Weldability, Thermal Aging and PWSCC Behavior of Nickel Weld Metals Containing 15 to 30% Chromium

2004 ◽  
Author(s):  
J. M. Boursier ◽  
F. Vaillant ◽  
B. Yrieix
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Thermal Ageing ◽  
Corrosion Cracking ◽  
Life Assessment ◽  
Alloy 600 ◽  
Head Penetration ◽  
Weld Metals ◽  
Alloy 690 ◽  
Primary Water

In 1991, a vessel head penetration was found leaking at Bugey 3 plant during the hydrotest. Metallurgical investigations confirmed that this problem was again related to primary water stress corrosion cracking of alloy 600. Moreover, the main crack initiated in the base metal of the penetration (alloy 600) has also propagated in the weld metal in alloy 182. More recently, stress corrosion cracking in alloy 182 has been found on welds of U.S. plants. SCC susceptibility of alloy 182 has been evidenced by several laboratories. In France, all original vessel heads using alloy 600 have been or will be replaced with penetrations in alloy 690 (with 30% chromium). With respect to substitution materials, ELECTRICITE´ DE FRANCE has undertaken a large R&D study focusing on the development of new weld metals. The aim of this study was to identify new materials that will be able to weld alloy 690. Weld metals containing 15 to 30% Chromium have been studied. This paper presents an overview of the main results obtained on 19% Cr, 26% Cr and 30% Cr alloys with respect to alloy 182 (15% Cr). Firstly, the weldability of weld metals has been studied focusing on the susceptibility to hot cracking. Secondly, the resistance to thermal ageing has been investigated in order to detect any long term ordering of the solid solution Ni-Cr that could induce embrittlement. Hardness tests, Charpy tests and resistivity measurements did not show any effect of ageing up to 60,000 hours at 360°C. Thirdly, stress corrosion cracking susceptibility in primary water at 360°C has been evaluated during constant load tests, RUB tests, slow strain rate tests. No cracking was observed on material containing more than 26% Cr for both initiation and propagation. Finally, a life assessment was performed for all weld materials with respect to alloy 182.

Stress Corrosion Cracking Incidents and Repair Technologies on PWR Dissimilar Weld Metal Joints in Japan

2010 ◽  
Author(s):  
Naoki Chigusa ◽  
Shinro Hirano ◽  
Takehiko Sera ◽  
Hitoshi Kaguchi ◽  
Masayuki Mukai ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Power Plants ◽  
Reactor Vessel ◽  
Corrosion Cracking ◽  
Alloy 600 ◽  
Maintenance And Repair ◽  
Head Penetration ◽  
Dissimilar Weld ◽  
Primary Water

Several Japanese PWR power plants have experienced Primary Water Stress Corrosion Cracking (PWSCC) on dissimilar weld joints since 2004. J weld of 3 Reactor Vessel Head Penetration in Ohi unit 3 is one of the PWSCC incidents occurred in 2004 and has been studied by sampling and opening the fracture surface after its repair. Including Ohi unit 3 Reactor Vessel Head Penetration repair, Japanese PWR utilities and MHI have been developing the preventive maintenance and repair technologies applicable to alloy 600 welds and base metal, following PWSCC events on the Bugey-3 and V.C. Summer. This paper describes recent Japanese PWSCC incidents and repair technologies developed in Japan.

Stress Corrosion Cracking (SCC) of Nickel-Base Weld Metals in PWR Primary Water

2013 ◽  
Vol 747-748 ◽  
pp. 723-732 ◽  
Author(s):  
Ru Xiong ◽  
Ying Jie Qiao ◽  
Gui Liang Liu
Keyword(s):  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Surface Condition ◽  
Cold Work ◽  
Corrosion Cracking ◽  
Pressurized Water ◽  
Weld Metals ◽  
Surface Residual Stresses ◽  
Primary Water

This discussion reviewed the occurrence of stress corrosion cracking (SCC) of alloys 182 and 82 weld metals in primary water (PWSCC) of pressurized water reactors (PWR) from both operating plants and laboratory experiments. Results from in-service experience showed that more than 340 Alloy 182/82 welds have sustained PWSCC. Most of these cases have been attributed to the presence of high residual stresses produced during the manufacture aside from the inherent tendency for Alloy 182/82 to sustain SCC. The affected welds were not subjected to a stress relief heat treatment with adjacent low alloy steel components. Results from laboratory studies indicated that time-to-cracking of Alloy 82 was a factor of 4 to 10 longer than that for Alloy 182. PWSCC depended strongly on the surface condition, surface residual stresses and surface cold work, which were consistent with the results of in-service failures. Improvements in the resistance of advanced weld metals, Alloys 152 and 52, to PWSCC were discussed.

Evaluation and Repair of Primary Water Stress Corrosion Cracking in Alloy 600/182 Control Rod Drive Mechanism Nozzles

2002 ◽  
Author(s):  
Charles R. Frye ◽  
Melvin L. Arey ◽  
Michael R. Robinson ◽  
David E. Whitaker
Keyword(s):  
Water Stress ◽  
Boric Acid ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Base Material ◽  
Corrosion Cracking ◽  
Alloy 600 ◽  
Control Rod ◽  
Drive Mechanism ◽  
Primary Water

In February 2001, a routine visual inspection of the reactor vessel head of Oconee Nuclear Station Unit 3 identified boric acid crystals at nine of sixty-nine locations where control rod drive mechanism housings (CRDM nozzles) penetrate the head. The boric acid deposits resulted from primary coolant leaking from cracks in the nozzle attachment weld and from through-thickness cracks in the nozzle wall. A general overview of the inspection and repair process is presented and results of the metallurgical analysis are discussed in more detail. The analysis confirmed that primary water stress corrosion cracking (PWSCC) is the mechanism of failure of both the Alloy 182 weld filler material and the alloy 600 wrought base material.

Sign in / Sign up

Export Citation Format

Share Document