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Design & System Configuration

Improved Control Rod Drive Mechanism and RCP Seal

“Canopy-seals” have traditionally been adopted in the Control Rod Drive Mechanism (CRDM) housing designs so that the latching assembly can be easily replaced on-site in the event of a failure. Over the years, however, canopy-seals have exhibited a susceptibility to stress corrosion cracks. To overcome this problem, Mitsubishi has developed a reliable design against leakage that still allows the removal of the latching assemblies on-site. This new design is currently applied to replaceable vessel heads.

This improved, cartridge type seal has been introduced to improve the maintainability of reactor coolant pumps. The large face plate design enhances sealing capability and improved materials are applied to O-rings. The service life of the seal has been extended through improvements in the design and material specification. The performance and integrity have been duly verified by full flow tests in the MHI facility.