[ RadSafe ] Rn-222, Solar heated homes, Public Unnderstanding. was: RE: Radioactivity in Granite Countertops NYT had anarticle on the topic
SAFarber at optonline.net
Tue Feb 28 12:58:50 CST 2012
As seen below my original question was about whether list members know of
any "granite" that contains radioactivity that is so low it cannot be seen
with a thin window GM survey detector like a 44-9. Dan McCarn was very
helpful on this point but any other feedback would be appreciated.
It is of course well known that granite countertops and granite in
construction present an interesting issue about trivial sources of low-level
exposure that might actually serve as a way to make people think and
understand a bit about radioactivity in the environment. For the record
there is a wealth of data on the migration of Rn-222 through solid rock
walls measured as part of radon mitigation in uranium mining.
Another interesting case of elevated Rn-222 release and exposure to
homeowners from granite is the situation seen with many forced hot air solar
heating systems. During the day, air is warmed by the sun incident on a
simple air transfer solar panel. Any excess heated air is then moved through
a heat storage reservoir typically of roughly 1" crush diameter [to get good
heat transfer] diameter granite. In many cases, since granite is so
ubiquitous and a cheap source of a crushed stone with a high heat capacity,
it is used in this type of passive solar heating. However, any locally
available stone has been used.
So any excess heat collected during the day is stored in the granite
[sometimes] rock heat storage reservoir. At night the heat is released to
the home by passing home air directly through the heat storage reservoirs.
The "heat storage reservoir" which is nothing more than an airtight box
through which to pass air from the solar panels, typically contains 80 to
100 tons [or more] of crushed stone. The Rn buildup in this situation inside
the reservoir which is released into the home can be quite surprisingly
elevated because the small diameter stone is able to release more Rn than a
solid slab of granite per gram of granite.
In a prior lifetime [1977- 1979], I was able to have fun and prompt some
studies of Rn inside some of the early solar homes in NH having forced hot
air solar systems. I saw a report on the NBC Today show about a "wonderful"
solar home just built in NH. After checking with some colleagues with the
NH Dept. of Health, I found that these single family homes contained large
[100 tons or so for a single home] heat storage granite reservoirs. After a
lot of calls in the background, I arranged for the NH Dept of Public Health
to work with the Environmental Measurements Lab [EML]. Dr. John Harley who
I had met some time before was interested in this situation when I asked him
about what the Rn release might be from a piece of granite 1" in diameter.
EML he said had never thought about making Rn measurements inside solar
homes [which were being built with very little air infiltration], or to get
inside some of these single family homes with granite heat reservoirs.
Dr. Harley agreed to approve his Radon Studies Group [which had developed
special expertise related to Rn releases from Uranium Mill tailing] to make
some measurements in some solar homes I might find for them.
After the initial group of Rn measurements inside a forced hot air solar
heated home [with 100 tons of crushed granite in their heat reservoir] ,
made in summer with open windows, the DOE EML came back to me and asked if I
could find some other homes to measure. The first home EML had gone into,
refused to let the researchers back in to make measurements during the
winter when the house would be tightly sealed up. The homeowner said that
this information "was inimical to the development of solar energy" and he
did not want people to know there was likely to be elevated levels of Rn-222
in some solar heated homes. As the homeowner felt: "Don't confuse me with
After a lot of calls, I was able to also speak to and get the DOE Solar
Development Group to cooperate with the DOE EML and get into a DOE Condo
complex in NH with a much larger granite heat storage reservoir since it was
serving many condos, not just one home, and had many more panels to capture
heat during the day and store it for nighttime use to serve the entire
At the time the DOE group promoting solar development, dragged its feet for
about a year in cooperating with another division of DOE [EML] to make the
field measurements of Rn. I remember the DOE Manager promoting solar
development telling me: "This is awful. How can there possibly be
radioactivity inside a solar home."
I had to go back to the Big Bang, the formation of radioactive heavy
elements, the U-238 decay series down to Ra-226 leading to Rn-222.
Fortunately, the DOE Solar Development group did in the end allow the Rn
measurements to be made. They deserve credit for cooperating a bit.
The data gathered is long buried in my papers but it would be interesting to
get more data of this sort from solar heated homes with forced hot air or
just in tightly sealed solar homes to see what levels of elevated Rn-222 are
As is obvious, it takes just a smidgen of elevated Rn-222 in a home and the
resulting WBDE to dwarf the incremental radiation exposure to the general
population from nuclear power electric generating stations.
Wouldn't it be great if we could find a way to "lay all the data on the
table" [preferably a nice flat granite table], as it were from nuclear,
reduced air infiltration from energy conservation, extreme cases like forced
hot air solar heating systems, unvented gas space heaters or gas
stoves/ovens [which cause elevated Rn in home air with many natural gas],
etc., etc., and discuss it so media, politicians, and the public could
begin to understand the issues exploited by anti-nuclear activists who have
been getting away with scaremongering for far too long.
Stewart Farber, MSPH
SAFarber at optonline.net
In a message dated 2/27/2012 1:41:57 P.M. Eastern Standard Time,
SAFarber at optonline.net writes:
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
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.......................
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