PART 192–HEALTH AND ENVIRONMENTAL PROTECTION STANDARDS FOR URANIUM AND THORIUM MILL TAILINGS–Table of Contents

Subpart B–Standards for Cleanup of Land and Buildings Contaminated with
Residual Radioactive Materials from Inactive Uranium Processing Sites

Remedial actions shall be conducted so as to provide reasonable
assurance that, as a result of residual radioactive materials from any
designated processing site:
(a) The concentration of radium-226 in land averaged over any area
of 100 square meters shall not exceed the background level by more than-
-
(1) 5 pCi/g, averaged over the first 15 cm of soil below the
surface, and
(2) 15 pCi/g, averaged over 15 cm thick layers of soil more than 15
cm below the surface.
(b) In any occupied or habitable building–
(1) The objective of remedial action shall be, and reasonable effort
shall be made to achieve, an annual average (or equivalent) radon decay
product concentration (including background) not to exceed 0.02 WL. In
any case, the radon decay product concentration (including background)
shall not exceed 0.03 WL, and
(2) The level of gamma radiation shall not exceed the background
level by more than 20 microroentgens per hour.

Here is the entire document

http://edocket.access.gpo.gov/cfr_2002/julqtr/40cfr192.12.htm

and the source of the entire set of law

http://www.access.gpo.gov/nara/cfr/waisidx_02/40cfr192_02.html

Were this used in the granite industry, one fifth to one sixth of the stones would have to be pulled from the market. I have seen the ICRP comments on “Optimization of Radiological Protection” where some wonder why use different standards on NORM, TENORM, and other nuclear industry products.

Al

Thanks for the comments and info. Great to see some movement on the issues.

True, Dr. Hans is way off on his estimate of where the radiation is coming from according to your data and the info from the Houston granite countertop. By a factor of hundreds! And this guy is a Geologist serving the natural stone industry? Looks like he tells em what they want to hear.

“Twenty microRems per hour is written as 20uR/hr. ”

When learning the terminology and units of this field, it took a while to get the differences between the units straight. After doing so, I ran across several experts that said the units could be used interchangably for our purposes, crudely at least, for Gamma in dry air or Alpha for external exposure. To keep the confusion down to readers not used to the units, I use millirem instead of the more correct milliroentgen.

Here is one of the references to this practice

“Note: The units of R, rad, and rem can sometimes be acceptably interchanged. For instance, for gamma radiation, and exposure of 1 R causes an absorbed dose in a person of about 1 rad, which results in a dose equivalent of 1 rem. This is due to the basis for the definitions of the units and the relative biological effectiveness of gamma radiation. An absorbed dose of 1 rad from fast neutrons, however would result in a dose equivalent of about 10 rem. ”

Since we tend to concentrate on measuring Gamma emitted from the granite countertop slabs, I use the terms interchangably to prevent further confusing newcomers to the discussion.

But, you are 100% correct in pointing out the difference. Thanks.

We have the references for the quote on EPA and some state agencies using 20 uR/hr as a remediation level for rooms, homes, or buildings. I will get them to you ASAP.

Thanks again, welcome to the discusssion. Glad to have an expert on board.

“Dr. Hans Hensen claims that most of the radiation in granite countertops comes from Potassium 40 ( K 40), in fact most of the radiation comes from Radon and Thorium.”

from the stones i’ve looked at the Uranium ore is the major player. i see less than
a 1% contribution from 40-K. the longer-lived Radon (the one people mean
they say “radon”, half life ~4 days) is in the 238-U series. the 232-Th series also produces a “radon” called “thoron” but that guy has a very short half-life.

“So there it is, even the EPA says that the radiation risks are unknown…… ”

not a mistake in your post – just wanted to mention that i intend to change
this. i have now ~40 samples from 3 stone yards and several private
individuals that i will investigate with my NaI(Th) spectrometer.
i intend to publish. Journal of Environmental Radioactivity or something
like that.

“Twenty microRems per hour is written as 20uR/hr. ”

20 uR/hr is 20 micro-Roentgens per hour, not 20 micro-rem/hr.

the latter (rem) is the unit of absorbed dose. it is the product of the dose
(in Roentgens) and a “quality factor”. this quality factor accounts for
the different amount of damage (”biological efficiency”) that different particles can do to human tissue.
the quality factor for gammas and betas is one, and it’s 20 for alphas.

in the sense that *external* alpha radiation generally poses little risk
(typical 1-2 MeV alphas have a range of only 1-2″ in air, and less than
the thickness of a single piece of paper, and they
are absorbed in the dead-layer of skin called the epidermis) then it’s not
heinous to mix mR and mrem. but your geiger counters are measuring
mR, not mrem, because they do not and cannot know what the particles
are.

my gamma spectrometer does though! also, your geiger counters are
generally underestimating the true fluence, especially for energies above
1 MeV, due to their known (in)efficiency as a function of the particle and
energy. this too is something that i can correct for with my NaI setup
to get the “true” fluence…

BTW the use of the unit “rem” is not strongly discouraged by NIST, although
when i undergo my yearly radiation retraining as part of my day job, the
unit mrem is still used. and it is very common elsewhere.

“Without going into a lot of detail on this topic, EPA and some State agencies have used an exposure of 20 microR/hour as a remediation action level for entire rooms, homes or buildings.”

i’d love to have references for that comment!

cheers,
bill