Radioactive Tungsten Electrodes (TIG)


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:


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.

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