[ RadSafe ] Help with old electron tube

[Geo>K0FF]

"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


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