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Campaigners press for full testing of nuclear plant sediment in effort to halt dumping off Cardiff coast

18 Jul 2020 7 minute read
Construction of new nuclear power station at Hinkley Point. Photo by Nick Chipchase and licensed under CC BY-SA 2.0

Campaigners are calling for plans to dump mud from the construction of the new Hinkley Point C nuclear power station into the sea off Cardiff Bay to be halted.

Campaign group Geiger Bay are pressing for extensive testing of the sediment following what they say is evidence of plutonium contamination, a claim that Westminster’s Environment Agency (EA) denies.

In February environment watchdog Natural Resources Wales confirmed they had received an application from EDF Energy, who want to dump 800,0000 tonnes of sediment dredged as part of building work for the new plant at Hinkley Point, the site of the disused Hinkley Point A facility.

Geiger Bay are a coalition of scientists, experts, individuals and organisations formed to oppose the plans.

Two years ago, EDF were given the green light to dump 300,000 tonnes of mud off the Cardiff coast.

Despite protests and a petition signed by over 7,000 people, and the support of Senedd Member Neil McEvoy, a full Senedd debate failed to convince the Welsh Government to halt the dumping.

During the debate on the initial dumping application in October 2018 the Welsh cabinet Secretary for Energy, Lesley Griffiths, dismissed claims of plutonium contamination in the sediment as “scaremongering”.

“Points have also been raised about historic issues with cooling ponds and the production of weapons-grade plutonium,” she said.

“This has understandably caused concern, but the test results on this marine licence show the dredged material is within safe limits and poses no radiological risk to human health or the environment and is safe to be disposed of at sea.”

However, National Resources Wales has recently admitted in a response to a public consultation that these tests were not sensitive to the presence of weapons-grade plutonium in the mud.



A freedom of information request from Geiger Bay in October 2018 has uncovered evidence from Magnox Ltd, who are now responsible for the Hinkley Point A plant, that accidents occurred when the reactors were producing plutonium for the Ministry of Defence.

As damaged fuel elements were hoisted from the cooling ponds, pieces of irradiated uranium fuel containing plutonium dropped to the bottom of the ponds. The damaged fuel elements, with some irradiated fuel exposed, were loaded into flasks for transport to Sellafield.

At this time uranium, plutonium and pieces of the Magnox cladding could have been distributed on the site. Tests by Dr Chris Busby have shown evidence for uranium and spent fuel cladding on the Hinkley Point site.

Geiger Bay’s FOI request also revealed that Westminster’s National Radiological Protection Board (NRPB) knew that, as a result of the accidents, plutonium leaked from the HPA cooling ponds for 20 years, between 1965 -1984.

Despite this, the Environment Agency only assessed the mud with gamma ray tests. Plutonium nuclei do not emit gamma rays. They decay into short-range alpha nuclei which are highly radiotoxic. All this evidence was presented to the Senedd before the debate two years ago.

Research published in Nature in 1985 by a team led by Emeritus Professor Keith Barnham, Physics Department, Imperial College London shows that Hinkley Point A was run as a plutonium factory from 1965 to 1970. They calculated that Magnox reactors like Hinkley Point A produced 0.36 tonnes of weapons-grade plutonium. Their results were confirmed in 2000 when the Ministry of Defence published an inventory of its weapons-grade plutonium. At the end of the inventory was the entry “From unidentified sites, 0.37 tonnes”.


In 1968 over 50% of the Hinkley Point A core was removed while reactors generated power. Accidents were likely as the cranes and cooling ponds were designed to cope with only 20% a year.

Work was performed at over twice the design rate for the facility so irradiated fuel with weapons-grade plutonium could reach Sellafield before the Nuclear Non-Proliferation Treaty came into force in 1970.

In addition, records of the Ministry of Agriculture Fisheries and Food of liquid discharges from Hinkley Point in 1967 and 1968 are both blank. However, Magnox Ltd subsequently provided gamma emission data from NRPB for these two years that show in 1969 there was a large peak in discharges (up to the permitted discharge level) of the gamma emitting nuclei that accompany plutonium.

The shape of this gamma radiation peak matches the shape of the peak nine months earlier in the amount of irradiated fuel removed and transported to the cooling ponds when refuelling at over twice the design rate. This suggests that the pieces of irradiated fuel broke off as the cranes lifted already damaged fuel elements from the ponds after only nine months cooling. The average cooling-off period for all Magnox reactors was 14 months.

Using data from the NRPB memo that tabulated the radiation from plutonium nuclei in the liquid waste from HPA for the 20 years from 1965 to 1984, Barnham estimates that, if no remedial action was taken, by 2014 when the ponds were drained, around 300 grams of plutonium could have leaked in liquid waste from the ponds to the sediment.


To escape the filters in the waste pipe, the plutonium would have had to be in the form of particles of a few microns in size or smaller. Plutonium containing particles around a micron diameter can be inhaled into the lungs and cause cancer. The biggest health risk in the mud already dumped off the Welsh coastline comes from the observation that plutonium-containing particles of this size have been blown back in sea spray onto the shores around the Sellafield reprocessing plant. If the plutonium leak continued at the same rate after 1984 there could be around 30-million-million such particles in the Hinkley Point sediment.

Another major health risk arises from uranium particles small enough to have escaped the filters. The Nature calculations show that, for every atom of plutonium exposed in the broken irradiated fuel, 500 uranium atoms would also have been exposed. As direct tests for uranium were never made on the liquid waste discharges, it is unclear how many such particles are in the mud.

Barnham also notes that 1969, when uranium and plutonium could have been released on the site as the damaged fuel elements were loaded into flasks, coincides with the start of a five-year leukaemia cluster reported in the British Medical Journal.

Nuclear industry sources claim routine HPA discharges were insufficient to produce the leukaemia cluster, but Barnham points out that these accidents were anything but routine.

Burnham-on-Sea, five miles away from Hinkley Point A, was named as the most significant ‘cancer cluster’ so far discovered near a British nuclear plant 18 years ago following a report by Dr Chris Busby, a government radiation adviser.

According to his study, which investigated cancer cases in Burnham since 1998, residents were 5.95 times more likely to get kidney cancer, cases of cervical cancer were 5.6 times higher than the national average and leukaemia rates were over four times above the norm. Women from Burnham had more than double the risk of breast cancer.


When the original sediment was tested prior to its dumping off the Cardiff coast it was only tested for gamma radiation Plutonium emits alpha radiation rather than gamma radiation. National Resources Wales has recently accepted Barnham’s evidence that gamma tests are not a reliable indication of the amount of plutonium in the sediment and has asked for focussed alpha testing to take place before the second round of dumping.

Campaigners insist samples must be taken at all depths in the sediment from across the Hinkley site, in the estuary, and in all the locations where Americium 241 levels, a marker for plutonium, have increased because of the dredging.

Barnham concludes: “I am pleased that Natural Resources Wales has accepted our evidence that the Welsh Government were misled by Westminster’s assurances before the first dump that alpha testing wasn’t necessary. We would like to help the Marine Licensing Team agree to the scope of the plutonium tests to be made before any more mud is dredged.”

Geiger Bay, a coalition of scientists, experts, individuals and organisations has now launched petitions to the Senedd and on in an effort to mobilise public support to stop the sediment from Hinkley Point C  being dumped off the Welsh coast.

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