US3873362A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for cleaning radioactively contaminated metal surfaces
Assignee: Halliburton Co
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Filing: 1973-05-29
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Granted: 1975-03-25
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Expires: 1993-05-29
Abstract
Abstract A process for removing radioactive scale from a ferrous metal surface, including the steps of initially pre-conditioning the surface by contacting it with an oxidizing solution (such as an aqueous solution of an alkali metal permanganate or hydrogen peroxide), then, after removal or decomposition of the oxidizing solution, the metallic surface is contacted with a cleaning solution which is a mixture of a mineral acid and a complexing agent (such as sulfuric acid and oxalic acid), and which preferably contains a corrosion inhibitor. A final step in the process is the treatment of the spent cleaning solution containing radioactive waste materials in solution by adding a reagent selected from the group consisting of calcium hydroxide or potassium permanganate and an alkali metal hydroxide to thereby form easily recovered metallic compounds containing substantially all of the dissolved metals and radioactivity.
Inventors
- 👤 Russell G Mihram
- 👤 Gerald A Snyder
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 21:23
CPC Classifications
G; G21; G21F; G21F9/00; G21F9/001; G21F9/002; G21F9/004; C; C23; C23G; C23G1/00; C23G1/02; C23G1/08
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
158 words
A PROCESS FOR CLEANING RADIOACTIVELY CONTAMINATED FERROUS METAL SURFACES WITH AQUEOUS SOLUTIONS, AND REMOVING THE RADIOACTIVE MATERIALS THEREFROM, COMPRISING: CONTACTING THE METAL SURFACE WITH AN AQUEOUS SOLUTION CONTAINING AN OXIDIZING AGENT TO PRE-CONDITION THE CONTAMINANTS ON THE METAL SURFACE, AND FACILITATE THEIR REMOVAL IN ACID SOLUTION; CONTACTING THE METAL SURFACE WITH A MIXTURE OF AN AQUEOUS SOLUTION OF MINERAL ACID AND A COMPLEXING AGENT AT A TEMPERATURE OF AT LEAST ABOUT 180*F TO DISSOLVE THE SCALE CARRIED ON THE METAL; THEN REMOVING THE SPENT MINERAL ACID SOLUTION FROM CONTACT WITH THE METAL SURFACE; AND ADDING TO THE SPENT ACID SOLUTION, A MATERIAL SELECTED FROM THE GROUP CONSISTING OF (A) AN ALKALI METAL PERMANGANATE FOLLOWED BY A PH ADJUSTING BASIC COMPOUND, (B) ALKALINE EARTH OXIDES AND (C) ALKALINE EARTH HYDROXIDES TO FORM WITH SOLUTES OF THE SPENT ACID SOLUTION, PRECIPITATABLE COMPOUNDS, AND PRECIPITATING SOLID COMPOUND FROM THE ACID SOLUTION TO REMOVE A MAJOR PORTION OF THE RAIOACTIVE MATERIALS THEREFROM.
Claim 2
Dependent Claim
158 words
A PROCESS FOR CLEANING RADIOACTIVELY CONTAMINATED FERROUS METAL SURFACES WITH AQUEOUS SOLUTIONS, AND REMOVING THE RADIOACTIVE MATERIALS THEREFROM, COMPRISING: CONTACTING THE METAL SURFACE WITH AN AQUEOUS SOLUTION CONTAINING AN OXIDIZING AGENT TO PRE-CONDITION THE CONTAMINANTS ON THE METAL SURFACE, AND FACILITATE THEIR REMOVAL IN ACID SOLUTION; CONTACTING THE METAL SURFACE WITH A MIXTURE OF AN AQUEOUS SOLUTION OF MINERAL ACID AND A COMPLEXING AGENT AT A TEMPERATURE OF AT LEAST ABOUT 180*F TO DISSOLVE THE SCALE CARRIED ON THE METAL; THEN REMOVING THE SPENT MINERAL ACID SOLUTION FROM CONTACT WITH THE METAL SURFACE; AND ADDING TO THE SPENT ACID SOLUTION, A MATERIAL SELECTED FROM THE GROUP CONSISTING OF (A) AN ALKALI METAL PERMANGANATE FOLLOWED BY A PH ADJUSTING BASIC COMPOUND, (B) ALKALINE EARTH OXIDES AND (C) ALKALINE EARTH HYDROXIDES TO FORM WITH SOLUTES OF THE SPENT ACID SOLUTION, PRECIPITATABLE COMPOUNDS, AND PRECIPITATING SOLID COMPOUND FROM THE ACID SOLUTION TO REMOVE A MAJOR PORTION OF THE RAIOACTIVE MATERIALS THEREFROM.
Claim 3
Dependent Claim
34 words
A process as defined in claim 1 wherein said aqueous solution containing an oxidizing agent consists essentially of an aqueous solution containing from about 1 weight percent to about 5 weight percent hydrogen peroxide.
Claim 4
Dependent Claim
29 words
A process as defined in claim 2 wherein the aqueous hydrogen peroxide solution is contacted with the metal surface at a temperature of from about 90*F to about 150*F.
Claim 5
Dependent Claim
21 words
The process defined in claim 2 wherein said aqueous solution containing an oxidizing agent contains about 2 weight percent hydrogen peroxide.
Claim 6
Dependent Claim
61 words
A process as defined in claim 2 wherein said contact of the metal surface with oxidizing agent is carried out for a period of from about 1 hour to about 5 hours, and following such contact, the hydrogen peroxide is destroyed by heating the hydrogen peroxide solution to a temperature of at least 160*F at a pH of at least 9.
Claim 7
Dependent Claim
48 words
A process as defined in claim 1 wherein said mixture of mineral acid and complexing agent consists essentially of an aqueous solution containing from about 1 weight percent to about 10 weight percent sulfuric acid, and from about 1 weight percent to about 7 weight percent oxalic acid.
Claim 8
Dependent Claim
26 words
The process defined in claim 6 wherein said mixture of mineral acid and complexing agent includes an effective amount of a ferrous metal corrosion inhibiting compound.
Claim 9
Dependent Claim
34 words
A process as defined in claim 7 wherein said aqueous solution containing an oxidizing agent consists essentially of an aqueous solution containing from about 1 weight percent to about 5 weight percent hydrogen peroxide.
Claim 10
Dependent Claim
36 words
A process as defined in claim 8 wherein said mixture of mineral acid and complexing agent consists essentially of an aqueous solution containing about 4 weight percent sulfuric acid and about 2 weight percent oxalic acid.
Claim 11
Dependent Claim
39 words
A process as defined in claim 8 wherein the material added to the spent acid solution is calcium hydroxide in an amount at least sufficient to neutralize all sulfuric acid and all oxalic acid in said spent acid solution.
Claim 12
Dependent Claim
34 words
A process as defined in claim 10 and further characterized in including the steps of rinsing the metal surface with demineralized water after removing the spent mineral acid from contact with the metal surface.
Claim 13
Dependent Claim
31 words
The process defined in claim 6 wherein said mixture of mineral acid and complexing agent consists essentially of about 4 weight percent sulfuric acid and about 2 weight percent oxalic acid.
Claim 14
Dependent Claim
23 words
The process defined in claim 6 wherein the metal surface is contacted with said aqueous acid solution at a temperature of about 205*F.
Claim 15
Dependent Claim
25 words
The process defined in claim 6 wherein the metal surface is contacted with said aqueous acid solution for a period of at least 20 hours.
Claim 16
Dependent Claim
19 words
A process as defined in claim 1 wherein the material added to the spent acid solution is calcium hydroxide.
Claim 17
Dependent Claim
33 words
A process as defined in claim 1 and further characterized in the step of rinsing the metal surface with demineralized water after removing the spent mineral acid from contact with the metal surface.
Claim 18
Dependent Claim
16 words
A process as defined in claim 1 wherein the metal cleaned is a 304 stainless steel.
Claim 19
Dependent Claim
44 words
The process defined in claim 1 wherein the material added to the spent acid solution is potassium permanganate and an amount of alkali metal hydroxide effective to adjust the pH of the spent acid solution and the added potassium permanganate to at least 10.
Claim 20
Dependent Claim
22 words
A process as defined in claim 1 wherein said aqueous solution containing an oxidizing agent contains potassium permanganate as the oxidizing agent.
Claim 21
Dependent Claim
127 words
A process for cleaning radioactivity contaminated ferrous metal surfaces comprising: contacting the metal surface with an aqueous solution containing from about 1 weight percent to about 5 weight percent hydrogen peroxide at a temperature of from about 90*F to about 150*F for a period of at least 1 hour; ceasing contacting the metal surface with hydrogen peroxide; contacting the metal surface with an aqueous acidic solution containing from about 1 weight percent to about 10 weight percent sulfuric acid and from about 1 weight percent to about 7 weight percent oxalic acid and a ferrous metal corrosion inhibitor compound at a temperature of at least 180*F and for a period of at least 20 hours; and removing the aqueous acidic solution from contact with the metal surface.
Claim 22
Dependent Claim
127 words
A process for cleaning radioactivity contaminated ferrous metal surfaces comprising: contacting the metal surface with an aqueous solution containing from about 1 weight percent to about 5 weight percent hydrogen peroxide at a temperature of from about 90*F to about 150*F for a period of at least 1 hour; ceasing contacting the metal surface with hydrogen peroxide; contacting the metal surface with an aqueous acidic solution containing from about 1 weight percent to about 10 weight percent sulfuric acid and from about 1 weight percent to about 7 weight percent oxalic acid and a ferrous metal corrosion inhibitor compound at a temperature of at least 180*F and for a period of at least 20 hours; and removing the aqueous acidic solution from contact with the metal surface.
Claim 23
Dependent Claim
35 words
A process as defined in claim 20 wherein contact of the metal surface with hydrogen peroxide is ceased by elevating the pH and heating the aqueous solution of hydrogen peroxide to Decompose the hydrogen peroxide.
Claim 24
Dependent Claim
20 words
A process as defined in claim 20 wherein said aqueous hydrogen peroxide solution contains about 2 weight percent hydrogen peroxide.
Claim 25
Dependent Claim
26 words
A process as defined in claim 22 wherein said aqueous acidic solution contains about 4 weight percent sulfuric acid and about 2 weight percent oxalic acid.
Claim 26
Dependent Claim
39 words
A process as defined in claim 23 wherein the metal surface is contacted with the aqueous hydrogen peroxide solution at a temperature of about 125*F, and is contacted with the aqueous acidic solution at a temperature of about 205*F.
Claim 27
Dependent Claim
26 words
A process as defined in claim 20 wherein said aqueous acidic solution contains about 4 weight percent sulfuric acid and about 2 weight percent oxalic acid.
Claim 28
Dependent Claim
24 words
A process as defined in claim 20 wherein the metal surface is contacted with the aqueous acidic solution at a temperature of about 205*F.
Claim 29
Dependent Claim
25 words
A process as defined in claim 20 wherein the metal surface is contacted with the aqueous hydrogen peroxide solution at a temperature of about 125*F.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-03-24 | 1978-09-23 | 1979-03-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-24 | 1982-09-23 | 1983-03-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-24 | 1986-09-23 | 1987-03-25 | $7700.00 | Window Closed / Lapsed |