WG-C Aug. 21, 2007
Present: Osborne, Kuchler, Enomoto, Seryi, Maurice Ball, Garbincius, Tom Lackowski, Markiewicz, Sullivan, Keller, Parker, Bialowons, Huedem, Herve (+possibly, other colleagues)
Atsushi Enomoto presented questions and discussion of fire safety in baseline layout of IR hall. See slides.
For example: how to pass concrete shield wall in the hall. This should be done with pressurized tunnel going around the wall on the side of the hall.
An additional passage tunnel between beam tunnel near IR hall and the hall is needed, since beam-tunnel is now blocked in front of IR hall.
John Osborne: the rule in Europe is to have escape not further than 30m away. Would go to separated pressurized area where smoke would not enter. That is why suggested to place small passage tunnels around the IR hall, with as many doors as needed. Near each lift need to have pressurized room where people can wait (1m**2 per 3 people).
Lackowski: in Numi had to have two ways out. At base of elevator have enclosure for up to two hours waiting time.
J.O: CERN also have two hours waiting time, and two way out rule.
Question: is present baseline OK from fire safety since the end of service cavern have only one way to the shaft?
J.O: that is why suggested to move 9m shaft close to the end of service cavern.
T.L: In Minos the hall was downstream of the shaft. To create second way out, built a concrete corridor (enclosure) that became second way out to the elevator.
Comment: to make baseline OK for fire safety: need to move 9m shaft to the end of the service cavern and have small passage tunnels around the hall.
Radiation safety and escape through the beam tunnel in case of fire -- in this case beam is shut off and escape ignoring the remaining radiation. Should have masks with 30min supply of oxygen for everyone in the hall.
Ventilations for stairs, elevators and passages should be separate.
John Osborbne presented single shaft option. Advantages: cost saving and possibility to have normal work in the cavern while lowering the loads (have rule at CERN that nobody could be in the cavern when loading is done in LHC halls). The latter advantage is for planning and hard to quantify in terms of cost.
The layout includes increase of main single shaft from 16m to 18m, pressurized egress passages around the hall. There is also cost reduction for surface building due to single building, gantry crane and shaft cover.
Version with two large shafts offset from the main hall looks unfavorable from construction point of view since two nearby caverns will act as single one.
There is ongoing discussion about the width and height of the cavern: recent layout was shown by A.Herve in WG-A where the height was decreased from 39m by several meters, but hall was wider. (The width is still under discussion in WG-A).
There was a comment made earlier in WG-A that that if detector B (which is further away from the main single shaft) have major problem, like failure of solenoid that need to be replaced, then both detector have to be stopped to allow its repairs.
To that comment A.Seryi suggested that if such thing happens with detector B, the first likely decision would be to continue physics run with detector A, until all would be planned and prepared to remove the detector B to the surface, during planned summer shutdown (preparation included, e.g. to rent the gantry crane again, which could be remounted in 2 months). However such major problems as the need for solenoid exchange are very unlikely, while exchange of TPC should be foreseen to be done in the garage position.
Next week there will be a meeting as usual.
On Aug 29 there will be conveners and IPAC meeting to discuss Convener's plan and progress.
A.Seryi said that in this case
