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Title: Technical Letter Report on Crack Growth Rate Testing on Alloy 600 Nozzle Sections from the Replacement Pressure Vessel Head at Davis-Besse Reactor.

Authors:
; ; ;  [1]
  1. (Nuclear Engineering Division)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USNRC
OSTI Identifier:
1137188
Report Number(s):
ANL-12/2
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Technical Report
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Alexandreanu, B, Chen, Y., Natesan, K., and Shack, W.J. Technical Letter Report on Crack Growth Rate Testing on Alloy 600 Nozzle Sections from the Replacement Pressure Vessel Head at Davis-Besse Reactor.. United States: N. p., 2014. Web. doi:10.2172/1137188.
Alexandreanu, B, Chen, Y., Natesan, K., & Shack, W.J. Technical Letter Report on Crack Growth Rate Testing on Alloy 600 Nozzle Sections from the Replacement Pressure Vessel Head at Davis-Besse Reactor.. United States. doi:10.2172/1137188.
Alexandreanu, B, Chen, Y., Natesan, K., and Shack, W.J. Tue . "Technical Letter Report on Crack Growth Rate Testing on Alloy 600 Nozzle Sections from the Replacement Pressure Vessel Head at Davis-Besse Reactor.". United States. doi:10.2172/1137188. https://www.osti.gov/servlets/purl/1137188.
@article{osti_1137188,
title = {Technical Letter Report on Crack Growth Rate Testing on Alloy 600 Nozzle Sections from the Replacement Pressure Vessel Head at Davis-Besse Reactor.},
author = {Alexandreanu, B and Chen, Y. and Natesan, K. and Shack, W.J.},
abstractNote = {},
doi = {10.2172/1137188},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jul 01 00:00:00 EDT 2014},
month = {Tue Jul 01 00:00:00 EDT 2014}
}

Technical Report:

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  • Cracks in Alloy 600 and Alloy 182 upper-head-penetration welded components from the Davis-Besse pressurized-water reactor were characterized by high-resolution analytical transmission electron microscopy. Axial cracks in the Alloy 600 nozzle and both axial and circumferential cracks in the weld metal were examined at scales ranging from mm to less than 1 nm. Despite different metallurgical structures in the wrought nozzle and weld alloys, the observations in both materials revealed characteristic penetrative intergranular attack and corrosion products indicating that the degradation occurred by intergranular stress corrosion cracking (IGSCC) during service. Sulfur impurities and sulfide particles found near crack tips in themore » Alloy 600 nozzle also indicated that the IGSCC in this material was assisted by impurities from the primary-water environment.« less
  • No abstract prepared.
  • Stress corrosion crack (SCC) growth rate tests and analytical electron microscopy (AEM) studies were performed over a broad range of environments and heat treatments of Alloy 600. This effort was conducted to correlate bulk environmental conditions such as pH and electrochemical potential (EcP) with the morphology of the SCC crack. Development of a library of AEM morphologies formed by SCC in different environments is an important step in identifying the conditions that lead to SCC in components. Additionally, AEM examination of stress corrosion cracks formed in different environments and microstructures lends insight into the mechanism(s) of stress corrosion cracking. Testingmore » was conducted on compact tension specimens in three environments: a mildly acidic oxidizing environment containing sulfate ions, a caustic environment containing 10% NaOH, and hydrogenated near-neutral buffered water. Additionally, stress corrosion cracking testing of a smooth specimen was conducted in hydrogenated steam. The following heat treatments of Alloy 600 were examined: mill annealed at 980 C (near-neutral water), mill annealed at 1010 C (steam), sensitized (acid and caustic), and mill annealed + healed to homogenize the grain boundary Cr concentration (caustic). Crack growth rate (CGR) testing showed that sensitized Alloy 600 tested in the mildly acidic, oxidizing environment containing sulfate ions produced the fastest cracking ({approx} 8.8 {micro}m/hr at 260 C), and AEM examination revealed evidence of sulfur segregation to the crack tip. The caustic environment produced slower cracking ({approx} 0.4 {micro}m/hr at 307 C) in the mill annealed + healed heat treatment but no observed cracking in the sensitized condition. In the caustic environment, fully oxidized carbides were present in the crack wake but not ahead of the crack tip. In near-neutral buffered water at 338 C, the CGR was a function of dissolved hydrogen in the water and exhibited a maximum (0.17 {micro}m/hr) near the transition between Ni and NiO stability. The cracks in near-neutral hydrogenated water exhibited Cr-rich spinels and NiO-type oxides but no significant oxidation of grain boundary carbides. No clear effect of dissolved hydrogen on the crack wake morphology was apparent. In hydrogenated steam testing of a smooth specimen (CGR estimated as {approx} 0.7 {micro}m/hr at 399 C), metallic nickel nodules were evident in both the crack wake and on the specimen surface. Oxide particles having a similar size and shape to the microstructural carbides were found in the crack wake, suggesting that these particles are carbides that were oxidized by contact with the steam. The present results show that different environments often produce unique crack tip morphologies that can be identified via AEM.« less
  • In the fall of 1991 a leak was reported to have occurred at a CRDM head penetration at a plant in France. This occurred during hydro-testing. The root cause of the cracking was identified as primary water stress corrosion cracking (PWSCC). The head penetrations in most PWR plants throughout the USA, Asia, and Europe use Alloy 600 materials, and one of the key issues to be dealt with is the rate at which stress corrosion cracks are predicted to grow. The crack growth rate in these head penetrations is affected by both the head penetration temperature and material microstructure. Thismore » growth rate is a key element of the safety case for the head penetrations. When this test program began in 1992, there were several published studies on this subject, but all the test specimens were thin-walled tubes, deformed into flat plates. This testing program was initiated to provide a predictive capability for the head penetrations, based on tests of the penetration material itself. Since this program began, other programs have begun in other laboratories, and the results obtained thus far are reviewed and compared with results of this program in Section 5.2. The results of this program and the others are expected to provide a more correct technical basis for the crack growth rates used in predicting crack extension of head penetrations in service. This report provides an updated status to the original report, published in October, 1993. In this revision, all crack growth data obtained during the past year have been included, along with microstructural results and discussion of the trends observed.« less