Springtime was always the busiest time of year for the women working at the wool processing plant in Chernihiv, northern Ukraine. More than 21,000 tons of wool passed through the factory from farms all across the country during the annual sheep shearing period. The April and May of 1986 were no exception.

The workers pulled 12-hour shifts as they sorted the piles of raw fleece by hand before they were washed and baled. But then the women started getting sick.

Some suffered nosebleeds, others complained of dizziness and nausea. When the authorities were called to investigate, they found radiation levels in the factory of up to 180mSv/hr. Anyone exposed at these levels would exceed the total annual dose considered to be safe in many parts of the world today in less than a minute.

You might also like:

• The bold plan to give Chernobyl a new life

• The bunkers built to survive an apocalypse

• How plants have reclaimed Chernobyl’s poisoned land

Fifty miles away was the Chernobyl nuclear power plant. On 26 April 1986 reactor number four at the power plant suffered a catastrophic explosion that exposed the core and threw clouds of radioactive material over the surrounding area as a fire burned uncontrollably.

But Chernihiv was regarded to be well outside the exclusion zone that was hastily thrown up around the stricken plant and readings elsewhere in the town had shown it to have comparatively low levels of radiation.