May 2022

Radioactive Tungsten Electrodes (TIG)

Introduction

Today I want to show you an item that you can find in a hardware store and it is radioactive. Let’s take a closer look at the thoriated Tungsten electrodes!

Main information

There are three types of thoriated Tungsten electrodes with the only difference being the amount of Thorium in them. Yellow ones contain around 1% of Thorium, red contain 2% and orange contain 4%. Even though orange ones contain the highest amount of Thorium, they are actually not much more radioactive than the red ones which are the most common. Tungsten electrodes come in different sizes with the bigger ones being slightly more active. Personally, I decided to go with 3.2mm x 175mm but smaller should also work fine.

Red Tungsten Electrodes (WT20)

Isotope: 232Th

Activity: < CPM (LND 7311)

Amount: ~2%

Since the label on the box clearly states that these electrodes contain Thorium, I didn’t expected the gamma spectroscopy to show anything intresting but to my suprise, it did!

Slide to the right to see Thorium gas mantle spectrum
Slide to the Left to see Thoriated Tungsten electrodes spectrum

The main two differences between the spectrum of Tungsten electrodes and the spectrum of Thorium gas mantle are the peak at 511 keV and the peak 583 keV. Let’s start with the peak at 511 keV. It is referred to as annihilation peak and it is caused by the annihilation of a positron by its interaction with an electron. This event can occur more often in Tungsten electrodes because of their density. The peak at 583 keV is caused by Thallium 208. When Thorium decays, it emits Radon 220 which is a gas and it escapes into the air but in the case of the Tungsten electrodes, it is trapped by dense Tungsten which results in the accumulation of Radon decay products including Thallium 208.

Thorium decay chain (source: metadata.berkeley.edu)

Safety

These electrodes are often used as a check source because of how easy to find they are and their small activity which makes them relatively safe. That being said, when used for their original purpose, the dust generated by sharpening them could cause health problems in the long run if inhaled.

Fake Tungsten Electrodes

When buying these electrodes, make sure to buy branded ones because unfortunately, unbranded ones are often fake and they do not contain Thorium. I made this mistake twice and both times I received fake electrodes that weren’t radioactive.

By allRadioactive, ago

Radioactive BH-45M Switch

Today we will take a closer look at a radioactive, soviet switch, the BH-45M!

The production of BH-45M switches started in 1945 and continues till this day, this being said, not all of those switches are radioactive. Units produced until 1965 used radium paint but in later models, radium paint was replaced by a nonradioactive one. The very early models which were produced until early 1950s, used RaBr2 while the ones produced later used RaSO4. BH-45M switches are mainly used in military vehicles such as tanks but can also be found in some civilian ones. These switches were produced in countries of Warsaw Pact and can be found today cheaply at antique markets.

As a result of constant exposure to nuclear radiation, the paint decays and with time it loses its radioluminaces properties. Today the glow from the switch is undetectable for human eye but a photo made with a long exposure shows that there is still little bit of glow left.

Long exposure of BH-45M switch

Radium is a particularly nasty element not only because of its very high activity and radio toxicity but also because it decays into a radioactive gas called radon which in large doses can be dangerous. Luckily, the switch I have is pretty well sealed and doesn’t leak too badly, so the radon emission is relatively low.

Activity and Gamma Spectroscopy

Radium painted items range in activity anywhere from few hundred CPM to hundreds of thousands depending on the amount of radium paint used. When it comes to BH-45M switches, they are definitely are on the hotter side. The one I have measures at around 220k CPM at 1cm distance on a pancake probe and 10uSv/h gamma only at 1cm distance on my RAYSID gamma spectrometer.

Just as expected, a gamma spectroscopy of the BH-45M switch shows a very characteristic gamma spectrum for Ra226 and its decay products.

By allRadioactive, ago