A 2007 cooling water leak at the Sizewell A nuclear power plant could have led to a dangerous radioactive leak had a plant contractor not decided to wash some laundry, leading him to discover a pool of water on the floor, the Guardian reports.

Up to 40,000 gallons of radioactive water had already leaked from the pond containing spent nuclear fuel before the leak was discovered, according to the HM Nuclear Installation Inspectorate’s report quoted in the Guardian article. Until that point, no alarms had gone off in the plant.

By the time the next safety patrol was scheduled — 10 hours from the time of discovery of the leak — the spent fuel rods in the pond could have been exposed to the air, risking a dangerous fire and off-site release of radioactivity.

Tags: nuclear energy