EP0305943B1 - Ätzverfahren für Metallgegenstände aus Zirkonium - Google Patents

Ätzverfahren für Metallgegenstände aus Zirkonium Download PDF

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Publication number
EP0305943B1
EP0305943B1 EP88114045A EP88114045A EP0305943B1 EP 0305943 B1 EP0305943 B1 EP 0305943B1 EP 88114045 A EP88114045 A EP 88114045A EP 88114045 A EP88114045 A EP 88114045A EP 0305943 B1 EP0305943 B1 EP 0305943B1
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EP
European Patent Office
Prior art keywords
bath
zirconium
etching
rise
temperature
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
Application number
EP88114045A
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English (en)
French (fr)
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EP0305943A3 (en
EP0305943A2 (de
Inventor
Armand Julian Panson
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CBS Corp
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Westinghouse Electric Corp
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Publication of EP0305943A2 publication Critical patent/EP0305943A2/de
Publication of EP0305943A3 publication Critical patent/EP0305943A3/en
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    • 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
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F1/00—Etching metallic material by chemical means
    • C23F1/10—Etching compositions
    • 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
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F1/00—Etching metallic material by chemical means
    • C23F1/10—Etching compositions
    • C23F1/14—Aqueous compositions
    • C23F1/16—Acidic compositions
    • C23F1/26—Acidic compositions for etching refractory metals

Definitions

  • the present invention relates to a process for etching metallic objects formed from zirconium or a zirconium alloy and specifically to a process for determining when an etching bath should be regenerated.
  • Zirconium components are especially preferred in nuclear reactor systems such as nuclear fuel cladding.
  • zirconium alloy tubes are pilgered to reduce the size thereof, and are subsequently etched to remove defects from the tubing surface.
  • the preferred zirconium alloys for use in nuclear fuel cladding include Zircaloy-2 and Zircaloy-4.
  • An aqueous hydrofluoric acid - nitric acid etching bath is the preferred etching medium.
  • the etching rate of such an aqueous bath decreases with use, upon dissolution of zirconium into the bath, until a limiting rate of about 20 percent of the fresh or initial bath is reached.
  • the used or spent bath which will generally contain about 24g/l of dissolved zirconium alloy was discarded.
  • the spent bath was treated to render it disposable before being discarded.
  • the spent bath contains, among other components, various zirconium compounds or complexes, some tin components when Zircaloy is etched, and residual hydrofluoric and nitric acids.
  • the dissolved zirconium content of the bath must be determined.
  • One method of determining the dissolved zirconium content of an etching bath is to remove a sample of the bath and analyze the same in a laboratory to ascertain the zirconium content, a time consuming and costly process.
  • Other faster and less costly procedures have been proposed, but as described in published German Patent Disclosure No. 28 28 547, the determination of zirconium metal content in hydrofluoric acid containing etching baths by calorimetric or titrimetric methods is not feasible.
  • the zirconium content of a hydrofluoric acid - nitric acid etching bath is determined by drawing off a portion of the bath, precipitating the metal in the portion in a form of a difficult to dissolve compound, and determining the concentration of the difficult to dissolve compound in a diluting agent by measuring the turbidity thereof.
  • the preferred precipitating agent is a solution of caustic soda which precipitates the zirconium in the form of zirconium hydroxide, and water to adjust to the necessary dilution.
  • the present invention resides in a process for etching of zirconium metallic articles with determination of the dissolved zirconium metal content of the bath during the etching process, as defined in claim 1 and as further characterized in subclaims 2 and 3, and, similarly, in a process of determining the dissolved zirconium content of an etching bath for zirconium metal objects as defined in claim 4 and as further charaterized in subclaim 5.
  • the process according to the invention makes use of the rise in temperature caused by the etch reaction in the etching solution.
  • This phenomena is known per se from document NL-A-6 515 842 disclosing a process for manufacturing semiconductor slices in which a surface layer with predetermined thickness is removed by treatement in an etchant, wherein the same number of slices with identical dimensions is being etched in the same volume of etchant in each turn and the change of temperature of the etchant caused by the etch reaction is chosen as an indication that the required amount of material has been removed.
  • the appropriate change of temperature of the etchant is determined empirically.
  • an initial determination is made of the rise in temperature of a predetermined volume of the aqueous etching bath upon immersion of a known quantity of a zirconium article, having a known surface area, therein, over a known period of time, as a function of the dissolved zirconium content of the bath.
  • the dissolved zirconium content of the bath at various times during an etching process is determined by immersing a known quantity of a zirconium metal object having a known surface area into a portion of the bath having the predetermined volume, measuring the rise in temperature of the bath portion over a predetermined time period, and then determining the dissolved zirconium metal content of the bath as a function of the rise in temperature.
  • only a small volume of the bath is used by separating or otherwise segregating the predetermined volume from the bulk of the bath, and immersing the zirconium metal object therein while stirring the bath portion and measuring the temperature rise by use of a thermocouple immersed in the bath portion.
  • the present process provides a calorimetric method for determining the loading of zirconium in an etching bath so as to provide an indication of when the bath should be replenished or replaced.
  • the process thus provides a practical method for determining the dissolved zirconium content or loading of aqueous hydrofluoric acid - nitric acid etching baths for nuclear fuel cladding.
  • etching is used for surface polishing and also to increase the inside diameter of the tubing.
  • the articles are etched by being immersed into an aqueous acid bath.
  • Current etching baths for such articles can use horizontal unstirred etching baths that contain an aqueous solution of 2 to 4 percent, preferably 2 or 3 percent, by weight hydrofluoric acid and 12 to 35 percent, preferably 15 percent, by weight nitric acid.
  • the Zircaloy-4 tubes are immersed in the bath for a predetermined period of time, with the immersion duration increased for a given increase of inside diameters of the tubes due to the exhaustion of bath strength with use.
  • the contact of the zirconium metal article with the etching bath results in dissolution of metallic components, particularly zirconium metal in ionic or complex form, in the bath and hydrofluoric acid and nitric acid are consumed such that the activity of the bath must be either regenerated or the bath discarded and fresh etching solution provided.
  • the present process comprises a calorimetric method for determining the dissolved zirconium content of an etching bath at any desired time during use of the bath for etching of zirconium metal articles.
  • This information then allows the bath loading to be determined by simple measurement of temperature increase for a given etching time.
  • the dissolved zirconium content of the bath at various times during an etching process can then be determined by immersing a known quantity of a zirconium metal object having the known surface area into a portion of the bath having the predetermined volume and measuring the rise in temperature of the bath portion over a predetermined time period.
  • the dissolved zirconium content of the bath can then be determined as a function of the rise in temperature by comparing the measured rise in temperature of the bath portion having the unknown concentration of zirconium over the predetermined time period with the information initially obtained for baths having a known concentration of zirconium.
  • a 1-inch (25.4 mm) length of Zircaloy-4 tubing (typically 0.375 inch (9.53 mm) outer diameter and wall thickness of 0.023 inch (0.58 mm) ), of known surface area, was immersed in a 40 ml portion of the hydrofluoric acid (2%) - nitric acid (15%) aqueous etching bath. The bath was agitated with a magnetic stirring bar and the temperature rise of the bath portion over a one minute time period was measured.
  • a temperature rise of 1°C was observed when the dissolved zirconium content of the portion was about 0.012 gms; a rise of about 2°C corresponded to a content of about 0.028 gms; a rise of about 5°C corresponded to a content of about 0.072 gms; and a rise of about 6°C corresponded to a content of about 0.085 gms.
  • the temperature rise is proportional to the weight of zirconium dissolved in the acid bath, with the temperature increase due to the heat of the dissolution reaction, which was determined to be about 2.72 kcal/gm Zircaloy-4 dissolved.
  • etching rate of a hydrofluoric acid - nitric acid bath for zirconium metals decreases as the bath loading or dissolved zirconium content of the bath increases.
  • etch rates of the bath decrease with use until a limiting rate of about 20 percent of the fresh or initial bath is reached.
  • Figure 2 illustrates graphically the etching rate of the previously described Zircaloy-4 sample in a 2% hydrofluoric acid - 15% nitric acid aqueous etching bath versus the loading, or dissolved zirconium content, of the bath.
  • Another of the previously described Zircaloy-4 samples is then immersed in the acid bath of unknown zirconium concentration for a minute and the temperature rise after one minute can be compared with the previously determined temperature rise after one minute of baths of known zirconium concentration to determine the unknown zirconium concentration of the acid bath having the unknown zirconium concentration.
  • the zirconium concentration of the acid bath can be determined in this way several times during the etching process until the zirconium concentration of the bath is such that the bath needs to be rejuvenated.
  • the present process is useful in etching of articles, such a nuclear fuel cladding, that are composed of zirconium or a zirconium alloy such as Zircaloy-2 or Zircaloy-4.
  • the alloy Zircaloy-2 contains, by weight, about 1.2 to 1.7 percent tin, 0.07 to 0.20 percent iron, 0.05 to 0.15 percent chromium, and about 0.03 to 0.08 percent nickel, the balance being zirconium
  • Zircaloy-4 contains, by weight, about 1.2 to 1.7 percent tin, 0.12 to 0.18 percent iron, and 0.05 to 0.15 percent chromium, the balance being zirconium.
  • the etching process is effected at atmospheric pressure and ambient temperature, although upon exothermic reaction of the acids and the metal, an increase in bath temperature will result. Temperatures of between about 20°C and 50°C are generally used.
  • a test of the present invention was effected on a plant scale etching system.
  • a sample of spent etch bath was measured using the present calorimetric method to determine the zirconium content of the bath.
  • the etching bath contained about 500 gallons (1893 l) of aqueous nitric acid - hydrofluoric acid solution (2%HF - 15%HNO3), and was used to etch final-size Zircaloy-4 fuel cladding.
  • the tube lengths were about 12 feet (3.66 m). The etching was carried out on successive lots of these tubes until the bath was judged to be exhausted by the operator based on experience with the immersion time required to achieve a required size reduction.
  • FIG. 4 A schematic illustration of an apparatus 1 for carrying out the present process is illustrated in Figure 4.
  • a vessel 3 such as a plastic container, is disposed on a magnetic stirrer 5, for receipt of a predetermined volume of an acid bath 7, from a vat containing an existing etching bath, the zirconium content of which is to be measured.
  • a plastic coated magnetic stirring bar 8 is placed in the bath, and a thermocouple 9 inserted into the bath which is connected to a thermocouple detector 11 for temperature readings.
  • a plastic support 13 extends from a base (not shown) to a location within the bath 7.
  • a known quantity of zirconium metal 15, having a known surface area, is suspended on the plastic support 13 within the bath and the bath agitated by actuation of the magnetic stirrer 5 and movement of the magnetic stirring bar 8.
  • the temperature rise of the bath 7 over a predetermined time period, such as a minute, is measured. This temperature rise is then used to determine the zirconium content of the acid bath.
  • the thermocouple detector 11, as illustrated may be associated with a control system 17, that will determine the amount of fresh acid to be added to the existing etching bath to regenerate the same.
  • the present process thus provides a calorimetric measurement and control of an etching process, a simple, direct, and inexpensive process to provide production control measurements for etching operations.
  • the process provides for on-line detection of bath loading and etching rates and forms the basis for production control systems.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • ing And Chemical Polishing (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
  • Chemically Coating (AREA)

Claims (5)

  1. Verfahren zum Ätzen von Zirkoniummetallgegenständen aus Zirkonium oder einer Zirkoniumlegierung, wobei die Zirkoniummetallgegenstände mit einem Bad (7) aus wäßriger Fluorwasserstoffsäure-Salpetersäure-Ätzlösung in einem Tank in Berührung gebracht werden, wobei der aufgelöste Zirkoniummetallgehalt des Bades während des Ätzvorgangs als Anzeige dafür bestimmt wird, die Ätzlösung verbraucht ist, dadurch gekennzeichnet, daß:
    anfänglich die Temperaturanstiegsgeschwindigkeit in einem vorgegebenen Volumen frischer Ätzlösung nach Eintauchen einer bekannten Menge des Zirkoniummetalls (15) mit bekannter Oberfläche während einer gegebenen Zeitspanne als Funktion des aufgelösten Zirkoniumgehalts in dem Bad (7) bestimmt wird;
    später während des Ätzvorgangs eine bekannte Menge eines Zirkoniummetallgegenstands (15) mit bekannter Oberfläche in eine Probe der benutzten Ätzlösung aus dem Bad (7) mit dem vorgegebenen Volumen eingetaucht wird;
    die Temperaturanstiegsgeschwindigkeit in der Badprobe aufgrund der Auflösung des Zirkoniummetallgegenstands (15) darin über eine vorgegebene Zeitspanne gemessen wird;
    und der aufgelöste Zirkoniummetallgehalt des Bades (7) als Funktion der Temperaturanstiegsgeschwindigkeit in der Badprobe bestimmt wird.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Probe des Bads (7) aus dem Bad (7) entnommen und in ein Gefäß (3) übertragen wird, in welchem der Temperaturanstieg gemessen wird.
  3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß das Bad durch Regenerieren desselben behandelt wird und ein weiteres Ätzen von Zirkoniummetallgegenständen in dem regenerierten Bad stattfindet.
  4. Verfahren zur Bestimmung des aufgelösten Zirkoniumgehalts eines wäßrigen Fluorwasserstoffsäure-Salpetersäure-Ätzbades (7) für Zirkoniummetallgegenstände, gekennzeichnet durch:
    Bestimmen der Temperaturgeschwindigkeit in einem vorgegebenen Volumen eines frischen Bades (7) beim Eintauchen einer bekannten Menge des Zirkoniummetalls (15) mit bekannter Oberfläche während einer bekannten Zeitspanne als Funktion des aufgelösten Zirkoniumgehalts des Bades (7);
    nach gewisser Benutzungsdauer des Bades Eintauchen einer bekannten Menge eines Zirkoniummetallgegenstandes (15) mit bekannter Oberfläche in eine Probe des Bades (7) mit dem vorgegebenen Volumen;
    Messen des Temperaturanstiegs in der Badprobe (7) aufgrund der Auflösung des Zirkoniummetallgegenstands (15) darin während einer vorgegebenen Zeitspanne; und
    Bestimmen des aufgelösten Zirkoniummetallgehalts des Bades (7) als Funktion des Temperaturanstiegs der Badprobe (7).
  5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, daß die Probe aus dem benützten Bad (7) entnommen und in ein Gefäß (3) übertragen wird, in welchem die Messung stattfindet.
EP88114045A 1987-08-31 1988-08-29 Ätzverfahren für Metallgegenstände aus Zirkonium Expired - Lifetime EP0305943B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US9122587A 1987-08-31 1987-08-31
US91225 1993-07-13

Publications (3)

Publication Number Publication Date
EP0305943A2 EP0305943A2 (de) 1989-03-08
EP0305943A3 EP0305943A3 (en) 1990-01-10
EP0305943B1 true EP0305943B1 (de) 1993-10-20

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ID=22226687

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EP88114045A Expired - Lifetime EP0305943B1 (de) 1987-08-31 1988-08-29 Ätzverfahren für Metallgegenstände aus Zirkonium

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EP (1) EP0305943B1 (de)
JP (1) JPS6475685A (de)
KR (1) KR890003986A (de)
DE (1) DE3885044T2 (de)
ES (1) ES2045045T3 (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100265556B1 (ko) 1997-03-21 2000-11-01 구본준 식각장치

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3419446A (en) * 1965-02-15 1968-12-31 Chemcut Corp Method and means for continuous control of etching rate
NL6515842A (de) * 1965-12-07 1966-12-27
DE2828547C2 (de) * 1978-06-29 1982-12-23 Didier-Werke Ag, 6200 Wiesbaden Verfahren zur Steuerung oder Regelung der Beizbadzusammensetzung einer Beizanlage
US4738747A (en) * 1986-07-22 1988-04-19 Westinghouse Electric Corp. Process for etching zirconium metallic objects

Also Published As

Publication number Publication date
EP0305943A3 (en) 1990-01-10
JPS6475685A (en) 1989-03-22
ES2045045T3 (es) 1994-01-16
KR890003986A (ko) 1989-04-19
EP0305943A2 (de) 1989-03-08
DE3885044D1 (de) 1993-11-25
DE3885044T2 (de) 1994-02-17

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