[ RadSafe ] Radioactivity in Granite Countertops

[Stewart Farber]

Does anyone know if there some types of granite that contain NO enhanced
levels of natural radioactivity? This has never been my experience, but I'm
no geologist.

 

I've done studies with high-pressure ionization chambers in many places
showing clearly elevated levels of radioactivity contained in granite in
construction throughout the Northeastern US as indicated by elevated gamma
dose rates of 20 micro-R/hr [200 nSv/hr] or more  [ in close proximity to
granite walls -approx. 1 foot distant] vs. typical background dose rates  of
about 8 micro-R/hr [ 80 nSv/hr] for the area. 

 

Every HPIC measurement near granite I've made around Boston [ at the
Christian Science Church, South Station, Bunker Hill Monument, steps of the
MA Statehouse, granite Colonial era wharf buildings]  or all around
Westerly, RI [a town where almost every building is made of granite], or in
NH or Maine, or  the Harrisburg, PA Capitol granite steps,  has shown about
a doubling of background dose rate measured with a HPIC a  foot  or so from
the granite used in construction. 

 

Another interesting measurement was of a doubling of background dose rate
near a large piece of Aswan red granite from Egypt which was used to make a
sarcophagus for a princess many thousands of  years ago. This ancient
granite ceremonial Egyptian coffin is currently displayed in front of the
Boston, MA Museum of Science.

 

All  granite mentioned  above would show greatly elevated count rates when
measured on contact with a standard pancake GM like an Ludlum 44-9 or
HP-360.  

 

However, a friend has recently installed granite countertops which shows
background rad levels on contact. So has my friend purchased "real" granite
with all the  natural radioactivity it "should" contain or has she been
cheated of her little bit of residual elevated U-238, Th-232, and K-40
radioactivity from the Big Bang?

 

Thoughts?

 

 

Stewart Farber