JPH0119119B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a fuel assembly with measurement lines installed in a nuclear reactor to continuously examine the behavior of core fuel, and in particular, after use, the fuel assembly and the drive unit are separated. In particular, the present invention relates to a fuel assembly with a measurement wire having a cutting mechanism for cutting the measurement cable.

When designing the core fuel assembly loaded in the fast reactor core, it is important to consider the fission products (EP) generated from the core fuel (PuO ₂ +UO ₂ ) by neutron irradiation.
It is necessary to continuously know the amount of gas, coolant flow rate, and temperature of each part of the fuel pin, but such fuel assemblies with measurement lines for measuring core fuel have not been put into practical use in Japan. The fuel assembly with measurement wires that was recently devised is loaded with a fuel assembly with measurement wires that incorporates a measurement device into the loading section of the core fuel assembly.
Each measurement of core fuel is being carried out. This fuel assembly with measurement wires consists of a fuel section that incorporates a fuel pin containing UO ₂ and PuO ₂ at the tip of the measurement cable/tube, and a drive section that moves this fuel section up and down during fuel exchange. There is. The measurement cables and tubes coming out of the fuel section pass through the neutron shielding cable penetration in the drive section and are connected to measuring instruments installed outside the reactor. Since the measuring section of this fuel assembly with a measuring line has a short life, it is necessary to replace it with a new fuel assembly with a measuring line every 2 to 3 years. However, in a fuel assembly with measurement wires, the driving part and the fuel part incorporating fissile material are integrated, so if it is handled as one unit using the above method, the cask that is stored during maintenance for radiation protection will be damaged. The thickness increases, the weight increases, and handling becomes difficult. Additionally, handling operations are restricted due to radiation dose. For this reason, a cutting mechanism is installed at the tip of the drive unit to cut the measurement cable and pipes in order to separate the device, drive unit, and fuel unit, and the measurement cable and pipes are cut during maintenance. However, since this area receives a large amount of neutron irradiation, the cutter may become dull and some measurement cables and pipes may not be able to be cut.

In the conventional cutting mechanism, the cutter part was near the tip, so the cutter lowered to the lowest end after cutting the measurement cables and pipes, and then raised the cutter to re-cut the uncut cables and pipes. If the cutter is lowered, the cutter's nipped part is below the cutter guide through hole at the lowest position, so the cut measurement cable and tubing will fly out and hit this part, making it impossible for the cutter to rise again. Furthermore, since there is no mechanism for forcibly opening the fingers, it is impossible to grasp the fuel section again, so a cutting mechanism that can reliably cut the cables and pipes in one go is required.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the above-mentioned drawbacks and to improve operational reliability by cutting the measurement cables and tubes again even when they are not cut.

The present invention will be described in detail below with reference to the drawings of one embodiment. In FIG. 1, in the lower part of the inside of the reactor vessel 1, there are a core fuel assembly, a neutron shielding body,
A reactor core structure 2 in which control rods and the like are installed is attached. A shield plug 3, which is the lid of the reactor vessel 1, is installed on top of this. The shield plug 3 is provided with a through hole, into which the drive section 4 passes, and the integrated sample section 5 is inserted into the loading section of the core fuel assembly. FIG. 2 shows a detailed diagram of this fuel assembly with measurement lines. A plurality of fuel pins 8 are provided inside the sample portion 5 of the fuel assembly with measurement lines, and the sample portion fuel 7 is installed at an arbitrary location on the fuel pins 8. Further, an end plug 9 is provided on the upper part of the fuel pin 8, and an FP gas measurement tube 10 and a neutron detector 11 are also provided on each fuel pin 8. In order to check the relationship between the coolant flow rate of the fuel pin 8 and the temperature of each part, a plurality of flowmeters 12 and temperature measurement sensors 13 are installed in the axial direction of the fuel pin 8. . The above tube 10
The measurement cable 20 also passes through the cutter guide 15 connecting the drive unit 4 and the fuel unit 5 from inside the handling head 14 on the upper part of the fuel unit 5.
It is connected by a shielded cable penetration 16 provided inside the drive unit 4, and is connected to a measuring instrument 6 provided outside the furnace. Note that a handle 18 is provided on the drive unit 4. Further, the cable penetration 16 is formed within the inner extension tube 23, and an outer extension tube 22 is further formed outside the inner extension tube 23.
is placed. The fuel section 5 includes a cutter guide 15
It is suspended from the drive part 4 by a finger 17 attached to the tip of the drive part 4. Upward and downward movements during fuel exchange are performed by a swing crane (not shown) installed inside the containment vessel. Since this vertical movement is a large stroke, a long bellows 21 is used as the pressure boundary of the reactor vessel 1.

During reactor operation, the fuel section is moved by the handling head 1 of the fuel section by a plurality of fingers 17 attached to the cutter guide 15, as shown in FIG.
4 is suspended to prevent the fingers 17 from closing on the outer surface 26 of the cutter 19. Fuel assemblies with measurement lines that have reached the end of their service life after being used for a certain period of time are
Using the handle 18 attached to the upper part of the drive unit 4, the outer extension tube 22 is lowered relative to the inner extension tube 23 that is integrated with the cutter guide 15, and the cutter 19 fixed to the tip of the outer extension tube 22 is lowered. To do this, the measurement cable 20 and the tube 10 are cut, and as shown in FIG. When closed, the drive section 4 and fuel section 5 are completely separated. Furthermore, since the gap between the cutter 19 and the cutter guide 15 is approximately 0.1 mm in terms of cutting ability, it is possible that the core wire of the measurement cable 20 will not be cut. For this purpose, a handle 18 mounted on the drive section 4 is rotated in the opposite direction to the cutting operation to raise the cutter 19. The state at this time is shown in FIG. When the fuel portion 5 is to be gripped again, the handle 18 is further rotated in the opposite direction from this state, and the tip of the finger 17 is forcibly opened by the slope 28 of the finger opening/closing slit of the cutter 19. Moreover, when cutting the fuel part again without gripping it again, the handle 18 is rotated in the cutting direction. The measurement cable 20 and the pipe 10, which could not be cut by repeating such operations many times, can be cut as many times as necessary. In addition, since the negated part 29 on the inner surface of the cutter 19 is located above the cutter guide uppermost hole 30 after cutting, the measurement cable 20 remaining inside the cutter guide 15 and the cut end 31 of the tube 10 are not caught, and the finger Since there is no hole for cable passage in the cutter guide 15 in the movable part of the opening/closing slit part, the cutter 19 does not get caught in the same way as above.
does not interfere with the vertical movement of the

Next, the effects of the above device will be described.

As shown in FIGS. 2 to 5, the shearing, delatching, and latching operations are performed by lowering the outer extension tube 22 with the handle 18 provided on the upper part of the drive unit 4, and by just this downward movement, the measuring cable 20, etc. The mechanism is such that the action of cutting the fuel part 5, the delatching action of separating the fuel part 5, and the latch action of gripping the fuel part 5 again with the fingers 17 can be performed in one action. Therefore, since the simple downward movement of the extension pipe is used as a direct shear cutting force and delatching action, if the measurement cable 20 or pipe 10 cannot be cut, the cutter can be raised again and cut as many times as necessary, and the drive The section 4 and the fuel section 5 can be separated. Furthermore, if the cable 20 and tube 16 cannot be cut after several cutting operations, the fuel part can be grasped, which improves handling reliability.

As explained above, according to the present invention, when separating the drive section and sample section, cutting of the measurement cable and tube,
Delatching and latching operations can be performed as many times as needed with one drive unit, so if the cutter is not able to cut the measurement cables due to misalignment during assembly of the drive unit, etc., the cutting operation can be performed again. Since the drive section and fuel section can be completely separated, the cutting ability is improved and the reliability of cutting is improved. In the unlikely event that it cannot be disconnected, it can be relatched and maintenance can be performed all at once, eliminating the need to worry about it falling off, increasing reliability when removing it.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the state in which the fuel assembly with measurement lines of the present invention is installed in a nuclear reactor, FIG. 2 is a cross-sectional view of the fuel assembly with measurement lines shown in FIG. FIG. 2 is a detailed view of the cutting mechanism, FIG. 4 is a diagram of the state after the measurement cable and tube are cut, and FIG. 5 is a diagram of the state immediately before the cutter is raised to perform a latching operation. 4... Drive section, 5... Fuel section, 15... Cutter guide, 17... Finger, 19... Cutter, 20...
Measurement cable, 28... slope.

Claims (1)

[Claims] 1. A sample part containing a fuel part, an inner extension tube whose upper end is held by a stiff plug and whose lower end is inserted into the sample part, and a cutter guide is formed at the lower end, and a cutter guide. A plurality of through-holes are formed through the inner and outer surfaces, a cable is inserted from the fuel part through the through-holes into the inside of the inner extension tube to the top of the flexible plug, and a cable is inserted above the through-hole of the cutter guide. a finger that is rotatably attached and can fit into the sample section when expanded; an outer extension tube provided concentrically along the outside of the inner extension tube;
A handle for driving the outer extension tube in the vertical direction relative to the inner extension tube, a cutter formed at the lower end of the outer extension tube, and a tapered portion formed on the outer surface of the cutter to expand the fingers when the cutter rises. , a large-diameter barbed portion formed on the inner surface of the cutter above the uppermost through hole position when the lowermost end of the cutter coincides with the lowermost end of the cutter guide; body.