JPS60108789A - Seal ring for driving mechanism of control rod for nuclear power plant - 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 the Invention] The present invention relates to a seal ring for a nuclear power generation Zosynt control rod drive mechanism, which is made of a nickel-based alloy that does not contain cobalt and has excellent wear resistance.

[Technical background of the invention and its problems]

Generally, a control rod drive mechanism for a nuclear power plant has a support tube 4 that supports a control rod 3 inserted inside a tube body 2 that protrudes from the outside of a reactor vessel 1, as shown in FIG. A seal ring 5.6 is provided to isolate the water from the control rod drive water, and the control rod 3 is driven up and down by the supply of the control rod drive water.

To raise the control rods 3 during reactor shutdown or power control, pressurized water is supplied from the inlet lower and the check valve 8 is closed, causing the pressure water to reach the lower surface of the support cylinder 4 that supports the control rods 3. This causes the control rod 3 to rise. At this time, the seal ring 5 attached to the inner guide shaft 9 generates sliding friction with the inner wall of the support tube 4 and wears out.

On the other hand, in order to lower the control rod 3 when starting up the reactor and increasing the output, pressurized water is supplied from the inlet 10, and the pressure water acts on the lower surface of the collet piston 11 and pushes it up. The collet piston 11 compresses the spring 12 during its rising process, and when #1 is compressed to the maximum,
When the upper end surface of the collet piston 11 collides with the inclined surface of the lower surface of the cap 13, the collet piston 11 separates from the groove 14 of the support tube 4, the stopper comes off, and the control rod 3 descends under its own weight. . The seal ring 6 attached to this L collet piston 11 is connected to the outer wall of the outer guide tube 15 and the cap support tube 1.
Sliding friction occurs with the inner wall of 6.

A cobalt-based alloy called Stellite containing approximately 50 tIb of cobalt is generally used for parts such as the seal ring 5.6 that require wear resistance.

However, when seal rings made of cobalt-based alloys are used in control rod drive mechanisms of nuclear power plants,
Wear products and corrosion products from friction contain cobalt, so when this is brought into the reactor by flowing water, it is irradiated with neutrons and becomes cobalt-60, which increases the radiation dose rate of nuclear power plants. will increase.

Furthermore, if this cobalt-60 accumulates, there is a risk of increasing the amount of radiation exposure of workers during periodic inspections of nuclear power plants, which in turn will reduce the operating rate of the plant.

[Purpose of the invention]

The present invention has been developed in view of the above, and uses a bi-Kel-based alloy that does not contain cobalt as an alloying element, which has excellent wear resistance, and also suppresses the increase in radiation dose rate due to cobalt-60, allowing plant operation. The object of the present invention is to provide a seal ring for a control rod drive mechanism of a nuclear power plant, which improves efficiency.

[Summary of the invention]

The present invention contains less than or equal to carbon o, is and silicon in weight percent.
0% or less, manganese 1.0% or less, chromium 10-25%, molybdenum 2.0-10%, aluminum 0.1-1
．． 0%, titanium 0.1-1.5%, iron 2-25%, niobium 3.0-6%. o qb , the remainder being nickel and incidental impurities.

Next, the chemical composition of the wear-resistant alloy constituting the seal ring for a nuclear power plant control rod drive mechanism of the present invention and the reason for its addition will be explained.

Carbon is a necessary element to dissolve in the alloy and improve its strength, and is usually added in an amount of about 0.02 to 0.06%, but if it is added in large amounts, carbides will precipitate at grain boundaries, resulting in poor intergranular corrosion resistance. Since it damages the strength and toughness, the coefficient should be set to 0.1 or less.

Silicon is added as a deoxidizing agent during melting and is usually 0.
It is contained in an amount of about 1 to 0.6%, but addition of a large amount impairs toughness and workability, so the content should be 1.0% or less.

Manganese is added as a deoxidizing and desulfurizing agent during melting, and usually contains about 0.1 to 0.5 titanium.

However, even if a large amount is added, the effect will be small, so 1
．． 0% or less.

Chromium is an element that improves the strength and corrosion resistance of the alloy, and is preferably in the range of 10 to 25%, particularly 15 to 20%. If it is less than 10, the effect of addition will be small, and if it exceeds 25, the processability will be impaired, so the above range is specified.

Molybdenum has the effect of improving the strength and corrosion resistance of the alloy, so it is necessary to add at least two or more molybdenum. However, since a large amount of addition exceeding 10% deteriorates the wire workability, it is necessary to keep it below this value.

Aluminum is an element that forms an intermetallic compound with Kel, precipitates in the alloy, and improves the strength of the alloy. In this case, if it is less than 0.14, there is little effect, and there is also a balance with the content of titanium and niobium, but 1.0%
If added in a large amount exceeding 0.1, the processability will deteriorate.
The range is preferably from 1.0 to 1.0, particularly preferably from 0.2 to 0.
Section 7 is good.

Like aluminum, titanium is an element that improves the strength of the alloy and is added in an amount of 0.1% or more, preferably 0.2% or more. However, the addition of a large amount deteriorates workability, although there is a balance between aluminum and niobium, so the ratio was set to 1.5.

Iron is an element that improves the hot forgeability of the alloy. In this case, adding less than 2% will have little effect;
Addition of a large amount exceeding 5% deteriorates corrosion resistance, so it was kept below this range.

Niobium, like aluminum and titanium, is an effective element that forms compounds with nickel to improve the wear resistance and strength of alloys. In this case, if it is less than 3.0%, the effect will not be sufficiently obtained, and if it exceeds 6.04%, workability will be impaired like aluminum or titanium, so this range is recommended.

[Embodiments of the invention]

Examples 1 and 2 Alloys having the compositions shown in Table 1 were prepared, melted in a high frequency induction melting furnace, hot forged, and then subjected to solution treatment. Next, after performing cold working of about 20%, aging treatment was performed under the conditions shown in Table 1, and test pieces were taken from this.

With the test piece 17 thus obtained in contact with the mating material 18 as shown in FIG.
10,000 times (with a sliding width of 25 m).
Total sliding distance: 500 m) Reciprocating motion was performed in pure water. The area of the sliding friction surface of test piece 17 is 15-! As the mating material 18, a 5US304 plate was sprayed with a Cr-B-8l-Ni based =yKel base wear-resistant material to have a surface roughness of 3S.

The evaluation method was to apply a load W of 1 kg and 5 kg to the test piece 17.
When applied, the magnitude of the force P required for the mating member 18 to shift from a static state to a moving state was compared, and the amount of friction wear was compared by weight measurement before and after the test. The results of this measurement are shown in Table 2.

Comparative Examples 1 to 6 Alloys and metals having the compositions shown in Comparative Examples 1 to 6 in Table 1 were prepared, and Comparative Examples 1, 2.3 were subjected to heat treatment and cold working in the same manner as in the above examples. However, in Comparative Example 3, a test piece was taken without aging treatment after cold working.

In addition, in Comparative Example 4, after melting using a high frequency vacuum induction melting furnace,
Cast into a mold. A test piece was taken from this and subjected to surface treatment in molten borax containing vanadium at 1000°C for 5 hours to form vanadium carbide on the surface.

In Comparative Example 5, test pieces were taken from commercially available pure Mo, which was hot-forged after sintering MO powder. Furthermore, in Comparative Example 6, a test piece was taken from a commercially available T1 alloy that was arc melted, hot forged, and then heat treated under the conditions shown in Table 1.

The thus obtained test pieces were subjected to a sliding test in the same manner as in the above examples, and the force of transition from a static state to a dynamic state and the amount of frictional wear were measured, respectively, and the results are also listed in Table 2.

As is clear from Table 2, Examples 1 and 2 of the present invention
The frictional resistance during sliding friction is the same or lower than that of the cobalt-based alloy of Comparative Example 2, which is conventionally used as wear-resistant parts such as seal rings.It also has less frictional wear and excellent wear resistance. It was confirmed that Furthermore, in Comparative Example 1, in which the amounts of molybdenum and titanium added are smaller than the specifications of the present invention, the amount of frictional wear is greater than that of the conventional cobalt-based metal.

In addition, Comparative Example 3 is an iron alloy containing approximately 80% manganese, which is said to have excellent wear resistance, Comparative Example 4 is a material with vanadium carbide formed on the surface, and wear resistance of various mechanical parts. Comparative example 5 used as an overlay on improvement
Compared to Comparative Example 6 of titanium alloy, Examples 1 and 2 have lower frictional resistance during sliding friction, less frictional wear, and excellent wear resistance.

Further, using the nickel-based alloy of Example 1 and the cobalt-based alloy of Comparative Example 2, which has been conventionally used as wear-resistant parts, the outer diameter was 83.37 m.

A seal ring with an inner diameter of 79.39 tm and a width of 2.36 fins was prepared. This was incorporated into a full-scale control rod drive test equipment as shown in Figure 1, and accelerated tests equivalent to 5 years of operation were conducted, including accumulator scram, vessel scram, dry twin, drive out, diversion gain, and diversion guard. ′
Ivy.

As a result, the friction wear of the seal ring of the present invention is 0.
0111 or less, which was significantly lower than the friction loss of the cobalt-based alloy seal ring, which was 0.04.9, and was confirmed to have excellent wear resistance.

〔Effect of the invention〕

As explained below, according to the seal ring for a nuclear power plant control rod drive mechanism according to the present invention, by defining the composition range of the nickel-based alloy constituting the seal ring, it is possible to start up a nuclear power plant.

Frictional resistance and frictional wear of the seal ring due to stoppage, increase and decrease of output are small, and the control rod can be driven stably for a long period of time.Furthermore, since it does not contain cobalt, the radiation dose rate increases due to cobalt-60. is suppressed, and
This has remarkable effects such as improving the operating rate of the 7″ runt.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a control rod drive mechanism of a nuclear power plant, and FIG. 2 is an explanatory diagram showing a sliding friction test method. 1... Reactor vessel, 2... Cylindrical body, 3... Control rod,
4... Support tube, 5, 6... Seal ring, 7.10
...Inlet, 9...Inner guide shaft, 11...Collet piston, 12...Spring, I7...Test piece, 18...
・Counter material.

Claims (1)

[Claims] Weight/average cents: carbon 0.1% or less, silicon 1.0% or less, manganese 1.04% or less, chromium 10-25%, molybdenum 2.0-10%, aluminum 0.1-1.0% 0.1 to 1.5 parts of titanium, 2 to 25 parts of iron, 3 parts of niobium.
A seal ring for a control rod drive mechanism of a nuclear power plant, characterized in that it is made of a wear-resistant alloy consisting of 0 to 6.0'l, the balance being nickel and incidental impurities.