Nuclear Monitor #927
Jan van Evert
The failure that occurred in April this year at the Oskarshamn nuclear power plant, Sweden’s largest, is classified by the Swedish Radiation Safety Authority as the most serious in five years.
A pipe outside the reactor vessel has broken and because of the position, the fault is classified as a category one, the most serious fault. The last time this happened was five years ago. This means that the reactor cannot be put into operation until the Swedish Radiation Safety authority approves it.
Uniper, the main owner, expects the plant to restart on August 15th at the earliest. The reason for the prolonged work is that the pipe is so difficult to access that a special working group had to be appointed to decide how the repair should be carried out.
Basically, it is a leak that has been detected in the primary system. It has been identified in a place where there are very high requirements for integrity of these structures. “We definitely don’t want leaks there,” says Francesco Cadinu, inspector at the Swedish Radiation Safety Authority.
The reactor was taken out of service in March for annual maintenance. During the audit, a crack was discovered in a pipe outside the reactor vessel. “During the audit, it was discovered that a pipe that is stupidly located was broken”, says Désiree Liljevall, press officer at Uniper.
Because the fault is classified as a category one, the reactor can only be restarted after the authority has approved it. Initially, the reactor owners categorised the fault as less serious, but the Swedish Radiation Safety Authority made a different assessment.
“We have decided that this incident needs to be classified as a category one instead. There is a team working on this case,” says Cadinu.
He emphasises that the fault does not pose any risk at the moment. “At the moment there is no risk linked to the damage, because the reactor vessel is empty and the plant is shut down.
The other day, the owners of the nuclear power plant announced that the earliest it can be operational is August 15th. “This is what it’s like to operate a technically advanced plant. Sometimes components break down and need to be repaired. We need the summer to repair the pipe and get approval”, says Liljevall.
Last year, one of Sweden’s nuclear power plants was also out of service for an extended period. Forsmark 3 was repaired for five months. This year, that reactor has also been out of operation for a few weeks due to a fault in the valves, but it is currently being restarted.
