JPS5840720B2 - Cloud transfer method and device in nuclear power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention was made as part of radiation exposure countermeasures when performing periodic inspection work or improvement work on an atomic couplant that is in use.

Horizontal parts of various piping that connect directly or indirectly to the reactor pressure vessel in a nuclear couplant, valves installed in the piping, safe end nozzles to which recirculation system piping is connected, and thermal sleeves fitted in the nozzles. In places where the flow of coolant is slow, such as the cavity between
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Because an extremely radioactive substance called O8IT (abbreviation for O8IT) accumulates, workers must be placed in an extremely dangerous work environment under high radiation when repair or maintenance work is carried out near the cloud accumulation site. It will be destroyed.

Therefore, measures must be taken to reduce radiation exposure from the cloud prior to periodic inspection work or improvement work.

Therefore, as shown in Figure 1, when performing periodic inspections of the welded parts of the safe end nozzle b that protrudes from the reactor wall of the reactor pressure vessel a, it is recommended to By fitting the shield d and completely sealing the opening of the biological shield e using the pack f containing lead particles, the safe end nozzle b and the thermal
It is thought that the cloud deposited in the cavity g between J and Fc will reduce radiation exposure at the work site.

Incidentally, in the case of an atomic couplant, it is difficult to cut it more than necessary, and therefore it is impossible to move the cloud by external pneumatic supply or mechanical force.

However, as described above, in the method of attaching lead or other shielding materials to the outside of the structure near the cloud deposition site, (a) the radiation dose of the constructor engaged in the shielding construction is too high;

(b) Since heavy objects are handled, the danger rate is high and the number of man-hours required for handling them is also large.

(／→ In the case of installing a shield, the construction period must be significantly increased, which is especially difficult under a tight schedule.

2) Reduction costs including installation and removal costs are high.

(The wing shape is fixed, so it is difficult to use it for other purposes, and it also causes problems in the management and storage space of the shield after construction.

(F) In order to suppress the radiation dose, a considerable thickness of lead is installed, which reduces the work space and hinders work.

There are many problems that need to be solved.

The method and device for transferring clouds in an atomic couplant according to the present invention have been made to solve the above problems, and are capable of transferring clouds accumulated in piping sections connected to a reactor pressure vessel by movement of an alternating magnetic field. It is characterized by:

The present invention is based on the analysis of radioactive materials (cloud) generated within the reactor pressure vessel and attached equipment. is generally 50-70
% of magnetic particles (gamma hematite and magnetite).

In particular, the cloud deposited in the thermal sleeve cavity in the safe end nozzle installed in the reactor pressure vessel contains approximately 272% Fe3O4, a ferromagnetic material, and F, a weakly magnetic material.
It contained approximately 685% e2O3.

Embodiments of the present invention will be described below with reference to the drawings.

The essential feature of the present invention is to move the cloud by magnetic force, and it can be implemented in various ways, but first, an example using a traveling magnetic field exciter based on alternating current will be described.

FIG. 2 is a longitudinal cross-sectional view of a safe end nozzle that constitutes the connection between the piping of the recirculation system and the reactor pressure vessel.

A safe end nozzle 2 is provided protruding from the reactor wall of the reactor pressure vessel 1, and inside the safe end nozzle 2, thermal stress generated in the safe end nozzle 2 due to the temperature difference between reactor water and cooling water is absorbed. A thermal sleeve 3 is fitted for relaxation.

A traveling magnetic field exciter body 4 based on alternating current is inserted into the thermal sleeve 3 .

Then, by disposing the power supply device 5 of the exciter main body 4 at a certain distance from the reactor pressure vessel 1 and connecting the exciter main body 4 and the power supply device 5 with a cord 6, the power supply device 5 is placed inside the thermal sleeve 3. To form a flat traveling magnetic field based on three-phase alternating current used in linear motors, etc.

The excitation effective range 7 of the exciter main body 4 is connected to the thermal sleeve 3.
1 in the power supply device 5 after adjusting the expected distribution position of the cloud 9 deposited in the cavity 8 between the safe end nozzle 2 and the safe end nozzle 2.
Check the phase of the next power supply (AC200V 3φ) with the connected phase rotation meter, then set the voltage adjustment scale to zero, and then turn on the no-fuse breaker (NFB).
Then, operate the voltage regulator to set a predetermined current to the exciter main body 4.
The exciter main body 4 continues to be energized without moving at all.

The energization time and current value are based on the cavity 8 of the thermal sleeve 3.
It is arbitrarily determined depending on the amount, shape, and state of attachment of the cloud 9 within.

When connecting the primary side of the power supply, care must be taken to match the three phases so that the direction of magnetic field movement is aligned with the direction of cloud movement (indicated by 10 in FIG. 3).

If the opposite occurs, the cloud 9 will move in the opposite direction, and the atmospheric dose at the work site will become significantly higher, resulting in an opposite effect.

However, as shown in Fig. 3, the traveling magnetic field caused by alternating current moves sequentially in the traveling direction, but unlike the direct current magnetic field, it can easily cause a traveling magnetic field in a magnetic body, and it can also be used for stationary objects (CRUD). It can give a shock to the particles, making it easier to move, so it can also encourage the movement of α-hematite, a non-magnetic substance in Cloud 9, and it also causes the movement of weakly acidic particles and magnetic particles such as γ-hematite and magnetite. As a result, about 70 to 80% or more of the cloud moves in the traveling direction 10.

Figure 4.5.6 shows an example of transferring clouds deposited on the horizontal pipes of the primary and secondary systems of a nuclear couplant. The traveling magnetic field exciter main body 12 is divided into several parts in the axial direction (three parts in the figure) to reduce the weight of each part, and each of the divided exciter main bodies 12a, 12b, 1
2C are connected by connecting wires 13 with the same phase, and each exciter main body 12a, 12b, 12C is also divided into several parts in the circumferential direction (
In the figure, the pipe 11 is divided into three parts, each of which surrounds the pipe 11, and each of the divided parts is connected by a ferry 14.

Then, a three-phase current having a predetermined phase is supplied from the power supply to each exciter main body 12a, 12b, 12C, and the cloud 9 deposited in the pipe 11 is moved as the magnetic field advances.

In FIG. 4, 17 is a biological shield, 18 is a jet pump tiff user, and 19 is a reactor core.

Fig. 7 shows an example in which the iron core 16 around which the coil 15 is wound is arranged in a spiral shape to make the cloud advance more smoothly. It can also be applied in the case of

Above we have shown an example of a flat plate-like traveling magnetic field based on three-phase alternating current, which is used in linear motors etc. as a method of magnetically transporting clouds. It is also possible to transport the cloud by moving the magnetic field by mechanically moving the cloud.

It should be noted that peeling and movement of the cloud is easiest when carried out when the cloud is immersed in water, followed by cases where it is carried out in a sludge state and cases where it is carried out in a dry state.

In addition, when the cloud is immersed in water, ultrasonic waves are used, and when the cloud is not immersed in water, mechanical vibration is used.
It is also possible to further facilitate detachment and movement of the cloud.

According to the cloud transfer method and device for an atomic couplant of the present invention: [) A wide working space can be obtained.

11) Construction is easy and the radiation exposure of the construction worker is low.

111) Low work cost (reduced work).

1v) Storage space after construction can be reduced.

(2) The radiation exposure reduction effect is reliable and significant.

(1) Since it advances an alternating magnetic field, even weakly magnetic substances can be easily transported, making it ideal for transporting clouds.

It can produce excellent effects such as

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a conventional radiation exposure reduction method, and Fig. 2 is an illustration of a cloud deposited between a safe end nozzle and a thermal sleeve in an atomic couplant of the present invention in which the cloud deposited between the safe end nozzle and the thermal sleeve is transported by a traveling magnetic field generated by alternating current. An explanatory diagram of the transfer method and device, Fig. 3 is an explanatory diagram of the progress of the magnetic field in the embodiment shown in Fig. 2, and Fig. 4 is an explanatory diagram of the progress of the magnetic field in the embodiment shown in Fig. 2. FIG. 5 is an explanatory diagram of the structure of the exciter main body used in the embodiment of FIG. 4 and the state of cloud distribution in the piping ( FIG. 6 is a view taken in the direction of the ■ arrow in FIG. 5, and FIG. 7 is an explanatory diagram when the iron core of the exciter is arranged in a spiral shape. 1...Reactor pressure vessel, 2...Safe end nozzle, 3...Thermal sleeve, 4,
12... Main body of traveling magnetic field exciter based on alternating current, 5.
...Power supply device, 9...Cloud, 10.
... Cloud's direction of travel, 11... Piping.

Claims (1)

[Scope of Claims] 1. A method for transporting clouds in an atomic couplant, which comprises transporting clouds deposited on a piping section connected to a reactor pressure vessel by the advancement of an alternating magnetic field. 2. A cloud transfer device in an atomic couplant, characterized in that an exciter configured to sequentially advance an alternating magnetic field is disposed near a cloud accumulation location such as a piping section connected to a nuclear reactor pressure vessel.