JPH079479B2 - Chemical decontamination method for stainless steel - Google Patents
Chemical decontamination method for stainless steelInfo
- Publication number
- JPH079479B2 JPH079479B2 JP33546087A JP33546087A JPH079479B2 JP H079479 B2 JPH079479 B2 JP H079479B2 JP 33546087 A JP33546087 A JP 33546087A JP 33546087 A JP33546087 A JP 33546087A JP H079479 B2 JPH079479 B2 JP H079479B2
- Authority
- JP
- Japan
- Prior art keywords
- stainless steel
- decontamination
- sulfuric acid
- radioactive
- solution
- 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 - Lifetime
Links
- 238000000034 method Methods 0.000 title claims description 27
- 229910001220 stainless steel Inorganic materials 0.000 title claims description 27
- 239000010935 stainless steel Substances 0.000 title claims description 27
- 238000009390 chemical decontamination Methods 0.000 title claims description 7
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 52
- 239000000243 solution Substances 0.000 claims description 22
- 239000010814 metallic waste Substances 0.000 claims description 17
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 9
- 230000001590 oxidative effect Effects 0.000 claims description 9
- 239000000941 radioactive substance Substances 0.000 claims description 8
- 150000003839 salts Chemical class 0.000 claims description 6
- 239000007864 aqueous solution Substances 0.000 claims description 2
- 238000005202 decontamination Methods 0.000 description 32
- 230000003588 decontaminative effect Effects 0.000 description 24
- 239000000463 material Substances 0.000 description 18
- 229910052684 Cerium Inorganic materials 0.000 description 13
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 13
- 238000006243 chemical reaction Methods 0.000 description 13
- 230000002285 radioactive effect Effects 0.000 description 12
- 238000004090 dissolution Methods 0.000 description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 10
- 239000000126 substance Substances 0.000 description 9
- 239000007788 liquid Substances 0.000 description 8
- 238000005253 cladding Methods 0.000 description 5
- 238000005498 polishing Methods 0.000 description 5
- 239000002699 waste material Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 239000007800 oxidant agent Substances 0.000 description 4
- 239000002901 radioactive waste Substances 0.000 description 4
- 238000002161 passivation Methods 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 239000012857 radioactive material Substances 0.000 description 2
- 150000000703 Cerium Chemical class 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 229910000431 copper oxide Inorganic materials 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 description 1
- 238000011038 discontinuous diafiltration by volume reduction Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000004299 exfoliation Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000003758 nuclear fuel Substances 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 238000012958 reprocessing Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
Landscapes
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、放射性金属廃棄物の化学除染方法に係り、特
に、放射性金属廃棄物がステンレス鋼である場合の方法
に関する。Description: TECHNICAL FIELD The present invention relates to a method for chemical decontamination of radioactive metal waste, and more particularly to a method when the radioactive metal waste is stainless steel.
〔従来の技術〕 原子力発電所や核燃料再処理工場等から発生する放射性
物質で汚染された金属廃棄物は、従来、切断等してドラ
ム罐詰めにし、廃棄物建屋に保管されている。この保管
中のドラム罐数は、年々増加傾向にある。このことか
ら、前記放射性金属廃棄物の減容化が望まれている。現
在の減容化技術としては、電解研磨除染法、ブラスト除
染法等が開発されているが、これらの方法では、除染対
象物に電極或いはノズルを挿入する必要があり、バル
ブ、ポンプ等の複雑な形状物への対応は難しい。このよ
うな複雑な形状物に適用できる除染法としては、化学除
染法があるが、従来開発されている化学除染法の多く
は、金属廃棄物の表面に強固に付着し放射性物質の大部
分を取り込んでいるクラツド溶解を目的としている。[Prior Art] Metal waste contaminated with radioactive substances generated from a nuclear power plant, a nuclear fuel reprocessing plant, etc. is conventionally cut and packed in drums and stored in a waste building. The number of drums in storage is increasing year by year. From this, it is desired to reduce the volume of the radioactive metal waste. As the current volume reduction technology, electrolytic polishing decontamination method, blast decontamination method, etc. have been developed, but with these methods, it is necessary to insert an electrode or a nozzle into the decontamination target, and the valve, pump It is difficult to deal with complicated shapes such as. As a decontamination method applicable to such a complicated shape, there is a chemical decontamination method. However, most of the conventionally developed chemical decontamination methods strongly adhere to the surface of metal waste to remove radioactive substances. The purpose is to dissolve the clad, which takes in most of it.
しかしながら、このクラツドが付着している金属母材の
表層には、孔食が発生しており、この深部にも放射性物
質が侵入しているため、母材の表層も汚染していると言
われている。従つて、表面のクラツドだけの化学溶解で
は、この放射性物質の除去は、不充分であり、一般廃棄
物並みの放射能レベルまで除染できないという問題があ
つた。この問題を解決する方法として、硝酸又は硫酸に
４価のセリウムを添加した溶液を用いてクラツドを溶解
又は剥離除去するとともに、金属母材の表層をも酸化溶
解する方法も開発されている。この方法では、４価のセ
リウムが３価になるときの酸化力を利用して金属を溶解
するので、溶解量は添加する４価のセリウムの量に依存
する。例えば、鉄が次式のように３価イオンとなつて溶
解するとき、４価のセリウムは３個の電子を受容し、 Fe→Fe3+＋3e- 3Ce4+＋3e-→3Ce3+ ３価のセリウムとなるため、鉄１モルを溶解するのに、
４価のセリウムは３モル消費される。従つて、除染が完
了するまでに消費される４価のセリウムの量が多いとい
う問題がある。この問題を解決するために、３価のセリ
ウムを４価のセリウムに電解再生して利用する方法も提
案されているが、この方法においては、装置が複雑化
し、使用する電気量も多いという欠点がある。However, it is said that pitting corrosion occurs in the surface layer of the metal base material to which the cladding adheres, and radioactive substances have penetrated into this deep area as well, so the surface layer of the base material is also contaminated. ing. Therefore, there has been a problem that the chemical dissolution of only the clad on the surface is insufficient to remove this radioactive substance and decontamination cannot be performed to a radioactive level comparable to that of general waste. As a method of solving this problem, a method of dissolving or peeling away the cladding using a solution of tetravalent cerium added to nitric acid or sulfuric acid, and oxidizing and dissolving the surface layer of the metal base material has also been developed. In this method, the metal is dissolved by utilizing the oxidizing power when tetravalent cerium becomes trivalent, so the amount of dissolution depends on the amount of tetravalent cerium added. For example, when iron is dissolved Te summer and trivalent ions as follows, tetravalent cerium receive three electron, Fe → Fe 3+ + 3e - 3Ce 4+ + 3e - → 3Ce 3+ 3 valent Since it becomes cerium, it is necessary to dissolve 1 mol of iron.
3 mol of tetravalent cerium is consumed. Therefore, there is a problem that a large amount of tetravalent cerium is consumed until the decontamination is completed. In order to solve this problem, a method of electrolytically regenerating trivalent cerium into tetravalent cerium and using it has been proposed, but in this method, the device is complicated and a large amount of electricity is used. There is.
このような観点から、本出願人は、使用する酸化剤の量
を低減する方法として特願昭62−21608号明細書におい
て、まず、第一工程として、放射性金属廃棄物を硫酸溶
液中に浸漬して大部分の放射性物質を溶解又は剥離除去
した後、次に、硫酸単独液中では溶解しにくい銅やクロ
ム酸化物など、被除染物表面に沈着する物質を溶解する
目的で硫酸に酸化性の金属塩を添加した溶液中に浸漬す
る第二工程とからなる放射性金属廃棄物の除染方法を提
案した。From this point of view, the applicant of the present invention discloses in Japanese Patent Application No. 62-21608 as a method for reducing the amount of the oxidizing agent used, first, as a first step, immersing the radioactive metal waste in a sulfuric acid solution. After dissolving or peeling off most of the radioactive substances, the substance is then oxidized to sulfuric acid for the purpose of dissolving substances that are difficult to dissolve in sulfuric acid alone, such as copper and chromium oxide, that deposit on the surface of the decontamination product. We proposed a method for decontamination of radioactive metal waste, which comprises a second step of immersing the solution in the solution containing the metal salt.
しかしながら、上記の方法では、金属廃棄物のうち表面
が不働態化されているステンレス鋼は、第一工程の硫酸
単独液への浸漬だけでは不働態皮膜が硫酸と母材との接
触をはばむため、母材の溶解反応が進行しにくく、した
がつて、金属廃棄物の表面にあるクラツドも剥離除去し
ないため、この第一工程は実際上、その機能をはたさ
ず、除染はもつぱら、第二工程である硫酸に酸化剤を添
加した溶液中に浸漬することで達成されることになる。
したがつて、不働態化していないステンレス鋼に対して
効果を発揮するが、不働態化したステンレス鋼に対して
は酸化剤低減の効果が小さいという問題があつた。However, in the above method, the stainless steel whose surface is passivated among the metal wastes, because the passivation film prevents contact between the sulfuric acid and the base material only by immersion in the sulfuric acid alone solution in the first step. However, since the dissolution reaction of the base material is difficult to proceed, and therefore the cladding on the surface of the metal waste is not removed by stripping, this first step does not actually function, and decontamination does not occur. The second step is to immerse it in a solution of sulfuric acid with an oxidant added.
Therefore, the effect is exerted on the non-passivated stainless steel, but there is a problem that the effect of reducing the oxidant is small for the passivated stainless steel.
本発明の目的は、前記技術の欠点を解消し、不働態化し
たステンレス鋼製の放射性金属廃棄物を一般廃棄物並み
の放射能レベルにまで化学的に除染するに当り、使用す
る酸化性の金属塩の量が少なくてすむ除染方法の提供を
目的とする。The object of the present invention is to eliminate the drawbacks of the above-mentioned technology, and to chemically decontaminate passivated stainless steel radioactive metal waste to a level of radioactivity equivalent to that of general waste. An object of the present invention is to provide a decontamination method that requires a small amount of the metal salt of.
本発明は、被除染物である不働態化したステンレス鋼か
ら、不働態皮膜の一部を除去すれば、この部分で硫酸と
母材とが次式（１）のごとく反応し、 Fe＋H2SO4→Fe2+＋SO4 2-＋2H+＋2e ……（１） この反応に伴つて、発生する電子（ｅ）が、残存してい
る不働態皮膜の主成分であるFe2O3を次式（２）のよう
に還元して溶解するという、 局部電池の作用により、被除染物の全面が、硫酸溶液中
で溶解することに着目し、前記した不働態皮膜の一部を
除去する手段として、被除染物であるステンレス鋼を硫
酸溶液に浸漬した初期に、ステンレス鋼の電位が活性態
域にくるように、一定時間電圧を印加する操作を行うよ
うにしたものである。According to the present invention, if a part of the passivation film is removed from the passivated stainless steel that is the substance to be decontaminated, sulfuric acid and the base material react in this part as shown in the following formula (1), and Fe + H 2 SO 4 → Fe 2+ ＋ SO 4 2 ＋＋ 2H + ＋ 2e …… (1) The electron (e) generated by this reaction is converted into Fe 2 O 3 which is the main component of the remaining passive film by the following formula. It is reduced and dissolved as in (2), Focusing on the fact that the entire surface of the material to be decontaminated dissolves in the sulfuric acid solution due to the action of the local battery, the stainless steel, which is the material to be decontaminated, is immersed in a sulfuric acid solution as a means of removing a part of the above-mentioned passive film. At the initial stage, the voltage is applied for a certain period of time so that the potential of the stainless steel is in the active state region.
すなわち、本発明によるステンレス鋼の化学除染方法
は、被除染物を硫酸溶液中に浸漬する第一工程と次に、
硫酸に酸化性の金属塩を添加した水溶液中に浸漬する第
二工程とからなる化学除染方法において、前記第一工程
の操作中に、被除染物であるステンレス鋼の電位が活性
態域に入るように電圧を一定時間印加する操作を付加し
たことを特徴とする。That is, the chemical decontamination method of the stainless steel according to the present invention, the first step of immersing the material to be decontaminated in a sulfuric acid solution, and then,
In a chemical decontamination method consisting of a second step of immersing in an aqueous solution in which an oxidizing metal salt is added to sulfuric acid, during the operation of the first step, the potential of the stainless steel to be decontaminated is in the active region. It is characterized in that an operation of applying a voltage for a certain period of time is added so that the voltage is turned on.
電圧を印加して除染する方法としては、電解研摩除染法
があり、電解液として硫酸を用いる方法も知られている
が、電解研摩除染法と本発明の方法の違いを述べる。As a method of decontaminating by applying a voltage, there is an electrolytic polishing decontamination method, and a method of using sulfuric acid as an electrolytic solution is also known, but the difference between the electrolytic polishing decontamination method and the method of the present invention will be described.
第１図に、ステンレス鋼（SUS304）の分極曲線を示し
た。電解研摩除染法は、一般に第１図において、不働態
域にある被除染物（ステンレス鋼製）の電位を電圧を印
加して貴な方向、すなわち、過不働態域に入るように操
作し、具体的には被除染物を陽極とし：電気的な作用に
よる次式の反応を利用して Fe−3e-→Fe3+ ステンレス鋼の母材を酸化溶解させるものであり、電圧
の印加を停止した後は、再び、被除染物の電位は、不働
態域にとどまるため、硫酸との化学的な溶解な進行しな
い。Figure 1 shows the polarization curve of stainless steel (SUS304). The electrolytic polishing decontamination method is generally operated by applying a voltage to the decontamination object (made of stainless steel) in the passive state in FIG. 1 so that it enters in the noble direction, that is, the passive state. , specifically to be divided dyed an anode: electrical Fe-3e by utilizing the following reaction by the action - → the Fe 3+ stainless steel base material is intended to oxidize dissolved, the application of the voltage After the stop, the potential of the substance to be decontaminated remains in the passive state region again, so that the chemical dissolution with sulfuric acid does not proceed.
したがつて、前記したごとく電解研摩除染法では、除染
面に反応電流を流すため、対極は、除染面と対向して設
置する必要があり、複雑な形状物への適用が難しいとい
う問題がある。Therefore, as described above, in the electrolytic polishing decontamination method, since the reaction current is applied to the decontamination surface, it is necessary to install the counter electrode so as to face the decontamination surface, which is difficult to apply to a complicated shape. There's a problem.
これに対し、本発明の方法は、第１図において不働態域
にある被除染物（ステンレス鋼製）の電位を卑な方向に
操作し、具体的には陰極とし、ステンレス鋼が硫酸液中
で化学的に溶解する活性態域に入るように一定時間電位
を操作する。これによつて不働態皮膜を（２）式に示し
たと同様の反応により還元溶解させれば、電圧の印加を
停止した後も、（１）式に示した反応により、ステンレ
ス鋼の母材が硫酸溶液中で、化学溶解することを利用し
たものである。さらに、被除染物の一部分で、この反応
が進行すれば、前記したごとく、局部電池の作用で、残
存する不働態皮膜は（２）式に示した反応により溶解
し、続いて、母材が（１）式に示した反応により溶解す
るという反応が、逐次進行し溶解反応は、被除染物全体
に広がる。したがつて、電圧を印加する時に必要な対極
は、簡単な形状のもので良く、しかも、被除染物の一部
と対向させるだけで良いことから、本発明の方法は、複
雑な形状物に容易に適用できる。On the other hand, in the method of the present invention, the potential of the substance to be decontaminated (made of stainless steel) in the passive state in FIG. 1 is operated in the base direction, specifically, the cathode is used, and the stainless steel is in a sulfuric acid solution. The potential is manipulated for a certain period of time so that it enters the active state where it is chemically dissolved. Accordingly, if the passive film is reduced and dissolved by a reaction similar to that shown in the formula (2), the stainless steel base material is formed by the reaction shown in the formula (1) even after the voltage application is stopped. It utilizes chemical dissolution in a sulfuric acid solution. Furthermore, if this reaction proceeds in a part of the material to be decontaminated, as mentioned above, the remaining passive film is dissolved by the reaction shown in the formula (2) by the action of the local battery, and then the base material is The reaction of dissolution by the reaction represented by the formula (1) sequentially proceeds, and the dissolution reaction spreads over the entire decontamination product. Therefore, the counter electrode required when applying a voltage may have a simple shape, and since it only needs to face a part of the material to be decontaminated, the method of the present invention can be applied to a complicated shape. Easy to apply.
次に、図面に基づいて本発明を説明する。第２図は、本
発明の方法を示す概念図である。Next, the present invention will be described based on the drawings. FIG. 2 is a conceptual diagram showing the method of the present invention.
第２図において、第１除染槽１には第１液として硫酸を
使用する。この第１液はヒータ２によつて所定温度まで
加温される。また、第２除染槽３には、第２液として硫
酸に４価のセリウム塩、６価のクロム酸塩又は重クロム
酸塩あるいは、過マンガン酸塩などの酸化剤のいずれか
を添加した液を使用し、この第２液もヒータ４によつて
所定温度に加温される。In FIG. 2, sulfuric acid is used as the first liquid in the first decontamination tank 1. The first liquid is heated to a predetermined temperature by the heater 2. Further, in the second decontamination tank 3, sulfuric acid as a second liquid was added with any one of an oxidizing agent such as tetravalent cerium salt, hexavalent chromate or dichromate, or permanganate. A liquid is used, and the second liquid is also heated to a predetermined temperature by the heater 4.
本発明によれば、ステンレス鋼製の放射性金属廃棄物
は、次のように除染される。According to the invention, stainless steel radioactive metal waste is decontaminated as follows.
まず、放射性金属廃棄物５は、第１除染槽１中におい
て、第１液である硫酸溶液中に浸漬される。この時、放
射性金属廃棄物の電位を、電位測定槽８に設置した参照
電極を用いて、記録装置10に記録する。First, the radioactive metal waste 5 is immersed in the sulfuric acid solution which is the first liquid in the first decontamination tank 1. At this time, the potential of the radioactive metal waste is recorded in the recording device 10 by using the reference electrode installed in the potential measuring tank 8.
この時、測定した電位が不働態域にあれば、参照電極９
で電位を測定しながら、放射性廃棄物５の電位が活性化
域になるように、電源７によつて放射性廃棄物５と対極
６の間に電圧を一定時間印加する。電圧の印加を停止し
た後、再び参照電極９を用いて放射性廃棄物５の電位を
測定し、活性態域にあれば第１液である硫酸との化学溶
解反応が行なわれていることであるから、電圧の印加を
停止したまま、第１液への浸漬を続ける。このとき、ま
だ不働態域にあれば、再度、電圧を印加し、電圧の印加
を停止後に、電位が活性態域に停滞するようになるま
で、この操作を繰り返す。電圧の印加時間は、不働態化
の程度に左右されるが、１〜20分程度で十分である。At this time, if the measured potential is in the passive state region, the reference electrode 9
While measuring the electric potential with, a voltage is applied between the radioactive waste 5 and the counter electrode 6 by the power source 7 for a certain period of time so that the electric potential of the radioactive waste 5 is in the activation region. After stopping the application of the voltage, the potential of the radioactive waste 5 is measured again using the reference electrode 9, and if it is in the active state, it means that the chemical dissolution reaction with the sulfuric acid which is the first liquid is being carried out. Therefore, the immersion in the first liquid is continued while the voltage application is stopped. At this time, if it is still in the passive state region, the voltage is applied again, and after the application of the voltage is stopped, this operation is repeated until the potential becomes stagnant in the active state region. The voltage application time depends on the degree of passivation, but about 1 to 20 minutes is sufficient.
このようにして、第１除染槽では、母材の溶解及びこれ
に伴つて表面に固着した、クラツドの剥離により、放射
性物質の90％以上が除去される。しかし、ステンレス鋼
と硫酸溶液の化学反応による溶解では、ステンレス鋼に
不純物として含まれる銅や、剥離されずに残つたクラツ
ドの一部が、被除染物の表面に沈着しており、これに一
旦溶出した放射性物質の一部が取り込まれるため、被除
染物表面の沈着物を溶解する操作として、次に、第２液
として、硫酸に酸化性の金属塩を添加した液が入つてい
る第２除染槽３に浸漬する。このようにして不働態化し
たステンレス鋼製の放射性廃棄物は、除染される。In this way, in the first decontamination tank, 90% or more of the radioactive material is removed by the dissolution of the base material and the accompanying exfoliation of the cladding that adheres to the surface. However, in the dissolution by the chemical reaction between the stainless steel and the sulfuric acid solution, copper contained as impurities in the stainless steel and a part of the cladding left unpeeled are deposited on the surface of the decontamination material, and Since a part of the eluted radioactive substance is taken in, as an operation for dissolving the deposit on the surface of the material to be decontaminated, the second solution is the second solution in which a solution obtained by adding an oxidizing metal salt to sulfuric acid is contained. Immerse in the decontamination tank 3. The passivated stainless steel radioactive waste is decontaminated.
次に実施例に基づいて本発明を詳述するが、本発明は、
これに限定されるものではない。Next, the present invention will be described in detail with reference to Examples.
It is not limited to this.
実 験 例 放射性物質で汚染され、不働態化しているSUS304製バル
ブを、第２図に示した本発明の方法と、電位操作を行な
わない従来の方法とにより除染し、放射能が検出限界以
下（１×10-5μCi/cm2）になるまでの除染時間と、酸化
材として使用した４価のセリウムの使用量を比較した。Experimental example A valve made of SUS304 which is contaminated with radioactive material and has been passivated is decontaminated by the method of the present invention shown in FIG. The decontamination time until the following (1 × 10 −5 μCi / cm 2 ) was reached was compared with the amount of tetravalent cerium used as the oxidizing material.
第１表に各工程の除染条件を、第２表に結果を示す。Table 1 shows the decontamination conditions of each step, and Table 2 shows the results.
従来の方法では、除染の効果がもつぱら第２液である硫
酸に４価のセリウムを添加した液中に浸漬する第二工程
に依存しこの第２液中での溶解速度が遅いため、４価の
セリウムの使用量が多く、除染時間も長い。本発明の方
法では、第１液である硫酸液中に浸漬する第一工程で、
大部分の放射性物質が除去されるため、４価のセリウム
の使用量は、従来法の700分の１と少なく、また、除染
時間も４分の１にできた。 In the conventional method, the decontamination effect is dependent on the second step of immersing in the solution of tetravalent cerium added to sulfuric acid, which is the second solution of para, and the dissolution rate in this second solution is slow. The amount of tetravalent cerium used is large and the decontamination time is long. In the method of the present invention, in the first step of immersing in the sulfuric acid solution which is the first solution,
Since most of the radioactive substances are removed, the amount of tetravalent cerium used is as low as 1/700 of the conventional method, and the decontamination time can be reduced to 1/4.
以上詳述したように、本発明によれば、不働態化したス
テンレス鋼製の放射性金属廃棄物を一般廃棄物並みの放
射能レベルにまで、化学的に除染するために使用する酸
化性の金属塩が微量ですみ、除染後の二次廃棄物量を少
なくできる。As described in detail above, according to the present invention, the oxidizing metal waste made of passivated stainless steel can be used to chemically decontaminate radioactive metal waste to a level of radioactivity equivalent to that of general waste. Only a small amount of metal salt is needed, and the amount of secondary waste after decontamination can be reduced.
第１図は、SUS304鋼の分極曲線、第２図は、本発明の方
法を示す概念図である。 １……第１除染槽,3……第２除染槽， ５……放射性金属廃棄物,6……対極， ７……電源,9……参照電極。FIG. 1 is a polarization curve of SUS304 steel, and FIG. 2 is a conceptual diagram showing the method of the present invention. 1 …… First decontamination tank, 3 …… Second decontamination tank, 5 …… Radioactive metal waste, 6 …… Counter electrode, 7 …… Power supply, 9 …… Reference electrode.
Claims (1)
製の金属廃棄物を硫酸溶液中に浸漬する第一工程の後、
次に硫酸に酸化性の金属塩を添加した水溶液中に浸漬す
る第二工程とからなるステンレス鋼の化学除染方法にお
いて、前記第一工程の操作中に、被除染物であるステン
レス鋼の電位が、活性態域にくるように電圧を一定時間
印加する操作を付加したことを特徴とするステンレス鋼
の化学除染方法。1. After the first step of immersing a stainless steel metal waste whose surface is contaminated with radioactive substances in a sulfuric acid solution,
Next, in the chemical decontamination method of stainless steel consisting of a second step of immersing in an aqueous solution in which an oxidizing metal salt is added to sulfuric acid, during the operation of the first step, the potential of the stainless steel to be decontaminated is However, the method for chemically decontaminating stainless steel is characterized in that an operation of applying a voltage for a certain period of time is added so that the stainless steel is in an active state region.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP33546087A JPH079479B2 (en) | 1987-12-28 | 1987-12-28 | Chemical decontamination method for stainless steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP33546087A JPH079479B2 (en) | 1987-12-28 | 1987-12-28 | Chemical decontamination method for stainless steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01173900A JPH01173900A (en) | 1989-07-10 |
| JPH079479B2 true JPH079479B2 (en) | 1995-02-01 |
Family
ID=18288805
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP33546087A Expired - Lifetime JPH079479B2 (en) | 1987-12-28 | 1987-12-28 | Chemical decontamination method for stainless steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH079479B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2937054B1 (en) * | 2008-10-13 | 2010-12-10 | Commissariat Energie Atomique | METHOD AND DEVICE FOR DECONTAMINATING A METAL SURFACE |
| FR3162096A1 (en) | 2024-05-07 | 2025-11-14 | Orano Ds - Demantelement Et Services | Radioactive decontamination process for the metal wall of a fluid circulation system |
-
1987
- 1987-12-28 JP JP33546087A patent/JPH079479B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01173900A (en) | 1989-07-10 |
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