CA2240421A1 - Process for recycling contaminated metal parts - Google Patents
Process for recycling contaminated metal parts Download PDFInfo
- Publication number
- CA2240421A1 CA2240421A1 CA 2240421 CA2240421A CA2240421A1 CA 2240421 A1 CA2240421 A1 CA 2240421A1 CA 2240421 CA2240421 CA 2240421 CA 2240421 A CA2240421 A CA 2240421A CA 2240421 A1 CA2240421 A1 CA 2240421A1
- Authority
- CA
- Canada
- Prior art keywords
- metal parts
- melt
- slag
- elements
- contaminated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
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- Processing Of Solid Wastes (AREA)
Abstract
The invention relates to a process for recycling metal parts which have been contaminated by radioactive elements, especially alpha-emitters. A melt and slag are formed from the metal parts and the slag is removed. Before the melt and slag are formed, the radioactive elements must be oxidised. To that end, the contaminated metal parts can be exposed to an oxygen-containing atmosphere at a temperature below the melting point of the metal parts.
Description
~ CA 02240421 1998-06-12 ., P~. T~ S AMENDE2 T~T TF~ANSLATION
Description Method for recycling contaminated metal parts The invention relates to a method for recycling metal parts which are contaminated by radioactive elements, in particular by ~-emitters, a melt and a slag being formed from the metal parts and the slag then being separated from the melt.
When dismantling and also when operating nuclear facilities, large amounts of contaminated, metal, in particular iron-containing, scrap is produced, which has to be recycled or disposed of. It is usual to subject this scrap to a melt decontamination. The radioactive - elements which this scrap contains are, for example, ~-emitters, such as uranium, thorium, transuranium elements and/or alkaline-earth metals.
A method which comprises a melt decontamination is known from DE 33 18 377 A1. In this method, the contaminated metal is melted, and a slagging agent is added to the melt which is formed. A slag which floats on the melt is then formed. Radioactive elements (e.g.
uranium, neptunium and plutonium), which caused the contamination of the metal parts, accum.;mulate in the slag. Thus, while the concentration of these elements in the slag increases, their concentration in the melt decreases. This is to be attributed to the fact that the solubility of the elements in question is greater in the slag than in the melt. Decontamination of the melt is thus achieved. The slag is later drawn off from the surface of the melt. Its volume is small compared to the total volume of melt and slag. Only this small volume of slag has to be taken to final storage. Consequently, only a relatively small final storage capacity is required.
The metal melt, the volume of which is significantly greater than the volume of the slag, is decontaminated and can therefore be reused. For example, shaped metal parts may be produced from decontaminated metal.
~l~h~ h ~h,~ m~ 3 ~jr~ L ~-~lc~ n1~ m; n,-1_ ~,~ 2 Although the elements which caused the contamination of the metal parts are substantially removed from the metal melt using the known melt decontamination, a further increase in the degree of decontamination is nevertheless desirable.
From FR 2 479 540 a method is known for the disposal of radioactive waste whereby parts of the waste are oxidized.
The object on which the invention is based is to provide a method for recycling radioactively contaminated metal parts which removes the elements which caused the radioactive contamination of the metal parts from the metal melt to an - even greater extent than hitherto. It is therefore intended for a greater amount (volume or mass) of the radioactive elements to be removed from the melt and introduced into the slag.
The object is achieved according to the invention in that the radioactive elements are oxidized prior to the formation of the melt and the slag, and that for the purpose of oxidizing the radioactive elements, the contaminated metal parts are held in an oxygen-containing atmosphere for a period at a temperature below the melting temperature of the metal parts.
The temperature at which the oxidation occurs, must be as high as possible, i.e. be only slightly below the melting temperature, in order that, on the one hand, no melt is yet Replacement Page formed during the oxidation and, on the other hand, oxidation which is as complete as possible is made possible ~ ~he ox~dat~on process namely proceed$ be~t at ~gher temper~ture~, Due to the fact that all the contaminated metal parts, and not ~ust the radioactive elements exclusively, are sub]ected to an oxidation process, this process is advantageously simplified.
Since the radioactlve elements adhere to the surfaces of the metal parts, complete oxidation of these elements is ensured.
The fact that a relatively small part of the metal of which the metal parts themselves consist is also oxidized in the process does not impede the subsequent melt decontamination.
The oxides of the elements then preferentially pass into the slag during the melting process.
The method according to the invention particularly brings the advantage that the radioactive elements which are to be dissolved in the slag are present as oxid-es, the solubility of which, surprisingly, is greater in the slag than the solubility of the unoxidized elements. As a result, a significantly increased proportion of the elements which caused the contamination is advantageously removed from the metal melt. The metal melt and thus also shaped metal parts, produced therefrom for example, are as a result substantially decontaminated. The shaped metal parts can then be used without limitations.
Replacement Page The oxygen-containlng atmosphere may, for example, be dry or moist air. It is then unnecessary, advantageously, to provide any special oxygen-containing atmosphere.
The period for which the metal parts are held in the oxygen-containing atmosphere at a temperature below the melting temperature of the metal parts, for the purpose of oxidation, may, for example, be 10 minutes to 60 minutes long.
Sufficiently complete oxidation of the radioactive elements is ensured in a period of this length.
- The metal parts to be decontaminated may, for example, contain iron and/or copper.
The method according to the invention brings the advantage that a significantly improved degree of decontamination of metal parts is achieved using a melt decontamination. The shaped metal parts produced from the decontaminated metal melt can then be used without restrictions.
Replacement Page
Description Method for recycling contaminated metal parts The invention relates to a method for recycling metal parts which are contaminated by radioactive elements, in particular by ~-emitters, a melt and a slag being formed from the metal parts and the slag then being separated from the melt.
When dismantling and also when operating nuclear facilities, large amounts of contaminated, metal, in particular iron-containing, scrap is produced, which has to be recycled or disposed of. It is usual to subject this scrap to a melt decontamination. The radioactive - elements which this scrap contains are, for example, ~-emitters, such as uranium, thorium, transuranium elements and/or alkaline-earth metals.
A method which comprises a melt decontamination is known from DE 33 18 377 A1. In this method, the contaminated metal is melted, and a slagging agent is added to the melt which is formed. A slag which floats on the melt is then formed. Radioactive elements (e.g.
uranium, neptunium and plutonium), which caused the contamination of the metal parts, accum.;mulate in the slag. Thus, while the concentration of these elements in the slag increases, their concentration in the melt decreases. This is to be attributed to the fact that the solubility of the elements in question is greater in the slag than in the melt. Decontamination of the melt is thus achieved. The slag is later drawn off from the surface of the melt. Its volume is small compared to the total volume of melt and slag. Only this small volume of slag has to be taken to final storage. Consequently, only a relatively small final storage capacity is required.
The metal melt, the volume of which is significantly greater than the volume of the slag, is decontaminated and can therefore be reused. For example, shaped metal parts may be produced from decontaminated metal.
~l~h~ h ~h,~ m~ 3 ~jr~ L ~-~lc~ n1~ m; n,-1_ ~,~ 2 Although the elements which caused the contamination of the metal parts are substantially removed from the metal melt using the known melt decontamination, a further increase in the degree of decontamination is nevertheless desirable.
From FR 2 479 540 a method is known for the disposal of radioactive waste whereby parts of the waste are oxidized.
The object on which the invention is based is to provide a method for recycling radioactively contaminated metal parts which removes the elements which caused the radioactive contamination of the metal parts from the metal melt to an - even greater extent than hitherto. It is therefore intended for a greater amount (volume or mass) of the radioactive elements to be removed from the melt and introduced into the slag.
The object is achieved according to the invention in that the radioactive elements are oxidized prior to the formation of the melt and the slag, and that for the purpose of oxidizing the radioactive elements, the contaminated metal parts are held in an oxygen-containing atmosphere for a period at a temperature below the melting temperature of the metal parts.
The temperature at which the oxidation occurs, must be as high as possible, i.e. be only slightly below the melting temperature, in order that, on the one hand, no melt is yet Replacement Page formed during the oxidation and, on the other hand, oxidation which is as complete as possible is made possible ~ ~he ox~dat~on process namely proceed$ be~t at ~gher temper~ture~, Due to the fact that all the contaminated metal parts, and not ~ust the radioactive elements exclusively, are sub]ected to an oxidation process, this process is advantageously simplified.
Since the radioactlve elements adhere to the surfaces of the metal parts, complete oxidation of these elements is ensured.
The fact that a relatively small part of the metal of which the metal parts themselves consist is also oxidized in the process does not impede the subsequent melt decontamination.
The oxides of the elements then preferentially pass into the slag during the melting process.
The method according to the invention particularly brings the advantage that the radioactive elements which are to be dissolved in the slag are present as oxid-es, the solubility of which, surprisingly, is greater in the slag than the solubility of the unoxidized elements. As a result, a significantly increased proportion of the elements which caused the contamination is advantageously removed from the metal melt. The metal melt and thus also shaped metal parts, produced therefrom for example, are as a result substantially decontaminated. The shaped metal parts can then be used without limitations.
Replacement Page The oxygen-containlng atmosphere may, for example, be dry or moist air. It is then unnecessary, advantageously, to provide any special oxygen-containing atmosphere.
The period for which the metal parts are held in the oxygen-containing atmosphere at a temperature below the melting temperature of the metal parts, for the purpose of oxidation, may, for example, be 10 minutes to 60 minutes long.
Sufficiently complete oxidation of the radioactive elements is ensured in a period of this length.
- The metal parts to be decontaminated may, for example, contain iron and/or copper.
The method according to the invention brings the advantage that a significantly improved degree of decontamination of metal parts is achieved using a melt decontamination. The shaped metal parts produced from the decontaminated metal melt can then be used without restrictions.
Replacement Page
Claims (3)
1. Method for recycling metal parts which are contaminated by radioactive elements, in particular by .alpha.-emitters, a melt and a slag being formed from the metal parts and the slag then being separated from the melt, characterized in that the radioactive elements are oxidized prior to the formation of the melt and the slag, and that for the purpose of oxidizing the radioactive elements, the contaminated metal parts are held in an oxygen-containing atmosphere for a period at a temperature below the melting temperature of the metal parts.
2. Method according to claim 1, characterized in that, the oxygen-containing atmosphere is dry or moist air.
3. Method according to one of claims 1 or 2, characterized in that the period is 10 minutes to 60 minutes long.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19546789.2 | 1995-12-14 | ||
| DE1995146789 DE19546789A1 (en) | 1995-12-14 | 1995-12-14 | Process for recycling contaminated metal parts |
| PCT/DE1996/002307 WO1997022124A2 (en) | 1995-12-14 | 1996-12-02 | Process for recycling contaminated metal parts |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2240421A1 true CA2240421A1 (en) | 1997-06-19 |
Family
ID=29403433
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2240421 Abandoned CA2240421A1 (en) | 1995-12-14 | 1996-12-02 | Process for recycling contaminated metal parts |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2240421A1 (en) |
-
1996
- 1996-12-02 CA CA 2240421 patent/CA2240421A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |