🚀 go-pugleaf

In article <1992Aug25.201850.28784@gateway.novell.com> terry@thisbe.Eng.Sandy.Novell.COM (Terry Lambert) writes:
>
>	Most smoke detectors use curium, and tend to have a much longer
>"useful life" as a result.  The half life on Promethium is about 2 1/2
>years, which is apparently the manufacturers approach to planned obsolecene
>(can't have the light bulbs lasting forever!).  The gammas being put off
>are fairly infrequent (< 1 per sec).
>
>	The other interesting this is: not only are these bulbs limited to
>a maximum useful life of ~2 years by the half life, the clock ticks on
>regardless of whether you buy the things or not.  That means the life of
>the bulb is limite to ~2 years > (shelf time + installed time), whereas
>regular bulbs are (x hours) > (installed time).  Makes you wonder about
>"sell by" dates and "close out" 'sales'.

Im curious:  How come the half life is equal to the useful life.  If I
remember correctly, halflife means that there is still half the radiation
left after that period, one quarter after twice the period, etc.  What
percentage of the initial radiation is needed for these bulbs to function
correctly?
Oh, and what does the Promethium do anyway?

  --  Joern Wettern
-- 
  --  Joern Wettern
      jwettern@techbook.COM

Using Unix almost makes you want to own a Macintosh.