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SEISMIC EVALUATION OF

EQUIPMENTS FOR

NUCLEAR POWER PLANT APPLICATIONS

Pradeep S

30 May 2016, IISc Bangalore

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Types of Seismic Vibrations

Natural Events

•Earthquakes

•Volcanoes

•Tsunami

•Microseisms

Man-made events

•Explosions

•Reservoir seismicity

•Rock burst (mines)

•Induced seismicity

•Cultural noise

Significance

Constant updating of load spectra, evolution of standards, regulations,

rules and calculation methods has increased the importance of seismic

evaluation of NPP structures.

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Seismic Qualification (Earthquake)

•Equipments are classified as Class I, Class II and Class-III.

•ASME Section III Div 1 subsection NB, NC, ND based on the seismic

safety class of the equipment.

•Supports qualified as per ASME section III Div 1 subsection NF.

Rules

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•Equipments are classified as:

•Passive equipments

•Active equipments

Passive equipments are qualified for structural integrity and active

equipments with an additional functional operability criteria.

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TYPICAL FLOOR RESPONSE SPECTRA

•Response Spectrum Method

•Time history

•Equivalent static method

Methods

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Individual loads to be considered :

• Dead Weight

• Internal Pressure

• External Pressure

• Temperature

• Nozzle Loads (from piping systems)

• Response spectra (OBE and SSE)

Typical loads

Design/

Service level Load combination

Stress limits

(Class-1) (NB)

(Class-2 & 3)

(NC & ND)

Design condition Dead weight + Design Pressure +

Nozzle loads

σm ≤ 1.0 S, σl ≤ 1.5 S

(σm or σl) + σb ≤ 1.5 S σm ≤ 1.0 S

(σm or σl) + σb ≤ 1.5 S Service Level A

Operating Pressure + Thermal

(operating temp) + Nozzle Loads σm/σl + σb + Q ≤ 3S

σm/σl + σb + Q + F = S

U<1 for fatigue Service Level B

Dead weight + Design Pressure +

Thermal (operating temp) + Nozzle

loads + OBE

σm ≤ 1.1 S

(σm or σl) + σb ≤ 1.65 S

Service Level C Dead weight + Design Pressure +

Nozzle loads + SSE

σm ≤ 1.2S

σl ≤ 1.8S

(σm or σl) + σb ≤ 1.8 S

σm ≤ 1.5 S

(σm or σl) + σb ≤ 1.8 S

σm = Generalized membrane stress

σl = Localized membrane stress

σb = Bending stress

S = Allowable stress

U = Cumulative usage factor

Q, F = Secondary and peak stress

and load combination

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EQPT, PIPING & SUPPORTS

6

25m

40m

10m

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CABLE TRAY SUPPORT STRUCTURE

27 m

3 m

INITIAL DESIGN

FINAL DESIGN

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4200 KW DG SET

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Parts considered for

qualification:

- Base frame (skid)

- Engine crank case

- Alternator assembly

- Crank shaft

- Turbocharger support

- Turbocharger

- Fly wheel

- Flexible coupling

- Oil sump

•Allowable stress limits of

the material as per

manufacturer’s standard

engineering practice.

•Functional operability

checked

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4.2 MW DG SET

Transverse forces on bearings

Lateral forces on cylinder

Piston force - Axial

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Load-1 = Engine dynamic forces

Load-2 = Alternator normal torque

Load-3 = Self/Dead weight

Load-4 = Loads due to seismic condition (OBE)

Load-5 = Loads due to seismic condition (SSE)

Load-6 = Short circuit load

LOAD COMBINATION FOR QUALIFICATION

•LC-1 = Loads under normal running condition

= Load-1+ Load-2 + Load-3

•LC-2 = Engine running + seismic (OBE)

= LC-1 + Load-4

•LC-3 = Engine running + seismic (SSE)

= LC-1 + Load-5

•LC-4 = Abnormal running condition = LC-1 + Load-6

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LOADS AND COMBINATIONS (4.2 MW DG SET)

Alternator Load Application

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Sloshing inside a tank (details)

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•Eigen value analysis with missing mass

correction

•Dynamic analysis carried out for sloshing effects

•Housner model used to adequately represent

the behavior

•Shell qualified as per ASME Sec III, ND

•Supports qualified as per ASME Sec III, NF

•Embedded plate size checks

•Weld adequacy checks

•impulsive mass, mi

•convective mass, mc

•mass of water, mw

•height of mi from bottom, hi

•height of mc from bottom, hc

•maximum height of fluid, h

•spring stiffness, Kc

Sloshing effect modeling

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SADDLE SUPPORTED TANKS

•Overall length of tank: 6202mm

•Outer diameter: 2324mm

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•Visited site (RAPP) to check availability of usable EPs and

area around the building

•Designed the tower from scratch

•Strength design of columns.

•Strength design of bracings.

•Strength design of stacks.

•Strength design of structure foundation bolts.

•Strength design of structure base plate and gussets.

•Pull out shear failure mode of foundation.

LATTICE TOWER SUPPORTED CHIMNEY

3 exhaust pipes entering the tower Silencer arrangement on the roof Complete lattice tower

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CONCLUSION

Seismic qualification is mandatory for all equipments before they are

installed in a Nuclear Facility.

ASME Sec III, is applicable for qualification based on the safety class of the

equipment.

FE Software provides a comprehensive assessment for qualification.

We have developed macros & scripts for load combination and qualification.

Successfully completed >45 projects on seismic qualification.

DAE entities & their EPCs: NPCIL, IGCAR, BARC-NRB and Punj Lloyd/

L&T

ITER, France through AMEC Nuclear, UK.

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ProSIM R&D Pvt Ltd #4, 1st B Main, 1st N Block, Rajajinagar, Bangalore – 560010

Ph: +91 80 23323020, Fax: +91 80 23323304

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