JPS58162888A - Nuclear fuel cladding tube - 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 improvements in nuclear reactor combustion rod cladding tubes.

More specifically, the present invention relates to improvements in zirconium-based alloy (Zircaloy) cladding tubes for nuclear fuel for light water reactors.

Nuclear fuel cladding for light water reactors today is made of a zirconium-based alloy, which reduces the mechanical interaction between the cladding and nuclear fuel pellets, and also serves as a barrier for fission products that act chemically on the cladding. (so-called P
In order to prevent CI/80C), it is known to apply a thin zirconium metal liner to the inner surface of a zirconium-based alloy cladding tube. (A pipe with one liner is hereinafter referred to as a composite pipe.

call. ) In this case, the thickness of the zirconium liner is very important to achieve the above effect; if it is too thin, the intended purpose cannot be achieved, and the liner occupies too much thickness for a given total thickness. and the strength of the entire composite pipe decreases. Therefore, thickness control is extremely important in manufacturing such composite pipes. As a prerequisite for its management, the problem is measuring the thickness of the composite pipe's base and liner, that is, the liner, but there is still no non-destructive testing method that is simple, accurate, and can be carried out efficiently on an industrial scale. unknown.

In other words, the substrate and liner have similar physical properties, so known non-destructive testing methods cannot distinguish them.
cannot be determined.

The present invention is intended to eliminate these inconveniences and provides a composite cladding tube whose liner thickness can be easily measured using a non-destructive method.

According to the present invention, for storing nuclear fuel therein,
Provided is a nuclear fuel cladding tube made of a zirconium-based alloy having a liner of a zirconium metal layer on its inner surface, characterized in that the zirconium metal layer uniformly contains r@radioactive material. .

The radioactive substance referred to here is one that is uniformly mixed with zirconium metal and does not inhibit the properties of zirconium. In addition, it is required to be an r-ray source because it can measure radiation through the zirconium-based alloy cladding base, does not activate other substances, and requires a large penetrating force.

A radioactive isotope of zirconium is preferable in the sense that it does not impede the properties of the zirconium alloy. However, metals similar to this.

r-radioactive isotopes of Ti, Hf 2 can also be used. Further, Y that undergoes f decay to become Zr, and Nb that undergoes β7 decay to become Zr can also be used.

The added radioactive substance has an appropriately long half-life so that it does not decay and sew during the manufacturing of the cladding, and on the other hand, even if there is little radiation, accurate measurements can be made in a shorter time than outside the cladding, so it has a strong radioactivity. In other words, it is necessary that the half-life is appropriately short.
Those with a half-life of about several tens of days to several hundred years are preferable.

Considering the above conditions, the main usable gamma ray metals are shown in the table below.

"Zr 85d HC0,594"Zr
65.5a β-0,255,C1,7
22゜[1,754"Ti 48y EC[10784""H
f sy gc O,126
, [1188°0.412 1chi Hf 7 od
gc O,519
, CL343゜0.456 tat Hy 45 d β-α133
．． α136゜0.546 1M2Hf9x106. ／″″Q,
271""") If 91 d /-0
,500,CL950"Y 108d
ECt36. t857, 2.76Y 57.5d
The amount of the radioactive substance added to β-1,21 depends on the strength of the radioactivity, but it is generally preferable to limit it to the room temperature solid solution range.

Next, embodiments of the present invention will be specifically described with reference to the drawings.

The present invention was applied to a fuel rod cladding tube for a pressurized water reactor.

Outer diameter 105m, length 5.5m, total wall thickness 0.6 Em 2
``We manufactured a Zr-based alloy clad tube with a single liner.

The Zr Reikin alloy composition is: 8n 1.55%, Fe0.
22%.

It was CrO,09 residual Zr.

The material for U1R is made of Zr metal with 1% by weight of Zr (
Analysis: 10.97%) was added, uniformly dissolved, and formed into a cylindrical billet. It was fitted inside a separately manufactured 2 alloy base tube, and both were simultaneously rolled to form a composite tube. The thickness of the liner was 0.0621 fl+.

An actual fuel rod is loaded with nuclear fuel pellets and sealed by welding end plugs to both ends of the rod, but in this example, only the cladding tube was fabricated.

Figure @1 is a cross-sectional view of the cladding tube manufactured in this way. In this figure, on the inner surface of the Zr alloy substrate 1.

Zr metal liner 2 containing radioactive materials.

Nuclear fuel pellets 3 to be loaded (indicated by dotted lines) and voids 4 are shown.

The thickness of the liner of the cladding tube thus manufactured was measured by external radioactivity measurement.

As shown in Fig. 2, a lead carrier 12 coated with stainless steel is inserted close to the outer surface of the tube to isolate the effect of radioactivity in the liner layer on the opposite side of the measuring section. A collimator 10 was provided, and the gamma rays passing through the gap 10' were measured with a Ge(Li) semiconductor detector 11.

As the width of the collimator gap becomes smaller, the spatial resolution improves, but on the other hand, the number of measurement counts decreases. As the number of counts decreases, it becomes necessary to lengthen the measurement time in order to obtain a certain level of accuracy. Furthermore, since the entire area is divided into smaller parts, the measurement time required to inspect the entire area becomes longer.

Therefore, the width of the gap in the IJ meter is chosen to achieve an optimal combination of spatial resolution and mechanical resolution related to statistical errors that depend on the measurement time within a given measurement time. 9 In this example, a small hole with a diameter of 0.50 was used.

The thickness of the collimator is not particularly limited. In this example, 2
There were 0 parrots.

Measurements were taken of the cover pipe kept stationary under these conditions.

31020 counts per second were obtained. The standard deviation of the count is 176 counts, and the relative error is 0.6 inches. This counting rate and the separately analyzed 912. Calculating from the content of 0.97%, the thickness of one liner layer was 0.064n+, which agreed well with the measurement of 10.062i+m obtained by destructive inspection of a fixed part of the fill.

The above measurement was performed with the cladding tube stationary, but when nondestructively inspecting a large number of tubes, it is sufficient to rotate the tubes and move them in the axial direction in the arrangement shown in Figure 2, which increases inspection efficiency. In order to increase the number of detectors, it is also possible to arrange a plurality of detectors at axially separated positions or at different circumferential positions.

The above inspection method uses a smooth average 4f with relatively continuous fluctuations.
This method is effective for measuring the thickness of the liner, and it is also advantageous to detect local abnormalities such as scratches on the inner surface of the liner using the conventional ultra-hill wave flaw detection method.

The purpose of the nuclear fuel cladding tube of the present invention is to enable the measurement of the thickness of one layer of the liner to be easily carried out on an industrial scale by non-destructive inspection without impairing the characteristics of the liner, thereby improving the performance of nuclear fuel. It is highly effective for quality control and performance assurance of the liner provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a nuclear fuel jacket pipe according to the present invention for illustrating the concept of the present invention. FIG. 2 is a conceptual cross-sectional view showing the principle of measuring the thickness of the liner of a nuclear fuel cladding tube according to the present invention by radioactivity measurement. In these figures. 1: Zirconium-based alloy cladding tube body 2: Zirconium liner Patent applicant: Atomic Fuel Industry Co., Ltd. Representative Patent attorney: Masahiro Matsui (1 other person) Figure 1 Figure 2 Figure 2

Claims (1)

[Scope of Claims] t A nuclear fuel sheath tube made of a zirconium-based alloy and having a liner of a zirconium metal layer on its inner surface for storing nuclear fuel therein;
A nuclear fuel tuft characterized by uniformly containing radioactive materials. 2. The nuclear fuel cladding tube according to claim 1, wherein the γ-ray radioactive substance is a radioisotope of zirconium. 3. The nuclear fuel cladding tube according to claim 2, characterized in that the radioactive isotope of zirconium is Zr-95. 4. The nuclear fuel cladding tube according to claim 2, characterized in that the radioactive isotope of zirconium is Zr-88. 5. The nuclear fuel cladding tube according to claim 1, wherein the γ-ray radioactive substance is Ti, Hf, Y, Nb, or the like.
A nuclear fuel cladding tube characterized by being made of at least one kind selected from radioactive isotopes.