EP0418722A1 - Procédé de décontamination totale de matériau métallique radioactif - Google Patents

Procédé de décontamination totale de matériau métallique radioactif Download PDF

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Publication number
EP0418722A1
EP0418722A1 EP90117571A EP90117571A EP0418722A1 EP 0418722 A1 EP0418722 A1 EP 0418722A1 EP 90117571 A EP90117571 A EP 90117571A EP 90117571 A EP90117571 A EP 90117571A EP 0418722 A1 EP0418722 A1 EP 0418722A1
Authority
EP
European Patent Office
Prior art keywords
bath
tank
ultrasounds
solution
khz
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.)
Granted
Application number
EP90117571A
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German (de)
English (en)
Other versions
EP0418722B1 (fr
Inventor
Fiorenzo Bregani
Antonio Garofalo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Enel SpA
Original Assignee
Enel SpA
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Filing date
Publication date
Application filed by Enel SpA filed Critical Enel SpA
Publication of EP0418722A1 publication Critical patent/EP0418722A1/fr
Application granted granted Critical
Publication of EP0418722B1 publication Critical patent/EP0418722B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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

Definitions

  • This prevent invention relates to a total decontamination process for metal radioactive material, in particular to radiactive metal material presenting big surfaces and recesses, like the tubes for the tube nests in the heat exchangers of a nuclear power station.
  • radioactive metal surfaces are decontaminated by means of chemical solutions of different kinds, electrolytic precesses, mechanical means, pressurized water jets and ultrasounds.
  • the drawback in the known processes resides in the unsatisfactory effectiveness for material presenting big surfaces and recesses, as it particularly happens in said tubes, so that there is always some residual radiactivity preventing from completing decontamination, and consequently, reducing the waste amounts to be delivered to said storages.
  • This invented process first uses together ultrasounds and washing in a water bath and then uses together ultrasounds and washing in a strong mineral acids bath according to steps that, as known, lead to a synergic effect in the action of removing the contaminated layer from the surface of the radioactive metal material.
  • this invented process defines a whole of conditions which allow the maximum decontaminating effect and are set substantially through the steps of: subjecting the radioactive material dipped in a first bath of controlled temperature water to a beam of continuous ultrasounds of controlled frequency; removing said material from said first bath and washing it in fresh water; subjecting said material to a second bath in a water solution of strong mineral acids under controlled temperature and subjecting said material in said second bath to a continuous ultrasound flow of controlled frequency.
  • the length of last said step varies according to the strength of the acid bath and decreases as the material dissolves; preferably, a sequence of immersions is carried out; at the end of each immersion, the material is removed from the bath in order to carry out a preliminary visual examination and the material presenting metallic gloss on its inner and outer surfaces is removed from the bath and delivered to radiometric checking.
  • the solution is considered exhaust as the iron concentration is higher than 30 g/l (the iron concentration may be determined, for instance, by a spectrophotometer).
  • this invented process is particularly suitable to decontaminate tubes of the tube nests of the heat exchangers in the nuclear power stations and more particularly tube nests of the feeding regenerators in boiling water power stations.
  • the paramount advantage of this invented process resides in that the radiactive material is decontaminated over those standars that are usually accepted for releasing non-inspected or non-­conditioned material and in that the waste to be delivered to said storages, consisting in the residuals from the decontaminating solutions, are much reduced in amount.
  • a monorail 1 moves in the direction of arrow 2 a plurality of hung and conveniently spaced cages 3, each containing a set 4 of one hundred tubes each being one meter long and set in the cage vertically; each set of tubes 4 in its cage is dipped sequentially in the tanks 5, 6, 7 and 8 by hoists 9, as detailed hereinbelow.
  • First tank 5 comprises an inner tank 5A and an outer tank 5B, both covered by a common cover 5C; inner tank 5A contains washing water for the tubes and in outer tank 5B is circulated a diathermic solution to keep at 55° C the temperature of the washing water in tank 5A.
  • Said solution is supplied from a suitable conventional first boiler, not shown in the figure, that gives it the required temperature; a pump, not shown in the figure, supplies the solution to the tank through inlet duct 10 and the solution comes back to said boiler through outlet duct 11.
  • Bottom exhaust means 12 allows to completely empty tank 5B, if necessary.
  • An assembly of ultrasound emitting piezoelectric transducers 13, of 20 kHz frequency, is applied to the outer of side and bottom walls of tank 5B, said transducers being of such specification and number as to maintain in the inner tank 5A an homogeneous power density of 25 Watt per liter (W/l).
  • the tank 5A inner sizes are 50 x 50 x 150 cm (150 cm height).
  • the tube set 4 is left in the washing water during a time period of 2 hours.
  • Second tank 6 recycles a steam of fresh water from an outer source through inlet and outlet ducts, not shown in the figure, to energetically wash the tubes of a set of tubes 4 dipped in said tank together with its cage 3, after removal from tank 5.
  • Tank 6 too comprises bottom exhaust means 14.
  • Third tank 7 comprises an inner tank 7A and an outer tank 7B; the inner tank contains a solution from 3,0% to 4,0% of HF (hydrofluoric acid) and from 5,0% to 6,0% of HNO3 (nitric acid) (% in volume), in water maintained at the temperature of 70° C by a diathermic solution which is supplied to tank 7B through inlet duct 15 and removed through inlet 16, similarly to the explaination referred to tank 5.
  • Tank 7A is covered by cover 17 provided with an opening connected with an intake tube 18 to remove acid vapours emitted from the solution in the tank.
  • Tank 7B is provided with a bottom exhaust means 21.
  • An assembly of ultrasound emitting piezoelectric tranducers 20 is applied to the outer of side and bottom walls of tank 7B, similarly to the description referred to tank 5.
  • Fourth tank 8 is similar to tank 6 described above.
  • the decontaminated tubes are washed in running water energetically in said fourth tank to release in the water the residual radioactive material particles detached from the tube outer and, in particular, inner surface.
  • This tank too is provided with a bottom exhaust means 22.
  • a cable 23 is associated to the hoist 9 supporting a cage 3 and a clamp 24 at the bottom of said cable holds said cage.
  • tanks and other parts which may be in contact with radioactive materials and with acids are made of suitable materials.

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Food Science & Technology (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Cleaning By Liquid Or Steam (AREA)
EP90117571A 1989-09-21 1990-09-12 Procédé de décontamination totale de matériau métallique radioactif Expired - Lifetime EP0418722B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT2177789 1989-09-21
IT8921777A IT1232632B (it) 1989-09-21 1989-09-21 Processo di decontaminazione totale di materiali metallici radioattivi.

Publications (2)

Publication Number Publication Date
EP0418722A1 true EP0418722A1 (fr) 1991-03-27
EP0418722B1 EP0418722B1 (fr) 1994-12-28

Family

ID=11186713

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90117571A Expired - Lifetime EP0418722B1 (fr) 1989-09-21 1990-09-12 Procédé de décontamination totale de matériau métallique radioactif

Country Status (3)

Country Link
EP (1) EP0418722B1 (fr)
DE (1) DE69015529D1 (fr)
IT (1) IT1232632B (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106158060A (zh) * 2016-08-23 2016-11-23 中国工程物理研究院核物理与化学研究所 一种去除放射性表面污染的超声电解自动去污系统

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102016208202A1 (de) * 2016-05-12 2017-11-16 Rwe Power Aktiengesellschaft Chemische Dekontamination von radioaktiven Metalloberflächen

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0106959A2 (fr) * 1982-10-21 1984-05-02 ABB Reaktor GmbH Procédé et installation pour enlever les dépôts sur les surfaces des composants d'une installation nucléaire refroidie à l'eau
FR2586322A1 (fr) * 1985-08-14 1987-02-20 Framatome Sa Procede de nettoyage et de decontamination par ultrasons d'enceintes et dispositif correspondant
FR2590716A1 (fr) * 1985-11-26 1987-05-29 Electricite De France Procede de decontamination de parois de reacteurs nucleaires, en particulier des parois du circuit primaire des reacteurs nucleaires a circuit d'eau pressurisee

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0106959A2 (fr) * 1982-10-21 1984-05-02 ABB Reaktor GmbH Procédé et installation pour enlever les dépôts sur les surfaces des composants d'une installation nucléaire refroidie à l'eau
FR2586322A1 (fr) * 1985-08-14 1987-02-20 Framatome Sa Procede de nettoyage et de decontamination par ultrasons d'enceintes et dispositif correspondant
FR2590716A1 (fr) * 1985-11-26 1987-05-29 Electricite De France Procede de decontamination de parois de reacteurs nucleaires, en particulier des parois du circuit primaire des reacteurs nucleaires a circuit d'eau pressurisee

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT OFFICE OF JAPAN, FILE SUPPLIER JAPS, Tokyo, JP; & JP-A-1 233 398 (TOSHIBA) *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106158060A (zh) * 2016-08-23 2016-11-23 中国工程物理研究院核物理与化学研究所 一种去除放射性表面污染的超声电解自动去污系统

Also Published As

Publication number Publication date
IT8921777A0 (it) 1989-09-21
DE69015529D1 (de) 1995-02-09
EP0418722B1 (fr) 1994-12-28
IT1232632B (it) 1992-02-28

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