[ RadSafe ] Adopting the International System of Units for Radiation Measurements in the United States: Proceedings of a Workshop

Ted de Castro tdc at xrayted.com
Mon Mar 6 10:53:56 CST 2017

Did the workshop have anything to say about the rampant misuse of units 
afforded us by SI?

Thanks to an incredibly cumbersome EXPOSURE unit - regulatory exposure 
limits are now being expressed in DOSE units without specifying - dose 
to what.

Back in the back old days when we where just too stupid to know any 
better these things were expressed in exposure units.  When a DOSE unit 
was expressed - rad - it was expressed as rad in xxxx. And was seldom 
measured but usually calculated.

So I recently encountered a quasi regulatory document called SEMI 2 
which has among other things:

"Direct doserate measurement with an Ion Chamber {or equivalent) calibrated
to +/- 10% of true doserate at the surface of the equipment (or at the 
approach) in all areas where the operator may have access with the ionizing
radiation source active.*"

*Sorry - wrong!  An ion chamber is an exposure instrument NOT dose rate 
- and this is for analytical x-ray for which the spectrum from one end 
to the other varies considerably and the exposure to dose ratio is 
spectrum dependent and will vary more than the requisite 10% from one 
end to the other.  Let along the body part to which their dose limits 
apply is not specified.  (they give the limits in Sv) I maintain there 
is in fact no survey instrument that can measure this!

So - with their use of SI and misuse of type of unit we are confronted 
with a published imperative which is clearly impossible to comply with.

So - what did the workshop have to say about ion chambers with Sv marked 
on the meter faces?

On 3/3/2017 5:51 AM, Jason Meade wrote:
> It was a great workshop and well worth my time, but after it was done, I'm
> pretty sure it will be done again with almost an identical agenda in 10
> years time.
> Entirely too much "but this is the way we've always done it" and "it would
> be too hard" type talking among those who've always been doing the work and
> who are largely in charge for any type of shift in thinking, despite the
> fact that the majority of the scientific and academic portions of our
> education system have already made the change.
> On Thu, Mar 2, 2017 at 11:38 AM, Cary Renquist <cary.renquist at ezag.com>
> wrote:
>>  From the National Academies Press.
>> One can always download the PDF version for free (might require an account)
>> Adopting the International System of Units for Radiation Measurements in
>> the United States: Proceedings of a Workshop
>> Most countries in the world use the SI (Système International, also known
>> as the metric system) units for radiation measurements in commercial and
>> technical activities. The United States, in contrast, uses a mix of SI and
>> conventional units for radiation measurements, despite 30-year-old national
>> and international recommendations to exclusively use SI. Radiation
>> professionals in the United States are faced with the need to understand
>> both systems and make conversions between the two.
>> Short link
>> http://bit.ly/2mPP5bQ
>> Adopting the International System of Units for Radiation Measurements in
>> the United States: Proceedings of a Workshop | The National Academies Press
>> <https://www.nap.edu/catalog/24645/adopting-the-
>> international-system-of-units-for-radiation-measurements-in-
>> the-united-states?utm_source=NASEM+News+and+Publications&
>> utm_campaign=b2788914c1-Final_Book_2017_03_02_24645&utm_
>> medium=email&utm_term=0_96101de015-b2788914c1-102196093&goal=0_96101de015-
>> b2788914c1-102196093&mc_cid=b2788914c1&mc_eid=3ee8f719d6>
>> ---
>> Cary Renquist
>> cary.renquist at ezag.com
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