Air Locks: Main Air Lock & Auxiliary Air Lock

  •    NPCIL
  •    Kakrapara 3 &4
  •    4 sets
  •    Nuclear Division


These Air Locks are designed to provide leak tight passage between the Reactor Building (RB) and the Reactor Auxiliary Building (RAB). They permits movement of personnel and materials/ components/equipment between the two buildings without disrupting the integrity of the reactor containment system.

Three doors are provided, in line with the double containment principle. This ensures that ground activity release is practically zero in the event of a release of activity in RB during Loss of Coolant Accident (LOCA) or any other accident.

Each assembly set of doors consists of a bigger door, called equipment door, and a smaller door, called personnel door. The personnel door is included in the corresponding equipment door (i.e. door-in-door). The three assemblies of doors divide the barrel into two airtight compartments when their doors are closed, locked and sealed by inflating EPDM/neoprene rubber seals mounted on them.

Construction details

  • Material: SA 516 Gr 70
  • Dimensions: Equipment door - 3m x 3m / Personnel door - 1.5m x 2m

Critical aspects

  • The RB side door set and Intermediate door set were tested at 1.84 kg/cm2(g) for integrity and 0.8 kg/cm2(g) for leak rate test.
  • RAB side door set was tested at 0.07 kg/cm2(g) for integrity and leak rate test.
  • The pneumatic test pressure of APCS and ASCS was 1.84 kg/cm2(g) and 0.07 kg/cm2(g) respectively.