Britain's Office of Nuclear Regulation said this week that the release of water at the Sellafield site on March 1 of this year during extremely cold weather included as much as 680 cubic meters (more than 24,000 cubic feet) of water. But the regulator said the estimate of the amount water that became contaminated before it was cleaned up was conservative, even while the effect on the environment was "negligible."
The leakage was rated as an INES Rating 1 event, which is the lowest level of concern above no safety concerns at all in the International Nuclear and Radiological Events Scale. A No. 1 rating is defined as an anomaly, falling below No. 2, which is defined as an incident.
Still, the ONR said the pipe failure involved “an overhead external raw water supply (i.e. an uncontaminated raw water process supply) pipe failed and water subsequently flowed into an active pipe trench and the basement of a contaminated redundant building. This resulted in contaminated water from the flooded basement flowing into a concrete compound on the side of the building and along a redundant sealine trench.”
The contaminated water “discharged to ground within the site at these two locations.” Meanwhile, the remainder of the water was pumped by installed systems and by fire brigade to waste water systems that discharged the water into the sea “by the approved route,” the ONR said.
Although the amount of water was estimated conservatively, the radioactivity of the water released to the sea was said to be “negligible.” Six samples of water tested indicated that the main alpha radiation emitters “exceeded the limits set out in column 5 of schedule 7 to the IRR17 by a factor of four.” However, if all of the contaminated water had been released to the sea it would have been an amount approximately 1/50,000 of the annual total authorized discharges to the sea allowed the Sellafield site, the agency said.
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