BNFL’s plans to stop pumping radioactive waste into the Irish Sea are set to be turned down by the Environment Agency.
The company is coming under increased international pressure to end emissions from its Sellafield reprocessing plant, but the technology it has proposed as an alternative cannot be relied on in the long term, according to the nuclear industry’s own regulatory body Nirex, which advises the Environment Agency.
The pressure on BNFL to act follows concern from Norway that emissions of the radioactive nuclide technetium-99 are reaching the North Sea and damaging their fishing industry.
Traces of the substance have been found in shellfish and seaweed off the coast of Norway, and the Norwegian government last week threatened legal action to stop BNFL discharging waste into the sea from Sellafield. Some marine life, including lobsters, swallow and reconcentrate the nuclides, leading to health fears for fishermen and consumers.
BNFL believes the best option is to do nothing, and carry on dispersing the waste into the sea as it does now, said Bob Morley, manager of environmental discharges strategy for Sellafield. ‘We would argue that it is far better to disperse it in the marine environment than to concentrate it in particulate form,’ he said.
But the government is not likely to allow this, as it has already signed an international treaty agreeing to stop discharges of the radioactive nuclide. Margaret Beckett, the environment, food and rural affairs secretary, and health secretary Alan Milburn are to make a decision on these discharges soon.
So, despite its reluctance, BNFL will have to stop these emissions. Its proposal is to pour the chemical tetraphenyl phosphonium bromide (TPP) into waste streams containing Tc-99, during the treatment process at its Enhanced Actinide Removal Plant (EARP) at Sellafield.
Following research in its own laboratories, the company believes the TPP will combine with the technetium, creating a solid that could be collected and stored in stainless steel drums. In the longer term BNFL hopes to store this substance in deep-waste repositories underground.
‘The process almost certainly does work, and we have tested it on simulates, but the ultimate test is a plant trial, and we won’t know how effective it is until we do that,’ said Morley.
But Nirex, the industry body established to set standards and advise the Environment Agency, is concerned the substance may leach out into the environment in thousands of years’ time.
Nirex does not have the power to stop the trials, but it has refused to give BNFL a so-called letter of comfort to go ahead – advice the Environment Agency uses to make its decision.
This stalemate has arisen because BNFL did not foresee a need for a technetium-removal system when it built the EARP plant, which cost £168m and opened in 1994, said John Large, independent consulting engineer. This was accepted by the industry regulators at the time.
‘BNFL is really in a corner – it was not completely on top of the technology. The firm did not predict this situation. Now it has happened and the company is embarrassed, so it is going on the back foot,’ said Large.
‘BNFL’s assumption that technetium will be diluted and disperse in the sea would be fine if it were not for marine animals. The chemistry and dispersal of these radioactive nuclides is very complex, while the ability of lobsters and other shellfish to reconcentrate the substances almost defeats the object of reprocessing plants,’ he said.
‘One of the problems within the industry is that the regulators have to go to BNFL to find out what the available technology is. But it is not for the company to make moral judgments on the best solution.’
Removal plant may be solution
BNFL may be forced to build a special technetium removal plant if the government and the industry’s regulators decide they are not satisfied with the fuel giant’s proposal.
There are a number of unresolved issues with combining TPP with technetium, said Bruce McKirdy, deputy head of safety at Nirex. ‘At the moment we do not have the information to give us confidence that this option will be safe in the long term. We have suggested alternatives to BNFL which we think would be better.’
Nirex has proposed that the company build a new facility at its waste treatment plant to take technetium out of the liquid effluent using electro-deposition. This process involves putting an electrode into the liquid to attract the technetium.
BNFL is reluctant to build a new facility, as it could cost between £100 and £200m, and may not be available until 2007.
But although building this additional treatment facility may take longer, as yet no one knows how long the TTP process itself would take to implement, said McKirdy. ‘There is an immediate need to stop pouring technetium into the sea, but we also need to make sure that whatever we do now is not storing up problems for the future. We do not have to go for a knee-jerk reaction,’ he said.
Once the technetium has been separated it will still need to be stored. The Environment Agency has advised BNFL to upgrade the technetium to a high-level waste, and store it in glass cylinders. At present it is rated as an intermediate-level waste, meaning it would be stored within cement in steel drums.
So where does technetium-99 come from?
During reprocessing, spent fuel rods are dipped into nitric acid and boiled. This liquid is then poured into the chemical processing plant, and high-level radioactive waste such as uranium and plutonium is separated out as solid waste. The remaining chemicals are left as liquid effluent, which is diluted until the radioactive nuclides within it reach permitted levels. This liquid effluent is then poured into the Irish Sea.