Re: VENTILATION AS BARRIER FOR AIRBORNE AREA

[joseph guido <jguido@poky.srv.net>]

Jackson_R_Ellis@rl.gov wrote:
> 
>      I am revisiting this topic because I believe I was not specific enough
>      about the geometry of the situation.  Several suggested using the
>      heavy plastic strips found on grocery refrigerated compartments that
>      would provide separation while still allowing equipment passage.
>      Others commented that such a large opening meant the two rooms were a
>      single airspace so a barrier that provides a complete seal and a DP of
>      up to 1 inch of water was needed.
> 
>      A top view is provided below.  Hopefully this didn't get chewed by the
>      long distances WEB travel.
> 
> 
> 
>                              ~860'
>      |--------------------------------------------------------------------|
>      |                                                                    |
>      |        15'                                                         |
>      |       |---|                                                        |
>      |       |   |                                                        |
>      |       |   |28'                                                     |
>      |       |---|                                                        |
>      |                                                                    |
>      |                                                                    |
>      |--------------------------------------------------------------------|
> 
>      The 25' X 28' opening is in the floor of the ~860' long larger room
>      (canyon).  The second room is below the opening on a lower level
>      (tunnel).  We wish to remove airborne rad area status from the tunnel
>      room.  You can now see refrigerated compartment plastic strips are not
>      an option.
> 
>      On the subject of using a solid barrier that provides a DP of up to 1"
>      of water:  The canyon room is an airborne area due to decontamination
>      activities approximately 300' - 400' away from the opening.  The
>      smaller room has no history of receiving contamination from that
>      activity.  The tunnel exhausts through the opening to the canyon room.
> 
>      We do not want to put a "golden line" down in the canyon room that
>      denotes the farthest distance airborne contamination will travel in an
>      open room (yet).  Workers traverse the length of the canyon room, so
>      separate controlled zones would mean dress/undress stations.  But, we
>      do want to consider the smaller room a separate airspace.  This
>      situation does not warrant a solid barrier (the requirement from DOE
>      RadCon Manual says "where practical."  However, I would like have a
>      ventilation barrier to ensure that airborne contamination (to the
>      extent that would produce 10% DAC) does not enter the tunnel room.
>      Does anyone know of a flow rate (or velocity) that is required?
> 
>      I apologize for the length of this message, but my last attempt to
>      abbreviate left out needed details.
> 
>      Thanks for your time.
> 
>      Jackson_R_Ellis@rl.gov

Seems like the key here is to maintain the tunnel at a higher pressure than the canyon so that 
leakage is from the tunnel into the canyon.  Additionally, if you were to set up the ventilation 
so that the exhaust from the canyon was at the end where the decontamination efforts are taking 
place, you could also sweep the air from the tunnel into the canyon and towards the airborne end. 
 I am not sure if this helps since it is likely that the ventilation is already set up in the 
areas you describe.  

joe guido