u.s. doe natural phenomena hazards meeting · –date and time of the quake - july 16, 2007 10:13...

1

U.S. DOE Natural Phenomena Hazards Meeting

Impacts of the Niigataken Chūetsu-Oki

Earthquake (NCOE) to the Kashiwazaki-Kariwa

Nuclear Power Plant, Post-Earthquake

Response, and Lessons Learned:

U.S. Perspective for Design Basis Earthquakes

and Beyond Design Basis Earthquakes

James J. Johnson, Antonio R. Godoy,

Aybars Gürpinar, Roger Kenneally

October 18-19, 2016

2

Outline of Presentation

• Niigataken Chuetsu-Oki Earthquake (NCOE) and its effect on the Kashiwazaki-Kariwa Nuclear Power Plant (KKNPP)

• KKNPP Design Basis Ground Motion and Design Procedures

• KKNPP performance when subjected to NCOE

• Post-2006 and Post-NCOE activities

• U.S. treatment and implications

3

KKNPP Subjected to NCOE

• Niigataken Chuetsu-Oki Earthquake

– Date and Time of the quake - July 16, 2007 10:13 AM

– Moment Magnitude - 6.8

– Epicenter located approximately 16 km north of KKNPP

• KKNPP – 7 units

– Four units operating (2,3,4,7) – Unit 2 in start-up – shut down successfully initiated by auto-scram

– Three units (1,5,6)– scheduled outage

4

KKNPP Subjected to NCOE: KKNPP Specific Issues and Generic Issues

• Common Cause Event

– Units 1-4 and 5-7 experienced the “same” ground motion; all SSCs experienced the “same” ground motion

– Correlation - all SSCs experienced the “same” ground motion; correlated seismic demand on SSCs in same building; potential correlated failures of like SSCs side-by-side

• Multi-Unit Considerations

– Shared systems

– In-unit support from other units unavailable

– “Identical” units failure modes “identical” – consequences multiplied

• – Cliff Edge Effects

5 5

©Google ©ZENRIN

10km

30km

Epicenter

KK NPS

Unit Horizontal-

NS

Horizontal

-EW Vertical

1 311(274) 680(273) 408(235)

2 304(167) 606(167) 282(235)

3 308(192) 384(193) 311(235)

4 310(193) 492(194) 337(235)

5 277(249) 442(254) 205(235)

6 271(263) 322(263) 488(235)

7 267(263) 356(263) 355(235)

Observed Acceleration on R/B Base Mat

Unit:Gal (cm/s2), Design value in ( )

Nagaoka

Kashiwazaki

Kariwa

KKNPP Subjected to NCOE

6

Design Basis Ground Motion for KKNPP (Pre-2006)

• DBGM defined on hypothetical or actual rock outcrop

– Rock defined as Vs > 700 m/sec

– Peak ground acceleration – horizontal – defined by empirical formulae

– Ground response spectral shape according to empirical data correlated with governing EQ

• Two earthquake ground motion levels S1 and S2 defined KKNPP dynamic design basis ground motions

– PGA

• S1 = 300 Gals

• S2 = 450 Gals

7

KKNPP Site is Complex with Irregular Soil Profile – Depth to Hypothetical Rock Outcrops

8

KKNPP Site – RB Foundation Depths and Depth to Hypothetical Rock Outcrops

9

Design Procedure for Ground Motion Excitations (JEAG-4601-1987): SSC Classes

Class As SSCs that may cause loss of coolant if damaged. SSCs that are required

for emergency shutdown of the nuclear reactor and are needed to maintain

the shutdown state of the reactor in a safe state; facility for storage of

spent fuel; and nuclear reactor containment

Class A SSCs that are needed to protect the public from the radioactive hazard in

the case of a nuclear reactor accident, and SSCs, the malfunction of which

may cause radioactive hazard to the public, but that are not classified as

Class As.

Class B SSCs that are related to the highly radioactive substance, but are not

classified as Class As or A

Class C SSCs that are related to the radioactive substance, but are not classified in

the above seismic classes, and facilities not related to radioactive safety.

10

Design Procedure for Ground Motion Excitations (JEAG-4601-1987):

Static and Dynamic Loads

• Equivalent static analysis

– Horizontal CI (called story shear coefficient) – dependent on a number of factors – for KKNPP region = 0.2

– Vertical CV – dependent on a number of factors – for KKNPP region = 0.3

– Differing multipliers of horizontal and vertical factors depending on SSC Classification

• Class As dynamic seismic forces due to S1 ground motion for design and due to S2 ground motion for evaluation

• Class A dynamic seismic forces due to S1 ground motion for design

• Classes B and C – equivalent static analysis

11

Design Procedure for Ground Motion Excitations (JEAG-4601-1987):

Envelope Class Static Analysis

Dynamic Seismic Force

S1 ground motion S2 ground motion

As

Horizontal seismic

force calculated from

3xCI

Vertical seismic force

calculated from Cv

The horizontal seismic force is

the seismic force on the

building due to the S1 ground

motion

The vertical seismic force is

calculated by taking half of the

maximum acceleration

amplitude of the S1 ground

motion as the vertical seismic

coefficient*

The horizontal seismic

force is the seismic force

on the building due to S2

ground motion

The vertical seismic force

is calculated by taking half

of the maximum horizontal

acceleration amplitude of

the S1 ground motion*

A

Horizontal seismic

force is calculated

from 3CI

Vertical seismic force

is calculated from Cv

The horizontal seismic force is

the seismic force on the

building due to S1 ground

motion

The vertical seismic force is

calculated by taking half of the

maximum horizontal

acceleration amplitude of the

basic earthquake ground motion

as the vertical seismic

coefficient

B

Horizontal seismic

force is calculated

from 1.5CI

Not taken into consideration

(investigation is conducted for

equipment and piping with the

possibility of resonance)

C Horizontal seismic

force is calculated

from CI

Notes:

CI (story shear coefficient): Value determined using 0.2 as the basic shear coefficient and with consideration of the dynamic

characteristics of the structure, type of ground, etc.

Cv (vertical seismic coefficient): Value determined using 0.3 as the basic value of the coefficient, and with consideration of the

dynamic characteristics of the structure, type of ground, etc.

*Both horizontal seismic force and vertical seismic force take place simultaneously combined in unfavorable directions. The

vertical seismic force is considered to be constant in the vertical direction.

12

KKNPP Design Procedure for Ground Motion Excitations

• Class As and A SSCs are designed to the envelope of equivalent static and dynamic loading conditions

• Next slide shows shear force as a function of design quantities (dynamic and static) for the Unit 7-RB (Class A with some portions Class As)

– Static values govern from grade to base mat

– Actual design values exceed static and dynamic loads – extra conservatism introduced by the designers

• Difficult to assess design values vs. estimated values from actual earthquake induced loads without detailed knowledge of the design and design criteria

13

Design Shear Force compared to NCOE Induced Shear Force

14

KKNPP Performance When Subjected to NCOE: Positive Consequences

• KKNPP behavior during and after the NCO earthquake

– Safe and stable – all 7 units

– LOSP did not occur – emergency power not required

– Immediate and extended inspections and tests confirmed no damage to Important-to-Safety SSCs (Class As and A)

– Considerable margin exists above the design strength of foundations, structures and equipment

– Damage and failures were to Not-Important-to-Safety SSCs and site (Class B and C)

15

KKNPP Performance When Subjected to NCOE: Reasons for Excellent Behavior

• Except for ground motion definition, KKNPP design was based on conservative assumptions, methods, and modeling;

• Stiffness and masses of many structures are smoothly distributed and stress concentrations are avoided;

• Reactor Buildings

• Deep embedment was an efficient characteristic to minimize acceleration effects;

• No excessive eccentricities and changes in stiffness;

• Equipment and piping properly anchored;

• No system interactions reported for safety related equipment – exception is buried fire protection piping failure and water flow into RB-1 – luckily, no adverse consequences

16 16

Kashiwazaki-Kariwa NPP Unit 7 Recorded Response – NCOE

17

KKNPP Subjected to NCOE:

Not Important to Safety SSC Failures

• Soil Failure

• Administration Building

• Fire Protection System

• Seismic Systems Interaction

• Seismic Instrumentation

18



• Soil Failure

– Extensive liquefaction occurred

– Site-wide soil failures limited the mobility of emergency responders and other important operational personnel, e.g., fire protection assets

– System failures, e.g., fire protection system rendered inoperable (fire extinguishing mode) experiencing failure of tanks and underground piping (five locations)

– Underground piping adjacent to U-1 RB ruptured leading to water intrusion into RB

– Differential settlement caused bus failure and ignition of the 2 hour fire in the Unit 3 in-house transformer,

19

Soil Failure Leading to Underground Fire Suppression Pipe Failure and Flooding of U-1 RB (2000 m**3)

20

KKNPP Unit 3 House Transformer Fire Ignited due to Soil Failure

21

KKNPP Subjected to NCOE: Not Important to Safety SSC Failures

• Soil Failure (continued)

– Caused damage to exhaust ducts connected to the stacks for Units 1-5 – potential consequence is radioactive releases at ground level rather than to the atmosphere at height;

– NPP station road was cut off; approach road to the site suffered a vertical relative settlement of about 0.50 m; immediate repair required

– Bank protection of the north-south discharge outlet sank;

– Slippage of soil of the east side slope of the switchyard area occurred;

– North slope of the soil disposal area collapsed.

22

Common Cause and Correlated Failure: An Example Exhaust Stack(s)

(c) KKNPP Units 1-5 typical damage to the

duct (shallow foundation) connecting to the

exhaust stack (piles). Soil settlement induced

differential displacements to these structures.

This is the pathway for the radioactive releases

to the atmosphere

23



• Administration building, containing the emergency response center, damaged causing significant delays in communication with the outside world, e.g., local fire department and other important parties;

• Selected anchorage failures, tank buckling, and other partial failures that could have led to flooding or other hazards;

• Oil leakages into the soil, which over the longer time frame could have led to significant environmental effects;

24

KKNPP Subjected to NCOE: Fire Protection Systems (Prevention, Detection, Extinguishing, Mitigation)

• Generally not classified as Seismic Category I or Safety-Related – Classification of Fire Protection Systems for all external events is an on-going issue world-wide

• Two issues are important:

(i) Systems interaction issue, i.e., if malfunction or failure occurs, does it adversely affect safety-related SSCs, e.g., underground piping failure and water ingression in U-1 RB;

(ii) Inability to fight fires when called upon to do so, e.g., the transformer fire in KKNPP Unit 3.

25

KKNPP Subjected to NCOE: Not Important to Safety SSC Failures


– Repeatable phenomena

• Falling (ceiling tiles in control room)

• Proximity impact – not observed or reported

• Spray and flooding (e.g., broken fire protection piping)

– Most often due to the effect of failure of non-SC-I items on SC-I items or housekeeping practices.

– Continued meaningful effort should be expended on the identification, evaluation, and corrective actions of seismic systems interaction issues for DBE and BDBE ground motions.

– Configuration Control Programs should be developed, proceduralized, trained on, and implemented – responsibility of engineering and operations

26

Control Room Ceiling Tiles

(a) View of the Control Room prior to the earthquake

(b) Control room ceiling panels that fell to the

floor and onto the control panels.

27

KKNPP Subjected to NCOE: Effects to be Addressed on World-wide Bases


– In cases where the NPP seismic evaluation identifies seismic systems interaction hazards, the licensee should correct such issues and ensure that the issues will not exist in the future. An effective configuration control program should be implemented and maintained. In some cases, the evaluations are considered only a “snap shot in time”. Even in these cases, an effective configuration control program should be implemented and maintained.

– For SSE and beyond design basis earthquake evaluations, a full NPP site review should be performed, that is, evaluate the consequences of failure of not-important-to-safety items to determine whether their failure will prohibit safe operation of the plant, e.g., fire protection system components that are not SC-I or SC-II.

28

KKNPP Subjected to NCOE: Seismic Data Acquisition System

• KKNPP Units 5-7 free-field records

– Numerous accelerometers were in place in the free-field on the surface of the soil and down hole.

– Substantial data was recorded in down hole arrays for aftershocks 1 and 2.

– Main shock down hole acceleration time history data was lost due to the aftershock data overwriting the records.

29

KKNPP Subjected to NCOE: Performance Assessment based on Japan Codes and Standards

• Generally, the KKNPP adhered to the Codes and Standards in effect at the time of its seismic design

• Changes in philosophy and implementation were already initiated when the NCOE occurred:

• Nuclear Safety Commission, “Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities,” Revision, September 19, 2006

• Japan Electric Association published JEAC-2008 (code) and JEAG-2008 (guidelines)

30

Post-2006 Japan Nuclear Safety Commission (19 September 2006) and Post-NCOE Activities

• Age of “active faults” for hazard consideration increased significantly in a tiered approach

(50,000 yrs changed to 120 -130,000 yrs – 400,000 yrs)

• Expanded field investigations recommended

• Empirical GMPEs and numerical fault modeling recommended

• Unspecified seismic sources near the site to be taken into account .

• Vertical ground motions to be estimated by GMPE and fault modeling

31

Post-2006 Japan Nuclear Safety Commission (19 September 2006) and Post-NCOE Activities

• Seismic categorization of SSCs was modified; Classes As and A were combined into Class S

• Updated design code JEAC-2008 and design guidance JEAG-2008 developed (in Japanese)

• Equivalent static load continues to be required in JEAC-2008 for seismic design of SSCs

• The concept of residual risk was introduced to account for beyond design basis ground motions

Currently (2016) – significant focus on BDBEE especially seismic vibratory ground motion, fault displacement, and tsunami (EE-PRA and RIDM)

32

Post-2006 (Japan Nuclear Safety Commission (19 September 2006) and Post-NCOE Activities .

• All NPP operators in Japan required to develop revised site-specific ground motions (Ss) reflecting the consensus of the scientific community

– KKNPP Units 1-4 side – Ss (PGA rock outcrop = 2300 Gals); RB basemat ZPA = 1000 Gals)

– KKNPP Units 5-7 side – Ss (PGA rock outcrop = 1200 Gals; RB basemat ZPA ~ 735 Gals)

• Detailed review of seismic capability of all units subjected to the Ss – “back check” – less conservative methodology and acceptance criteria than design

• NPP operators in Japan are required to consider the potential for fault displacement on site.

33

Post-2006 (Japan Nuclear Safety Commission (19 September 2006) and Post-NCOE Activities .

• Immediately after NCOE, Japan’s nuclear industry (regulators and licensees) assessed the seismic capability of fire protection systems

• TEPCO for KKNPP:

– Reconstructed all FP piping and founded in open channels or above ground

– Installed five water tanks for redundancy

– Implemented full time fire brigade and associated equipment

34

Fire Fighting Capability Significantly Improved after NCOE

(a) Schematic of reorganization of the KKNPP onsite fire-fighting capabilities post-NCO

earthquake

(b) Underground water tanks for firefighting system (redundancy and diversity).

(c) Fire fighting system: newly installed aboveground piping.

35


• Common Cause Events, Cliff Edge Effects, and Multi-Unit PRA Evaluations –

– U.S. leading the way in developing and implementing approaches to evaluate these issues; generally, through SPRA methods (other countries following)

– Acceptance criteria and evaluation methodologies – Risk metrics (CDF, LERF, LRF) or failure metrics (DOE criteria)

36


• Multi-unit considerations. Methodology exists for performing a seismic PRA that covers multiple units – not implemented to date; to be included in non-mandatory appendix of revised Standard ASME/ANS RA-Sb-2012; essentially almost every PRA performed in the U.S. has examined each nuclear power unit one-by-

one – progress needed.

• Cliff-edge effects. One important aspect of evaluations of BDBEEs is to assess with confidence that there is no ”cliff edge effect” when the BDBEE slightly exceeds the design basis. If there exist cliff edge effects at any credible hazard level, one needs to be assured that no adverse consequences occur to the NPP. – Seismic vibration motion is evaluated in SPRA-space – Other EEs progress needed.

37

Lessons Learned from KKNPP Subjected

to NCOE: U.S. Implications

• Soil Failure

– Definite concern at site selection and evaluation phase

– Focus is primarily on DBE (SSE) ground motions and effect on SC-I SSCs

– NUREG-0800 (SRP) Section 2.5.3 Surface Deformation, Rev. 5, July 2014

– Increased attention is being paid to BDBE and SC-II or non-Seismic Category SSCs in implementation of NTTF 2.1 evaluations

38



• Fire Protection System

– Generally addressed in SRP Section 9.5 with reference to Regulatory Guide 1.189 “Fire Protection for Nuclear Power Plants,” Rev. 2, October 2009

– RG 1.189 is in revision; current authors recommendations are to clarify and expand:

• The definition of “areas of high seismic activity”;

• The definition of “natural phenomena of less severity and greater frequency than the most severe natural phenomena (approximately once in 10 years)”.

– Expected performance of Fire Protection Systems in BDBEE should be evaluated

39




– Continued meaningful effort should be expended on the identification, evaluation, and corrective actions of seismic systems interaction issues for DBE and BDBE ground motions.

– Configuration Control Programs should be developed, proceduralized, trained on, and implemented – responsibility of engineering and operations

– SPRAs executed for NTTF 2.1 and other applications are and should address this issue

40



• Seismic Instrumentation issues have been addressed in:

– ANSI/ANS 2.2-2016, “American National Standard - Earthquake Instrumentation Criteria for Nuclear Power Plants,” Approved July 14, 2016.

– U.S. NRC Regulatory Guide 1.12, “Nuclear Power Plant Instrumentation for Earthquakes,” Rev.2, March 1997 (proposed Rev. 3, September 2016)

41


• DBE and BDBE – Vibratory Motion

– Site evaluation phase

– Periodic review for existing sites should be required as discussed previously

– Use PSHA and DSHA concepts

– Evaluate NPP for BDBE – SPRA or SMA

• DBE and BDBE – Fault Displacement

– Site evaluation phase

– Periodic review for existing sites if new information suggests fault close proximity to site

– Use PFDHA and DFDHA concepts

– Evaluate NPP for BDBE – SPRA or SMA

42

KKNPP Lessons Learned – U.S. Implications – References

• Johnson, J.J., and Gürpinar, A., “Summary of Information on Effects of the Niigataken Chūetsu-Oki (NCO) Earthquake on the Kashiwazaki-Kariwa Nuclear Power Plant,” Internal Report - NRC.[2015a]

• Johnson, J.J., Gürpinar, A., Campbell, R.D., and Kammerer, A., “Seismic Design Standards and Calculational Methods in the United States and Japan,” NUREG/CR-xxxx, in printing.[2016a]

• Johnson, J.J., Godoy, A.R., and Gürpinar, A., “Impacts of the Niigataken Chūetsu-Oki (NCO) Earthquake on the Kashiwazaki-Kariwa Nuclear Power Plant, Post-Earthquake Response, and Lessons Learned: Japan Perspective,” Internal Report – NRC.[2015c]

• Johnson, J.J., Godoy, A.R., Gürpinar, A., Kenneally, R.M., “Impacts of the Niigataken Chūetsu-Oki (NCO) Earthquake on the Kashiwazaki-Kariwa Nuclear Power Plant, Post-Earthquake Response, and Lessons Learned: U.S. Perspective,” NUREG/CR-xxxx, publication undecided 2016.[2016b]

These studies were sponsored by the Nuclear Regulatory Commission under NRC Contract Number NRC-04-0-161.

43

Thank You for Your Attention

u.s. doe natural phenomena hazards meeting · –date and time of the quake - july 16, 2007 10:13...

Documents