#### Kathrin Kretz | 6. April 2020

When I attended my first trial day at igus years ago, a colleague told me, “It is never boring here. We get fascinating queries every day. Right now I’ve been tasked to find out whether energy chains can withstand radioactive radiation.” My colleague was right – I stayed, and now I can tell you what I’ve learned.

The question of the suitability for use of our energy chains and cables in radioactive environments arises very frequently.

I am no expert on radiation or chemistry, but in order to understand the queries better, I have acquired at least a general knowledge of the material.

Alpha radiation is the weakest form – paper can deflect it
Beta radiation plastic or aluminium plates can deflect it
Gamma radiation is very intense, penetrating through granite

### How does radiation affect the body?

What is disturbing about this issue is that radiation cannot be seen or felt. When rays strike our bodies, they discharge part of their energy. This affects our cells. It can change cell components or indirectly ionise the water in the cell. This gives rise to so-called free radicals, which can damage tissue. This is when we go to the supermarket to look for juice with “antioxidants” to give us a small sense of security.

### What unit is used to express radiation dose?

This is a truly interesting question. At first, it bothered me that there seemed to be a variety of units. Some doses were given in rad, some in gray, and some in sievert.

The reason is a simple one: rad is an obsolete unit that hasn’t been used in Germany since 1978.
Energy dose has come to be given in gray and effective dose in sievert.
Wikipedia has an article about the various SI units which I consider to be easy to understand, even for the layman.

In order to be able to understand questions from this area and answer them, it is helpful to have a general familiarity with the units:

Sv = sievert (J/kg)
G = gray (J/kg)

rd x 100 = Sv
Gy = Sv
Sv/1000 = mSv

The dose rate is usually given in mSv/h.

https://www.planet-wissen.de/technik/atomkraft/das_reaktorunglueck_von_tschernobyl/strahlung-harmlos-oder-gefaehrlich-100.html

### What is the maximum radiation dose for plastic energy chains?

We have determined the following values for the most common products.

Service life is merely a guide for the material and does not take into account static or dynamic load.

You can use the following formula to calculate how long the e-chain can be used in your application:

You see that, in principle, many igus products are suitable for use under radiation exposure. Service life is greatly dependent on radiation exposure, however. Personally, I would recommend oversizing the energy chain somewhat, since we assume reduced load capacity (70%).

Wälischmiller Engineering has installed our standard E2/000 series in their servo manipulator for removing pipelines that have been radioactively contaminated.

We have discussed the behaviour of our chainflex cables in a radioactive environment with a number of materials specialists from our jacket suppliers. As a rule, we test the product properties of our cables and energy chains in our own laboratory, but we would rather stay away from radioactive radiation.

The specialists’ answers are based on general knowledge of the behaviour of various materials under these conditions. Cable radiation resistance is largely dependent on the molecular structure of the material used, or more precisely, on the length of the molecular chains.

This is why PUR cables are generally better suited than TPE or PVC cables.

The manufacturer’s information indicates that polyurethane is more resistant than most other plastics, but its use in applications with more than 1 mSv is not recommended.

I hope you have enjoyed this article and that it has helped you. The next fascinating question might come from you.

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