Re: Re[2]: Technical Basis Documents

[Keith Welch <welch@CEBAF.GOV>]

At 06:44 PM 9/22/96 -0500, you wrote:

>Units are important.
>
>There is a principle in math and science that the denominator is "unitized"
>as you make reference.  The 100 cm^2 is not a unit area, cm^2 is.....
>
>
>Pardon my ignorance, but didn't the 100cm^2 area eventuate due to the fact that
>contamination probes typically had an acvtive area of about 100cm^2 when
>monitoring for contamination directly?


OK, Ok, Units are important.  "that may have been what I said, but what I
meant was..."  There is no difference between 10 dpm/cm2 and 1000
dpm/100cm2.  Yes, when we sit down to do calculations it makes it convenient
to have everything in compatible units, but how often are we handed a real
life situation where we don't have to make conversions during the process of
calculation??  We're talking grade school math here.  I just think we're
puting too much emphasis on the color of the measuring stick rather than the
size of what we're measuring.  Yes, I suppose we are making all good
mathematitions cringe by not reducing our fraction, but the purpose of using
100 cm2 in the reporting is to represent the fact that we measured the
contamination over an area of 100 cm2 NOT over an area of one cm2.  In other
words, the reported value also says something about the process or method of
the assessment.  Why we don't say decimeter .... Idunno. 

It was suggested that among other reasons, "political friendliness" would be
a good reason for using dpm/cm2, because it has a smaller number attached.
I do not agree with this premise.  We have enough credibility problems
without being accused of trying to make things sound "better" than they are.
(If we use Bq. we're sunk if we are concerned with this - wow! a
Giga-becquerel)  I do think that we should use units that allow for the
representation of the data using ordinary numbers.  For instance, use Ci,
uCi, pCi, (or Bq, MBq..) to keep from having to use huge powers of ten.
(i.e. Don't call a 10 Ci source a 10,000 millicurie source)

Alex,  I don't think the original (and still standard) common probes for
contamination monitoring really see a 100cm2 area, but I may be wrong.  Has
anybody done or heard of an assessment of this??  If you hold a pancake
probe over a surface, how much active surface area is really measured?

Keith Welch
Thomas Jefferson National Accelerator Facility
Newport News VA
welch@cebaf.gov