JPS59160798A - Cooling device for shielding plug of fast reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a cooling device for a fast reactor shielding plug.

[Technical background of the invention and its problems]

In general, a fast reactor shielding plug that shields the upper opening of the reactor vessel of a fast breeder reactor has a sealing material provided on the top surface of the plug, measurement terminals, and various equipment such as electrical instrumentation parts that are exposed to high temperature inside the reactor. A cooling device is provided to lower the temperature near the top surface to approximately room temperature in order to protect the area from heat damage.

As shown in FIG. 1, this type of conventional cooling device consists of an annular fixed plug fixed in the upper opening of the furnace vessel and a rotary ball bearing 3 mounted on the fixed plug a. A fast reactor shielding plug consisting of a rotating plug q mounted on a fast reactor shielding plug is simply provided with a hollow cooling layer 7 at the top of each plug to which refrigerant is supplied and discharged from the outside through a reflux vibro feed pipe S1. Therefore, almost sufficient cooling can be achieved during operation of the fast breeder reactor, but
There was an inconvenience in that sufficient cooling could not be achieved during fuel exchange.

That is, in operating conditions where liquid sodium is flowing into the reactor vessel/into the reactor vessel through the inlet pipe g, through the reactor core section 9 and then out through the outlet pipe 10, the free surface of liquid sodium at approximately SOO°C. The heat dissipated from l/3 is propagated through the inert gas saw layer to the support structure/3 of each plug, da. This support structure /3 has a radiation shielding layer /da for preventing radiation leakage inside, and a large number of heat shielding layers /da for heat insulation.
S is provided, as well as a core upper mechanism/6 that controls the reactor core, a fuel exchanger/7, and a fuel loading/unloading machine 1.
In order to support a heavy structure such as 1.g, it is made of a thick metal plate due to strength requirements. Therefore, a large amount of heat propagated to the supporting structure/3 is propagated to the upper part of each plug 3 through the receiving structure/3. However, since this amount of heat is exchanged with the refrigerant sent inside the cooling layer, it is not transferred to the upper surface /q of each plug, but instead is transferred to the upper surface /q of each plug. is maintained at approximately room temperature.

On the other hand, when replacing fuel, between each plug and da.

The rotary plug q placed on the rotary ball bearing 3 is rotated by driving the rotary gear 2/ by a drive motor (not shown). As the rotary plug holder rotates, the feed pipe that supplies and discharges the refrigerant to and from the cooling layer 7 and the circulation vibro also rotate, so each pipe 3 and B are closed using a gate valve (not shown) to cool the cooling layer 7. The layer 7 is sealed and cooling pipes (not shown) are removed from each pipe. In this way, in the closed cooling layer 7, cooling is performed only by natural convection caused by a temperature difference between the lower surface and the upper surface within the cooling layer 7, and its cooling capacity is very small.

Normally, during fuel exchange, the sodium temperature is lowered to about 200°C, but as mentioned above, the cooling capacity of the cooling layer 7 is small, so the range of sodium temperatures that can maintain the top surface of each plug λ and da at room temperature is limited. It had the disadvantages of being narrow and having a low maximum temperature. Furthermore, due to some unknown reason, the temperature of the upper surface of each plug could not be lowered to near room temperature due to the high sodium temperature, and there was a risk that equipment installed on the upper surface would suffer heat loss.

[Purpose of the invention]

The present invention has been made in view of these points, and a convection cooling layer that communicates with the cooling layer is provided on the top surface of the plug to provide a large cooling capacity during fuel exchange. Moreover, it is an object of the present invention to provide a cooling device for a fast reactor shielding plug that can increase its maximum temperature.

[Summary of the invention]

The cooling device for a fast reactor shielding plug of the present invention includes a cooling layer provided at the top of the fast reactor shielding plug so that a coolant can be freely supplied;
The fast reactor shielding plug projects upward from the top, has an upper end closed, and a lower end formed by an annular convection cooling layer communicating with the cooling layer.

[Embodiments of the invention]

The present invention will be described below with reference to embodiments shown in FIGS. 2 and 3.

FIG. 2 shows an embodiment of the present invention, in which the same parts as in the prior art are given the same reference numerals.

First, the present invention provided on the fixed plug λ will be explained in detail.

In this embodiment, a convection cooling layer 24 is provided between the inner and outer annular heat dissipating plates 2J a and Q3 b from the upper surface /q of the upper plate 22.
The upper end openings of both heating plates 23a, :l, jb are closed with a cover JC, and the upper plate 22 is provided with the above-mentioned gap. It is formed by drilling a communication hole J that communicates with the cooling layer 7.

Next, a detailed explanation of the present invention provided in the rotating plugder will be given.

In this embodiment, the upper ends of the inner and outer heat sinks na and 23b are bent outward to form an inverted-shaped gap, and the outer ends are closed to form a gear unit l for rotating the rotary plug. It is a thing,
The rest of the structure is similar to the device provided on the fixed plug λ.

Next, the cooling effect according to this embodiment will be explained.

During operation of the fast breeder reactor, cooling is performed by forcibly supplying and discharging refrigerant into the small cooling layer 7 provided at each plug through the feeding vibrator 3 and the reflux vibro, and cooling the upper surface/
9 is sufficiently maintained at room temperature.

On the other hand, when the supply of refrigerant is stopped during fuel exchange, the refrigerant undergoes natural convection (thermosyphon phenomenon) through the cooling layer 7 and the convection cooling layer portion, and sufficient cooling is performed. To explain further, since the convection cooling layer protrudes upward, the refrigerant inside is in a state where sufficient convection can occur, and the refrigerant located above the convection cooling layer is connected to the outside through the heat sink, 2.7 m, UB. Since it is cooled by heat exchange, it flows down in the convection cooling layer J, and at the same time, the high temperature refrigerant at the lower position actually rises and convection occurs, and the amount of heat propagated from the support structure /3 is transferred to the heat sink 23a, It is dissipated through λ3b, and the upper surface /9 is cooled to approximately room temperature. In order to efficiently perform this cooling, it is preferable that the gap between the heating plates 23 a , , ZJ b be 30 to /σ0TrR. Moreover, since the cooling capacity is thus high, even if the sodium temperature in the furnace rises, the top surface temperature can be kept close to room temperature.

In addition, if for some reason the radiation dose on the top surface/9 partially exceeds the allowable value, if an additional shield (not shown) is layered on top of the radiation shielding layer/9, the cooling layer 7 will provide sufficient cooling. However, since the natural convection of the refrigerant in the convection cooling layer J can exert its cooling ability, the vicinity of the upper surface /9 can be cooled to approximately room temperature.

FIG. 3 shows yet another embodiment of the present invention, including inner and outer heat sinks! , 7 m, , 2 Jb from the upper end opening of the dummy book, 2
6 is inserted into a convection cooling layer 24, and the convection cooling layer J is closed to the cooling layer. The mutual connection is carried out by bolting the seven lunges 7 together.

This blockage of the convection cooling layer occurs when the fast breeder reactor is operating, and during operation, the refrigerant flows into the convection cooling layer, reducing the efficiency of forced cooling in the cooling layer. This is to prevent this from happening.

〔Effect of the invention〕

As described above, the fast reactor shielding plug cooling device of the present invention is constructed by providing a cooling layer provided at the top of the plug with an annular convection cooling layer protruding upward from the top. Cooling can be performed by natural convection, and the cooling capacity is particularly large during fuel exchange in fast breeder reactors, making it possible to widen the fluctuation range of sodium temperature during fuel exchange and increase the maximum temperature. Furthermore, even in the event of a sudden rise in sodium temperature or increase in radiation dose, the top surface of the plug can be maintained at room temperature, preventing heat loss from equipment installed on the top surface of the plug, and making it easier to maintain equipment on the top surface. This makes it possible to achieve advantages such as excellent reliability.

It should be noted that the device of the present invention may also include other cooling devices attached to the convection cooling layer portion. For example, a liquid cooling pipe can be attached to the heat sink, or the heat sink can be cooled by air.

Furthermore, although the above-mentioned embodiments show examples in which the present invention is applied to a fixed plug and a rotating plug, the present invention can also be applied to various other types of shielding plugs. −

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view showing a shielding plug and a reactor vessel with a conventional device attached thereto; FIG. The figure is a longitudinal sectional side view showing another embodiment of the present invention showing a convection cooling layer with a dummy plug inserted. C...Fixed plug, D...Rotating plug, R...Cooling layer, /9...Top surface, n...Top plate 1.2Ja,,2
．． ．． 7b...Annular heat sink, J...Convection cooling layer,...Communication hole 1.26...Dummy plug. Applicant's agent Kiyoshi Inomata

Claims (1)

[Claims] l A cooling layer provided at the top of the fast reactor shielding plug so that refrigerant can be freely supplied; and a cooling layer protruding upward from the top of the fast reactor shielding plug, the upper end of which is closed, and the lower end of the fast reactor shielding plug. A cooling device for a fast reactor shielding plug, the part having an annular convection cooling layer communicating with the cooling layer. The convection cooling layer consists of fixing inner and outer annular heat sinks to the top plate of the fast reactor shielding plug with a gap between them, closing the upper end openings of the inner and outer heat sinks, and The cooling device for a fast reactor shielding plug according to claim 1, characterized in that it is formed with a communication hole that communicates the gap and the cooling layer. 3. The cooling device for a fast reactor shielding plug according to claim 1, wherein the convection cooling layer is formed to be openable and closable with respect to the cooling layer. Claim 2, characterized in that an annular dummy plug having a shape that can be inserted from the upper end opening into the gap between the inner and outer heat sinks is detachably attached to the upper end of the heat sink. Cooling device for the fast reactor shielding plug described.