USNRC RIC 2009 Conference

Technical Session 2　 Regulatory Applications of International Operating Experience

Current Status of Seismic Safety Review based on Lesson learned from Kashiwazaki-Kariwa NPP on Niigata-ken Chuetsu-oki (NCO) Earthquake

Incorporated Administrative Agency

Japan Nuclear Energy Safety Organization (JNES)Katsumi EBISAWA

A. Nuclear Safety Regulation in JapanA. Nuclear Safety Regulation in Japan

　　 METI, NISANuclear and Industrial Safety Agency

Established in 2001,Staff: ～ 800　・ Safety review　・ Licensing, etc.

　　 METI, NISANuclear and Industrial Safety Agency

Established in 2001,Staff: ～ 800　・ Safety review　・ Licensing, etc.

　 NSCJNuclear Safety Commission of Japan

　 Established in 1978, Staff: ～ 100　・ Safety review　・ Regulatory guides

　 NSCJNuclear Safety Commission of Japan

　 Established in 1978, Staff: ～ 100　・ Safety review　・ Regulatory guides

　 　 JNES Japan Nuclear Energy Safety Organization

Established in 2003Staff: ～ 460 ・ Support of review, inspection ・ Safety Research, etc.

　 　 JNES Japan Nuclear Energy Safety Organization

Established in 2003Staff: ～ 460 ・ Support of review, inspection ・ Safety Research, etc.

LicenseesLicensees

Apply forpermitReport

Oversight

Report of cross check analysisInstruction of review

Safetyreview

Do Cross check analysis: Review the utility report technically as TSO of NISAEstablish Seismic Safety Division in Oct.2007, after NCO EQ

Do Cross check analysis: Review the utility report technically as TSO of NISAEstablish Seismic Safety Division in Oct.2007, after NCO EQ

11

■ NSCJ　Ⅰ． Revision of seismic design review guide

■ NISA　Ⅱ． Seismic re-evaluation　Ⅲ ． Review of NCO EQ

■ JNES　Ⅰ． Support to revision of seismic design review guide　Ⅱ． Cross-check analysis for seismic re-evaluation　Ⅲ ． Cause analysis of NCO EQ

■ Overseas organizations

　・ IAEA 、 OECD/NEA

・ NRC

2001.7

2006.9

2006.9

2007.7

2006.9

2007.7

22

B. Progress in Seismic Safety Regulation in JapanB. Progress in Seismic Safety Regulation in Japan

（～ 2000 ）（ 2001 ～ 2005 ） （ 2011 ～　　 ) 　（ 2006 ～ 2010 ）Northridge

EQ （ 1994.12 ）Kobe EQ （ 1995.1 ）

NCOEQ （ 2007.7 ）

Information exch.with NRC （ 2008. ７ )

IAEA Seismic Safety Center　　　　　 （ 2008.10)

IAEA-JNES Tsunami EBP　　　　 （ 2007 ～ 2009)

Northridge EQ Kobe EQ NCO EQ NRC meet.

ⅠⅠ．． Activities after Revision of Seismic design GuideActivities after Revision of Seismic design Guide

■NSCJ　　・ Main features of revised seismic design review guide

Items Previous guide New guide

(1) Design basis ground motion

・ 2 kinds of ground motion

・ S1 ： Within elastic region

・ S2 ： Confirmation of function

・ No possibility beyond S2

・ One design ground motion

　・ Ss ： Confirmation of function

・ Possibility beyond Ss

(2) Seismic design ・ Allowable stress based ・ Performance based

(3) Risk ・ Recognize residual risk*

* risk due to beyond Ss

■NISA　　・ Required the licensees to re-evaluate seismic safety of existing NPPs according to the new seismic design review guide （ 2006.9 ）　　⇒　 Re-evaluation: 1st step- deterministic approach, 2st step- Residual risk

■Atomic Energy Society of Japan (AESJ)　　・ Established Seismic PSA Implementation Standard based on consideration of residual risk in the new seismic design review guide （ 2007.9 ）

33

Tokai #2

Tomari

Fukushima #1, #2

Onagawa

Hamaoka

TakahamaIkata

KashiwazakiKariwa

Genkai

Sendai

Rokkasho

Higashidoori

Monjyu

Ooi

Shimane

Mihama

Tsuruga Shika

Tokai #2

Tomari

Fukushima #1, #2

Onagawa

Hamaoka

TakahamaIkata

KashiwazakiKariwa

Genkai

Sendai

Rokkasho

Higashidoori

Monjyu

Ooi

Shimane

Mihama

Tsuruga Shika

2006 2007 2008 2009 2010 ～

PWR （ 23 units ）

BWR （ 32 units ）

Reprocessing/FBR Monju（ 6 facilities ）

　　 NISA

　　 JNES

ⅡⅡ．． Status of Seismic Re-evaluationStatus of Seismic Re-evaluation

Interim report

Final report

Review of interim report

NCO EQ （ 2007.7 ）

Review of final report

Uti

lity

■Review by NISA　・ Organize Subcommittee related to seismic safety re-evaluation

■NISA’s direction to reflect recent findings and lessons learned from NCO earthquake (2007.7) ・ To TEPCO: to investigate causes and to confirm plant integrity （ 2007.7 ） ・ To JNES: to carry out cause analysis and cross-check to TEPCO’s result　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 （ 2007.10 ） ・ To licensees: to reflect cause analysis result by JNES to seismic safety re-evaluation （ 2008.9 ）

44

ⅢⅢ ．． Process to deal with NCO EQ by NISA 1/2Process to deal with NCO EQ by NISA 1/2

2. Integrity evaluation to NCO EQ1. Cause analysis of earthquake

Earthquake andground motioncharacteristics

3. Re-evaluation(Criteria ⅣAs)

・ Reinforcement （ voluntary ）・ Building and facility integrity

Buildingresponse

characteristics

Standard ground motion Ss

Evaluate elastic limit （ urgently ）（ Criteria AsⅢ ）

Inspection

・ Building / facilityintegrity

Additional inspection

Analysis

Observed G.M.

・ Building / facilityIntegrity

Facility withsmall margin

55

Process to deal with NCO EQ by NISA 2/2Process to deal with NCO EQ by NISA 2/2

2. Integrity evaluation to NCO EQ 1.Cause analysis of earthquake

Earthquake andground motioncharacteristics

3.Re-evaluation(Criteria ⅣAs)

・ Reinforcement （ voluntary ）・ Building and facility integrity

Buildingresponse

characteristics

Standard ground motion Ss

Evaluate elastic limit （ urgently ）（ Criteria AsⅢ ）

JNES cross-check analysis⇒Causes 　 resolved and approved by Subcommittee

・ Source charac- teristics・ Deep under- ground structure

・ Floor flexibility・ Building-soil interaction

JNES cross-check analysis of Units 6&7⇒Evaluation result approved

by Subcommittee

JNES cross-check analysis of Unit 7 ⇒Evaluation result approved by Subcommittee

Inspection

・ Building / facilityintegrity

Additional inspection

Analysis

Observed G.M.

・ Building / facilityIntegrity

Facility withsmall margin

66

Kashiwazaki Site

Epicenter

■ Location of Units K1-7

Main shock:　 ・ July 16, 2007　 ・ Mj : 6.8　 ・ Depth : 10 km　 ・ Epicenter Distance: 14 km

1.Cause Investigation on NCO EQ

K5 K6 K7Service Hall

Soil Dump

K4 K3 K2 K1

Japan Sea

North

South

About 2.5 km

■ Characteristics of Earthquake

8

■ Earthquake Motion observation at Reactor Building

Vertical Array observation

Seismometer on the Building Foundation

Ground Surface

77

3rd floor2nd floor

1st floor

1stbaseme

nt

5thbasement

9

1000

500

0

-5000 5 10 15

680Gal 606GalKK1

442Gal＊

KK2 KK3 KK4 KK5KK6KK7485Gal384Gal 366Gal 322Gal 318Gal

0 5 10 15 0 5 10 15 0 5 10 15 0 5 10　 15 0 5 10 15 0 5 10 15(s)

加速

度(Gal

）

5.0

加速

度（Gal）

周期（秒）2.01.00.50.20.10.050.02

0

500

1000

1500

2000

5.0

加速度（Gal）

周期（秒）2.01.00.50.20.10.050.02

0

500

1000

1500

2000

Response Spectra of Unit 1 and 5

Observed

Design

Unit 1Unit 2 Unit 3 Unit 4 Unit 7 Unit 6

Unit 5

(1)Features of Observed Waves and Response Spectra on Reactor Building

Generation of 3 Pulse Waves

5.0

加速

度（Gal）

周期（秒）2.01.00.50.20.10.050.02

0

500

1000

1500

2000

Unit 1 Unit 5

273 Gal

680 Gal

Period (s) Period (s)

Period (s)

ⅠⅠ．． Amplification Characteristics of the Sources and the Seismic Ground MotionsAmplification Characteristics of the Sources and the Seismic Ground Motions (1) Why did 3 pulses happen ? 　 (2) Why did the observed seismic ground motions exceed those designed and the Unit 1 shows the highest values which are nearly double of the design response ? (3) Why did the acceleration values of observed seismic motions of the Unit 1 become nearly double of the Unit 5 ?(Those two Units locate in 2.5 km apart each other in the site).ⅡⅡ．． Response Spectral Characteristics of BuildingsResponse Spectral Characteristics of Buildings (1)Why were the response spectra derived from the observed seismic motions different from those of the vibration model of the conventional seismic design ?

ⅠⅠ．． Amplification Characteristics of the Sources and the Seismic Ground MotionsAmplification Characteristics of the Sources and the Seismic Ground Motions (1) Why did 3 pulses happen ? 　 (2) Why did the observed seismic ground motions exceed those designed and the Unit 1 shows the highest values which are nearly double of the design response ? (3) Why did the acceleration values of observed seismic motions of the Unit 1 become nearly double of the Unit 5 ?(Those two Units locate in 2.5 km apart each other in the site).ⅡⅡ．． Response Spectral Characteristics of BuildingsResponse Spectral Characteristics of Buildings (1)Why were the response spectra derived from the observed seismic motions different from those of the vibration model of the conventional seismic design ?

Contents of Cause Investigation

88

Observed Observed

DesignDesign

Response Spectraof Unit 4 Building

Asperity 1(Rupture starting ： 0

sec)

Asperity 3(Rupture starting ：

7.8 sec)

NPP

Asperity 2(Rupture starting ： 3

sec)

Observed wave formNPP

Vs=3.0km/s

Vs=2.4km/s

Vs=2.0km/s

Vs=1.7km/s Vs=1.68km/sVs=0.98km/s

Vs=0.84km/s

1.80　sec放射特性

発電所敷地方向に

強い波動の放射

P波、Sｖ波の波動伝播（２次元差分法解析結果）

Analysis of the effects of source characteristics

(2) Analysis of Effects of Sources and Seismic Ground Motionsof Sources and Seismic Ground Motions

ASP1（DIP=30° ）NS成分：0.34，EW成分：－0.43走向：37° ，傾斜：40° ，すべり角：90°射出角：123.51° ，方位角：184°

ASP3（DIP=30° ）NS成分：0.48，EW成分：－0.66走向：37° ，傾斜：30° ，すべり角：90°射出角：145.25° ，方位角：88°

Dip=30°

Dip=40°

ASP1（DIP=30° ）NS成分：0.34，EW成分：－0.43走向：37° ，傾斜：40° ，すべり角：90°射出角：123.51° ，方位角：184°

ASP3（DIP=30° ）NS成分：0.48，EW成分：－0.66走向：37° ，傾斜：30° ，すべり角：90°射出角：145.25° ，方位角：88°

Dip=30°

Dip=40°

Plane section Cross section

Asperity 3 (EW):Strong radiation

★ ： Rupture starting point

(i) Sequential rupture of 3 asperities which broke out strong seismic motion is one of causes of amplifying pulse wave.(ii) Asperity 3 is very close to the site, and radiates strong seismic motion.

(i) Sequential rupture of 3 asperities which broke out strong seismic motion is one of causes of amplifying pulse wave.(ii) Asperity 3 is very close to the site, and radiates strong seismic motion.

99

（ Vs ：km/s ）

Generation of 3-D Underground Structure Model

(3) Analysis of Effects of Deep Ground Structure

Used data 　 : Boring surveys, reflection surveys, geological maps, etc., performed by the former Japan National Oil Corporation.

Used data 　 : Boring surveys, reflection surveys, geological maps, etc., performed by the former Japan National Oil Corporation.

KKNP

基盤岩

ｸﾞﾘｰﾝﾀﾌ・七谷下部寺泊

椎谷（Vs=0.8～1.7）

海域上部寺泊

（Vs=3.15）

（Vs=2.6）

（Vs=2.2）

（Vs=1.9）

西山（Vs=0.7～1.1）WE

Source Area

Kanto Side ← → Japan-Sea Side

The Site

Free Base Stratum

Depth = 150 – 250 m

Seismic Base Stratum

Depth = 5000 – 8000 m

Ground SurfaceNishiyama

ShiiyaUpper

Teradomari

LowerTeradomari

Green Tuff / Nanatani

Bedrock

E

WAnticline

The Site

Perspective View Direction

NEpicenter

Japan-Sea Side ←

→ Kanto Side

(i) Earthquake bedrock near the site is deep as about 5~8 km.(ii) The deep underground structure has irregularity in propagation path of

seismic motion from epicenter.

(i) Earthquake bedrock near the site is deep as about 5~8 km.(ii) The deep underground structure has irregularity in propagation path of

seismic motion from epicenter. 1010

-1西山-2西山

上部寺泊下部寺泊七谷＋ｸﾞﾘｰﾝﾀﾌ基盤

-1西山-2西山

上部寺泊下部寺泊七谷＋ｸﾞﾘｰﾝﾀﾌ基盤

椎谷（Vs=0.98km/s）

西山（Vs=0.7km/s）

上部寺泊（Vs=1.87km/s）

地震基盤（Vs=3.2km/s）

下部寺泊（Vs=2.2km/s）

0

0.50

1.50

2.15

7.20

深度（km）

七谷層+（ Vs=2.6km/s）4.30

0

100速度(cm/s)

地震基盤

敷地解放基盤

敷地に直達する

地震動の伝播経路

ASP3

●パルス波の成長過程

Analysis of Amplification Characteristics of Pulse Waves at Unit 1

Free bedrock

Seismic bedrock

■Propagation of pulse wave

ASP 3

■Amplifying process of pulse wave

Velocity wave (cm/s)

0

-8000

-7000

-6000

-5000

-4000

-3000

-2000

-1000

0

0 20 40 60 80　 (cm/ s)最大速度

　(m)

深度

　 0　　　　

-2

-4

-6

-8 　　　　 0 　　　　 40 　　　　 80

-8000

-7000

-6000

-5000

-4000

-3000

-2000

-1000

0

0 1 2 3 4　 (km/ s)せん断波速度

0 　　　　 2 　　　　 4Shear vel. (km/s)Max. vel. (cm/s)

■ Max. velocity (EW) and Shear Vel. (Vs)

　

Seismic bedrock

Bedrock

Shitiya layer

KabuTeradomari layer

Jyoubu Teradomari layer

Shiiya layer

Nishiyama layer Vs reduction

Shiiya layer

NNP Free bedrock

Dep

th (

km)

Nishiyama layer

(i) Irregularity in deep underground structure concentrate and storage seismic ground motion energy, and tend to lead seismic motion to the site.(ii) Pulse wave at the layer near free bedrock are amplified largely. (iii) Amplifying factor is 3 ~ 4 times.

(i) Irregularity in deep underground structure concentrate and storage seismic ground motion energy, and tend to lead seismic motion to the site.(ii) Pulse wave at the layer near free bedrock are amplified largely. (iii) Amplifying factor is 3 ~ 4 times.

1111

Unit 1

①7.92 sec

②9.36 sec

③10.72 sec

④13.28 sec

⑤13.84 sec

ｱｽﾍﾟﾘﾃｨ1ｱｽﾍﾟﾘﾃｨ 2

ｱｽﾍﾟﾘﾃｨ3

ｻｲﾄW E

Snap shot of propagation of Seismic motion from source

Failure of ASP3Failure of ASP3

Arrival ofpulse waveTo the site

Seismicbedrock

Seismic bedrock

Kabu-Teradomarilayer

Shiiya layer(Reduction of Vs)

Amplificationof pulse wave at Shiiya andNishiyama layers

Propagation andAmplificationof pulse wave

Generation of

pulse wave

due to failure

of ASP 3

Propagation ofPropagation of

pulse wavepulse wave

due to failure ofdue to failure of

ASPASP １ １ and 2 and 2

ASP 1ASP 1

ASP 2ASP 2

ASP 3ASP 3

NPP

1212

Animation of Propagation of Seismic motion from Source

1313

15

● Cause of difference of Response Spectra 　⇒　 A rigid floor was assumed and analyzed, however, the real floor is flexible and a floor deformation is likely.

● Policy of the investigation into the model 　　　　 Consideration of the following items: ・ Floor deformation　 ・ Interaction between nonlinearization soil and building 　　 ・ Adjoining turbine building

● Cause of difference of Response Spectra 　⇒　 A rigid floor was assumed and analyzed, however, the real floor is flexible and a floor deformation is likely.

● Policy of the investigation into the model 　　　　 Consideration of the following items: ・ Floor deformation　 ・ Interaction between nonlinearization soil and building 　　 ・ Adjoining turbine building

440m

133m

22 ．． Integrity EvaluationIntegrity Evaluation (1) Response Spectral Characteristics of Buildings(1) Response Spectral Characteristics of Buildings

（ Input Waves ： Observed Waves on Foundation ）

Analysis Policy on the Cause on Horizontal Response Spectral (1/2)

1414

Observed: Seismometer

Lumped-mass Model (Rigid Floor)

⇒⇒ 　　 Investigation using 3-D FEM ModelInvestigation using 3-D FEM Model

HorizontalTurbine Building SectionTurbine Building Section

Ground aroundGround aroundReactor BuildingReactor Building

Building-ground Building-ground Interacting SectionInteracting Section

Concrete damping: 3%440m

SeismometerSeismometer（（ 2nd floor2nd floor ））

SeismometerSeismometer（（ FoundationFoundation ））

0

1000

2000

3000

4000

0.01 0.1 1 10　周期 （秒）

　(Gal)

加速

度応

答ス

ペク

トル

0

1000

2000

3000

4000

0.01 0.1 1 10

　周期 （秒）

　(Gal)

加速

度応

答ス

ペク

トル

h=0.05加

速度

応答

スペ

クト

ル (

Ga

l)加

速度

応答

スペ

クト

ル (

Ga

l)

ＮＳ成分とＥＷ成分の形状違いの要因はター

ビン建屋の有無

周期 ( 秒 )

Analysis Results on Horizontal Response Spectra at Unit 4 (2/2)

SeismometerFloor Plans of the Real

Plant and the FEM Model

Tu

rbin

e B

uild

ing

Tu

rbin

e B

uild

ing

The TEPCO documents were altered partially.

Outer Wall

Outer Wall Inner Wall

Inner Wall

Shell Wall

EW direction

NS Direction

FEM-meshPosition

Acc

eler

atio

n r

esp

on

se s

pec

tra

(G

al)

Acc

eler

atio

n r

esp

on

se s

pec

tra

(G

al)

Observed: Seismometer

Lumped-mass model Model (Rigid Floor)

FEM Model(Flexible floor)

EW Component

Period (s)

Period (s)

NS Component

Th

e d

iffe

ren

ce in

fo

rm b

etw

een

th

e N

S-

and

EW

-co

mp

on

ents

was

cau

sed

by

the

exis

ten

ce o

r n

on

exis

ten

ce o

f th

e T

urb

ine

Bu

ildin

g.

The results on the analysis of FEM model simulate the observed records well.The consideration of the floor flexibility is extremely essential.

The results on the analysis of FEM model simulate the observed records well.The consideration of the floor flexibility is extremely essential. 1515

C. Conclusions (1/3)

1616

Lessons learned from NCO earthquake

■Observed ground motion far exceeded the design of K-K NPP

BUT ; Safety related SCCs function maintained.

⇒Japanese seismic design codes and standards and design practice basically work well. BUT; Why ground motion and response exceeded the design? Reasons identified so far; ・ New findings through the “Ground Motion Evaluation”: ・ Effect of irregularity in deep underground structure ・ Effectiveness of source model in near site earthquake

・ Building response ・ Effect of the floor flexibility in reactor building

Lessons learned from NCO earthquake

■Observed ground motion far exceeded the design of K-K NPP

BUT ; Safety related SCCs function maintained.

⇒Japanese seismic design codes and standards and design practice basically work well. BUT; Why ground motion and response exceeded the design? Reasons identified so far; ・ New findings through the “Ground Motion Evaluation”: ・ Effect of irregularity in deep underground structure ・ Effectiveness of source model in near site earthquake

・ Building response ・ Effect of the floor flexibility in reactor building

Conclusions (2/3)

1717

Regulatory implications from NCO earthquake

■ Seismic safety regulation in Japan has to be changed due to NCO EQ?

→ No change in basic seismic regulation framework ・ Lessons learned from NCO EQ were reflected into the Seismic Re-

evaluation for all existing NPPs in Japan based on the NISA’s additional direction on Sept.2008.

・ JNES ‘s is working on currently ; “Cross-Check” of licensee’s Re-evaluation reports progressed And, Residual Risk approach will be further enhanced

Regulatory implications from NCO earthquake

■ Seismic safety regulation in Japan has to be changed due to NCO EQ?

→ No change in basic seismic regulation framework ・ Lessons learned from NCO EQ were reflected into the Seismic Re-

evaluation for all existing NPPs in Japan based on the NISA’s additional direction on Sept.2008.

・ JNES ‘s is working on currently ; “Cross-Check” of licensee’s Re-evaluation reports progressed And, Residual Risk approach will be further enhanced

Conclusions (3/3)

International Cooperation JNES is readyJNES is ready to share the lessons learned from NCO EQ with international

nuclear community e.g. through various chances like NRC (RIC and bilateral agreement), IAEA, OECD/NEA and individual countries hoping to actively contribute to further improvement of seismic safety.

■ Way for JNES to contribute to further improvement of seismic

safety. ・ IAEA ‘s revision of “seismic hazard evaluation guide” (DS422) currently underway. Lessons from NCO EQ, like source model prediction, newly incorporated

according to NISA and JNES comment

・ Contribute to the IAEA’s International Seismic Safety Center (ISSC)

■ Ｔｏｗａｒｄ the Global Nuclear Renaissance ;In line with the move of “Global Nuclear Renaissance", JNES intend to .Support for Asian countries for human resources development, etc

International Cooperation JNES is readyJNES is ready to share the lessons learned from NCO EQ with international

nuclear community e.g. through various chances like NRC (RIC and bilateral agreement), IAEA, OECD/NEA and individual countries hoping to actively contribute to further improvement of seismic safety.

■ Way for JNES to contribute to further improvement of seismic

safety. ・ IAEA ‘s revision of “seismic hazard evaluation guide” (DS422) currently underway. Lessons from NCO EQ, like source model prediction, newly incorporated

according to NISA and JNES comment

・ Contribute to the IAEA’s International Seismic Safety Center (ISSC)

■ Ｔｏｗａｒｄ the Global Nuclear Renaissance In line with the move of “Global Nuclear Renaissance", JNES intend to; Support for Asian countries for human resources development, etc. 1818