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OL3 repairs could take several months – expert

10 Nov 2022 10:48

Foto: TVO

Foto: TVO

10 Nov 2022 10:48

(Montel) Fixing the cracked feedwater pumps at Finnish nuclear reactor Olkiluoto 3 (1.6 GW) could take several months if the parts need to be manufactured, nuclear expert Juhani Hyvarinen told Montel on Thursday.

Hyvarinen, who is professor of nuclear technology and head of energy technologies at Finland’s LUT university, previously worked as chief nuclear officer at Finnish nuclear developer Fennovoima and before that for nearly 20 years at nuclear watchdog Stuk.

“Usually, nuclear operators store spare parts that are known to have long manufacturing times if it is not too costly. So, I would not be surprised if they have impellers in storage but they will definitely not have an entire pump,” said Hyvarinen.

“The manufacturing of new impellers would take at least a few months. But changing them does not take long, a few days or maximum a few weeks, including testing.”

The Olkiluoto 3 reactor has been in test production since March but was stopped last month after cracks were found in feedwater pump impellers.

Operator TVO is investigating the issue but has not yet provided estimates of how long the repairs will take or details on part replacements.

It may be possible to source parts from other power plant operators, said Hyvarinen.

The feedwater pumps were common in large nuclear plants and the same type as those installed by Siemens in Germany’s Isar 2 (1.4 GW) reactor, for example.

“The difference – if there is any – is that the ones in OL3 are slightly larger than the pump manufacturer has previously made. But as a type this has been in use for a very long time and as far as I know, there have not been any major issues previously,” Hyvarinen said.

Even if all four pumps were not fixed, the reactor could run at limited capacity for some time, Hyvarinen said, adding that running at full power required three feedwater pumps.

Risk of further issues?
The reactor’s launch is 13 years beyond schedule already and so the turbine had been idle since being installed over a decade ago.

The risk of further complications remained until the project was complete, said Hyvarinen.

“So far, the common denominator with the issues has been that the turbine facility is a prototype, it is not exactly like the ones used in Germany for decades,” he said.

“If it had been the same size as Isar, for example, it is unlikely there would have been these issues at this magnitude.”

However, the issue may be how the reactor was run, he said, pointing to the frequent ramp ups and down during the commissioning phase.

“Ramping up and down”
“The pumps are not really designed for that and the manufacturer might not have considered there would be so much ramping up and down,” Hyvarinen said.

“The initial problems were on the reactor’s side before moving to the turbine, he noted. “There is a wave of issues from inside of the facility towards the outside”, indicating that if any new issues arose, they would likely be linked to electrical equipment such as generators, he added.

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