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The Mihama nuclear plant in Fukui Prefecture Image: REUTERS file

Fukui court allows 5 aging nuclear plants to continue operations


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Mihama's No. 3 unit, which opened in 1976, became in 2021 the country's first nuclear unit to operate beyond the government-mandated 40-year service period

The service period for reactors was subsequently extended to 60 years 

JGovt just really love with those old reactor until when? At some point it will reach 60 years, 80 years and beyond.


-10 ( +1 / -11 )

Keep them running and drop the price of electricity.

8 ( +10 / -2 )

Of course they will extend their life regardless of safety concerns because they can’t afford to replace them.

2 ( +7 / -5 )

In handing down the ruling, Presiding Judge Yasushi Kato said the court did not find any reasons to believe the reactors could encounter problems and endanger residents

Judge Kato might be learned in the vagaries of Japanese law but he isn’t a civil nuclear engineer which is a highly specialized job…

0 ( +5 / -5 )

what, you don’t like electricity?

-1 ( +1 / -2 )

Sensible decision. If they are safe there is no need to shut them.

0 ( +4 / -4 )

Does not reduce our electricity bill. ¥25.5/kWh.

Updates are required to extend the reactor life from 40 years to 60 years.

7 ( +8 / -1 )

Is the service period for a reactor based on science or is it arbitrary? Exactly which parts degrade and deteriorate over time and can't be replaced?

3 ( +4 / -1 )

The reactor vessels can never be replaced. The part containing the nuclear fuel.

8 ( +8 / -0 )


Exactly, it consists many parts, sometimes, with complex parts it only need one or few to make the whole thing to fail. Extension is not really based on science rather than economy and politics, especially now they try to extend beyond 60 years.

0 ( +4 / -4 )

Mihama is a PWR with a history of, er, incidents, including this from 2004:

Final Reports on Mihama-3 Accident: Critical Facts Remain Unclear Nuke Info Tokyo No. 106 – Citizens' Nuclear Information Center (cnic.jp)


From Wiki: "Of the main classes of reactor with a pressure vessel, the pressurized water reactor is unique in that the pressure vessel suffers significant neutron irradiation (called fluence) during operation, and may become brittle over time as a result. ...

Annealing of pressurized water reactor vessels to extend their working life is a complex and high-value technology being actively developed by both nuclear service providers (AREVA) and operators of pressurized water reactors."

2 ( +2 / -0 )

profits, government subsidies to increase ever more profits, raise prices to ever increase profits on profits in profits and then say they can’t afford to rebuild them with modern tech. Let’s hope they aren’t using an Atari computer and joy stick to control them. What’s another accident waiting to happen in an aging society that everyone’s going to die anyway from in 50 years right.

-4 ( +2 / -6 )

Judge Yasushi Kato said the court did not find any reasons to believe the reactors could encounter problems and endanger residents

the judge himself do not even know the word radioactivity and has no scientific knowledge to even judge the situation.... waiting for another FUKUSHIMA catastrophe.

how the life of people can be handled by a single man??

-5 ( +3 / -8 )

Well, as long as that one-way bridge in the photo is safe in an earthquake, and is not the only escape route.

1 ( +2 / -1 )

It is not only the pressure vessel that is irradiated but pipes, turbine blades, valves, nuts etc.

The building must also be airtight and able to withstand pressure over normal atmospheric.

The longer a reactor operates, the more the aforementioned parts become damaged and prone to failure.

Western Japan contains large cities such as Kobe,Kyoto and Osaka.Depending on wind direction all these cities could be affected by a nuclear accident as well às Nagoya.

Japan has had too many severe nuclear disasters for the country to suffer more.

-1 ( +3 / -4 )

Quake proof designed nuclear plants are nowhere in Japan despite country where strong quake often hit, those seismic resistance are inferior to even general houses. And domestic nuclear power corporations repeat even irrational insistence as if nuclear plants' seismic resistance raised year by year, despite aging.

But Japanese judges are extremely afraid to go against economy circles, often defend corporations profit than safety of citizen.

Because, judge who didn't allow to operate nuclear plants was demoted, judges who allow to operate it had been promoted or had been parachuted to large corporations.

-3 ( +2 / -5 )

The Fukushima reactors 1-3 working at the time of the powerful earthquake on 3/11 survived the quake and went into emergency shutdown or SCRAM. Had there been no tsunami there would have been no nuclear disaster.

The reactors at the second Fukushima plant Daini went into SCRAM and weren't affected by the tsunami.

The reactors at the Onegawa plant went into SCRAM and weren't affected by the tsunami.

1 ( +2 / -1 )

The two yearly 'shakken' check on all automobiles is stricter than then '20 yearly check' on a nuclear power plant.

Brittleization of metals due to radiation, thinning of turbine pipes due to pressure, heat and flow anomalies, all limit the life of a nuclear power plant. In one NPP at Mihama they never even measured the thickness of the pipes, relying on data from a similar reactor plant nearby, which unfortunately then burst, killing 5 and injuring 6. Official report found the failing pipe had been omitted from an initial inspection plan and quality management systems were ineffective.

Safety Japan...

1 ( +3 / -2 )

Clayton K. CharToday  09:44 am JST

Is the service period for a reactor based on science or is it arbitrary? Exactly which parts degrade and deteriorate over time and can't be replaced?

Did you mean to ask which parts don't degrade or deteriorate over time, because they all do.

1 ( +1 / -0 )

All replaceable parts of a reactor are supposed to be replaced every 20-25 years.

The circulation pumps surrounding the core need to be replaced almost every 10 years, and the heat exchangers surrounding the core must be replaced.

Worthwhile read

The Nuclear Aged

Europe’s atomic reactors are getting old. Can they bridge the gap to an emissions-free future?


2 ( +2 / -0 )

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