Radioactive traces are found on shore at Aldeburgh

The Environment Agency’s latest monitoring report on the area around the Sizewell nuclear site reveals that traces of a particularly dangerous isotope known as Strontium-90 were found in the autumn in sediment samples taken at Aldeburgh.

Officials stress the level found was extremely low and is not considered to present any risk to health.

They say that while Strontium-90 emits beta radiation, the level found was tiny compared with the average amount of such radiation routinely found in a human body.

Strontium-90 can be produced by a nuclear reactor but can also be created by atomic fuel reprocessing, such as that carried out at Sellafield in Cumbria.

It could even be a residue from nuclear accidents elsewhere in the world or even nuclear weapons testing carried out more than half a century ago.

Nuclear site operators and the Environment Agency are mystified how the isotope came to be present.

Radioactivity is often measured in units called Becquerels (Bqs). The level of Strontium-90 detected at Aldeburgh was between 1 and 3.8 Bqs per kilogram.

Officials point out that in comparison the human body contains an average of between 4,000 and 5,000 Bqs of the radioactive isotope Potassium-40, which also emits beta radiation.

The Strontium-90 trace was picked up during the monitoring programme for Sizewell A, which has been undergoing decommissioning work, required by the Environment Agency

The Environment Agency said: “We are continuing to work with the operator. It is important to note that these results are unusual and the levels of radioactivity detected are very low.”

A spokesman for Magnox, which is managing the Sizewell A site, said: “While it cannot be certain that it came from Sizewell A, the site holds a permit to discharge Strontium-90 and the Environment Agency has noted that the levels detected are very low. There are no safety or environmental concerns and no risk to members of the public.”