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Special Article: The Great Tohoku Earthquake (1)
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Information
ICMST-Kobe 2014
Nov 2(Sun) - 5(Wed), 2014
Kobe, Japan
Nuclear Regulation Authority Outline of the New Safety Standards for Light Water Reactors for Electric Power Generation
For Public Comment
Outline of New Safety Standard (Design Basis)
For Public Comment
New Safety Standards (SA) Outline (Draft)
For Public Comment
Outline of New Safety Standard(Earthquake and Tsunami)(DRAFT)
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  Vol.5 No.4(Feb-25)
Vol.5 No.3(Nov-25)
Vol.5 No.2(Aug-26)
Vol.5 No.1(May-27)
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Featured Articles
EJAM5-3NT58 "Development of Future Prediction of Animation by coupling of Principle Component Analysis and Singular Spectrum Analysis"
EJAM5-3NT58 Validation of Multifrequency and Window-Multifrequency Techniques using Remote Field Eddy Currents for ISI of FBR Tubes
EJAM5-3NT59 Remote Controlled Robot with expandable features

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Contacts
(EJAM): ejam@jsm.or.jp
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(in English)

 
Vol.1 No.1 ← GA 5 - AP 6 - 7 - NT 7 - 7(1) - 7(2) - 8 - 9Vol.1No.3
Vol.1, No.2, NT7

Water Jet Peening
Technology for Preventing Stress Corrosion Cracking
by Using Cavitations

 
Hitachi-GE Nuclear Energy, Ltd.
Mitsubishi Heavy Industries, Ltd.
 

KEYWORD:
water jet, peening, stress improvement, SCC, reactor internals EJAM (1-2-NT7) - Water Jet Peening - Technology for Preventing Stress Corrosion Cracking by Using Cavitations

 
 
 
Classification
(I: Inspection, II: Repair, III: Replacement, IV: Preventive Maintenance, V: Others)
 
What is WJP?
EJAM1-2-NT1-Fig.1_Mechanism_of_residual_stress_improvement_with_WJP

Fig. 1 Mechanism of residual stress improvement with WJP

Water Jet Peening (WJP) is a kind of peening methods using cavitations and is known as one of the most successful underwater peening methods to the reactor internals in BWRs (Boiling Water Reactors) and PWRs (Pressurized Water Reactors) in Japan. It is known that causes for Stress Corrosion Cracking (SCC) are categorized into three and SCC potential can be mitigated by removing or reducing at least one of the three; aggressive environment, susceptible material and tensile stress. WJP reduces residual tensile stress and puts the surface and near-surface layer in high compression to mitigate SCC potential.

A schematic mechanism of residual stress improvement with WJP is shown in Figure 1. When highly pressurized water is injected into water through a WJP nozzle, the high-speed water jet generates cavitations. The cavitations in the water jet collapse after a moment, then the intensive pressure wave is generated by the collapse. By controlling the parameters shown in Figure 2 so that the collapse happens on the metal surface optimally, compressive stress appears on the surface because plastic deformation generated by the intensive pressure wave is elastically constrained by surrounding metal.

EJAM1-2-NT7-Fig.2_Essential_variables_of_WJP_(Parameters to be controlled).png

Fig. 2 Essential variables of WJP (Parameters to be controlled)

For More about WJP...

[Vol.1 No.2 NT7(1)] "The Water Jet Peening for Reactor Internals Technology for Preventing Stress Corrosion Cracking by Using Cavitations"

EJAM1-2-NT7(2)-_NT7(1)_Fig2_Water jet peening to the BWR reactor internal

(EJAM Vol.1 No.2 NT7(1) Fig. 1)

[Vol.1 No.2 NT7(2)] "WATER JET PEENING AS RESIDUAL STRESS IMPROVEMENT METHOD FOR ALLOY 600 PWSCC MITIGATION"

Vol.1No.2NT3Figure5

(EJAM Vol.1 No.2 NT7(2) Fig.5)

Contact
Japan Society of Maintenology (ejam@jsm.or.jp)