JPH02247596A - Fast breeder - Google Patents

Abstract

PURPOSE:To reduce thermal stress by providing a roof deck which is joined with the opening part at the upper part of a safe container to seal the opening part and cools the safe container while the safe container is suspended by the opening part, and separating the opening part from the roof deck. CONSTITUTION:The safe container 2 is fixed and suspended while having its upper end stored in the roof deck 4 having a cooling function, its inside is sealed, and the upper end of the container 2 is separated from the roof deck 4. An auxiliary cylinder 5 is suspended from the roof deck along the side wall internal surface of a nuclear reactor container 1 and reaches the primary sodium liquid stored in the container 1. Consequently, only the hydrostatic pressure by a sodium cooling material is applied to the container 1 and high stress by a reactor core, etc., and a steep temperature gradient generated in the container 1 due to heating from below and cooling from above can be evaded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the structure of a fast breeder reactor, and particularly to a fast breeder reactor in which a core reactor vessel is supported by a safety vessel that protects the reactor vessel. Regarding furnaces.

[Conventional technology]

As a conventional fast breeder reactor reactor vessel support method, for example, the document "The Creys-Ma" published by NER8A
lville power plant (1985)
As introduced in ``Buddhism's Super Phoenix,'' a reactor vessel with a roughly U-shaped cross section is surrounded by a safety vessel with a roughly U-shaped cross section surrounding the sides and bottom, and the upper end is covered by a roof deck. The reactor vessel and safety vessel are each sealed tightly.The reactor core and other reactor internals are connected to the reactor vessel via the core support structure. The reactor vessel also contains primary sodium coolant.

This load is also supported in the reactor vessel.

In the case of a suspension support system in which the reactor vessel and safety vessel are suspended from the roof deck, the reactor vessel is used as a boundary for primary sodium and primary argon gas as a cover gas covering the primary sodium. In addition to the functional requirements of the reactor vessel, it is also required to function as a strength member that supports the necessary load.6 In terms of strength, a particular problem is that first, the reactor vessel is subject to long-term tensile stress under high temperature conditions. Second, the upper part of the reactor vessel is cooled by the roof deck cooling system, and the lower part is in contact with high-temperature sodium. This means that a large thermal stress occurs due to a large temperature gradient.In order to solve these problems, conventional methods have been to keep the reactor vessel at a low temperature by appropriately cooling it, etc., and to suppress the temperature gradient. Efforts are being made to reduce the thermal load on the reactor vessel and maintain its structural integrity.

In addition, as well-known examples regarding the yX reactor vessel support structure, there are Japanese Patent Application Laid-Open No. 57-204490 and Japanese Patent Application Laid-open No. 59-11.
There are those disclosed in Japanese Patent Application Laid-open No. 6094, Japanese Patent Application Laid-open No. 14198/1980, and the like.

[Problem to be solved by the invention]

As mentioned above, there are concerns regarding the structural integrity of the conventional nuclear reactor vessel, which is supported by hanging from a roof deck.

Firstly, the reactor vessel is subject to long-term tensile stress and pressure differential between the inside and outside due to the cover gas at high temperatures.Secondly, the reactor vessel has a steep temperature gradient, especially near the liquid level. Large thermal stress is generated.

There are problems such as these, and designs are being taken to solve these problems by taking appropriate measures such as cooling the reactor vessel and keeping it at a low temperature.

An object of the present invention is to eliminate the above-mentioned problems and provide a fast breeder reactor having a structure capable of reducing thermal stress and having a reactor vessel with higher structural reliability.

[Means to solve the problem]

The above purpose is to provide a reactor vessel that accommodates a reactor core, a sodium coolant that cools the reactor core, and a cover gas that covers the sodium coolant; a roof deck that connects and seals an opening at the top of the safety vessel, suspends the safety vessel from the opening, and has a cooling function to cool the safety vessel; This is achieved by means of a fast breeder reactor, characterized in that the opening is separate from the roof deck.

Preferably, the roof deck is provided with an auxiliary tube that is connected to and suspended from the roof deck and that reaches the sodium coolant.

It is also effective to provide a communication port that penetrates the side plate of the auxiliary cylinder in the thickness direction at a level above the liquid level of the sodium coolant in the auxiliary cylinder.

Further, it is preferable that an overflow suppression structure is provided between the reactor vessel and the auxiliary cylinder to prevent sodium coolant from overflowing,
The flood suppression structure should preferably consist of overlapping meshes.

[Effect]

In a fast breeder reactor in which the safety vessel supporting the reactor vessel is suspended from the roof deck and the upper opening of the reactor vessel is separated from the roof deck, the upper end of the side wall of the reactor vessel is a free end. It receives only the hydrostatic pressure of the sodium coolant inside the tank. Furthermore, since the spaces inside and outside the reactor vessel are communicated with each other, there is no difference in gas pressure between the inside and outside, and no stress is generated in the reactor vessel due to gas pressure.

Regarding safety containers suspended from roof decks,
The side walls bear the loads of the reactor vessel, core, sodium coolant, safety vessel itself, etc., and the roof deck bears all of these loads. The safety container is then cooled by the roof deck's cooling function.

If an auxiliary cylinder is provided that reaches the sodium coolant from the roof deck, the auxiliary cylinder will suppress sloshing of the sodium coolant, and if a communication hole is provided in the auxiliary cylinder, there will be no difference in gas pressure between the inside and outside of the reactor vessel. No stress is generated by cover gas.

If an overflow suppression structure is provided between the reactor vessel and the auxiliary cylinder, such as a structure in which meshes are overlapped, the overflow suppression structure will suppress the sodium coolant inside the reactor vessel from overflowing to the outside, and Flowing cover gas between the reactor vessel and the safety vessel.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 8.

FIG. 1 shows a first embodiment of a fast breeder reactor with a reactor vessel support system according to the present invention. Reactor vessel support structure 3 provided on the inner bottom of the surrounding safety vessel 2
Supported by The safety container 2 is suspended with its upper end covered by a roof deck 4 having a cooling function, and the inside thereof is sealed. On the other hand, the upper end of the reactor vessel 2 is separated from the roof deck 4.

and along the inner surface of the side wall of the reactor vessel 1.

The auxiliary cylinder 5 is suspended from the roof deck and reaches the level of the primary sodium liquid contained in the reactor vessel 1 as a sodium coolant.

According to the structure shown in FIG. 1, the core 6 in primary sodium
The loads of the reactor internals and other internal structures are transmitted to the reactor vessel 1 together with the primary sodium load.

It is further transmitted to the safety vessel 2 via the reactor vessel support structure 3. Therefore, this reactor vessel 1 does not have to support the above-mentioned load as the conventional reactor vessel does by the hanging portion of the roof deck at its upper end.

By supporting the reactor vessel 1 with the safety vessel 2 in this manner, tensile force due to the loads of the primary sodium, the reactor core 6, etc. does not act on the upper end of the reactor vessel 1.

In addition, a communication hole 5a is provided above the primary sodium liquid level in the auxiliary cylinder 5 to communicate the space between the reactor vessel 1 and the safety vessel 2. The pressure difference between the inside and outside of the reactor vessel disappears, and neither internal pressure due to gas pressure nor external pressure acts on the reactor vessel 1.

Due to the above-mentioned effects, only the hydrostatic pressure caused by primary sodium acts on the reactor vessel over a long period of time, which improves the reliability of the reactor vessel in terms of structural integrity.

Furthermore, the upper part of the nuclear reactor vessel 1 is separated from the roof deck 4, and in this case, unlike in the conventional suspension system, the upper part of the nuclear pressure vessel is not cooled, so that the upper part of the nuclear reactor vessel 1 is not cooled down rapidly near the sodium liquid level. No temperature gradients occur.

From the perspective of ensuring the structural integrity of the reactor vessel, this means that there is no need to properly cool the reactor vessel, and conventional reactor wall protection structures, such as those near the sodium liquid level in the reactor vessel, are no longer necessary. It may be possible to rationalize the cooling structure or heat shielding structure provided in the system by replacing it with a simpler structure.

On the other hand, if the upper end of the reactor vessel 1 is separated from the roof deck 4, the upper end is likely to lock during an earthquake. Therefore, this locking can be prevented by installing an auxiliary cylinder 5 suspended from the roof deck 4 close to the inside of the reactor vessel 1 and interfering directly or indirectly with the X reactor vessel 1. This auxiliary cylinder 5 also has the effect of suppressing sodium from overflowing outside the reactor vessel due to liquid level sloshing during an earthquake. In order to further suppress sodium overflow to the outside of the reactor vessel 1, an overflow suppression structure 7 filled with mesh or the like is installed in the gap between the reactor vessel 1 and the auxiliary cylinder 5.

The reactor vessel support structure 3 will be explained with reference to FIGS. 2 to 4. Figure 2 is a view from the ■-■ arrow in Figure 1, and shows the reactor vessel 1.
An appropriate number, for example, eight vertical ribs 8 are provided on the outside of the bottom of the safety container 2 radially from the center, and correspondingly, concave vertical ribs 9 are provided on the inside of the bottom of the safety container 2 in the radial direction. .

Figure 3 (■-■ cross section of Figure 1) and Figure 4 (I of Figure 3)
As shown in V-IV sectional view), the vertical rib 8 of the reactor vessel
The vertical ribs 9 of the safety vessel have a structure of one plate at each location, and the vertical ribs 9 of the safety vessel have a structure of 2' plates sandwiching the vertical ribs 9 to prevent swinging of the reactor vessel 1 and the safety vessel 2 in the circumferential direction. On the other hand, in the radial direction, a displacement difference occurs due to a difference in thermal expansion due to a temperature difference between the reactor vessel 1 and the safety vessel 2, so it is necessary to have a structure to release or absorb this displacement. Therefore, in this embodiment, the vertical ribs 8, which are free in the radial direction,
9 is used to create a structure that allows this relative displacement to escape. Therefore, by sliding the top of the vertical rib 8 on the 1M sub-reactor vessel 1 side on the surface of the sliding member 10 provided at the bottom of the vertical rib 9 on the safety vessel 2 side, relative displacement can be smoothly released. Furthermore, by arranging an appropriate number of these vertical ribs 8 and 9 in the circumferential direction, misalignment of the axis between the reactor volume 1I11 and the safety vessel 2 can be prevented.

In FIG. 5, as a modification of FIG. 1, the reactor core 6 is replaced with the reactor vessel 1.
The second embodiment of the present invention is the same as that shown in FIG. 1 except for the support method of the reactor core 6 and the reactor vessel support structure 3, which is used when supporting the reactor from the side.

6 and 7 show structural examples of the reactor vessel support structure 3 in the second embodiment shown in FIG. 5. The structure 1 function is similar to that shown in FIGS. 3 and 4, except that the vertical ribs 8 of the reactor vessel 1 and the vertical ribs 9 of the safety vessel are installed on the sides of both vessels.

FIG. 8 shows a sodium overflow suppressing structure 7 showing an example of the structure of the sodium overflow suppressing structure 7 shown in FIGS. 1 and 5.
is provided over the entire circumference of the gap between the reactor vessel 1 and the auxiliary cylinder 5 and at a level above the sodium liquid level. A mesh 13 is provided between the mounting seat 11 provided on the inner peripheral surface of the reactor vessel 1 and the mounting seat 12 provided on the outer peripheral surface of the auxiliary cylinder 5.
etc., and secure with bolts, etc.

Both mounting seats 11, 12 are constructed of perforated plates so that cover gas can pass therethrough. Furthermore, the axial length of the mesh 13 is slightly longer than the gear spacing between the two mounting seats 11 and 12, and by compressing and tightening it during installation, unnecessary gaps that could become a path for sodium overflow can be avoided. Try to eliminate it.

〔Effect of the invention〕

According to the present invention, a fast breeder reactor has a structure in which a reactor vessel containing a reactor core, sodium coolant, etc. is supported by a safety vessel, and the safety vessel is suspended from a roof deck for cooling.
In addition, because the reactor vessel is separated from the roof deck, only the hydrostatic pressure from the sodium coolant is applied to the IM child reactor vessel, which is similar to that seen in conventional fast breeder reactors in which the reactor vessel is suspended from the roof deck. It is possible to avoid the high stress generated in the reactor vessel due to the load of the reactor core, sodium coolant, etc., as well as the rapid temperature gradient that occurs in the reactor vessel due to heating from below and cooling from above. Since the structure allows communication between the spaces in the vessel and the safety vessel, it is possible to eliminate the effect of cover gas pressure on the nuclear vessel, which improves reliability in terms of the structural integrity of the fast breeder reactor. can.

Furthermore, by providing an auxiliary cylinder that reaches the sodium coolant from the roof deck and providing a water overflow suppression structure between the auxiliary cylinder and the reactor vessel, it is possible to prevent the sodium coolant from spilling out from the reactor vessel.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a fast breeder reactor according to a first embodiment of the present invention, FIG. 2 is a view taken along arrow nn in FIG. is a sectional view of the reactor vessel support structure of the first embodiment, FIG. 5 is a diagram showing the fast breeder reactor of the second embodiment according to the present invention, and FIGS. 6 and 7 are the reactor vessel of the second embodiment. A cross-sectional view of the support structure, FIG. 8, is a view showing the sodium flooding structure of FIGS. 1 and 5. DESCRIPTION OF SYMBOLS 1... Reactor vessel, 2... Safety vessel, 3... Reactor vessel support structure, 4... Roof deck, 5... Auxiliary cylinder, 5a... Communication port, 6... Reactor core , 7... Sodium overflow suppression structure, 8... Vertical ribs, 9... Vertical ribs,
DESCRIPTION OF SYMBOLS 10...Sliding member, 11...Mounting seat, 12...Mounting seat, 13...Mesh. Figure 1: Atomic P2 t1 2: Safety organ 3: #Chisudoor guest equipment support nm-, tip 4° roof top 17 grains door pull 5: Pre-power B force letter 7: Overflow net p red L 晦゛j1 5a: JJL hole diagram Figure 2 (π-■ arrow prediction) Figure (V-VUfr plane) Figure (■-■l!a plane]

Claims (1)

[Claims] 1. A reactor vessel that accommodates a reactor core, a sodium coolant that cools the core, and a cover gas that covers the sodium coolant; comprising: a safety vessel that supports a reactor vessel; and a roof deck that connects and seals an opening at the top of the safety vessel, suspends the safety vessel from the opening, and has a cooling function that cools the safety vessel; A fast breeder reactor, wherein the opening at the upper end of the reactor vessel is separated from the roof deck. 2. The fast breeder reactor according to claim 1, further comprising an auxiliary tube that is connected to and suspended from the roof deck and reaches the sodium coolant. 3. The fast breeder reactor according to claim 2, wherein a communication hole is provided in a side plate of the auxiliary cylinder at a portion above the liquid level of the sodium coolant, the communicating hole passing through the side plate in the thickness direction. 4. The fast breeder reactor according to claim 2 or 3, further comprising an overflow suppression structure for preventing sodium coolant from overflowing between the reactor vessel and the auxiliary cylinder. 5. The fast breeder reactor according to claim 4, wherein the overflow suppression structure is formed by overlapping meshes.