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GA 1 - 2 - 3 - 4 - AP 1 - 2 - 3 - 4 - 5 - NT 1 - 2 - 3 - 4 - 5 - 6Vol.1No.2
Vol.1, No.1, NT6 EJAM - IHSI (Induction Heating Stress Improvement) Preventive Maintenance Technique for Primary Loop Recirculation Piping

IHSI (Induction Heating Stress Improvement)
Preventive Maintenance Technique for Primary Loop Recirculation Piping

 
TOSHIBA CORPORATION
 

KEYWORDS:
SCC, PLR piping, austenitic stainless steal, sensitized zone, stress improvement, IHSI

 
1. Technical summary
 
Classification
(I: Inspection, II: Repair, III: Replacement, IV: Preventive Maintenance, V: Others)
 
The outer surface of an objective pipe is heated with high frequency induction heating in order to induce temperature difference through the thickness of the heat effective zone of the pipe with simultaneous water cooling of inner surface. Through this process, residual stress in the inner surface is improved for compression by induced thermal stress.
Figure1 Figure2
Fig. 1 Concept of IHSI Fig. 2 Stress, Deformation and Temperature Distributions Induced by IHSI

 

 
2. Scope

(1) Components
-Stainless steel piping and nozzle/safe-end such as BWR PLR (Primary Loop Recirculation) Piping
-Nickel base Alloy nozzle/safe-end
(2) Objective Location
SCC Sensitized zone of the pipe base metal near the weld
(3) Materials
Austenitic stainless steel and Nickel base Alloy

 
3. Features

(1) Prevent initiation of SCC crack at the sensitized zone by stress improvement near the weld of pipe inner surface
(2) This technique is applied under the air condition with cooling water inside the pipe
(3) This technique is adopted after the pipe installation

Figure3
Fig. 3 Residual Stress Distribution on the Inside Surface
Along the Axial direction of the Piping
(Typical Groove)
Figure4
Fig. 4 Residual Stress Distribution on the Inside Surface
Along the Axial direction of the Piping
(Narrow Groove)
 
4. Examples of Application

(1) This technique was applied to BWR PLR piping.
(2) Same process was applied to BWR nozzle/safe-end weld.

Figure5

Fig. 5 Field Application of IHSI

 
5. Reference
(1) Teruaki Sato, Kazuyoshi Yonekura, Satoshi Hongo, Shoji Hayashi and Hideyo Saito,”Introduction of Repair/ Maintenance Techniques for SCC in Primary Loop Recirculation System Piping”, Maintenology,Vol.3,No.3(2004)
(in Japanese). (in English)
 
6. Contact
Japan Society of Maintenology (ejam@jsm.or.jp)