JPS60237400A - Decontamination method - 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 The present invention relates to a method for decontaminating tools, equipment parts, etc. used in nuclear power plants, for example, whose surfaces are contaminated with radioactive substances.

Traditionally, decontamination methods involve applying beads of plastic or iron particles to surfaces contaminated with radioactive materials.

A method is provided in which a fluid such as water or air is injected together with an abrasive material such as glass particles, and radioactive materials are removed from the surface by the fluid injection pressure and the abrasive effect of the abrasive material.

However, according to this method, it is difficult to clean both the fluid and the abrasive material after use, and many problems arise in their disposal.

The present invention aims to solve the above conventional problems and easily clean both the fluid and abrasive material used for decontamination, and its main feature is to use Freon as the fluid.

The invention will be explained in detail below.

The freon used in the present invention refers to fluorochloro substituted products of hydrogen ash, and a typical example is freon-
22 (C field'llF2: 8 points -160°C1 boiling point -40
．． 8℃), freon-12 (Cα2F2: melting point -158
°C9 boiling point -29,8 °C), Freon-113(C(
ml! 2F-C (17F2: melting point -35°C, boiling point 47.
6°C), and it is desirable to use Freon=113, which has a high boiling point.

The abrasives used in the present invention include metal particles such as iron, stainless steel V Snuchy μ, aluminum, alumina, V-rica,
There are ceramic particles such as zirconia, glass particles, hard abrasives such as 7e recon force-bide particles, sand, plastic particles such as polymethyl methacrylate and polystyrene, and soft abrasives such as wood particles such as wood particles 9 seed shells. In particular, the above-mentioned soft abrasive material is resistant to pulverization even when it hits the surface to be treated, and can be reused.Therefore, it does not generate fine powder that may be scattered around and contaminate the surrounding area, and it can also be incinerated after use. However, if it is too soft, the polishing effect on the surface to be treated will be reduced.

In view of these balances, among the soft abrasives, black walnut shell pieces, especially walnut shell pieces, are preferable. The above abrasive material has a diameter of about 0.4 to 3. Generally, it is made into small pieces (particles) of about 100 ml.

Examples of the present invention are described below.

In Fig. 1, (1) is a processing chamber connected to an abrasive material P storage tank (2), an abrasive material supply path (3) having a valve (3) A, and a Freon F storage tank (4) E. Contact valve (
4) A, (4) B and! An injection nozzle (5) connected to a sulfurion supply channel (4) with a pressure port/7" (4) 0.bony" (4) D is inserted, and the workpiece has a surface contaminated with radioactive substances. The radioactive substance is removed from the surface by the injection pressure and polishing effect of Freon F and abrasive P that are injected from the injection nozzle (5) in the processing chamber (1). The injection pressure at this time can be set broadly from about 5o to 150 #/d, and the amount of abrasive depends on the injection pressure, but it is about 5o to 300g per Freon 11 (in the case of walnut shell). .

The used Freon is vaporized by an infrared heater (6) installed in the processing chamber (1), and then heated to a blower (7).
is removed from the processing chamber (1) by
) The condensed Freon is returned to the storage tank (4)E via the reflux path Q1 through which the pulp αOA exists. Furthermore, the remaining freons that are not condensed in the condenser (9) are returned to the processing chamber (
1) and collected by the demister (11) A merges with the freon in the reflux path α1 via the merging path (2) where the pulp (12A) is interposed. On the other hand, the abrasive after use The Freon that has not been vaporized in the processing chamber (1) flows down to the separation tank 0 fathom via the flow path a3 interposed by the valve (L3A), and is separated into the abrasive P and the Freon F in the separation tank 04. When the abrasive material P is a walnut shell, the difference in specific gravity between the abrasive material P and Freon F is large, and the abrasive material P and Freon F clearly float and separate.

The separated abrasive P is taken out from the separation tank 04 by the slurry pump α0 and returned to the abrasive P storage tank (2) via the return path OQ. Stockpile f! In (2), the remaining Freon F is further separated and the return path Qη is interposed with pulp 0ηA.
is returned to the separation tank α◆. A level gauge (2) A is inserted in the storage tank (2), and the level gauge (2) A detects the surface position of the abrasive material P, and the slurry pump a
9 is controlled by the detected value to adjust the amount of abrasive P returned from the separation tanks α. Freon F separated in the separation tank α- connects through the filter θ to the take-out path α interposed with the valve Q'JA and the bottom of the separation tank a4, and then connects to the take-out path (1) interposed with the valve (1)A. Pump (via
b) If the degree of contamination is low, pulp UA
is stored in the furnace liquid tank (e) from the furnace liquid path (a) where
The pulp (c) merges with the freon in the freon supply path (4) via the merging path (c) in which A is interposed.

On the other hand, if the degree of Freon contamination increases, valve (A)
It is led to the distiller (c) through the regeneration path (a) with an intervening
It condenses through the regeneration path (b) intervening in the storage tank (c).
4) Returned to E, the distillation residue is taken out to the residue tank (to) from the discharge passageway interposed by the valve IMA. In addition, the storage tank (
4)E.

There are level gauges (4) in the furnace liquid tank (c) and distiller (7), respectively.
1)E.

Four A and (c) A are inserted to detect the Freon liquid level and control the amount of Freon F to be taken out and taken in.

Instead of the above embodiment, the processing chamber c11) may be as shown in FIG. In Fig. 2, an injection nozzle /l/(to) is suspended from the upper wall of the processing chamber G1), and
A sea fi7 made of flexible material such as rubber is installed on the horizontal inlet and outlet sides of the roll conveyor (
B) and 04, the long articles to be treated such as pipes and electric cables are continuously carried in and out in the direction of the arrows and processed by the injection nozzle lv (g). Furthermore, processing room (41)
may be made movable as shown in FIG. In FIG. 3, the processing chamber (41) has an opening (42) at the bottom, and the opening (
42) is brought into contact with the surface of the workpiece 1, and the injection nozzle /l/ (
45), the processing chamber (41) is moved while processing. At this time, the discharge path (48) and the Freon supply path (44)
.

The abrasive supply path (43) and the like are naturally made flexible.

Note that the method for separating and recovering the freon and walnut pieces is not limited to the embodiment shown in the first period above, and various methods can be adopted.

As mentioned above, in the present invention, Freon is used as a fluid, so in addition to the inherent cleaning properties of Freon as a solvent, it is easy to vaporize without fear of ignition, so separation and purification from abrasive materials can be carried out extremely efficiently. Since radioactive materials are added, radioactive substances are removed not only by the ejection pressure of the flexible material, but also by the abrasive effect of the abrasive material, greatly improving decontamination efficiency.In addition, soft materials, especially walnut shells, can be used as the abrasive material. In this case, it is difficult to break and maintains its original shape even when it collides with the surface to be treated, so it can be reused, and the difference in specific gravity between Freon and walnut shells allows efficient flotation and separation.

[Brief explanation of drawings]

FIG. 1 is a system diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram of a processing chamber of another embodiment, and FIG. 3 is an explanatory diagram of a processing chamber of still another embodiment. In the figure, (2)... Abrasive material storage tank, (3)... Abrasive material supply path, (4)... Freon supply path, (4) E
... Freon equipment 11 tanks, (5) ... Injection nozzle, F ... Freon, P ... Abrasive material patent applicant Daido Steel Co., Ltd. I 2 Senga 3 Senga procedure amendment 1. Indication of the case Patent Application No. 251671 filed in 1982 2. Name of the invention Decontamination method 3. Person making the amendment Relationship with the case Patent applicant address Aza Kazudashi, Hoshizaki-cho, Minami-ku, Nagoya City Address 66 name (371
) Daido Steel Co., Ltd. Representative Director Autumn 1) Masaya, 41 Agent 467 Address 32-6 Tsukimigaoka, Yatomi-cho, Mizuho-ku, Nagoya Number of inventions increased by 7 due to amendment, subject of amendment Specification "Name of invention" The column “Method” has been corrected.

Claims (3)

[Claims] (1) A decontamination method characterized by spraying Freon together with an abrasive onto a surface contaminated with radioactive substances (2) “Claim (1)” that the abrasive is soft
Decontamination method described in (3) The soft abrasive is a small piece of walnut shell.
Claim (2) Decontamination method described in JK