Introduction

Small amounts of radioactive isotopes are often used in common household items. A good example of that would be ²⁴¹Am in smoke alarms or ²²⁶Ra in watches but today, I want to focus on tubes (valves) and other less common electrical components containing radioactive isotopes!

TG-36 is a spark gap tube most probably produced in the late 1960s or early 1970s and it originally contained around 1 uCi (37 kBq) of ¹³⁷Cs. Even though some ¹³⁷Cs has decayed, it is still active enough so that it can be used as a calibration source for gamma spectroscopy as well as a check source for Geiger counters. When placed right against my RAYSID gamma spectrometer with a CsI(Tl) 5cm³ crystal, the activity increased by 218 CPS.

1B63A tube contains a small amount of ⁶⁰Co which was used to better ionise the gas inside of the tube. Originally these tubes contained 1 uCi of Cobalt-60, however, Cobalt-60 has a rather short half-life of only 5.3 years, which means that there is less than 0.013 uCi left which means that there is no detectable activity. A gamma spectrum of Cobalt-60 should show two characteristic peaks at 1173 keV and 1332 keV.

Victoreen’s DV3A is a voltage regulator tube containing a microscopic amount of ⁶³Ni. These tubes can be found in some old US survey meters from the cold war. I found mine in my Eberline 120 survey meter that I have bought some time ago without even knowing the tube contained any radioactive isotopes! Unfortunately, ⁶³Ni emits only weak beta radiation which is not able to go through the glass tube and even if it would, the amount of ⁶³Ni is too small to be detected.

While this tube does not contain any radioactive isotopes it can generate x-rays if hooked to a high voltage. Sadly, I don’t own a power supply capable of generating high voltage so I won’t be able to demonstrate it. Maybe one day…

AZS switches were often used in different vehicles such as tanks and military planes produced in the Warsaw pact. The tip of the switch has radium 226 paint on it in order to make it glow in the dark but it also causes it to be very radioactive and emit huge amounts of radon since most of these switches are not sealed as a result of their age. It is worth mentioning that newer AZS have a non-radioactive, glow in the dark paint. An easy way to check if the switch contains ²²⁶Ra is simply to check if it glows in the dark. If NOT, then it is most probably radium.

BH-45M is very similar to the above mentioned AZS with the main difference being a slightly smaller activity.

Wait, there is more!

If you know of any interesting tubes, switches and other electrical components containing radioactive isotopes, let me know in the comments section and I’ll do my best to get them and add them to the post!