JPS60107593A - Automatic stop device for nuclear 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 the Invention] The present invention provides an atom system that detects the coolant temperature and automatically scrams when the normal reactor shutdown system does not scram during an accident in a fast breeder reactor. Regarding automatic furnace shutdown equipment.

[Technical Preface of the Invention] Generally, a nuclear reactor controls the output by inserting a control rod containing a neutron absorbing material into the reactor core, but in the event of an emergency such as an accident, the control rod must be fully inserted into the reactor core. The furnace is configured to avoid shutting down the furnace output.

Since it is necessary for the automatic reactor shutdown system to reliably stop the operation of the reactor in an emergency, it is required that the structure is such that each part can operate reliably. Therefore, this device includes a reactor shutdown system that operates based on the scram signal output to the reactor shutdown system using electric circuits such as logic circuits and relays, and external equipment such as the control rod drive machine 414.
The U2ffi, 3
It is desirable to implement 4R heavy safety measures.

FIG. 1 shows a schematic example of a liquid metal cooled fast breeder reactor. In the same figure, the reactor core 2 is housed in the C1 reactor vessel 1.
This core 2 is supported by a core support structure 3. The upper end of the reactor vessel 1 is closed off by a shielding plug 4, and a coolant such as liquid sodium is contained within the reactor vessel 1.

The low-temperature coolant flows into the lower part of the reactor vessel 1 from the coolant inlet pipe 5, passes through the reactor core 2 from below and is heated, and the high-temperature coolant flows out of the reactor vessel 1 from the coolant outlet pipe 6. It flows out to the intermediate heat exchanger (not shown) and exchanges heat with the secondary coolant. The coolant, which has become low temperature through heat exchange with the secondary coolant, passes through the coolant outlet pipe 5 and is sent to the lower part of the reactor vessel 1, and thereafter circulates through this path.

A control rod assembly 7 is installed in the reactor core 2 together with a fuel assembly. Although the control rod assembly 7 actually includes a plurality of members, only one is shown in the figure. The shielding plug 4 is provided with a core upper machine 4t? The installation number is J8. A large number of measurement fins 10 are accommodated in a joint body 9 which is provided through the shielding plug 4. The tip of each of these measuring fingers 10 faces the upper surface of the reactor core 2, and a temperature detector (not shown) is installed at the tip.
etc., and are configured to measure the temperature of the coolant flowing out from the core 2. Note that the measurement finger 10 is led out of the reactor vessel 1 through a protection tube 11 and a penetration 12.

A control rod drive mechanism 13 is installed in the upper part of the upper core mechanism 8. Upper guide pipes 14 or 9A are installed from the lower ends of these control rod drive mechanisms 13, and these upper guide pipes 14 pass through the joint shell 9 to guide the control rod assembly 7 loaded in the reactor core 2. It is opposite to the upper end.

The control rod assembly 7 is connected to the lower guide tube 1 as shown in FIG.
5, and a control rod 16 housed in the lower guide tube 15 so as to be vertically movable.

A 1-inch transformer nozzle 1 protruding from the lower end of the lower guide pipe 15
7 penetrates the core support plates 18 and 19 and is inserted into the high pressure plenum 20 formed between them, and is prevented from being removed by the pressure of the cooling oil Δ in the high pressure plenum 2o. It has a link hold town structure. A portion of the coolant in the high pressure lunum chamber 20 is supplied to the entrance nozzle 1.
After cooling the neutron absorbing material 21 introduced into the lower guide tube 1 from 7 and housed in the control rod 16, the lower guide tube 14
flows into.

Further, a dash ram 22 is provided to protrude from the lower end of the control rod 16, and when the control rod 16 is lowered, the dash ram 22 enters into the dashbot 23 to provide a buffer. Inside the upper guide tube 14 is an outer extension tube 24.
The outer extension tube 24 is connected to the connecting rod 2.
The outer extension tube 2 is configured to be driven up and down by the control rod drive mechanism (13 in FIG. 1) via the outer extension tube 5.
A plurality of latch fingers 26 are provided at the lower end of 4. These latch fingers 26 are configured to be able to expand and contract in diameter, and when the diameter is expanded, they engage with the handling head 27 of the control rod 16 to hold the control rod 16, and when the diameter is contracted, they engage with the handling head 27. It is configured so that it can be disengaged from the

An inner extension tube 29 is provided inside the outer extension tube 24 via the heat-sensitive expansion body 28 , and this inner extension tube 29 is connected to the heat-sensitive expansion body 2 .
4i6 is constructed so that it moves up and down by 'C' according to the expansion and contraction of 8. A latch operating portion 30 is provided at the lower end of the inner extension @ 29, and when this latch operating portion 30 advances into the latch fingers 26, these latch fingers are expanded in diameter and engaged with the C handling head 27, and When the latch operating portion 3o is pulled out from within the latch finger 26, the latch fin force 26 is configured to contract in diameter C due to its own elastic force, and is configured to engage or disengage from the handling head 27.

Note that through holes 24a and 2 are provided in the side wall and upper end of the outer extension tube 24.
4b IJX installed and cooling 4 flowing inside the upper guide pipe 14
71 is made to flow along the surface of the heat-sensitive expansion body 28.

In the conventional automatic reactor shutdown system with this configuration,
During normal operation, the control rod 16 is moved into the core 2 by moving the outer extension tube 24 up and down by the control rod drive mechanism (13 in FIG. 1) with the lug inker 26 engaged with the handling head 27. It is inserted or withdrawn and the power of the reactor is controlled.

If the fuel outlet temperature becomes abnormally high due to fuel release, etc., the temperature of the heat-sensitive expansion body 28 will rise due to the coolant flowing as shown by the arrow in FIG. 26 and the latch operating section 30, the latch operating section 30 descends and comes out of the latch finger 26, and the engagement between the C1 latch finger 26 and the handling head 27 is released. As a result, the control rods 16 fall into the reactor core 2 due to gravity, causing the reactor to scram.

FIGS. 3 and 4 each show another example of the prior art.

In these examples, the control rod 16 is directly suspended from the connecting rod 25 by a pyromagnet 31, and when the curvature point of the electromagnet 31 is exceeded due to an abnormality in the ambient temperature, It utilizes the principle that the control rod 16 falls when it loses its magnetic force.

In other words, in the example of FIG.
From the upper part of the outlet of 2, connect the pipe 33 for introducing the coolant to the electromagnet 3.
It is pulled around to the 1st neighborhood.

In addition, in the example shown in FIG. 4, the control rod is fully withdrawn and the torpedo 31 is positioned near the upper end of the control rod 16, so that the coolant flowing out from the fuel 32 will not hit the electromagnet 31. That's what I do.

[Problems with Background Art] However, the above-mentioned conventional device having the combination J: sea urchin has the following drawbacks. That is, in the examples of FIGS. 2 and 4, the inner diameter of the upper guide pipe 14 covers only about 25% of the surrounding fuel outlet, as shown by the hatching in FIG. CJj is low, and the flow rate of coolant is low. In addition, since the cold coolant flowing out from the control rod 7 TRs the central part, there is a drawback that it is difficult for the thermal engraving body 28 and the pyromagnet 31 to detect the temperature rise of the coolant at the outlet of the fuel 32. .

Furthermore, in the example of FIG. 3, C routes a pipe 33 above a suitable number of fuels 32, but as shown in s2 in FIG. Since it is installed in a loaded area, it is difficult to route the piping 33. In addition, this part is not only directly connected to thermal striping between control rods, blanket fuel, or core fuel, but is also exposed to harsh thermal transient conditions such as reactor trings, and is used as a piping layer. Therefore, as the structure becomes more complex, its structural reliability decreases.

Furthermore, due to the pipe structure, the flow path pressure loss increases, the flow rate of the coolant decreases, and not only is it not possible to obtain a sufficient temperature shift, but also the time required for the coolant to reach the pyromagnet 31 is delayed.

Next, let's take this as an example of a 100100O class nuclear reactor.
Explain quantitatively.

The coolant flow rate per core fuel during normal operation is approximately 30
kg/s, and the fuel outlet temperature that can be suppressed in the event of an abnormality is 6
50℃, while the control rod is about 10kg/5T420℃. This is calculated as Mtn for the above 25% inclusive case (this is based on an experimental reactor, and is approximately 0% in a large reactor). Assuming that the coolant flows in proportion to the area, the fuel outlet temperature is (30 dazzles/'s Xo, 25 x 6 x 650
℃＋420℃×10kg/s＞÷(30kg/S
X O, 25 x 6 pieces + 10 kg/s) = 608°C. Incidentally, the nuclear reactor is in an overpower state even during normal operation, and the temperature in that case is about 600°C to 620°C. Therefore, since the C1 fuel outlet cooling section may come into direct contact with the temperature-sensing section, there is a risk that the temperature-sensing sensor will work and cause a scram in this case even in the over-output state of normal operation.

[Object of the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks in the background art and to obtain a highly reliable nuclear reactor automatic shutdown device.

[Summary of the Invention] That is, the automatic reactor shutdown system of the present invention directly detects an abnormality in the fuel outlet temperature and automatically prevents control rods from falling into the reactor core. The inner diameter near the lower end of the upper guide tube of the mechanism is an inner diameter that includes more than half of the outlet area of the fuel rod adjacent to the control rod.
It is characterized by the presence of

[Embodiments of the Invention] Hereinafter, the present invention will be described in detail with reference to FIGS. 6 to 12. In these figures, the same members as J3 and -C in FIGS. 1 to 5 are given the same reference numerals.

In Fig. 6, a non-driving head is installed at the upper end of the A3 C1 control rod 16.
1 and suspended from the connecting rod 25. The upper guide tube 140, which opens at the upper ends of the control rod assembly 7 and the fuel 32, has a large diameter section 14a near the F end. C 50% of the area of the outlet of the fuel 32 that touches the corner as shown in J
The dimensions include -C.

In this case, the average temperature of the cold kj material reaching the temperature sensing part (cured pyromagnet 31) is calculated from the above and IFi1's ΔI calculation (30 kg/S x 0, 5 x 6 pieces x 65
0'C+10 kg/5X420℃)÷(30kr,
/s xo, 5x6 + 10 yen/S>-627°C. Therefore, by setting the operating point of the temperature sensing section to 627°C, 'Ca'i, the operation point of Tongfu's over-output state can be reduced.
Since the temperature is over 0℃, there is no risk of an accidental scram, and even if the temperature is below 650℃, which we want to keep in case of an abnormality, we can definitely avoid a scram.

In the embodiments shown in FIG. 8 J5 and FIG. 9, the upper guide tube 1
4 large diameter rjB 14 There are 78 cue points in a 3
A plurality of plate-shaped kites 34 for preventing the control rod 1G and the control rod 1G from coming into contact with the inner surface of the large diameter portion 14a are installed at appropriate intervals through the base 1) 35.

A measurement-resistant finker 10 JJ'Y shell is inserted between these guides 34 and the large diameter portion 14a.

Kite 34 (Ikuno is as follows.

In other words, as explained in FIG. In the example, the diameter of the 1011 guide answer 14 is expanded near the lower end, and the C large diameter portion 14 is expanded.
A and C, there is an interference between this large diameter portion 14a and the finger 10. Therefore, in this embodiment, the iI measuring fin 10 is inserted into the large diameter portion 14a to solve the problem of interference with the outer surface of the large diameter portion. In this case, the kite 34 is made thin (so that even if the weak four-point finger 10 comes into contact with the torpedo magnet 'ci31, which is eccentric, as shown by the chain line C in FIG. 9, it will not be damaged). The guide 34 serves to protect the large diameter portion 14a, and can also be used to improve earthquake resistance.

In embodiment a) C shown in FIGS. 10 and 11, an acceleration tube 36 for accelerated falling is fitted into the outer extension tube 24, and the guide 34 is as shown in FIG. To,
4ILIi has a shape that is gently curved inwardly convexly. The curved shape of these guides 34 is similar to that of the acceleration tube 36 when the pan 1-ring head 27 is inscribed in the kite 34.
Regardless of the position of the lower end of C, the geometric shape is such that there is always a portion where the two overlap.

In this embodiment, when the control rod 16 falls alone and is accelerated by the acceleration tube 36, the diameter of the control rod 16 and the diameter of the lower end of the acceleration tube 36 are changed to the shape of the blade 36. In consideration of the above conditions, the acceleration tube 36 will not overtake the control rod 16 when the control rod 16 falls, and the control rod 16 will surely accelerate and fall.
Wear.

Note that the guide 34 may be replaced with an intermittent spiral flow 237 as shown in FIG. η, that is, the large diameter portion 14 of the upper guide tube 14 as described above. Inside a is a low-temperature cooling N1 of about 420°C from the control rod 16 and a 580°C coolant from the fuel.
In this case, the 8-temperature cooling water from the control rod 16 flows in. If only FJ+ BL cold 211j hits the temperature sensing part, it will not be possible to set 1 due to abnormal fuel outlet temperature. It is possible to control the flow and control the flow (it is necessary to pre-mix the flow, as shown in Figure 12). The control rod outlet coolant is mixed to provide a stable flow of temperature (q), resulting in a highly reliable automatic reactor shutdown system.

[Effects of the Invention] As explained above, according to the automatic nuclear reactor shutdown device of the present invention, the 1tIi structure is simple, the combustion)'31;l+D cooling can be sufficiently introduced into the temperature sensing part, and mixing is prevented. It is possible to obtain a cooling system in which the temperature is averaged, and an automatic shutdown of the Kyoshi reactor that is not only highly reliable without malfunctions but also stable in terms of tub construction strength.

[Brief explanation of the drawing]

Figure 1 shows the schematic configuration of the fast breeder reactor.
Figures 4 to 4 are J8 vertical cross-sectional views illustrating conventional automatic reactor shutdown devices, respectively, Figure 5 is a cross-sectional view for explaining their operation, Figures 6, 8-3, and 10. 7, 9 and 11 respectively show an embodiment of the present invention, and 7, 9 and 11 show the J3 line and IX in FIG. 6, 8 J3 and 10, respectively. -IX-ray O, J:bi-X
FIG. 12 is a cross-sectional view taken along the line l-XI, and FIG. 12 is a cross-sectional view of another embodiment of the present invention. 7... Control rod assembly 8...
......Core upper mechanism 10...
・・h1 Measuring fin force 11・・・・・・・・・・Protective tube 13・・・・・・・・・・Control rod drive is 41 ri 14
・・・・・・・・・・・・Dobe guide pipe 15・・・・・・
...Lower t'lB guide tube 16...
・・・Control rod 17・・・・・・・・・En 1 Herans nosuru 2
4......Outer extension tube 25...
...... Connecting rod 28 ...... Heat-sensitive engraving body 29 ...
・・・・・・Inner extension n31・・・・・・・・・
・・Cute dim sum magnet 32 ・・・・・・・・ Burning angle 34 ・・・・・ Guide 35 ・・・・・・・・・・・ Spacer 36...
・・・・・・・・・Acceleration color 37・・・・・・・・・Fluid wing agent Sa Suyama - Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11

Claims (3)

[Claims] (1) In an automatic reactor shutdown system that directly detects an abnormality in fuel outlet temperature and automatically drops a control rod into the reactor core, the inner diameter near the lower end of the upper guide tube of the control rod drive mechanism is adjacent to the control rod. An automatic nuclear reactor shutdown system characterized by having an inner diameter that includes more than half of the exit area of a fuel rod. (2) The automatic reactor shutdown system according to claim 1, wherein a guide is provided near the lower end of the upper guide tube to prevent contact between the control rod and the measurement finger of the control rod drive mechanism. . (3) Near the lower end of the lower guide tube, a fluid flow tank is disposed to combine the coolant flowing out from the control rods and the coolant flowing out from the fuel. Nuclear reactor automatic shutdown device as described in section.