Magnox Electric, the government’s nuclear operating company, has been ordered to pay £400,000 in fines and costs after being found guilty of leaking radioactive waste into the ground for more than 14 years.
The company denied 11 charges brought by the Environment Agency related to the management of radioactive waste at its Bradwell site, near Southminster in Essex.
On 6 February, a jury at Chelmsford Crown Court found Magnox Electric Ltd, formerly Nuclear Electric Plc, guilty of three charges of disposing of radioactive waste otherwise than in accordance with its authorisation, contrary to sections 13(1) and 32(1)(a) of the Radioactive Substances Act 1983. The company also admitted two counts of failing to maintain the plant, contrary to sections 13(1) and 32(1)(c).
The verdict was the result of a five-week trial. Sentencing the company on 17 February, Judge Peter Fenn said he was surprised the company had omitted to check the suitability of a sump in the plant’s liquid waste system during renovations in 2001.
The sump was the source of a long-running leak of radioactive effluent into the ground. The prosecution told the court the leak occurred because of a combination of poor design and a lack of routine inspection and maintenance.
Speaking after the case, Phil Heaton, a team leader in the Agency’s nuclear regulation division, explained that the leak resulted from basic design flaws in the sump. It was originally just a brick-lined pit intended as an inspection chamber when the first generation Magnox plant was built in the late 1950s. But it was modified in 1976 to hold wastewater before treatment in the site’s effluent plant. The sump had no impermeable lining and clay pipes leading from it had been poorly sealed.
The problem only came to light in 2004 when Magnox staff noticed the liquid level in the pit was rising and falling due to infiltration and leakage into the ground.
The company immediately informed the Agency and the Nuclear Investigations Inspectorate and drained the sump. Its investigation revealed the leak had probably been occurring since the 1976 modifications. However, Magnox Electric and its predecessor Nuclear Electric only bore responsibility from 31 March 1990.
The liquid came from a decontamination bay used for washing down equipment which had been in contact with radioactive material. It was slightly radioactive due to the presence of tritium and caesium 137 isotopes.
The Agency said none of the radioactive material left the site and there was no risk to employees or the environment.
"Boreholes around the site showed no contamination," Mr Heaton told ENDS. "A lot of characterisation was done and it is known that the radioactivity is moving at about one metre a year. In the 100-year decommissioning of the plant, it will not leave the works."
Mr Heaton said the tritium was mobile in the soil but its 12-year half-life would mean it would be of little consequence in 100 years’ time. Soil contaminated by the longer-lived caesium 137 might eventually need to be removed, but the isotope is less mobile and the volume of soil less significant.
The defence sought but failed to show the leak happened while its predecessor, the Central Electricity Generating Board, ran the site. The prosecution meanwhile homed in on failures by the company regarding the sump which had been converted without a proper design specification and had no watertight lining, and for which there was no operating procedure or inspection regime in place.
Magnox was fined £130,000 for the three charges of disposing of radioactive waste outwith its licence conditions, and £120,000 for the two charges of failing to maintain the sump.
The fine is one of the largest ever secured by an Agency prosecution, equalling one handed down to Thames Water in 2000 following a pumping failure which flooded homes in Erith in Kent with sewage (ENDS Report 301, pp 50-51 ).
But it does not come close to the record environmental fine of £1 million secured by the Agency’s predecessor the National Rivers Authority in 1990. Shell UK received the fine following a 156-tonne oil discharge to the Mersey estuary which was put down to negligence.
It is the second time Magnox has been prosecuted for failures at Bradwell. In June 2001 it was fined £100,000 for failing to prevent or report two accidental releases at Bradwell and one at Hinkley A in Somerset (ENDS Report 317, pp 45-46 ).