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Re[2]: Fwd:RE: Question RE <Working Level>
The last time I looked, I seem to remember the assumed detriment
from exposure to 4 WLM (from ICRP 32) being comparable to the
assumed detriment of 5 rem from ICRP 26/30, which is still the
basis for NRC/DOE regulations in the U.S. The ratio of these two
exposure or dose values is (5 rem / 4 WLM) or 1.25 rem per WLM.
In those jet-setting countries of the world where new
recommendations (like ICRP 60, etc.) are incorporated into
regulation with blistering speed, the detriment above (with some
changes to what is included in definition of detriment) is NOW
associated with 2 rem (or 20 mSv, in their new-fangled
terminology). Thus, the ratio changes to (20 mSv / 4 WLM), or 5
mSv per WLM.
I don't recall seeing anything that says this relationship between
WLM and rem (or Sv) is truly dosimetrically accurate; it is instead
more of a convenient ratio between "apples and oranges" to assist
in determining compliance with regulatory limits.
I know this is a simplification, and if it's too far off, I welcome
corrections from those who are more knowledgable than I.
Vincent King
vincent.king@doegjpo
_____________________________ Reply Separator _________________________________
Subject: Re: Fwd:RE: Question RE <Working Level>
Author: Mike Dempsey <mdempsey@lanl.gov> at Internet
Date: 1/12/99 4:25 PM
I'm not so sure about the strange units... I think that 4 WLM equals 5
REM. It was set up this way to track the exposure of uranium miners per quater.
Mike Dempsey
At 11:24 AM 1/12/99 -0600, you wrote:
>I agree with you on the Robley Evans article; it is one of my favorite
>references on the subject of radon. The full reference is "Engineers'
Guide to
>the Elementary Behavior of Radon Daughters," Health Physics 17:229-252,
>1969. In
>Evans' article it states that "the WL unit was introduced in 1957 by the USPHS
>.." and that it is a term employed in the United States and Canada. Leave it
>to us Americans once again to develop strange non-SI units and try to inflict
>them on everyone else!
>
>ICRP 32 and ICRP 47 are also good references to have on the shelf.
>
>> I would hate to think that a WLM to dose conversion factor would be based
>on a
>negotiation, but strange things happen. <
>
>Me too, Charlie. When I started working here we used 1000 mrem/WLM & 330
>mrem/WLM for Rn-222 and Rn-220, respectively -- now it's 1250 mrem/WLM & 420
>mrem/WLM. But that's DOE; I'm not sure what others assume.
>
>Elizabeth Algutifan,
>Environmental Health Physicist
>Elizabeth_Algutifan@wssrap-host.wssrap.com
>
>
>____________________Forward Header_____________________
>Subject: RE: Question RE <Working Level>
>Author: <radsafe@romulus.ehs.uiuc.edu>
>Date: 1/12/99 10:32 AM
>
>The dosimetry of radon-222 and its progeny is one of the most complex
>problems in radiation protection. In spite of much research, it has never
>been unequivocally solved. Radon is simply a radioisotope generator. The
>short lived progeny of radon deliver the dose. How much dose and where it
>is delivered depend on many factors such as the concentrations of daughters
>inhaled, aerosol particle size distribution, free ion fraction of the
>progeny, how the progeny are inhaled (nose vs mouth breathing), etc.
>Correlation of dose with radon concentration is further complicated by the
>deposition (plate out) of progeny on surfaces - particularly
>electrostatically charged surfaces.
>The literature is full of references on this subject, but some of the more
>useful ones may be NCRP 78, FRC Report 8, and a very useful article by R. D.
>Evans with a title something like "An Engineer's Guide to the Behavior of
>Radon Daughters" in Health Physics journal in the mid 1970s.
>The Evans article gives an excellent derivation of the working level (WL).
>The key to the derivation is that the WL is defined as "ANY concentration of
>short lived radon daughters in one liter of air that can produce an emission
>of 130,000 MeV of POTENTIAL alpha energy." A quick "do it yourself" guide
>to deriving the 130,000 is as follows: (1) Calculate the number of atoms of
>Po-218, Pb-214, Bi-214, and Po-214 when each is present at 100 pCi of
>activity. (2) Calculate the total POTENTIAL alpha energy contributed by
>each of these four: (a) Multiply Po-218 atoms by the sum of Po-218 and
>Po-214 alpha energies per disintegration and (b) multiply Pb-214, Bi-214,
>and Po-214 atoms by the Po-214 alpha energy. (3) Sum the total products
>obtained in (2) and round to two significant figures.
>Short-term, real-time measurements of airborne progeny have been made by
>many techniques for counting air filters including multiple alpha counts,
>alpha spectroscopy, alpha and beta counting, and various combinations of
>these.
>This message is much longer than I intended, but this is a complex subject
>that has defied simple answers. Hope this helps.
>Bill Goldsmith
>Wagoldsmith@mindspring.com
>
>-----Original Message-----
>From: radsafe@romulus.ehs.uiuc.edu
[mailto:radsafe@romulus.ehs.uiuc.edu]
>On
>Behalf Of Ivor Surveyor
>Sent: Tuesday, January 12, 1999 2:47 AM
>To: Multiple recipients of list
>Subject: Question RE <Working Level>
>
>Dear Radsafe,
>
>I wonder if anybody be kind enough to help me with some questions on the
>definition of <working level>.
>
>Epidemiological studies on Radon and its progeny use a unit called <working
>level>.
>
>I understand that is a historical unit, but is still very much favored by
>some epidemiologists.
>
>I am interested to know the origin of the unit.
>How did the definition 1.3 x 10E5 Mev/L of alpha energy arise?
>How did the original workers measure this quantity? Or intend it to be
>measured?
>Is it necessary to assume a form of secular equilibrium between radon and
>its progeny in order to use the unit?
>
>I read that 1 WL corresponds to a Rn-222 concentration of approximately
>100pCi/l or 3.7Bq/l, and/or 7.5 pCi/ or 277mBq/l of Rn-220. Are these neat
>conversions just a coincidence?
>
>I have also read 1 WLM corresponds to an equivalent dose of 10 mSv, but
>the Olympic Dam mine in South Australia uses the conversion 1 WLM = 5 mSv.
>ICRP 90 (B126) page 138. Points out that the complex relationship between
>dose to target tissue and concentration in WLM. Matters such as the
>aerodynamics of particles, breathing patterns and biological characteristic
>of lungs, the lung model used etc.
>I note that ICRP gives a conversion to the tracheobronchial region of
>between 4 to 13 mGy per WLM.
>
>This raises two further questions.
>
>In any given industrial site is the conversion of WLM to equivalent dose a
>compromise based on management, worker negotiation?
>
>Is variation in conversion from WLM to mSv a problem in comparing findings
>from different epidemiological sources?
>
>I hope these question are not considered to be too simplistic.
>
>
>
>
>
>
>
>Ivor Surveyor [isurveyor@vianet.net.au]
>Emeritus Consultant Physician,
>Department of Nuclear Medicine
>Royal Perth Hospital.
>
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