JPS59116580A - Reactor container - 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 [Field of Application of the Invention] The present invention relates to a nuclear reactor vessel having a gas insulating layer, and particularly to a nuclear reactor vessel that provides suitable thermal insulation performance over a long period of time.

[Prior art]

In large nuclear power reactors, for example fast reactors that use liquid sodium as a coolant, the diameter of the reactor vessel is I.
Qm or more, especially for tank type fast reactors, it can be more than 20m. In the above-mentioned fast reactor, sodium, which is a coolant, is operated at a temperature of 500C or higher, so direct contact between such high-temperature sodium and the reactor vessel poses problems in terms of the strength of the reactor vessel, and the wall temperature of the reactor vessel increases. In order to lower the temperature to around 400C, a heat insulating layer will be provided on the inner surface of the reactor vessel. A gas insulation layer is used as one of these insulation structures.

FIG. 1 shows a conventional example using a gas heat insulating layer.

The nuclear reactor is hermetically sealed with a shielding lid 1 placed on top of a reactor vessel 2. The core 5' is supported by a core support structure 4', and the low temperature coolant in the lower plenum 7 is heated by the core 5' trap and flows to the upper plenum 6', where it is then cooled by an intermediate heat exchanger. and returns to the lower plenum 7. The reactor vessel 2 is thermally shielded by a gas layer 8' provided between the reactor vessel 2 and the partition wall 3. However, since the heat insulating layer 8' communicates with the cover gas plenum 9' above the upper plenum 6', in the prior art, the coolant evaporated from the liquid level of the upper plenum 6' has a lower temperature. Since it condenses and liquefies on the inner surface of the reactor vessel 2 and accumulates in the heat insulating layer 8', the heat insulating performance deteriorates due to the paper transfer of the liquefied coolant, so the temperature 4 of the reactor vessel is increased.
There are drawbacks that reduce its strength.

[Purpose of the invention]

The present invention provides a cooling material (
By reevaporating the liquid), the above disadvantages can be eliminated.
The present invention provides a nuclear reactor vessel with good heat insulation performance.

[Embodiments of the invention]

The present invention will be explained by examples. FIG. 2 shows an embodiment of the present invention, in which a fine mesh 10 is provided on the outer surface of the partition wall 3.
' is provided. A portion of the coolant evaporated from the upper plenum 6' to the cover gas plenum 9' condenses and liquefies on the lower temperature inner surface of the reactor vessel 2 and falls to the bottom of the gas insulation layer 8', but this liquid is 10', it is transported by capillary action to the higher temperature wall surface of the partition wall 3, where it evaporates again. As described above, according to the present invention, it is possible to prevent the overnight coolant from accumulating in the gas heat insulating layer 8' and deteriorating the heat insulating performance.

It is clear that, in addition to providing a mesh as a mechanism for transporting liquid to the wall surface of the partition wall 3, the same effect can be obtained by directly processing fine lines on the partition wall surface.

FIG. 3 shows a reactor vessel 2 and a partition wall 3 in another embodiment of the present invention.
A partition wall 11' is provided in the middle of the partition wall 3, and a mesh 10' is provided on the surface facing the partition wall 3. In addition to increasing the evaporation area, this embodiment also prevents heat transfer caused by direct condensation of the steam evaporated from the partition wall 3 on the wall surface of the reactor vessel 2, which further improves the insulation performance. can be done.

According to the present invention, condensed liquid is not accumulated in the gas insulation layer, and there is a significant effect in preventing deterioration of the insulation performance of the reactor vessel.

Further, FIG. 4 shows another embodiment of the present invention. In FIG. 4, a liquid heat shielding layer 42 is provided on the outer periphery of the high temperature plenum 8, a liquid heat shielding layer 41 is provided on the outer periphery of the high temperature plenum 8, and a sealed liquid (for example, NaK) is placed in the heat shielding layer 41. Heat transport pipe using vaporization and condensation (hereinafter referred to as heat pipe)
11 is inserted, and the other end is inserted into the cooling pipe 10 that circulates a low-temperature coolant, thereby cooling the heat shielding layer 41.

The heat pipes 11 are arranged along the wall of the reactor vessel at appropriate intervals in the circumferential direction, and the number of heat pipes is determined by the required amount of heat removal. The features of the cooling method using heat pipes will be explained using FIG. 5. The inside of the heat pipe 11 is maintained at a high vacuum and is filled with a small amount of liquid. The vapor vaporized in the high temperature section 12 moves almost at the speed of sound to the low temperature section, where it condenses and releases the heat of vaporization, and the liquefied liquid returns to the high temperature section 12 by capillary action in the mesh 14. A feature of heat pipes is that the heat flux is not proportional to the temperature difference between the high-temperature part and the low-temperature part, as is the case with ordinary heat conductors, but is proportional to the vapor pressure determined by the temperature of the high-temperature part. FIG. 6 shows a vapor pressure curve when NaK is used.

As can be seen from FIG. 6, the characteristics of the heat pipe using NaK exhibit the characteristics of a type of thermal switching element, in which the amount of heat removed is extremely small below about 40 CI' and rapidly increases above about 400 C. This provides the following favorable characteristics as a cooling method for the reactor vessel wall.

(1) Even if the temperature of the high-temperature plenum 8 rises, the temperature of the container wall 2 is maintained at about 4000°C.

(2) Even if the temperature of the high-temperature plenum 8 suddenly decreases as in a reactor scram, the amount of heat removed by the heat pipe also decreases rapidly, and the temperature of the vessel wall 2 does not suddenly change from about 400C.

The above characteristics indicate that the reactor vessel 2 is not subjected to a large thermal shock.

Furthermore, the amount of heat transport in the heat pipe increases or decreases depending on the temperature of the high temperature section (
(Refer to FIG. 6) (3) There is no temperature difference in the axial direction of the reactor vessel wall 2.

(4) There is no temperature difference in the circumferential direction of the reactor vessel.

It is shown that This has the great advantage of avoiding thermal deformation due to local temperature distribution, which is a problem especially in the case of large containers.

As described above, the present invention provides an extremely suitable method for cooling the reactor vessel wall. In the embodiment shown in FIG. 4, the cooling pipe 10 is provided at the top, but the heat pipe 1
It is clear that the same effect can be obtained even if it is provided at the lower part of 1. Moreover, if the cooling capacity of the cooling pipe 10 is sufficient,
The heat shield layer 42 can also be omitted. Fig. 8 shows an example of a specific structure according to this embodiment. Cooling pipes 10 are arranged in a header shape along the circumferential direction of the furnace vessel 2, and argon gas for cooling is supplied. .

The argon gas is discharged from the upper end of the heat pipe 11 into the cooling furnace container, and is separately returned to the purification system where it is cooled again and circulated.
do.

Another embodiment of the invention is shown in FIG. In FIG. 7, one end of the heat pipe 11 is inserted into the low temperature plenum 7 (in this case, inside the low temperature plenum 7,
By taking care to improve the fluidity of the coolant around the heat pipe 11 so that it does not become a stagnant, there is an advantage that the cooling pipe 1o can be omitted. An example of this specific structure is shown in FIG. This utilizes core support structure attachment bolts 14.

As described above, the present invention provides a safe and good reactor vessel wall cooling method that prevents the occurrence of thermal shock and local thermal stress by utilizing the heat transport characteristics of heat pipes.

In addition, the heat pipe 11 has a diameter of 2 when flying NaK.
Performance will be satisfactory if approximately 150 to 2004C are used. Using such a large number of identical products not only reduces manufacturing costs but also has the advantage of improving reliability because even if some parts are damaged, there is no functional problem. Moreover, the plug-in type shown in FIG. 9 is easy to replace.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view showing the structure of a conventional reactor vessel, FIG. 2 is a partial cross-sectional view of a reactor vessel according to an embodiment of the present invention, and FIG. FIG. 4 is a partial sectional view of a reactor vessel according to another embodiment of the present invention, FIG. 5 is a sectional view of a cooling section using a heat pipe, FIG. 6 is an evaporation curve of NaK, and FIG. Figure 8 is a partial sectional view of a reactor vessel according to another embodiment of the present invention.
FIG. 9 is a concrete structural diagram of another embodiment. 2... Reactor vessel wall, 41.42.9... Shielding layer,
7... Low temperature plenum, 8... High temperature plenum, 10.
...Cooling Y 1 Figure! New 2nd figure Kaya 3rd figure 3 Merei Ahika゛X Yq figure

Claims (1)

[Claims] 1. A nuclear reactor characterized in that, in a reactor vessel structure in which a gas insulation layer is provided between a high temperature, a liquid, and an inner wall of the reactor vessel, liquid condensed on the wall surface forming the gas insulation layer is reevaporated. container.