of the reactor vessel 10, it is necessary to start up slowly so that the number of days required for startup is increased and the reactor wall 10 a gradually increases in temperature. However, when the nuclear reactor is used for commercial operation such as power generation, it is desirable to shorten the time required for startup and extend the rated operation time as much as possible.
Concerns due to such thermal stress occur not only at the time of startup, but also at the time of normal stop and emergency stop.

From such a background, in the reactor vessel structure of a hot vessel, in order to further improve the reliability and operability of the reactor vessel, a measure to alleviate the thermal stress generated on the wall of the reactor vessel is required. . It is desirable that this measure minimizes additional equipment and has high heat resistance and safety.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a reactor vessel structure and a reactor that can relieve the thermal stress of the reactor vessel wall surface that is generated when the reactor is started up. It is to provide a driving method.

In order to solve the above problems, the present invention employs the following means.
The reactor vessel structure according to the present invention is provided with a liquid surface space in which an inert gas filling space is formed in an upper portion of a liquid surface filled with a liquid metal coolant in a reactor vessel containing a reactor core, A coolant formed between the vessel wall surface and the bottomed inner cylinder by installing a bottomed inner tube inside the vessel wall surface of the liquid surface space up to a position higher than the coolant level during steady operation of the reactor A reactor vessel structure having a retention tank, which is fixedly supported on the lower surface of a roof deck that forms the upper surface of the liquid surface space inside the bottomed inner cylinder and spaced apart in the axial center direction of the reactor vessel And a lower end portion of the partition member is extended into the liquid surface of the liquid surface space that is most lowered by a change in the coolant level in a series of reactor operation states. It divides the interior to the inner space and outer space, before being connected to the inert gas supply system An inert gas is supplied to the inner space and a first gas pipe provided with a first on-off valve, and an inert gas is branched from the first gas pipe on the upstream side of the first on-off valve and supplied to the outer space. And a second gas pipe provided with a second on-off valve, and the liquid metal relatively changes the inert gas filling pressure in the inner space and the outer space when filling in preparation for reactor startup is completed. The coolant staying tank is filled using the pressure difference generated by the above.

According to such a reactor vessel structure, the partition member fixedly supported on the lower surface of the roof deck that forms the upper surface of the liquid surface space is formed on the inner side spaced from the bottomed inner cylinder in the axial center direction of the reactor vessel. The lower end of the partition member is extended to the liquid level of the liquid level space that is the lowest when the coolant level changes in a series of reactor operation states, and the inside of the liquid level space is defined as the inner space and the outer space. A first gas pipe connected to an inert gas supply system to supply an inert gas to the inner space and having a first on-off valve, and branched from the first gas pipe upstream of the first on-off valve Then, an inert gas is supplied to the outer space and a second gas pipe having a second on-off valve is provided, and when the filling for the reactor start-up preparation is completed, the liquid metal is filled with the inert gas in the inner space and the outer space. Use pressure difference generated by relatively changing pressure Since the coolant retention tank is filled, liquid metal is filled in the coolant retention tank in the reactor vessel, so that special consideration is required so that the liquid metal does not come into contact with air. There is no need to add a new one.

  Then, the inert gas filling pressure in the internal space is set higher than that in the external space, and the liquid level in the internal space is pushed down and the liquid level in the external space is raised by this pressure difference to fill the coolant retention tank with liquid metal. Therefore, the liquid metal can be reliably filled up to the upper end of the coolant retention tank, and at the time of start-up of the nuclear reactor, the liquid sodium Na expanded by the temperature rise is from the coolant retention tank to the upper plenum having a low liquid level. By overflowing into the reactor, the liquid level of the coolant in contact with the wall of the reactor vessel is maintained at a fixed position where it coincides with the upper end of the coolant retention tank.

Furthermore, in the above reactor vessel structure, the first gas pipe connected to the inert gas supply system to supply the inert gas to the inner space and provided with the first on-off valve, and the upstream side from the first on-off valve And a second gas pipe provided with a second on-off valve while supplying an inert gas to the outer space by branching from the first gas pipe, and the pressure difference by opening and closing the first on-off valve and the second on-off valve. As a result, it is possible to easily fill the coolant retention tank in the reactor vessel with liquid metal in preparation for start-up, etc. with a relatively simple structure in which a partition member is additionally installed and the inert gas supply system is changed. Can do.

  In the reactor vessel structure described above, it is preferable to include a liquid level detection unit that detects the liquid level in the inner space and the outer space, thereby controlling the liquid level in the inner space and the outer space. Since it becomes possible, the coolant retention tank can be reliably filled with the liquid metal.

A nuclear reactor operation method according to the present invention is a nuclear reactor operation method including the above-described nuclear reactor vessel structure , wherein the inert gas filling pressure in the internal space is set to a pressure higher than that in the external space, A starting preparation step is provided in which the liquid level in the internal space is pushed down and the liquid level in the external space is raised to fill the coolant retaining tank with the liquid metal.

  According to such a reactor operating method, the inert gas filling pressure in the internal space is set to a pressure higher than that in the external space, the liquid level in the internal space is pushed down and the liquid level in the external space is raised to retain the coolant. Since it has a start-up preparation process that fills the tank with liquid metal, it is possible to start operation in a state in which the liquid metal is reliably filled up to the upper end of the coolant retention tank using the pressure difference generated in both spaces. . For this reason, when the reactor is started up, the liquid sodium Na expanded by the temperature rise overflows from the coolant retention tank into the lower plenum of the liquid level, so that the coolant liquid in contact with the wall of the reactor vessel The surface height is maintained at a fixed position that coincides with the upper end of the coolant retention tank.

According to the present invention described above, when the reactor is started up, the liquid sodium Na expanded by the temperature rise overflows from the coolant retention tank into the upper plenum having a low liquid level, thereby contacting the wall of the reactor vessel. The liquid level of the coolant is kept at a constant position that coincides with the upper end of the coolant retention tank. As a result, the thermal stress generated by relaxing the temperature gradient in the axial direction is reduced on the wall of the reactor vessel, so that a remarkable effect of further improving the reliability and operability of the reactor vessel can be obtained. .
Further, the present invention described above can be implemented by changing the container structure to which a bottomed inner cylinder and a partition member are added, and by simply remodeling the inert gas supply system, so that additional equipment is minimized and high heat resistance is achieved. Has feasibility. In particular, since there is no need to add a liquid metal (coolant) pipe such as sodium, which requires measures to prevent contact with air, it is highly effective in improving plant reliability and durability.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment of the reactor vessel structure which concerns on this invention, (a) is a longitudinal cross-sectional view which shows the outline | summary (liquid level at the time of normal operation) of a reactor vessel structure, (b) is A of (a). It is -A sectional drawing. FIG. 2 is a longitudinal sectional view showing a coolant level at a normal stop in the reactor vessel structure of FIG. 1. FIG. 2 is a longitudinal sectional view showing a liquid level at the start of filling of a coolant into a coolant retention tank in the reactor vessel structure of FIG. 1. FIG. 2 is a longitudinal sectional view showing a liquid level at the completion of filling of a coolant into a coolant retention tank in the reactor vessel structure of FIG. 1. FIG. 2 is a longitudinal sectional view showing a liquid level when filling of a coolant into a coolant retention tank is completed in the reactor vessel structure of FIG. In coolant filling with respect to a coolant retention tank, it is explanatory drawing of the inert gas pressure operation which showed the inert gas pressure corresponding to the reactor operation state of a horizontal axis on the vertical axis | shaft. It is a figure which shows the temperature gradient of a reactor vessel wall surface about the case where the coolant level in a reactor vessel is "a liquid level rise" and "a case where a liquid level is constant." It is a longitudinal cross-sectional view which shows the example of the conventional reactor vessel structure.

In the following, an embodiment of a reactor vessel structure and a reactor operating method according to the present invention will be described with reference to the drawings.
The reactor vessel 10A of the embodiment shown in FIG. 1 is called a hot vessel applied to a fast reactor such as a fast breeder reactor, and stores the core 11 in the internal space of the reactor wall 10a. The core 11 is supported by an installation portion such as a skirt portion 12 in the reactor vessel 10A.

Inside the reactor vessel 10 </ b> A, a partition wall 13 is provided on the upper end side of the core 11 to form an upper plenum 14 and an intermediate plenum 18. A lower plenum 19 partitioned by the skirt portion 12 is formed below the intermediate plenum 18.
The upper plenum 14 is a space in which a coolant such as liquid sodium Na, which is a liquid metal, is filled, and an inert gas filling space G such as argon is formed above the liquid surface of the liquid sodium Na. It becomes the space region of the liquid surface structure provided in 10A. Like the conventional structure described above, liquid sodium Na flows from a cold leg pipe (not shown) into the lower plenum 19 of the reactor vessel 10A and is heated in the process of passing through the core 11 from below to above. The upper plenum 14 is returned to the cooling system through hot leg piping.

  An inner cylinder 20 attached inside the reactor wall 10a is provided in the reactor vessel 10A. The inner cylinder 20 has an inner cylinder bottom surface 21 formed by coupling the lower end side to the furnace wall 10a. Thus, since the inner cylinder 20 of the bottomed inner cylinder having the inner cylinder bottom surface 21 having a smaller diameter than the reactor wall 10a is installed inside the reactor vessel 10A, the inner side of the reactor wall 10a and the inner cylinder 20 A coolant retention tank 22 that is a space for retaining liquid sodium Na, which is a coolant, is formed between the outer wall surface.

The inner cylinder 20 is provided up to a position higher than the coolant level L3 in the normal (steady) operation of the reactor in the upper plenum 14 of the liquid surface space described above.
The lower end portion of the inner cylinder 20 and the inner cylinder bottom surface 21 are not desirably adjacent to the upper plenum 14 where thermal transients during severe reactor trips are severe, and therefore are provided on the intermediate plenum 18 side slightly below the partition wall 13. Yes.

The illustrated reactor vessel 10A is an important device that constitutes the coolant boundary, and liquid sodium Na is used as an example of the coolant. In this case, it is necessary to prevent the liquid sodium Na from becoming a low temperature of about 200 ° C. or less in order to prevent freezing. Therefore, the liquid sodium Na is heated and kept warm according to the operating conditions. In addition, the inside of the reactor vessel 10A is an inert gas in which an upper part of liquid sodium Na is filled with an inert gas such as argon (Ar) in order to prevent sodium, which is a chemically active coolant, from coming into contact with air. It has a liquid surface structure in which an active gas filling space G is provided.
With respect to the inside of such a nuclear reactor vessel 10A, in the present embodiment, the inner side of the inner cylinder 20 is spaced apart from the inner cylinder 20 so as to form a gap that allows a smooth flow of liquid sodium Na. A partition member 25 having a small-diameter cylindrical shape is provided. The partition member 25 is provided so that the upper end side is fixedly supported on the lower surface of the roof deck 15 and the lower end portion extends below a coolant level L5 (see FIG. 4) at the time of filling described later. .

  That is, the length of the partition member 25 is the most liquid level change in the coolant level change in a series of reactor operation states (normal operation, normal stop, filling start, filling completion, and startup preparation completion) described later. It is set so that the lower end portion always enters the liquid surface of the liquid sodium Na when the filling of the surface is lowered. At this time, the lower end of the partition member 25 does not need to penetrate deeply into the liquid level of the liquid sodium Na, and is filled with the inert gas formed inside the upper plenum 14 even when filling is completed when the liquid level is the lowest. It is only necessary that the space G can be divided into the inner space Gi and the outer space Go.

  Such an inner space Gi and an outer space Go are closed spaces. Therefore, by changing the inert gas filling pressure between the two spaces relatively, a pressure difference generated in the two spaces is used to make the coolant retention tank 22. It is possible to fill the coolant (liquid metal). That is, when the inert gas filling pressure in the inner space Gi and the outer space Go is relatively changed, the liquid level of the liquid sodium Na changes due to the pressure difference generated in both spaces. Thus, the coolant liquid sodium Na can be filled up to the upper end of the coolant retention tank 22.

In this embodiment, the inert gas supply space G branches off from the inert gas supply (filling) system 30 that supplies an inert gas such as argon, that is, the inert gas is supplied to the inner space Gi. A second gas pipe 32 for supplying an inert gas to the outer space Go is additionally provided so as to branch from the first gas pipe 31. The first gas pipe 31 and the second gas pipe 32 are provided with a first on-off valve 33 and a second on-off valve 34 in order to enable independent supply of inert gas.
Note that an inert gas pressurizing compressor (not shown) is provided at an appropriate position of the inert gas supply system 30.

In other words, the pressure difference between the inner space Gi and the outer space Go described above is the first gas that is connected to the inert gas supply system 30 to supply the inert gas to the inner space Gi and includes the first on-off valve 33. A pipe 31 and a second gas pipe 32 branched from the first gas pipe 31 upstream of the first on-off valve 33 to supply an inert gas to the outer space Go and provided with a second on-off valve; It can be generated by opening / closing the first opening / closing valve 33 and the second opening / closing valve 34.
Thus, the reactor vessel structure of the present embodiment is different from the reactor vessel 10A provided with the coolant retention tank 22 with respect to the partition member 25, the second gas pipe 32, the first on-off valve 33, and the first By adding the 2 on-off valve 34, the liquid metal of the coolant can be filled up to the upper end of the coolant retention tank 22.

Hereinafter, the procedure for filling the coolant retention tank 22 with liquid sodium Na will be described together with a series of reactor operation states (normal operation, normal stop, filling start, filling completion, and startup preparation completion).
During normal operation of the nuclear reactor shown in FIG. 1, an inert gas set at a pressure P ₀ is supplied from an inert gas supply system 30. In this case, the first on-off valve 33 and the second on-off valve 34 is either opened, therefore, within the inner space Gi and the outer space Go are both maintained at P ₀ of the same pressure. Note that the liquid sodium Na level during normal operation is L3, and the coolant retention tank 22 is filled with liquid sodium Na up to the upper end.

Such a state during normal operation is continued up to point A in the explanatory view of the inert gas pressure operation showing the relationship between the reactor operation state and the inert gas pressure (see FIG. 6).
In FIG. 1 to FIG. 5, the first on-off valve 33 and the second on-off valve 34 are displayed in black in the fully closed state.

When the nuclear reactor shown in FIG. 2 is normally shut down, the liquid sodium Na level in the inner space Gi, the outer space Go, and the coolant retention tank 22 decreases as the temperature decreases. Along with the lowering of the liquid level, the pressure of the inert gas supply system 30 is reduced from P ₀ to P ₁ for maintenance work. That is, in the inert gas pressure operation of FIG. 6, the reactor operating state changes from point A to point B.
In this case, since both the first on-off valve 33 and the second on-off valve 34 are open, the insides of the inner space Gi and the outer space Go are maintained at P ₁ having the same pressure. Further, the coolant level in the internal space Gi decreases to L2.

When the filling of the nuclear reactor shown in FIG. 3 is started, liquid sodium Na is replenished up to the upper end portion of the coolant retention tank 22 whose liquid level has been lowered during the normal stop. That is, in the inert gas pressure operation shown in FIG. 6, the reactor operating state is maintained after maintaining the pressure P ₁ while keeping the liquid sodium Na from point B to point C by maintenance work or the like, and then cooled. Coolant filling into the material retention tank 22 is started. At this time, the second on-off valve 34 of the second gas pipe 32 is fully closed, and the pressure of the inert gas supply system is increased from P ₁ to P ₂ .

When the coolant filling is started in this way, in the inert gas pressure operation of FIG. 6, the pressure of the inert gas is changed from the point C (FIG. 2) before the start of the coolant filling to the region C ′ (FIG. 3) during the coolant filling. ) To change to a point D (FIG. 4) of completion of coolant filling.
As a result, a pressure difference is generated between the inner space Gi that is a closed space and the outer space Go, and the liquid level is reduced to the coolant level L4 in the inner space Gi on the high pressure side (pressure P ₂ ). The liquid level rises in the outer space Go of (pressure P ₁ ). This is because the inner space Gi and the outer space Go communicate with each other, and the flow of the liquid sodium Na is possible, and the outer side is the volume of the liquid sodium Na whose liquid level is reduced in the inner space Gi. The liquid level in the space Go rises.

  Due to such a change in the liquid level, the liquid sodium Na in the outer space Go reaches the upper end of the coolant retention tank 22 and further flows into the coolant retention tank 22. As a result, by adjusting the pressure of the inert gas filling system 30, the liquid sodium Na can be filled into the coolant retaining tank 22 whose liquid level has been lowered, and finally the state at the completion of filling shown in FIG. Become. For adjusting the pressure of the active gas filling system 30, an inert gas pressurizing compressor originally provided in the inert gas supply system 30 may be used.

Filling completion time of 4 point D becomes the inert gas pressure operation of FIG. 6, the pressure of the inert gas supply system 30 is maintained at P _2.
Therefore, the internal pressure of the inner space Gi is P _2, and the internal pressure in the external space Go to the second on-off valve 34 fully closed are isolated from the inert gas supply system 30, the internal pressure P ₂ from the internal space Gi side by receiving the impact increases from _{P 1} to _{P 1} '. That is, in the inert gas pressure operation diagram of FIG. 6, when the pressure change is different from the internal space Gi, the pressure change in the external space Go is indicated by a one-dot chain line in the drawing.

And the operating method of the nuclear reactor provided with the reactor vessel structure of this embodiment sets the inert gas filling pressure of the internal space Gi to a pressure higher than the external space Go, pushes down the liquid level of the internal space Gi and externally A startup preparation step of raising the liquid level of the space Go and filling the coolant retention tank 22 with liquid sodium Na is provided.
According to such a method of operating the nuclear reactor, the pressure difference generated in the internal space Gi and the external space Go is used, and the liquid sodium Na as a coolant is reliably filled up to the upper end portion of the coolant retention tank 22. The furnace can be started. As a result, when the reactor is started up, the liquid sodium Na expanded by the temperature rise overflows from the coolant retention tank 22 into the upper plenum 14 having a low liquid level, and thus the reactor wall 10a of the reactor vessel 10A The liquid level of the coolant in contact with the coolant is kept at a fixed position that coincides with the upper end of the coolant retention tank 22.

When the filling of the coolant is completed in this way, the state at the time of filling is maintained from point D to point E in the inert gas pressure operation of FIG. Thereafter, the inner space Gi and the outer space Go both pressure P ₂ becomes when fully opened the second on-off valve 34 from the filling completion time of state described above, when the further increase the pressure of the inert gas supply system 30 to P ₀ FIG. 6 shows a state at the completion of the start-up preparation indicated by a point F.
At this time, since the liquid sodium Na is kept warm, there is no temperature change, and the coolant staying tank 22 is filled with the liquid sodium Na up to the upper end. Moreover, the coolant level L6 in the upper plenum 14 excluding the inside of the coolant retention tank 22 is slightly higher than the coolant level L5 at the completion of filling shown in FIG.

According to the reactor vessel structure of the present embodiment as described above, by providing the partition member 25 with the lower end portion extending to the coolant level at the completion of filling, on the inner side separated from the bottomed inner cylinder 20 When the inside of the inert gas filling space G that becomes the liquid surface space is divided into the inner space Gi and the outer space Go, and the liquid sodium Na, which is the liquid metal serving as the coolant, is filled in the coolant retention tank 22, Filling using a pressure difference generated by relatively changing the inert gas filling pressure in the inner space Gi and the outer space Go becomes possible.
For this reason, liquid sodium Na can be easily and safely filled into the coolant retention tank 22 in the reactor vessel 10A as preparation for starting up the reactor. That is, there is no need to newly add a liquid metal supply pipe of liquid sodium Na that requires sufficient consideration so that the liquid metal does not come into contact with air, and an additional partition member 25 and a simple modification of the inert gas supply system 30 By implementing the above, measures against thermal stress of the reactor wall 10a, which becomes a problem particularly at the time of startup of the reactor, are realized.

  This thermal stress countermeasure will be described in detail. When the start-up preparation shown in FIG. 5 is completed, if liquid sodium Na is filled up to the upper end of the coolant retention tank 22 before the start-up of the nuclear reactor, Liquid sodium Na expanded by the temperature rise overflows from the coolant retention tank 22 into the upper plenum 14 having a low liquid level. Therefore, when the nuclear reactor is started up, the liquid level of liquid sodium Na in contact with the wall surface of the reactor vessel 10A coincides with the upper end of the coolant retention tank 22, and is kept constant without fluctuation until normal operation.

By the way, it is desirable that the reactor vessel 10A described above includes a liquid level detection unit (not shown) that detects the liquid level in the inner space Gi and the outer space Go. That is, in order to detect the liquid level of the liquid sodium Na that changes in the internal space G, for example, a liquid level sensor is installed on the wall surface of the partition member 25 or the inner cylinder 20 and used to adjust the pressure of the inert gas supply system 30. That's fine.
Specifically, the liquid level of the liquid sodium Na that changes in the internal space G is detected stepwise or continuously, and it is confirmed that the liquid level has changed to the predetermined liquid level corresponding to the above-described reactor operating state. Then, the operation control of the inert gas pressurizing compressor can be reliably performed. That is, since the liquid level in the inner space G can be accurately managed, the coolant staying tank 22 can be reliably filled with the liquid sodium Na as the coolant.

In this way, when the liquid sodium Na level in contact with the reactor wall 10a can be kept constant at the time of starting the reactor, the liquid level of the liquid sodium Na can be obtained as shown in FIG. A large temperature gradient generated in the axial direction in the vicinity can be reduced, and as a result, the thermal stress in the vicinity of the liquid surface is also reduced.
For this reason, even if the start / stop is repeated during the operation period of the reactor, the thermal stress repeatedly generated on the reactor vessel 10A can be reduced. Therefore, the deformation (liquid) The problem of breakage due to surface ratchet) or creep fatigue can be reduced or eliminated.
Further, by providing the coolant retention tank 22, not only at the time of start-up described above but also at the time of normal stop or emergency stop when the volume of liquid sodium Na contracts, the liquid sodium Na level in contact with the furnace wall 10a is reduced. The drop width can be reduced, and the concern due to thermal stress such as the thermal stress in the vicinity of the liquid level can be reduced.

  Further, in the embodiment described above, as an additional facility with respect to the conventional example shown in FIG. 8, the inner cylinder 20 having the inner cylinder bottom surface 21 and the partition member 25 are additionally provided, and the inert gas for supplying the inert gas to the upper plenum 14 is provided. Only the gas filling system 30 is modified. That is, it is only necessary to add the cylinder 20 and the partition member 25 having a simple structure in the reactor vessel 10A, and the modification of the inert gas filling system 30 is not a large-scale structure with a simple configuration. It can be easily implemented at a low cost.

  According to the reactor vessel structure of the present embodiment described above, the liquid level height of the liquid sodium Na in contact with the reactor wall 10a of the reactor vessel 10A is always the upper end of the coolant retention tank 22 when the reactor is started. It is kept in a constant position that matches. As a result, on the wall surface of the reactor vessel 10A, the thermal stress generated due to the relaxation of the temperature gradient in the axial direction is reduced, so that a remarkable effect of further improving the reliability and operability of the reactor vessel is obtained. It is done.

  Moreover, since this embodiment mentioned above can be implemented by the change of the container structure which adds a partition member to a bottomed inner cylinder, and simple modification of an inert gas supply system, additional equipment is minimized and high Has heat resistance. In particular, since there is no need to add a liquid metal (coolant) pipe such as sodium, which requires measures to prevent contact with air, it is highly effective in improving plant reliability and durability.

  In addition, when the coolant retention tank 22 is filled with the liquid metal of the coolant using the pressure difference generated by relatively changing the inert gas filling pressure in the inner space Gi and the outer space Go, the pressure difference is formed. The pressure increase is not limited to the inner space Gi side, and for example, reverse pressure adjustment may be performed so as to reduce the pressure on the outer space Go side.

Moreover, this embodiment mentioned above is applicable also when filling a coolant in the storage bucket as described in patent documents 3-5, for example.
Note that the present invention is not limited to the above-described embodiment, and may be appropriately changed within a range not departing from the gist thereof, such as the type of coolant and inert gas, the configuration of the coolant filling system, and the filling / recovery procedure. can do.

10A Reactor vessel 10a Reactor wall 11 Core 12 Skirt part 13 Bulkhead 14 Upper plenum 15 Roof deck 20 Inner cylinder 21 Inner cylinder bottom 22 Coolant retention tank 25 Partition member 30 Inert gas filling system 31 First gas piping 32 Second gas Piping 33 First open / close valve 34 Second open / close valve G Inert gas filling space Gi Internal space Go External space

Claims (3)

In the reactor vessel containing the reactor core, a liquid surface space in which an inert gas filling space is formed at the upper part of the liquid surface filled with the liquid metal coolant is provided, and inside the vessel wall surface of the liquid surface space, Reactor vessel structure having a bottomed inner cylinder installed up to a position higher than the coolant level during steady-state operation of the reactor and provided with a coolant retention tank formed between the vessel wall surface and the bottomed inner cylinder Because
A partition member fixed and supported on the lower surface of the roof deck that forms the upper surface of the liquid surface space is provided inside the bottomed inner cylinder in the axial center direction of the reactor vessel, and a lower end portion of the partition member is provided. The inside of the liquid surface space is divided into an inner space and an outer space by extending into the liquid surface of the liquid surface space that is the lowest when the coolant level changes in a series of reactor operation states ,
A first gas pipe connected to an inert gas supply system to supply an inert gas to the inner space and having a first on-off valve, and branched from the first gas pipe upstream of the first on-off valve. Providing an inert gas to the outer space and a second gas pipe provided with a second on-off valve,
Upon completion of preparation for reactor start-up, the liquid metal is filled into the coolant retention tank using a pressure difference generated by relatively changing the inert gas filling pressure in the inner space and the outer space. A reactor vessel structure characterized by that. The reactor vessel structure according to claim 1 , further comprising a liquid level detection unit that detects a liquid level in the inner space. A method of operating a nuclear reactor comprising the reactor vessel structure according to claim 1 or 2 ,
Set the inert gas filling pressure in the inner space at a higher pressure than the outer space, filling the liquid metal the raises the liquid surface of the outer space with push down the liquid surface of the inner space to the coolant residence tank A reactor operating method comprising a startup preparation step.

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