JPS5913979A - Fuel assembly of fast breeder - 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 invention] The present invention relates to a fuel assembly for a fast breeder reactor.

[Technical background of the invention]

A conventional example will be explained with reference to FIGS. 1 to 4. 1st
The figure is a diagram showing a schematic configuration of a fuel assembly. In the figure, 1 indicates a trumpet tube. An entrance nozzle 3 is provided at the bottom of a handling head 2 at the top of the ratchet 1. The handling head 3 is configured such that its internal shape matches the tip of a refueling machine (not shown). In addition, a plurality of coolant inlets 4 are provided on the side of the entrance nozzle 3, and in combination with a connecting pipe between two core support plates (not shown) as core support structures, the coolant is injected. This is a configuration that adjusts the flow rate. A plurality of fuel bottles 5 are provided in the trumpet tube 1 in the form of a triangular lattice. As shown in FIG. 3, this fuel bottle 5 houses a plurality of cylindrical pellets 7 made of sintered uranium dioxide powder in a cladding tube 6, and seals the upper and lower parts with an upper end plug 8 and a lower end plug 9, respectively. This is the configuration. A wrapping wire 10 is spirally provided around the outer periphery of the fuel bottle 5, and its upper and lower ends are connected and fixed to the upper end stopper 8 and the lower end stopper 9, respectively. The wrapping wire 10 maintains a constant distance between the fuel pins 5, allowing the coolant to flow uniformly and achieving uniform cooling.

The cladding tube 6 is made of 20% cold-worked 5US316, while the wrapping wire 10 is made of SUS304 solution-treated material.

Generally, several methods are used to maintain a constant distance between the fuel pins 5. A first method is to maintain a constant distance between the fuel pins 5 by inserting thin support tubes (not shown) between the fuel bottles 50. A second method is to support each fuel pin 5 with a grid.

A third method is a method using the wrapping wire 10 mentioned above. This method using the wrapping wire 10 is easier to manufacture than the first and second methods.
It is generally widely adopted because the pressure loss during coolant flow is small.

[Problems with background technology]

In fast breeder reactors, fast neutrons cause material swelling (volume expansion). As shown in FIG. 3, the amount of swelling due to this swelling phenomenon depends on the amount of neutrons and temperature, so the amount of p-swelling varies depending on the neutron distribution and temperature distribution occurring within the reactor core. Figure 3 shows the temperature distribution, neutron flux distribution, and SU
It is a figure showing the swelling amount distribution of S316. As described above, the cladding tube 6 of the fuel pin 5 is made of 20% cold-worked SUS 316, while the weaving wire 10 is made of 5US304 solution-treated material. Therefore, the swelling characteristics of the above two types are different, and changes occur in the longitudinal direction υ due to swelling and thermal expansion, and as a result, the pitch interval of the wrapping wire 10 changes, and at the end, a slack portion is formed as shown in FIG. There was a problem that occurred.

[Purpose of the invention]

An object of the present invention is to prevent the wrapping wire from loosening at the end of the period of use and to maintain the spacing between the fuel pins during the period of use by constructing the wrapping wire with a material having excellent anti-swelling properties. The purpose of this invention is to provide a fuel assembly for a fast breeder reactor that can be used.

[Summary of the invention]

The fuel assembly for a fast breeder reactor according to the present invention houses a plurality of fuel pins in a rat flat tube connected to the handling head at the upper end and the entrance nozzle at the lower end, and the outer periphery of the fuel bin is made of austenitic stainless steel containing titanium. The structure includes a wrapping wire made of solution-treated material.

Therefore, it is possible to obtain a wrapping wire that is resistant to volumetric expansion, to prevent the wrapping wire from loosening at the end of the period of use, and to maintain the spacing between the fuel pins during the period of use.

5- [Embodiment of the Invention] An embodiment of the present invention will be described with reference to FIGS. 5 to 8. FIG. 5 is a diagram showing a schematic configuration of a fuel assembly.

In the figure, 101 indicates a trumpet tube. An entrance nozzle 103 is provided at the upper part of the f-tube 10 and at the lower part of the nozzle handling head 102. The above-mentioned handling head iox is configured such that its internal shape matches the tip of a refueling machine (not shown). In addition, the entrance nozzle 103 side'WIK is provided with a plurality of coolant inlets 104, and serves as a core support structure.
The structure is such that the flow rate of the coolant is adjusted in combination with a connecting pipe between two core support plates (not shown). A plurality of fuel pins 105 are provided in the shape of a triangular lattice inside the wire tube 10. As shown in FIG. 6, this fuel pipe 105 houses a plurality of cylindrical pellets 107 made of sintered uranium dioxide powder in a cladding tube 106, and has upper and lower end plugs 108 and 109, respectively. Sealed configuration 6-. A wrapping wire 110 is spirally provided around the outer periphery of the fuel pin 105, and its upper and lower ends are connected and fixed to the upper end plug 108 and the lower end plug 109, respectively.

Then, by this wrapping wire 110, the fuel pin 1
05 is kept constant to allow the coolant to flow uniformly, thereby achieving uniform cooling.

The wrapping wire 110 is manufactured by using austenitic stainless steel to which 0.045% titanium is added as a solution-treated material without cold working.

The fact that the wrapping wire 110 according to the present invention has swelling resistance will be explained below based on two experimental results. First, the first experiment was to measure the distribution of swelling amount depending on the amount of titanium added. The samples used were 2
Making ingots with variable frequency by variable frequency vacuum melting 11
After hot rolling at 50°C, annealing was performed at 1150°C for 15 minutes. Then, it was machined to a thickness of 0.15+ m by mechanical polishing, subjected to solution treatment at 1200° C. for 10 minutes in an argon stream, and then finished by electrolytic polishing. The titanium concentration range is from 0.01% to 0.2%, and the composition other than titanium is the same as SUB 316 stainless steel. The irradiation was 24 appm'l (62 appm after pre-injection).
38 dpi (=I
01 ions at 200 keV with g≧0.1 MeV) were irradiated. The swelling charge of each sample was then observed using an electron microscope. As a result, as shown in FIG. 9, when the titanium concentration is around 0.2%, the amount of swelling is approximately O, indicating high swelling resistance. On the other hand, a high h-swelling amount is shown at a titanium concentration of around 002%.

Further, it can be seen that variations are observed when the titanium concentration is between 0.02% and 0.03%, but when the titanium concentration is 0.03% or more, the amount of swelling is small and the material has swelling resistance. In other words, a very small amount of titanium is added (0.045% in this example).
), it can be seen that the swelling resistance is improved.

The second experiment measured the effect of cold working on the swelling properties of titanium-added 5U8316 stainless steel. The sample used in the first experiment was one with a titanium concentration of 0.045%, and after solution treatment at 1200°C for 10 minutes, the titanium concentration was 20%.
cold worked. The irradiation was carried out in the same manner as in the first experiment, and the swelling charge of samples subjected to cold working and samples subjected to cold working with only solution treatment was observed using an electron microscope. As shown in the figure, the amount of swelling in the cold-worked sample increases as the irradiation charge increases, whereas the sample that was not cold-worked shows only a very small amount of swelling. It can be seen that it has high swelling resistance.

As is clear from the experimental results in Box 1 and 2 above, when austenitic stainless steel to which a trace amount of titanium, for example 0.045% titanium is added, is used as a solution-treated material without cold working, it has high resistance. It can be seen that it has swelling properties.

Snap Wrapping Wire 110'ii O,045
To prevent the wrapping wire 110 from loosening at the end of the fuel assembly usage period by manufacturing the austenitic stainless steel to which 9-% titanium is added as a solution-treated material without cold working. This makes it possible to maintain the spacing of each fuel pin/105 during the use of the fuel assembly.

In the above embodiment, all of the wrapping wires 110 are 0.04
Although it is made of austenitic stainless steel to which 5% titanium is added and subjected to only solution treatment, it is also possible to make only one thick part of the swelling amount from the above material.

Also, the amount of titanium added is not limited to 0.045%, but 0.03%.
% or more, similar effects can be obtained.

〔Effect of the invention〕

The fuel assembly for a fast breeder reactor according to the present invention houses a plurality of fuel pins in a wrapper tube with a two-handling head at the upper end connected to an entrance nozzle at the lower end, and the outer periphery of the fuel bin is made of austenitic stainless steel containing titanium. The structure includes a wrapping wire made of solution-treated steel.

Therefore, it is possible to obtain a wrapping wire that is resistant to volumetric expansion, to prevent the wrapping wire from loosening at the end of its use period, and to maintain the spacing between the fuel pins during its use period. .

[Brief explanation of drawings]

N< Figures 1 to 3 are diagrams showing conventional examples, in which Figure 1 is a perspective view of a fuel assembly, Figure 2 is a sectional view taken along the line ■-n in Figure 1, and Figure 3 is a front view of a fuel pin. Figure 4 is a diagram showing the temperature distribution, neutron flux distribution, and swelling amount distribution of the core in the Rhapsody reactor (France), Figure 5 is a front view of the fuel pin with the wrapping wire loosened at the end of use, and Figures 6 to 6 FIG. 10 is a diagram showing an embodiment of the present invention, FIG. 6 is a perspective view of a fuel assembly, FIG. Figure 9 is a diagram showing the distribution of the amount of swelling due to changes in titanium concentration, and Figure 10 is a diagram showing the difference in swelling between cold working and cold working. 101...Ratsuno 4Ws102...Handling spatula y, 1os...Entrance nozzle, No05...
Fuel pin, 110...wrapping wire. Applicant's representative Patent attorney Takehiko Suzue, 1-5 figures, 6 figures, 9 B -421- 10 figures (dpa)

Claims (2)

[Claims] (1) Fuel consisting of a rat/f pipe with a handling head connected to the upper end and an entrance nozzle at the lower end, a plurality of fuel bottles housed in this wrapper pipe, and a wrapping wire wound around the outer circumference of the fuel bin. In the collective,
A fuel assembly for a fast breeder reactor, wherein the wrapping wire is made of a solution-treated austenitic stainless steel material containing titanium. (2) The fuel assembly 0 for a fast breeder reactor according to claim 1, wherein the wrapping wire is made of a solution-treated austenitic stainless steel material to which 0.045% titanium is added.