Re: Bq soon

[Graham Roger Stevenson <Graham.Stevenson@cern.ch>]

Greetings!



A few comments on SI units may help to calm personal fears - it is not at 

all as bad as you think it might be!



I work for an international accelerator lab of about 3000 staff, about 2000 

visitors and another thousand or so contractors on site.  We changed to SI 

units for radiation protection over ten years ago, essentially overnight.  It 

took almost no time at all (a few weeks) for people to become familiar with 

the new system and now the only people to have trouble are our American 

friends and visitors.  Conversions between units still go on, and my usual 

pain is the conversion between electronVolts and Joules.  But that is still 

better than thinking in foot-pounds.  However it is most useful to have power 

deposition in mWatts/gram (for energy deposition in superconducting coils) 

being identical to Grays/second (which can damage the coil). And to know the 

weight of the earth shield above my accelerator enclosure in tonnes by 

knowing the specific gravity and the thickness in metres is a distinct 

advantage since the density of water is one tonne per cubic metre instead 

of a stupid 62.5 pounds per cubic foot.



On a personal basis, having lived in France for 30 years now, I find that old 

units do not die or even fade away with time.  You might like to share my 

amusement. Foodstuffs in a market are still bought in "livres" (pounds), but 

at 500 grams (half a kilogram) instead of the "real" 450 grams or so.  Butter 

in Italy is still bought by the "etto" (100 grams or a quarter of a pound 

approximately.  Napoleon didn't win everywhere. Pipe bore diameters are still 

mesured in units of a quarter of an inch. The French are still thinking in 

"anciens francs" (old francs) even though that currency was replaced by the 

new franc some 40 years ago, which was itself replaced by the euro recently.



I do not complain about SI units but I do complain about the American pint,

which weighs 16 ounces, versus the Imperial pint which weighs 20 ounces.

Thus the US quart and gallon are some 20% smaller than real quarts and gallons.



Becquerels for ever! but I still have some regrets about the passing of the 

millirem.  The innate danger levels are still there though in the new system. 

Sieverts and Grays are lethal, millisieverts are nasty, microsieverts don't 

count unless there are lots of them and who cares about nanosieverts! 



Graham

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| Graham R. Stevenson,         | Email: Graham.Stevenson@cern.ch |

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