EVOLUTION OF SEISMIC DESIGN BASIS FOR INDIAN NUCLEAR POWER PLANTSPrabir 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 2 Atomic Energy Regulatory Board (AERB). Present stage 4. was formed in 1983. have undergone continuous evolution and improvement over the years. • Regulatory practices of seismic safety. • Three distinct stages from a regulatory perspective 1. Incipient regulatory stage 3.Introduction • NPP program commenced in India in 1969 with commissioning of TAPP-1&2 (BWR) at Tarapur. constructed commissioned and being operated. Pre-regulatory stage 2. • Subsequently NPPs (PHWR) were designed (indigenously). • Status of engineering of new generation power reactors – VVER 1000: finishing stage of construction – PFBR 500: Advanced stage of construction. New stage for future generation of NPP The regulatory authority. – PHWR 700: advanced design stage NPP locations in India Evolution of seismic design basis for Indian nuclear power plants 3 Evolution of seismic design basis • 60% of the land area in India is considered susceptible to earthquake shaking of intensity VII and above. Evolution of seismic design basis for Indian nuclear power plants 4 . Seismic loading was determined following IS875 1957.10 times the gravity load. Severe earthquakes of Kutch (1894) and Bihar (1934) were felt here. Tarapur.Evolution of seismic design basis… Pre-regulatory stage • This stage covers the NPPs designed / constructed / commissioned before the formation of AERB. – TAPS–1&2 (BWR).05g. All structures and mechanical components of the station and buildings be designed to resist a horizontal force equivalent to 0.4g. Kalpakkam The site falls in the In zone–I of IS1893 1966.05 times gravity load. Kota According to IS875 1057 the site was not prone to seismic activity as it fell in geologic zone – I.1g and remaining plant structures for 0. Evolution of seismic design basis for Indian nuclear power plants 5 Evolution of seismic design basis… Pre-regulatory stage – RAPS – 1&2 (PHWRs). – MAPS – 1&2 (PHWRs). and not prone to seismic activity. Considering this the NPP was designed for horizontal load up to 0. • NPPs of this stage are. • The seismic design basis for the reactors in this stage generally followed Indian Standard (IS) codes of industrial units. Evolution of seismic design basis for Indian nuclear power plants 6 . These earthquakes were estimated to generate horizontal acceleration of 0. 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. During this stage. Evolution of seismic design basis for Indian nuclear power plants 8 .2g for SSE and 0. • These two regulatory documents are the requirements and guidelines for derivation of DBGM parameters of present stage. Kakrapar Horizontal PGA: 0.Evolution of seismic design basis… Incipient regulatory stage • This stage covers NPP commissioned after formation of AERB but designed and constructed prior to AERB. and “Safety Guide on Seismic Studies and Derivation of Design Basis Ground Motion Parameters”. AERB/SG/S-11.1g for OBE Evolution of seismic design basis for Indian nuclear power plants 7 Evolution of seismic design basis… Present stage • AERB published “Code of Practice on Safety of Nuclear Power Plant Siting”.15g for OBE • KAPS – 1&2 (PHWR).3g for SSE and 0. • SSE or SL-2 level and OBE or SL-1 level were considered. Narora Horizontal PGA: 0. • NAPS – 1&2 (PHWR). – Active fault within 5km radius – Potential of liquefaction. • The regulation specifies rejection criteria. AERB/SC/S in 1990. DBGM parameters were derived following similar approach of IAEA / USNRC. slope instability. AERB siting code AERB/SC/S and safety guide on determination of DBGM parameters AERB/SG/S11 were prepared and published. ground failure/subsidence if there is no engineering solution. intermediate range (50km radius). Evolution of seismic design basis for Indian nuclear power plants 9 Evolution of seismic design basis… Present stage PGA values of different sites Evolution of seismic design basis for Indian nuclear power plants 10 . and MEQ data. local (5km radius) and site area (within plant boundary). • Guidelines are based on geological and seismological investigations in four scales.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. regional (300 km radius). This is in addition to the inherent rationality of the method... Evolution of seismic design basis for Indian nuclear power plants 12 . • Safety assessment of reactors are gradually becoming more PSA centric. – New information/data and advancement on earthquake engineering – Special requirements of new reactors. – Experience gained over the years on seismic safety of NPP. • 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. if any co-located. which invariably results in derivation of DBGM parameters of new reactors by probabilistic seismic hazard analysis (PSHA).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. Evolution of seismic design basis for Indian nuclear power plants 11 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. seismotectonic status and site-specific attenuation relation of the region are requirements for a robust PSHA • Peninsular India.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. Evolution of seismic design basis for Indian nuclear power plants 14 . challenges in application of PSHA due to – Sparse data. where most of the Indian nuclear facilities are located poses unique. • This calls for innovative approach to conduct PSHA of the sites in this region. – Lack of information on seismotectonic characteristics. Evolution of seismic design basis for Indian nuclear power plants 13 Design basis for future NPPs PSHA • Data/information on strong motion earthquake. and – Non-availability of regional specific attenuation relationships. This raised a probable issue how to deal with the beyond design basis earthquakes (BDBEq) in new reactors as well as the existing one. 25 Boore. Energy.25 25%. 0. 0.5 Mean+1σ Same ‘b’ value.75 Prop. 0.1 Mmax (max) 0.25 25%.25 20 km.5 30 km.125 GSHAP 0.5 Mmax (max) 0.25 Campbell. 0. 0. 0.25 20 km.5 Evolution of seismic design basis for Indian nuclear power plants 16 . 0.75 Mean+1σ 0.75 Mmax (min) 0. 0. 0. 0.3 Mean-1σ 0. 0. 0.125 Same ‘b’ value. 0. Energy. 0.1 Abramson. 0.1 Mean 0. 0.5 Atkinson. 0. 0.125 Actual data 0.1 0%.125 0. • PSHA aided by sensitivity study of input and technique to determine parameters along with logic tree could be an useful approach. 0.9 Mean 0. 0.1 10 km.2 Sadigh. 0. 0. 0. 0.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. 0.125 Prop.15 Mixed. Evolution of seismic design basis for Indian nuclear power plants 15 Design basis for future NPPs PSHA B Value B value-range Rate Apportionment Mmax Focal Depth Attenuation relation Atkinson.15 50%.2 Sadigh.3 Added dispersion 0%.25 Boore. 0.125 Mmax (mean) 0.5 30 km.25 Campbell.5 Mean-1σ 0.15 50%.75 Mmax (min) 0.125 10 km.125 Mmax (mean) 0. 0. 0.15 Mixed.5 Abramson. 'g' UHS 0. • New generation NPPs have provisions to address BDBA scenarios • What provisions should be kept for beyond design basis earthquakes.10 0. Will it follow similar one of BDBA? – Regulatory guidelines Evolution of seismic design basis for Indian nuclear power plants 18 .0100 0.00 Spectral Acceleration.Design basis for future NPPs PSHA 1.0000 10.01 0. (Damping = 5%). Sec 1.1000 Period. Evolution of seismic design basis for Indian nuclear power plants 17 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. BDBEq? • Isuues are – How to define BDBEq? – Approach of management of BDBEq.0000 Uniform hazard spectra generated for Kalpakkam site. 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 19 nk ha T u yo Evolution of seismic design basis for Indian nuclear power plants 20 . PHWRs at Kaiga. Maharashtra (TAPP – 3&4) 4. For BDBEq. is generally derived for an annual frequency of occurrence of 10-4. Tamilnadu (PFBR) 5. PHWRs at Rawtbhata near Kota. (KK-1&2) Evolution of seismic design basis for Indian nuclear power plants 21 Design basis for future NPPs (BDBEq) • Design basis earthquake. PHWR at Tarapur. Rajasthan (RAPS – 3 to 6) 3. SSE. • Contribution of seismic induced CDF to total CDF play an important role Evolution of seismic design basis for Indian nuclear power plants 22 . Karnataka (KGS 1 to 4) 2. Tamilnadu. Russian VVERs under construction at Kudankulam.Evolution of seismic design basis… Present stage 1. Prototype fast breeder reactor at Kalpakkam. the frequency of occurrence would be smaller than SSE.