An extended harangue on SI prefixes (was re dental xrays)

[brian whatcott <inet@INTELLISYS.NET>]

At 00:12 12/29/00 -0500, Ludwik wrote:
/snip/
> 1 RAD = 100 ergs/gram  1 GRAY = 1 J/kg = 100 rads
 [Ludwik assertion one]
> ***********************************************
/snip/

> 3600 mSv is 360 mrem
                                        (??????)

> >   /snip/ I am assuming the yearly
> > dose is 200 mrem. Brian quoted (see below) the average yearly
> > dose of 3600 mSv (360 mrad). This probably accounts for medical
> > treatments. Right? Otherwise 360 is about two times larger than what
> > is usually printed for the so-called "natural background."
>
> /snip/

[Brian]
> > I did not! 3600mSv = 360 rem.    Cockroaches maybe, humans no.
> > I expect Ludwik had 3600 uSv in mind.
[Ludwik]
> NO, NO, NO --> 3600 mSv = 360 mrem  (not 360 rem). [Ludwik assertion two]




Let me spell it out in words....it is possible that Ludwik is not   (1)
registering 'mSv' as 'millisievert'.                                (2)

I assert that....                                                   (3)

It cannot be that                                                   (4)
three thousand six hundred millisievert                             (5)
 equals three hundred sixty millirem [Ludwik assertion two]         (6)
AND                                                                 (7)
one sievert equals 100 rem    (from Ludwik assertion one]           (8)

Ludwik assertion one was                                            (9)
one gray = 100 rad                                                 (10)
and                                                                (11)
one gray = one sievert                                             (12)
and                                                                (13)
100 rad = 100 rem                                                  (14)
so                                                                 (15)
1 sievert = 100 rem                                                (16)

I have numbered the 16 lines above consecutively.
 If Ludwik will tell where his understanding departs from mine
by referring to a line number - it will probably not be necessary
 for him to use all caps.

This is the original text that appeared to wrap Ludwik round the axle:

------------------------------------------------------------------
The Health Physics Society // Submitted by Ron Sumner
//
When a pregnant patient undergoes a complete
dental x-ray examination, the radiation dose to the embryo is
about 1 microgray. Compare this to the average dose from
naturally occurring environmental sources of about 3000
microgray per year.

------------------------------------------------------------------

I write 1 microgray as 1 uGy
I write 1 milligray as 1 mGy
I write 3000 uGy as 3 mGy
Using Ludwik's assumptions,
I write 3000 uGy = 3 mGy = 300 mrem = 0.3 rem


Have at it!     :-)




brian whatcott <inet@intellisys.net>  Altus OK
                Eureka!