At 01:23 on 26th April 1986 an experiment (to test reactor safety) was started at the number 4 reactor of the Chernobyl nuclear power plant in northern Ukraine (then part of the USSR).

Less than a minute after the start of the experiment there was a steam explosion which blew the lid off the reactor and resulted in the largest accidental release of radioactivity into the environment in the history of nuclear power production.

The exposed reactor core burnt for approximately 10 days with continued releases of radioactivity. As well as high contamination in the local area, radioactive plumes were transported over large areas of Europe. At distances from the reactor the highest fallout of radioactivity was due to wet deposition in rainfall.

Contamination in the UK

By 5th May 1986 there were reports that the contaminated airmass had passed over the UK and CEH (then the Institute of Terrestrial Ecology, ITE) began sampling in Cumbria. These samples showed the extent of deposition and we immediately began a nationwide survey of contamination. Utilising the nationwide network of ITE’s sites, 500 grass samples were collected within 10 days of the estimated peak deposition in the UK. Results were published in the Guardian (25th July 1986) and provided the first national mapping of radiocaesium deposition. Days after the initial deposition we had also begun studies to look at the transfer of radioiodine and radiocaesium to sheep.

It soon became evident that sheep in some western upland areas had radiocaesium levels in their tissues above the level allowed for entry into the human foodchain. Consequently the government placed restrictions on the movement and slaughter of sheep in some upland areas (in part using the ITE survey results) - restrictions in Wales and west Cumbria lasted until 2012.

Research focus

During the 1980s and 1990s our research was dominated by the consequences of the Chernobyl accident. In the UK we had a focus on understanding the behaviour of radiocaesium in upland areas, investigating remedial measures and predicting the duration of restrictions. We contributed to international evaluations of the accident and its consequences and, as the former Soviet Union opened up, we began collaborative studies in Belarus, Russia and Ukraine predominantly assessing exposure routes of rural populations but also conducting animal studies in the Chernobyl Exclusion Zone.

Today the focus of our Chernobyl related research has changed to looking at the effects of radiation on wildlife in the Chernobyl Exclusion Zone. The TREE project combines controlled laboratory experiments with fieldwork in the Exclusion Zone, including a camera trapping survey of animals in the contaminated environment.

Above: Slideshow of camera trap photographs from the Chernobyl Exclusion Zone

30 years on - virtual issue of Journal of Environmental Radioactivity

Coinciding with the 21st anniversary of the Chernobyl accident CEH staff published the book Chernobyl - catastrophe and consequences. For the 30th anniversary we have produced a virtual special issue of the Journal of Environmental Radioactivity highlighting 30 key papers published on Chernobyl, and also a review discussing scientific advances and remaining radioecological questions associated with Chernobyl.

Nick Beresford

Additional information

Staff page of Professor Nick Beresford

Blog post: Assessing mammal abundance in the Chernobyl Exclusion Zone

You can follow Nick's TREE project work via @radioecology on Twitter