7 October 2010

OECD/NEA IAGE/IAEA ISSC Workshop

Kim, Min Kyu, Choi, In-Kil

Introduction

SSI researches in Korea

Overview of a Research Project about Seismic Risk Assessment of Nuclear Waster Repository

Development of Evaluation Response Spectrum ◦ Probabilistic Seismic Hazard Analysis (PSHA)

◦ Uniform Hazard Spectrum

◦ Artificial Acceleration Time History

◦ Seismic Response Analysis

Conclusion

Slide 2

Seismic risk evaluation for low-intermediate nuclear waste repository system in Korea was needed.

Especially, a SILO system should be performed a seismic risk assessment.

An evaluation response spectrum for SILO was needed.

A seismic hazard curve for bedrock should be transformed to a location of underground cavern (SILO).

Slide 3

Slide 4

` In operation

20 units (17,716 MW)

`

Under

construction

8 units (9,600 MW)

`

Under

planning

10 units (15,400 MW)

Yong-gwang

6 units

Kori 8 units

Ulchin 8 units

Wolseong 6 units

In Operation

Under Construction

Nuclear Power Plants

(Under construction)

Radioactive Waste

Disposal Facility (Under construction)

SSI is not so important for Korea because all Korean NPP sites were rock sites.

But now SSI analysis is an essential part of a structural engineering for Korean NPP ◦ There is no rock site for NPP anymore in Korea ◦ NRC regulatory guide for fixed base condition was

changed (SRP, 2007)

SSI researches were performed by some researchers ◦ Infinite elements, boundary elements, spring-dashpot

elements

SSI works performed by engineering side ◦ SASSI program was popularly used for SSI analysis.

Slide 5

Title

• Development of Seismic

Risk Assessment System for

medium and low level

nuclear waste repository

Purpose

• Seismic Risk evaluation for

nuclear waste repository

• Radiation dose evaluation of

seismic event

Pro

ba

bili

ty o

f F

ailu

re

An

nu

al E

xce

ed

Pro

b.

Seismic Motion Parameter

Fre

qu

en

cy

Seismic Motion Parameter Seismic Motion Parameter

Seismic Fragility Curve Seismic Hazard Curve

Seismic Risk Evaluation

Slide 6

Slide 7

ITEMS Target Facilities

Tunnel Vertical Tunnel

Operational Tunnel Construction Tunnel

Cavern SILO

Ground Ground Storage Facilities

Vertical Tunnel Operational Tunnel

Construction Tunnel SILO

Slide 8

Driving systemDriving system Driving systemDriving system

Literature review

Selection of SSC

Evaluation of

numerical model

Hazard curve

Transform of

hazard curve

Fault/event tree

Atmosphere/

Geology data

Dose conversion

factor

Leakage rate for

accident scenario

Seismic analysis

Failure

mode/criteria

Fragility analysis

for each SSC

Accident scenario

analysis

Seismic risk

assessment method

Source term

evaluation

1st

year

2nd

year

3rd

year

Fragility analysis Fragility analysis Risk analysis Risk analysis Radiation dose Radiation dose

Pre/post

processing

Risk assessment

solver

Radiation rate

determine

Computer Code Computer Code

Development of

FT/ET editor

Site specific spectrum for seismic risk assessment is needed

Uniform hazard spectrum (UHS) is generally used

Kori site specific spectrum was used in Korea for seismic risk assessment

0.01 0.1 1 10 100

Frequency(Hz)

0

0.2

0.4

0.6

0.8

Sp

ectr

al A

cce

lera

tio

n(g

)

Kori Site Specific

Uniform Hazard

Reg. Guide 1.60

Fundamental Frequency Shift

Response Decrease

Slide 9

HCLPF Natural freq.

Transformer A 0.516 0.304 0.254 13Hz 0.492 0.415 1.187 0.613 0.302

Transformer B 0.442 0.310 0.214 15Hz 0.463 0.429 1.080 0.477 0.232

Transformer C 0.692 0.310 0.336 20Hz 0.390 0.464 0.840 0.582 0.282

Bushing A 0.619 0.304 0.305 9.3Hz 0.5 0.374 1.334 0.826 0.407

Bushing B 0.489 0.311 0.236 5Hz 0.5 0.257 1.945 0.950 0.459

Bushing C 0.597 0.303 0.295 6.1Hz 0.5 0.287 1.740 1.040 0.513

mA SSSSA UHSSA UHSF UHSAM UHSHCLPF

TR A TR B TR C BU A BU B BU C

Slide 10

Seismic Hazard Curves

Uniform Hazard Spectrum Attenuation equation

Seismic Source

Artificial Acceleration Time History

Site Response Analysis

Ground Layout

Dynamic Characteristic Propose Evaluation Response Spectrum

Input Parameters

• Thickness • Shear wave velocity • Unit weight

• Shear Modulus (G) • Damping ratio

Spectrum Analysis

Slide 11

Parameter Value

a-value 5.5±0.5

b-value 0.8±0.1

6.7±0.5

Focal depth 10±5

MAXM

Slide 12

2127.0277.0715.2 LLW MMM

Midcontinent of Toro et al. (1997)

1 10 100 1000

Epicentral Distance (km)

10-5

10-4

10-3

10-2

10-1

100

Pea

k G

round A

ccele

ration (

g)

ML=6.0

Toro et al. (1997)0.5 Hz

1.0 Hz

2.5 Hz

5.0 Hz

10.0 Hz

25.0 Hz

35.0 Hz

PGA

Slide 13

RCR

CCRCMCMCCY WW 60,100

lnmax)45(ln4)6(3621ln 2

22 7CRR epi

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Peak Ground Acceleration (g)

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

Annual E

xceedance P

robabili

ty

Mean

15 Percentile

Median

85 Percentile

Slide 14

0.1 1 10 100

Frequency (Hz)

101

102

103

Spectr

al A

cce

lera

tion (

gal)

Toro et al.(1997)1.0E-04

Frequency (Hz) Acceleration (g)

1 0.04318

2.5 0.09301

5 0.22785

10 0.29921

25 0.39322

35 0.39267

50 0.18334

Slide 15

Generation of 30 artificial acceleration time histories which satisfy the uniform hazard spectrum using P-CARES

Slide 16

Response Spectrum of 30 artificial

acceleration time histories

Compare of mean response spectrum

and UHS

Slide 17

Korean Standard (1997): seismic hazard based on Rock condition ◦ Shear wave velocity of the rock: 760m/s~1500m/s

FEMA 368: Maximum Considered Earthquake (MCE) ◦ Shear wave velocity of the rock: 760m/s

Japan: engineering bedrock and seismic bedrock ◦ engineering bedrock: 400-700m/s ◦ seismic bedrock: 3000m/s

Standard Review Plan of NRC (2007) ◦ Fixed base assumption: 3500ft/s ⇨ 8000ft/s (1067m/s ⇨ 2438m/s)

Slide 18

Soil

layer

Soft

rock Rock

Hard rock

0.5

(EL. M)

-80

(EL. m)

-130

(EL. m)

Density

(g/cm3) 1.65 1.90 2.70 2.90 2.90 2.90

Vs(m/s) 628.0 745 1500 2897 2580 3074

Layer

thickness

(m)

4.3 5.2 23.5 80.5 50.0 70.0

Poisson's

ratio 0.33 0.3 0.27 0.20 0.23 0.12

Slide 19

Pro-SHAKE

Frequency domain analysis

Equivalent linear method for considering a nonlinear soil properties of ground ◦ Shear wave velocity and damping ratio

20

Slide 21

Frequency (Hz)

Surface Input motion Underground

100 0.334 0.184 0.097

50 0.328 0.182 0.099

25 0.844 0.408 0.187

16.67 0.877 0.365 0.231

10 0.439 0.315 0.195

8.33 0.367 0.296 0.184

5 0.258 0.237 0.130

1 0.047 0.047 0.045

0.5 0.025 0.025 0.025

Slide 22

Uniform hazard spectrum for target nuclear waste repository system was developed by using seismic hazard curve

30 artificial seismic acceleration time histories were developed for seismic response analysis

Finally evaluation response spectrum for seismic risk assessment for low and intermediate nuclear waste repository system in Korea

Slide 23

감사합니다