camelot-forum.co.uk

EDF to review whether they can delay closing Harlepool and Heysham nuclear plants again. They're already 8 years past their original planned shut downs. But I guess we need all the electricity we can get?!

https://www.theguardian.com/environment ... ol-heysham

All high pressure boilers in the U.K. require to be insurance inspected annually. Every five years they need a Non destructive test of all the welds associated with the pressure vessel to legally be allowed to operate. A hydraulic pressure test well in excess of the working pressure is also under taken.
How do E.D.F. get away with these procedures. One would hope the procedures in France / E.U. reach the same standards. ????
They are running in France well past there inspection times.

I believe they have just switched to "on condition" inspections nor a lot of stuff, and life-extended based on the inspection history. Not unusual in just about everything involving engineering. The design process will have used worst case factors for things like stress corrosion, microfractures occurring in welds, radiation induced degradation, etc. They will then have put a life on the system, with a hefty safety factor. If the inspection history over the years shows that the actual operating conditions were less severe than the worst case used during design, then it's usually possible to give a life extension.

This happens all the time in civil engineering, structures get their predicted end-of-life changed as a consequence of inspections showing rates of degradation that were higher or lower than the design team envisaged. The other factor that kicks in is whether a design life extension makes sense in terms of the additional maintenance cost. Very often things get shut down and demolished not because they are unsafe, but because they cost to much to maintain.

These two stations were equipped with pod boilers and the original basis of design allows for the boilers to be removed for repair / replacement. Unfortunately a few decades back the containment studs that held the containment covers in place over these boiler access points were found to be badly corroded and the only option available was to weld the containment covers up to seal them agains the reactor coolant pressure levels. These pod boilers are now inspected routinely as is the rest of the fleet using a raft of remote inspection equipment including an incredibly long camera that has been modified from the other more standard boilers in the fleet to deal with the tight radii in the pods.

The boilers are less of a concern than the corrosion to the heat shield that sits above the core on these stations and of course the fleet wide issue of moderator integrity due to mass graphite wastage and structural integrity of the fuel and control channels therein

Moxi