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Title: NDE Reliability Issues for the Examination of CASS Components

Abstract

The relatively low cost and corrosion resistance of cast austenitic stainless steel (CASS) materials resulted in their extensive use for piping systems in nuclear power plants (NPPs). However, CASS component welds are among the most challenging volumetric examinations required to be performed for detection of potential service degradation. Effective and reliable inspection methods for CASS materials are essential to achieving the objectives of defense-in-depth. A complicating issue is the presence of thermal aging embrittlement, a known degradation mechanism that occurs in CASS NPP materials. Further, while not as yet reported in CASS, many unforeseen instances of cracking in safety-related piping system welds have been experienced in other austenitic materials. Currently, a performance-based method to qualify NDE in CASS is not available. Pacific Northwest National Laboratory (PNNL) has performed nondestructive examination (NDE) research under the sponsorship of the U.S. Nuclear Regulatory Commission (NRC) for over four decades. A primary objective of the research has been to assess the effectiveness and reliability of conventional and advanced NDE methods for the inspection of light-water reactor components. One of the tasks being performed within this framework is to evaluate state-of-the-art technical approaches for examining safety-related nuclear reactor components that pose significant challenges to traditionalmore » NDE methods. A specific area of research in this regard is the volumetric examination of coarse-grained weldments and base materials. This report summarizes, compiles, and assesses relevant investigations performed by PNNL and other domestic and international organizations for welds adjacent to CASS components to provide a comprehensive evaluation on this subject. The primary objectives of the report are to assess the overall feasibility for advanced NDE methods to reliably and effectively examine field CASS piping components and to determine if techniques similar to those described in existing standards could be applied to develop performance demonstration requirements for CASS piping components. This report discusses improving the reliability of CASS examinations through the use of advanced low-frequency phased-array techniques, coupled with other “best practice” examination parameters, and makes recommendations for consideration by NRC Staff regarding the development of effective performance-based qualifications for CASS weldments. In addition to the PNNL research documented here, over 230 historical and more recent publications have been reviewed in the development of this document. The report is expected to be a useful resource for engineers and scientists involved in NDE of CASS for purposes of inservice inspection on existing plants during current and extended periods of operation. Finally, researchers and NDE practitioners conducting future investigations to advance the state-of-the-art should find the information contained in this report to be beneficial.« less

Authors:
 [1];  [2];  [2];  [2];  [2];  [2];  [3]
  1. Washington University
  2. BATTELLE (PACIFIC NW LAB)
  3. U.S. Nuclear Regulatory Commission
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1564083
Report Number(s):
PNNL-28840
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
Cast Austenitic Stainless Steel (CASS), nondestructive examination (NDE), structures, U.S. Nuclear Regulatory Commission’s, analysis

Citation Formats

Jacob, R E., Crawford, Susan L., Moran, Traci L., Larche, Michael R., Prowant, Matthew S., Diaz, Aaron A., and Nove, Carol A. NDE Reliability Issues for the Examination of CASS Components. United States: N. p., 2019. Web. doi:10.2172/1564083.
Jacob, R E., Crawford, Susan L., Moran, Traci L., Larche, Michael R., Prowant, Matthew S., Diaz, Aaron A., & Nove, Carol A. NDE Reliability Issues for the Examination of CASS Components. United States. doi:10.2172/1564083.
Jacob, R E., Crawford, Susan L., Moran, Traci L., Larche, Michael R., Prowant, Matthew S., Diaz, Aaron A., and Nove, Carol A. Mon . "NDE Reliability Issues for the Examination of CASS Components". United States. doi:10.2172/1564083. https://www.osti.gov/servlets/purl/1564083.
@article{osti_1564083,
title = {NDE Reliability Issues for the Examination of CASS Components},
author = {Jacob, R E. and Crawford, Susan L. and Moran, Traci L. and Larche, Michael R. and Prowant, Matthew S. and Diaz, Aaron A. and Nove, Carol A.},
abstractNote = {The relatively low cost and corrosion resistance of cast austenitic stainless steel (CASS) materials resulted in their extensive use for piping systems in nuclear power plants (NPPs). However, CASS component welds are among the most challenging volumetric examinations required to be performed for detection of potential service degradation. Effective and reliable inspection methods for CASS materials are essential to achieving the objectives of defense-in-depth. A complicating issue is the presence of thermal aging embrittlement, a known degradation mechanism that occurs in CASS NPP materials. Further, while not as yet reported in CASS, many unforeseen instances of cracking in safety-related piping system welds have been experienced in other austenitic materials. Currently, a performance-based method to qualify NDE in CASS is not available. Pacific Northwest National Laboratory (PNNL) has performed nondestructive examination (NDE) research under the sponsorship of the U.S. Nuclear Regulatory Commission (NRC) for over four decades. A primary objective of the research has been to assess the effectiveness and reliability of conventional and advanced NDE methods for the inspection of light-water reactor components. One of the tasks being performed within this framework is to evaluate state-of-the-art technical approaches for examining safety-related nuclear reactor components that pose significant challenges to traditional NDE methods. A specific area of research in this regard is the volumetric examination of coarse-grained weldments and base materials. This report summarizes, compiles, and assesses relevant investigations performed by PNNL and other domestic and international organizations for welds adjacent to CASS components to provide a comprehensive evaluation on this subject. The primary objectives of the report are to assess the overall feasibility for advanced NDE methods to reliably and effectively examine field CASS piping components and to determine if techniques similar to those described in existing standards could be applied to develop performance demonstration requirements for CASS piping components. This report discusses improving the reliability of CASS examinations through the use of advanced low-frequency phased-array techniques, coupled with other “best practice” examination parameters, and makes recommendations for consideration by NRC Staff regarding the development of effective performance-based qualifications for CASS weldments. In addition to the PNNL research documented here, over 230 historical and more recent publications have been reviewed in the development of this document. The report is expected to be a useful resource for engineers and scientists involved in NDE of CASS for purposes of inservice inspection on existing plants during current and extended periods of operation. Finally, researchers and NDE practitioners conducting future investigations to advance the state-of-the-art should find the information contained in this report to be beneficial.},
doi = {10.2172/1564083},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {9}
}