Re: Day/Night background change?

[presley.j@atomcon.gc.ca]

     Radsafers,
     
     There is another phenomenon which shows up
     in the northern climes from time to time
     which is also related to Radon and its progeny.
     
     At times during the middle of winter in Canada we might 
     experience a warm spell of say 60 Deg F or so. (really !)
     
     But, of course, this is short-lived (T-1/2=12 h) and may be 
     accompanied by a rapid drop to below freezing with accompanying 
     freezing rain.
     
     Without getting into all of the details, the net effect is that
     the warming of the ground enhances the Radon emanation from the
     soil which is then trapped in the snow/ice by the crust from
     the frozen rain. Now anyone who walks or drives over this crust
     will end up with tires/shoes mildly contaminated with Radon progeny.
     
     This causes a stir usually once a year at most Ontario 
     nuclear plants when all of a sudden the tires of trucks trying to 
     leave the facility are reading about 1000 cpm on a contamination
     meter. Until one of the "old-timers" is contacted to remind
     everyone of the origin of the "contamination".
     
     Any plants in the US ever see this ?
     
     Jim Presley
     presley.j@atomcon.gc.ca