1. Role of PSA in Ensuring Safety of Future NPPs J K Jena Senior Consultant Nuclear Risk Management Lloyd’s Register Consulting Date 06 th September, 2013

2. Agenda Probabilistic Safety Assessment (PSA) Focus of Advanced Reactor Technologies Fukushima Accident: Stretching the Extra Mile Safeguarding against Beyond Design Basis (BDB) Accidents Increasing Role of PSA

3. Probabilistic Safety Assessment (PSA) Systematic mathematical tool to quantify risk arising from a NPP Compliments traditional deterministic analysis Provides insights into safety loop-holes in the NPP design and operation Brings up needed risk reduction measures to minimize risk Aids Risk Informed Decision Making PSA is performed in 03 levels to predict best estimate of –Core Damage Frequency (CDF) in Level-I (Efficacy of design and operational safety): –Large Early Release Frequency (LERF) in Level-II (Efficacy of containment and allied systems): –Death / yr in Level-III (Efficacy of offsite accident management system): Lesser are the risk figures safer is the technology

4. Focus of Advanced Reactor Technologies To reduce RISK, NPP design and operational safety has primarily focused on –High reliable material and instrumentation Large LOCA frequency reduction by adopting LBB concept in fabrication of the primary system piping. Reduction of ATWS sequence contribution to CDF by using high reliable C&I system –Passive core and containment cooling (Phenomena based) PCCS instead of ECCS in AP1000, APR1400, EPR, ESBWR –Minimum post initiating event operator intervention 24hrs no operator intervention following a DBA in AP1000 –Post core melt scenario handling EPR, ESBWR [Basemat Internal Melt Arrest and Coolability Device (BiMAC)], EU-ABWR

5. Fukushima Accident: Stretching the Extra Mile Advanced engineering design and material selection in the Generation III/III+ reactors has brought down CDF and LERF to a significantly low level(CDF ≈ 10 -07 /yr). Fukushima accident has brought up a big question: How to safeguard the reactor against Beyond Design Basis (BDB) accident or multiple natural disaster?

6. Safeguarding against Beyond Design Basis (BDB) Accidents Safeguarding People in BDB Accident SBO Handling Ultimate Heat Sink for RPV Inside Containment Combustible Gas Management Spent Fuel Pool Cooling SAMG and EPP

7. Increasing Role of PSA Objective & Scope Making full scope PSA Level-1,2 & 3 mandatory Corroborating PSA results in all decision making process Comparing the new engineered systems introduced as safeguard from BDB accidents Inclusion of Special Events All external event modelling with LOOP/SBO Multiple failures as Initiating Event Site safety assessment Modelling Details Increasing the mission time beyond 72 hrs Considering Common Cause Failure (CCF) of safety systems upto sensor level. Detailed modelling of Containment Safety Systems

8. For more information, please contact: J K Jena Sr. Consultant, Nuclear Risk Management Lloyd’s Register Consulting T +91-22-4192 4010 M +91-981 977 0830 E Jajati.Keshari.Jena@lr.org W www.lr.org/consulting W www.riskspectrum.com Lloyd's Register and Lloyd’s Register Consulting are trading names of the Lloyd's Register Group Limited and its subsidiaries. For further details please see our web site www.lr.org/entities