RE: Smoke Alarms & Photon Beams Don't Mix

["Minnema, Douglas" <Douglas.Minnema@ns.doe.gov>]

Thanks to Dave and Mike for the corrections on how ionization-type smoke
detectors work.  When we had the problems, we did not look into the details
of how they worked, but only realized that we could not continue to operate
the reactor if we had a fire alarm every time we pulsed.  All we did know
was that a pulse of gamma radiation set it off.  As I recall, some of our
particle accelerators also needed to use heat detectors for similar reasons.
(I was working at Sandia National Labs.  At the time we had a wide variety
of machines in a fairly small physical area.  It was a close-knit group of
people and lots of fun.)

As Mike said, now I am puzzled too.  Either the radiation was affecting the
circuit itself, or perhaps the device was designed to consider a high
current level as a failure mode.  Note that the main purpose of our fast
burst reactor was to test pulsed neutron and gamma radiation effects on
electronics, so perhaps we were just conducting another test without
realizing it :-)

Also, I do recall that we went through the same thought process that Steve
Frey discusses.  There are distinct advantages and disadvantages of each
type of detector, and they should be selected based on the application and
environment.  If you need the early response and high sensitivity, then by
all means find a way to get the detector out of the beam and keep the
ionization-type system.  Due to the nature of our business, we were more
concerned with protection of property than people, so heat detection was
adequate.  (Not that we weren't concerned about the people, but these were
small buildings, easy access to exits, and only occupied during operational
hours.)


Doug Minnema Ph.D., CHP
Defense Programs
<Douglas.Minnema@ns.doe.gov>

what few thoughts i have are truly my own

> -----Original Message-----
> From:	David_S_Hyder@RL.gov [SMTP:David_S_Hyder@RL.gov]
> Sent:	Monday, February 14, 2000 6:52 PM
> To:	Multiple recipients of list
> Subject:	RE: Smoke Alarms & Photon Beams Don't Mix
> 
> Mike is correct, smoke decreases the current.  Try this link:
> 
> http://www.howstuffworks.com/smoke.htm
> 
> David Hyder
> Health Physicist
> (509) 373-9652
> David_S_Hyder@rl.gov
> Hanford's Facility Evaluation Board
> 
> > -----Original Message-----
> > From:	Michael McNaughton [SMTP:mcnaught@lanl.gov]
> > Sent:	Monday, February 14, 2000 3:25 PM
> > To:	Multiple recipients of list
> > Subject:	RE: Smoke Alarms & Photon Beams Don't Mix
> > 
> > At 05:10 PM 2/14/00 -0600, you wrote:
> > >the ionization of smokey air is different from clear air.
> > >Therefore, anything that ionizes the air in the chamber will set it
> off.
> > 
> > I think the smoke particles attract ions, and so decrease the current -
> > the
> > device alarms when there are fewer ions ... so now I am puzzled.
> > 
> > mike
> > Mike McNaughton
> > email: mcnaught@LANL.gov or mcnaughton@LANL.gov
> > phone: (505)667-6130
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