scholarly journals Susceptibility to Severe PWSCC (primary water stress corrosion cracking) of LTMA (low temperature mill anneal) Alloy 600

2020 ◽  
Vol 58 (12) ◽  
pp. 815-821
Author(s):  
Sung Soo Kim ◽  
Jung Jong Yeob ◽  
Young Suk Kim
Keyword(s):  
Water Stress ◽  
Low Temperature ◽  
Stress Corrosion Cracking ◽  
Short Range ◽  
Alloy 600 ◽  
Lattice Contraction ◽  
Short Range Ordering ◽  
Mill Anneal ◽  
Primary Water ◽  
Kinetics Of

It has been proposed that a primary water stress corrosion cracking (PWSCC) in pressurized water reactor (PWR) is governed by a lattice contraction due to a short range ordering reaction in Alloy 600. This leads researcher to think that the kinetics of lattice contraction may control a susceptibility of PWSCC in Alloy 600. A lattice variation with ordering treatment at 400 <sup>o</sup>C was systematically investigated using high resolution neutron diffraction(HRPD) in high temperature mill anneal (HTMA), low temperature mill anneal (LTMA), and sensitized (SEN) Alloy 600. The results showed that ordering treatment caused an isotropic lattice contraction due to short range ordering (SRO) reaction. The lattice contractions of (111) plane are saturated to be 0.04% in 4 to 1500 hours at 400 <sup>o</sup>C according to prior treatment condition. The lattice contraction in the magnitude of 0.03% of (111) plane in LTMA Alloy 600 is faster by 8 times and 66 times than that of SEN and HTMA, respectively. This fact may explain why the LTMA is most susceptible to PWSCC through of kinetics of lattice contraction in Alloy 600. Thus, it is possible to conclude that the susceptibility of Alloy 600 to PWSCC is governed by the kinetics of (111) lattice contraction.

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.

Effects of Dissolved Hydrogen on the Primary Water Stress Corrosion Cracking Behavior of Alloy 600 at 325 °C

2004 ◽  
Vol 261-263 ◽  
pp. 943-948 ◽  
Author(s):  
Q.J. Peng ◽  
Tetsuo Shoji
Keyword(s):  
Water Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Experimental Results ◽  
Alloy 600 ◽  
Pressurized Water ◽  
Cracking Behavior ◽  
Primary Water ◽  
Dissolved Hydrogen

Primary water stress corrosion cracking (PWSCC) of Alloy 600 has been a great concern to the nuclear power industry. Reliable PWSCC growth rate data, especially at temperatures in the range of 290-330°C, of the alloy are required in order to evaluate the lifetime of power plant components. In this study, three tests were carried out in simulated pressurized water reactor (PWR) primary water at 325°C at different dissolved hydrogen (DH) concentrations using standard one-inch compact tension (1T-CT) specimens. The initiation and growth of cracks as well as insights into the different PWSCC mechanisms proposed in the literature were discussed. The experimental results show that the detrimental effects of hydrogen on crack initiation and growth reached a maximum at a certain level of DH in water. The experimental results were explained in terms of changes in the stability of the surface oxide films under different DH levels. The experimental results also support the assumption that hydrogen absorption as a result of cathodic reactions within the metal plays a fundamental role in PWSCC.

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