JPS58199139A - Manufacture of composite coating pipe - 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 The present invention relates to nuclear reactor fuel elements, and more particularly to a composite cladding that includes a zirconium barrier on the inner wall surface of the zirconium alloy cladding.

Currently, nuclear fuel for nuclear reactors is packed into various containers such as tubes or rods. In general, these containers have (a) excellent corrosion resistance, (b) from the usage conditions in nuclear reactors.
be non-reactive; (C) have good thermal conductivity; (
d) It is required to have good toughness and ductility up to a certain high temperature, and (e) it is required to have a small neutron absorption cross section. Hereinafter, the containers filled with nuclear fuel for these nuclear reactors will be referred to as fuel cladding tubes.

Zirconium alloys have a small neutron absorption cross section and good toughness and ductility. Additionally, this alloy has relatively good corrosion resistance against nuclear reactor cooling water, and is therefore widely used as a nuclear fuel product.

However, when the load fluctuations of a nuclear reactor are large, the zirconium alloy is corroded from the inside by nuclear fuel products (such as iodine gas) released from the nuclear fuel. Then, stress from the nuclear fuel pellets filled in the covering 4f acts, causing stress corrosion cracking in the covering duct.

It takes 1! As a measure to prevent this, attempts have been made to provide various types of gold-Rdlk between the fuel and the cladding tube. Among these, a composite cladding tube in which the inner wall of a zirconium alloy tube is lined with zirconium of a 4-grade purity is also considered to be promising. The thickness of zirconium, 11&, is approximately 5-30% of the tube thickness.Sirconitum is softer than zirconium alloys, reducing strain within the nuclear fuel element and preventing stress corrosion cracking. It is also an excellent feature that it does not cause large neutron capture penalties, heat transfer penalties, or material incompatibilities. , the vertical axis shows the position of the cladding tube with a zirconium barrier (■) and the stress δ (standard il), respectively. This figure shows that the presence of the 75 μm thick zirconium barrier significantly alleviates the stress applied to the cladding tube.

In such a composite cladding tube, it is extremely important that the thickness of the zirconium barrier is formed to a desired dimension.

Therefore, it is necessary to non-destructively measure the zirconium barrier thickness. However, there is a drawback that the eddy current or ultrasonic methods conventionally used to measure the thickness of composite pipes in general cannot be applied. That is, the physical properties of the zirconium alloy tube and the zirconium barrier are very similar, and
This is because the boundaries are metal bonded. Therefore,
There is a fuel cladding tube in which an acoustic effect is provided at the boundary between the zirconium alloy tube and the zirconium barrier, and the thickness of the zirconium barrier can be measured from the acoustic effect from this boundary. In addition, although the composite wave 4f with an acoustic effect is plastically unprocessed from the raw pipe, the acoustic boundary also deforms following the raw pipe, so that the characteristics as a fuel clad pipe are not impaired, and The acoustic boundaries must be continuous and uniformly distributed to allow for non-destructive measurement of the zirconium barrier thickness of the fuel cladding. However, although the acoustic inclusions formed with open ends on both end faces deform as the raw pipe undergoes plastic processing, they are pushed out from near the open ends in the regional processing direction, some of them flow out, and become intermittent. Since the distribution becomes non-uniform, continuous measurement of the zirconium barrier thickness becomes impossible.

Therefore, in order to continuously and non-destructively measure the thickness of zirconium injection, it is necessary to form an acoustic boundary on both end faces of the composite coated pipe so that it does not protrude.

The purpose of the present invention is to measure zirconium barrier thickness non-destructively.
The acoustic boundaries created to allow both Rf and RfjJK
Composite fuel cladding tubes are formed so that they do not leak out, are continuously and evenly distributed following the plastic deformation of the raw tube, and are metal-bonded at boundaries other than acoustic boundaries. It is possible to obtain.

The characteristics of the present invention are that the zirconium barrier thickness is set so as to be non-destructively measurable, and the acoustic boundary is uniformly distributed so that it is not exposed on both end faces during plastic working for manufacturing fuel cladding tubes. The object of the present invention is to provide a composite fuel-clad raw tube that can be formed by intervening.

That is, as schematically shown in FIG. 2, the present invention forms an acoustic inclusion 3 at the boundary between the zirconium alloy outer tube 1 and the zirconium inner tube 2 so as not to protrude from both end faces. After that, they are integrated to create a composite fuel cladding tube. In addition, in Fig. 2, the part that does not have a ring-4 boundary is a part where the zirconium barrier thickness cannot be measured non-destructively, so it is cut and removed after the cladding is completed. As such, zirconium alloys or zirconium substitutes can be used. At this time, it is necessary to perform metallic bonding with the ring 4 except for the acoustic boundary, and the ring 4 preferably has a recessed end face in order to improve tube expansion efficiency.

In general, there are two types of pipe expansion methods that expand an inner pipe and integrate it with an outer pipe: a roller pipe expansion method and an explosive pipe expansion method. However, since the roller tube expansion method rolls the inner surface of the tube, it causes hardening and distortion. In addition, the four-way tube expansion method has problems such as difficulty in applying it to tubes with small inner diameters, and doubts as to whether sufficient contact between the inner tube and the outer tube can be obtained in the axial direction. Therefore, in the present invention, by using a rubber tube expansion method that statically applies uniform pressure, the boundary between the zirconium alloy outer tube and the zirconium inner tube is
After intervening an acoustic clear field, they are integrated to produce a composite fuel-clad raw tube. In this way, the acoustic inclusions formed at the boundary between the zirconium alloy outer tube and the zirconium inner tube so that they do not protrude on both end faces do not flow out into the tube even in the case of plastic UQ processing of the tube. Since it deforms accordingly, it can be distributed continuously and uniformly.

In view of the above, the zirconium barrier type fuel if manufactured according to the present invention allows (2) non-destructive measurement of the zirconium barrier thickness after bonding without any delay.

Example (1) The outer tube is an am-1aa machined Zircaloy hollow billet with an outer diameter of 140.5 mm and an inner diameter of 69.6 mm, and the inner tube is also made by melting and td.
A groove with a width of 5 m and a depth of 0.3 wm is placed on the outer surface of a high-purity zirconium hollow billet with an outer diameter of 69.4 mm and an inner diameter of 4 & 4 mm, which has been cut and finished. Graphite powder with a particle size of 100 μm mixed with methyl cellulose was applied to the beak and dried.

Next, the soft d411 was shaped so that the graphite powder would not come out on both sides, and the contact surface with the Zircaloy outer tube-1 and the zirconium inner tube-2 was shaped like a rubber expanded tube 'TD. ! IJ/Goo 4 was prepared and installed in combination as shown schematically in FIG. Next, using a hairstyle press, cover both end faces of the boundary between the expanded rubber tube 1, the Zircaloy outer tube 1, and the zirconium inner tube 2 with a mild steel ring 4, and interpose graphite 3 so as not to expose the outer tube 1 to the outside. At the same time, a composite nuclear material cladding tube was fabricated in which the boundaries between the Zircaloy outer tube-11, the zirconium inner tube-2, and the mild steel ring-3 were metallurgically bonded.

After that, through the steps of hot extrusion, cold rolling, and annealing, the outer diameter is 1252 mm, the inner diameter is 10.80 mm, and the wall thickness is α86 mm.
A composite nuclear fuel cladding tube having graphite inclusions of 1 lIs and approximately 5 μm thick inside was fabricated, and the mild steel portions at both ends were cut and removed.

A composite fuel cladding tube with a length of 4,000 m according to the present invention,
Frequency 10MH! Measured using water immersion ultrasonic pulse reflection method,
The reflected echo from the coated tube was clearly observed on a cathode ray tube, and the result is shown in Figure 5g5. In addition, the signal output was recorded on a recorder. Figure 5 (a) is a reflected echo without inclusions, (b)
are reflected echoes from inclusions, and both reflected echoes were clearly seen. The zirconium barrier thickness distribution measured in this manner is shown in FIG. , (2) Example (1
), graphite was interposed on the outer surface of the zirconium inner tube. (
In 2), after interposing Zircaloy on the inner surface of the outer tube, a composite fuel cladding tube was prepared in the same manner as in Example (1).
The measurement results were also almost the same.

Although graphite has been described in the above embodiments, non-destructive measurement of the zirconium barrier thickness can be performed even if the inclusion is of a material other than graphite that has an acoustic seedling. Therefore, the present invention is applicable to all methods of manufacturing composite cladding tubes that allow non-destructive measurement of the zirconium barrier thickness.

[Brief explanation of the drawing]

Figure 1 is an orientation diagram of the cladding tube, Figures 2 and 3 are diagrams showing the shape of the cladding tube, Figure 4 is a diagram showing the mating structure, Figure 5 is a diagram showing reflected echoes, and Figure 6 is a diagram showing the shape of the cladding tube. is a diagram showing the zirconium barrier thickness distribution measured non-destructively. 1...Zircaloy outer tube, 2...Sirconi') mnf
, 3... Graphite, 4... Mild steel ring, 5... Tube expansion medium rubber, 6 (JL) (8) 4th eye hair 5 days

Claims (1)

[Claims] 1. A composite cladding tube made of a zirconium alloy, characterized in that a boundary having an acoustic effect that enables non-destructive measurement of the thickness of the zirconium barrier provided on the inner surface of the cladding tube is interposed so as not to be exposed on both end faces. $1! Construction method.