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	A New Mechanical Condition-based Maintenance Technology Using Instrumented Indentation Technique
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Vol.1, No.1, NT5 EJAM(1-1-NT5) - Internal Polishing Preventive Maintenance Technique for Primary Loop Recirculation Piping

Internal Polishing
Preventive Maintenance Technique for Primary Loop Recirculation Piping

TOSHIBA CORPORATION

KEYWORDS：
SCC, PLR piping, austenitic stainless steel, sensitized zone, stress improvement, polishing, whetstone

1. Technical summary

Classification
(I: Inspection, II: Repair, III: Replacement, IV: Preventive Maintenance, V: Others)

In this technique, inner surface of a pipe is polished in order to improve residual stress. Through the process, residual stress just near the inner surface removes to compression and SCC crack initiation is prevented.


(1)	(2)

Fig. 1 Improvement of Surface Residual Stress and SCC Prevention by Internal Polishing

Fig. 2 Sample of whetstone

2. Scope

(1) Components
Stainless steel piping/components such as BWR PLR (Primary Loop Recirculation) piping
(2) Objective Location
SCC Sensitized zone of the pipe base metal near the weld
(3) Materials
Austenitic stainless steel

3. Features

(1) Prevent initiation of SCC crack at the sensitized zone.
(2) This technique is applied under the air condition.
(2) This technique is adopted at the installation of piping/components (construction or replacement).

Fig. 3 Improvement of Surface Residual Stress and SCC Prevention

4. Examples of Application

(1) This technique was applied to BWR PLR piping.
(2) Same process has been applied to other components such as nozzle safe-end and Reactor Internals made of stainless steel.

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)
(2) Kaneo Takamori et al, ”SCC Crack Initiation and Propagation of Low Carbonized Stainless Steel in High Temperature Pure Water”, Maintenology, Vol.3,No2(2004),( in Japanese).

6. Contact

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


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