On the morning of January, 7th, 2007, one of the contractors working on decommissioning the Sizewell A nuclear power station on the eastern Suffolk coast in England was in the laundry room when he noticed cooling water leaking on to the floor from the pond that holds the reactor’s highly radioactive spent nuclear fuel.

Sizewell A stopped generating electricity in December 2006 and the decommissioning process began. Part of that process is the cooling of spent fuel rods in water ponds and it takes years before they can be moved. Sizewell A and its two 1000 megawatt Magnox reactors went online in 1966

More than 40,000 gallons of radioactive water leaked into the open when a 15ft crack appeared in a pipe leading to a cooling pond in the Sizewell A reactor in January 2007 – some of it leaking into the North Sea, said a report released by Britain’s Nuclear Installation Inspectorate (NII).

The pond water level had dropped by more than 330 millimetres, yet none of the sophisticated alarms in the main control room of the plant were tripped, said the NII report.  

By the time of the next scheduled safety patrol, the pond level would have dipped far enough to expose the nuclear fuel rods, potentially causing them to overheat and catch fire sending a plume of radioactive contamination, killing hundreds of people along the coastline, and forcing the evacuation of thousands more, said a local environmental group.

"It would have been a very serious radioactive release running down the coast of Suffolk as far as the wind would take it," said John Large of the local Shutdown Sizewell Campaign.

The NII’s chief inspector, Mike Weightman, however, said that the outbreak of a fire was unlikely, as the fuel rods were already partly decayed and two feet of water remained in the pond.

But the NII’s report of the incident, obtained under the Freedom of Information Act, revealed a series of worrisome failings.

When the pipe cracked before 11.30am on the morning of Sunday, January 7th 2007, some 182,000 litres of radioactive water spilled from a 4.6 meter long split.

The radioactive water washed into drains and some found its way into the North Sea. The leak should have triggered an alarm, but the one monitoring the pond was not working.

Even if it had worked as expected, however, the Independent newspaper said it is unlikely that anyone would have noticed it, as a different alarm had been going off for days without anyone turning it off.

"The pond could have been drained (it takes about 10 hours) before the required plant tour by an operator had taken place. In this worst-case scenario, if the exposed irradiated fuel caught fire it would result in an airborne off-site release," said the NII report.

It concluded that the "NII believes that there was significant risk that operators and even members of the public could have been harmed if there had not been fortunate and appropriate intervention of a contractor who just happened to be in the right plant area when things went wrong."

The NII commended the plant operator Magnox Electric for responding quickly once the leak had been discovered, saying, “The only good action noted was that when the contractor raised the alarm the operators appeared to react very well and avoided a significant event from becoming a very serious off-site event."

The NII report did note, however, that a prosecution might have been appropriate, but that none was undertaken. A prosecution would have taken "considerable resources" at a time when the NII was financially "stretched,” said the report.

The NII’s own Weightman, however, denied that a prosecution was a possibility.

"The operators secured improvements in safety and complied with the law very early on," he told the Independent.

"If we had had to go to prosecution we would have."

Yet local anti-nuclear groups told Bellona Web Friday that the incident has been downplayed because the NII was reluctant to highlight a leak at a time when the Brtish government was beginning to make public plans to build a new generation of nuclear plants.

The United Kingdom is currently planning to begin building a new generation of nuclear power plants beginning around 2013.