[ RadSafe ] dose values reported in Japan continue to beconfusing

Sun Mar 20 16:29:36 CDT 2011

Thanks, Ed.  Lots of us know this, but as they say "practice makes perfect".  I'll never be perfect.  Confident maybe...  The feeling that comes with what you know can't ever be replaced.  At least not for me.

Dan McClung
Dept of Veterans Affairs
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----- Original Message -----
From: radsafe-bounces at health.phys.iit.edu <radsafe-bounces at health.phys.iit.edu>
To: The International Radiation Protection (Health Physics) Mailing List <radsafe at health.phys.iit.edu>
Sent: Sun Mar 20 17:12:15 2011
Subject: Re: [ RadSafe ] dose values reported in Japan continue to beconfusing

To Jeff and all who sometimes struggle,

Yes, those of us not trained from the start of our careers on Systeme
Internationale (SI) units, such as Sieverts and Grays, but rather on the
"classic" rem/rad/roentgen system will likely continue to struggle with the
conversion.  Textbook definitions aside (e.g., one Gray = one joule/Kg of
absorbed dose), I believe that all of us in the nuclear professions develop
an intuitive "feel" for comprehending any situational exposure and dose
data, or any other parameters that we use to assess quantitative data. Our
reference basis for assimilating reported data tends to fall back to our
initial education and training, and our experience implementing that
training in practical situations.

For instance, a supposed background radiation level (exposure rate) reading
of 200 uR/hr tells me that something is likely up.  Yes, it could still be
natural, depending on the geology and altitude of the locale, but having
performed many surveys in areas where typical background ranges from 5-20
uR/hr, I intuitively know that the situation warrants further
investigation.  If the data is presented to me in nanoSv/hr, well sorry,
Dude, but I'm going to have to convert.  This is a little like only
understanding a foreign language by having to translate what is said in
one's mind, rather than just instantaneously thinking in that language.

That said, and finding old habits most comfortable, herewith is my rule of
thumb for quickly converting between SI and "classic" exposure and dose
units.

Given that the conversion for the basic unit of dose equivalent is one
Sievert = 100 rem, then to convert from any quantity of Sieverts or Grays to
rems or rads, respectively:
1) multiply the given number by 100*,*
2) keep the unit prefix the same, and
3) substitute the classic units for the SI ones*.*

For example, citing a recently much reported example from Fukushima,
converting an equivalent dose rate of 100 milliSieverts per hour to the
Rem/hr domain, multiply 100 X 100 = 10,000, keep the milli prefix, and
substitute rems for Sieverts.  The result, of course, is 10,000 millirems
per hour, or 10 rems/hr.  To convert in the other direction (such as from
rems to Sieverts), simply divide the given number by 100, keep the prefix,
and substitute the desired units.

Classic units are like classic rock, or classic Coke, or...maybe not
(humor).  Hope this helps.

Carl Ed Johnson Jr.
Not affiliated.
cejjr56 at gmail.com

On Sat, Mar 19, 2011 at 8:12 PM, Jeff Terry <terryj at iit.edu> wrote:

> Sieverts and rem are by far the absolute worst conversions for me, so I can
> understand why CNN would have trouble.
>
> The factor of 100 just seems metric. It just isn't a conversion factor like
> 454 g per lb, 1.06 qts per l, and 2.54 cm per inch.  You can't see a dose so
> you have to remember which one is bigger. Since the rem numbers were drilled
> into my head, all of the factors of 10 from milli to micro still hurt when
> dealing with this and you just don't want to be off by an order of
> magnitude. 1 mrem/day still makes far more sense to me that 10 uSv/day.
>
> Then take into account the language translation and the translation to
> chest x-rays, it is amazing that anyone gets this correct.
>
> Sorry, but I have to go and find a few 5/32" screws for a project that I am
> working on.
>
> REM forever ; )
>
> This last week has caused me to do more sievert/rem conversions then I have
> had before, not too mention sievert/chest x-ray conversions. Amazingly, it
> is finally starting to register.
>
> Best,
>
> Jeff
>
>
> Jeff Terry
> Asst. Professor of Physics
> Life Science Bldg Rm 166
> Illinois Institute of Technology
> 3101 S. Dearborn St.
> Chicago IL 60616
> 630-252-9708
> terryj at iit.edu
>
>
>
>
> On Mar 19, 2011, at 8:42 PM, Perle, Sandy wrote:
>
> > The posting below was posted to the wearing subject, so I've started a
> new
> > subject line. Sorry about that.
> >
> > -----------------------------------
> > Sander C. Perle
> > President
> > Mirion Technologies
> > Dosimetry Services Division
> > 2652 McGaw Avenue
> > Irvine, CA 92614
> >
> > +1 (949) 296-2306 (Office)
> > +1 (949) 296-1130 (Fax)
> >
> > Mirion Technologies: http://www.mirion.com/
> >
> >
> >
> >
> >
> > On 3/19/11 6:39 PM, "Perle, Sandy" <SPerle at mirion.com> wrote:
> >
> >> From the latest CNN report out of Tokyo:
> >>
> >> "Six members of the emergency crew at the plant have been exposed to
> >> more than 100 millisieverts of radiation per hour, the equivalent of
> >> getting 10 chest X-rays per hour, plant owner Tokyo Electric Power
> >> Company said.
> >>
> >> Tokyo Electric had raised the exposure level for emergency workers from
> >> its previous standard of 100
> >> millisieverts per hour to 250 millisieverts."
> >>
> >> I never heard of any chest x-ray where you get 10 per hour with a dose
> of
> >> 100 mSv!
> >>
> >> Where do they get their stuff? Are they simply oblivious to the dose
> units
> >> they're reporting? Now if they said 100 mrem per bour, I could see a
> chest
> >> x-ay of 10 mrem each.
> >>
> >> Regards,
> >>
> >> Sandy
> >
> >
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