ICMST-Tohoku 2018
Oct. 23 - 26, 2018
Sendai, Japan
ICMST-Shenzhen 2016
Nov 1 - 4, 2016
Shenzhen, China
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)

Vol.10 No.2(Aug)
Vol.10 No.1(May)
Vol.9 No.4(Feb)
Vol.9 No.3(Nov)

< Other Issues


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

Featured Articles
EJAM7-3NT72 A New Mechanical Condition-based Maintenance Technology Using Instrumented Indentation Technique
EJAM7-3NT73 Survey robots for Fukushima Daiichi Nuclear Power Plant

(in English)

Vol.1 No.1 NT.4 (May, 2009) Sheet A
Preventive Maintenance and Repair for PLR Piping EJAM(1-1-NT4-SheetA) Preventive Maintenance and Repair for PLR Piping

In recent years, cracks due to stress corrosion cracking (here-after it is called SCC) have been found in many pipes of the primary loop recirculation systems(here-after PLR) of boiling water reactor(here-after BWR).

Their pipes were made of low carbonized stainless steel (SUS316(LC)). Formerly, it was thought that SCC due to sensitizing never took place, if the material was carbonized lower. However, afterwards from investigations of actually used materials and experiments it became clear that if the metal surface became hard, inner-granular SCC sensitivity increased and the crack propagates as inter-granular SCC in the simulated BWR environmental water.

According to the above-mentioned investigations and experiments, the SCC mechanism for low carbonized stainless steel is as follows:

As the first step, inner-granular SCC initiates and propagates to the depth of surface processed zone in the section where stress level is high and cracking sensitivity increases due to hardness increase by surface processing. As the second step, the crack can propagate as inter-granular SCC, depending on stress and chemical conditions at the crack tip.

It is well known that SCC initiation depends on combination of three factors such as material, environment and stress. Accordingly, it is effective to reduce the influence of these three factors in order to prevent SCC.

Repair and preventive techniques of mitigation for materials and residual stress of PLR piping against SCC are mainly as follows:

  1. CRC : Corrosion Resistant Cladding
  2. Internal Polishing
  3. IHSI : Induction Heating Stress Improvement
  4. SHT : Solution Heat Treatment
  5. HSW : Heat Sink Welding
  6. Weld Overlay
Japan Society of Maintenology (