Loop Plugs

Preferred Engineering Loop Plugs have been used for various PWR nozzle isolation requirements. Designed to isolate both Hot and Cold legs the Preferred Loop plugs offer reliable nozzle isolation with minimal protrusion from the vessel wall. Our Loop Plugs are engineered for manual actuation which eliminates complicated installation tools and minimizes moving components. Dual seals offer redundant isolation with maximum conformance to clad nozzle surface variability.


  • Positive and passive compression Seal – requires no external air or hydraulic pressure to create and maintain a seal.
  • Plug Seal is actuated by simple manual torqueing from the refuel floor.
  • Secondary Inflatable seal provides redundant isolation.
  • The Plug includes a vent hose to the refuel floor.
  • The nozzle/piping can be back-filled by the Plug backfill valve to allow cavity water to fill pipelines.
  • The Plug stainless steel parts are electro-polished to facilitate decontamination.
  • All Plug parts and fasteners are secured to prevent FME.
  • Optional - The piping downstream of the Loop Plug can be drained by remote pumping into the cavity.