JPS6271801A - Standard sample for measuring thickness of oxide layer of zirconium-base alloy member - Google Patents

Abstract

PURPOSE:To obtain a standard sample for measuring the thickness of the oxide layer of a zirconium-base alloy member having good calibration accuracy and long life by providing an insulating oxide layer to a prescribed film thickness on the surface of the zirconium-base alloy. CONSTITUTION:Zr alloys such as zircalloy-2, -4, Zr-2.5%Nb and Zr-1%Nb known generally as the alloy for atomic reactors are usable for the zirconium-base alloy member. Any insulator is usable for the insulating oxide layer and is exemplified by ceramic layers of zirconium oxide, aluminum oxide, etc. A sample to be measured is a Zr alloy and plural pieces are preferably provided by using the zirconium oxide and changing the film thicknesses in order to measure the thickness of the oxide layer thereof. Since the specified thickness of the oxide layer is reproduced with the long life and high accuracy in the above-mentioned manner, the calibration with the extremely high accuracy is made possible.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention is based on a standard used for measuring the thickness of an oxidized layer formed on the surface of a zirconium-based alloy member used in a nuclear reactor. Regarding samples.

[Technical background of the invention and its problems]

Generally, in nuclear reactors such as boiling water reactors and pressurized water reactors, zirconium-based alloys are often used as structural members such as channel boxes and heating material cladding tube 1 spacers. Zirconium-based alloys have advantages such as a small neutron absorption cross section, good corrosion resistance in high-temperature water, and mechanical properties suitable as a material for reactor internal structure.

Zirconium-based alloy structural materials are used in harsh environments in reactors1, for example in boiling water reactors, temperatures of 28
Because it is exposed to neutron irradiation in boiling water at 9°C and a pressure cuff of 1 kg/Crd, the surface of the zirconium-based alloy produces speckled grayish-white corrosion due to a corrosion reaction called nosierer corrogene at the end of its use. things may occur. In such a state, the thickness of the healthy portion may decrease and the mechanical properties may deteriorate. For this reason, zirconium-based alloy members used in the reactor for a certain period of time are transferred to a fuel storage pool, and the health of the member is determined by measuring the thickness of the #1 layer.

As a method for measuring the thickness of the oxidized layer of this zirconium-based alloy member, non-destructive testing using eddy current is often used. The principle of this device is as follows.

When a coil carrying an alternating current is brought close to a conductive material such as metal, eddy currents are generated in the material due to electromagnetic induction. The strength of the eddy current generated in the material varies depending on the distance between the material and the coil, and the impedance generated in the coil changes in accordance with this distance.

By bringing the coil into contact with the surface of the zirconium-based alloy member on which the oxide has formed, the thickness of the oxide becomes equivalent to the distance between the coil and the metal surface (in this case, the Zr-based alloy), and the thickness of the oxide layer You can get output according to your needs.

Therefore, if a calibration curve between the chemical layer thickness and the output signal is obtained in advance using a sample with a known oxide layer thickness, that is, a standard sample, the oxide layer thickness can also be calculated for a sample with an unknown oxide layer thickness. can be found.

In measurements based on this vortex IIR principle, it is important to calibrate the thickness accurately, and for this purpose a highly accurate standard sample is required.

As a standard sample, a non-conductive tape such as a plastic film pasted on the surface of a zirconium-based alloy member is used because it is simple, but the non-conductive tape changes due to the contact pressure of the coil, resulting in inaccurate calibration. may occur. Furthermore, problems such as abrasion of the non-conductive tape due to contact with the coil and deterioration of the non-conductive tape in the fuel storage pool were common.

[Purpose of the invention]

The purpose is to provide a standard sample for measuring the oxide layer thickness of alloy members.

[Summary of the invention]

The present invention is a standard sample for measuring the oxide layer thickness of a zirconium-based alloy member in which an insulating oxide layer of a predetermined thickness is provided on the surface of a zirconium-based alloy.

The zirconium-based alloy member in the present invention is used as a structural member of a nuclear reactor such as a channel box, a fuel cladding tube, a spacer, etc., and the zirconium-based alloy is Zircaloy-2, which is generally known for use in nuclear reactors.
, -4, Zr-2,54Nb.

Zr alloys such as Zr-1%Nb can be used. The insulating oxide layer may be any insulator, and examples include ceramic layers such as zirconium oxide and aluminum oxide. Since the sample to be measured is a Zr alloy and its oxide layer thickness is to be measured, it is preferable to use zirconium oxide. - Furthermore, in order to obtain the calibration in+s with good accuracy, it is preferable to provide a plurality of insulating oxide layers with different thicknesses. Generally, the thickness of the oxidized layer that forms on the surface of a component at the end of its use is about 200 μm, so
The film thickness may be changed within a certain range. Note that since the roughness of the surface of this insulating oxide layer affects measurement accuracy, it is preferable that the surface roughness is 5 μm or less.

ZrO2, Al2O can be used as a means for forming the insulating oxide layer.
3 grade plasma spraying or 500~ in an oxidizing atmosphere
It is preferable to use an unirradiated member to be measured in order to form a ZrO2 film through oxidation by heating to about 750°C.

〔Effect of the invention〕

As explained above, according to the present invention, the measuring head can be adjusted correctly. Therefore, it is possible to appropriately determine the quality of structural materials within the nuclear reactor.

[Embodiments of the invention]

The present invention will be explained in detail below.

Using an unirradiated cursed fuel cladding tube (1) made of Zircaloy-2, outer diameter 12.4ml, inner thickness 0.91mm), the outer surface of the tube is machined to depths of 30μ, 50μ, 75μ, 100μ.
μ.

A 150μ groove (2) was made around the entire circumference of the tube (Fig. 1 (&)
. The width of each groove is 30 mm, and there is a 20 mm long ungrooved portion between the grooves.

The grooved portion of the fuel cladding tube after machining was coated with zirconium oxide by plasma spraying, and the grooved portion was filled with zirconium oxide (3). The filled zirconium oxide was coated to a depth slightly larger than the depth of the groove (Fig. 1(b)).Then, the outer surface of the zirconium oxide laminate was polished to a diameter of 1.2 mm, the same as the ungrooved portion. It was completed to a length of 41 m (Figure 1 (C)).

The surface roughness of the zirconium oxide layer after polishing is 0.5 μm and has a smooth surface.

Further, the thickness of each zirconium oxide layer varied within a range of approximately ±2 μ in the axial direction and circumferential direction of the tube.

Thus obtained. Install the oxide layer thickness measurement device in the solvent storage pool using a standard sample.

A calibration curve with good reproducibility could be obtained by several calibrations. To obtain a calibration curve, input the calibration voltage into the probe of the oxide layer thickness measuring device, press the probe against the standard sample, and scan in the axial direction of the tube to obtain the output voltage corresponding to the thickness of the oxide layer. A calibration curve is determined by subtracting the output voltage of the part where no oxide layer is formed. A good linear relationship was established between the zirconium oxide thickness and the output voltage. Furthermore, the zirconium oxide layer did not deform or wear out due to contact with the probe or friction.

Furthermore, it was found that even in a long-term fuel storage pool, no corrosion occurred and it could be used as a standard sample for a long period of time.

In addition to the shape shown in Figure 1, there are also grooves (in which the oxide layer (3) is formed without adding 2+ (Figure 2 (a)),
Oxide/3 (2) Continuous (Fig. 2 (b)
), and a groove (2j) is formed, and the oxide layer (3) has the same thickness inside and outside the groove (Fig. 2 (C)).
Various configurations are possible.

However, due to ease of manufacturing and calibration, the first
The configurations shown in FIG. 2(e) and FIG. 2(c) are considered suitable.

In particular, by adopting a configuration in which each oxide layer is separated, the output voltage r of the part where no oxide layer is formed during scanning
This is a particularly preferred configuration for unattended measurements, since calibration can be performed while checking.

[Brief explanation of drawings]

1 and 2 are schematic cross-sectional views of a fuel cladding tube. 1...Fuel cladding tube 2...Groove 3...Oxide layer, zirconium oxide Agent: Patent Attorney Noriyuki Chika Same Bamboo Flower Kikuo (α) (b) (C) Figure 1

Claims (2)

[Claims] (1) A standard sample for measuring the oxide layer thickness of a zirconium-based alloy member, characterized in that an insulating oxide layer of a predetermined thickness is provided on the surface of the zirconium-based alloy. (2) The standard sample for measuring the oxide layer thickness of a zirconium-based alloy member according to claim 1, wherein a plurality of the insulating oxide layers are provided with different thicknesses. The standard sample for measuring the thickness of an oxide layer of a zirconium-based alloy member according to claim 1, wherein the insulating oxide layer is a sprayed film of ceramic particles.