JPS6076688A - Nuclear reactor structure - 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 structure, and particularly to the realization of an earthquake-resistant structure for completely improving the integrity of the reactor.

[Background of the invention]

The total weight of a conventional nuclear reactor, all examples of tank type Ff3R, and [2] will be explained using FIG.

4 tank-type reactor vessels, reactor core 6, and heat generated by the nuclear fission reaction inside the reactor core? It is a dog-bore valley device that houses the liquid metal coolant 10 to be taken out, the main circulation pump 9 to circulate it, the intermediate heat exchanger 8 to transfer heat to the total secondary system, etc., and is installed at the top. roof slab
It is supported hanging down from 3. Further, the roof slab 3 is supported by the pedestal 1 through a support structure (skirt) 2V. The support structure supports the entire weight of the reactor, weighing approximately 10,000 tons, making it an important issue to ensure the reactor's integrity in the event of an earthquake. be.

However, (1) In the event of an earthquake, seismic force entering from the pedestal l is transmitted to the reactor vessel 4 via the skirt 2 and roof slab 3.

The reactor vessel 4, upper core mechanism 7, intermediate heat exchanger 8, main circulation pump 9, and other heavy equipment are directly supported by the roof slab 3. In conventional nuclear reactor W structures, the natural frequency is small, and there is a structural limit to achieving a sufficiently high value for earthquake response input, and the natural frequency is close to the predominant value of the earthquake response acceleration of the reactor building. Therefore, the response acceleration must be considerably large? I don't get it. Therefore, in order to withstand seismic force, it is necessary to have a three-member rigid roof slab structure that can support the full weight of the reactor vessel (C), which increases the weight of the reactor vessel 4 and the accompanying increase in the weight of the reactor vessel 4. Various disadvantages occur, such as a significant increase in the construction period due to the increase in the number of welding meters, and a decrease in the reliability of welding thick stainless steel.

Furthermore, in a reactor structure that has a large response during an earthquake, the emergency insertion performance of control rods in the event of an earthquake may deteriorate, and this is not a good idea from the standpoint of reactor reliability.

[Purpose of the invention]

The purpose of the present invention is to reduce the stress noise generated by the members of the roof slab during excavation by reducing the moment of inertia of the roof slab and increasing the natural frequency of the roof slab itself. The objective is to provide an entire nuclear reactor structure that can improve the structural integrity of the nuclear reactor on the ground, and improve the emergency control rod insertion performance.

[Summary of the invention]

The main points of the present invention are shown in Fig. 2-2 in comparison with Fig. 2-1 of a vibration model of an example of the present invention.

Figure 2-1 is a vibration model diagram of a conventional example. In the conventional nuclear reactor structure, the intermediate heat exchanger, the main circulation pump, and the roof slab are directly supported, and the natural frequency of the roof slab does not include the weight of the one mechanism above the core, which accounts for approximately 35% of the total city total. Rigidity and moment of inertia related to the weight WR8 of the roof slab itself, and stiffness and moment of inertia related to the weight Wa + Wc of the hanging reactor vessel, etc., which accounts for about 40% of the total weight, totaling about 25 inches of the total weight? It is determined by the rigidity and moment of inertia regarding the weight of the intermediate heat exchanger, main circulation cylinder 1, etc., which are directly supported and suspended from the roof slab occupying the space.

Among these, the moment of inertia related to the reactor vessel WR+Wc, which accounts for about 40% of the total weight of the reactor structure, has a short distance from the support point with the skirt, which is the fulcrum of the vibration mode of the roof slab, and a small radius of rotation.

Equation (1) shows the relationship between radius of rotation, weight, and moment of inertia, and Equation (2) shows the relationship between moment of inertia, rigidity, and natural frequency.

(Moment of inertia) = (stop 1i°) / (rotation radius) 2 (
1) As can be seen from both equations, the radius of rotation has a linear effect on the natural frequency. In other words, the reactor vessel's small radius of rotation cannot be the main factor determining the natural frequency of the roof slab. That is, in the conventional nuclear reactor structure, the moment of inertia related to the roof slab itself, and the moment of inertia related to the intermediate heat exchanger, main circulation pump, etc. (C) that are directly supported and suspended from the roof slab are This is the main factor that determines the natural frequency of the roof slab in the example reactor structure.For this reason, in the conventional reactor structure, the moment of inertia of the intermediate heat exchanger, main circulation pump, etc. Therefore, even if the roof slab is completely rigid in order to increase the natural frequency of the roof slab, it is difficult to lower the natural frequency due to the accompanying increase in the roof slab's own weight.As a countermeasure, it is difficult to lower the natural frequency. It was necessary to plan the design and construction to meet advanced design requirements to ensure soundness and welding construction requirements.

The entire vibration model diagram of the present invention is shown in Figure 2-2. The difference between the present invention and the conventional example is the weight W of the intermediate heat exchanger and the main circulation pump. k) It is not supported by a roof slab, but is supported by a core support structure. According to the present invention, the weight W of the intermediate heat exchanger and main circulation pump, which was one of the factors determining the natural vibration deposit of the roof slab in the conventional example,
Since o was not directly attached to the roof slab but supported by the core support structure, it is included in the weight of the reactor vessel WR + Wo + Wc. Therefore, the weight of the reactor vessel WR+Wo
+Wc increases to about 65 times the total weight, but as mentioned above L7, its radius of rotation is small, so it is excluded from the factors that determine the natural frequency of the roof slab. That is, according to the present invention, the natural frequency of the roof slab is dramatically increased to -1 compared to the conventional example, which not only improves the structural integrity of the reactor during an earthquake, but also improves the structural integrity of the roof slab during an earthquake. The displacement is reduced, the relative displacement between the upper core mechanism supported by the roof slab and the reactor core is reduced, and control rod emergency insertion can be improved.

The 31st page shows a comparison between the conventional example and the present invention regarding the natural frequency of the roof slab. In a nuclear reactor whose roof slab structure is basically the same shape, the reactor structure according to the present invention can be expected to increase the natural frequency by about 20 to 30% compared to the conventional reactor structure.

Moreover, according to the nuclear reactor structure according to the present invention, if the conventional structure q
) If the natural vibration can be used, the rigidity can be lowered by about 20 to 30% than the conventional one, and it is therefore possible to reduce the weight of the entire reactor structure. Further, the structure according to the present invention has a property that the natural frequency increases as the square of the stiffness as long as the range between the stiffness and the natural frequency is such that the parabolic weight increase is not significant.

FIG. 4 shows the relationship between the roof slab natural frequency and the earthquake response input, with the horizontal axis showing the reciprocal of the natural frequency and the vertical axis showing the earthquake response input. While the natural frequency of the conventional example shown as a shows an excellent seismic response input, [7, the natural frequency of the present invention shown as b shows a noticeable decrease in seismic response input,
The seismic response input has decreased by about 20 to 30% compared to the conventional example, and the reactor structure is questionable. It is clear that the structure enhances

[Embodiments of the invention]

An embodiment of the tank-type nuclear reactor structure of the present invention will be described below with reference to Figure 5.

The nuclear reactor according to the present invention includes a reactor core 6, a coolant 10 that is generated in the core and takes out heat, and an intermediate heat exchanger 8 that transfers the heat of the coolant to the outside. A nuclear reactor vessel 4 is installed on the top of the reactor vessel and is supported by being joined to a roof slab 3. The intermediate heat exchanger 8 and the main circulation pump 9 are constructed using a core support mower 5? ζIii! It is supported only in the horizontal direction by a support 44' having a radiation seal structure 11i with the roof slab 3 at its upper end. It is installed on the roof slab 3 through one skirt 2 to the reactor and on the pedestal 1. In addition, there are 13 inert gas spaces inside the reactor vessel (the upper part of which has a free liquid level 12).

The weight added to the roof slab 3 is the 111 weight of the reactor vessel 4, which includes the intermediate heat exchanger 8, 9 dry bongs, etc., and the weight of the roof slab 3 itself, which includes the reactor upper structure, etc.: However, considering the vibrations above and below the roof slabs 3 and J, which play an important role in the vertical vibrations of the reactor structure,
Regarding the reactor vessel, whose weight accounts for approximately 65% of the total weight of the reactor structure, the distance from the support point to the skirt 2, which serves as the fulcrum for vertical vibration of the roof slab, is short, and the radius of rotation is small.

In other words, the effect on the vertical natural frequency of the inertial roof damper 3, which is proportional to the product of the rotation half-load and the weight, is small. ,
l: The vertical natural frequency of the roof slab 3 is mostly controlled by the moment of inertia of the roof slab 3 itself, which is determined by the weight of the roof slab 3 itself including the core upper mechanism 7 and its radius of rotation. In other words, compared to the conventional VC structure in which the intermediate heat exchanger 8 and the main circulation pump 9 are supported by the roof slab 3, it is reduced by the moment of inertia caused by the load of the intermediate heat exchanger 8 and the main circulation pump 9 at 11°C. 1
The well-reduced upper and lower natural frequencies of the roof slab 3 make it possible to maintain a high frequency that reduces earthquake response input.

Furthermore, according to the present invention, the core support structure 8, which conventionally had through holes for the intermediate heat exchanger 8 and the main circulation pump 9,
Intermediate fever 5! : By fixedly supporting the converter 8 and the main circulation pump 9, their rigidity increases, and the relative displacement between the core support structure 8 and the core upper mechanism 7 suspended and supported by the roof slab 3 is also reduced. Is there any improvement in performance in terms of ease of insertion of control rods? tA - In addition, the core support structure 5 has an intermediate heat exchanger 8 and a main circulation bonder 9.
By being fixedly supported, the conventional reactor cooled liquid metal pot brenum 10-1 and cold brenum 10
- The complex seal structures such as bellows seals and manometer seals that were separated into 2 parts are completely removed, which is expected to be effective in terms of manufacturing efficiency and cost, and also lead to a single line in the construction period.

Further, an intermediate heat exchanger 8 fixedly supported on the core support structure
, by providing horizontal support with sealing performance by the entire roof slab 3 at the upper end of the main circulation pump 9,
The conventional cantilever beam has been changed to a beam model with one end fixed and one end supported, and the soundness of the intermediate heat exchanger 8 and the main circulation pump 9 itself in the event of an earthquake is also improved. This is particularly effective in preventing serious problems such as galling of the main circulation pump's 9 shafts.

Nowadays, we have focused on the vertical vibration υ1 frequency, but the horizontal fixed frequency is lower than before because the load support points of the intermediate heat exchanger 8, main circulation pump 9, etc. are lower than before. The moment of inertia for the conventional model increases. However, horizontal vibrations were conventionally supported only by the rigidity of the reactor vessel, but horizontal vibrations were supported by the intermediate heat exchanger 8 and the main circulation pump 9, which were supported by the core support structure 5 and the roof slab 3. Since it is supported at two points, the rigidity against horizontal motion increases by the rigidity of the beams of the intermediate heat exchanger 8 and the main circulation pump 9, which offsets the increase in the horizontal moment of inertia, and the horizontal natural pendulum 〇 The decline in numbers is not a problem.

〔Effect of the invention〕

As explained below, the nuclear reactor according to the present invention reduces the moment of inertia of the roof slab by fixedly supporting the intermediate heat exchanger, main circulation bong, etc. from the suspension support of the roof slab to the core support structure. , its rigidity can be increased, the response acceleration to seismic input can be completely reduced, and the reactor health can be improved, as well as the reactor core held in the reactor vessel and the reactor core holding the control rods. It is possible to suppress the relative displacement with the upper mechanism, improve emergency control rod insertion performance in the event of an earthquake, and expect a significant improvement in reactor safety.

[Brief explanation of the drawing]

Figure 1 is a structural diagram of a conventional nuclear reactor, and Figure 2-1. Figure 2-2 is a comparison diagram of the vibration model of the conventional example and the present invention, Figure 3 is a comparison diagram of the relationship between the rigidity of the roof slab and the natural frequency of the conventional example and the present invention, and Figure 4 is the natural frequency. Regarding the seismic response input, FIG. 5 is a comparison diagram between the conventional example and the present invention, and FIG. 5 is a structural diagram of an embodiment of the present invention. 4... Reactor vessel, 5... Core support structure, 6...
Reactor core, $ 1 Figure ¥2-1 (2) Figure 2-2 (2) Figure 3 IL-Fasula FAIi Small No. 4 (21 1/U @ Condolence Service)

Claims (1)

[Claims] 1. i. A sub-reactor vessel, a roof slab that supports this reactor vessel with the entire hanging L2, a skirt that supports this roof slab, a reactor building pedestal that fully supports this skirt, and a reactor core within the reactor vessel. Thermal energy generated in? In a nuclear reactor structure consisting of an intermediate heat exchanger to take out, a main circulation pump that circulates the entire liquid metal coolant in the reactor vessel, and a core support structure that supports the whole reactor vessel, an intermediate heat exchanger that is a reactor internal structure A nuclear reactor characterized in that the heat exchanger and main circulation pump are fixedly supported by the core support structure, and the load of the intermediate heat exchanger and the main circulation pump is borne by the entire core support structure with only the horizontal supporting action of the roof slab. structure.