Lapel Air Sampling and Monitoring

[Robert.Morris@DOEGJPO.COM (Robert Morris)]

     Some time ago, when I suggested lapel sampling for plutonium workers 
     at Lawrence Livermore Lab, I remember being told that the only thing 
     you know for sure after counting a lapel air sample was that  the 
     activity on the filter was not in the person's lungs.  Actually there 
     is some truth to that when the airborne contaminant is associated with 
     high specific activity particles.  But sometimes less-than-ideal 
     information is better that any other alternative.  I think that is the 
     case with lapel air sampling for radionuclides.  I have found lapel 
     air sampling useful during outdoor tasks and in situations where 
     well-characterized local exhaust ventilation is not in use.  
     
     One major problem when using lapel air sampling for radionuclides is 
     finding personal pumps that move enough air to achieve required 
     detection limits.  The best I have been able to find are Buck Pumps 
     that pull nominally 7 to 8 Liters/minutes.  Another problem is the 
     filter holder.  Typical IH particulate cassettes are only 25-mm 
     diameter, so after several hours of sampling, the particle load is 
     thick and significantly absorbs alpha radiation.  Open-faced 47-mm 
     holders are normally made of metal and designed to be mounted on a 
     wall.  You can get a concussion by having one of those bounce up and 
     hit you in the forehead.  I have found plastic 47-mm in-line filter 
     holders from Millipore, after a machinist cut off the upstream cowl,  
     to be a good an open-faced holder.
     
     Someone else mentioned that there are no alarming personal monitoring 
     systems.  French-made Merlin Gerin Model MCA-11 (also known as the 
     "Monica CAM") is a belt-mounted pump that pulls air through a special 
     sampling head.  The sampling head looks like half of a softball 
     suspended around the neck on a lanyard.  The sampling head is designed 
     mechanically to separate sub-micron sized radon progeny from larger 
     particles assumed to be the ones of interest.  Air-stream patterns and 
     impaction do the separation.  A dual channel analyzer, surface barrier 
     detector measures in real-time and, in theory, alarms at 21 DAC-hours 
     for Pu-239.  If a false alarm occurs due to radon progeny 
     interferences, this will clear within a few minutes in a radon-free 
     atmosphere, so it is possible to make good field decisions about how 
     to interpret alarms.  Dr. J. Charuau published "Design and assessment 
     of a personal air monitor to optimize the occupational monitoring in 
     plutonium laboratories," in Proceedings of the DOE Workshop on 
     Workplace Aerosol Monitoring, Napa, CA, 1985.  Dowell Martz and I 
     published GJPO-M-008-91, "Evaluation of personal air sampler designed 
     to provide an early warning of plutonium exposure," and submitted it 
     for publication in the proceedings of a 1991 DOE workshop.  
     Unfortunately those proceedings were never published.  I have copies 
     that I can mail out.
     
     Robert Morris, CHP, CIH
     WASTREN-Grand Junction
     2597 B3/4 Road
     Grand Junction, CO 81503
     970/248-6704
     rmorris@gjpomail.doegjpo.com