CA1062590A - Reactor decontamination process - Google Patents
Reactor decontamination processInfo
- Publication number
- CA1062590A CA1062590A CA244,084A CA244084A CA1062590A CA 1062590 A CA1062590 A CA 1062590A CA 244084 A CA244084 A CA 244084A CA 1062590 A CA1062590 A CA 1062590A
- Authority
- CA
- Canada
- Prior art keywords
- acid
- reagent
- edta
- decontaminating
- hydroxylamine
- 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
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/36—Regeneration of waste pickling liquors
-
- 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
-
- 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
- G21F9/001—Decontamination of contaminated objects, apparatus, clothes, food; Preventing contamination thereof
- G21F9/002—Decontamination of the surface of objects with chemical or electrochemical processes
- G21F9/004—Decontamination of the surface of objects with chemical or electrochemical processes of metallic surfaces
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physics & Mathematics (AREA)
- Electrochemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Food Science & Technology (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method of decontaminating a water cooled nuclear reactor and novel compositions employed therein are described.
A relatively small quantity of acidic reagent composition is injected into the circulating coolant of the reactor, which is shut down but not defueled, so as to provide a dilute solution of reagent which dissolves radioactive contaminants in the system. The coolant is then passed through cationic exchange resin to remove the contaminant and leave the regenerated reagent which is returned to the cooling system. When the cationic resin stops removing contaminants it is removed and normally discarded. The reagent is finally removed from the system by anionic exchange resin. Suitable reagents include mixtures of certain organic acids with or without complexing agents.
A method of decontaminating a water cooled nuclear reactor and novel compositions employed therein are described.
A relatively small quantity of acidic reagent composition is injected into the circulating coolant of the reactor, which is shut down but not defueled, so as to provide a dilute solution of reagent which dissolves radioactive contaminants in the system. The coolant is then passed through cationic exchange resin to remove the contaminant and leave the regenerated reagent which is returned to the cooling system. When the cationic resin stops removing contaminants it is removed and normally discarded. The reagent is finally removed from the system by anionic exchange resin. Suitable reagents include mixtures of certain organic acids with or without complexing agents.
Description
106Z5~0 This invention relates to a method of decontaminating a ,heavy water moderated and cooled reactor or an ordinary water-cooled reactor, including the fuel assemblies and associated heat transport systems. The invention also relates to novel reagent compositions which may be used in the aforesaid method.
More particularly the invention relates to the injection of a relatively small quantity of a reagent composition directly in-to the circulating reactor coolant - either water (H2O) or heavy water (D2O) - so that the coolant acts as a carrier for the reagent in dilute solution therein. The reagent dissolves the active corrosion products containing radioactive contamina-tion, and these are removed by passing the coolant over a cationic exchenge resin which becomes "loaded" and is then dis-carded. Reagent which is regenerated by the cationic exchange resin is recirculated through the reactor system. Finally, the reagent may be removed from the system by passing the coolant through an anionic exchange resin and depositing the reagent thereon.
In the past, decontamination of nuclear reactors has been effected by circulating various reagents, in a concentra-tion of about 3-Z0%, through the equipment and then discharging the spent reagents and contaminants. Reagents such as oxalic acid (2-25 g/l), ammonium citrate (5-100 g/l) and EDTA (0.4-4 g/1) have been employed. Phosphoric acid and dilute dichromic acid have also been employed. Such methods all have the inherent disadvantage that heavy water coolant becomes contaminated, and use of a conventional decontamination reagent results in serious downgrading of the expensive primary heavy water coolant, and probable corrosion of parts of the e~uipment. In order to ~F
___ rm/~`
minimize downgrading of the D2O, the D2O would have to be replaced with H2O before decontamination with the relatively concentrated and corroSive conventional reagents took place. This is not only time consuming but could be hazardous since the workers are likely to be exposed to radiation. As the radioactive wastes from the conventional treatments are in liquid form and large quantities are involved, disposal is very costly. Many of the disadvantages of the prior art were overcome by Motojima et al in United States Patent 3,737,373, issued June 5, 1973, which describes a process in which deuterated 0.1% oxalic acid was added to the D2O reactor coolant to dissolve the contaminants.
The dissolved radioactive contaminants were removed from the coolant flow by irradiation of the oxalic acid causing decomposition thereof and precipitation of the dissolved metals and contaminants.
~he contaminants can then be recovered by simple filtration and/or ion exchange techniques. The Motojima method, as per the aforesaid United States Patent, is limited to the use of deuterated oxalic acid which is destroyed during the process, so that additional acid must be added to continue decontamination. The use of oxalic acid may be disadvantageous owing to the formation of insoluble oxalates. Furthermore, the method is discontinuous in that the reactor must be cycled between cool, subcritical conditions and hot, critical conditions.
An object of the present invention is to provide a simple process for continuously decontaminating shutdown heavy water moderated and cooled reactors which minimizes corrosion, down-grading of the expensive heavy water, the volume of radioactive waste for disposal, and decontamination time.
Another object of this invention is to provide a novel composition of matter for use as a decontaminating reagent in the process of the present invention.
Thus, by one aspect of the present invention there is provided a method of decontaminating a nuclear reactor coolant system which comprises in;ecting an acidic chemical reagent into circulating coolant in said system to thereby form a dilute reagent solution, circulating said solution to dissolve contam-inated deposits therein, passing said dilute solution through a cationic exchange resin to thereby collect dissolved cations and radionuclides thereon and regenerate said chemical reagent solution, recycling said regenerated solution through said system, and subsequently passing said coolant solution through an anionic exchange resin to remove said reagent from said coolant system.
In another aspect of this invention there is provided a decontaminating reagent for use in the decontamination of nuclear reactor systems comprising a binary or ternary mixture of (a) at least one of sulfuric acid, sulfamic acid, dithionous acid, phosphoric acid and hydroxylamine, (b) at least one of ethylene-diaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), and (c) 0 - 50% citric acid. -A particularly preferred reagent for use in the decontamin-ation method comprises a mixture of ethylenediaminetetraacetic acid (EDTA), oxalic acid and citric acid.
In the process of the present invention it has been found that the reagent may be used in concentrations as low as 0.01~
and consequently the risk of corrosion of reactor components is considerably reduced. As the reagent is regenerated on the cationic resin exchange bed the overall cost of some reagents j?l _3_ ., ~
106Z5~0 which are relatively costly is reduced considerably. On the other hand, the cationic exchange resin is sufficiently inexpensive to permit discardal following loadiny with radioactive contaminants.
As the radioactive contaminant waste is in a low bulk solid form, disposal of the radionuclides is simplified.
Although decontamination factors are smaller than can be achieved with more aggressive conventional methods, the present process is inexpensive, simple to operate, relatively non-corrosive and generates much less waste than the conventional . 10 chemical cleaning methods. These features permit it to be used more frequently than conventional methods, so that radiation fields need never be allowed to become very high, with a conse-quent saving in man-rem exposure.
As the reagents are added directly to the coolant to provide a low concentration of reagent, it is merely necessary to shut down the reactor before effecting the decontamination process. It is not necessary to defuel the reactor nor is it necessary to drain the system. Because the decontaminating reagent is regenerated the process can be continued as long as activity is still being removed and because the reagents are dilute, the formation of gases from corrosion and resin degradation is slight.
Many reagent compositions have been found to be effective to dissolve contaminants from nuclear reactor systems and amenable to removal by ion exchange resin. Most such comp-ositions are based on mixtures of organic acids, such as oxalic and citric acids, with or without complexing or chelating agents such as EDTA, HEDTA and NTA. The precise mechanism of dissolution is not entirely understood but it is believed to include diss-olution as well as complexing of the contaminants. Use of oxalic jC~
~06Z590 acid alone is believed not to be entirely beneficial due to the possibility of the formation of insoluble oxalates. It has also been found that inorganic acids such as sulphuric acid are effective in combination with either complexing agents or oxi-dizing agents, depending upon the type of contamination under consideration. Thus, the reagent composition is generally a mixture containing at least two compounds selected from the group consisting of sulphuric acid, oxalic acid, acetic acid, thioglycolic acid, citric acid, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), hydroxylamine, hydrazine, dithionous acid, sulphurous acid, sulfamic acid, phosphoric acid and ethylene diamine, with at least one acidic compound being present. Pref~rably a reducing agent component is included.
One suitable reagent composition which has been proven effective in large scale testing is that sold under the trade mark NUTEK
L-106 by Nuclear Technology Corporation, of Connecticut, U.S.A., which is a modified polyfunctional organic reagent comprising about 40% EDTA, 22% oxalic acid and 20~ citric acid, the balance being water of hydration and impurities (all percentages in this specification are by weight unless otherwise indicated).
Other particularly suitable compositions include:
(a) 20-50% citric acid 10-50% ethylenediaminetetraacetic acid (EDTA) 20-50% hydroxylamine (b) 0-50% citricacid 10-50% NTA or EDTA
20-50% oxalic acid or hydroxylamine (c) 25-75% ethylenediaminetetraacetic acid (EDTA) 25-75% hydroxylamine rm/'~
~06Z590 (d) 20-40~ sulphuric acid 60-80% hydroxylamine (e) 20-70% sulfamic acid 30-80% ethylenediaminetetraacetic acid (EDTA) (f) chromic acid All of the above reagents or mixtures can be regener-ated by the use of suitable cationic exchange resins to remove the contaminants, and the reagents or mixtures themselves can be removed from the reactor systems by anionic exchange resins ; 10 when the level of activity of the coolant system has been reduced sufficiently to warrent such removal. Suitable anionic and -cationic resins include POWDE ~ anionic resins and AMBERLIT
XE-78 anionic resin and POWDE ~ cationic resins and AMBERLIT
XE-77 cationic resin. Other cationic and anionic resins are also operative.
It s desirable that the exchange resins be in forms which tend to restore the original cooIant composition. In the case of heavy water moderated and cooled reactors a preferred cationic resin is in D form, and a preferred anionic resin in OD form.
The method of the present invention will be described in more detail hereinafter by particular reference to the Examples and to the accompanying drawings in which:
Fig. 1 is a simplified flow diagram of the path of the decontaminating reagent through a CANDU-BLW (Canadian Deuterium Uranium-Boiling Light Water) reactor described in Example l;
Fig. 2 is a graph showing 60Co in South HTS (Heat Trans-port System) against time;
;
rm/~
Fiq. 3 is a graph showing 54Mn in South HTS against time;
F~g. 4 is a graph illustrating removal of crud from South HTS; and Fig. 5 is a graph illustrating corrosion of steel during decontamination of North HTS.
Example 1 A shutdown of a CANDU-BLW reactor gave the opportunity to install additional in-cbre flux detectors and control ab-sorbers and anchor some steam-separator cyclones which had become loose in the steam drums. Designers estimated that installation of the in-core equipment would require 125-400 man-hours of work inside the reactor outlet feeder cabinet where the radiation field was about 1 Ry/h in July. Modifications in the steam drums, where the radiation field was about 3 Ry/h, would require 20-120 man-hours. Decontamination of the steam drums and outlet feeders was recommended to reduce the ex-posure of personnel to radiation.
The heat transport system (HTS) was predominantly carbon steel, and radiation fields resulted from 54Mn and 60Co contamination in deposits consisting of approximately equal proportions of Fe2O3 and Fe3O4. The distribution of corrosion products and contaminants in the HTS at the time of the reactor shutdown was estimated to be as follows:
Crud 60co 54Mn 59Fe kg Ci Ci Ci .
Reactor Core 24-44 30-50 60-120 80-350 Steam drums 13 2 0.4 0.3 Outlet feeders 1.5 0.2 - -106;~590 Chemical decontamination of the reactor by the method of the present invention using 0.1~ Nutek~ L-106 was the method chosen for reducing radiation fields. Experiments using contam-inated materials from the reactor indicated that L-106 could lower fields by factors of up to 13 without causing excessive corrosion or damage to components of the system.
The two loops of the HTS, north and south, each received two separate decontaminations. Each decontamination was applied in two stages, designed to minimize the spread of radioactive material from the reactor core to the steam drums. Figure l is a Simplified diagram of the path of L-106 solutions through the HTS during the decontaminations. Each of the four decontam-inations of the HTS was done with the following sequential steps:
a) removal of impurities from the HTS using the ~urification system, b) heating the water in the loop to about 85C with the main pumps 3 followed by drain-down of the water in the elevated steam drum, c) injecting L-106 into the reactor inlet header and circulating it through the reactor core, feeders, and purification system using the shutdown cooling pumps 4 and the purification booster pump 5. The ion exchange units 6 were coated with 9/l cation/
anion H-form Powde ~ resin to remove dissolved activity and regenerated the L-106, d) refilling the steam drum with water (end of phase 1) and circulating L-106 through the whole HTS loop and purification system (9/1 c/a resin) using the main pumps 3.
e) removal of L-106 from the loop using 3/7 cation/anion H-form Powde ~ resin (end of phase 2).
jc~
Decontamination of the South HTS
The south HTS was decontaminated on October 2 and 4 by injecting 5~ kg of L-106 into valve 9 each time and following the procedure outlined above, except that during the second decontamination an additional 34 kg of ~-106 was injected during step (d) (phase 2). For L-106 regeneration, the Powde ~ units were coated with 3 kg/m2 of 9/1 cation/anion resin and were operated at 20 to 30 ~s for 40 min or longer. For the most part, one Powdex~ unit at a time was used while the other was being recoated. Decontaminating solution from the reaction inlet header (sample post 301~ and from the Powdex~ effluent (post 302 - or 304) was sampled about every 15 minutes and analysed to follow the progress of the decontamination.
Phase 2 of the decontamination (flow to the steam drums) was started after several cation-rich Powdex~ units were used to lower the concen'ration of activity in the HTS to about 20% of its peak value observed just after L-106 injection. After the regen-erations were stopped, 2 Powdex~3 units,coated with 3 kg/m2 of 3/7 cation/anion resin operated at about 20Q/s were used to remove the L-106 and residual radio-elements from the HTS. Phase 1 lasted for about 10 hours, and Phase 2 for about 7 hours for each decontam-ination.
Decontamination of the North HTS
Decontaminations of the north HTS were done on October 23 and 26 by injecting 57 kg of L-106 into the reactor inlet header on each date. The general procedure outlined above was followed for both decontaminations. The first Powdex~ unit used for regeneration on October 23 was coated with 3 kg/m2 9/1 (c/a) resin and operated ~c:
at 30Q/q for about 20 minutes. Thereafter, all L-106 regeneration in the north loop was done with the Powde ~ units coated with 1.5 kg/m2 of 9/1 (c/a) resin operated at a nominal 30Q/s for 20 minutes.
During the regenerations, samples of L-106 solution from the reactor inlet header (post 305) and Powdex~ outlet (302 and 304) were sampled at about 5 minute intervals.
Results and DisCUSSion _ General Partial results of chemical and radiochemical analyses for 60 Co and 54 Mn, radiation surveys, and corrosion coupon examinations are given in Figures 2 and 3 and illustrate the effects of the Powdex~ purification system on the chemistry of the decontaminating solution.
Adding L-106 to the HTS immediately released some of the deposited iron and radio-elements to the water. The amount of material liberated immediately by a given quantity of L-106 appeared to decrease with successive injections of the chemicals. Injecting about 50 kg of L-106 into either HTS loop at 80C caused the release of 7 to 8 Ci 60 Co (160 ~ci/l) after the first injec:ion and 4 to 5 Ci 60 Co after the second injection. 37 kg (0.05~)of L-106 used for a third injection into the south HTS liberated only about 1 Ci 60 Co on October 5. The contaminated surfaces also released 1 to 5 Ci 54 Mn (20 to 100 ~Ci/l), 4 to 6 mg crud/kg and 200 mg Fe (total) /kg shortly after each of the first two L-106 injections into either loop. Starting the main HTS pumps and circulating L-106 solution through the steam drums caused the release of an additional 1.4 to 3.5 Ci 60 Co (20 to 50 ~Ci/1),0.6 to 3.2 Ci 54 Mn, and up to 100 mg Fe/kg.
~c:?,~
Removal of Impurities from the HTS
The quantities of radio-elements and Fe removed from the HTS were calculated and the results appear in Table 1. The values given in Table 1 probably represent the minimum quantities - removed from the HTS, since sampling was not frequent enough to permit accurate determination of the quantities of iron and radioactivity removed during short-lived crud bursts.
The decontaminant removed most of the radioactive deposits from the fuel. At least 70% of the 60 Co (36.8 Ci) and 35~ of the 54 Mn (22.6 Ci) were removed from the estimated 30-50 Ci 60Co and 30-60 Ci 54 Mn resident on the fuel.
Figures 2 and 3 illustrate the effect of the purification system on radio-elements in the HTS, and Figure 4 shows that the Powdex~ units retained at least 1/3 of the crud (>0.45~ ) which entered them. The resin removed up to 3/4 of the particles which were in the purification feed immediately after the pumps were started on October 23, indicating that hydraulic shock dislodged larger particles than did the L-106 alone.
QUANTITIES OF RADIO-ELEMENTS AND IRON REMOVED FROM THE HTS
SOUTH HTS NORTH HTS
Oct. 2 Oct. 4 Sum Oct. 23 Oct. 26 Sum TOTAL
-60 Co Ci 10.1 0.1 10.2 14.1 12.5 26.6 36.8 54Mn Ci 2.4 1.8 4.2 7.6 10.8 18.4 22.6 65 Zn Ci 2.5 - 2.5* 3.4 3.1 6.5 9.0 Fe kg 10.5* 15 25.5 27.4 8.4 35.8 61.3 * minimum quantity jc:-\2., Table 2 shows operating conditions for Powdex~) units.
CONDITIONS FOR 9/1 CATION/ANION POWDEX~
RESIN MIX OPERATED IN 0.03-0.1% NUTEK~ L-106 AT 80C
- Powdex~ Resin Coating Q/sw Q/(s.m ) Loading2 kg/m *
Normal for south HTS 20 to 30 .47 to .85 3 Experiment .05 .75 3 1st coat for north HTS 30 .75 3 Normal for north ~ITS 30 .75 1.5 *each Powdex~) unit has 40.3 m2 of area for resin support The benefits of L-106 regeneration are estimated from Table 3, which compares the totals of nuclides removed from the HTS with the quantities which might have been removed had no regeneration been made. The latter quantities were calculated from the concentration increases which resulted from the injection of L-106 and the pump starts.
CURIES OF R~DIOELEMENTS REMOVED BY REGENERATION
Oct. 2 1 Oct. 23 Oct. ;~6 60Co 54r~ 60Co 54Mn 60Co ~
Total removed from HTS, A 10.1 2.4 14.1 7.6 12.6 10.8 Amt. released by injection of chemicals 7.4 1.0 7.8 4.8 4.3 2.6 Quantity loosened by pump start 1.7 0.6 1.4 0.8 3.5 3.2 Amt. removable without regeneration, B 9.1 1.6 9.2 5.6 7.8 5.8 Amt. removed by regeneration, C 1.0 0.8 4.9 2.0 4.9 5.0 (B+c)/B 1.11 1.5 1.53 1.36 1.62 1.86 Regeneration rate, kg NTL-106/min* 0.16 0.32 0.43 * regeneratlon rate - ((kg L-106 in HTS). (purification rate, kg/m).
(no. regeneratlon Powdex coats used). (20 min.))/
((60,000 kg HTS vol.). (duration of decontam.,min.)) j c ~
There appears to be a positive correlation between the rate of L-106 regeneration and the extra quantity of radio-activity removed by regeneration. No correlation exists for the Mn data alone, possibly because the dissolution rate of Mn increases with decontamination time.
The decontaminations were terminated by using resin coats of either 1/2 or 3/7 cation/anion Powde ~ resins, which removed at least 75% of all impurities entering the purification system.
Corrosion The corrosion of HTS materials during the decontam-ination was monitored with coupons and with a model L-3 Corrosomete ~ -manufactured by the Magno Corp., Santa Fe Springs, California. Both pre-oxidized and newly pickled coupons were exposed to the decontaminating solution in autoclaves in:
1) a south HTS outlet feeder,
More particularly the invention relates to the injection of a relatively small quantity of a reagent composition directly in-to the circulating reactor coolant - either water (H2O) or heavy water (D2O) - so that the coolant acts as a carrier for the reagent in dilute solution therein. The reagent dissolves the active corrosion products containing radioactive contamina-tion, and these are removed by passing the coolant over a cationic exchenge resin which becomes "loaded" and is then dis-carded. Reagent which is regenerated by the cationic exchange resin is recirculated through the reactor system. Finally, the reagent may be removed from the system by passing the coolant through an anionic exchange resin and depositing the reagent thereon.
In the past, decontamination of nuclear reactors has been effected by circulating various reagents, in a concentra-tion of about 3-Z0%, through the equipment and then discharging the spent reagents and contaminants. Reagents such as oxalic acid (2-25 g/l), ammonium citrate (5-100 g/l) and EDTA (0.4-4 g/1) have been employed. Phosphoric acid and dilute dichromic acid have also been employed. Such methods all have the inherent disadvantage that heavy water coolant becomes contaminated, and use of a conventional decontamination reagent results in serious downgrading of the expensive primary heavy water coolant, and probable corrosion of parts of the e~uipment. In order to ~F
___ rm/~`
minimize downgrading of the D2O, the D2O would have to be replaced with H2O before decontamination with the relatively concentrated and corroSive conventional reagents took place. This is not only time consuming but could be hazardous since the workers are likely to be exposed to radiation. As the radioactive wastes from the conventional treatments are in liquid form and large quantities are involved, disposal is very costly. Many of the disadvantages of the prior art were overcome by Motojima et al in United States Patent 3,737,373, issued June 5, 1973, which describes a process in which deuterated 0.1% oxalic acid was added to the D2O reactor coolant to dissolve the contaminants.
The dissolved radioactive contaminants were removed from the coolant flow by irradiation of the oxalic acid causing decomposition thereof and precipitation of the dissolved metals and contaminants.
~he contaminants can then be recovered by simple filtration and/or ion exchange techniques. The Motojima method, as per the aforesaid United States Patent, is limited to the use of deuterated oxalic acid which is destroyed during the process, so that additional acid must be added to continue decontamination. The use of oxalic acid may be disadvantageous owing to the formation of insoluble oxalates. Furthermore, the method is discontinuous in that the reactor must be cycled between cool, subcritical conditions and hot, critical conditions.
An object of the present invention is to provide a simple process for continuously decontaminating shutdown heavy water moderated and cooled reactors which minimizes corrosion, down-grading of the expensive heavy water, the volume of radioactive waste for disposal, and decontamination time.
Another object of this invention is to provide a novel composition of matter for use as a decontaminating reagent in the process of the present invention.
Thus, by one aspect of the present invention there is provided a method of decontaminating a nuclear reactor coolant system which comprises in;ecting an acidic chemical reagent into circulating coolant in said system to thereby form a dilute reagent solution, circulating said solution to dissolve contam-inated deposits therein, passing said dilute solution through a cationic exchange resin to thereby collect dissolved cations and radionuclides thereon and regenerate said chemical reagent solution, recycling said regenerated solution through said system, and subsequently passing said coolant solution through an anionic exchange resin to remove said reagent from said coolant system.
In another aspect of this invention there is provided a decontaminating reagent for use in the decontamination of nuclear reactor systems comprising a binary or ternary mixture of (a) at least one of sulfuric acid, sulfamic acid, dithionous acid, phosphoric acid and hydroxylamine, (b) at least one of ethylene-diaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), and (c) 0 - 50% citric acid. -A particularly preferred reagent for use in the decontamin-ation method comprises a mixture of ethylenediaminetetraacetic acid (EDTA), oxalic acid and citric acid.
In the process of the present invention it has been found that the reagent may be used in concentrations as low as 0.01~
and consequently the risk of corrosion of reactor components is considerably reduced. As the reagent is regenerated on the cationic resin exchange bed the overall cost of some reagents j?l _3_ ., ~
106Z5~0 which are relatively costly is reduced considerably. On the other hand, the cationic exchange resin is sufficiently inexpensive to permit discardal following loadiny with radioactive contaminants.
As the radioactive contaminant waste is in a low bulk solid form, disposal of the radionuclides is simplified.
Although decontamination factors are smaller than can be achieved with more aggressive conventional methods, the present process is inexpensive, simple to operate, relatively non-corrosive and generates much less waste than the conventional . 10 chemical cleaning methods. These features permit it to be used more frequently than conventional methods, so that radiation fields need never be allowed to become very high, with a conse-quent saving in man-rem exposure.
As the reagents are added directly to the coolant to provide a low concentration of reagent, it is merely necessary to shut down the reactor before effecting the decontamination process. It is not necessary to defuel the reactor nor is it necessary to drain the system. Because the decontaminating reagent is regenerated the process can be continued as long as activity is still being removed and because the reagents are dilute, the formation of gases from corrosion and resin degradation is slight.
Many reagent compositions have been found to be effective to dissolve contaminants from nuclear reactor systems and amenable to removal by ion exchange resin. Most such comp-ositions are based on mixtures of organic acids, such as oxalic and citric acids, with or without complexing or chelating agents such as EDTA, HEDTA and NTA. The precise mechanism of dissolution is not entirely understood but it is believed to include diss-olution as well as complexing of the contaminants. Use of oxalic jC~
~06Z590 acid alone is believed not to be entirely beneficial due to the possibility of the formation of insoluble oxalates. It has also been found that inorganic acids such as sulphuric acid are effective in combination with either complexing agents or oxi-dizing agents, depending upon the type of contamination under consideration. Thus, the reagent composition is generally a mixture containing at least two compounds selected from the group consisting of sulphuric acid, oxalic acid, acetic acid, thioglycolic acid, citric acid, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), hydroxylamine, hydrazine, dithionous acid, sulphurous acid, sulfamic acid, phosphoric acid and ethylene diamine, with at least one acidic compound being present. Pref~rably a reducing agent component is included.
One suitable reagent composition which has been proven effective in large scale testing is that sold under the trade mark NUTEK
L-106 by Nuclear Technology Corporation, of Connecticut, U.S.A., which is a modified polyfunctional organic reagent comprising about 40% EDTA, 22% oxalic acid and 20~ citric acid, the balance being water of hydration and impurities (all percentages in this specification are by weight unless otherwise indicated).
Other particularly suitable compositions include:
(a) 20-50% citric acid 10-50% ethylenediaminetetraacetic acid (EDTA) 20-50% hydroxylamine (b) 0-50% citricacid 10-50% NTA or EDTA
20-50% oxalic acid or hydroxylamine (c) 25-75% ethylenediaminetetraacetic acid (EDTA) 25-75% hydroxylamine rm/'~
~06Z590 (d) 20-40~ sulphuric acid 60-80% hydroxylamine (e) 20-70% sulfamic acid 30-80% ethylenediaminetetraacetic acid (EDTA) (f) chromic acid All of the above reagents or mixtures can be regener-ated by the use of suitable cationic exchange resins to remove the contaminants, and the reagents or mixtures themselves can be removed from the reactor systems by anionic exchange resins ; 10 when the level of activity of the coolant system has been reduced sufficiently to warrent such removal. Suitable anionic and -cationic resins include POWDE ~ anionic resins and AMBERLIT
XE-78 anionic resin and POWDE ~ cationic resins and AMBERLIT
XE-77 cationic resin. Other cationic and anionic resins are also operative.
It s desirable that the exchange resins be in forms which tend to restore the original cooIant composition. In the case of heavy water moderated and cooled reactors a preferred cationic resin is in D form, and a preferred anionic resin in OD form.
The method of the present invention will be described in more detail hereinafter by particular reference to the Examples and to the accompanying drawings in which:
Fig. 1 is a simplified flow diagram of the path of the decontaminating reagent through a CANDU-BLW (Canadian Deuterium Uranium-Boiling Light Water) reactor described in Example l;
Fig. 2 is a graph showing 60Co in South HTS (Heat Trans-port System) against time;
;
rm/~
Fiq. 3 is a graph showing 54Mn in South HTS against time;
F~g. 4 is a graph illustrating removal of crud from South HTS; and Fig. 5 is a graph illustrating corrosion of steel during decontamination of North HTS.
Example 1 A shutdown of a CANDU-BLW reactor gave the opportunity to install additional in-cbre flux detectors and control ab-sorbers and anchor some steam-separator cyclones which had become loose in the steam drums. Designers estimated that installation of the in-core equipment would require 125-400 man-hours of work inside the reactor outlet feeder cabinet where the radiation field was about 1 Ry/h in July. Modifications in the steam drums, where the radiation field was about 3 Ry/h, would require 20-120 man-hours. Decontamination of the steam drums and outlet feeders was recommended to reduce the ex-posure of personnel to radiation.
The heat transport system (HTS) was predominantly carbon steel, and radiation fields resulted from 54Mn and 60Co contamination in deposits consisting of approximately equal proportions of Fe2O3 and Fe3O4. The distribution of corrosion products and contaminants in the HTS at the time of the reactor shutdown was estimated to be as follows:
Crud 60co 54Mn 59Fe kg Ci Ci Ci .
Reactor Core 24-44 30-50 60-120 80-350 Steam drums 13 2 0.4 0.3 Outlet feeders 1.5 0.2 - -106;~590 Chemical decontamination of the reactor by the method of the present invention using 0.1~ Nutek~ L-106 was the method chosen for reducing radiation fields. Experiments using contam-inated materials from the reactor indicated that L-106 could lower fields by factors of up to 13 without causing excessive corrosion or damage to components of the system.
The two loops of the HTS, north and south, each received two separate decontaminations. Each decontamination was applied in two stages, designed to minimize the spread of radioactive material from the reactor core to the steam drums. Figure l is a Simplified diagram of the path of L-106 solutions through the HTS during the decontaminations. Each of the four decontam-inations of the HTS was done with the following sequential steps:
a) removal of impurities from the HTS using the ~urification system, b) heating the water in the loop to about 85C with the main pumps 3 followed by drain-down of the water in the elevated steam drum, c) injecting L-106 into the reactor inlet header and circulating it through the reactor core, feeders, and purification system using the shutdown cooling pumps 4 and the purification booster pump 5. The ion exchange units 6 were coated with 9/l cation/
anion H-form Powde ~ resin to remove dissolved activity and regenerated the L-106, d) refilling the steam drum with water (end of phase 1) and circulating L-106 through the whole HTS loop and purification system (9/1 c/a resin) using the main pumps 3.
e) removal of L-106 from the loop using 3/7 cation/anion H-form Powde ~ resin (end of phase 2).
jc~
Decontamination of the South HTS
The south HTS was decontaminated on October 2 and 4 by injecting 5~ kg of L-106 into valve 9 each time and following the procedure outlined above, except that during the second decontamination an additional 34 kg of ~-106 was injected during step (d) (phase 2). For L-106 regeneration, the Powde ~ units were coated with 3 kg/m2 of 9/1 cation/anion resin and were operated at 20 to 30 ~s for 40 min or longer. For the most part, one Powdex~ unit at a time was used while the other was being recoated. Decontaminating solution from the reaction inlet header (sample post 301~ and from the Powdex~ effluent (post 302 - or 304) was sampled about every 15 minutes and analysed to follow the progress of the decontamination.
Phase 2 of the decontamination (flow to the steam drums) was started after several cation-rich Powdex~ units were used to lower the concen'ration of activity in the HTS to about 20% of its peak value observed just after L-106 injection. After the regen-erations were stopped, 2 Powdex~3 units,coated with 3 kg/m2 of 3/7 cation/anion resin operated at about 20Q/s were used to remove the L-106 and residual radio-elements from the HTS. Phase 1 lasted for about 10 hours, and Phase 2 for about 7 hours for each decontam-ination.
Decontamination of the North HTS
Decontaminations of the north HTS were done on October 23 and 26 by injecting 57 kg of L-106 into the reactor inlet header on each date. The general procedure outlined above was followed for both decontaminations. The first Powdex~ unit used for regeneration on October 23 was coated with 3 kg/m2 9/1 (c/a) resin and operated ~c:
at 30Q/q for about 20 minutes. Thereafter, all L-106 regeneration in the north loop was done with the Powde ~ units coated with 1.5 kg/m2 of 9/1 (c/a) resin operated at a nominal 30Q/s for 20 minutes.
During the regenerations, samples of L-106 solution from the reactor inlet header (post 305) and Powdex~ outlet (302 and 304) were sampled at about 5 minute intervals.
Results and DisCUSSion _ General Partial results of chemical and radiochemical analyses for 60 Co and 54 Mn, radiation surveys, and corrosion coupon examinations are given in Figures 2 and 3 and illustrate the effects of the Powdex~ purification system on the chemistry of the decontaminating solution.
Adding L-106 to the HTS immediately released some of the deposited iron and radio-elements to the water. The amount of material liberated immediately by a given quantity of L-106 appeared to decrease with successive injections of the chemicals. Injecting about 50 kg of L-106 into either HTS loop at 80C caused the release of 7 to 8 Ci 60 Co (160 ~ci/l) after the first injec:ion and 4 to 5 Ci 60 Co after the second injection. 37 kg (0.05~)of L-106 used for a third injection into the south HTS liberated only about 1 Ci 60 Co on October 5. The contaminated surfaces also released 1 to 5 Ci 54 Mn (20 to 100 ~Ci/l), 4 to 6 mg crud/kg and 200 mg Fe (total) /kg shortly after each of the first two L-106 injections into either loop. Starting the main HTS pumps and circulating L-106 solution through the steam drums caused the release of an additional 1.4 to 3.5 Ci 60 Co (20 to 50 ~Ci/1),0.6 to 3.2 Ci 54 Mn, and up to 100 mg Fe/kg.
~c:?,~
Removal of Impurities from the HTS
The quantities of radio-elements and Fe removed from the HTS were calculated and the results appear in Table 1. The values given in Table 1 probably represent the minimum quantities - removed from the HTS, since sampling was not frequent enough to permit accurate determination of the quantities of iron and radioactivity removed during short-lived crud bursts.
The decontaminant removed most of the radioactive deposits from the fuel. At least 70% of the 60 Co (36.8 Ci) and 35~ of the 54 Mn (22.6 Ci) were removed from the estimated 30-50 Ci 60Co and 30-60 Ci 54 Mn resident on the fuel.
Figures 2 and 3 illustrate the effect of the purification system on radio-elements in the HTS, and Figure 4 shows that the Powdex~ units retained at least 1/3 of the crud (>0.45~ ) which entered them. The resin removed up to 3/4 of the particles which were in the purification feed immediately after the pumps were started on October 23, indicating that hydraulic shock dislodged larger particles than did the L-106 alone.
QUANTITIES OF RADIO-ELEMENTS AND IRON REMOVED FROM THE HTS
SOUTH HTS NORTH HTS
Oct. 2 Oct. 4 Sum Oct. 23 Oct. 26 Sum TOTAL
-60 Co Ci 10.1 0.1 10.2 14.1 12.5 26.6 36.8 54Mn Ci 2.4 1.8 4.2 7.6 10.8 18.4 22.6 65 Zn Ci 2.5 - 2.5* 3.4 3.1 6.5 9.0 Fe kg 10.5* 15 25.5 27.4 8.4 35.8 61.3 * minimum quantity jc:-\2., Table 2 shows operating conditions for Powdex~) units.
CONDITIONS FOR 9/1 CATION/ANION POWDEX~
RESIN MIX OPERATED IN 0.03-0.1% NUTEK~ L-106 AT 80C
- Powdex~ Resin Coating Q/sw Q/(s.m ) Loading2 kg/m *
Normal for south HTS 20 to 30 .47 to .85 3 Experiment .05 .75 3 1st coat for north HTS 30 .75 3 Normal for north ~ITS 30 .75 1.5 *each Powdex~) unit has 40.3 m2 of area for resin support The benefits of L-106 regeneration are estimated from Table 3, which compares the totals of nuclides removed from the HTS with the quantities which might have been removed had no regeneration been made. The latter quantities were calculated from the concentration increases which resulted from the injection of L-106 and the pump starts.
CURIES OF R~DIOELEMENTS REMOVED BY REGENERATION
Oct. 2 1 Oct. 23 Oct. ;~6 60Co 54r~ 60Co 54Mn 60Co ~
Total removed from HTS, A 10.1 2.4 14.1 7.6 12.6 10.8 Amt. released by injection of chemicals 7.4 1.0 7.8 4.8 4.3 2.6 Quantity loosened by pump start 1.7 0.6 1.4 0.8 3.5 3.2 Amt. removable without regeneration, B 9.1 1.6 9.2 5.6 7.8 5.8 Amt. removed by regeneration, C 1.0 0.8 4.9 2.0 4.9 5.0 (B+c)/B 1.11 1.5 1.53 1.36 1.62 1.86 Regeneration rate, kg NTL-106/min* 0.16 0.32 0.43 * regeneratlon rate - ((kg L-106 in HTS). (purification rate, kg/m).
(no. regeneratlon Powdex coats used). (20 min.))/
((60,000 kg HTS vol.). (duration of decontam.,min.)) j c ~
There appears to be a positive correlation between the rate of L-106 regeneration and the extra quantity of radio-activity removed by regeneration. No correlation exists for the Mn data alone, possibly because the dissolution rate of Mn increases with decontamination time.
The decontaminations were terminated by using resin coats of either 1/2 or 3/7 cation/anion Powde ~ resins, which removed at least 75% of all impurities entering the purification system.
Corrosion The corrosion of HTS materials during the decontam-ination was monitored with coupons and with a model L-3 Corrosomete ~ -manufactured by the Magno Corp., Santa Fe Springs, California. Both pre-oxidized and newly pickled coupons were exposed to the decontaminating solution in autoclaves in:
1) a south HTS outlet feeder,
2) the inlet to the purification system, and
3) the outlet from the Powdex~.
The dry coupons were weighed before and after the decontamination, after loose deposit was brushed away, and again after adherent deposit was removed with Clarke's solution. The average loss of thickness (uniform penetration) of each coupon was calculated from the weight of metal lost. The Corrosomete ~, indicated differential corrosion rates by changes in electrical resistance through corroding metal "probes". The Corrosomete ~ was located in the HTS shutdown cooling circuit and was fed from the outlet of the shutdown cooling pump 7. Table 4 summari~es the information obtained from the coupons, and Figure 5 presents the Corrosometer~
results for October 23-24.
j c ~
.
.
CORROSION OF COUPO~S DETER~IINED AFTER t~ASHING
SOUM HTS NO~ TS
Auto- Oct. 2 C3ct. 4 Oct.2 & 4 Oct. 23 6 26 ~ clave l~m ~m/dl~m llm/d llmllm/d llm l~m/d Powdex ~ Inlet M~ld steel " 2.7 4.14.9 13.47~6 7.79.2 35.3 " " 2.7 4.25.1 14.1 to to*8.6 32.9 - 5.514.98.2 8.28.0 30.6 403--SS " 0.120.18 ------------------ ------ -- --410--SS 0.010.01 ------------------ ------ ------ ------Powde~ Outlet 3 Mild steel " 8.212.7 2.36.410.1 10.317.3 66.4 " " 7.712.0 2.46.7 to to*16.1 61.8 " " - --- 2.57.010.6 10.815.1 58.0 Outlet Feeder Mild steel " 7.8 5.6 " " 7.7 5.6 " . " 7.8 5.6 ~ " 7.0 5.1 " " 5.6 4.0 " " _7.6 5.4 410-SS " 9.8 7.0 ~ " g.O 6.5 " " 9.0 6.5 2 1/4 Cr, 1 ~lo " 6.7 4.8 " " 6.4 4.6 .
~Unlform pcnctrntion assumcd *Rfltc bflscd on rnn~c of pcnctrntlon in (0.646 ~ 0.365)d of flow throu~h autoclnvcs 2 and 3 on Oct. 2 and 4.
rm/_lc TEST RESULTS
The decontamination lowered radiation fields on most HTS equipment and saved radiation exposure during subsequent maintenance.
- Regeneration of the L-106 increased the removal of 60 Co by about 60%. The L-106 reacted rapidly with 1 Fe3O4/
1 Fe2O3 corrosion products and continuous regeneration was essential for efficient decontamination. Corrosion of carbon steel was greatest in the purification outlet (17.6ym, 67.6 ym/d), but the average uniform penetration for all carbon steel surfaces was 3.6 ym. Materials other than carbon steel were unaffected.
Removal of most of the fuel deposits should significantly lower the rate at which radiation fields increase in the future.
The following examples illustrate bench scale tests . . .
showing the efficacy of alternative reagent compositions in the practice of the present invention.
.
In a series of tests in autoclaves, the decontamination potential of ~ilute solutions of each of ethylenediaminetetraacetic acid, sulfurous acid, sulfuric acid, and phosphoric acids was measured for the removal of 60 Co from oxide on Zircaloy- ~, carbon steel, Inconel-600~, and Monel 400~. Decontamination factors for these alloys when treated by the different solutions at tempera-tures ranging between 50 to 150C were:
Zircaloy-4~ 1.2 - 25 Carbon Steel 2 - 100 Inconel-600~ 1.3 - 4 Monel-400~ 1.2 - 6 jc:~ ~
.
An in-pile recirculating loop has been decontaminated at different times by dilute phosphoric acid; by ethylenediamine-tetraacetic acid plus oxalic acid and citric acid; by ethylene-diaminetetraacetic acid plus hydroxylamine; by sulfuric acid plus hydroxylamine; and by sulfuric acid plus oxalic acid. In all the decontaminations, the active ingredients were regenera-ted on cation resins. The loop is constructed of carbon steel and stainless steel.
Decontamination factors for irradiated corrosion products ranged between 1.5 - 3.5 for the two steels.
~0 rm/J~'
The dry coupons were weighed before and after the decontamination, after loose deposit was brushed away, and again after adherent deposit was removed with Clarke's solution. The average loss of thickness (uniform penetration) of each coupon was calculated from the weight of metal lost. The Corrosomete ~, indicated differential corrosion rates by changes in electrical resistance through corroding metal "probes". The Corrosomete ~ was located in the HTS shutdown cooling circuit and was fed from the outlet of the shutdown cooling pump 7. Table 4 summari~es the information obtained from the coupons, and Figure 5 presents the Corrosometer~
results for October 23-24.
j c ~
.
.
CORROSION OF COUPO~S DETER~IINED AFTER t~ASHING
SOUM HTS NO~ TS
Auto- Oct. 2 C3ct. 4 Oct.2 & 4 Oct. 23 6 26 ~ clave l~m ~m/dl~m llm/d llmllm/d llm l~m/d Powdex ~ Inlet M~ld steel " 2.7 4.14.9 13.47~6 7.79.2 35.3 " " 2.7 4.25.1 14.1 to to*8.6 32.9 - 5.514.98.2 8.28.0 30.6 403--SS " 0.120.18 ------------------ ------ -- --410--SS 0.010.01 ------------------ ------ ------ ------Powde~ Outlet 3 Mild steel " 8.212.7 2.36.410.1 10.317.3 66.4 " " 7.712.0 2.46.7 to to*16.1 61.8 " " - --- 2.57.010.6 10.815.1 58.0 Outlet Feeder Mild steel " 7.8 5.6 " " 7.7 5.6 " . " 7.8 5.6 ~ " 7.0 5.1 " " 5.6 4.0 " " _7.6 5.4 410-SS " 9.8 7.0 ~ " g.O 6.5 " " 9.0 6.5 2 1/4 Cr, 1 ~lo " 6.7 4.8 " " 6.4 4.6 .
~Unlform pcnctrntion assumcd *Rfltc bflscd on rnn~c of pcnctrntlon in (0.646 ~ 0.365)d of flow throu~h autoclnvcs 2 and 3 on Oct. 2 and 4.
rm/_lc TEST RESULTS
The decontamination lowered radiation fields on most HTS equipment and saved radiation exposure during subsequent maintenance.
- Regeneration of the L-106 increased the removal of 60 Co by about 60%. The L-106 reacted rapidly with 1 Fe3O4/
1 Fe2O3 corrosion products and continuous regeneration was essential for efficient decontamination. Corrosion of carbon steel was greatest in the purification outlet (17.6ym, 67.6 ym/d), but the average uniform penetration for all carbon steel surfaces was 3.6 ym. Materials other than carbon steel were unaffected.
Removal of most of the fuel deposits should significantly lower the rate at which radiation fields increase in the future.
The following examples illustrate bench scale tests . . .
showing the efficacy of alternative reagent compositions in the practice of the present invention.
.
In a series of tests in autoclaves, the decontamination potential of ~ilute solutions of each of ethylenediaminetetraacetic acid, sulfurous acid, sulfuric acid, and phosphoric acids was measured for the removal of 60 Co from oxide on Zircaloy- ~, carbon steel, Inconel-600~, and Monel 400~. Decontamination factors for these alloys when treated by the different solutions at tempera-tures ranging between 50 to 150C were:
Zircaloy-4~ 1.2 - 25 Carbon Steel 2 - 100 Inconel-600~ 1.3 - 4 Monel-400~ 1.2 - 6 jc:~ ~
.
An in-pile recirculating loop has been decontaminated at different times by dilute phosphoric acid; by ethylenediamine-tetraacetic acid plus oxalic acid and citric acid; by ethylene-diaminetetraacetic acid plus hydroxylamine; by sulfuric acid plus hydroxylamine; and by sulfuric acid plus oxalic acid. In all the decontaminations, the active ingredients were regenera-ted on cation resins. The loop is constructed of carbon steel and stainless steel.
Decontamination factors for irradiated corrosion products ranged between 1.5 - 3.5 for the two steels.
~0 rm/J~'
Claims (15)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of decontaminating a nuclear reactor coolant system which comprises injecting an acidic chemical reagent into circulating coolant in said system to thereby form a dilute reagent solution, circulating said solution to dissolve contaminated deposits therein, passing said dilute solution through a cationic exchange resin to thereby collect dissolved cations and radionuclides thereon and regenerate said chemical reagent solution, recycling said regenerated solution through said system, and subsequently passing said coolant solution through an anionic exchange resin to remove said reagent from said coolant system.
2. A method as claimed in claim 1 wherein said reactor is a heavy water moderated and cooled reactor.
3. A method as claimed in claim 2 wherein said chemical reagent comprises a mixture containing at least two compounds selected from the group consisting of sulphuric acid, oxalic acid, acetic acid, thioglycolic acid, citric acid, ethylene-diaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), hydroxylamine, hydrazine, dithionous acid, sulphurous acid, sulfamic acid, phosphoric acid and ethylene diamine, with at least one acidic compound being present.
4. A method as claimed in claim 3 wherein said reagent comprises ethylenediaminetetraacetic acid (EDTA), oxalic acid and citric acid.
5. A method as claimed in Claim 3 wherein said reagent comprises 20 - 70% sulfamic acid and 30 - 80% ethylenediamine-tetraacetic acid (EDTA).
6. A method as claimed in Claim 3 wherein said reagent comprises 10 - 50% ethylenediaminetetraacetic acid (EDTA) or nitrilotriacetic acid (NTA). 20 - 50% hydroxylamine and 0 - 50%
citric acid.
citric acid.
7. A method as claimed in Claim 3 wherein said reagent comprises 25 - 75% ethylenediaminetetraacetic acid (EDTA) and 25 - 75% hydroxylamine.
8. A method as in Claims 1, 2 and 3 wherein the resins are in the forms tending to restore the original coolant composition.
9. A method as in Claims 2 and 3 wherein said cationic resin is in D+ form, and the anionic resin is in the OD- form.
10. A method as in Claims 1, 2 and 3 wherein said reagent comprises a reducing agent.
11. A decontaminating reagent for use in the decontamination of nuclear reactor systems comprising a binary or ternary mixture of (a) at least one of sulfuric acid, sulfamic acid, dithionous acid, phosphoric acid and hydroxylamine, (b) at least one of ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), and (c) 0 - 50% citric acid.
12. A decontaminating reagent as in Claim 11 including citric acid.
13. A decontaminating reagent for use in decontaminating nuclear reactor systems as claimed in Claim 11 comprising 20 - 70% sulfamic acid and 30 - 80% ethylenediaminetetraacetic acid (EDTA).
14. A decontaminating reagent as claimed in Claim 11 or Claim 12 comprising 10 - 50% ethylenediaminetetraacetic acid (EDTA) or nitrilotriacetic acid (NTA), 20 - 50% hydroxylamine and 0 - 50% citric acid.
15. A decontaminating reagent as claimed in Claim 11 comprising 25 - 75% ethylenediaminetetraacetic acid (EDTA) and 25 - 75% hydroxylamine.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA244,084A CA1062590A (en) | 1976-01-22 | 1976-01-22 | Reactor decontamination process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA244,084A CA1062590A (en) | 1976-01-22 | 1976-01-22 | Reactor decontamination process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1062590A true CA1062590A (en) | 1979-09-18 |
Family
ID=4105036
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA244,084A Expired CA1062590A (en) | 1976-01-22 | 1976-01-22 | Reactor decontamination process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1062590A (en) |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2471655A1 (en) * | 1979-12-10 | 1981-06-19 | Ca Atomic Energy Ltd | REAGENT AND METHOD FOR DECONTAMINATION OF RADIOACTIVE SYSTEMS |
| EP0075882A2 (en) * | 1981-09-25 | 1983-04-06 | Hitachi, Ltd. | Process for regenerating cleaning fluid |
| EP0090512A1 (en) * | 1982-03-22 | 1983-10-05 | London Nuclear Limited | Process for treatment of oxide films prior to chemical cleaning |
| FR2547450A1 (en) * | 1983-06-07 | 1984-12-14 | Westinghouse Electric Corp | METHOD AND APPARATUS FOR IMPROVEMENT IN OR WITH RESPECT TO DECONTAMINATION OF METAL SURFACES IN NUCLEAR POWER PLANT REACTORS AND OXIDIZING SOLUTION USED THEREFOR |
| US4512921A (en) * | 1980-06-06 | 1985-04-23 | The United States Of America As Represented By The United States Department Of Energy | Nuclear reactor cooling system decontamination reagent regeneration |
| US4729855A (en) * | 1985-11-29 | 1988-03-08 | Westinghouse Electric Corp. | Method of decontaminating radioactive metal surfaces |
| EP0273182A1 (en) * | 1986-12-01 | 1988-07-06 | Siemens Aktiengesellschaft | Method of cleaning a container |
| EP0355477A1 (en) * | 1988-08-12 | 1990-02-28 | Siemens Aktiengesellschaft | Process and device for decontaminating the primary system of a nuclear-power station |
| US4913849A (en) * | 1988-07-07 | 1990-04-03 | Aamir Husain | Process for pretreatment of chromium-rich oxide surfaces prior to decontamination |
| US5264041A (en) * | 1986-12-01 | 1993-11-23 | Siemens Aktiengesellschaft | Method for cleaning a vessel |
| WO2012009781A1 (en) * | 2010-07-21 | 2012-01-26 | Atomic Energy Of Canada Limited | Reactor decontamination process and reagent |
| WO2017076431A1 (en) * | 2015-11-03 | 2017-05-11 | Areva Gmbh | Method of decontaminating metal surfaces in a heavy water cooled and moderated nuclear reactor |
| CN113881513A (en) * | 2021-09-08 | 2022-01-04 | 中国辐射防护研究院 | Detergent for decontamination of nuclear power station reactor components and use method thereof |
-
1976
- 1976-01-22 CA CA244,084A patent/CA1062590A/en not_active Expired
Cited By (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2471655A1 (en) * | 1979-12-10 | 1981-06-19 | Ca Atomic Energy Ltd | REAGENT AND METHOD FOR DECONTAMINATION OF RADIOACTIVE SYSTEMS |
| US4512921A (en) * | 1980-06-06 | 1985-04-23 | The United States Of America As Represented By The United States Department Of Energy | Nuclear reactor cooling system decontamination reagent regeneration |
| EP0075882A2 (en) * | 1981-09-25 | 1983-04-06 | Hitachi, Ltd. | Process for regenerating cleaning fluid |
| EP0075882A3 (en) * | 1981-09-25 | 1983-08-31 | Hitachi, Ltd. | Process for regenerating cleaning fluid |
| EP0090512A1 (en) * | 1982-03-22 | 1983-10-05 | London Nuclear Limited | Process for treatment of oxide films prior to chemical cleaning |
| US4476047A (en) * | 1982-03-22 | 1984-10-09 | London Nuclear Limited | Process for treatment of oxide films prior to chemical cleaning |
| FR2547450A1 (en) * | 1983-06-07 | 1984-12-14 | Westinghouse Electric Corp | METHOD AND APPARATUS FOR IMPROVEMENT IN OR WITH RESPECT TO DECONTAMINATION OF METAL SURFACES IN NUCLEAR POWER PLANT REACTORS AND OXIDIZING SOLUTION USED THEREFOR |
| EP0138289A1 (en) * | 1983-06-07 | 1985-04-24 | Westinghouse Electric Corporation | Improvements in or relating to the decontamination of metal surfaces in nuclear power reactors |
| US4729855A (en) * | 1985-11-29 | 1988-03-08 | Westinghouse Electric Corp. | Method of decontaminating radioactive metal surfaces |
| EP0273182A1 (en) * | 1986-12-01 | 1988-07-06 | Siemens Aktiengesellschaft | Method of cleaning a container |
| US5264041A (en) * | 1986-12-01 | 1993-11-23 | Siemens Aktiengesellschaft | Method for cleaning a vessel |
| US5164015A (en) * | 1986-12-01 | 1992-11-17 | Siemens Aktiengesellschaft | Method for cleaning a vessel |
| US4913849A (en) * | 1988-07-07 | 1990-04-03 | Aamir Husain | Process for pretreatment of chromium-rich oxide surfaces prior to decontamination |
| EP0355477A1 (en) * | 1988-08-12 | 1990-02-28 | Siemens Aktiengesellschaft | Process and device for decontaminating the primary system of a nuclear-power station |
| WO2012009781A1 (en) * | 2010-07-21 | 2012-01-26 | Atomic Energy Of Canada Limited | Reactor decontamination process and reagent |
| CN103155047A (en) * | 2010-07-21 | 2013-06-12 | 加拿大原子能有限公司 | Reactor decontamination process and reagent |
| JP2013538336A (en) * | 2010-07-21 | 2013-10-10 | アトミック エナジー オブ カナダ リミテッド | Reactor decontamination method and decontamination agent |
| EP2596502A4 (en) * | 2010-07-21 | 2015-09-30 | Atomic Energy Of Canada Ltd | Reactor decontamination process and reagent |
| WO2017076431A1 (en) * | 2015-11-03 | 2017-05-11 | Areva Gmbh | Method of decontaminating metal surfaces in a heavy water cooled and moderated nuclear reactor |
| CN113881513A (en) * | 2021-09-08 | 2022-01-04 | 中国辐射防护研究院 | Detergent for decontamination of nuclear power station reactor components and use method thereof |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4512921A (en) | Nuclear reactor cooling system decontamination reagent regeneration | |
| CA1062590A (en) | Reactor decontamination process | |
| US3873362A (en) | Process for cleaning radioactively contaminated metal surfaces | |
| CA1224025A (en) | Decontamination of metal surfaces in nuclear power reactors | |
| JPS6158800B2 (en) | ||
| US20130251086A1 (en) | Reactor decontamination process and reagent | |
| US4476047A (en) | Process for treatment of oxide films prior to chemical cleaning | |
| US5245642A (en) | Method of controlling co-60 radiation contamination of structure surfaces of cooling water circuits of nuclear reactors | |
| WO2000078403A1 (en) | Method for the decontamination of metallic surfaces | |
| US5024805A (en) | Method for decontaminating a pressurized water nuclear reactor system | |
| CA1136398A (en) | Decontaminating reagents for radioactive systems | |
| CA1230806A (en) | Ceric acid decontamination of nuclear reactors | |
| US5724668A (en) | Method for decontamination of nuclear plant components | |
| EP3063771B1 (en) | Ambient temperature decontamination of nuclear power plant component surfaces containing radionuclides in a metal oxide | |
| US20040152940A1 (en) | Method of chemical decontamination | |
| CA1303948C (en) | Process for pretreatment of chromium-rich oxide surfaces prior to decontamination | |
| US5901368A (en) | Radiolysis-assisted decontamination process | |
| US11286569B2 (en) | Recontamination mitigation method by carbon steel passivation of nuclear systems and components | |
| Kaminski et al. | Metal surface decontamination using 1-hydroxyethane-1, 1-diphosphonic acid | |
| Masse et al. | Cleaning and decontamination: experimental feedback from PHENIX | |
| Anstine et al. | Evaluation of a dilute chemical decontamination process for boiling water reactors | |
| JPS6117993A (en) | Method of inhibiting adhesion of radioactive substance to constitutional member of nuclear power plant and nuclear power plant with treater | |
| JP3179500B2 (en) | Nuclear power plant and operation method thereof | |
| Seddon | Decontaminating reagents for radioactive systems | |
| JPS63271196A (en) | Method for preventing adhesion of radioactive ion to iron structural material |