Page 37 - July-August 2012
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Nuclear Plant Journal, July-August 2012
37
by improved operational performance
and reductions in risk profiles. However,
there are indications that licensees have
not been as proactive in making voluntary
measures to upgrade systems, structures,
and
components
with
improved
technology as many foreign countries
have been doing to enhance safety. It
is important that the licensees not rely
solely on the NRC’s regulations, generic
communications, and inspections, but
demonstrate on their own, initiatives and
high standards of work quality.” This
sentence was formulated carefully and
in a diplomatic IAEA style but in my
remarks as the IRRS team leader, I asked
more clearly: “What could be the NRC’s
leverage to encourage proactive measures
by licensees?”
Concerning Japan, it was noted
already before the Fukushima accident
on the IAEA missions that the Japanese
have built and operated the plants very
much following the U.S. model. For
the seismic hazards there was a solid
regulatory basis in the USA at the time
when the first Japanese plants were built,
and consequently also the Japanese plants
have a robust seismic design with large
safety margins. On the other hand, the
risks addressed by the designers of the
U.S. plants did not emphasize the site
specific risk factors such as tsunamis that
were much more serious in Japan. Also
during the operating stage, it seems that
the Japanese operators have not made
plant modifications that would go beyond
the modest changes that have been made
in the USA at similar plants.
Fukushima has
changed the attitudes:
“never again such a
catastrophe”
The accident of Fukushima was a
heavy blow on all of us who work in the
field of nuclear power. However, it was
encouraging that the political decision
makers and the general public in most
countries did not lose their trust on our
promise on safety. It is also assuring to
see that many operators throughout the
world have clearly expressed their will to
make their plants even safer than they are
today.
Safety reassessments, similar to
European “stress tests”, have been
conducted in all countries with operating
NPP’s and many ideas have been
generated on means to enhance safety.
The innovative thinking of many operators
has shown that we have not yet exhausted
all means to make nuclear power safer,
and even with reasonable costs. In this
process there has been no need to wait
for regulatory requirements because the
operators know best their facilities and
are in the best position to look at potential
areas where improvements could be
made.
TheEuropeanwide“stress tests”were
completed in April, 2012 and the country
specific reports on peer reviews that were
made publicly available on the website
provide a large
variety of examples from the initiatives
taken by the European operators. Some
of those measures are already in the
implementation phase, and it is good
to note that many safety enhancement
projects were actually initiated before
the accident in Fukushima. Many actions
are adapted to specific plants but getting
acquainted to the country specific peer
review reports gives a good overview of
the general trends and also concrete ideas
for consideration at each plant.
I am aware that operators in other
countries have started more or less similar
safety upgrades as those in Europe. I
want to highlight here the ambitious work
conducted by the Japanese industry and
operators in a joint project coordinated
by Japan Nuclear Technology Institute
(JANTI). The final report issuedApril 3rd,
2012 is on website
.
jp/english/ , and it demonstrates well
the new very responsible attitude of the
Japanese industry and operators.
JANTI project started with evaluation
of the course of accident at all four units.
Based on that they made a systematic
fault tree analysis on what went wrong
and where the course of accident had
been possible to turn if proper systems,
resources, or emergency plans had been
available.After that they identified subject
areas for careful engineering examination.
Not surprisingly, these were:
Preparation for earthquake and
•
tsunami (natural hazards)
Preparation of power sources
•
Responsiveness to heat sink loss
•
Countermeasures against hydrogen
•
Preparation for emergency events
•
From each of the above areas they
examined in detail five to ten subjects
and elaborated potential countermeasures
on how the respective failures could have
been avoided. These countermeasures
went beyond regulatory requirements,
and gave a good “shopping list” for
analysis, development and possibly
implementation. The study addressed
even a potential combination of events
that have not happened but would be
conceivable: a major fire connected with
flood, earthquake, or tsunami.
WANO’s Post-
Fukushima
Commission has made
recommendations that
a regulator can strongly
support
As I noted above, after Chernobyl
accident an extensive international
review of all Soviet designed NPP’s
was conducted, and a systematic safety
enhancement programme was based on its
results. We should recognize that a similar
program would be equally important for
all other NPPs as well. I have understood
that the scope of WANO programs
now suggested is being expanded to
review also the features and facilities
for accident response and mitigation, as
well as implementation of design safety
fundamentals. This is an important and
good move that I can warmly support.
Contact: Jukka Laaksonen, Rusatom
