JPH046495A - Fast breeder reactor - Google Patents

Abstract

PURPOSE:To reduce temperature fluctuation in a welded part fixing a support pipe plate in the lower end part of a core upper mechanism and a straightening tube by a method wherein a low-temperature coolant flowing out between support pipes from a control rod is made to gush out into an upper plenum. CONSTITUTION:A high-temperature coolant flowing out of a fuel assembly 7 in a core and a low-temperature coolant flowing out of a control rod 10 are separated into main channel paths by support pipe plates 30 and 53. In other words, the high- temperature coolant flowing out of the fuel assembly 7 passes inside a straightening tube 31, gushes out into a pipe-plate upper plenum 56 and runs out into an upper plenum 12. Part of the high-temperature coolant not flowing into the straightening tube 31 passes through a pipe-plate lower plenum 55 and runs out into the upper plenum 12. Meanwhile, the low-temperature coolant flowing out of the control rod 10 flows mostly into an upper guide pipe 51, flows out into a pipe-plate intermediate plenum 54 between the support pipe plates 30 and 53, flows in the radial direction and runs to the upper plenum 12 around a core upper mechanism 29. According to this constitution, the high-temperature and low-temperature coolants are mixed in a fluid field which is located outside the core upper mechanism 29 and wherein no structural material of the upper plenum 12 exists.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention reduces temperature fluctuations in the upper core mechanism of a fast breeder reactor that uses liquid metal (metal) as a coolant. Regarding fast breeder reactors.

(Prior Art) FIG. 4 shows a schematic configuration of a conventional loop type fast breeder reactor. That is, a reactor core 2 is provided inside the reactor vessel 1, and a coolant (liquid sodium) 3 is accommodated therein. The reactor vessel 1 has a coolant inlet nozzle 4 at the bottom, a coolant outlet nozzle 5 at the peripheral wall, and the upper opening is closed with a shielding plug 6.

The core 2 includes a core fuel assembly (hereinafter simply referred to as a fuel assembly) 7, a blanket fuel assembly 8, a reflector 9, and a control rod 10, and is supported on a core support 11. The inside of the reactor vessel 1 is divided into an upper plenum 12 and a lower plenum 13 by the core support 11 . The high pressure plenum 15 provided at the lower part of the reactor core 2 is a deep plate provided on the lower surface of the shielding plug 6, and 16 is a required gap 17 between the inner peripheral wall and the inside wall of the reactor vessel 1. A plurality of flow holes I8 are formed in this inner cylinder 14.

FIG. 5 shows a longitudinal section of the fuel assembly 7 in FIG. 4. That is, at the top and end of the hexagonal trumpet tube 1g (
To one end of the trumpet tube 19, a small diameter transformer nozzle 21 is attached. There are many fuel vinyls inside the trumpet tube 19/2:)
1, in which reference numeral 23 indicates a fixing plate C for fixing these fuel bottles 22 inside the trumpet tube 19, and 24
is a wire spacer that forms a predetermined gap between the fuel bottles 22.

A coolant outlet 25 is formed in the handling outlet 20. The transformer nozzle 21 is closed at its lower end and has a plurality of coolant inlet orifices 26 on its peripheral wall. The fuel assembly 7 configured in this way is constructed by inserting the entrance nozzle 21 into the connecting pipe 27J of the high pressure blenum 14. It is loaded in a predetermined position.

An orifice 28 is formed in the connecting pipe 27 and communicates with the coolant inflow orifice 26 of the entrance nozzle 21 .

A core mechanism 29 is attached to the shield plug. This is for replacing the fuel polymer 7, which is a component of the reactor core 2.
戊 has been. The code 30 is part 1 of the core-1 mechanism 29.
Edge 1. Installation (even the first support plate 1, - support tube plate 30
For each fuel t1 assembly 7, a plurality of rectifier tubes 31 are welded in front of the row (1, which is more firmly fixed, and the symbol 3:! has a smaller welded part. The cylinder 31 is configured to face downward from the support tube plate 30, the protrusion 5, and the cooling +Δ outflow L12.5 of each fuel assembly 'i from the V direction. A coolant flow D33 is formed at the intermediate position of the mounting portion of each rectifying tube 31, and the lower part of the instrumentation tube 34 is introduced into the rectifying tube 31. In the figure, T11 is the fuel The assembly is represented by ']'C represents the control rod.

Cooling 1 with fast growth and odor configured as follows.
The coolant 3 flows from the entrance nozzle 4 through the high pressure lennum 14, passes through the inlet orifice 28, 26, and enters the entrance nozzle 21. (l) flows in the trumpet tube 19 in the f direction, and as it passes between the many combustion pins 22, it is given nuclear reaction heat and is cooled by tr + A flows out from the outflow l] 25. .Here ζ゛, each fuel #E+ assembly 7 loaded in the core 2 has a different calorific value depending on its loading position.
The flow rate distribution for each fuel assembly 7 is determined so as to equalize the temperature property 4 of the coolant 3 in the upper part and increase thermal efficiency.

Outflow from the coolant outlet 25 1. The high temperature coolant 3 is passed through the cooling nozzle 5 to I1. It flows out of the reactor vessel 1, and the heat exchanger and circulation port installed outside the reactor vessel 1.
(none of which are shown), etc. are cooled and refluxed to the nozzle 4 again.

(Problems to be Solved by the Invention) In the fast breeder reactor configured as described above, the temperature of the coolant flowing out from each fuel assembly 7 is not constant. In addition, since there is also a temperature difference between the fuel assembly 7 and the guide tube of the control rod 10 adjacent thereto, the lower end ζ of the core upper mechanism 2g, the straightening tube 31 is affected by the temperature difference between them, resulting in a temperature fluctuation △φ expressed as T/゛d, -T.This temperature fluctuation Δφ is about 60% of the temperature difference, and is about 1H2. 3, where T, T2 is the temperature of the coolant flowing from two adjacent fuel assemblies 7 and control rods IO, and ΔT is a.

It shows the temperature amplitude at each position between 10 and 10 degrees.

. In FIG. 6, symbol C: indicates a mixture of coolants having different temperatures flowing out from two adjacent fuel fuel assembly 7 and control rod 10. Shows you where to start. This zero point is located between two adjacent rectifier cylinders 31,31. Further, the symbol l) indicates a point above the 0 point at the 1 position on the lower surface of the support tube sheet 30 (5,
aL! Point A on the upper surface position of the fuel assembly 7 is shown as point A, and the temperature fluctuation distribution on the line connecting these points a, b, and c is shown in FIG. 4. In other words, temperature fluctuations occur above the 0 point (at points 7 and 5, there is some attenuation, but the amount of attenuation is small. The area surrounded by a mesh in Figure 3 is the highest temperature; the fluctuation is the largest. 1. -F-12, Due to temperature fluctuations like this, the ends of some of the mechanisms 29 in the core 1 may suffer from excessive thermal fatigue, especially due to thermal striping of the structural members. The welded part 32 that fixes the support tube plate 30 and the rectifier tube 31, !l: is a part that is vulnerable to heat damage, and cracks can occur easily.

The present invention has been made to solve the above problems, and reduces the temperature fluctuation Δφ in the welded part that fixes the support tube plate and the rectifier tube at the lower end of the upper core structure, thereby preventing cracks etc. from occurring in the welded part. The purpose of this invention is to provide a highly safe fast breeder reactor that prevents this from occurring.

[Structure of the Invention] (Means for Solving the Problems) In the present invention, a rectifier cylinder provided at the lower end of the core upper mechanism is arranged so as to face the handling head at the upper end of the fuel assembly loaded in the reactor core from above. In a fast breeder reactor equipped with a guide tube into which coolant flowing out from a control rod flows and a support tube sheet that supports the straightening tube, a second support tube sheet is provided with a space below the support tube sheet. The present invention is characterized in that the low-temperature coolant flowing out from the control rods flows out from between these support tubes into the upper plenum.

(Function) The difference between the coolant outlet temperature of the handling head of each fuel assembly loaded in the core and the outlet temperature of the control rod assembly (ΔT
), the low temperature coolant flowing from the control rods is directed into the upper guide tube and jetted into the tube plate intermediate plenum. Then, the coolant flowing out from the core fuel assembly through the straightening tube and the temperature coolant jetted from outside the straightening tube through the tube plate lower plenum into the upper plenum are mixed in the upper plenum outside the core upper mechanism. This reduces the temperature fluctuation Δφ that occurs on the lower surface of the lower support tube plate and the side surface of the rectifier tube, prevents the occurrence of cracks due to thermal fatigue, and improves the long-term integrity of the fast breeder reactor. .

(Example) An example of a fast breeder reactor according to the present invention will be described with reference to FIG.

In FIG. 1, only the main parts of the present invention are shown, and the same parts as in FIG. 6 are given the same reference numerals, and the explanation of the overlapping parts is omitted.

That is, in FIG. 1, the second support tube sheet 53 is provided below the first support tube sheet 30, and the rectifying tube 31 is connected to the support tube sheet 3.
0, configured to penetrate through the second support tube sheet 53. The upper guide tubes are arranged in rows above the first support tube sheet 30 and below the second support tube sheet 53.

A control rod connecting rod 52 is inserted into the control rod 10, and the amount of heat generated in the core is controlled by vertically driving a control element (not shown). Further, the core fuel assembly 7 is provided with a fuel pin 22 and a neutron shield 35 above the fuel pin 22.

In the fast breeder reactor of the above embodiment, the fuel assembly 7 of the core
The high temperature coolant flowing out from the control rods 10 and the low temperature coolant flowing out from the control rods 10 are transferred to the first support tube sheet 30 and the second support tube sheet 5.
3 separates the main flow paths. That is, the high-temperature coolant flowing out from the fuel assembly 7 of the reactor core passes through the inside of the straightening tube 31, is ejected into the tube plate upper plenum 56, and flows out into the upper plenum 12. Further, a portion of the high-temperature coolant that does not flow into the straightening tube 31 passes through the tube plate lower plenum 55 and flows out into the upper plenum 12. On the other hand, most of the low-temperature coolant flowing out from the control rod 10 flows into the upper guide tube 51, and the tube sheet intermediate plenum 54 between the support tube sheet 30 and the second support tube 53
and flows radially into the upper plenum 12 around the upper core mechanism 29. In this way, the high temperature coolant flowing out from the fuel assembly 7 of the reactor core and the low temperature coolant flowing out from the control rods 10 are transferred to the core upper mechanism 29 and the support tube plate 3 at the lower part.
0 and the second support tube plate 53 to mix the high temperature and low temperature coolant in a fluid base free of the structural members of the upper plenum 12 outside the upper core structure 29. As a result, structures such as the core upper mechanism 29, the rectifier cylinder 31, and the support tube plate 30 can be protected from thermal fatigue caused by thermal striping, and the integrity of the fast breeder reactor can be improved. In this first embodiment, the temperature fluctuation is greatest in the area where the high-temperature coolant and the low-temperature coolant are mixed, which is indicated by the mesh in the figure. However, since this is not a location where structural materials exist, thermal fatigue due to thermal striping does not occur.

Next, another embodiment of the present invention will be described with reference to FIGS. 2 and 3.

Note that the same parts as in FIG. 1 will be described using the same reference numerals. That is, in FIG. 2, the upper guide tube 51 of the control rod 10 is separated into two parts by the support tube plate 30 and the second support tube plate 53. As in the book, the control rod 10 is flown out L2, the upper guide tube 51 is inflow j, the low temperature cooling 1 is flowed out from the low temperature pipe I: 2-hole 57 to the tube plate intermediate Solena t1, and the flow path is set to the high temperature side. , the low-temperature side C is separated in the same manner as in the first embodiment, but one part of the guide tube 51 is divided into 6 pieces by the support tube plate 30 and the second support plate 53.
Therefore, there is no risk of misalignment of the divided L-portion guide tubes due to thermal deformation, etc., and the insertability of the control rod 10 is not impaired.

Thermalst that responds to temperature fluctuations.To prevent fibbing, the temperature is adjusted between the upper bream 12 and away from the structural members.
As with the first embodiment, the ++-Mars driving caused by the temperature fluctuations that cause song can be reduced.

[Effects of the Invention] According to the present invention, a second support tube plate is provided at the lower part of the section mechanism in the core located at the outlet 1-] of the high-temperature coolant of the control rod of the fuel assembly. 11. Mix the coolant for the Hayabusa combination and the control rods in the part of the upper brenum that does not have structural members (radially outward). .

, To prevent thermal fatigue due to thermal fatigue from occurring in the F part of the upper core mechanism (, 7"), to prevent the occurrence of cracks due to thermal fatigue in structural materials 4 Ruko, 1- is "("
In addition, if the thermal fatigue due to temperature fluctuations can be reduced, the rectifier tube, support tube plate, etc. can be made using expensive materials such as fatigue-resistant insulation panels. The weldability and weldability are also better than the tJ stage.
Since it can be made using steel, it is also possible to reduce costs during production. 7

[Brief explanation of the drawing]

FIGS. 1 and 2 are side views showing the main parts of each embodiment of the fast breeder reactor according to the present invention, respectively. Figure 4 is a schematic vertical cross-sectional view showing the conventional θ) fast breeder reactor; Figure 5 is a vertical cross-sectional view showing the fuel assembly in Figure 4; Figure 4 is a side view showing the lower part of a part of the reactor core 1 in cross section, and Figure 7 shows the axial characteristics of temperature fluctuations in a conventional fast breeder reactor. ~
It is a characteristic diagram. 1... Reactor vessel 2... Core 3... Coolant 4... Input 1 nozzle 5... Output I-1 nozzle 6... Shielding plug 7... Core fuel 1 assembly 8... Branwood fuel assembly 9... Reflector 0... Control rod 1... Core support 2... Upper blennium 3... Lower blennium 4... High pressure beam L/Num 5 ...Dip doble - Toro...Inner cylinder 7...Gap...Flow hole 9...Trumpet tube 20...Handling head 21...Ln) Run snorzzle 22... Combustion wood + 1 bottle 23... Fixed plate 24... Wire spacer 25... Cooling 1 output [1 26... Coolant inflow orifice 27... Connecting pipe 28... Orifice 29... Core Upper mechanism 30... Support tube plate 31... Rectifier tube 32... Welding section 33... Coolant distribution [J 34... Instrumentation well 35... Neutral shielding body 51... 1 Part guide tube 52...Control rod connecting rod 53...Second support tube plate 54...Tube plate intermediate section 55...Tube plate lower plenum 56...Tube plate upper plenum 57...Low temperature flow hole

Claims (1)

[Claims] A rectifier tube provided at the lower end of the core upper mechanism is arranged to face the handling head at the upper end of the fuel assembly loaded in the reactor core from above, and a guide tube into which the coolant flowing out from the control rods flows and the rectifier tube are arranged to face each other from above. In a fast breeder reactor equipped with a support tube sheet that supports a cylinder, a second support tube sheet is installed below the support tube sheet with a space therebetween, and the low-temperature coolant flowing out from the control rod is collected between these support tube sheets. A fast breeder reactor characterized in that the reactor is configured such that it flows out into an upper plenum.