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Core Shroud Replacement Work

Purpose of Core Shroud Replacement

It is vitally importance to maintain the stable operation of Nuclear Power Plants now, and well into the future. The discovery of core shroud cracking in the BWR in 1990 led to heightened awareness and enhanced shroud inspection programs worldwide. This inspection initiative revealed that Stress Corrosion Cracking (SCC) of core shroud was becoming an issue for the entire BWR industry.

SCC is caused by the proper combination of Material, Residual Stress and Water Chemistry. Tokyo Electric Power Company decided to replace the core shroud with the more SCC resistant 316L material for the preventative maintenance of their plants.


Toshiba has developed and established the Core Shroud Replacement Method as the complete countermeasure. In doing so, Toshiba has therefore, developed the shroud replacement method and machines, including Chemical Decontamination, Shroud Support Machining, Shroud Welding and other technologies.

Core Shroud

Core Shroud

Construction of RPV

The core shroud is the cylindrical stainless steel structure in the Reactor Pressure Vessel (RPV) that surrounds the fuels, control rods and other core components (reactor core). The core shroud directs cooling water flow through the jet pumps, into the bottom head region and up through the reactor core.

Shape of Core Shroud

Shape of Core Shroud

The core shroud is a cylinder that surrounds the reactor core. The top guide and core plate rest on the shroud to provide horizontal support for the fuel assemblies.

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