[ RadSafe ] Help with old electron tube

[MCCORMICK, LUKE I]

In a previous life with the military, we had many H3 tubes. Check
Wright-Patterson web site for their military rad items, & you will
probably find what you need.

Regards,
 
Luke McCormick, Health Physicist
US Customs & Border Protection
6650 Telecom Dr. Suite 100
Indianapolis, IN 46278
Voice: (317) 614-4844
Fax: (317) 298-1139
Pager: (877) 554-9459
Cell: (317) 710-8742

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Geo>K0FF
Sent: Saturday, August 18, 2007 1:41 PM
To: radsafe at radlab.nl
Subject: [ RadSafe ] Help with old electron tube

"Radsafers:

Does anyone have info on an F-2757 electronic tube from ITT made in the 
early-60's?  A picture is attached. The info I have is:

>> The radioactive tubes are high-power TR switches.  When
>> the  430 radar was first installed, it used those tubes so
>> that it could receive both polarizations.  The tubes have
>> radioactive tritium gas in them.

Do these really contain H-3 and any idea how much?  A Google search by
several people has not
turned up any useful info.

Thanks!
Jeff"









Radioactive sources in Vacuum Tubes

Many, even most, vacuum tubes that rely on ionization for their
operation include a radioactive source to help even out that operation.

Tubes that do require ionization but do not include a radioactive source
depend upon external means to initiate ionization (priming), such as
Cosmic Rays, stray background radiation,  and light photons. When the
tube needs to operate in a dark environment, or when it needs to operate
very quickly, beta radiation sources are often included inside to
achieve this goal.

TR (Transmit-Receive) or Spark Gap switches in particular need to
operate very quickly as radars switch back and forth from transmit and
receive on a fast cyclical pattern.

http://www.orau.org/ptp/collection/consumer%20products/electrontubes.htm

Other types of tubes utilizing ionizing radiation include voltage
regulators, neon bulbs, lightning surge protectors, fluorescent lamp
starters, trigatrons, spark-gap modulators, krytons (<5 uCi Ni-63), etc.
NOT ALL tubes that contain radiation are so marked!!

Argon, Neon, Hydrogen, and others are the conductive gasses in cold
cathode plasma discharge designs.
In hot cathode designs, electrons in a high vacuum conduct the current.
Filaments of tungsten ( radio transmitting tubes) or Iridium (ion vacuum
gauges) are coated with radioactive Thorium 232 and heated electrically.


Some easier to find tube numbers are 1B22
1B29 1B41
http://www.tubecollector.org/1b22.htm
2 uCi Ra-226 is normal dose in these.


Early on, RADIUM, Ra-226 was about the only isotope available. After
WW2, short lived reactor and accelerator produced beta emitters like H3,
Co-60, Kr-85, Cs-137, Pm-147, Ni-63
became the norm. Interestingly, Ni-63 is used in the Corotron, the high
voltage regulator commonly used in many Geiger Counters.

Victoreen was once a huge user of Ni-63, refer to the NRC documents
detailing the extensive cleanup at their former plant.

Radio tubes that have metal electrode connectors (pins) passing through
a glass envelope are sometimes slightly radioactive because the kind of
glass used often contains minute amounts of uranium. This type glass has
the same thermodynamic expansion coefficient ratio as the metal used,
keeping the seal gastight during high temperature operation. The
radioactive qualities of the glass have no bearing as to why it is
chosen.


George Dowell, "Geo" 
NLNL/ New London Nucleonics Laboratory


Copyright (c) Viscom Inc. 2007

The treatise may under no circumstances be resold or redistributed in
either printed, electronic, 

or any other forms, without prior written permission from the author.

Comments, criticism and questions will be appreciated and may be
directed to

the author by email to GEOelectronics at netscape.com


 


All PHOTOS (c) by the author unless noted otherwise





"Our progress as a nation can be no swifter than our progress in
education" -- J. F. Kennedy


"You do not really understand something unless you can explain it to
your grandmother." - Albert Einstein (1879-1955) 





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