AW: [ RadSafe ] Help with old electron tube

[Franz Schönhofer]

Thank you, George, for this information. 

I intended about 10 years ago to conduct a survey on radioactive substances
used in everyday life and in consumer products in Austria. Unfortunately
somebody else wanted my laboratory and according to a long tradition of
intrigue in the Austrian bureaucracy he succeeded and ruined it within less
than a year.....

I am still interested in this topic and I wonder whether these devices
containing radioactive material are still in use. I have a lot of experience
with transfer of tritium from wrist watches to humans, but the use of
tritium has been mostly discontinued or even forbidden. So what about the
devices described?

Best regards,

Franz


Personal remark: I have during my trip to Estonia enjoyed five days in
Helsinki with friends and I can assure you that I had quite a few KOFF (and
Lapin Kulta) beers with my friend Heikki.....

Franz Schoenhofer, PhD
MinRat i.R.
Habicherg. 31/7
A-1160 Wien/Vienna
AUSTRIA



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