EVOLUTION OF SEISMIC DESIGN BASIS FOR INDIAN

EVOLUTION OF SEISMIC DESIGN
BASIS FOR INDIAN NUCLEAR
POWER PLANTS
Prabir C. Basu
AERB, India
Evolution of seismic design basis for Indian nuclear power plants
Outline
• Introduction
• Evolution of seismic design basis
• Design basis for seismic re-evaluation
• Design basis for future reactors
• Concluding remarks
Evolution of seismic design basis for Indian nuclear power plants
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Introduction
• NPP program commenced in
India in 1969 with commissioning
of TAPP-1&2 (BWR) at Tarapur.
• Subsequently NPPs (PHWR)
were designed (indigenously),
constructed commissioned and
being operated.
• Status of engineering of new
generation power reactors
– VVER 1000: finishing stage of
construction
– PFBR 500: Advanced stage of
construction,
– PHWR 700: advanced design stage
NPP locations in India
Evolution of seismic design basis for Indian nuclear power plants
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Evolution of seismic design basis
• 60% of the land area in India is considered susceptible
to earthquake shaking of intensity VII and above.
• Three distinct stages from a regulatory perspective
1. Pre-regulatory stage
2. Incipient regulatory stage
3. Present stage
4. New stage for future generation of NPP
The regulatory authority, Atomic Energy Regulatory
Board (AERB), was formed in 1983.
• Regulatory practices of seismic safety, have undergone
continuous evolution and improvement over the years.
Evolution of seismic design basis for Indian nuclear power plants
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Evolution of seismic design basis…
Pre-regulatory stage
• This stage covers the NPPs designed / constructed /
commissioned before the formation of AERB.
• The seismic design basis for the reactors in this stage
generally followed Indian Standard (IS) codes of
industrial units.
• NPPs of this stage are,
– TAPS–1&2 (BWR), Tarapur.
Seismic loading was determined following IS875 1957. All
structures and mechanical components of the station and
buildings be designed to resist a horizontal force equivalent to
0.10 times the gravity load.
Evolution of seismic design basis for Indian nuclear power plants
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Evolution of seismic design basis…
Pre-regulatory stage
– RAPS – 1&2 (PHWRs), Kota
According to IS875 1057 the site was not prone to seismic
activity as it fell in geologic zone – I. and not prone to seismic
activity. Severe earthquakes of Kutch (1894) and Bihar (1934)
were felt here. These earthquakes were estimated to generate
horizontal acceleration of 0.4g. Considering this the NPP was
designed for horizontal load up to 0.05 times gravity load.
– MAPS – 1&2 (PHWRs), Kalpakkam
The site falls in the In zone–I of IS1893 1966. A few temmor
occurred in areas at about 25 Km away from the site in
past.Taking this into account the containment building was
designed for a horizontal seismic coefficient of 0.1g and
remaining plant structures for 0.05g.
Evolution of seismic design basis for Indian nuclear power plants
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Evolution of seismic design basis…
Incipient regulatory stage
• This stage covers NPP commissioned after formation of
AERB but designed and constructed prior to AERB.
During this stage, AERB siting code AERB/SC/S and
safety guide on determination of DBGM parameters
AERB/SG/S11 were prepared and published.
• SSE or SL-2 level and OBE or SL-1 level were
considered. DBGM parameters were derived following
similar approach of IAEA / USNRC.
• NAPS – 1&2 (PHWR), Narora
Horizontal PGA: 0.3g for SSE and 0.15g for OBE
• KAPS – 1&2 (PHWR), Kakrapar
Horizontal PGA: 0.2g for SSE and 0.1g for OBE
Evolution of seismic design basis for Indian nuclear power plants
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Evolution of seismic design basis…
Present stage
• AERB published “Code of Practice on Safety of Nuclear
Power Plant Siting”, AERB/SC/S in 1990, and “Safety
Guide on Seismic Studies and Derivation of Design
Basis Ground Motion Parameters”, AERB/SG/S-11.
• These two regulatory documents are the requirements
and guidelines for derivation of DBGM parameters of
present stage.
• The regulation specifies rejection criteria,
– Active fault within 5km radius
– Potential of liquefaction, slope instability, ground
failure/subsidence if there is no engineering solution.
Evolution of seismic design basis for Indian nuclear power plants
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Evolution of seismic design basis…
Present stage
• It specifies DBGM in terms of following
– PGA
– Response spectral shape
– Spectrum compatible time history
• It provides guidelines on methodology for conducting
seismo-tectonic investigations, deriving the seismic
design basis and also to checking the suitability of the
site from seismic safety consideration.
• Guidelines are based on geological and seismological
investigations in four scales, regional (300 km radius),
intermediate range (50km radius), local (5km radius) and
site area (within plant boundary), and MEQ data.
Evolution of seismic design basis for Indian nuclear power plants
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Evolution of seismic design basis…
Present stage
PGA values of different sites
Evolution of seismic design basis for Indian nuclear power plants
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Evolution of seismic design basis…
Seismic re-evaluation of existing NPP
• Derivation of new seismic DBGM parameters of sites
following present regulation for new plant calls for
seismic reevaluation of existing NPP, if any co-located.
• Exercise of seismic re-evaluation of old NPPs with the
new seismic design basis has been initiated
• PSHA approach was adopted to derive review basis
parameters (uniform hazard spectrum) for seismic reevaluation of fast breeder test reactor (FBTR) at
Kalpakkam.
Evolution of seismic design basis for Indian nuclear power plants
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Design basis for future NPPs
• Work for revision of AERB/SG/S11 has been initiated for
the sites of new reactors of advanced generation.
• Guiding factors of the revision are,
– Experience gained over the years on seismic safety of NPP.,.
– New information/data and advancement on earthquake
engineering
– Special requirements of new reactors.
• Safety assessment of reactors are gradually becoming
more PSA centric, which invariably results in derivation
of DBGM parameters of new reactors by probabilistic
seismic hazard analysis (PSHA). This is in addition to
the inherent rationality of the method.
Evolution of seismic design basis for Indian nuclear power plants
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Design basis for future NPPs
•
Niigataken – Chuetsu – oki (NCO) earthquake
induced acceleration about three time the design basis
at the Kashwazaki – Kariwa NPP (KK-NPP) site. This
raised a probable issue how to deal with the beyond
design basis earthquakes (BDBEq) in new reactors as
well as the existing one.
Evolution of seismic design basis for Indian nuclear power plants
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Design basis for future NPPs
PSHA
• Data/information on strong motion earthquake,
seismotectonic status and site-specific attenuation
relation of the region are requirements for a robust
PSHA
• Peninsular India, where most of the Indian nuclear
facilities are located poses unique. challenges in
application of PSHA due to
– Sparse data,
– Lack of information on seismotectonic characteristics, and
– Non-availability of regional specific attenuation relationships.
• This calls for innovative approach to conduct PSHA of
the sites in this region.
Evolution of seismic design basis for Indian nuclear power plants
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Design basis for future NPPs
PSHA
• The approach fro PSHA analysis of these sites should
have following characteristics
– It is amenable to accommodate all advancement of PSHA
tools like attenuation relation ship
– At the same time can take care of uncertainties arising out of
data inadequacy.
• PSHA aided by sensitivity study of input and technique
to determine parameters along with logic tree could be
an useful approach.
Evolution of seismic design basis for Indian nuclear power plants
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Design basis for future NPPs
PSHA
B Value
B value-range
Rate Apportionment
Mmax
Focal Depth
Attenuation
relation
Atkinson, 0.1
Mean-1σ
0.125
Actual data
0.9
Mean
0.75
Mean+1σ
0.125
Mean-1σ
0.125
GSHAP
0.1
Prop. Energy,
0.5
Mean
0.75
Mmax
(max)
0.125
Mmax (mean)
0.75
Mmax (min)
0.125
10 km, 0.25
Abramson, 0.25
20 km, 0.5
Boore, 0.25
30 km, 0.15
Campbell, 0.15
Mixed, 0.1
Sadigh, 0.25
0%, 0.5
25%, 0.3
50%, 0.2
Same ‘b’ value,
0.5
Prop. Energy,
0.5
Added
dispersion
Atkinson, 0.1
Mmax
(max)
0.125
Mmax (mean)
0.75
Mmax (min)
0.125
Mean+1σ
Same ‘b’ value,
0.125
0.5 power plants
Evolution of seismic design basis for Indian nuclear
0%, 0.5
10 km, 0.25
Abramson, 0.25
20 km, 0.5
Boore, 0.25
30 km, 0.15
Campbell, 0.15
Mixed, 0.1
Sadigh, 0.25
25%, 0.3
50%, 0.2
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Design basis for future NPPs
PSHA
Spectral Acceleration, 'g'
1.00
UHS
0.10
0.01
0.0100
0.1000
1.0000
10.0000
Period, Sec
Uniform hazard spectra generated for Kalpakkam site,
(Damping = 5%).
Evolution of seismic design basis for Indian nuclear power plants
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Design basis for future NPPs
Beyond Design basis earthquake
(BDBEq)
• Work on BDBA gained momentum after occurrence of
accidents in three mile island and Chernobyl.
• New generation NPPs have provisions to address BDBA
scenarios
• What provisions should be kept for beyond design basis
earthquakes, BDBEq?
• Isuues are
– How to define BDBEq?
– Approach of management of BDBEq. Will it follow similar one
of BDBA?
– Regulatory guidelines
Evolution of seismic design basis for Indian nuclear power plants
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Design basis for future NPPs
Beyond Design basis earthquake
• Factors to be considered to deal BDBEq:
–
–
–
–
–
–
Definition of BDBEq
Evaluation of ground motion
Behavior of plant
Design/evaluation of plant and/or retrofitting
Operating practices
Seismic safety culture
Evolution of seismic design basis for Indian nuclear power plants
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Evolution of seismic design basis for Indian nuclear power plants
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Evolution of seismic design basis…
Present stage
1. PHWRs at Kaiga, Karnataka (KGS 1 to 4)
2. PHWRs at Rawtbhata near Kota, Rajasthan (RAPS – 3
to 6)
3. PHWR at Tarapur, Maharashtra (TAPP – 3&4)
4. Prototype fast breeder reactor at Kalpakkam,
Tamilnadu (PFBR)
5. Russian VVERs under construction at Kudankulam,
Tamilnadu, (KK-1&2)
Evolution of seismic design basis for Indian nuclear power plants
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Design basis for future NPPs
(BDBEq)
• Design basis earthquake, SSE, is generally derived for
an annual frequency of occurrence of 10-4. For BDBEq,
the frequency of occurrence would be smaller than SSE.
• Contribution of seismic induced CDF to total CDF play
an important role
Evolution of seismic design basis for Indian nuclear power plants
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