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27th International Conference on Structural Mechanics in Reactor Technology (SMiRT)
山中委員長挨拶
2024 年 3 月 4 日

On behalf of the Chairman of the Nuclear Regulation Authority, NRA, I would like to sharemy sincere welcome with all the participants here in SMiRT27 at Yokohama and hope that
devoted technical discussions contribute to enhance nuclear safety. It is great honor to me
to have this opportunity to make a speech today.
I had been engaged in research on the safety of nuclear fuel at Osaka University for nearly
40 years, and then I was appointed to a Commissioner of the NRA in 2017. Five years later,when I became a Chairman of the NRA, in my first message as a head of the organization, Iemphasized three areas that I would like to put foci:① Communication with various stakeholders in more understandable manner,② Regulation considering facilities’ situation in real,③ Human resource development in nuclear safety.
Till today, I have been working with these in mind as a Chairman.
The NRA was established in 2012 based on the reflection and lessons learned from theaccident at the TEPCO's Fukushima Dai-ichi Nuclear Power Station.
In the past, there was a widespread safety myth, which is wrong belief, that accidents would
not occur if only safety standards were met, and continuous improvement for safety wererarely made. This situation must be one of the results from the structure of regulators that theregulatory bodies were not independent from nuclear promotion agencies, and that theresponsibility of safety regulation was dispersed under double-check hierarchy.
Furthermore, because of the lack of technical expertise in the regulator, technicaldetermination had to rely upon the licensees’ interests; therefore, the regulator could notaccomplish regulatory requirement to avoid accidents in the timely manner.
Those are why the NRA was established as an independent regulatory committee governedby expert commissioners and with authority to regulate whole nuclear safety arena.
The magnitude-9 earthquake and tsunami on March 11, 2011, resulted in the simultaneous
loss of functions on multiple equipment and systems in TEPCO’s Fukushima Dai-ichi, andthen failed to prevent the severe accidents at Unit 1 through 4.

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The lessons learned from this accident are reflected in the strengthen safety regulatory
requirements of nuclear facilities we developed in the summer of 2013.
We have greatly reinforced the countermeasures against natural hazards such as
earthquake and tsunami, and have enhanced the requirements for preventing severe
accident, for example, by multiplexing and diversifying SSCs (structures, systems andcomponents).
In addition, we have newly required to deal with and mitigate the progress and outcomes ofsevere accident and terrorism.
With these new regulatory requirements, we have reviewed and approved the renewal oflicenses for nearly 20 units of nuclear power plant so far.
In terms of continuous improvement of safety, instead of we are constantly collecting new
knowledge and discussing the improvement of regulatory requirements, not leaving them as
they are.
In our legal requirement, a robust back-fit scheme is built-in, where new knowledge obtained
from domestic and overseas operational experience or safety research is screened for thediscussion at the NRA Commission Meeting in order to decide the necessity of reflection asa regulatory requirement. Once decided to be reflected, then the legal documents would beamended and applied to existing facilities.
To date, more than 10 back-fits have been decided, including countermeasures against
natural hazards such as volcano, earthquake and tsunami, as well as internal flooding.
With regard to the Noto Peninsula Earthquake occurred on January 1, this year, we willcollect knowledge by paying close attention to the investigations and researches conductedby relevant parties, and if new knowledge is obtained, we will appropriately determine
whether or not it is necessary to incorporate it into regulation and how to incorporate it.
Besides such back-fit efforts by the NRA, I would like to make a strong emphasis that it isquite important to encourage licensees’ voluntary continuous safety improvements as they
have the primary responsibility for nuclear safety.
The Fukushima Daiichi NPS accident also revealed that off-site countermeasures, such asevacuation and its preparation, needed to be improved.
Many lives were lost due to inappropriate evacuations; however, there were no loss of life
from radiological damage on the contrary.
The NRA formulated the Nuclear Emergency Preparedness and Response Guide,
recollecting such a situation during the severe accident.

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The EPR Guide stipulates how to set zones for preparation of protective measures andoperation against nuclear emergencies according to the types and characteristics of nuclear
facilities.
Referring the EPR Guide, the local governments build a plan for residents’ protective
measures including smooth evacuation, taking into account their geography, climate,demography, transport network and so on.
After legislative discussions in the Japanese National Diet, the new Nuclear Regulatory
Inspection System has come into effect since April 2020.
Currently, the NRA inspectors can freely observe facilities and components, and accesslicensees’ information anytime and anywhere.
Our inspectors also oversight from performance-based and risk-informed perspectives; thatallows us to check the level of safety in effective and efficient manner.
Resident inspectors walk through the facility on a daily basis, and when needed on specificissues, the expert inspectors are dispatched from the NRA headquarters.
The aftermath of TEPCO’s Fukushima Daiichi NPS accident is still on going.
As one of our top priorities, the NRA has kept eyes on TEPCO's decommissioning work at
the Fukushima Daiichi NPS, in order for safe and steady progress.
During 10 years after the accident, the main activities were countermeasures against
challenges with high radiological risk brought by the accident.
The next 10 years should be the period to advance a new phase of decommissioning, namelywaste management, including analysis, classification, appropriate treatment and storage ofvarious types of waste.
Moreover, the whole details of the accident has not been revealed.
The NRA continues to work with various research institutes to investigate and analyze how
and what occurred in the accident.
I myself have visited Fukushima Daiichi NPS eight times in this couple of years and observed
the reactor buildings directly to lead the investigation activities.
Last year TEPCO surveyed the inside of Unit 1 containment vessel and it was revealed thatthe concrete pedestal under the reactor pressure vessel was severely damaged in the way
we had not expected.
Observed peculiar damage is like that concrete part is lost with reinforcing steel bars onlyremaining. The mechanism of this situation has not been clearly explained so far.
Likewise, we are conducting research on a variety of issues that need to be elucidated.

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The NRA will never forget the accident which originated us, and continue to tackle with issues
in the Fukushima Dai-ichi NPS.
I have worked on these issues with three focused areas I mentioned in mind. Our efforts tofurther strengthen the nuclear safety will never end, and we continue to improve ourorganization, nuclear regulation, radiation protection measures and situation of TEPCO’s
Fukushima Dai-ichi NPS.
We are pleased to welcome you and close by wishing fruitful discussions, successful thisconference.