CA1229780A - Iron removal from edta solutions - Google Patents
Iron removal from edta solutionsInfo
- Publication number
- CA1229780A CA1229780A CA000457792A CA457792A CA1229780A CA 1229780 A CA1229780 A CA 1229780A CA 000457792 A CA000457792 A CA 000457792A CA 457792 A CA457792 A CA 457792A CA 1229780 A CA1229780 A CA 1229780A
- Authority
- CA
- Canada
- Prior art keywords
- solution
- exchange resin
- anion exchange
- loaded
- acid
- 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.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
- G21F9/007—Recovery of isotopes from radioactive waste, e.g. fission products
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
- G21F9/04—Treating liquids
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Treatment Of Water By Ion Exchange (AREA)
- External Artificial Organs (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Disclosed is a method of removing transition metals from a decontamination solution containing a com-plexing agent having an equilibrium constant for the ferric ion complex formation reaction of greater than 1022, such as ethylenediaminetetraacetic acid. An anion exchange resin is loaded with the complexing agent or one of its salts, and the solution is passed through the anion exchange resin. The process is applied to decontamination solutions which are used to clean cooling systems of nuclear reactors.
Disclosed is a method of removing transition metals from a decontamination solution containing a com-plexing agent having an equilibrium constant for the ferric ion complex formation reaction of greater than 1022, such as ethylenediaminetetraacetic acid. An anion exchange resin is loaded with the complexing agent or one of its salts, and the solution is passed through the anion exchange resin. The process is applied to decontamination solutions which are used to clean cooling systems of nuclear reactors.
Description
~ ~29 ~
1 51,129 IRON REMOVAL FROM ~DTA SOLIJTIONS
BACKGROUND OF THE INVENTION
Deposits that contain radioactive elements often form in the cooling systems of nuclear reactors. In order - to safely maintain and repair the cooling system, it is necessary to remove these radioactive deposits. This can be accomplished, for example, by using an oxidizing solution of alkali permanganate followed by a decontamination solution of oxalic acid, citric acid, and ethylenediaminetetraacetic acid (EDTA). The ~DTA forms a complex with the radioactive metal ions in the deposits, which solubilizes them. The decontamination solution is circulated between the cooling system and a cation exchange resin which exchanges the metal ions on the resin and frees the EDTA to solubilize additional metal ions.
s 1.~2~ 7~
1 51,129 IRON REMOVAL FROM ~DTA SOLIJTIONS
BACKGROUND OF THE INVENTION
Deposits that contain radioactive elements often form in the cooling systems of nuclear reactors. In order - to safely maintain and repair the cooling system, it is necessary to remove these radioactive deposits. This can be accomplished, for example, by using an oxidizing solution of alkali permanganate followed by a decontamination solution of oxalic acid, citric acid, and ethylenediaminetetraacetic acid (EDTA). The ~DTA forms a complex with the radioactive metal ions in the deposits, which solubilizes them. The decontamination solution is circulated between the cooling system and a cation exchange resin which exchanges the metal ions on the resin and frees the EDTA to solubilize additional metal ions.
s 1.~2~ 7~
2 51,129 ~ major difficulty with this process, however, is that EDTA does not readily yield up metal ions, par-ticularly the ferric ion, to the cation exchanye resin.
Thus, the concentration of the metal ion-EDTA complex builds up in the decontamination solution until it is no longer effective in solubilizing the metal ions in the deposits. When this happens, it is necessary to add fresh EDTA to the solution. This means that the solution must be constantly monitored to determine if the EDTA has been depleted so that more can be added. Also, great care must be taken not to add excess EDTA since EDTA is not very soluble unless it has fcrmc~ a complex with metal ions, and precipitated EDTA can itself be difficult to remove from the cooling system. Moreover, if excess EDTA is added, not only is the reagent wasted, but the additional EDTA must be removed from the solutisn at a later stage which adds to the volume of radioactive waste.
SUMMARY OF THE INVENTION
We have discovered a process for removing tran--ition metal ions from a decontamination solution contain-ing EDTA while regenerating the EDTA. Unlike the prior process which used a cation exchange resin, our process uses an anion exchange resin. The anion exchange resin is preloaded with EDTA anion so that the entire metal ion-EDTA
complex deposits on the ion exchange resin, releasing fresh EDTA from the anion exchange resin into the solution.
Thus, the concentration of uncomplexed EDTA in the solution remains fairly constant and it is not necessary to monitor the solution for the EDTA concentration or to add fresh EDTA.
DESCRIPTION OF THE INVENTION
The process of this invention can be applied to any solution containing a complex of a transition metal with a complexing agent having an equilibrium constant for the ferric ion complex formation reaction of greater than 1022. Examples of such complexing agents include ethylene-diaminetetraacetic acid, trans, 1, 2-diaminocyclohexane-9`-7~30
Thus, the concentration of the metal ion-EDTA complex builds up in the decontamination solution until it is no longer effective in solubilizing the metal ions in the deposits. When this happens, it is necessary to add fresh EDTA to the solution. This means that the solution must be constantly monitored to determine if the EDTA has been depleted so that more can be added. Also, great care must be taken not to add excess EDTA since EDTA is not very soluble unless it has fcrmc~ a complex with metal ions, and precipitated EDTA can itself be difficult to remove from the cooling system. Moreover, if excess EDTA is added, not only is the reagent wasted, but the additional EDTA must be removed from the solutisn at a later stage which adds to the volume of radioactive waste.
SUMMARY OF THE INVENTION
We have discovered a process for removing tran--ition metal ions from a decontamination solution contain-ing EDTA while regenerating the EDTA. Unlike the prior process which used a cation exchange resin, our process uses an anion exchange resin. The anion exchange resin is preloaded with EDTA anion so that the entire metal ion-EDTA
complex deposits on the ion exchange resin, releasing fresh EDTA from the anion exchange resin into the solution.
Thus, the concentration of uncomplexed EDTA in the solution remains fairly constant and it is not necessary to monitor the solution for the EDTA concentration or to add fresh EDTA.
DESCRIPTION OF THE INVENTION
The process of this invention can be applied to any solution containing a complex of a transition metal with a complexing agent having an equilibrium constant for the ferric ion complex formation reaction of greater than 1022. Examples of such complexing agents include ethylene-diaminetetraacetic acid, trans, 1, 2-diaminocyclohexane-9`-7~30
3 51,129 tetraacetic acid (DCTA), and oxybis (ethylenediaminetetra-acetic acid) (EEDTA). Common transition metals found in nuclear reactor decontamination solutions include iron, cobalt, nickel, and chromium. The temperature of the solution should be at least about 40C in order to keep the EDTA in solution and prevent it from precipitating. The temperature of the solution should be below about 100C, however, as anion exchange resins and the reagents used in the solution may de-compose above that temperature. The pH of the solution is not critical but it is typically about 2 to about 2 1/2 for most decontamination solutions due to the acidity of reagents which are present.
In the first step of the process of this invention, an anion exchange resin is loaded with EDTA, DCTA, or EEDTA.
Any anion exchange resin is suitable and may be used in this invention. The resin should be loaded with only EDTA, DCTA, or EEDTA and not with any other complexing agents because as the metal EDTA, DCTA, or EEDTA complex is absorbed by the resin, another anion (i.e., NTA, citric, or oxalic) would be released, diluting the concentration of EDTA, DTCA, or EEDTA in the solu-tion. Other complexing agents, such as NTA, or organic acids, such as citric acid and oxalic acid form much weaker transition metal complexes compared to those formed with EDTA, DTCA, or EEDTA and metals complexed with these other agents can be removed from solution by cation exchanges. This is not the case for EDTA, DCTA, or EEDTA metal complexes, and as a result, the metal remains in solution using conventional removal methods.
The anion exchange resin is most conveniently loaded with the EDTA, DCTA, or EETA anion by preparing a solution of the EDTA, DCTA, or EEDTA and passing the solution tnrough the anion exchange resin. It is preferable to use a solution of an EDTA, DCTA, or EEDTA salt, preferably an alkali metal salt, such as sodium EDTA, DCTA, or EEDTA to load the anion exchange resin with the EDTA, DCTA, or EEDTA anion, or this releases sodium hydroxide rather than just water into the solution. Since NaOH
is highly alkaline, (pH~12-14) the pH of the solution exiting the colurnn, after an initial rise, will fall back down to the pH of 1212~
In the first step of the process of this invention, an anion exchange resin is loaded with EDTA, DCTA, or EEDTA.
Any anion exchange resin is suitable and may be used in this invention. The resin should be loaded with only EDTA, DCTA, or EEDTA and not with any other complexing agents because as the metal EDTA, DCTA, or EEDTA complex is absorbed by the resin, another anion (i.e., NTA, citric, or oxalic) would be released, diluting the concentration of EDTA, DTCA, or EEDTA in the solu-tion. Other complexing agents, such as NTA, or organic acids, such as citric acid and oxalic acid form much weaker transition metal complexes compared to those formed with EDTA, DTCA, or EEDTA and metals complexed with these other agents can be removed from solution by cation exchanges. This is not the case for EDTA, DCTA, or EEDTA metal complexes, and as a result, the metal remains in solution using conventional removal methods.
The anion exchange resin is most conveniently loaded with the EDTA, DCTA, or EETA anion by preparing a solution of the EDTA, DCTA, or EEDTA and passing the solution tnrough the anion exchange resin. It is preferable to use a solution of an EDTA, DCTA, or EEDTA salt, preferably an alkali metal salt, such as sodium EDTA, DCTA, or EEDTA to load the anion exchange resin with the EDTA, DCTA, or EEDTA anion, or this releases sodium hydroxide rather than just water into the solution. Since NaOH
is highly alkaline, (pH~12-14) the pH of the solution exiting the colurnn, after an initial rise, will fall back down to the pH of 1212~
4 51,129 the sodium EDTA, DCTA, or EEDTA (pH~4-5) as fewer hydroxide groups of the preferred strong base anion exchange resin are replaced by the EDTA, DCTA, or EEDTA anion. Thus, by monitoring the pH of the solution leaving the resin, one can then determine when the resin has been fully loaded. After the pH falls to below abou-t 6, the resin should be considered to be fully loaded with EDTA, DCTA, or EEDTA anion. While the acid form of EDTA, DCTA, or EEDTA can be used, it is more difficult to determine when the resin has been loaded because, without the presence of the sodium ion, the solution leaving the columns will be at approximately a neutral pH value (~7). Thus, the difference in pH values of the column feed (about 4.5) and the column effluent (about 7) is significantly less than when the sodium salt is used. Also, the acid form of EDTA, D~TA, or EEDTA is not very soluble in water, which means that the solution must be more dilute.
In the next step of the precess of this invention, the decontamination solution containing the metal ion-EDTA, DCTA, or EEDTA complex is circulated between the EDTA, DCTA, or EEDTA
loaded anion exchange resin and the reactor cooling system, or the portion thereof that is being decontaminated, such as the steam generator of a pressurized water reactor or a boiling water reactor. As the metal ion-EDTA, DCTA, or EEDTA complex is absorbed onto the EDTA, DCTA, or EEDTA anion exchange resin, fresh EDTA, DCTA, or EEDTA is released into the contamination solution. The solution is circulated until the concentration of metal ions in the solution leaving the cooling system is not substantially greater than the concentration of metal ions in the solution entering the cooling system.
After the metal ion-EDTA, DCTA, or EEDTA complex has been removed, the EDTA and any remaining ions in the solution can be removed by passing the solution through a fresh anion exchange resin or a mixed anion-cation exchange resin, which results in relatively pure water. When the preloaded anion exchange resin has been saturated with -the metal ion-EDTA, DCTA, or EEDTA complex, it is disposed of as radioactive waste.
~p~
51,129 The following examples further illustrate this invention.
, !EXAMPLE
e f ~
A 1 inch ~m~~glass column 18 inches long was partially filled with 100 ml of an anion exchange resin sold by Rohm and Haas under the trade designation "IRA-400," a strong-based polystyrene resin having a particle size between 16 and 50 mesh. A solution was prepared of 100 grams/liter of the di~odium salt of EDTA. The solu-tion, which had a pH of 4.38, was fed through the top ofthe column at 1-3 bed volumes/hr. and the pH of the solu-tion leaving the bottom of the column was measured. The following table gives the pH of the solution leaving the column after various bed volumes of the solution had flowed through the column.
BED VOL~ME pH
0.5 11.85 1.0 12.86 1.5 12.94 2.0 12.36 2.5 6.56 3.0 5.90 3.5 5.64 4.0 5.47 4.5 5.29
In the next step of the precess of this invention, the decontamination solution containing the metal ion-EDTA, DCTA, or EEDTA complex is circulated between the EDTA, DCTA, or EEDTA
loaded anion exchange resin and the reactor cooling system, or the portion thereof that is being decontaminated, such as the steam generator of a pressurized water reactor or a boiling water reactor. As the metal ion-EDTA, DCTA, or EEDTA complex is absorbed onto the EDTA, DCTA, or EEDTA anion exchange resin, fresh EDTA, DCTA, or EEDTA is released into the contamination solution. The solution is circulated until the concentration of metal ions in the solution leaving the cooling system is not substantially greater than the concentration of metal ions in the solution entering the cooling system.
After the metal ion-EDTA, DCTA, or EEDTA complex has been removed, the EDTA and any remaining ions in the solution can be removed by passing the solution through a fresh anion exchange resin or a mixed anion-cation exchange resin, which results in relatively pure water. When the preloaded anion exchange resin has been saturated with -the metal ion-EDTA, DCTA, or EEDTA complex, it is disposed of as radioactive waste.
~p~
51,129 The following examples further illustrate this invention.
, !EXAMPLE
e f ~
A 1 inch ~m~~glass column 18 inches long was partially filled with 100 ml of an anion exchange resin sold by Rohm and Haas under the trade designation "IRA-400," a strong-based polystyrene resin having a particle size between 16 and 50 mesh. A solution was prepared of 100 grams/liter of the di~odium salt of EDTA. The solu-tion, which had a pH of 4.38, was fed through the top ofthe column at 1-3 bed volumes/hr. and the pH of the solu-tion leaving the bottom of the column was measured. The following table gives the pH of the solution leaving the column after various bed volumes of the solution had flowed through the column.
BED VOL~ME pH
0.5 11.85 1.0 12.86 1.5 12.94 2.0 12.36 2.5 6.56 3.0 5.90 3.5 5.64 4.0 5.47 4.5 5.29
5.0* 5.15
6.0 5.07 *A new solution was prepared having a pH of 4.49.
The above table shows that, after an initial start-up time, the pH of the solution leaving the resin fell to close to the pH of the solution entering the resin. This indicated that the column was almost satur-ated with EDTA.
6 51,129 Simulated spent decontamination solutions were prepared by dissolving 50, lO0, and 200 ppm of iron (from magnetite, Fe304) in three 0.5 weight percent solutions of a commercially available decontamination agent believed to be 30% citric acid, 30% oxalic acid, 40% EDTA, and contain-ing an inhibitor believed to be thiourea. The three solutions were mixed in beakers with the preloaded anion exchange resin prepared in Example 1 at 54C. After 5 hours the solutions were tested and were found to contain 3, 11, and 46 ppm of iron, respectively. This established that the EDTA-loaded anio.. exchange resin successfully removed iron from the solutions.
A 100-ml sample of the EDTA-loaded anion exchange resin prepared as in Example 1 was placed in a 1 inch glass column 18 inches long. A 0.5% solution of the commercially available decontamination agent (described in Example 2) which contained 80 ppm of iron was passed through the column at 12 bed volumes/hr. from top to bottomJand the iron, oxalate, citrate, and EDTA concentra-tions in the solution leaving the column were measured.
The following table gives their concentrations.
3~
The above table shows that, after an initial start-up time, the pH of the solution leaving the resin fell to close to the pH of the solution entering the resin. This indicated that the column was almost satur-ated with EDTA.
6 51,129 Simulated spent decontamination solutions were prepared by dissolving 50, lO0, and 200 ppm of iron (from magnetite, Fe304) in three 0.5 weight percent solutions of a commercially available decontamination agent believed to be 30% citric acid, 30% oxalic acid, 40% EDTA, and contain-ing an inhibitor believed to be thiourea. The three solutions were mixed in beakers with the preloaded anion exchange resin prepared in Example 1 at 54C. After 5 hours the solutions were tested and were found to contain 3, 11, and 46 ppm of iron, respectively. This established that the EDTA-loaded anio.. exchange resin successfully removed iron from the solutions.
A 100-ml sample of the EDTA-loaded anion exchange resin prepared as in Example 1 was placed in a 1 inch glass column 18 inches long. A 0.5% solution of the commercially available decontamination agent (described in Example 2) which contained 80 ppm of iron was passed through the column at 12 bed volumes/hr. from top to bottomJand the iron, oxalate, citrate, and EDTA concentra-tions in the solution leaving the column were measured.
The following table gives their concentrations.
3~
7 51,129 IRON OXALATE CITRATE EDTA
~ED VOLUME ~ppm) (mg/ml) ~ mi) (ppm, Feed 80 1080 1000 1384 10 to 11 39 10 290 4100 5 20 to 21 35 - 10 760 4366 40 to 41 37 10 1370 3352 60 to 61 14 78 1340 2521 80 to 81 8.8 430 1130 1783 90 to 91 3.8 500 910 984 100 to 101 1.0 830 970 1332 The above table shows that, after an initial start-up period, the EDTA-loaded column successfully removed iron in the solution to levels below lO ppm.
~ED VOLUME ~ppm) (mg/ml) ~ mi) (ppm, Feed 80 1080 1000 1384 10 to 11 39 10 290 4100 5 20 to 21 35 - 10 760 4366 40 to 41 37 10 1370 3352 60 to 61 14 78 1340 2521 80 to 81 8.8 430 1130 1783 90 to 91 3.8 500 910 984 100 to 101 1.0 830 970 1332 The above table shows that, after an initial start-up period, the EDTA-loaded column successfully removed iron in the solution to levels below lO ppm.
Claims (14)
1. A method of removing ferric ion from a solution containing a complexing agent selected from the group consisting of ethylenediaminetetraacetic acid, trans, 1,2-diaminocyclohex-anetetraacetic acid, oxybis (ethylenediaminetetraacetic acid), and mixtures thereof, comprising loading an anion exchange resin with said complexing agent or a salt thereof and circulating said solution through said anion exchange resin.
2. A method according to Claim 1 wherein said com-plexing agent is ethylenediaminetetraacetic acid.
3. A method according to Claim 2 wherein said anion exchange resin is loaded with an alkali metal salt of ethylene-diaminetetraacetic acid.
4. A method according to Claim 1 wherein said anion exchange resin is loaded by passing a solution of said salt through said resin until the pH of said solution as it leaves said resin is less than 6.
5. A method according to Claim 1 wherein the temper-ature of said decontamination solution is maintained at about 40 to about 100°C.
6. A method according to Claim 1 wherein said de-contamination solution also contains citric acid and oxalic acid.
7. In a method of decontaminating a steam generator of a pressurized water nuclear reactor wherein a decontamination solution containing ethylenediaminetetraacetic acid is circu-lated through said generator to solubilize ferric ion in deposits therein by forming a complex therewith, an improved method of removing said ferric ion from said decontamination solution and of regenerating said ethylenediaminetetraacetic acid in said solution, comprising circulating said decontamination solution through an anion exchange resin loaded with the anion of ethylenediaminetetraacetic acid.
8. A method according to Claim 7 wherein said anion exchange resin is loaded by treating a basic anion exchange resin in hydroxyl form with an alkali metal salt of ethylene-diaminetetraacetic acid.
9. A method according to Claim 8 wherein said anion exchange resin is loaded by passing a solution of said salt through said basic anion exchange resin until the pH of said solution as it leaves said resin falls below 6.
10. A method according to Claim 7 wherein said decontamination solution is circulated between said generator and said anion exchange resin until the concentration of said metals in said solution as it leaves said generator is not substantially greater than the concentration of said metals in said solution as it enters said generator.
11. A method according to Claim 7 wherein the temperature of said decontamination solution is maintained at about 40 to about 100°C.
12. A method according to Claim 7 wherein said decontamination solution also contains citric acid and oxalic acid.
13. A method according to Claim 1 wherein said anion exchange resin is loaded with a salt of said complexing agent.
14. A method according to Claim 7 wherein said anion exchange resin is loaded with an alkali metal salt of ethylene-diaminetetraacetic acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US51356783A | 1983-07-14 | 1983-07-14 | |
| US513,567 | 1983-07-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1229780A true CA1229780A (en) | 1987-12-01 |
Family
ID=24043815
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000457792A Expired CA1229780A (en) | 1983-07-14 | 1984-06-28 | Iron removal from edta solutions |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0135276B1 (en) |
| JP (1) | JPS6039596A (en) |
| KR (1) | KR910006798B1 (en) |
| CA (1) | CA1229780A (en) |
| DE (1) | DE3480446D1 (en) |
| ES (1) | ES8607740A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0778554B2 (en) * | 1987-05-26 | 1995-08-23 | 荏原工業洗浄株式会社 | Method for treating radioactive waste liquid containing chelate compound |
| US6375850B1 (en) * | 1999-01-21 | 2002-04-23 | United States Enrichment Corp. | Method for removing metals from a cleaning solution |
| KR100699257B1 (en) | 2004-08-09 | 2007-03-27 | 삼성전자주식회사 | microwave |
| RU2458418C1 (en) * | 2012-01-10 | 2012-08-10 | Федеральное государственное унитарное предприятие "Научно-исследовательский технологический институт имени А.П. Александрова" | Method for removing transition metals and radionuclides from solutions containing complexing agent |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5840466B2 (en) * | 1979-10-26 | 1983-09-06 | 東洋醸造株式会社 | Production method of acyl-CoA oxidase |
| GB2077482B (en) * | 1980-06-06 | 1983-06-08 | Us Energy | Coolant system decontamination |
-
1984
- 1984-06-28 CA CA000457792A patent/CA1229780A/en not_active Expired
- 1984-07-11 DE DE8484304725T patent/DE3480446D1/en not_active Expired
- 1984-07-11 EP EP84304725A patent/EP0135276B1/en not_active Expired
- 1984-07-12 ES ES534265A patent/ES8607740A1/en not_active Expired
- 1984-07-13 JP JP59144539A patent/JPS6039596A/en active Pending
- 1984-07-13 KR KR1019840004109A patent/KR910006798B1/en active IP Right Grant
Also Published As
| Publication number | Publication date |
|---|---|
| EP0135276B1 (en) | 1989-11-08 |
| ES534265A0 (en) | 1986-06-01 |
| DE3480446D1 (en) | 1989-12-14 |
| KR850001623A (en) | 1985-03-30 |
| EP0135276A1 (en) | 1985-03-27 |
| JPS6039596A (en) | 1985-03-01 |
| KR910006798B1 (en) | 1991-09-02 |
| ES8607740A1 (en) | 1986-06-01 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |