When you sell steel for recycling or direct reuse, you probably know what is likely to be hidden in amongst it; however, those whose job it is to handle and process second hand steel do not.

This makes it important to be able to test for hazardous materials, particularly including radioactive substances that may be contained inside heavy, dense steel receptacles.

Although there are existing methods to detect these, the EU-funded MU-STEEL project has been looking for a better way, and using muon detection this better method has now been found.

In brief, muons are relatively heavy elementary particles – 200 times heavier than electrons – and while they will pass through ordinary steel, the dense plates used to protect radioactive substances will block their path.

Therefore, simply by detecting the number of muons passing through a cargo of second hand steel, it is quick and easy to determine if any potentially radioactive containers appear to be held within it.

It is one way technology is allowing recycled steel to be produced more safely, with quick tests that do not delay the processing and handling of the material.