The 35th International Geological Congress, Cape Town, South Africa (Aug. 28-Sep. 2, 2016)
Monday, Aug. 29, 2016, Session T8.2, “Geohazards and societal benefits: coping with reality /Risk evaluation and management in the 21st Century”, Hall 4B2, 17:00-17:15, #2221. Ver. 7

Japan’s Nuclear Regulation
Standards against Natural
Hazards after Fukushima（日本の福島後の原子力新規制基準の自然災害への対応）

Akira ISHIWATARI
Commissioner of Nuclear Regulation
Authority, Japan (D.Sc., Geologist)（石渡 明（原子力規制委員会委員））
The slides were slightly corrected and edited after the presentation.
1NRA’s New Regulation Standards against
Natural Hazards after Fukushima
accident (Mar. 11, 2011)
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.
(NRA was established on Sep. 19, 2012)2

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 areaInput▼Tsunami
Seawalls
Tsunamimonitoringequipment

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.

3

Clarification of requirements
for fault displacement“Capable faults” need to be determined as those whose
activities 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)

4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 basal age of the 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

5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 setat 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)

6

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.
7

Tsunami sources
Nagasaki spur fault(length:86km, Mw7.6)
Northern and central part ofRyukyu 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.

8Unit 2 C/V

Unit 1 C/V

Tsunami protection
Sea wall & Water tight doors(+15.0m from sea level)

T/B

Sea water pumps

Tsunami protection Bank(+8.0m from sea level)

Copyright, Kyushu EPC

NPPs Tsunami Height
Sendai
2.0m
Ikata
1.9m
Takahama 1.7m

Input Tsunami
7.0m
8.7m
6.7 m

Sea water pool(for taking water attsunami withdrawal)

Site Elevation
13m
10m
3.5m

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

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

D-45 D-48
Mar. 19, 2014, East
China
Assessment
Sea
Meeting #95,Doc. 2-1, p. 81,
Sendai NPPs, Reactor #2
Fault (Kyushu Reactor #1EPC)

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.

10300 m10

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)

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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 Ma

SendaiNPP

Kushikino Gold Mine
3.4-3.9 Ma
Mar. 19, 2014, Assessment Meeting #95
Doc. 2-1, Sendai NPPs (Kyushu EPC)

12
Izawa, E. (2004) Chishitsu
News, 599, 49-54 (in Jpn.).
12

Capable faults (near site <30km)
Blue: Fault length assessedby Kyushu EPC
Red: Fault length assessed by
the Headquarter forEarthquake 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)
13

Design Basis Ground Motion of Sendai NPPs(DBGM)
Hypocenters identified
Ss-1

Hypocenters 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
Copyright, Kyushu EPC

Horizontal movement

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.)

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-)14

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)

15

2016 Kumamoto Earthquake
Apr. 14, M6.5 and Apr. 16, M7.3; 50 deaths,>2,000 injuries and >180,000 evacuees.

Epicenter ofMain ShockBeppu-Haneyama Fault

Futagawa Fault

Surface Fault Trace:
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
MeteorologicalAgency)
Kyushu EPC’sevaluation of theFutagawa-Hinagu
Fault in the Sendai
NPP Reassessment:
93 km, M8.1

Hinagu Fault
Sendai NPP

Japan Meteorological Agency

16

Apr. 23, 2014 Assessment Meeting#107 Sendai NPPs, Kyushu EPC

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.
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 to
be deposited in
the NPP site
during its
operation:
NPP
Ash
Sendai 15 cm
Ikata
15 cm
Takahama
10 cm

Kikai
17Conclusion (Principal aims of NRA)
Protect human life & environment – our goal
Independent scientific & technical decisions
Field-based, effective regulation
Open & informed regulation processesProfessional moral & ability by daily studies
Immediate & organized action at crisis

Thank you for your kind attention.
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