EDF Energy has published its report on the Ground Granulated Blast-furnace Slag (GGBS) silo collapse which took place on the Hinkley Point C construction site on 10th June last year.
The report’s headline conclusion on the sudden silo collapse stating that it was caused by the overloading of a bolted joint due to inadequate design, raises more questions than it answers.
Spokesperson for the Stop Hinkley Campaign, Roy Pumfrey, said:“ The questions raised are questions that nobody should be having to ask at this stage in the construction of a potentially dangerous nuclear facility. EdeF has not told the public whether the design, construction and operation of the silo conformed with all the certification standards. It is purely chance that there were no injuries or fatalities when the silo collapsed. That’s not good enough.”
The report outlines a long list of failures and claims that a significant number of bolts may not have met the specified minimum strength grade requirement. These specified minimum strength requirements are there to ensure that such a catastrophic failure does not occur. Pumfrey added: “The obvious question is ‘if the construction company purchasing the equipment for the HPC build has not gone through the full rigor of checking the certification of the components in their silo, how can we be sure that they are doing so for the materials used for the reactors themselves?” The silo is a piece of work equipment that comes under PUWER (Provision Use Work Equipment Regulations) and as such the supplier should have fully documented the design, which would include sufficient structural design calculations, with copies of the certifications of the components. This major failure of contractors and sub-contractors to adhere to modern regulations, begs questions about the audit trail EDF should have in place for the build of HPC. If there was a strong audit trail and quality control system for the silo the inadequate strength of the bolts should have been picked up. “If such a major failure can be blamed on nuts and bolts not being adequately specified and their quality not being verified, how can we be confident about the nuts and bolts used so far on the constriction of HPC? To also blame hot weather as a contributing factor simply beggars belief.”
The failed component is just one among thousands of different components and materials required for this construction project. EdeF has already had to deal with anomalies in the steel carbon content of the vital pressure vessel lid at HPC sister reactor at Flamanville in Normandy. It seems there is a worrying pattern showing a true lack of quality control at EDF. EdeF has also admitted that the silo did not conform to Construction Design & Management. Regulations that changed after the silo was built. It is unclear, knowing this, why the silo wasn’t demolished as no longer fit for purpose.
Pumfrey continues: “It seems to Hinkley that the Office for Nuclear Regulation (ONR) has been far too accepting of EdeF’s latest page in its book of excuses. One of its Inspectors recently conceded that the silo designer had “made a mistake”, yet ONR expects no further action The public Stop needs to see a full investigation into how the quality control process has failed in the case of the silo and whether any similar failures could be occurring across the whole construction site. EdeF ‘got lucky’ on this occasion as there were no injuries or deaths, perhaps due to the fact that the collapse occurred half an hour before work on site was due to start. We will be seeking evidence from ONR that similar failures cannot happen again, because any such failures could be a lot more serious.”