Doors

Within the battery limits of the CVŘ contract there are four big hot cells, designated ECA, ECC, ECD, and ECR and three small hot chambers marked ECS, ECE, and ECM, see the figure below. Technological service entrances are scheduled to lead from the small cells to the big ones, using the sealed and shielded sliding doors. Next to the small cells there are two transfer spaces (SAS) providing operators with the service entrance into the cell from their room. Sealed shielded revolving doors are foreseen to interconnect the transfer spaces with the cell and granting access to transfer spaces. Entrance to the big cells from the level of the rear service zone is through the heavy, air-sealed door, moving on the rail tracks. It is complicated to open this door, which therefore usually remains closed, except for the rare exceptional situations.

All the doors form a part of the dynamic containment with hot cells, and must therefore meet, apart from other parameters, full tightness being subject to regular pressure testing in the future. Doors of all the types must withstand earthquakes and comply with the SI class of seismicity and all the requirements for the operation control system.

Hot cells layout

1. Hinged doors  –  small cell / transfer room
2. Sliding doors  –  big cells / small cells
3. Aperture
4. Hinged doors  –  transfer room / front zone of small cells
5. shafts with lifting support
6. Sealing trapdoor of vertical connection in cell ECR
7. Biological doors in pool

DOOR TYPES

SLIDING DOORS

Shielded sliding door between the big and small cells is an assembly of four sliding doors riding on the continuous bottom and top rail tracks. The main weight-bearing item is an assembly of the bottom bogie; the vertical positioning is kept by two sets of top support. To ensure radiation safety there are a filling from lead bricks and polyethylene panels. The door itself consists of a bearing frame, inner shielding panels (lead + polyethylene panels) and cover sheets. The door is held upright by action of its top guide along with the top support. Motion of each of the doors is provided by the rotary trapezoidal screw assembly, driven by motor, via a gearbox. The door can be power-operated or hand-operated via a manual drive. The drive is coupled to the second shaft, led out of the motor. Both the motor and manual control unit are available in SAS, behind the door-fitted cover. End positions of the doors – “open“ and “closed“ are

indicated by the end-switch assemblies with negative logics. Service and emergency end positions of the doors are being sensed. A motor-driven lock is there to hold the doors in their closed positions. A pneumatic drive that can also be manually operated with the remote manipulator is there to propel the lock.

HINGED DOORS

The revolving doors grant access to SAS from the front zone and to small cells from SAS. Two of them are available in the front zone, other two in SAS of the ECE/ECS cells one in the ECM cell’s SAS. This layout will necessitate one left-side door and four right-side doors (see schematic diagram above). Door controls and indicators are located on the cell control panels. Clear height of the passage is selected in respect of the ECA, ECC, ECD, and ECR cells’ sliding doors clear height. The passages will allow passage of a maintenance crab with suspended heavy manipulator. Doorframes form a part of the frame buried in concrete. To seal off the doors, there is an inflatable Ω-shaped seal which is – complete with the anchorage accessories – a part of the doorframes. The valves and pressure gauges in the sealing form a part of the shared pneumatic distributor for the small cells.

HEAVY DOORS

(CVŘ is only in charge of the design, but the delivery of the airtight doors itself is within the responsibilities of AREVA)

The big cells are made accessible from the area of the rear service zone through a heavy airtight door, which consists of the heavy concrete door and alpha door. This rides on the rails in the hot cells’ rear zone, granting – upon rare occasions – access to the cell and allowing replacement of bulk equipment. Gauge of the rails is 950 mm. Heavy doors are identical for all the big cells. An additional shielding is fitted on the cold side of the door at the floor level, reaching ca 30 cm above it. The alpha door makes the big cells accessible for a routine transfer of samples and other materials. Its design is proprietary, allowing connection of capsules with irradiated material without radiation leaks.