13.05.2009 Lauri Myllyvirta

Faults have been observed in the primary coolant pipes of Olkiluoto 3 that are being welded together in France. Finnish watchdog STUK has ordered the manufacturer to stop work until the issue is resolved.

What happens next?
TVO will put together a report on how the faults affect accident risk. The big concern is that, once again, STUK will say that the components are not as good as they were supposed to be but they are still good enough after repairs.

What should happen?
It seems that the problem lies with the pipe material and therefore welding the pipes again may not be enough. As a bare minimum, new tests of welding and heat treatment methods need to be carried out to make sure the welding guidelines are appropriate for the pipe material. Most likely, the pipes should be manufactured again.

This is the second time Areva has failed to manufacture the pipes up to standard. It could well be that the whole plant design is unrealistic if they can't make the enormous pipes as well as the engineers assumed. This would mean that modifications to the entire design of the plant are needed.

The pipes are extraordinarily important because a complete breakdown of these pipes is not an accident scenario that the reactor is designed to mitigate with appropriate safety margins (design basis accident). This points to the need to revise the plant design as well.

Because of mounting quality flaws and persistent problems with safety culture, construction must be stopped. It is impossible to repair a moving train. A thorough international inspection must be carried out instead of just trying to deal with every problem separately after things have already gone wrong.

More info:
A 2007 report by nuclear expert Helmut Hirsch on the problems with the first batch of pipes, potential safety implications and capability of the EPR to handle primary pipe breakdown.