Search

Occasional Topics
OTjapan Measures for Tsunami Striking Nuclear Power Station in Japan
Special Article: The Great Tohoku Earthquake (1)
OTjapan The Tragedy of “To Be” Principle in the Japanese Nuclear Industry
EJAMOT_CN3_Figure1_The_outside_view_of_CEFR OTChinaPlanning and Consideration on SFR R&D Activities in China
< All Occasional Topics

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)
Issues
  Vol.5 No.4(Feb-25)
Vol.5 No.3(Nov-25)
Vol.5 No.2(Aug-26)
Vol.5 No.1(May-27)
< Other Issues

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

JSM
Contacts
(EJAM): ejam@jsm.or.jp
(JSM): secretariat@jsm.or.jp
HP: http://www.jsm.or.jp
(in English)

 
Vol.1 No.2 ← GA 6 - 7 - AA 8 - 9 - NT 10 - 11 - 12 - 13Vol.1 No.3
Vol.1, No.3, NT13 EJAM (1-3-NT13) - Crack Removing Method for Repair of Reactor Internals

Crack Removing Method for Repair of Reactor Internals

 
Hitachi-GE Nuclear Energy, Ltd.
 

KEYWORDS:
SCC, electric discharge machining, reactor internals, core shroud, shroud support

 
1. Technical summary
 
Classification
(I: Inspection, II: Repair, III: Replacement, IV: Preventive Maintenance, V: Others)
 
This is a repairing method for SCC (stress corrosion cracking) of reactor internals. In this method, existing SCC cracks are completely removed under water by using electric discharge machining (EDM) or grinding,
EJAM1-3-NT13-Fig.1(small)_EDM_method EJAM1-3-NT13-Fig.2(small)_Grinding_method
EDM method (Sheet A) Grinding method (Sheet B)
2. Scope

(1) Components
BWR and PWR core internals. Core shroud, shroud support, for example

(2) Materials
Both base metal and weld of austenitic stainless steel and high nickel alloy

(3) Condition
This method can only be applied to location where the necessary structural strength is ensured by the remaining portion after removal of cracks.

 
3. Features

・Machining head for removing crack is positioned precisely according to the result of eddy current test (ECT) for the crack.

・Crack growth is stopped by removal of cracks completely. In addition, peening treatment or other stress improvement is performed and initiation potential of SCC cracks is reduced.

 
4. Examples of Application
Crack removing equipments for inner and outer surface of core shroud have been developed.

This technique was applied to many BWR core shrouds in Japan.
 
5. Reference
M.Tanaka, T. Itou, T. Yamamoto, A. Mori, M. Makino, “Introduction of repair and Maintenance Technology against SCC in core shroud” Maintenology, Vol.3, No.3, (2004) (in Japanese)
 
6. Contact
Japan Society of Maintenology (ejam@jsm.or.jp)