special seismic problems

SPECIAL SEISMIC PROBLEMS OF HIGH

ENERGY PIPING

L. PEČÍNKA

IAGE Workshop, 2011

30.11.2011 1

DEFINITION AND TASK

High energy fluid systems: Fluid systems that, during normal

plant conditions are either in operation or maintained pressurized

under conditions

either or both of the following are met

maximum operation temperature exceeds 100°C (200°F) or

maximum operating pressure exceeds 2MPa (275 psig.)

Tasks

development of ASME Code Section III

break postulation: history and rules

ageing management: Dynamic Behavious of Piping Systems with

Local Degradation

redefinition of L LOCA: influence of SSE

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DEVELOPMENT OF ASME CODE Section III :

HISTORICAL MILESTONES

1915 : STANDARD SPECIFICATION FOR POWER PIPING

1935 : AMERICAN TENTATIVE STANDARD FOR PRESSURE PIPING

1942 : ASA B 31.1 AMERICAN STANDARD CODE FOR PRESSURE PIPING

1953 : REVISION OF THE 1942 CODE ASA B 31.1a – 1953

TYPICAL FEATURE: ALLOWABLE STRESSES IDENTICAL

WITH BOILER CODE

1955 : REVISION OF THE 1953 CODE: B31.1 – 1955

PRESSURE DESIGN

Minimum thiskness of pipe wall

Allowable working pressure of pipe

Only in words: sustained external loadings

Formulated eq. (10) for thermal expansions including „i“

milestone!

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hS

DEVELOPMENT OF ASME CODE SECTION III :

HISTORICAL MILESTONES cont. 1

1963 issued Section III „Nuclear Pressure Vessels“

Design-by-analysis approach published

B 31.1 – 1953 not included

1969 issued USAS B31.7 „Nuclear Power Plant Piping Class 1, 2

and 3“

Simplified Design-by-analysis approach used for Class 1

Class 2/3 nearly identical with B 31.7

1971 issued ASME Code Section III. B 31.7 included

Article NB 3600 Piping Design for Class 1

Article NB 3600 Piping Design for Class 2/3

Seismic event not included for Class 2

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mBBaaab STTECTE 312

131

10

iMI

DoC

t

PDoC

2221



1972 issued Winter Addenda of Section III.

Seismic event included

For Class 2/3 Piping following equations formulaten

For sustained loads

For occasional loads

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8

hba

n

SW

MMi

t

PDo2.175.0

25.0

9

hba

n

SW

MMi

t

PDo

75.02

5.0



Introduced eq (11) as a sum of eqs (8) and (10) in form

Introduced „Servis Limits“

normal, upset, emergency, faulted

1974 : Service Limits in 1972 Winter Addenda changed to Service

Limits A, B, C, D

1981 : introduced PRIMARY STRESS INDICES B1 and B2

INCREASED ALLOWABLE STRESSES FOR SERVICE LIMITS A and B

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Ahca

n

SSW

Mi

W

Mi

t

PD

75.075.02

5.0 0

AhA SSfS 25.025.1

hA

n

SW

MB

t

DPB 5.1

22

max1

8



Eq. (9) : allowable stresses for Level C and D increased to

Level C:

Level D:

effect of non repeated single anchor movement

for Class 1 Eq. (10) has been changed to

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yhBA

n

SorSW

MMB

t

DPB 5.18.1

22

max1

Ac S

W

Mi

yh SorS 8.125.2

yh SorS 0.205.3

CD S

W

Mi 3

mBBaaabi STTECM

I

DC

t

DPC 3

22321

9

10



GENERAL COMMENTS

In revision of ASME CODE Section III. Articles NB 3600 and NC 3600

after 1981 the allowable stresses have been increased

At present US NCR accepted only Revision 1992

It is evident that develpment of Class 2 Code was ahead of Class 1

After 1981 NB 3600 and NC 3600 both Articles are partly unified –

introduction of B1 and B2 indices in Eq. (8) and (9) of NC 3653

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BREAK POSTULATION: HISTORY AND RULES

HISTORICAL DATA

1959 : US NPP SHIPPINGPORT DESIGN: MAXIMUM CREDIBLE

ACCIDENT

1975 : US NRC STANDARD REVIEW PLAN 3.6.2 MEB 3-1: PIPE

BREAK OUTSIDE CONTAINMENT

RG 1.46 for piping inside containment

Definition of high energy piping

1981 : EXTENSION OF MEB 3-1 TO INSIDE AND OUTSIDE PIPINGS

1987 : MEB 3-1 WENT THROUGH SOME SUBSTANTIAL CHANGES

1986 : SRP 3.6.3 LBB

2005: APPARITION PRBABILISTIC LBB

REDEFINITION OF L LOCA

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BREAK POSTULATION: HISTORY AND RULES

HISTORICAL DATA cont. 1

1975 : SRP 3.6.2, MEB 3-1

FOR ASME CODE Section III. Class 1 Piping

in containment penetration area: breaks need not be postulated if

-

- The cumulative usage factor (CUF) should be less than 0.1

in aress other than containment penetration: breaks should be

postulated

- At therminal ends

- At intermediate locations where

- At intermediate locations where CUF exced 0.1

30.11.2011 10

m

m

bbaaab

i

S

STTEC

W

MC

t

DPC

3

4.28.02

231

10

m

m

bbaaabi

S

STTEC

W

MC

t

DPC

3

4.28.0

2321

BREAK POSTULATION: HISTORY AND RULES cont. 2

If two intermediate location cannot be determinated, two highest

stress location should be selected. If the piping run has only one

change or no change of direction, only one intermediate location

should be postulated

FOR ASME Code Section III., Class 2 Piping

in contaiment penetration area: breaks need not be postulated if

in areas other than containment penetration: breaks should be

postulated

At terminal ends

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Ah

iBAi SS

W

Mi

W

MM

t

DP

2.18.075.0

25.0


At two locations with at least 10% diference in stress, or if stresses

differ by less than 10%, two location separated by a change of

direction of the pipe run

At each location where breaks shall be postulated, pipe whip

restrainst shall be postulated and calculated

1986: US NRC issued Generic Letter 87-11: Relaxation in Arbitrary

Intermediate Pipe Rupture Requirements

Arbitrary intermediate pipe reptures as specified in 1975 SRP edition

for Class 1 and Class 2/3 piping are now no longer mentioned or

defined in MEB 3-1

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Ah

cBAi SS

W

Mi

W

MM

t

DP

2.18.075.0

25.0

109


For Class 2 piping Eqs. (8) and (9) of ASME Code Section III

Article NC 3600 the stress indices B1 and B2 where introduced

and stress limits to 1.5. (Eq.(8)) and 1.8 (Eq.(9))

PIPE WHIP RESTRAINTS

Design features are based on

Displacement and bending or

Displacement and rotation

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Typical transverse restaint based on displacement: coper bumpers and celluar concretering

hShS


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Stainless steel rods: fixed

U shape rods aroung sleeve

Stainless steel rods: fixed

U shape rods without sleeve


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Stainless steel rods:

„pipe following“ U shaped rods

Stainless steel rods:

„pipe following“ U shaped rods


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Attachment of stainless steel bar

to steel frame


for hinge mechanism



to concrete embedment

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An Experimental Study on Dynamic Behavior of

Piping Systems with Local Degradation

National Research Institute for Earth Science and Disaster Prevention

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Purpose

Degradation of piping systems caused by Aging Effects

(Wall thinning / Cracks)

How does the piping systems

with local degradation

behave under the destructive earthquake?

An experimental research program is being conducted.

(1996 – 2000)

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Pipe Element Tests

Cyclic 4-point bending tests using straight pipes with degradation

Purpose : To clarify the failure mode of degraded pipes under

the high level bending loading

Piping System Tests

Shaking table tests using piping systém models with degradation

Purpose : To clarify the effect of degradation on piping

system´s dynamic behavior and failure mode

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Pipe Element Tests

Specimens with Wall Thinning

Degradation : Full circumferential thinned wall (Made by machining)

Material : Carbn Steel STS410

Internal Pressure : 11MPa / 0MPa

The Figure of the Thinned Wall Specimens

t = 4.3mm for 50% wall thinning, 2.15mm for 75% wall thinning

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Failure mode of thinned wall pipes

#01 Low cycle fatigue with

ratcher deformation

Pressurized specimens with

50% of wall thinning

Hoop stress by internal pressure

at thinned wall part :

Circumferential cracks were

caused by cyclic bending load.

y45.0

Before the bending test

Swelling by ratchet Crack

After the bending test

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#02 Buckling and Low – cycle fatigue

The 50% of thinned wall specimen

without internal pressure and water

Local buckling occurred at the thinned

wall part during cyclic loading.

Cracks caused at the bottom of

buckling deformation.

A full circumferential break was caused

by the following a few cycles.

(View from loading direction)

(View from the upper side)

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#03 Combined mode with ratchet,

low – cycle fatigue and burst

Pressurized specimens with

75% of wall thinning

Hoop stress by internal pressure

at thinned wall part:

The wall thickness decreased from 2.15 mm

to 1.1 – 1.6 mm because of ratcheting.

Cracks penetrated in the circumferential direction,

and in the axial direction as well.

y9.0Circumferential cracks

Axial cracks

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3D_A01

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Piping System Tests

Material: Carbon Steel STPT370

Defect type: No degradation Internal Pressure: 10 MPa

Material: Carbon Steel FSGP Elbow & Carbon Steel STPT370

Defect type: Wall thinning at Elbow Internal Pressure: 10 MPa

Material: Stainless Steel SUS304 & Carbon Steel STP370

Defect type: Partial EDM notch Internal Pressure: 8 MPa

3D_C01

3D_D01

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3-D Piping model for piping system tests

Wall thickness of Elbow1 and Elbow2 were thinned for 3D_C01

A narrow band random wave was used for the excitation tests

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Test Results of 3-D Piping System Tests

3D_A01: 2.78Hz 3D_C01: 2.42Hz 3D_D01: 2.79Hz

(Without defects) (Wall thinning at Elbow) (Partial EDM notch

at straight pipe)

Relation between Input Acceleration

and Response Acceleration at Elbow 3

Relation between Input Acceleration

and Range of Elbow Deformation Angle

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Test Results of 3-D Piping System Tests

Failure mode

3D_A01: 20 times excitation

in elastic – plastic level

3D_C01: 6 times excitation

in elastic – plastic level

Fatigue cracks in the longitudinal direction at

the side surgace of Elbow1

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Conclusion

The failure mode of thinned wall pipe changes according to the

condition of wall thinning and internal pressure.

Wall thinning at elbows in a piping system affects its natural

frequency, reduces the strength, and increases the deformation

of the piping system. A small crack has little or no influence

on the piping system´s vibration characteristic.

The failure mode of 3-D piping models with and without

wall thinning was low-cycle fatigue failure at an elbow.

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30.11.2011 30

REDEFINITION OF LARGE LOCA

US NRC NUREG – 1829, Vol. 1

„Estimating Loss-of-Coolant Accident (LOCA) Frequencies

Through the Elicitation Process“

What is „elicitation“ process?

Results of the elicitation process

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BACKGROUND

SOLUTION OF MANY MECHANICAL PROBLEMS (DESIGN,

INTEGRITY) IS COMPLICATED

ADVANTAGES OF ELICITATION APPROACH

ESTABLISHED PROCESS USED US NRC (NUREG/CR-5424, US NRC,

1990)

NO DEVELOP WORK NEEDED

USABLE QUICKLY

USED BEFORE FOR COMPLEX PROBLEMS WITH LITTLE DATA

ABLE TO CONSOLIDATE AND QUANTIFY VARIOUS DATA STREAMS

SERVICE HISTORY

PFM INSIGHTS

EXPERT KNOWLEDGE ON PROBLEMS OF INTEREST

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30.11.2011 32

PANEL SELECTION

POTENTIAL PANEL MEMBERS MAY BE SEEKED WITHIN

INDUSTRY

ACADEMIA

NATIONAL LABORATORIES

CONTRACTING AGENCIES

INTERNATIONAL AGENCIES

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FLOWCHART OF THE OVERALL ELICITAION

PROCESS

FLOWCHART OF THE OVERALL ELICITAION

PROCESS

30.11.2011 33

30.11.2011 34

ELICITATION TRAINING

CONSTRUCTING THE PANEL WITH EXPERTS FROM ALL RELEVANT TECHNICAL AREAS AND INSTITUTIONAL/ORGANISATIONAL AFFILIATIONS

CONDUCTING ELICITATION TRAINING TO IDENTIFY POSSIBLE SOURCES OF BIAS AND CONDUCT AN EXERCISE INVOLVING „ALMANAC-TYPE“ QUESTIONS WITH KNOWN ANSWERS

PROVIDING OPERATING EXPERIENCE DATA AND BASE CASE SCENARIOS FOR ANCHORING AND VALIDATING RESPONSES TO THE PANEL

FORMULATING THE ELICITATION QUESTIONS TO AVOID RESPONSE BIAS

CONDUCTING INDIVIDUAL ELICITATION QUESTIONS TO ELIMINATE THE POSSIBILITY OF GROUP DYNAMICS INFLUENCING PANELLIST RESPONSES

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ELICITATION TRAINING – cont. 1

THE ELICITATION PROCESS HAS THREE SPECIFIC PURPOSES

TO DISCUSS SOURCES OF BIAS IN THE ELICITATION

PROCEDURE

TO FAMILIARISE THE PANELLIST WITH THE TYPE OF

RESPONSES WHICH THEY WILL BE ASKED TO MAKE

TO PROVIDE THE PANELLISTS WITH PRACTICE IN MAKING

ELICITATION RESPONSES USING TRAINING EXERCISE

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MOTIVATION BIASES

SOCIAL PRESSURE (LOBBING)

MISINTERPRETATION IF THE ELICITATION QUESTION STRUCTURE

IS INCONSISTENT WITH A PANELLIST’S THOUGHT PROCESS

MISINTERPRETATION DUE TO INCORRECT ASSUMPTIONS ABOUT

THE DATA OR THE MODELS USED TO ANALYZE THE ISSUE

WITHFUL THINKING AS THE RESULT OF INSTITUTIONAL BIAS

30.11.2011 36


COGNITIVE BIASES

INCONSISTENCY DUE TO MULTIPLE ISSUES, ASSUMPTIONS,

DEFINITIONS OR ALGORITHMS INVOLVED

PANELLIST MAKES A RELATIVE COMPARISON TO A BASE CASE

AND DOES NOT SUFFICIENTLY ADJUST HIS RESPONSE WITH

RESPECT TO THE BASE CASE ESTIMATES

PANELLIST’S OPINION IS OVERLY INFLUENCED BY THE RECENT

OCCURENCE OF A DRAMATIC EVENT

UNDERESTIMATING OF UNCERTAINTY

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TRAINING EXERCISE

CONDUCTED AS A PART OF FIRST GROUP MEETING

CONSISTED OF ASKING THE PANELLISTS A NUMBER OF

QUANTITATIVE QUESTIONS WITH KNOWN ANSWERS BUT IN A

SUBJECT AREA WITH WHICH THEY ARE RELATIVELY

UNFAMILIAR

THE PURPOSE OF THIS QUESTIONS

TO ACCUSTOM THE PANELLISTS TO THE TYPE OF RESPONSES

THAT WILL BE REQUIRED TO PROVIDE IN THEIR ELICITATIONS

TO DEMONSTRATED TO THE PANELLISTS THAT ALTHOUGH

INDIVIDUALLY MAY BE HIGHLY UNCERTAIN ABOUT THEIR

RESPONDSED, THE GROUP RESPONSE IS CLOSER TO THE

CORRECT ANSWER THAN THE INDIVIDUAL RESPONSES.

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INDIVIDUAL ELICITATIONS

EACH PANEL MEMBER HAS CERTAIN TIME (IN MONTHS) TO PREPARE THEIR ELICITATION RESPONSES

DURING THIS TIME PERIOD INDIVIDUAL ELICITATION SESSIONS ARE CONDUCTED SEPARATELY BETWEEN EACH PANEL MEMBER AND THE FACILITATION TEAM

THE OBJECTIVES FOR THE INDIVIDUAL ELICITATION SESSIONS

IDENTIFY ANY INCONSISTENCIES BETWEEN THE QUANTITATIVE AND QUALITATIVE RESPONSE

PROVIDE ADDITIONAL CLARIFICATION TO THE ELICITATION QUESTIONS, IF NECESSARY

IDENTIFY NECESSARY FOLLOW-ON WORK FOR EACH PANEL MEMBER

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PRACTICAL APPLICATION – TRANSITION

BREAK SIZE ELICITATION STRUCTURE

PRACTICAL APPLICATION – TRANSITION

BREAK SIZE ELICITATION STRUCTURE

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MATERIAL AGEING DEGRADATION

MECHANISMS

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REACTOR PRESSURE VESSEL FAILURE

MODES

REACTOR PRESSURE VESSEL FAILURE

MODES

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LOADING HISTORY VARIABLES

30.11.2011 43

CONCLUSIONS

EXPERT ELICITATION IS FORMAL PROCESS FOR PROVIDING

QUANTITATIVE ESTIMATES OF THE FREQUENCIES OF

PHYSICAL PHENOMENA WHEN THE REQUIRED DATA IS

SPARSE AND WHEN THE SUBJECT IS TOO COMPLEX TO

ADEQUATE MODEL

THE PROCESS CONSISTED OF A NUMBER OF STEPS

THE PROJECT STAFF IDENTIFIED MANY OF ISSUES TO BE

EVALUATED THROUGH A PILOT ELICITATION

THE PANEL MEMBERS ARE SELECTED FOR THE FORMAL

ELICITATION

30.11.2011 44

CONCLUSIONS – cont. 1

THE PROJECT STAFF GATHERS BACKGROUND MATERIAL AND PREPARES AN INITIAL FORMULATION OF THE TECHNICAL ISSUES

AT THE INITIAL MEETING THE PANEL DISCUSES THE ISSUES AND DEVELOPED A FINAL FORMULATION FOR THE ELICITATION STRUCTURE

AFTER INITIAL MEETING THE STAFF PREPARE A DRAFT ELICITATION QUESTIONNAIRE AND ITERATED WITH THE PANEL TO DEVELOPED FINAL QUESTIONNAIRE

THE PANELLISTS DEVELOP THEIR INITIAL ESTIMATES

A SECOND MEETING IS HELD WITH ENTIRE PANEL TO REVIEW THE ELICITATION QUESTIONS AND TO FINALIZE THE FORMULATION OF REMAINING TECHNICAL ISSUES

AT HOME INSTITUTIONS THE PANEL MEMBERS PERFORMED ANALYSES AND COMPUTATIONS TO DEVELOPED ANSWERS TO THE ELICITATION QUESTIONNAIRE

30.11.2011 45

CONCLUSIONS – cont. 2

IN THE CASE OF PROBABILISTIC QUESTIONS THE INDIVIDUAL

AND GROUP ESTIMATES FOR THE MEANS, MEDIANS, 5TH AND

95TH PERCENTILES OF THE EVENT UNDER EVALUATION

FREQUENCY DISTRIBUTIONS SHALL BE CALCULATED

THE STAFF DEFINE PRINCIPAL ASSUMPTIONS AND CHOICES

THE EXPERT ELICITATION PROCESS US NRC USED TO

EVALUATE REACTOR RISK (NUREG-1150)

DEVELOP SEISMIC HAZARD CURVES (NUREG/CR-6372)

ASSESS THE PERFORMANCE OF RADIOACTIVE WASTE

REPOSITORIES (NUREG/CR-5411)

30.11.2011 46

CONCLUSIONS - RESULTS

DEFINITION OF THE TRANSITION BREAK SIZE:

Is a break of area equal to the cross-sectional flow area of the inside

diametr of specified piping for a specific reactor

The specified piping for a PWR is the largest piping attached to

the reactor coolant system

For BWR is the feed water line inside containment or RHR

system inside containment

TBS for PWRs : 12 to 14 inch = 30.5 to 35.6 cm

TBS for BWR : 20 inch = 50.8 cm

QUESTION: CAN SSE INFLUENCET TBS?

30.11.2011 47

SEISMIC CONSIDERATIONS FOR THE

TRANSITION BREAK SIZE

Approach and Key Steps for Unflawed Pipe Evaluation:

PGASSEACC /

Approach and Key Steps for Unflawed Pipe Evaluation; = ACC/SSEPGA

30.11.2011 48

SEISMIC CONSIDERATIONS FOR THE TRANSITION

BREAK SIZE cont. 1

Example of the Seismic Hazard Curves

30.11.2011 49


TRANSITION BREAK SIZE cont. 2

Factor of Safety

THE GENERALIZED FORM OF THE FACTOR OF SAFETY IS AS FOLLOWS

LOGNORMAL DISTRIBUTION, LOGARITHMIC STANDARD DEVIATIONS

…. Capacity factor

STRUCTURE RESPONSE

PIPING, EQUIPMENT, COMPONENTS

SF = 1/F

FAAFA cMVZC ,

rsc FFF

nlecmcmdincohSSIgmthSSrs FFFFFFFFFF

crers FFFF

enlecmceanemdessre FFFFFFFF

30.11.2011 50

cF



Estimates of Normalized Stress Ratios and Probability of

Exceedance

Hazard Curve for Plant of Interest Probability

Acceleration Acceleration

m s-2 g

Probability of

Exceedance

=

A/MVZPG

Corrected

Seismic

stresses

x SF x SSE

(N+Seismic

Value)/Sm

0,5 0,051 1,21 E-3 ..

..

..

1,0 0,102 4,1 E-4 ..

..

..

....

....

....

....

....

....

....

....

....

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....

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....

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....

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~ ~ ~ ~ ~ ~ ~

30.11.2011 51



Probability of exceedance versus maximum normal + seismic

stress

30.11.2011 52



CONCLUSIONS

The US NCR has been considering revision of the regulatory

requirements for the ECCS

State of the art: ECCS shall be sized to provide adequate makeup water

to compensate LLOCA

Concept of the transition break size proposed

Methodology of evaluation of seismic effects presented

30.11.2011 53

www.ujv.cz

Thank you for your attention

30.11.2011 54

special seismic problems

Documents

revision of asme code

issued asme code section

code asa b

pressure piping

boiler code

issued section

piping design

american standard code