US4587043A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Decontamination of metal surfaces in nuclear power reactors
Assignee: Westinghouse Electric Corp
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Filing: 1983-06-07
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Granted: 1986-05-06
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Expires: 2003-06-07
Abstract
Abstract A method for decontaminating metal surfaces having radioactive oxide deposits thereon is disclosed which comprises preparing a decontamination solution having a pH of about 1.5 to about 4 comprising water, about 0.02 to about 0.5% of a water soluble organic acid which has an equilibrium constant in a complex with ferric ion of at least about 109 and which is capable of producing a pH of about 2 to about 3 in water, and about 0.01 to about 0.4% of a chelate in free acid form which has an equilibrium constant in a complex with ferric ion of about 1015 to about 1019 and which is at least 0.4% soluble at 40 DEG C. in water having a pH of about 2 to about 3. An apparatus for performing the above method is disclosed.
Inventors
- 👤 Alexander P. Murray
- 👤 Sharon L. Weisberg
- 👤 Lawrence F. Becker, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 11:46
CPC Classifications
G; G21; G21F; G21F9/00; G21F9/001; G21F9/002; G21F9/004; Y; Y02; Y02E; Y02E30/00; Y10; Y10S; Y10S422/00; Y10S422/903
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
260 words
A method of decontaminating metal surfaces coated with oxides containing radioactive substances comprising: (A) providing a decontamination solution which comprises (1) water; (2) about 0.02 to about 0.5% of at least one water-soluble organic acid which has an equilibrium constant in a complex with ferric ion of at least 10 9 , and which is capable of producing a pH of 2 to 3 in water; and (3) about 0.01 to about 0.4% of a chelate in free acid form which has an equilibrium constant in a complex with ferric ion of about 10 15 to about 10 19 , and which is soluble at at least 0.4% at 40° C. in water having a pH of about 2 to about 3; (B) heating said decontamination solution to about 70° to about 200° C.; (C) circulating said decontamination solution over said metal surfaces and through a cation exchange resin until the radioactivity of said decontamination solution does not increase significantly after contacting said metal surfaces; (D) providing an oxidizing solution which comprises (1) water; (2) 0.2 to 2.5% of an alkali metal permanganate; and (3) about 0.2 to about 2.5% of an alkali metal hydroxide; (E) heating said oxidizing solution to about 70° to about 200° C.; (F) circulating said oxidizing solution over said metal surfaces until the dichromate level in said oxidizing solution ceases to increase significantly; and (G) circulating said decontamination solution over said metal surfaces and through a cation exchange resin until the radioactivity of said decontamination solution does not increase significantly after contacting said metal surfaces.
Claim 2
Independent Claim
260 words
A method of decontaminating metal surfaces coated with oxides containing radioactive substances comprising: (A) providing a decontamination solution which comprises (1) water; (2) about 0.02 to about 0.5% of at least one water-soluble organic acid which has an equilibrium constant in a complex with ferric ion of at least 10 9 , and which is capable of producing a pH of 2 to 3 in water; and (3) about 0.01 to about 0.4% of a chelate in free acid form which has an equilibrium constant in a complex with ferric ion of about 10 15 to about 10 19 , and which is soluble at at least 0.4% at 40° C. in water having a pH of about 2 to about 3; (B) heating said decontamination solution to about 70° to about 200° C.; (C) circulating said decontamination solution over said metal surfaces and through a cation exchange resin until the radioactivity of said decontamination solution does not increase significantly after contacting said metal surfaces; (D) providing an oxidizing solution which comprises (1) water; (2) 0.2 to 2.5% of an alkali metal permanganate; and (3) about 0.2 to about 2.5% of an alkali metal hydroxide; (E) heating said oxidizing solution to about 70° to about 200° C.; (F) circulating said oxidizing solution over said metal surfaces until the dichromate level in said oxidizing solution ceases to increase significantly; and (G) circulating said decontamination solution over said metal surfaces and through a cation exchange resin until the radioactivity of said decontamination solution does not increase significantly after contacting said metal surfaces.
Claim 3
Dependent Claim
12 words
A method according to claim 1 including repeating steps (F) and (G).
Claim 4
Dependent Claim
13 words
A method according to claim 1 wherein said organic acid is citric acid.
Claim 5
Dependent Claim
12 words
A method according to claim 1 wherein said chelate is nitrilotriacetic acid.
Claim 6
Dependent Claim
22 words
A method according to claim 1 wherein said alkali metal permanganate is potassium permanganate and said alkali metal hydroxide is sodium hydroxide.
Claim 7
Dependent Claim
48 words
A method according to claim 1 wherein said oxidizing solution is about 0.5 to about 1% alkali metal permanganate and about 0.5 to about 1% alkali metal hydroxide, and said decontamination solution is about 0.05 to about 3% citric acid and about 0.03 to about 0.2% nitrilotriacetic acid.
Claim 8
Dependent Claim
12 words
A method according to claim 1 wherein said water is deionized water.
Claim 9
Dependent Claim
19 words
A method according to claim 1 including the additional last step of rinsing said metal surfaces with deionized water.
Claim 10
Dependent Claim
22 words
A method according to claim 1 wherein said metal surfaces are tubes in a steam generator of a pressurized water nuclear reactor.
Claim 11
Dependent Claim
27 words
A method according to claim 9 wherein said decontamination solution is forced up and down said tubes several times before being circulated to said cation exchange resin.
Claim 12
Dependent Claim
33 words
A method according to claim 1 including the additional last step of circulating said decontamination solution through an anion exchange resin, and circulating said oxidizing solution through a second mixed anion-cation exchange resin.
Claim 13
Dependent Claim
40 words
A method according to claim 11 wherein said cation exchange resin is a strong acid, said anion exchange resin is a weak base, and said mixed anion-cation exchange resins are a mixture of a strong acid with a strong base.
Claim 14
Dependent Claim
46 words
A method according to claim 1 including the additional steps between steps (C) and (D), and between steps (F) and (G), of rinsing said metal surfaces with water heated to about 70° to about 200° C. and passing said water over a mixed anion-cation exchange resin.
Claim 15
Independent Claim
139 words
An apparatus for decontaminating metal surfaces having a coating thereon which contains a radioactive substance comprising: (A) a decontamination tank for holding a decontamination solution; (B) means for circulating said decontamination solution between said decontamination tank and said metal surfaces; (C) a cation exchange column containing a cation exchange resin; (D) means for circulating said decontamination solution between said decontamination tank and said cation exchange column; (E) an oxidizing tank for holding an oxidizing solution; (F) means for circulating said oxidizing solution between said oxidizing tank and said metal surfaces; (G) a water tank for holding water; (H) means for circulating water between said water tank and said metal surfaces; (I) a mixed anion-cation exchange column containing a mixed anion-cation exchange resin; and (J) means for circulating said water between said water tank and said mixed anion-cation exchange column.
Claim 16
Independent Claim
139 words
An apparatus for decontaminating metal surfaces having a coating thereon which contains a radioactive substance comprising: (A) a decontamination tank for holding a decontamination solution; (B) means for circulating said decontamination solution between said decontamination tank and said metal surfaces; (C) a cation exchange column containing a cation exchange resin; (D) means for circulating said decontamination solution between said decontamination tank and said cation exchange column; (E) an oxidizing tank for holding an oxidizing solution; (F) means for circulating said oxidizing solution between said oxidizing tank and said metal surfaces; (G) a water tank for holding water; (H) means for circulating water between said water tank and said metal surfaces; (I) a mixed anion-cation exchange column containing a mixed anion-cation exchange resin; and (J) means for circulating said water between said water tank and said mixed anion-cation exchange column.
Claim 17
Dependent Claim
37 words
Apparatus according to claim 14 including: (A) an anion exchange column containing an anion exchange resin; and (B) means for circulating said decontamination solution from said decontamination tank through said oxidizing tank and said anion exchange column.
Claim 18
Dependent Claim
39 words
Apparatus according to claim 14 including: (A) a second mixed anion-cation exchange column containing a second mixed anion-cation exchange resin; and (B) means for circulating said oxidizing solution from said oxidizing tank to said second mixed anion-cation exchange column.
Claim 19
Dependent Claim
36 words
Apparatus according to claim 14 wherein said cation exchange resin is a strong acid, said anion exchange resin is a weak base, and said mixed anion-cation exchange resin is a strong acid with a strong base.
References Cited (Backward Citations)
US3080262A
Cited
US3258429A
Cited
US3496017A
Cited
US3522093A
Cited
US3613909A
Cited
US3615817A
Cited
US3664870A
Cited
US3873362A
Cited
US4287002A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-05-05 | 1989-11-04 | 1990-05-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-05-05 | 1993-11-04 | 1994-05-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-05-05 | 1997-11-04 | 1998-05-06 | $7700.00 | Window Closed / Lapsed |