Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanFRAGILITY ENHANCEMENT IN SEISMIC-TSUNAMIRISK REDUCTION FOR NUCLEAR POWER PLANTS
Naotaka TAKAMATSU1､ Hiroyuki KAMEDA2 and Katsumi EBISAWA3
1

2

Deputy Director General, JNES, Tokyo, Japan takamatsu-naotaka@jnes.go.jp
Professor Emeritus, Kyoto University and Technical Counselor, JNES, Tokyo, Japan
kameda2@minuet.plala.or.jp
3
Associate Vice President, JNES, Tokyo, Japan ebisawa-katsumi@jnes.go.jp(JNES: Japan Nuclear Energy Safety Organization)

ABSTRACT: As major engineering tools for seismic-tsunami risk reduction at nuclear
power plants, we propose a framework of fragility enhancement of plant structures,
systems, components. A key issue is to eliminate cliff-edge effects at electrical devices
under tsunami actions. It is pointed out that fragility enhancement is achieved by realizing"smooth fragility" and/or "safe re-location". It is proposed to consider many other types ofcomponents that are subjected to various load effects such as inundation, hydrodynamic
forces, scouring, buoyancy, and uplift. Engineering options with "Water Proof, Structural
Resistance and Dry Siting" are proposed.

Key Words: Multi-units, Tsunami Design, Seismic-Tsunami PSA, Fragility, Cliff Edege

1. INTRODUCTION
The Tohoku earthquake (Mw9.0) occurred at 14:46 on March 11, 2011, and caused a huge tsunami.
strong seismic ground motion was observed at the Fukushima Dai-ichi nuclear power plant (F1-NPP)
and reactors were shut down after control rods had inserted. While the reactors were shut downnormally, they were attacked by tsunami about 46 minutes after the earthquake occurred. Various
components of the water intake systems and emergency diesel generators were flooded. External
power supply was also lost due to damage by strong seismic motions and tsunami. In this situation,
station blackout occurred. As a consequence, functions of reactor cooling system was lost, coredamage (CD) occurred and radioactive materials were released to the off-site area (Japanese
government 2011).
As major engineering tools for seismic-tsunami risk reduction at NPPs, we propose a frameworkof fragility enhancement of plant structures, systems, components (SSCs). A key issue is to eliminate
cliff-edge effects at electrical devices under tsunami actions. It is pointed out that fragility
enhancement is achieved by realizing "smooth fragility" and/or "safe re-location" later. It is proposed
to consider many other types of plant components that are subjected to various load effects such as
inundation, hydrodynamic forces, scouring, buoyancy, and uplift. Engineering options with "Water
Proof (WP), Structural Resistance (SR) and Dry Siting (DS)" are proposed. It is pointed out that1586

combined action of strong seismic motions and tsunami attack with a time lag should be considered.
These notions are closely related to the experience of the 2011 Tohoku earthquake and tsunami
disaster and the performance of NPPs in the disaster area, where some "failed catastrophically" butsome "failed gracefully".
This paper describes the overview of tsunami disaster of NPPs by Tohoku earthquake and tsunami
and various types of load effects by tsunamis. The outline of fragility evaluation on tsunami PSA is
also described. Then the paper represents the proposal of concept of "Tsunami Resistant Technology"
as fragility enhancement of SCCs. Further based on the above concept, typical examples of SSC
design and enhancement for tsunami protection of NPP and example of implementation of WP, SR and
DS are described.
2. TSUNAMI DISASTER OF NUCLEAR POWER PLANTS AND VARIOUS TYPES OF
LOAD EFFECTS BY TSUNAMI
2.1 Nuclear power plants(1) Fukushima Dii-chi NPP
The tide level observation system consists of the tide gauge (quiet area in the harbor) and therecording device at building. The arrival time and tsunami height of first big wave were 41 min after
the main shock and O.P. about 4 m respectively. The arrival time /tsunami height of second big wave
were 8 min after the first big wave the water level is unknown due to tide gauge failure, max. scale of
the gauge is 7.5 m respectively. The tsunami height was more than 10 m that the experts estimated tobe more than 10 m from the picture showing the overflow status of tsunami seawall (10 m).
Tokyo Elec. Power Co. (TEPCO) evaluated the design tsunami height based on Japanese Society
Civil Engineering (JSCE) guide (2002), assessing Shioyazaki EQ. (M7.9) as M8.0 voluntary, and thehighest water level of each Unit was set as 5.4 to 5.7 m. The design tsunami height (5.7m) is lower
than the tsunami height (10m). The site height (10 m) is lower than the inundation height (14m).
As to the sea water pump facilities for component cooling (height: 5.6 to 6 m), all Units were
flooded by tsunami as shown in Fig.1. Whether or not they were damaged by wave power is underinvestigation. The Emergency Diesel Generators (EDGs) and switchboards installed in the basement
floor of the reactor and the turbine buildings (height: 0 to 5.8 m) were flooded except for Unit 6, andthe emergency power source supply (EPS) was lost. Regarding Unit 6, two out of three EDGs were
installed in the first basement of the RB and was flooded, but one DG installed on the first floor of DG
building was not flooded and the EPP supply was possible.
F1-NPP was inundated heavily beyond its tsunami protection capabilities, and lost all of them.
Reactorbuilding
原子炉建屋
Turbinebuilding
タービン建屋+5m

Coolingsea water
海水ポンプ
pump
motor
モーター
Sea water Seawall (height: 10m)
+10m
pit
+5.6m intake
取水ピット
+5m
Sea surface: 0m
海面：0m

ディーゼル
Emergency
発電機室
DieselGenerator
room

取水配管
海水ポンプ
Cooling sea waterpump

Fig.1 Illustration of sea water supply system and situation oftsunami disaster at Fukushima Daiichi nuclear power plant1587

(2) Tokai Dai-ni NPP
The arrival time and tsunami height of first big wave were 30 min after the main shock (14:46) and
O.P. about 5.4 m respectively. The record of tide gauge was not recorded because the power supply
was disrupted from16:40 and the tsunami height exceeded the tsunami measurement scale.
The design tsunami height was H.P.+5.8 m. The design tsunami height (5.8m) is lower than theinundation height (6.3m). The site height (6.1 m) is lower than the inundation height (6.3m).
When the earthquake hit the site, the north emergency seawater pump room was under levelingconstruction of its sidewall as protection against tsunami. The construction work put in place a new
sidewall up to H.P. +7.0 m outside the existing sidewall, but the waterproof sealing of the penetrationof the wall had not been completed as shown in Fig.2. The tsunami flooded the north emergency
seawater pump area in the seawater pump room through the small holes. One of three seawater pumps
for EDGs was submerged, and one of three EDGs stopped. The other two EDGs were able to operate,
successfully ensuring emergency power supply.
Tokai Dai-ni plant where inundation was slight and light enough was able to avoid total loss ofthe terminal heat sinks.
(3) Onagawa NPP
The arrival time of first big wave was 43 min after the main shock (14:46). The observed
maximum tsunami height was O.P. about 13 m. Height of site was 14.8 m. Subsidence due to crustal
deformation was about 1m.
Onagawa district is featured with a ria-coastline. In this area, lessons learnt from historical tsunami
disasters have taken root as a local climate. To apply for Establishment permit, Tohoku Elec. PowerCom. listened from many local residents on tsunami run-up height and damage, and reflected them inthe site height of 14.8 m. The design tsunami height (13.6m) is larger than the observed height (13m).
The site height (13.8 m) considering the 1m ground subsidence is larger than the observed height(13m).
Component cooling system consists of intake channel/seawater pump/ seawater pump room/ heatexchanger room as shown in Fig.3. The seawater pump room was designed as the height of 14.8 m andabout 100 m away from the coast to prevent the inundation by run-up tsunami. Inside the room, thetide gauge is installed with an opening. Tide gauge is to allow the automatic stop of the seawater pumpin short of seawater due to the backrush of a tsunami. The tsunami did not attack the seawater pumproom directly. The seawater overflowed in the room through the opening of gauge. Then the seawater
flowed from the pump room, via the trench, into the basement floors of the reactor buildings, causing
the heat exchanger room of the component cooling water system in the second basement to besubmerged. The component cooling water pump of Unit 2 was also submerged, which thereby caused
the cooling function of EDGs to be lost, with two units stopped out of those three generators.

South side

North side

Side wall H.P. +7.0 (ASL+6.11m): Completed
Water seal of penetrations: Completed

Water seal of penetrations:
Not yet completed

Circulation water
pump area

Emergency sea water pump area

Side wall H.P. +7.0 (ASL+6.11m):
Completed

Fig.2 Illustration of sea water supply system and situation oftsunami disaster at Tokai Daini nuclear power plant

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Tsunami height:
about 13m*

Site 13.8m*
潮位計
Tide gauge（津波浸入）

R/B (Accessory
structure)

Sea water pump

R/B

Opening of gauge
Trench浸水

Design height:
9.1 m

Heat exchanger

Intake port

pump of the component cooling system（津波浸入）

Inundation of tsunami

Fig.3 Illustration of sea water supply system and situation oftsunami disaster at Onagawa nuclear power plantFig.4 Inundation at Fukushima Daiich NPP

Fig.5 Inundation at Onagawa NPP

Tohoku Electric Power Comp. Inc. took measures to prevent the piping penetrations and the cabletray penetrations from the seawater pump room to the trench. They would set up a flood barrier aroundthe seawater pump room. Then the seawater flowed from the pump room, via the trench, into thebasement floors of the reactor buildings, causing the heat exchanger room of the component coolingwater system in the second basement to be submerged.
The component cooling water pump of Unit 2 was also submerged, which thereby caused thecooling function of EDGs to be lost, with two units stopped out of those three generators.
Tohoku Electric Power Comp. Inc. took measures to prevent the piping penetrations and the cabletray penetrations from the seawater pump room to the trench. They would set up a flood barrier aroundthe seawater pump room.
The Onagawa NPPs where inundation was slight and light enough were able to avoid total loss ofthe terminal heat sinks.
2.2 Various types of load effects by tsunamis
The authors have investigated seismic and tsunami disaster caused by Tohoku earthquake. Basedon this investigation results, various types of load effects by tsunami are described. We must be awarethat there are various types of load effects by tsunami to be considered: inundation, hydrodynamic
forces (impulsive, sustained in push-pull), scouring, buoyancy, and uplift.
(1) Inundation
The Fig.4 shows the inundation at F1-NPP. The Fig.5 shows the inundation that the seawater flew
in the basement of reactor building through intake tunnel-pump pit-trench due to siphon effects at
Onagawa NPP. We must be careful. Seawater flowed into the basement of the reactor building throughthe intake tunnel, pump, pit and trench due to siphon effects. So we must be aware that water creeps inanywhere if there are accessible paths and head difference.
(2) Effects of hydrodynamic forces
The Fig.6 (a)-(c) shows another very different picture of water-related hazards from groundmotion effects. The Fig.6 (a) is the effects of the hydrodynamic forces were bent steel pillars in
Onagawa town. The Fig.6 (b) is the seawall gate in Miyako city, this is a very strong one but wasdestroyed by the impulsive tsunami force. The Fig.6 (c) is the tsunami flew over the tsunami wall of
15.5 m at Fudai River in Fudai village. It broke maintenance girders like the photo, but the main
structure remained intact.

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(3) Scouring, buoyancy and uplift
The Fig.7 (a)-(d) shows about scouring, buoyancy and uplift. We can observe that this seawall
toppled because of scouring as shown in the Fig.7 (a)-(b). The Fig.7 (c) is the condition that the fueltank floated and dislocated at Onagawa NPP. We can say so because this space has not been disturbed
at all. The Fig.7 (d) is concrete from a bridge. It was not dislocated like the photo, but it was uplifted
once and then transported. We can say so because of many evidences of multiple failures, so uplifteffects are also these ways.

(b) Sea wall gate destroyed by
impulsive tsunami force at Miyako city(a) Bent steel pillars at Onagawa town(c) Tsunami flew over the tsunami wall across Fudai River (TP+15.5m),
and broke maintenance decks / main structure stayed intact at Fudai village

Fig.6 Effects of hydrodynamic forces(a) Seawalls toppled due to scouring at Miyako city(b) Seawalls toppled due to scouring at Miyako city(c) Fuel tank floated and dislocated (Tohoku EPCO) (d) Bridge decks pulled up from the piers and transported
at Onagawa town
(by K.Kawashima) at Rikuzen-Takada city

Fig.7 (a)-(d) Scouring, buoyancy & uplift15902.3 Success example of tide embankment, and ancient instruction and observance
The authors have investigated seismic and tsunami disaster caused by Tohoku earthquake andconfirmed success example of tide embankment, and ancient instruction and observance.
The 10m-high tide embankment in Taro district with a local nickname of “the Great Wall ofChina”, was destroyed by the 15m-high tsunami as shown in Fig.8(1). However the 15.5m-high tideembankment in Otabe district in Fudai village was constructed according to the village chief’s strong
willing as shown in Fig.8(2). This blocked the 15 m-high tsunami and successfully protected thehouses in this district. As a lesson learnt from great damages caused by the past tsunamis, local
wisdom against a15m high tsunami has been widely disseminated. In contrast to the failure of disasterprevention in the former 10 m-high embankment case, the construction of the latter 15.5 m
embankment with the local wisdom led to “a peace consequence” (Japanese government 2011).
The stone monument stands at the Aneyoshi district in Miyako city as shown in Fig.9(1). As
lessons learnt from past experience of the tsunami disaster, the inscription reads as “Do not build any
house below this stone”. Run-up height of 38.9 m by Tohoku earthquake was observed as shown in
Fig.9(2). Thanks to having followed this ancient instruction, Tohoku earthquake did not claim a single
casualty in this district. It is seen that the fate depended on whether this kind of previous tsunami
lessons had been reflected in tsunami design or not (Japanese government 2011).

(2) Ohtabe district in Fudai village(1) Tao district in Miyoko city

Fig.8 Success example of tide embankments(1) A photo from the village’s point of view
(Average height of district: about 60 m)(2) A photo from a viewpoint of facing the village
taken at the spot slightly below the stone monument

Fig.9(1)-(2) Ancient instruction and observance in Miyako city1591

3. PROCEDURE OF TSUNAMI FRAGILITY ON TSUNAMI PSA
3.1 Procedure of the Seismic PSA
The procedure of tsunami PSA consists of 4 steps as shown in Fig.10 (Sugino 2008).
-Step 1: Collection of information related to earthquake and setting of accident scenario- Step 2: Tsunami hazard evaluation- Step 3: Fragility evaluation- Step 4: Accident sequence evaluation
3.2 Tsunami fragility evaluation(1) Procedure of tsunami fragility evaluation
The Fig. 11 shows the evaluation procedure of tsunami fragilities. On the fragility evaluation oftsunami, fragility curves are obtained as the conditional probability that tsunami wave height exceeded
the installation height of targeted structures and components as shown in figure.
Tsunami wave heights are evaluated by conducting analysis of onshore run-ups to the area thattargeted buildings, structures and components are installed. Evaluate uncertainties and dispersion of
the wave heights of tsunami wave run-ups.
(2)Damage part, damage mode and its physical quantities for evaluation of tsunami fragilities
It is important to identify the modes (inundation, hydrodynamic forces (impulsive, sustained inpush-pull), scouring, buoyancy, and uplift) on function failure against tsunami in case of targeting
facilities outside and inside of buildings. It is also important to identify their functional failure limits
and intensities of tsunami. The intensities of tsunami are consisted of tsunami wave height, tsunami
wave force, scour etc.
The failure parts, failure modes and physical quantities representing functional failure limits aredifferent for each targeted structures and components. For quantitative evaluation of tsunami margins,attention should be paid that physical quantities representing margins would differ as the failure partsand failure modes to be evaluated are also different based on targeted structures and components.
(3)Examples of Fragility Evaluation
The Fig. 12 shows an example of fragility evaluation. The results on analysis of onshore run-ups
of tsunami are shown for targeted point in the Fig.12. The Fig.12 shows the result of fragility
evaluation in case of assuming the installation point of reactor building is 600 m distant from theshoreline, and function failure is occurred when tsunami run-ups reaches to the building.
3.3 Concept of seismic-tsunami PSA methodology
The concept and important issues for developing seismic-tsunami PSA methodology considering the
combination of seismic and tsunami events at multi-units has been examined (Ebisawa 2012). This
concept and important issues consists of the following four viewpoints; setting of accident scenarios,
seismic-tsunami hazard evaluation, seismic-tsunami fragility evaluation and seismic-tsunami accident
sequence evaluation.

(2) Tsunami Hazard Evaluation
Tsunami Source Modeling
Tsunami Analysis

ExceedanceFrequency (1/yr)

Tsunami hazard curve

Tsunami run-up analysis(1) Collection of information related to Tsunami and
Setting of accident scenario(3) Tsunami Fragility Evaluation
Tsunami inundation evaluation
Capacity (height) of SSCs
Function Failure Probability evaluation(4) Accident Sequence Evaluation
Accident sequence modeling( Event Tree, Fault Tree )Occurrence Frequency of accident

Tsunami height at shoreline (m)Fig.10 Procedure of tsunami PSA

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Result of analysis

Max. tsunami heightat shoreline

Functional Failure
Probability

Total
number of Realistic
Tsunami● : analysis

10

Max. Tsunami height (m)Max. Tsunami height (m)Inundation height at 600m

600m from shoreline

86Function failure height

4
2
0
0

2

4

6

8

10

R/B

Function lfailure
height assumed
TP+4.5m

R/B assumed at the 600 m fromshoreline

Tsunami fragility curve

Run-up analysis

Inundation heightFragility curve

Functional Failure
Probability

Tsunami simulation

Function failure height

Inundation height (m)Realistic Tsunami set
Real：amplitude, period

Inundation height (m)Facility set

1.0
0.8

Tsunami fragility curve

0.6
0.4
0.2
0.0
0

2

4

6

8

10

Max. Tsunami height at shoreline (m) Max. Tsunami height at shoreline (m)Fig.12 Example of tsunami fragility evaluation

Fig.11 Procedure of fragility evaluation

Fig.13 Enhancement of fragility under tsunami threat （Kameda 2011, Kameda 2012）

4. PROPOSAL OF “TSUNAMI RESISTANT TECHNOLOGY” AS FRAGILITY
ENHANCEMENT OF SSC
4.1 Proposal of "Tsunami Resistant Technology” as fragility enhancement of SCC
The practical risk reduction is realized through the enhancement of fragility function. This is themost important engineering practice. Of course, hazard assessment and accident scenario evaluation
are also important. But the most direct way to enhance the risk reduction is the enhancement offragility (Kameda 2011, Kameda 2012).
Vulnerability of electric devices to water intrusion (like switch boards, motors for seawater pumps,
cables, etc.) should be drastically improved. This is a very specific feature of tsunami protection,compared to ground motion protections. We have seen the cliff-edge effects drastically as shown in
Fig.13. If the tsunamis exceeded the design, then we suddenly get 100% malfunction. This is extreme
dangerous, so eliminating the cliff-edge effect through making smooth fragility or relocating to a safe
location. We need to do this kind of enhancement.
4.2 Elements of Tsunami Resistant Technology
We need elements of tsunami-resistant technology to avoid the cliff-edge, considering various
load effects of tsunamis. The key issue is the elimination of cliff-edge effects. The objective is smoothfragility and/or safe relocation. We can come up with some elements of engineering protection
methods. We came up with three key areas as follows(Kameda 2011, Kameda 2012);- Water Proofing (WP: isolated from direct contact with water),- Structural Resistance (SR: withstand hydrodynamic tsunami forces) and- Dry Siting (DS: located at high elevation).
The proper combination of WP, SR and DS is particularly important to existing plants where thesite elevations are prefixed.

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5. Typical examples of SSC design and enhancement for tsunami protection of NPP and
implementation of waterproof, structural resistance and dry siting
5.1 Example of paths of tsunami intrusion
The Fig. 14 (1)-(2) shows how the water came in and crept into NPPs. The paths of tsunami intrusion
are as follows.
(1) Sea water pumps inundated at flooded sea water pit(2) Critical facilities submerged by flooding in the buildings intruding through carry-in entrances,ventilation louvers, etc. Then the seawater is spread in the building through hatches and openings.
EDG, electric devices, pumps, etc. are inundated.
Detailed problem identification should be made on tsunami effects on plant safety, on which basis
protection works should be enacted using WP, SR and DS technology.
5.2 Typical examples of SSC design and enhancement for tsunami protection of NPP
The table 1 shows how we can classify them into the three areas (WP, SR and DS). We may classify
them in these ways. We would like to propose this kind of framework.
We developed this kind of table of what should be the major methods to protect from tsunami. We
need a seawall and residual heat removal function following reactor shutdown. We need to protect
pumps for residual heat removal and so forth. We need a core cooling system, emergency power
supply system, emergency component cooling system, electric devices, equipment for emergency
management, building components (like doors to the buildings) and the possible paths of intrusion. As
actions, for example of seawalls, we need strong walls, a strong foundation, sea bed consolidation.
5.3 Example of implementation of waterproof, structural resistance and dry siting
Actions are already being taken at Hamaoka NPP by Chubu Electric Power as shown in Fig.15(1)-(3) because Hamaoka is extreme difficult situation. They anticipate a Tokai earthquake. They aregoing to complete it by December 2012 as shown in Fig.15.
(1) Protection from inundation of the site(2) Protection from inundation of buildings(3) Protection of core-cooling function under emergency
For example, they are making a tsunami wall with a very strong wall and foundations with a lengthof 1.6 km like Fig.15(1). The doors and the partitions to enter the building and the internal partitions
are to be strengthened and watertight (so waterproof and structural resistance) like Fig. 15(2). Twoemergency gas turbine generators are to be installed at an altitude of 25 m like Fig. 15(3), so it’s dry
siting. This kind of framework should be established.

hatchventilation louver
carry-in entrance
emergency diesel generator
electric devices

Reactor Building
pumps for cooling systems in
isolated reactor condition, etc.

(2) Critical facilities submerged by flooding in the buildings(1) Sea water pumps inundated at flooded sea water pit

Fig. 14 (1)-(2) Water came in and crept into NPPs

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Table 1 SSC design and enhancement for tsunami protection of NPP
Structures, Systems, Components (SSC)

Location

Actions (e.g.)*Seawall*outdoor*facing theopen sea*strong walls*strong foundation*sea bed consolidation

WP*Pumps for the residual heatremoval system , etc.

*buildingbasement*watertight chamber○*Core cooling system*High pressure-low pressure
core pumps, etc.

*bldg. basement*watertight chamber○*bldg. basement& vicinity*watertight chamber, or*relocate in high elevation○*Emergency diesel generator

DS○*Residual heat removal
function following reactor
shut down (scram)*Emergency power supply
systemSR○○*Fuel oil tanks*outdoor*strong foundation*Emergency component
cooling system*Sea water pumps, etc.

*outdoor &seawater level* Electric devices*power cable & signal cable*monitoring instruments*electrical panels, etc.

*outdoor*indoor*watertight protection for
driving motors, etc.
*water-sealed cable*strong cable supports*watertight chambers*upper floor of bldg

*Equipments for
emergency management*Portable emergency power
supply systems*Portable pumps*(optional)*install at high elevation○*(optional)○*Carry-in entrance to bldg.
*Ventilation louvers, etc.

*Outer wall of
bldg.

*Hatches and openings
within buildings* Openings at intake tunnels* Trenches, etc.

*Inside bldg.

*install at high elevation*watertight & strong
doors to resist tsunami
loads*waterproof hatches &doors* Outdoor &underground* Watertight lids, etc.

*Building components* Possible paths of intrusion(seepage, siphon effects, etc.)(2) Watertight doors at entrace to RB and waterproof
internal partitions (WaterProof & Structural Resistance)

○

○

○

○

○

○

○

○
○

(3) Emergency gas turbine generator to beinstalled at T.P,+25m (Dry Siting)

soil
rock
(1) Tsunami wall construction (T.P.+18m, 1.6km length, RC wall,
RC foundations) (Structural Resistance)
Fig. 15Action plan at Hamaoka NPP by Chubu Electric Power Co.

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6. CONCLUSINS
The summarization of this paper is as follows.
(1) Performance of NPPs in the Tohoku earthquake 11 March 2011 reviewed: some failed
catastrophically, some failed gracefully.
(2) Critical lessons for future nuclear safety were proposed:
1) Risk-based decision should be the basis of nuclear safety measures.
2) “Scientific imagination” should be a key for establishing risk models.
3) Speed in action is critical.
(3) It is seen that the fate depended on whether this kind of previous tsunami lessons had beenreflected in tsunami design or not.
(4) Agenda for tsunami PSA were proposed in terms of enhancement of tsunami fragility to eliminate
cliff-edge.
(5) "Tsunami resistant engineering" was proposed for NPP safety. The key issue is to eliminate cliffedge effects in the fragility of SSC by realizing "smooth fragility" or "safe relocation".
(6) A scheme of engineering components "Water Proof", "Structural Resistance", and "Dry Siting" wasproposed.
REFERENCES
Japanese government. (2011). “Report of Japanese government to the IAEA ministerial conference on
nuclear safety”.
Sugino, H., Iwabuchi, Y., Nishino, M., Tsutsumi, H., Sakagami, M. and Ebisawa, K. (2008).
“Development of probabilistic methodology for evaluating tsunami risk on nuclear power plants”,
The 14th World Conf. on Earthquake Engineering, Oct. 12-17, Beijing, China.
Ebisawa, K., Kameda, H. and Hirano, M. (2012), “Concept of seismic-tsunami PSA under combined
ground-motion and tsunami effects on multi-unit nuclear power plants”, Proceeding of the One Yearafter 2011 Great East Japan Earthquake – International Symposium on Engineering Lessons Learned
from the Giant Earthquake-, Tokyo, 3-4 March 2012.
Kameda, H. (2011), "Earthquake engineering agenda for safety of nuclear power plants," Bulletin of Japan
Association for Earthquake Engineering, No.15, Special issue on the Great East Japan Earthquake Disaster,
October 2011, pp.97-102. (in Japanese)

Kameda, H. (2012). “Engineering agenda on earthquake-tsunami safety of nuclear power plants raisedby the 2011 Great East Japan Earthquake disaster”, Proceeding of the One Year after 2011 Great
East Japan Earthquake – International Symposium on Engineering Lessons Learned from the Giant
Earthquake-, Tokyo.

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