Dear Al,

hmmm, to be honest as always, I have strongly hesitated to reply on this interesting topic. The main reason was that I have considered that there must exist another colleague in the forum named "Stephan"..!

But due to I have seen until now that this mate hasn't answered (yet), please let me try to give you a short overview on the specific German treatment of "Thoriated Tungsten Inert Gas Electrodes".

I guess the issue of the radioactivity of Thorium doped TIG-Electrodes is as old as the Thorium itself.

And due to no better information than what has already been given by you and the other wise colleagues here, there is - of course - everything more coming from my side as unnecessary as even possible.

But in particular in regard to your clearly determined question I have tried to find out what the most current safety regulations are in Germany, for treating those electrodes and how the conditions are when they are being used in welding.

Therefore I should describe that it is hard for me to say how other European countries are regulated in respect to this issue, since Safety Regulations are - I assume different to the United States of America(?) - to be used on a national level. This means - as far as I know - the Italians have different regulations in comparison to the Hungarians, the English again different to the Spanish and so on. The European standardization on these issues is just in the beginning and due to we have the not that tiny problem to speak different languages within the European Community you can imagine how difficult it is to find a common level of treatments and regulations.

We sure have a (very) huge administration in Brussels but this is meant by the meaning of the word itself: ADMINISTRATION.

The responsibility in Germany in regard to the maintenance of industrial health and safety standards has the so called "employer's liability insurance association" (in German language we call it "Berufsgenossenschaft" or abbreviated "BG").

Subsequently I will thus abbreviate it "BG" - it sounds better than E.L.I.A.(?) - and I ask your understanding for please knowing what it means.

There are different BG's responsible for different fields of employment. They are united in a kind of Head Organisation (Vereinigte Berufsgenossenschaften = VBG).

Each of those BG's are now treating the conditions of health and safety standards for the different occupational groups. In the field of metal workers we have the United Metal Employer's Liability Insurance Association (VMBG). They are preparing finally the so called "BGI's" (in German) "Berufsgenossenschafts-Informationen". I.e. specific Guidelines treating the safety standards for the particular group of employees.

However, to show how serious the risks for employees (welders) who are using Thoriated Tungsten Electrodes is kept in Germany there has been prepared a valid and normally strictly to follow Guideline for the "Usage of Thoriated Tungsten Inert Gas Welding Electrodes" (BGI 746 = Umgang mit thoriumoxidhaltigen Wolframelektroden beim Wolfram-Inert-Gas-Schweißen, see also the BGI_746_Cover.pdf). This most current guideline (having a size of 28 pages) containing many very interesting information of which a large amount is founded on the German radiation protection ascertainment, due to that Thorium is, just as you have already mentioned above, an Alpha-Emitter.

And I am honest. When I had a closer look on these information (for providing you the most accurate details) I was a bit shocked. Since I have used those thoriated electrodes for many years as well as many others of the forum members did and certainly still do. The reason was that I have been told there were no better ones available at that time what was probably not either a lie.

The BGI 746 describes the safety measures for (Quote):

"...avoiding possible risks in using thoriated Tungsten Electrodes or to reduce these risks down to an absolute low minimum."

Among others there are described solutions for working place configuration or welders safety equipment etc. Basing on the German Radiation Protection Regulations (§ 3) where in general the "OPERATION" with radioactive substances is treated, specific items are listed dealing with particular radioactive elements or substances. Among others here explicitly the "...grinding and AC welding with thoriated Tungsten Electrodes" is stated. Thereby § 94 of the German Radiation Protection Regulations is valid what means that every measure has to be undertaken to minimize the radiation exposition for the employee as far as even possible (Minimierungsgebot = Instruction for Minimization).

So far the "theoretical" background of the German Regulations. What does this now mean for the practical realization?

Now it becomes honestly a bit difficult. When I read what in BGI 746 is explained I felt remembered the on the current efforts and activities in finding an international valid industrial standard for carcinogenic substances in welding (Cr VI, NiO,...).

Since a reliable predication about the worker's radiation exposition rate - in particular the human body's incorporation of Thorium - is almost impossible, only a representative Measurement of the working place' air Thorium concentration is feasible. But to achieve precise predictions in regard to what the worker is being exposed to - what sounds slightly like a contradiction - is again only possible by using a specific and personal working place depending measurement. You know what now comes? Yes! These measurements are too intricate + expensive and thus practical "impracticable".

What then follows within the BGI 746 are some descriptions to best possible solve the problem to avoid expensive and finally impracticable measurements but rather to give some common advice to be on the safe side.

These recommendations and regulations I would like to list subsequently and I would like to leave it to you what kind of conclusions you may come to by these information.

-  In case of using thoriated Tungsten Electrodes for AC-Welding or in case of grinding thoriated Tungsten Electrodes the employer is committed to perform an estimation (§95 Abs.1 German Radiation Protection Regulations) about the employees personal radiation exposition within a time period of 6 months. 

For a better understanding of how this estimation can be realized three different instances are given in the BGI 746. One of those examples I would like to state hereinafter:

"A AC-TIG-welder works 1760 hours par year and uses 50% of this time 2% thoriated and 50% of this time 4% thoriated Tungsten Electrodes. It is assumed that he has to grind the electrodes ~ 1000 times par year. Then the calculative estimation of his radiation exposition is done by:

880h x 4.2 µSv/h + 880h x 8.4 µSv/h + 500 x 0.58 µSv + 500 x 0.29 µSv = 11.523 µSv or ~ 11.5 µSv /year.

One has to know that the factors to be seen above have been fixed by precise measurements in the surrounding areas of welders etc.

These (maximum)values can be stated as following:

-  TIG AC Welding with 2%ThO2 = 4.2 µSv/h
-  TIG AC Welding with 4%ThO2 = 8.4 µSv/h
-  DC Welding with 2% ThO2 = 0.06 µSv/h
-  DC Welding with 4% ThO2 = 0.12 µSv/h
-  Grinding a 2% ThO2 electrode = 0.29 µSv/grinding
-  Grinding 2 4% ThO2 electrode = 0.58 µSv/grinding

Now one has to know the important fact that a maximum exposition rate for only "working" people (in this case welders using radioactive substances) must be lower than 6 mSv/year.

Other occupational groups (occupational exposited persons e.g. nuclear power plant personnel) are treated astonishingly different, by having higher threshold values for their exposition rates (20mSv/year).

What can be seen by this calculation example is that it is actually the case that welders who use thoriated Tungsten Electrodes can be exposited to relative high values of radioactivity. From my personal point of view, the critical issue is that Thorium can be incorporated by inhalation and thus it can - in worst case - damage the human body.

Therefore the BGI 746 concludes the following:

-  DC TIG Welding using thoriated Tungsten Electrodes can be estimated as to go below the threshold value of 6mSv (Inhalation).
-  TIG AC-Welding (e.g. Aluminum) shows exposition- or inhalation rates respectively, laying higher 6mSv/year.
-  Adverse positions of the welders breathing zone (relatively to the arc) deteriorate the exposition rate values. I.e. cause "significantly increased" radioactive exposition.
-  Grinding of thoriated Tungsten Electrodes causes a disposal of radioactive particulate matter - or grit as you have named it. Also here an exceed of 6mSv/year by inhalation can be observed.

To reduce the amount of this response I would like to avoid the measures being necessary or recommended respectively, for reducing the radiation exposition or inhalation of Thorium when working with or using thoriated Tungsten Electrodes. You Al, and the other appreciated colleagues have given many very good hints and professional advice with respect to how one can reduce the risks in using Alpha emitting thoriated Electrodes.

In regard to what you have asked about the treatment of the grinding grit, the BGI 746 makes no explicit predication about how to handle the grit. The only statement concerning this is that one has to take care when disposing the Thoriumoxide containing dust since it can be dispersed then and inhaled by that and can lead to an extraordinary increase of the exposition rates mentioned above. Electrode rests again are not counted to be dangerous to be disposed.

Nonetheless, as far as I know the German "thoroughness", I guess that this "Disposal" is treated within the "Radiation Protection Regulations" which I do not know in detail. Sorry for that.

Please believe me I do not want to upset anybody by having listed partially how the Germans treat the "Thorium problem". As I mean to remember I said once in another post, that in particular the Germans tend to "overemphasize" any technical risk.

But on the other hand when I see that the BGI 746 says explicitly (translated):

"As soon as an employer is informed about the fact of a female employee's pregnancy, the employer is strictly committed to take care that the working conditions for the pregnant woman have to secure that no kind of any Thorium incorporation is possible."

This - so the BGI 746 further - does in fact mean nothing less than the usage of thoriated Tungsten Electrodes has to be prohibited!

And my personal(!) opinion is: By having meanwhile extraordinary good alternatives (Lanthanated, Ceriated, etc. as Henry and the others have explained) in this sector one should consider twice if one should take the risk of any kind of harm only by following some doubtful data (founded in the past) which say that the welding behaviour of thoriated Tungsten Electrodes would beat the other types of electrodes for lengths.

My best regards to you and all the others,
Stephan