Procedure for an EF1 Failure

by Anne Trudel, Aug. 29, 2006

Measurements were undertaken to assess the extent of air activation buildup in the BL2A tunnel under normal beam operation with the exhaust fan EF1 off. The purpose of the measurements was to determine if beam operation could continue for a period of several days in this mode, or whether beam operation had to cease and the fan repaired before resumng operation.

EF1 only exhausts the BL2A tunnel air. The South end of the tunnel has an opening to a 1/2-metre diameter tunnel for the BL2A beam pipe coming from the 500MeV cyclotron vault. The opening is completely sealed around the beam pipe, thus limiting air flow between the tunnel and the vault. The opening is completely sealed around the beam pipe, thius limiting air flow between the tunnel and the vault. The North end of the tunnel abuts against the solid concrete wall of the ISAC Maintenance Hall. All penetrations are sealed to maintain the required zoning for the hall. The entrance to the tunnel from the Mechanical Services Room is a solid door.

The test with EF1 turned off was conducted over a three-day period with 35 µA of proton current on a zirconium carbide target at the ITW target station. During the test periodic air samples were taken at the area safety unit on the B2 level at ISAC, immediately outside the Mechanical Services Room. This is the nearest occupied area to the BL2A tunnel. No air activation products were observed in this area throughout the duration of the test.

Immediately upon turning off beam a series of air samples were taken first in the Mechanical Services Room, and then the BL2A tunnel. Correcting for the decay time between the end-of-beam and the sample time, this corresponds to less than 0.01% DAC for air activation.

The measurements demonstrate that the buildup of air activation in the tunnel is negligible under normal operation for a period of three days with no direct ventilation. Therefore normal beam operation can safely continue for such a period of time. If access to the tunnel is required with EF1 offm air samples would need to be taken upon entry.