The radioactive substance technetium-99 is leaking from the Sellafield site and contaminates to the ground water table both inside and outside the site. This is being reported by the Health & Safety Executives (HSE) Nuclear Safety Directorate. The source of the leak is suspected to be some old tanks storing great volumes of liquid radioactive waste.
The owner of the Sellafield site, British Nuclear Fuels Ltd., have themselves reported small amounts of Tc-99 in the ground water inside the site, but claimed the low levels posed no threat to safety and that there were no indications that the material had moved off site. Anyway, the HSE now reports Tc-99 has been detected in boreholes outside as well as inside the site.
It is still small volumes of Tc-99 which are leaking, and the event is classified as level 0 on the International Nuclear Event Scale. However, figures for Tc-99 concentrations in the boreholes are currently unavailable.
The large volumes of Tc-99 being discharged into the marine environment from the Sellafield site every year have given rise to international concern. In the Irish Sea there have been detected high concentrations of the substance in both lobster and seaweed. Both the Norwegian and the Irish governments have strongly opposed the discharges. With a half-life of 213,000 years, the Tc-99, will maintain in the environment almost forever.
This radioactive nuclide is very mobile, and discharges from the Sellafield site has been detected as far north as the Barents Sea. The large amounts of Tc-99 originate from the reprocessing of so called Magnox fuel. Purifying technologies are available, but are quite expensive.
The discharges now being traced in the ground water around the Sellafield site originate from a different source. According to BNFL and HSE, the source of this leakage are some tanks inside a 40-year-old storage building (B-241).
Building B241 was initially constructed in the early 1950s and consists of a number of now redundant concrete tanks which were used for settling out (separating liquids from sludges) the treated reprocessing wastes from the plutonium product and finishing streams. Today this building is characterised by hard wear. According to the local environment organisation, CORE, HSE and the Environment Agency (EA) undertook an audit of B241 in 1995.
Their joint report describes the tank complex as then holding 7,400 m3 of waste with a total solids content of 3,000 tonnes. The radioactive inventory of the wastes was estimated at 2,079 Tbq beta/gamma and 81 Tbq of alpha radionuclides.
HSE have now demanded BNFL to find the exact source of the leakages, and to submit a report on how they plan to stop the leakages.
BNFL plans to empty the old tanks, but how the stored liquid waste will be treated is not yet known.