Hinkley nuclear station: New Cardiff Bay mud dumping plans

EDF Energy wants to "deposit" up to  600 000 cu metres (about 800 000 tonnes) of sediment dredged as part of building work for the Hinkley Point C plant into the sea off Cardiff Bay.

They got away with "only" 120 000t before, in 2018, and now think the compliant Welsh will give them an easy ride.   Natural Resources Wales (NRW) has received a plan for sampling and testing the mud, which will now be subject to a six-week consultation with specialists and the public.  NRW appear to have taken no notice of the basic errors in their previous license - including the lack of EIA confirmed in the High Court case - as summarised in the WANA briefing.

Image captionThe mud disposal site in 2018 was located about a mile off the south Wales coast

EdF's Chris Fayers was interviewed on Radio Wales on 5th February, followed by FoE coordinator Keith Stockdale.

The same old yarn - Cardiff is the closest suitable dump-site; important to keep the dredgings in the Severn Estuary; our sampling was sufficient last time and we're sure it will show no problem this time.  The radioactive dose to anyone is the same as eating bananas.

EdF use calculations as if the mud was dumped in the open sea - a model that is used for Sellafield's discharges in Morecambe Bay. 
As Keith Stockdale pointed out, the Severn Estuary mud does not get swept down the channel.  It swishes back and forth with the twice daily tides, some deposits on mud banks and in saltmarsh, and some gets into the wind as microspray drops.  From the mud banks, it moves up estuaries like the Rhymney and Usk.  When the mudbanks dry out, the mud particles blow onto land and are taken up in crops.  The nuclear contaminants get to people via inhalation and local foodstuffs. 

Thus the model calculations ignore sea-to-land transfer processes established by science.  They assume most or all of the mud disappears to the open sea, yet common observation sees mud banks accumulating and saltmarsh building up.  EdF's Fayers indeed argued for retaining the mud in the Severn Estuary system, as happens to much of it, but NRW has no idea how much reaches the land, nor have they yet required EdF to provide evidence on it.

The Cardiff Dump site was designated only for dredgings from harbour channels.  It was never licensed for ‘capital’ dredgings and not for the heavy clay (64% of the total) which EdF intend to dig out from their massive tunnels for installing 7-metre seawater pipes for cooling water.  Their closest dump site is in fact on land, with their other construction waste.  EdF's real motive in trying to dump in the estuary is they expect the mud to contain radioactive pockets of material that they’d have to test and deal with specially.  How much easier for them (and cheaper) to dump in our sea!

Sampling last time failed to meet basic standards.  Most samples were just recent deposits scooped off the seabed (1-3cm).  The few borehole samples showed mixed results, indicating patchy radioactive deposits down to a metre or two.  The 3 boreholes out near the planned pipes were quite insufficient on international standards for the volume excavated (7-15 sampling positions are specified;  more if contaminants are found to be patchy).   The Senedd Petitions Committee maintained there should be more samples at depth, but the Minister ignored them (supported by Labour on the party whip).

Since that time, further evidence has been found that the nuclear station was discharging elevated levels of radioactivity in sludge from the cooling ponds (decommissioned 2014), arising from mishaps with the spent nuclear fuel elements about 1970 (Prof Keith Barnham).  The greatest fear is of the ‘hot’ particles of used nuclear fuel released in that sludge, because these are not detected by the conventional analysis - yet just one getting into the human body would be very dangerous.

Artificial radioactive components were detected in the 2013 sampling.  Caesium-137 and Americium-241 are the two fingerprints of nuclear reactor products. They are just visible on the CEFAS graph below, because that has been scaled to show "dose", not specific radioactivity.

As plutonium Pu-241 is the source of Am-241, the amounts of Pu-241 are inferred from the intensity of gamma radiation from Am-241.  The CEFAS graph makes the artificials look insignificant, but harm depends not on the gamma-ray dose, but depends strongly on whether the elements are taken up into food and the human body.  U-238 is 30-60% higher in the 3 relevant deep samples, so the real total dose may come close to the 10uSv/a limit.

Plutonium (Pu) is 30x more abundant than given by the government CEFAS analysis.  That assumed Pu-241 is 90% of total Pu (as average in Sellafield discharges), but Hinkley-A magnox reactor had only 3% Pu-241 in the total Pu, being operated to produce mainly ‘bomb’ Pu-239. So their basic numbers are seriously wrong. 

Pu has the property of being quickly adsorbed onto mud particles, which then mainly settle out locally, in the Bridgewater Bay mud.  The mud builds up by a mm or two per year, so deeper samples indicate levels of Pu in earlier years.  Sampling at a sequence of depths allows past discharges over the decades since 1970 to be assessed. Last time they just measured the average in 20cm and 110cm long cores, looking as if they want to hide the pattern of Hinkley's secret past discharges.

NRW failed to require assessment of what happened to the dumped mud in 2018. It's massively insulting to Welsh people to imagine EdF could play the same tricks again, get supine politicians to say it's not radioactive, so they can spread 6 times more mud with historical Hinkley contaminants on our beaches, mudflats and river estuaries, knowing there's no safe level of these nuclear fuel radionuclides and that dangerous 'hot' microparticles may be included,