Cavity Seal System

The Preferred Engineering Cavity Seal System consists of segmented EPDM extrusions custom made for the reactor annulus. We use a series of polished Stainless-Steel cover plates with pairs of stainless steel J-bolts and cam actuated toggle nuts compress each seal. Our system requires no torque measurements, and the seal compression can be immediately verified by use of a feeler gauge.


  • The toggle nuts include visual indicators allowing for fast and accurate verification of actuated/unactuated status.
  • Able to be installed in 60-75 minutes by 2-3 RXS technicians
  • J-Bolt leak test allows for immediate verification of seal through J-Bolt prior to flood up.
  • Robust EPDM Seal sections can be individually inspected and replaced as needed.