IAEA Technical Meeting on Lessons Learned and Safety Improvements Related to External
Hazards Based on the IAEA Fukushima Daiichi Accident ReportVienna, Austria, 23–25 November 2016, Board Room C, Ref. No.: J20-TM-52527

Japan’s Nuclear Regulation
against Natural Hazards after
the Fukushima Daiichi Accident
Akira ISHIWATARI
Commissioner of NuclearRegulation Authority,
Japan (D.Sc., Geologist)1

Thanks
Five years have passed since the March2011 Fukushima Daiichi nuclear accident.
To prevent recurrence of such a disaster,
Nuclear Regulation Authority (NRA)* wasestablished in September 2012. NRA has
worked hard for keeping nuclear safety
and improving nuclear regulation. NRA
expresses sincere thanks to IAEA and its
member countries for their kind help inreconstructing Japan after the Fukushima
Daiichi accident.
*Five commissioners and thousand staffs

2Thanks
I thank IAEA for giving me a chance of thispresentation. I am glad to contribute tointernational nuclear safety by presenting
our knowledge learned from experience ofthe Fukushima accident.
Fukushima dictates that “perfect safety” or“ultimate preparedness” does not exist innuclear safety. We keep going for further
improvement of nuclear safety in Japan
with international understanding.
3

NRA’s New Regulation Standards against
Natural Hazards after the Fukushima
accident (Contents of this Presentation)
More stringent standards on tsunami
Clarification of requirements for fault
displacement
More precise methods to define design basis
ground motion (DBGM) by earthquake
Assessment & monitoring of volcanic activity
An example: Sendai Nuclear Power Plants(NPPs), Kyushu Electric Power Co.
4

More stringent Standards on Tsunami
Define “Design Basis Tsunami” that exceeds
the largest in the historical records
Requirements for multiple protective measures
Preventing inflow(High-level seismic design)

Limiting theinundation area

Input
▼Tsunami
Seawalls
Tsunamimonitoring
equipment

Watertightdoors▼Design Basis Tsunami(at X kmoffshore)▼Normal level

Water supply for cooling must be available even incase of lowered water level at tsunami withdrawal.

5Sites affectedby the Mar. 11,
2011 Tohoku
Tsunamis

Tsuruga

Monju
MihamaTomari

Higashidori

Ohi
Takahama
Shika
ShimaneTokai

Genkai
Hamaoka
SendaiKashiwazaki-Kariwa
Fukushima Daiichi
Fukushima DainiTEPCO plants

Onagawa

Ikata“Operational Statusof Nuclear Facilitiesin Japan” by JNES
(2013)

6Mar. 11 Tsunamis at NPPs
NPP

Tsunami Height(Mar. 11, 2011)

Input Tsunami(before Mar. 11)

Input Tsunami(after Mar. 11)

Higashidori

4 m [13 m]

6.5 m

11.7 m*Onagawa

13 m [15 m]*

9.1 m

23.1 m*Fukushima Daiichi

15 m [10 m]

5.4 – 5.7 m

26.3 m** (14.13 m)

Fukushima Daini

15 m [12 m]

5.1 – 5.2 m

27.5 m***Tokai

5 m [8 m]

5.7 m

17.1 m*Site caused
severe accident
Site affected bytsunami[ ] Site elevation*Site subsided 1 mby the earthquake(Elevation was 14m at tsunami input)*Currently underevaluation or not
yet evaluated**For consideration***Proposed byTEPCO

Data from various sources (Credit: A. Ishiwatari)7

Clarification of requirements
for fault displacement“Capable faults” need to be determined as those whoseactivities since the late Pleistocene (approx.120,000 to130,000 years ago or later) cannot be denied
Important facilities have to be constructed on the groundwithout outcrop of capable faults
Risk of loss of safety
Important facilities：for“Shut-down, Cooling,Containment”

function by the damageof the buildings andequipment

Movement of afault○Movement of the fault under important facilities like Reactor Building may result in
the concentration of deadweight onto the spot and cause damage of the building.
○Even in case damage of the building is avoided, safety function can be lost due to thedeformation of the facilities or damages of the internal equipment.
https://www.nsr.go.jp/data/000070101.pdf (2013)8How to find a capable fault?
1. Covering Bed Method
Geologicalage of bed

younger“Capable fault” is the official term for “activefault” that is defined in IAEA Safety Standards
Series No. SSG-9 “Seismic hazards in site
evaluation for nuclear installations”. The “120130 ka” is the base age of Upper Pleistocene.

120-130
thousandyears(ka)olderJudge:
2. Crossing
Vein Method120-130 ka
dike or vein

Capable Fault

Capable Fault
CapableFault

Not Capable Fault
Not CapableFault

9On-siteCapableFault
Evaluation

Tsuruga

TomariMonju
MihamaHigashidori

Ohi
Takahama
Shika
Shimane

Tokai

Genkai
Hamaoka

Kashiwazaki-Kariwa
Fukushima Daiichi
Fukushima DainiTEPCO plants

Onagawa

Ikata
Sendai“Operational Statusof Nuclear Facilities
in Japan” by JNES
(2013)

13

On-site capable fault evaluation
NPP

by Specialists or NRA

Evaluation Result

Higashidori

Specialists

Capable Fault*

Shika

Specialists

Capable Fault*

Tsuruga

Specialists

Capable Fault*

Monju

Specialists

Not Capable Fault

MihamaSpecialists and NRA

Not Capable Fault

Ohi

Specialists

Not Capable Fault

Takahama

NRANot Capable Fault

IkataNRA

Not Capable Fault

SendaiNRANot Capable Fault

Site operation permitted(Ikata and Sendai arecurrently on operation)

Credit: NRA*Evaluation of fault(s) directly
beneath the reactor is not
fixed (on evaluation by NRA)

Note: Specialists’ evaluation is (will be) taken as
important information in the final NRA’s judgment.

11More precise methods to define
Design Basis Ground Motion (DBGM)
Survey 3D geological structure of the site
Take into consideration of seismic groundmotion predication
Engineering Basement (Vs>0.7km/s)

Seismic
DBGM is set
at this depth

Seismic Basement (Vs>3km/s)

hypocenter

Unique underground structure to amplify theground motion

https://www.nsr.go.jp/data/000070101.pdf P.14 (2013)12

Sites experienced
stronger seismic
motions than theTomari
old DBGMs

Monju
MihamaHigashidori

Ohi
Takahama

Onagawa
Shika

Shimane

Tokai

Genkai
Hamaoka
Sendai

Kashiwazaki-Kariwa
Fukushima Daiichi
Fukushima DainiTEPCO plants

Tsuruga

Ikata“Operational Statusof Nuclear Facilities
in Japan” by JNES(2013)10

Sites experiencing earthquakes with strong
motions larger than the old DBGMs3) (gal = cm/s2)
NPP site

Earthquake
NameDate

Magnitude
Mw

PGA
basematDistance
to siteCredit: NRA
Operation
StatusOnagawa

Miyagi-Oki
earthquake

August 16,
2005

7.1316 gal 1)

84km

SCRAM at Units#1, 2, 3

Shika

Noto Peninsula
earthquake

March 25,
2007

6.7

226 gal 1)

18km

Under periodical
inspection

Kashiwazaki-Kariwa

Chuetsu-Oki
earthquake

July 16,
2007

16km

SCRAM at Units #3, 4,
7. Others; underperiodical inspection

Onagawa

Tohokuearthquake

March 11,
2011

125km

SCRAM at Units #1 &3. Unit 2; underperiodical inspection

Fukushima
DaichiTohokuearthquake

Onagawa

Miyagi-Oki
earthquake

6.6680 gal 2)

9.0

607 gal 2)

March 11,2011

9.0550 gal 2)

180km

SCRAM at Units #1, 2,
3. Others: underperiodical inspection

April 7,2011

7.1

398 gal 1)

78km

Under periodical
inspection

1) Response spectra exceeded the design basis ground motion (DBGM, Ss or S2) at some periods
2) Peak ground acceleration (PGA) and response spectra (at some periods) exceeded the DBGM (Ss or S2)
3) Design basis ground motions (DBGMs) before and after the March 11, 2011 Tohoku Earthquake (at 50 Hz):
SiteOnagawaShika
Kashiwazaki-Kariwa Fukushima-Daiichi
Before 580 gal
600 gal450 gal*
600 gal (*Before back check)
After
1000 (on evaluation) 1000 (on evaluation) 1209-2300 (on eval.) 900 (for consideration)144) SCRAM threshold ground acceleration at Kashiwazaki-Kariwa: horizontal =120-185 gal, vertical = 100 gal

Reassessment of Sendai Nuclear
Power Plants (NPPs): an example
Time sequenceof reassessment

Copyright, Kyushu EPC••••

Owned by Kyushu EPC
2 PWRs, 890,000kW each
About 30 years operation
Front onto East China Sea(not to plate boundary)Jul. 8, 2013
Back-fit safety assessment completed
Jul. 16, 2013
Examination by NRA commissioners and secretariats started.
>60 times open-to-public meetings~700 times closed meetings
Revision after public comments
Sep. 10, 2014
Permission for basic design decided.
Sep. 10, 2015 and Nov. 17, 2015
Commercial operation of Reactors #1
and #2 restarted, respectively. Bothreactors are currently on operation.
15

Tsunami sources
Nagasaki spur fault(length:86km, Mw7.6)
Northern and central part of
Ryukyu trench(length:approx.900km, Mw9.1)

Sendai NPPs

Eurasia Plate
Philippine
Sea Plate

Copyright, Kyushu EPC

Ruptureinitiation
point

NRA required to estimate thetsunami height caused bynorthern and central part of
Ryukyu trench** Any tsunami caused by this wide
area have never been recorded, but
the possibility to break several
segment simultaneously, as in caseof the Great East Japan Earthquake,should be considered.

16Unit 2 C/V

Unit 1 C/VTsunami protection
Sea wall & Water tight doors(+15.0m from sea level)

T/BSea water pumps

Tsunami protection Bank(+8.0m from sea level)

Copyright, Kyushu EPC

NPPsSendai
Ikata
Takahama
Mihama

DBT
2.0m
1.9m
1.7m
3.3m

Input Tsunami
7.0m
8.7m
6.7m
4.2m

Sea water pool(for taking water attsunami withdrawal)

Site Elevation
13m
10m
3.5m
3.5m

Design Basis
Tsunami (DBT) ofSendai NPPs iscalculated at thepoint 8 km offshore
and 50 m waterdepth.
Input Tsunami Heightis the maximum atthe site waterfront.
Site Elevation is theground height wherereactors are placed.

17Capable faults on site?
Geological Map of the Sendai Nuclear Power Plant site

D-45 D-48
EastChina
Sea

Two reactors are built on
the Cretaceous
conglomerate bed.
The longest and youngest
faults (e.g. D-45 and D48) are selected for
detailed assessment.

Mar. 19, 2014,
Assessment
Reactor #2
Meeting #95,
Doc. 2-1, p. 81, Reactor #1
Sendai NPPs,Fault (KyushuEPC)

18

300 m

18

Mineral veins cutting fault zones
D-45 fault zone is cut by a quartz vein including chlorite and illite (p.109)
The newest
rupture planesof fault zones
are indicated byred arrows.
D-48 fault zone is cut by calcite veins (p. 117)
Chlorite andillite are alsopresent in thefault zones.

Mar. 19, 2014, Assessment Meeting #95
Doc. 2-1, Sendai NPPs (Kyushu EPC)

19

Age of hydrothermal veins: 3 Ma in the Sendai-Kushikino area

On-site faults of Sendai
NPPs formed before (orgeologically at the sametime with) the 3 Ma hydrothermal activity. Thus they
are not capable faults.
Hishikari Gold Mine
0.7-1.2 MaSendaiNPPKushikino Gold Mine
3.4-3.9 Ma
Mar. 19, 2014, Assessment Meeting #95
Doc. 2-1, Sendai NPPs (Kyushu EPC)

20
Izawa, E. (2004) Chishitsu
News, 599, 49-54 (in Jpn.).
20Capable faults (near site <30km)
Blue: Fault length assessedby Kyushu EPC
Red: Fault length assessed by
the Headquarter for
Earthquake Research
Promotion (HERP)
Sendai NPPs

Ichiki Fault

Copyright, Kyushu EPC

NRA required to extend thelength of faults to fit thelength assessed by HERPThe nearest faults are used
for calculation of Design
Basis Ground Motion (DBGM)(Mar. 12, 2014 Assessment
Meeting #92. Copyright:
Kyushu EPC)
21

Design Basis Ground Motion of Sendai NPPs(DBGM)
Source specified
Hypocenter identified
Ss-1

Source unspecified
Hypocenter unidentified
Ss-2

Ss-2 is based on the 2004
Rumoi Earthquake (M5.7),
Hokkaido (Sato et al. 2013)

Koshiki Fault
Ichiki Fault
Koshiki Strait Fault
Horizontal movement

Copyright, Kyushu EPC

Horizontal movement

Seismic accelaration of DBGM:(gal = cm/s2)
Sendai:540 gal (Appl.) >>> 620 gal (Reassess.)
Ikata:
570 gal (Appl.) >>> 650 gal (Reassess.)
Takahama: 550 gal (Appl.) >>> 700 gal (Reassess.)
Mihama: 750 gal (Appl.) >>> 993 gal (Reassess.)

Ss-1 andSs-2 are
DBGMs forSendai NPPs.
The Ss-2“hypocentersunidentified”
earthquake isassumed tooccur in theearth’s crust
just beneaththe NPPs.
The Ss-2 islarger thanthe Ss-1 insome periods.

Calculation is based on Irikura andMiyake (2001; J. Geogr., 110, 849-;
2011; Pure Appl. Geophys., 168, 85-)22

Capable faults (near site <100km)
Kumamoto
NagasakiSendai NPPs
Kagoshima

Kyushu EPC’s evaluation of
Futagawa-Hinagu Fault is
93 km long and M8.1,assuming a full-length rupture.
Equivalent epicenter distancefrom Sendai NPPs is 104 km.
The Futagawa-Hinagu
Fault caused M7.3
Kumamoto earthquake
on Apr. 16, 2016 andassociated numerous
disastrous earthquakes.
(Mar. 12, 2014 Assessment
Meeting #92. Copyright:Kyushu EPC)

23

2016 Kumamoto Earthquake
Apr. 14, M6.5 and Apr. 16, M7.3; 50 deaths,>2,000 injuries and >180,000 evacuees.
50 km
Epicenter ofMain ShockBeppu-Haneyama Fault

Surface Fault Rupture:
Futagawa: 28 km
Hinagu:6 km
Fault Length bySatellite-based Ground
Movement:
Futagawa E: 5 km
Futagawa W: 20 km
Hinagu:10 km(Data from Japan
Meteorological Agency)

Futagawa Fault
Kyushu EPC’s
evaluation of the
Futagawa-Hinagu Fault
in the Sendai NPP
Reassessment:
93 km, M8.1
Hinagu Fault
Sendai NPP

Japan Meteorological Agency

24

Protection of NPPs from volcanic hazards
Utility companies should survey Quaternary volcanoes within 160 km from theNPP, and assess their eruption histories, geothermal activities, distribution oflavas, pyroclastic flows and ash, etc.
(Apr. 23, 2014 Assessment Meeting #107 Sendai NPPs, Kyushu EPC)
In case if apyroclastic flow
reached the NPP
site in the geologic
past, the company
should conduct
seismic andgeodetic monitoringof the source
caldera volcano.
This is the case for
Sendai NPPs.

R=160 km area

Aso

Kirishima
Sendai NPP

Aira
Ata

Quaternary
volcanoCaldera(not to scale)

Evaluation ofvolcanic ash tobe deposited in
the NPP site
during its
operation:
NPPAshSendai
15 cm
Ikata
15 cm
Takahama 10 cm
Mihama 10 cm

Kikai25Conclusion (Action Principles of NRA)
Protect human life & environment – our goal
Independent scientific & technical decisions
Field-based, effective regulation
Open & informed regulation processes
Professional moral & ability by daily studies
Immediate & organized action at crisis
Enhance nuclear safety & security culture

Thank you for your kind attention.
Presentation by Akira Ishiwatari, NRA Commissioner

26