Mihama is a nuclear power facility owned by Kansai Electric Power Co.
Mihama was the first commercial reactor in Japan.
Unit 1 started operating in 1970 and Unit 3 is in serviced since 1976.
It is located at 320 kilometers West of Tokyo.
And there are 3Westinghouse/Mitshubishi PWR reactors.
Let's see what happened there.
In 1990, the PWR operators in Japan developed guidelines
in order to deal with secondary piping wall thickness.
A mechanism called Flow Accelerated Corrosion of FAC, was included.
These guidelines were applied in Mihama by the PWR vendor, Mitshubishi.
Six years later, in 1996, the NPP Builder transferred
this corrosion control to a new contractor.
Next year, in 1997, this new contractor developed a new CAD model
for the secondary piping.
And because of that, years later, they discovered sections
that should have been included in the Guidelines.
They added them but they did not communicate this
preferring to wait for the next outage.
Later the same year, in June, a report was made,
but the omission of those pipelines is not told to anybody.
And finally, in November, it was established
a new inspection program, once again there are poor communication
and there is not update that new sections have been included
in these Guidelines.
There is little concern for Safety Culture
both by the contractor and the operator
which has not work to develop proper communication ways.
Here we have three different failures.
First, they did not communicate the discovery of pipelines,
because the Refueling outage was close.
The omission of inspection in some pipelines.
And do not communicate the addition.
Then, during August 9th at 3:22 pm,
some fire alarms in turbine building started.
The lower area was full of steam.
A load power reduction started but there was a steam generator
main steam mismatch, which caused a reactor trip.
There were 104 contractor employees and 1 Kansai SRO involved.
There were several injured. And a rescue plan was activated.
Later that day, a main steam break in the condensate piping was found.
The aftermath can be summarized as 11 people were injured,
four were burned in hospital and five dead.
All because there was a poor safety culture.
All the communications failed from Mitshubishi
when they did not include the piping to the new contractor
which did not communicate their discoveries,
hoping not to be discovered
before the next opportunity to implement all of them.