JPH01129195A - Roof slab of fast breeder - Google Patents

Abstract

PURPOSE:To flatten the temperature distribution of roof slabs and prevent thermal deformation by dividing the roof slabs into three chambers, filling coolant in an upper stage chamber and radio-active ray shielding concrete in a middle stage chamber and penetrate-three chambers by heat tubes. CONSTITUTION:Heat intruded in a lower stage chamber 23 through a heat insulating structure 19 is conducted to an upper stage chamber 25 through a heat tube 28, transmitted to coolant fed from a header 26 and exhausted out of roof slabs from a return header 27. Since the heat insulating structure 19 has low heat conductivity and the heat tube 28 has good heat conductivity, the axial temperature distribution has a distribution in which axial temperature difference of a box structure 20 including strength members of the roof slabs is lessened. Circumferential temperature distribution is moderated because many heat tubes 28 are provided and heat is removed by the coolant uniformly flowed out from circumferentially provided headers 26, 27.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a roof slab for a fast reactor that closes a reactor vessel of the fast reactor.

(Prior Art) A roof slab for closing the reactor vessel is provided at the upper part of the reactor vessel of a fast breeder reactor, and the core upper mechanism, intermediate heat exchanger, etc. are supported by this roof slab.

However, the bottom surface of this roof slab is exposed to the high temperature inside the furnace, and the top surface is at room temperature because people enter it. As a result, temperature distribution occurs in the axial direction, resulting in thermal deformation and thermal stress. Conventionally, to prevent this, a heat insulating material was installed on the bottom surface, and a box-shaped structure as a strength member was installed on top of it. A complex labyrinth was formed inside for cooling, through which a coolant such as nitrogen gas or air was passed.

(Problem to be solved by the invention) However, in this method, there is a temperature difference between the entrance and exit of the maze, so a temperature distribution also occurs in the roof slab, causing thermal deformation and thermal stress, and damage in the maze. There are other problems, such as the possibility that the labyrinth may occur or blockage of the flow path, and that the manufacturing cost increases to form a more complex labyrinth.

In view of these points, the present invention alleviates unevenness in the temperature distribution of the roof slab, which causes thermal deformation and thermal stress in the roof slab, and multiplexes cooling channels.

The object of the present invention is to provide a fast reactor roof slab that is simplified, has improved reliability against flow path damage, blockage, etc., and is easy to manufacture.

[Structure of the invention]

(Means for solving the problem) This purpose is to create a fast reactor that is installed to close off the top surface of the fast reactor, with a heat insulating material installed on the bottom surface, and a box-shaped structure as a strength member installed on the top. In the roof slab, three rooms are formed in the height direction within the box-shaped structure, the middle room is filled with concrete for radiation protection, and heat pipes are installed to penetrate the three rooms. This is achieved by installing and flowing coolant into the upper chamber.

(Function) With this configuration, the heat on the lower surface of the roof slab is transmitted to the upper surface by the heat pipe, and the heat is radiated on the upper surface, so that thermal deformation of the roof slab can be achieved with a simple structure.

(Example) An example of the present invention will be described below with reference to one drawing.

In FIG. 1, a fast reactor 1 is supported on a pedestal 2 by a cylindrical support 4 fitted around a roof slab 3. Further, the upper end of the reactor vessel 5 is fixed around the roof slab 3, and the inside of the roof slab 3 is provided with a large rotating plug 8 that is rotated when replacing the fuel in the reactor core 7. At the same time, a rotatable small rotation plug 9 is provided, and further inside thereof, a core upper mechanism 12 is arranged in which a control rod guide tube 1o extending into the reactor core and a control rod 11 inserted therein are mounted. There is. In addition, the roof slab 3 also includes an intermediate heat exchanger 13 that transfers the heat emitted from the core to the secondary sodium system, and a mechanical pump 1 that circulates the sodium in the reactor.
4 etc. are installed and supported in large numbers. A partition wall 17 that partitions a high temperature sodium section 15 and a low temperature sodium section 16 in the furnace is provided in the middle part of the furnace, and the roof slab 3 is
To prevent the mounted equipment from tilting and applying unreasonable deformation or stress to the bulkhead 17 and the seal 18 between it and the mounted equipment, prevent it from being deformed by stress during an earthquake or by vibration of the roof slab. It has a rigid structure to avoid large fluctuations in the fast reactor output due to changes in the insertion position of the control rods into the reactor core.

FIG. 2 is a cross-sectional view of the loop slab, which is a box-shaped structure 2 with a heat insulating structure 19 provided at the bottom to avoid thermal deformation of the box-shaped structure 20, which is a strength member of the roof slab.
The inside of 0 consists of three rooms with partition plates 21 and 22, and multiple heat pipes are installed to penetrate these three rooms, and the middle room 24 is filled with concrete to prevent radiation. has been done. In the upper room 25, a coolant supply header 26 and a cooling unit return header 27 are installed to flow the coolant, and the coolant enters the lower room 23 (gas inside this room) through the insulation structure 19. The heat is transmitted to the upper room 25 through the heat pipe 28,
The heat is transferred to the coolant supplied from the header 26 and taken out from the header 27 to the outside of the roof slab.

With regard to the axial temperature distribution of the roof slab configured in this way, the heat that has passed through the heat insulating structure 19 is first transferred to the lower room 23, then transferred to the upper room 26 by the heat pipe 28, and this heat is It is removed by coolant supplied and discharged from the header.

Here, since the thermal insulation structure has poor thermal conductivity and the heat pipe has good thermal conductivity, the axial temperature distribution is as shown in Figure 3. Temperature differences can be reduced, and therefore thermal deformation and thermal stress of the box-shaped structure can be prevented. In addition, the temperature distribution in the circumferential direction is eased by the provision of a large number of heat pipes and the removal of heat by the coolant that flows out uniformly from the headers provided in the circumferential direction.
It is also possible to prevent circumferential thermal deformation and thermal stress that occur in the roof slab.

In addition, in the event of a heat removal system accident such as a blockage of the coolant outlet of the header or a damage to the heat pipe, it is important to note that the header has multiple outlet outlets and a large number of heat pipes. Due to the redundancy of equipment, the impact of accidents is extremely small and reliability is improved.

Furthermore, in terms of manufacturability, there are two partition plates inside a box-shaped structure.
1 and the partition plate 22, fixing the heat pipe thereto, and filling the middle chamber 24 with concrete, the manufacturing efficiency is very good.

〔Effect of the invention〕

As explained above, the present invention is directed to the axial direction 1 of the roof slab.
The temperature distribution can be made uniform in the circumferential direction, preventing the occurrence of thermal deformation and thermal stress, making it possible to create a safer roof slab. In addition, when assuming an accident in the heat removal system, the roof slab has a multiplicity structure and can be used as a roof slab with improved reliability. Furthermore, since it is easy to manufacture, it has the advantage of being able to provide an inexpensive roof slab.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing the overall structure of the fast reactor, FIG. 2 is a longitudinal cross-sectional view showing the structure of the roof slab of the present invention, and FIG. 3 is a diagram showing the axial temperature distribution of the roof slab of the present invention. be. 3... Roof slab 19... Heat insulation structure 20... Box-shaped structure 21.22... Partition plate 28... Heat pipe 26.27... Coolant header 25... Upper room 24...Middle room 23...Lower room Agent Patent attorney Nori Ken Yudo Chika Ken Daishimaru Figure 1 Figure 2

Claims (1)

[Claims] (1) In a roof slab consisting of a box-shaped structure that closes off the top surface of the reactor vessel that houses the reactor core and liquid coolant inside, and an insulating structure provided at the bottom of the box-shaped structure, the inside of this box-shaped structure is 1. A roof slab for a fast reactor, characterized in that the roof slab is partitioned into at least three layers in the direction, concrete is provided in the middle layer, and heat pipes are provided vertically penetrating the concrete layer.