JPS62228992A - Cutter for radioactive waste - 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] [Object of the Invention] (Industrial Application Field) The present invention relates to a spent nuclear 51 tube such as an in-core neutron measurement tube stored in a fuel pool of a boiling water reactor. It is related to radioactive waste cutting equipment that cuts radioactive waste.

(Prior art) Generally, in boiling water reactors, various types of instrumentation are performed for reactor management, reactor power control, maintenance, etc. Among these, nuclear instrumentation for in-reactor neutrons is The neutron flux distribution is being monitored. Reactor output control is performed by this neutron flux distribution PS82, and the neutron flux distribution state within the reactor is always maintained in an appropriate state during the operating period of the nuclear reactor.

The neutron flux distribution in the reactor core is monitored through a rod-shaped in-core neutron measurement tube (hereinafter referred to as LPPMPP type). This LPRM detector is inserted and held between fuel assemblies installed in the reactor core.

The LPPMPP type has a detector main body and a spring holder connected to the upper end of the detector main body, and the spring holder is biased upward by a spring housed in the detector main body. The upper end of the spring holder has a grid shape and is installed and held at the intersection of the upper grid plate, while the detector body is housed in an in-core housing that penetrates the bottom of the reactor pressure vessel.

The detector body of the L P P M detector is integrally assembled from the neutron detection part and the Ml cable, and the Ml cable is dehumidified and exhausted from the internal insulating material such as A1203 in a high-temperature air atmosphere. The ends are sealed with argon gas. At this time, the inside of the neutron detector is similarly evacuated and filled with argon gas, so that the inside of the LPRM detector is maintained in an airtight state.

The surface of the LPRM detector is coated with uranium-235 (U), and this U235 absorbs thermal neutrons generated in the reactor and forms fission fragments, causing the LPRM
The argon gas inside the detector is ionized.

This ionization current enters each electrode and is output as an electromagnetic signal proportional to the neutron flux.

By the way, when a nuclear reactor is operated for a long period of time, the U235 coated on the neutron detection part of the LPRM detector loaded in the reactor is depleted and the neutron flux imaging sensitivity is reduced. This decrease in detection sensitivity is compensated for and covered by periodic calibration, but when the LPRM detector becomes unusable, it is replaced with a new LPRM detector.

In this case, the used LPRM detector has a built-in neutron detection unit with high radiation ω, and there is a risk that workers handling the used LPRM detector may be exposed to radiation. For this reason, used LPRM detectors are stored underwater in fuel pools to reduce radiation exposure to workers.

Due to this relationship, the spent L generated during each periodic inspection of the nuclear reactor
PRMM detectors, each stored and stored in a fuel pool. Due to the storage of the LPPM detector in use bay, the space in the fuel pool is reduced, and the work space in the fuel boule becomes narrow every time a periodic inspection is performed, making it difficult to improve work efficiency.

(Problems to be Solved by the Invention) In conventional boiling water reactors, spent LPRMs detected during each periodic inspection are stored in the fuel pool. On the other hand, if a stored used LPPM detector is exposed above the pool water surface for cutting, the neutron detection part is highly radioactive, so the work opening There was a risk that each car would be exposed to the T/I rays.

The present invention was made in consideration of the above-mentioned circumstances, and
By simply and easily cutting long pieces of radioactive waste from PRM detector chopsticks underwater in a fuel pool,
1. Providing sufficient work space within the fuel pool to improve work efficiency, reduce waste emissions, and significantly reduce the risk of radiation exposure during work. The purpose is to provide an IJ disconnection device.

(Structure of the Invention) (Means for Solving the Problems) The radioactive waste cutting device according to the present invention includes a main body base fixed to the side wall of a fuel pool, a main body base that is movably supported by the main body base, and a radioactive waste cutting device according to the present invention. A cutter with a blade and a cutting blade holder.
g1g1 main body, a holding table with foldable steps numbered to guide long radioactive waste such as pan-nuclear instrumentation tubes on the side of the main body base, and a step numbered holding table on the side of the main body of the cut and fix the radioactive waste.
The long radioactive waste is cut into short pieces underwater in a fuel pool.

(Function) The radioactive waste VJ disconnection device according to the present invention removes long radioactive waste such as spent nuclear instrumentation pipes that are taken out from the core of a nuclear reactor, moved underwater into a fuel pool, and stored. The fuel is cut into short pieces underwater in the fuel pool.

During cutting work, the holding table attached to the main body base is expanded to support the long radioactive waste on this holding table and guide the movement of the waste material. Fix long pieces of radioactive waste,
The radioactive waste fixed to the holder was placed in the cutting machine body under water in the fuel pool! , 7J cutting blade to cut into short pieces that are easy to handle.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

1 and 2 are a front view and a plan view showing a cutting device for radioactive waste such as spent nuclear instrumentation tubes according to the present invention, and are equipped with this cutting device? FIG. 3 shows the upper structure of the reactor building 1110 of the lll1 water reactor. A reactor pressure vessel 11 is housed in a reactor containment vessel (not shown) of the reactor building 10 .

A reactor well 12 filled with water is formed above the reactor pressure vessel 11, and this reactor well 12 is connected to the fuel assembly 1.
It is connected to a fuel pool 14 containing 3 fuels.

Above the reactor well 12 and fuel boule 14, there is a fuel exchanger 1fJ for transferring the fuel assembly 13 and the reactor in-reactor (steam dryer, steam dryer, etc.) underwater. A machine 15 is provided so as to be freely movable.

On the other hand, a core shroud 16 is integrally housed inside the reactor pressure vessel 11, and this reactor core shroud 16 has an upper grid plate 17 at the top and a core support plate 18 at the bottom horizontally. As shown in FIG. 4, the core support plate 18 is provided with a fuel support fitting 20, and a set of four fuel assemblies 13 are held on this fuel support fitting 20.Fuel assemblies 13 is loaded into the reactor core 21 with its upper part supported by the grid holes of the upper grid plate 17.

Also, reactor pressure content 8! An in-core housing 23 is installed passing through the lower end plate 11a of i11, and an in-core guide tube 24 is connected to the upper part of this in-core housing 23. The in-core guide tube 24 is provided through the core support plate 18 and opens into the core support plate 18F. An in-reactor neutron measurement tube (hereinafter referred to as "L") and RM detection (hereinafter referred to as "S") 25 as a nuclear instrumentation tube is fitted into the jt1 opening 24a of the in-core guide tube 24 so as to be freely insertable and removable from above. L,
The lower end of the PRM detector 25 is connected to the in-core housing 2
3, and its upper end is installed on the cross-section of the upper grid plate 17, and is elastically held by a spring built into the detector body.

Replacement work for the LPRM detection'/S25 installed in the core of the reactor is carried out remotely under water from above the DI subreactor pressure vessel 11 via the fuel exchange line 15, and is removed from the reactor pressure vessel 11. The LPRM detector 25 is transferred underwater from the reactor well 12 into the fuel pool 14,
It is stored at a predetermined position within the fuel pool 14.

A spent nuclear instrumentation pipe cutting device 26 shown in FIG. 1 J3 and FIG. 2 is provided on the pool wall of the fuel pool 14.

The cutting device 26 is attached to the pool side wall of the fuel boule 14 ['
The cutting machine has a main body base 27 in the shape of a J-shaped plate, and a guide rail 29° 29 for guiding the vertical movement of the cutting machine main body 28 is installed in the center of the main body base 27. The cutting machine main body 28 is suspended from a winch (not shown) by a hanging lobe 30 such as a wire rope so as to be able to rise and fall.

On the other hand, the cutting machine body 28 includes a cutting blade 31 and a cutting blade receiver 32.
The L and Q shearing forces 31 are held by a fluid cylinder (not shown) so as to be able to move forward and backward toward the cutting blade receiver [no 32], and by driving the cylinders, the L and Q shearing forces 31 are
P RM detector 25 off ll7i'? It's designed to look like this.

Also, on both sides of the main body base 27 are L PRM detectors 2.
A holding table 35 with five guides parallel to one can be installed freely. The holding table 35 is held so that it can be tilted up and down between a folded storage position and an expanded deployment position,
In the storage position, the holding table 35 is fixedly stored in a folded state by the hook 36.

LPRM detection il! ! When cutting i25, the holding table 35 is expanded and set horizontally, and the guide roller 36 provided on the holding table 35 is used.
? The L PRM detector 25 is laterally guided and transferred underwater, and is held on the holding table 35 and guide rollers 36 , 37 built into the main body base 27 . The used LPRM detector 25 is fixed by holders 38 installed on both sides of the cutting machine body 28. Each fixed spent LPPM detector 25 is connected to a fuel boule 14 by a cutting blade 31.
It is cut to a predetermined length under water. disconnected LPR
The M detector 25 is provided with six removable fragment storage boxes 40 below the cutting blade receiver 32 to prevent fragments from falling at the cutting portion.

Thus, the used L PRM detector 25 is typically about 13
It has a length of about m. This LPRM detector 25 is cut into pieces of 4 m or less for transportation needs. Due to this relationship, the cutting operation of one tree of used LPRM detectors 25 is repeated several times, and all of the used [-PRM detectors 25]
The operation of returning the cutter head holding the cutting blade 31 to its original position is repeated until a short cut piece of Im or less is obtained, and the short cut piece t is stored in a storage container (not shown).

The cut pieces of the used LPRM detector stored in the storage container are lifted into the air from within the fuel boule 14 by known means (not shown), moved from the atomic bomb building to the 1-noid bunker boule, and placed in place. The processing work of the L PRM detector 25 is completed.

In the present invention, although the used flow LPPM detector is targeted for cutting, the present invention can also be applied to cutting long vibrator-shaped or rod-shaped radioactive wastes limited to this detector.

〔Effect of the invention〕

As described above, in the radioactive waste cutting device J3 according to the present invention, long radioactive waste such as spent nuclear T1 tubes is cut under water by the cutting flH1 main body in the fuel pool. Because we have made it possible to do this, long pieces of radioactive waste can be cut and processed with simple operations.
Since long pieces of radioactive waste are not stored in the fuel pool as long as they are, the space in the fuel pool can be used effectively, and sufficient work space can be secured.
It has the effect of significantly reducing the amount of radiation exposure of workers.

[Brief explanation of drawings]

FIG. 1 is a front view of an embodiment of a radioactive waste cutting device according to the present invention, FIG. 2 is a plan view of the cutting device, and FIG.
The figure shows a partial layout of the upper part of the reactor building of a boiling water reactor equipped with a radioactive waste cutting device. Figure 4 shows the interior of the reactor pressure vessel of a boiling water reactor. FIG. 3 is a partially enlarged view of the structure. 10... Reactor building, 11... Reactor pressure vessel,
12... Reactor well, 13... Fuel assembly, 14
... Fuel pool, 1G... Core shroud, 17.
... Upper grid plate, 18... Core support plate, 21... Core part, 23... In-core housing, 24... In-core guide tube, 25... Neutron h1 loading tube (radioactive 1ji
! waste), 26... cutting device, 27... main body base, 28... cutting machine main body, 29... guide rail, 3
1... Cutting blade, 32... Cutting blade holder 1, 35...
Holding table, 36.37... Guide roller, 38.
...Holder, 40...Fragment storage box.

Claims (1)

[Scope of Claims] 1. A main body base fixed to the side wall of the fuel pool, a cutting machine main body supported on the main body base so as to be able to rise and fall and having a cutting blade and a cutting blade holder, and a lateral side of the main body base. The cutting machine has a foldable holding table for guiding long radioactive waste such as spent nuclear instrumentation pipes, and a holding tool provided on the side of the cutting machine body for fixing the radioactive waste. A device for cutting radioactive waste, characterized in that the long radioactive waste is cut into short pieces underwater in a fuel pool. 2. A holding table is held on both sides of the main body base so that it can be tilted up and down between a storage position and a horizontal unfolded position, and a guide roller for guiding a long radioactive waste is mounted on the holding table. A radioactive waste cutting device according to scope 1. 3. A guide rail is installed in the center of the main body base,
The radioactive waste cutting apparatus according to claim 1, wherein the cutting machine main body is supported so as to be able to rise and fall along the guide rail. 4. The cutting machine according to claim 1, wherein holders are provided on both sides of the cutting machine main body for fixing elongated radioactive waste, and a debris storage box is detachably provided below the cutting machine main body. Radioactive waste cutting equipment.