Assessment of Eddy Current Testing for the Detection of Cracks in Cast Stainless Steel Reactor Piping Components (NUREG/CR-6929)

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Publication Information

Manuscript Completed: November 2006
Date Published: February 2007

Prepared by:
A.A. Diaz, R.A. Mathews,
J. Hixon¹, S.R. Doctor

Pacific Northwest National Laboratory
Richland, WA 99352

D.A. Jackson and W.E. Norris, NRC Project Managers

Prepared for:
Division of Fuel, Engineering and Radiological Research
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code Y6604

¹Visiting Intern - U.S. Nuclear Regulatory Commission
Division of Fuel, Engineering and Radiological Research
Office of Nuclear Regulatory Research

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Abstract

Studies conducted at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington, have focused on assessing the effectiveness and reliability of novel approaches to nondestructive examination (NDE) for inspecting coarse-grained, cast stainless steel reactor components. The primary objective of this work is to provide information to the U.S. Nuclear Regulatory Commission (NRC) on the utility, effectiveness, and reliability of advanced NDE methods as related to the inservice inspection of primary piping components in pressurized water reactors. This report describes progress, recent developments, and results from the assessment of eddy current testing (ET) for detection of surface-breaking cracks in cast stainless steel (CSS) reactor piping components from the inside surface of the pipe wall. In assessing the ET inspection technique, PNNL used a range of specimens from four different sources:

• cast stainless steel pipe segments with thermal and mechanical fatigue cracks (Westinghouse Owners Group)

• specimens containing thermal fatigue cracks (PNNL)

• a blank spool piece from a Spanish nuclear plant (loaned by the Electric Power Research Institute NDE Center)

• three smaller segments of highly coarse-grained blank spool pieces (Southwest Research Institute)

• a blank spool piece of vintage cast stainless steel on loan from Westinghouse

• a blank spool piece of vintage cast stainless steel on loan from IHI Southwest Technologies Inc.

Eddy current studies were conducted on the inner-diameter surface of piping using a Zetec MIZ-27SI eddy current instrument and a Zetec C Z0000857-1 plus-point spot probe with an operating frequency of 250 kHz. To reduce noise effects, a subset of the CSS specimens was degaussed, resulting in noticeable improvements. In this report, results from laboratory studies for assessing detection, localization, and length sizing effectiveness are provided, and issues and anticipated future work are discussed.