Last-ditch efforts are being made to stop a new form of nuclear waste being pumped into the Blackwater estuary at Bradwell.

From Thursday waste from Fuel Element Debris (FED) treatment is due to be released into the river on each high tide for 18 months.

The process involves the ends of fuel rods used in nuclear power station reactors being dissolved in acid to bring them within safe levels of radioactivity and then releasing the waste into waterways.

The Bradwell Against New Nuclear Group and supporters have launched 11th hour legal challenges and made last pleas to the authorities, including site operators Magnox and regulators the Environment Agency (EA) to halt the process.

It is concerned about the impact the waste could have on the environment, including Mersea oysterbeds, and also those who use Bradwell Marina who BANNG say could be sailing or swimming in nuclear debris.

The area was recently made a Marine Conservation Zone, which BANNG calls “a toothless policy”.

Graham Farley, who has been supporting BANNG with legal action, said: “There was much criticism over the actions of the EA in respect of flooding. MPs criticised the EA for not listening, it seems as though they haven’t learnt anything from that episode if this is how they react to something so emotive as nuclear waste and its effect on people and the environment.

“This is purely a cost-saving exercise as the normal route is to store the waste in sealed yellow bins which eventually end up in long term central storage.

“The FED plant will be removed after 18 months and moved elsewhere. All to save money.”

Peter Clements, mayor of West Mersea, added: “We always say the River Blackwater is unsuitable for the discharge of waste because it takes 10 days to discharge so whatever they put in it sticks.

“The oyster industry has recovered remarkably since they stopped the power station so as far as we are concerned there’s no doubt about the effects it would have on the environment, and this could knock back that recovery a lot.

“There is a lot of smoke and mirrors and one does not know how far you can trust what they say.”

An EA spokesman said: “Nuclear power stations discharge within strict permitted limits and monitored. Whilst the FED process is new to the Bradwell site, the associated discharge and its impact on the estuary is well understood.

“We take account of impacts in the local environment when setting limits and carry out our own environmental monitoring in the local area to determine levels of radioactivity in the estuary. These continue to demonstrate that levels in the environment around Bradwell remain very low.”

A Magnox spokesman said: “Magnox has been engaged with local stakeholders on its proposals for treating FED as part of the work to decommission the site for a number of years.

“The process, which is based on the safe and successful dissolution experience elsewhere, will reduce the volume of FED by more than 90%. The dissolved metal will be treated and a solid waste will be retained on the site.

“The remaining effluent will be discharged within authorised limits agreed by the EA. Discharges to the estuary within agreed safe limits have been taking place regularly for more than 50 years and are continuing as the site is decommissioned.

“Magnox is sensitive to the local environments in which it operates and is committed to decommissioning Bradwell with the highest regard to safety and the environment. Our work programme is fully compliant with regulatory requirements and we will ensure it remains so as clean-up of the site continues.”