Effects of hydrogen on electropotential monitoring of stress corrosion crack growth

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Description

Electropotential monitoring (EPM) has a crack growth measurement resolution that is an order of magnitude greater than methods that rely on crack mouth opening displacement. However, two phenomena have been identified that compromise the accuracy of the EPM technique. Coolant hydrogen concentrations above those needed to chemically reduce nickel oxide to metallic nickel cause EPM to underestimate the true crack length. The metallic nickel provides an electrical conduction path at contact points across the irregular crack surface thereby lowering the EPM potential. The coolant hydrogen concentration at which this reduction occurs is temperature dependent and correlates with an abrupt decrease ... continued below

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7 p.

Creation Information

Thompson, C.D.; Carey, D.M. & Perazzo, N.L. August 1, 1997.

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  • Knolls Atomic Power Laboratory
    Publisher Info: Knolls Atomic Power Lab., Schenectady, NY (United States)
    Place of Publication: Schenectady, New York

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Description

Electropotential monitoring (EPM) has a crack growth measurement resolution that is an order of magnitude greater than methods that rely on crack mouth opening displacement. However, two phenomena have been identified that compromise the accuracy of the EPM technique. Coolant hydrogen concentrations above those needed to chemically reduce nickel oxide to metallic nickel cause EPM to underestimate the true crack length. The metallic nickel provides an electrical conduction path at contact points across the irregular crack surface thereby lowering the EPM potential. The coolant hydrogen concentration at which this reduction occurs is temperature dependent and correlates with an abrupt decrease in the rate of SCC crack growth. It was also found that EPM can indicate large crack growth when none actually exists. At temperatures > 315 C (600 F) the electrical resistivity of mill annealed Alloy 600 increased by as much as 5% in a period of weeks or months. Each 1% increase in resistivity results in a bias in the EPM indicated cracklength of about 0.2 mm (0.008 inches). Smaller changes in the electrical resistivity of other alloys have been measured which rank as EN52> X-750> 304SS> nickel. It has been shown that these resistivity changes occur during exposure to high temperature water or inert gas. Strategies to minimize the effects of these two phenomena on EPM measurement are discussed.

Physical Description

7 p.

Notes

OSTI as DE99001883

Source

  • 8. international symposium on environmental degradation of materials in nuclear power systems-water reactors, Amelia Island, FL (United States), 10-14 Aug 1997

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  • Other: DE99001883
  • Report No.: KAPL-P--000146
  • Report No.: K--97009;CONF-970832--
  • Grant Number: AC12-76SN00052
  • DOI: 10.2172/319836 | External Link
  • Office of Scientific & Technical Information Report Number: 319836
  • Archival Resource Key: ark:/67531/metadc680655

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  • August 1, 1997

Added to The UNT Digital Library

  • July 25, 2015, 2:20 a.m.

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  • May 16, 2016, 6:23 p.m.

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Thompson, C.D.; Carey, D.M. & Perazzo, N.L. Effects of hydrogen on electropotential monitoring of stress corrosion crack growth, report, August 1, 1997; Schenectady, New York. (digital.library.unt.edu/ark:/67531/metadc680655/: accessed April 25, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.