JPS5946597A - Atomic power plant pipeline system - 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 [Field of Application of the Invention] The present invention relates to a piping system for a nuclear couplant, and in particular to a piping system for a nuclear reactor, which is a system for adjusting the flow rate of coolant supplied to the reactor core in a boiling water reactor. This relates to a circulation piping system (hereinafter referred to as recirculation piping).

[Background of the invention]

A recirculation system piping according to the prior art is shown in FIG.

1 indicates the reactor pressure vessel. Below, reactor pressure vessel 1
The recirculation system piping installed in the system has the following configuration. Straight pipe 2, elbow 3, tee 4, inlet valve 5, elbow 6, pump 7 for forced circulation of water in reactor pressure vessel 1, motor 8 for driving pump 7, outlet valve 9, other systems The piping component components of the nozzle stub 10 for connection with the pipe, the cross 11, the header bent pipe 12, the reducer 13, the straight pipe 14, the elbow 15, and the nozzle stub 16 are butt welded into the shape shown in Fig. 1. It is assembled and configured.

The structure of the main piping members shown above will be explained below.

Figure 2 shows tee 4. For tees used not only for recirculation system piping but also for piping in general, the M and C dimensions in Figure 2 are determined by standards such as JIS and ANSI (American standards), and commercially available tees are manufactured according to these standards. There is.

FIG. 3 shows details of the butt weld between the elbow 3 and the pipe 2. In FIG. 3, 40 indicates a welded portion between the pipe 2 and the elbow 3, and 41 indicates an ultrasonic probe.

1 in Figure 3. ．． The dimensions indicated by 12 are for welding pipe 2.
and shows the range in which the inner surface of the end portion of the tee 4 is mechanically cut.

Aside from general industrial piping, piping systems that require a high degree of safety and reliability, such as those for nuclear power plants, require regular maintenance not only during construction, but also over a long period of time during use. It is required to inspect welded parts using ultrasonic flaw detection or the like to confirm their soundness.

Conventional recirculation system piping consisting of such piping members is
Ultrasonic flaw detection of welded parts during maintenance inspections is difficult, and inspection work takes a long time. Maintenance and inspection of the nuclear couplant piping system, such as the recirculation system piping, is carried out after the reactor is shut down. A liquid containing radioactive substances exists within the piping of the atomic couplant. In particular, since both ends of the recirculation system piping are connected to the reactor pressure vessel 1, which houses the reactor core where many fuel assemblies are loaded, cold reactor water containing multi-needle radioactive materials flows into the recirculation system piping. exists in Therefore, the more difficult it is to perform the above-mentioned ultrasonic flaw detection of the welded portion, the greater the risk of radiation exposure to workers. Furthermore, maintenance and inspection work in a radioactive atmosphere requires replacement of workers, which is extremely difficult.

[Purpose of the invention]

The object of the present invention has been made based on the above-mentioned drawbacks of the prior art, and it is an object of the present invention to reduce the possibility of stress corrosion cracking occurring in the recirculation system piping installed in the reactor pressure vessel, thereby increasing the reliability of the nuclear couplant. The aim is to improve sexuality.

[Summary of the invention]

A feature of the present invention is that in a recirculation system piping installed in a reactor pressure vessel, a straight pipe member with a tee is integrally formed with a tee part and a straight pipe part, and a blood vessel member is integrally formed with a bent pipe member with a tee. and integrally forming straight pipe parts to be joined to other piping members at both ends and branch parts of the bent pipe member with a tee,
The straight pipe section is attached by welding to one end of a straight pipe section formed on another piping member.

[Embodiments of the invention]

To inspect the welded part 40 shown in FIG. 3 and its vicinity,
In order to perform one-movement flaw detection with the ultrasonic probe 41, a smooth surface is required over a certain range.

This range is indicated by Ll and L2 in FIG. At the same time welding part 4
The inner surface of the 0 is also required to be machined to be smooth over a certain range so that the ultrasonic waves are uniformly reflected. This range is shown in FIG. 3 as 71 + t2.

Originally, in order to perform ultrasonic flaw detection sufficiently, Ll *L2
For 11*72, approximately 5 times the plate thickness T is required, and for 11*72, approximately 3 times the thickness T is required. However, in the case of tee 4, as shown in Figure 2, the dimensions are determined by the standard so that the end of the bending radius is the welded part, so the lengths of Ll and 2+ are not the same as the above dimensions. Therefore, when performing ultrasonic flaw detection as an in-service inspection (hereinafter referred to as ISI), the flaw detection range is limited and sufficient flaw detection cannot be performed.

A preferred embodiment based on such considerations is as follows:
It is shown in FIG. 4, and its details will be explained below.

FIG. 4 shows a recirculation system piping according to a preferred embodiment of the present invention. Components that are the same as those of the conventional example are indicated by the same reference numerals. The recirculation system piping includes bent pipe members 20, 24, 36, and 37, each having a straight pipe section at the end of the bent part, and straight pipe parts provided at both ends of the bent part, and further connecting this straight pipe part to other systems. A bent pipe member 21 with a tee integrally provided with a branch for connection, an inlet valve 5, a pump 7, a motor 8, a straight pipe 2, an outlet valve 9, a straight pipe with a tee provided with a branch for connection to other systems. It is composed of a pipe member 22, a cross pipe member 23 with a reducer integrally provided with a reducer, and a nozzle holder 25 provided with a straight pipe part, and each pipe member is butt welded as shown in Fig. 4. It can be assembled into a shape.

FIG. 5 is an enlarged view of the straight pipe member 22 with a tee. The straight pipe member 22 with a tee includes a tee part 28 and a straight pipe part 29A.
, 29B and 29C.

Tee part 28, straight pipe part 29 A, 29 B Oyohi 29
c, it is constructed in one piece. The straight pipe portions 29A, 29B, and 29C are formed by extending the tee portion 28, as shown in FIG. The straight pipe portion 29C becomes the branch portion described above. The branches may be removed diagonally. Length t5 of each straight pipe part
+ t6 and t7 must be at least 5 times the wall thickness of the straight pipe section. If this is satisfied, the lengths of the straight pipe portions 29A, 29B, and 29C can be adjusted as necessary.

An enlarged view of the bent pipe member 21 with a tee is shown in FIG.

The bent pipe member 21 with a tee is an integral structure of the bent pipe member 20 and the straight pipe member 22 with a tee. That is, the structure is such that the straight pipe part 27A of the bent pipe member 20 and the straight pipe part 29A of the straight pipe member 22 with tees are shared, and the branch part 28 and the bent pipe part 29 are present, and the branch part 28 and the bent pipe part There are straight pipe portions 30A and 30B which are extensions of a portion of 29. The branch portion 28 is a straight pipe portion, and corresponds to the straight pipe portion 29C in FIG.

In FIG. 4, the straight pipe section of the bent pipe member 20 is butt-welded to a nozzle section (not shown) of the reactor pressure vessel 1. Naturally, a straight pipe portion is also formed in this nozzle portion. The straight pipe part of the bent pipe member 20 and the straight pipe part 30A of the bent pipe member 21 with a tee are butt welded.

The pulp 5 is butt-welded to the straight pipe portion 30B of the bent pipe member 21 with a tee. One straight pipe part of the bent pipe member 36 is welded to the pulp 5, and the other straight pipe part is welded to the pump 7, respectively. Both ends of the straight pipe 2 are butt welded to the pump 7 and pulp 9, respectively.

One straight pipe part of the bent pipe member 37 is butt welded to the pulp 9, and the other straight pipe part is butt welded to the straight pipe part 29A of the straight pipe member 22 with a tee. The straight pipe portion 29B of the straight pipe member 22 with a tee and the straight pipe portion of the piping member 23 are butt welded.

The header bent pipes 12 are butt-welded to the straight pipe portions of the piping member 23, respectively.

One straight pipe portion of one bent pipe member 24 is butt-welded to the straight pipe portion 33E of the piping member 23. The nozzle stub 25 is butt-welded to a plurality of openings provided in the header curved pipe 12. One straight pipe part of the bent pipe member 24 is butt-welded to the straight pipe part 35 of the nozzle stub 25 .

The other straight pipe portion of each bent pipe member 24 is welded to a nozzle portion (not shown) of the reactor pressure vessel 1.

Although not shown in the figure, the bent pipe member 24 is connected to an ejection nozzle located at the top of the jet pump. The welding between each piping member mentioned above is
Since the straight pipe parts are butt welded together, ultrasonic flaw detection can be performed extremely easily. This allows the probe 41 to touch and move easily in the vicinity of the welded portion, making it possible to perform flaw detection over a sufficient range.

The straight pipe portion of the nozzle stub 25 and the straight pipe portion of the piping member 23 are joined to the bent pipe member 24 in an area consisting of the bent pipe members 36, 37, the straight pipe member 22 with a tee, the piping member 23, and the header bent pipe 12. This was done after conducting a pressure test. The pressure test in the above-mentioned area was conducted because the pressure in this area due to the discharge pressure of the pump 7 is higher than the pressure in the reactor pressure vessel 1 and the pressure in the suction side piping of the pump 7. This will be done separately. This pressure test is performed by welding blind lids to the end faces of the straight pipe portion of the nozzle stub 25 and the straight pipe portion of the piping member 23 to seal the ends of the straight pipe portions, and further closing the pulp 5. After the pressure test, the blind cover attached to the nozzle stub 25 and the piping member 23 is removed, and one straight pipe (9) of the bent pipe member 24 is attached to that part as described above. By attaching the curved pipe member 24 last, it is possible to absorb errors caused by joining of each piping member.

During operation of a boiling water reactor, cooling water within the reactor pressure vessel 1 flows through the recirculation system piping. That is, the pump 7 is driven, and the cooling water in the reactor pressure vessel 1 is supplied to the bent pipe member 20, the bent pipe member with tee 21, the pulp 5, and the bent pipe member 3.
6, the piping member 2 passes through the pump 7, the straight pipe 2, the pulp 9, the bent pipe member 37, and the straight pipe member 22 with a tee in order.
It flows into 3. The flow path of the cooling water is divided by the piping member 23, and a part of the cooling water flows directly from the piping member 23.
The liquid is ejected through the entire curved pipe member 24 into the jet pump inside the reactor pressure vessel 1. The remaining cooling water, which is the majority, is discharged from the piping member 23 into the jet pump via the header bent pipe 12, the nozzle stub 25, and the bent pipe member 24.

ISI will be carried out after the boiling water reactor is shut down, but
As described above, the areas around the welded portions of the recirculation system piping in this embodiment are all straight pipe portions having a simple shape (10), making ultrasonic flaw detection extremely easy.

ISI inspection time is also significantly reduced. therefore,
The risk of radiation exposure for workers conducting inspections is significantly reduced, while at the same time improving the operating efficiency of the reactor. In particular, by simplifying the shape of the welded part, it becomes possible to use an automatic ultrasonic flaw detection device, and ultrasonic flaw detection can be performed remotely and automatically. This will significantly contribute to eliminating radiation exposure for workers.

Particularly in this embodiment, since a teeed bent pipe member is used, in which the teeed straight pipe member and the bent pipe member are completely integrated, it is possible to reduce the number of welding points in the piping system. This is I
The number of locations subject to SI can be reduced, the time required for ISI can be reduced, and at the same time, the areas where stress corrosion cracking may occur can be reduced, and the reliability of the atomic couplant can be significantly improved.

〔Effect of the invention〕

As explained above, the present invention uses a bent pipe member with a tee that is an integrated straight pipe member with a tee and a bent pipe member (11), so the number of welded parts in the piping system can be reduced. As a result, the possibility of stress corrosion cracking occurring in the piping can be reduced, which has the effect of significantly improving the reliability of the atomic couplant.

[Brief explanation of the drawing]

Figure 1 is a structural diagram of the conventional recirculation system piping for a boiling water reactor, Figure 2 is a structural diagram of the tee shown in Figure 1, and Figure 3 is the state of ultrasonic flaw detection near the elbow weld. An explanatory diagram showing
Fig. 4 is a structural diagram of a recirculation system piping according to a preferred embodiment of the present invention, Fig. 5 is a structural diagram of a straight pipe member with a tee shown in Fig. 4, and Fig. 6 is a structural diagram of a straight pipe member with a tee shown in Fig. 4. It is a structural diagram of a bent pipe member. 1... Reactor pressure vessel, 7... Pump, 12...
Header bent pipe, 20, 24, 36.37... bent pipe member,
21... Bent pipe member with tee, 22... Straight pipe member with tee, 25... Nozzle stand, 28... Part of tee (branch),
29... Bent pipe section, 29A, 29B, 29C, 30A,
30B... Straight pipe section. Agent Patent Attorney Akio Takahashi (12) Ji4 Kasumi-589-? 7

Claims (1)

[Claims] 1. In the recirculation system piping installed in the reactor pressure vessel, a straight pipe member with a tee is integrally formed with a part of the tee and a straight pipe part, and a blood vessel member is integrally formed with the straight pipe member with a tee to form a curved pipe member with a tee,
Further, a straight pipe part to be joined to another piping member is integrally formed at both ends and branch parts of the bent pipe member with a tee, and the straight pipe part is connected to one end of the straight pipe part formed on the other piping member. Atomic couplant piping system installed by welding.