Experience Based Methods for ALWR Kassawara

8/9/2019 Experience Based Methods for ALWR Kassawara

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PURPOSE

DR FT

USE OF EXPERIENCE-BASED SEISMIC QUALIFICATION

METHODS FOR ADVAN CED LIGHT WATER REAcrOR

EQUIPMENT AND DISTRIBUTION SYSTEMS

Dr, R.

P.

Kassawara, Advanced

Reactor

Corp.

Mr. P. W. Haves, MPR Associates

Mr. r< Merz, EQE

Dr. P. Ibanez, ANCO Engrs.

The electric utility industry through the Advanced Reactor Corporation ARq and the

Department

of

Energy have initiated a joint program to

perfonn

first-of-a-kind

engineering

FOAKE)

for the advanced light water reactor (ALWR) plants. The

FOAKE Program has the goals of (1) completing engineering on certified ALWR designs

in sufficient detail to define firm cost and schedule estimates: (2) ensuring the existence

of an infrastructure to provide resources for and manage completion of detailed designs;

and (3) defining a process to achieve design standardization beyond that required for

certification.

One

of the FOAKE Phase 1 projects involves Equipment Seismic

Qualification. The objective

of

this project is to develop criteria and procedures for

experience-based seismic qualification

of

electrical and mechanical equipment and

distribution systems_

Experience-based seismic qualification

of

equipment involves the collection of data

describing the perfonnanco:

of

equipment classes based on (1) actual earthquake

experience, (2) shake table test results or, (3) analyses demonstrating the capability to

withstand seismic loads. The data

is

evaluated to establish a demonstrated seismic

capacity

of

an t:ntire class

of

equipment. The data

is

also used to define equipment

parameters such as rating, manufacturer.

or

vintage that are encompassed by the

experience base for a particular equipment class. The evaluation process results in the

establishment of a set of inclusion rules and specifications that must be satisfied to apply

the experience base for equipment seismic qualification.

The purpose of this paper

is

to provide a description of the seismic qualification project

and a summary

of

results. -

BACKGROUND

Current criteria and guidelines for seismic qualific:l ion of equipment are included in

Appendix A of 10CFR Part 100, [1]1 in the NRC's Standard Review Plan [2] and

related regulatory guides. and in industry standards such

as IEEE

Std. 344-1987 Pl.

These guidelines and criteria recognize. to varying degrees. a number of different

l 'lumbers in brackets [ J refer to reterences.

[-



technical approaches to demonstrate that important electrical and mechanical equipment

will remain functional during and after a design.basis earthquake. These methods

include:

• Testing, typically performed using a seismic shake table which simulates

eanhquake

motions;

• Analysis. including dynamic analysis and equivalent static analysis methods;

• Earthquake and test experience, that is, demonstration of equipment

capability based on performance

of similar equipment in past eanhquakes

or dynamic test environments; and

• Combinations of the above.

Of

these methods. testing and analysis have been the more common approaches used for

post·1975 nuclear plants. A considerable amount of equipment qualification also has

been based on extension of test or analysis results for similar equipment, which

is

tantamount to utilization of experience data.

The use of experience data on the seismic performance of equipment to demonstrate

seismic capability of similar equipment has also been used extensively in seismic

verification of equipment for operating nuclear plants. This use of past performance

data has been formalized

in

the past several years for the purpose

of

resolving

Unresolved Safety Issue (US ) A·46, "Seismic Qualification of Equipment in Operating

Nuclear Power Plants." [4] This approved approach for resolution of US A-46 utilizes

data on the performance of typical power plant equipment and cable tray and conduit

systems

in

real earthquakes as well as in past shake table tests to assign generic seismic

capacities to classes of equipment which fall within the bounds

of

the experience

database. These bounds are defined by specific equipment attributes and inclusion rules.

The earthquake and test data on which the capacities are based are referred to

collectively as the experience d:ltabase.

The experience database collected for resolution of US A·46 is based on performance of

equipment in over 30 eanhquakes and in numerous seismic qualification tests. Seismic

capacities assigned to a large number of equipment classes based on the observed ground

motions have been established and are referred to

as

the "Reference Spectrum." Generic

seismic capacity curves based on test data are referred to as "Generic Equipment

Ruggedness Spectra" (or

GERS

for specific classes of equipment and are generally

higher than the earthquake experience·based capacity (i.e

•

the Reference Spectrum).

The experience database collected for resolution of USI A·41i. which concentrated on

equipment generally of 1970's vintage, is constantly being expanded through EPRI's

ongoing post·earthquake investigation program to include more recent earthquakes

(through 1992 and modern vintage equipment. The use of this seismic experience data

for demonstration of seismic adequacy of newly deSigned equipment requires design

controls and engineering evaluations. These

will

ensure that new equipment to which

·2·



experience·based methods

are

applied can be represented by equipment whose seismic

performance has been demonstrated within the experience data.

The earthquake

and

seismic test experience data is supplemented by analytical .

experience data. The term analytical experience data as used in this report applies not

only to explicit seismic analyses but also to other technical information such as analyses

of

equipment response to operational loads or ASME Code analyses which can be shown

to demonstrate a level

of

seismic ruggedness in an equipment item.

Recognizing the lessons learned from this seismic experience, the EPRI Utility

Requirements Document URD)

[5]

states

that

the

ALWR

seismic Category 1

equipment will

be

qualified using seismic experience data where it

is

cost effective and is

technically justifiable.

The project has evaluated the application

of

experience·based methodology to the

seismic qualification

of

ALWR equipment and, for those applications where it is justified,

provides recommended lower bound seismic capacities, together with guidelines for

application of the methodology to the procurement and installation of

AL

WR equipment.

PROJEcr

ORGANIZATION

The project was performed under the management and direction

of

ARC. ARC was

assisted by a contractor team consisting

of

MPR Associates. the primary contractor. EQE

Engineering Consultants and ANCO Engineers. The project team interfaced with the

ALWR project within the Electric Power Research Institute (EPRI). with the nuclear

steam supply system (NSSS) vendors of ALWR plants. Westinghouse, Combustion

Engineering and Ge:neral Electric. and with NUMARC. The project team was provided

independent review and guidance from a Utility Advisory Panel consisting

of

utility

representatives from Commonwealth Edison. Duke

Powe:r

Wisconsin Electric, Southern

Company Services. Southern Nude:ar Operating Company and GPUN. The project also

interfaced technically with NRC taff members from the Offices

of

Nuclear Regulatory

Research and Nuclear Reactor Regulation and a team

of

outside consultants.

SUMMARY

OF

RESULTS

ALWR Equipment Charncterization

Seismic Category 1 equipment descriptions in ALWR S,andard Safety Analysis Reports

(SSARs)

[6].

[7]

[8]

were reviewed. The results

of

the review indicate that some new

equipment designs. not represented in the existing experience database. are planned fer

the ALWRs. However. the majority of the seismic Category 1 equipment for the

AL WR's reviewed

will

be conventional equipment types which are represented

in

the

experience database:. These include most of the .J..LWR pumps, valves. electric power

equipment. diesel generators. inverters. and chillers. Equipment which is expected to be

of

new and/or advanced design includes solid state digital control equipment. and a few

special valves. For a number of the conventional electrical and mechanical equipment

ciJsses defined here:n. '.·intJge issues

Jre

not e x p e ~ t e to

be

significant·.that

is.

3



Seismic Capacity

Review of experience data from earthquakes which occurred sUbsequent to

USI

A-46

investigations (i.e., in 1985 through 1992) indic::ne that modern vintage power plant

equipment is represented and that the equipment performance is consistent with that

observed prior to the 1980 s. Further, the records

of

earthquake motion from the more

recent earthquakes support the reference seismic capacity spectrum (i.e., the Reference

Spectrum) developed for earlier vintage equipment

in

the

USI

A-46 resolution. 9) This

reference capacity spectrum is shown in Figure 1 and is considered a reasonable lower

bound seismic capacity for the newer equipment as well as the older vintage equipment

classes.

t

should also be noted that a significant amount of seismic test data exist for certain

ALWR equipment classes, and the resulting capacity. spectra are typically higher

than

the

earthquake experience capacity spectrum. For example, data for certain types

of

station

batteries show spectral capacity levels of about 4

g.

transformers have spectral capacity

levels of about 3 g and valve motor oper::nors show spectral capacities over 20

g.

Analyses and fragility test data used for Probabilistic Risk Assessment PRA) and Seismic

Margin studies as well as experience reinforced by the judgment of

experienced seismic

engineers demonstrate that the seismic capacities of mechanical equipment such as gate

and globe valves, horizontal and certain vertical pumps, and electrical motors have

capacities well above the earthquake experience-based capacity levels, and may be

considered inherently rugged for essentially any likely AL

WR

site. These

data

sources

have been augmented for the selected equipment classes by a detailed review

of

equipnient functional characteristics and

of

the codes and standards invoked in

procurement documents. These requirements, while not necessarily addressing seismic

loading explicitly, ensure

an

inherent high level of seismic ruggedness and eliminate the

need for explicit seismic qualification testing for such classes as pumps, motors, valves

and motor operators.

ALWR

Seismic Demand

The ALWR standard plants are being designed to a free·field ground motion

characterized

by

a Reg. Guide

1.60

(10] response spectrum anchored at a peak ground

acceleration of 0.3 g. This input ground motion spectrum is also shown in Figure 1.

A review

of

AL

WR

designs shows that buildings which contain most seismic Category 1

~ q u i p m e n t

are massive, stiff. reinforced concrete buildings with significant embedment

(i.e., in the range

of

40 to 80 feet for both rock and soil sites). These design

characteristics indicate that in-structure seismic demand requirements for ALWR

equipment should fall below the seismic capacity spectrum obtained from

~ r t h q u k e

experience (Figure I) for all building elevations up to grade level. and possibly higher.

Review of equipment layouts for these plants shows that the majority of conventional,

electrIcal and mechanical equipment will be at grade level

or

below.



In

summarY while manv of the AL WR seismic demand spectra for equipment are not

. .

yet finalized. and some demand spectra for higher plant elevations

will

likely exceed

earthquake e:,:perience-based capacity levels, the seismic demand for AL WR equipment

is expected to be bounded by earthquake experience data for a significant fraction of

applications at and below grade levels.

Equipment Seismic Qualification Guidelines for ALWR Equipment

The approach taken for experience-based qualification of LWR equipment involves:

• review

of

earthquake, seismic shake table, and analytical experience

data

for

each equipment class;

• determination of the seismic capacity implied by the experience data. Two

levels of seismic capacity have been identified; one based only on

earthquake experience referred to hereafter as Level A) and one based on

all available test, analysis and earthquake experience data Level B);

• determination of any equipment technical requirements which should be

invoked to ensure ruggedness

or

to avoid a potential seismic vulnerability,

and;

• documentation of the results of the experience data review in the fonn of

supplementary equipment procurement and installation specification

requirements which assure seismic capacity levels defined for each class.

The resulting procurement and installation specification requirements for those ALWR

equipment classes selected

by

the FOAKE Project for development of experience·based

seismic qualification are summarized below. Seismic capacity levels assigned to these

equipment classes nre provided

in

Table 2

Horizontal Motor-Drjven Pumps - Umitations are imposed on pump size and type to

ensure applicability of experience data. Requirements for maintaining pump and driver

alignment and for accommodating axial thrust loads are specified. Standard pump design

practice and the resultant level of inherent ruggedness of various pump components are

identified. Anchorage, mounting and service connection installation details are specified.

Specification requirements are defined for two levels of seismic capacity. -

Vertical Motor-Driven Pumps - Limitations are imposed on pump size and type to

ensure applicability of experience data. Requirements for maintaining pump and driver

alignment and for sizing radial bearings are defined. Standard pump design practice and

the resultant level of inherent ruggedness of various pump components are identified_

Anchorage, mounting and service connection insmllation details are specified.

Specification requirements are defined for two levels

of

seismic capacity.

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Motor ODe rated Valves - Limitations are imposed on minimum valve size and on motor

operator types to ensure applicability of experience data. Valve body and yoke design

and material requirements. including specific checks on operator mass/moment arm

relative

to

the valve. are specified. Seismic inputs for required ASME Code and Generic

Letter 89 10 weak-link analyses are defined. Installation details covering location

of

motor controls. electrical and control lines. and valve support are specified. Specification

requirements for motor operated valves are defined for two levels of seismic capacity.

Manual/Check Valves - Valve body and yoke design and material requirements are

specified. Specification requirements are defined for one level of seismic capacity.

Thermal Element Assemblies - Applicability

of

experience based seismic qualification

methods

is

limited

to

resistance temperature detectors

or

thermocouples. Mounting and

wiring details and restrictions to ensure adequate stiffness are specified. Specification

requirements are defined for two levels of seismic capacity.

Diesel Generator Units - Coniiguration and stiffness of mounting skid is specified.

Engine·mounted auxiliary components to which specified capacity levels apply and

external auxiliary components to which specified capacity levels do not apply are clearly

identified. Use of vibration isolation mounts is prohibited. Anchorage and load

path

design requirements for skid mounted auxiliary equipment are specified. Provisions to

limit sloshing at engine fluid free surfaces are specified. Specification requirements

are

defined for

two

levels of seismic capacity.

Transformers - Limitations are imposed on transformer type and rating to ensure

applicability of experience data. Transformer coil support requirements and clearances

between electrical conductors and structure are defined. Anchorage details are specified.

Specification requirements are defined for

two

levels

of

seismic capacity.

Batteries on

Racks·

Limitations are imposed on battery size. cell type and manufacturer

to

ensure applicability of experience data. Requirements for positive internal plate

suspension details are defined. Installation of cells in racks and rack structural and

anchorage requirements are specified. Specification requirements are defined for two

levels of seismic capacity.

ALWR

istribution

Svstem DeSign Guidelines

The approach taken for development of experience·based design guidelines for ALWR

distribution systems involves:

•

review of earthquake and shake table test experience data for distribution

systems and their supports.

definition of functional requirements for distribution systems subject to

seismic loading,



• development of simplified design

by

rule methods for AL

WR

cable trays,

conduit and HVAC dueting, and

• Use of experience data to demonstrate that design rules will ensure

achievement of distribution system functional requirements.

The proposed approach provides a preferred alternative to currently approved dynamic

analysis methods developed for elastic structures. The approach includes:

qualitative criteria based on observations from earthquakes and tests

quantitative, static design checks, and _

additional provisions to ensure leak tightness of

V

AC ducts

Such an approach has significant benefits in addition. to cost effectiveness; it is expected

to improve safety by providing better access

for

inspection/maintenance and avoiding

over-restrained systems and over-sized supports.

CONCLUSIONS

The results of this FOAKE project demonstrate that for certain relatively standard and

inherently rugged equipment classes, experience-based seismic qualification methods,

supplemented by equipment-specific procurement and installation requirements, provide

a technically justifiable and cost-effective alternative to seismic shake table tests and

dynamic analysis. The project results also provide a practical, design-by-rule approach

for

distnbution systems which

is

consistent with earthquake and test experience and

which will avoid over' design of these systems and their supports.

REFERENCES

l 10 CFR Part LOO Appendix A - Seismic and Geologic Siting Criteria

for

Nuclear

Power Plants.

2. NUREG-0800 - Standard Review Plan for the Review of Safety Analysis Reports

for

Nuclear Power Plants.

3. IEEE Std 344-1987, IEEE Recommended Practice for Seismic Qualification of

Class IE Equipment for Nuclear Power Generating Stations.

4.

NUREG-I030 - Seismic Qualification of Equipment in Operating Nuclear Plants

Unresolved Safety Issue A-46.

5. EPRI Advanced Light Water Reactor Utility Requirements Document issued

3/90.

6. ABWR Standard Safety Analysis Report - GE Nuclear Energy.

7.

AP600 Standard Safety Analysis Report - Westinghouse Ekctric Corporation.

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8. Combustion Engineering Standard Safety Analysis eport· Design Certification.

9. Sandia Report SAI'l D92·0140 . Part I . Use of Seismic Experience and Test Data

to Show Ruggedness of Equipment in Nuclear Power Plants. Part II Review

Procedure to Assess Seismic Ruggedness of Cantilever Bracket Cable Tray

Support.

10. USNRC Regulatory Guide 1.60 . Design Response Spectra for Seismic Design of

Nuclear Power Plams.

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1

2)

3)

4)

5)

6)

7)

8)

9)

10)

11)

12)

13)

14)

15

16)

17)

18)

19)

20)

21)

22)

Table 1

Potential for Applying Experience Data for L

WR

Equipment Seismic Qualification

Group 1

Group

2·

High

Intermediate

Motor Control Centers

Low Voltage Switchgear

Metal Clad Switchgear

Transformers

X

Chillers

X

Fans

X

Instrument Racks

X

Control Panels

Horizontal Pumps

X

Vertical Pumps

-

Normal

X

Deep-Well/Can

X

Batteries

X

Manual/Check Valves X

Motor Operated Valves X

ir Operated

Valves X<

f >

X

-

Pilot

Operated

Relief Valves

X<

Air Handlers

X

Battery Chargers 1nveners

X

Panel BoardslSwitchboards

X

Thermal Element Assemblies X

Air Compressors

X

Diesel Generator Units

X

Relays

-

Solid State

X

.

Electro Mechanical

TOT L

9

11

-to·

Group

3

Ow

X

X

X

X

1 >

X

X

6



Spectral Acceleration gj

1.4

1.2

1

O S

0.6

0 4

..

0 2

V

0.1

V

I

I I I I I

5 Damping

I I

•

I I

I

I

~ ~

Experience Based

I

apacity

I I I I

1\\

V

I I I

IIII -AI .

III

LWR Design

I 11111

round Motion

I I I I IIII

j ,

v

\

I IIIII1

V

I I

III1

I

10

100

Frequency

Hz)

RG 1.60 at 0.3g Reference Spectrum

Figure 1. Comparison o Reg Guide l 60

and Reference Spectrum

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Experience Based Methods for ALWR Kassawara

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