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Vol.2 No.1 previous GA 13 - AA 15 - SP2 (16 - 17 - 18) - NT 23 - 24 - 25 next Vol.2 No.3
Academic Articles
Regular Paper (Invited) Vol.2 (2010) p.50 - p.64
 

Evaluation of Weld Residual Stress near the Cladding and J-weld in Reactor Pressure Vessel Head for the assessment of PWSCC Behavior
 
Jinya KATSUYAMA1,*, Makoto UDAGAWA1, Hiroyuki NISHIKAWA1,†, Mitsuyuki NAKAMURA1,‡ and Kunio ONIZAWA1
 
1Nuclear Safety Research Center, Japan Atomic Energy Agency, 2-4 Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan
 
Abstract
Weld residual stress is one of the most important factors in order to assess the structural integrity of safety-related components such as reactor pressure vessel (RPV) in long-term operation of nuclear power plant since the residual stress significantly affects crack initiation and growth behaviors. The inner surface of the RPV made of low alloy steel is protected against corrosion by weld-overlay cladding of austenitic stainless steel. At the J-weld of the vessel head penetrations, Ni-based alloys are used for weld material. The residual stresses generated within the cladding, J-weld and base material were measured as-welded and after PWHT conditions using the deep-hole-drilling method. Thermal-elastic-plastic-creep analyses considering the phase transformation were also performed to evaluate the weld residual stress. By comparing analytical results with the measured ones, it was shown that there was roughly a good agreement of residual stress distribution within the cladding, J-weld and base metal. It was also suggested that taking the phase transformation during welding and PWHT into account was important to improve the accuracy of weld residual stress analysis. Using the residual stress distributions, fracture mechanics analyses for primary water stress corrosion cracking (PWSCC) have been performed using probabilistic fracture mechanics analysis code. Effects of the weld residual stress and scatter of PWSCC growth rate on the crack penetration were evaluated through some case studies.
 
Keywords
weld residual stress, reactor pressure vessel, PWSCC, weld-overlay cladding, J-groove welding, deep-hole-drilling method, finite element analysis, structure integrity, crack growth
 
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Article history:
Received 20 May 2010
Accepted 21 July 2010