New Regulatory Requirements in Japan Tomoho Yamada Secretariat of Nuclear Regulatory Authority June 24-28 35th Meeting of the Nuclear Safety Standards Committee

<Countermeasures> <Countermeasures> Progression of Fukushima-Daiichi Accident and Countermeasures Earthquake <Countermeasures> Reactor　shutdown Prevention of prolonged loss of off-site power <Countermeasures> Enhancement of robustness against earthquake and tsunami Emergency DGs / core cooling systems started Design basis height: 5.7m Inundation height: 15.5m Tsunami Enhancement of plant monitoring and control functions Prevention of core damage Enhancement of emergency power supply and core cooling Loss of communication & instrumentation functions Prevention of containment failure Core damage Suppression of release and dispersion of radioactive materials Hydrogen explosion in reactor building ※DG： Diesel Generator Release of large amount of radioactive materials to environment

Basic Policy of New Regulatory Requirements Thorough Application of Defense-in-Depth Concept Prepare multiple effective measures (multi-layered protective measures) and, for each layer, achieve the objective only in that layer regardless of the measures in the other layers. Assume the preceding layer be breached (denial of preceding layer) . Elimination of Common Cause Failure Fire protection Reinforcement of SSCs important to safety (elimination of shared use of passive components, if relied on for a long time). More Stringent Assessment and Enhanced Protective Measures Against Extreme Natural Hazards More stringent approach for assessment of earthquake and tsunami, introduction of measures against tsunami inundation. Due consideration of diversity and independence (shift of emphasis from “redundancy centered”). Performance based Requiremants

Structure of New Regulatory Requirements （Measures beyond DBA） NEW Suppression of release of Radioactive Materials Measures against Intentional Aircraft Crash Prevention of Containment Failure Prevention of Core Damage （Multiple Failures） ＜Present＞ Natural Phenomena Fire Natural Phenomena Reinforced Fire Reliability Reliability Reliability of Power Supply Reliability of Power Supply Ultimate Heat Sink Ultimate Heat Sink Function of other SCCs Reinforced Function of other SCCs Seismic/Tsunami Resistance Seismic/Tsunami Resistance

Strengthening the Requirements 1) Comprehensive consideration of natural hazards such as volcano, tornado and forest fire in addition to earthquake and tsunami, etc. 2) Reinforce fire protection measures 3) Enhance reliability of SSCs important to safety (Redundancy of passive component such as piping, if relied on for a long time) 4) Reinforce the reliability of off-site power supply (connect to different substations by multiple transmission lines) 5) Protect systems for Ultimate Heat Sink (Protection of seawater pumps, etc.) 6) Legally require measures against Severe Accident and Terrorism　

Reinforcement of Off-Site Power Supply (connection to different substations through multiple lines) Sub Station C Sub Station A Sub Station B Nuclear Power Station Sub Station D Sub Station E Sub Station A Sub Station B Nuclear Power Station

Protection of Systems for Ultimate Heat Sink (Protection of seawater pumps, etc.) 　 seawater pumps wall

Basic Policy of New Requirements Against Severe Accident and Terrorism 1)　Preparation of multi-layered protective measures for “prevention of core damage”, “maintaining containment integrity”, “controlled release by venting”, and “suppression of release / dispersion of radioactive materials” 2) 　Use of mobile equipment as a base and further enhancement of reliability by combined use with permanently installed systems / equipment as “Continuous improvement” Enhancement of protective measures for Spent Fuel Pool (Water level measurement, Alternative water supply, Spray) 4) 　Enhancement of command communication and instrumentation (Reinforced seismic-resistance of on-site emergency response center, improved reliability / durability of communication system, enhanced instrumentation including SFP ) 5) 　Introduction of “Specialized Safety Facility” against intentional aircraft crash

Requirements to Prevent Core Damage Measures to Prevent Core Damage assuming situations more severe than Design Basis Accidents Accidents including the followings: 1) ATWS 2) Loss of reactor cooling function (at high pressure) 3) Loss of reactor depressurization function 4) Loss of reactor cooling function (at low pressure) 5) Loss of UHS System 6) Loss of support function (makeup water, power supply) 7) Others identified by IPE and IPEEE

Measures against Loss of UHS System Example: Alterative UHS System PWR Through main steam relief valves to the atmosphere Sea water injection to RHR-S BWR Filtered venting system Mobile RHR reactor building sea pump RHR

Measures against Loss of Electric Power (Station Blackout) Example: ･Batteries(8hours without load shedding + 16hours with load shedding) ･Alternative onsite AC power for 7 days ･External Support by the 6th day hours 8 24 144 168 Batteries Onsite AC External Support Alternative onsite AC power (Power Vehicle)

Requirements to Prevent Containment Failure Measures to Prevent Containment Failure after Core Damage Cooling and depressurization of CV, reduction of release of radioactive materials (e.g., CV spray ） Heat removal from CV and depressurization of CV 　　 （e.g., Filtered venting） Cooling of molten core at the bottom of CV and inside RPV (e.g., water injection) Prevention of Direct Containment Heating (DHC) (e.g., depressurization of RPV) Prevention of hydrogen explosion inside CV (e.g., igniter)

Water injection system into lower part of CV CV spray to cool and depressurize CV, and reduce release of radioactive materials Filtered venting to reduce the pressure and temperature inside CV in addition to reducing radioactive materials while exhausting Water injection system into lower part of CV to prevent CV failure due to molten core (mobile pumps, hoses etc.) Alternative mobile equipment Reactor building Containment RPV Stack Permanently installed system Filter Filtered Venting system

Measures to Prevent Reactor Building Damage, Fuel Damage in SFP, etc. Other Measures Measures to Prevent Reactor Building Damage, Fuel Damage in SFP, etc. 1) Prevention of hydrogen explosion at reactor building etc. 2) Cooling of SFP 3) Prevention of fuel damage during shutdown 4) Emergency Response Center

Prevention of fuel damage in SFP Water spray (mobile) Mobile alternative water injection equipment Failure of makeup water or small leakage Loss of cooling or water injection function of spent fuel storage pool, or small leak of pool water. Requirements Prepare facilities and procedures for cooling, shielding and preventing criticality of fuels in the SFP. Example of measures Alternative mobile water injection system Spent fuel pool Reactor well Heat exchanger Fuel pool cooling and cleanup system Skimmer surge tank Large leakage Loss of water due to large break of SFP. Requirements Prepare facilities and procedures to mitigate the fuel damage and to prevent criticality Example of measures Mobile Water spray system Monitoring / instrumentation Measurement of level and temperature of pool water, and dose rate around the SFP These measuring instruments are connected to alternative AC power sources. Monitoring water level by video cameras

Measures against Aircraft Impact, etc. “Specialized Safety Facility” to mitigate the release of radioactive materials after core damage caused by intentional aircraft crash Mountain side Specialized Safety Facility Emergency control room Filtered venting Reactor building Power supply CV spray pump CV spray CV Water source Molten core cooling pump Water injection into reactor Core For example, 100 m Water injection into lower part of CV Filter sea * System configuration is an example. For BWR, one filtered venting for prevention of containment failure (p.10) and another filtered venting of Specialized Safety Facility are acceptable solution.

Measures for suppressing release / dispersion of radioactive materials Assuming CV failure, require outdoor water spraying equipment, etc. (Suppression of dispersion of radioactive materials by water spraying to reactor building) Water-spraying by a large capacity water cannon system (Pictures cited) Upper: Fire fighting white paper, 2005 edition, http://www.fdma.go.jp/html/hakusho/h17/h17/html/17705k10.html Lower: Fire fighting white paper, 2011 edition, http://www.fdma.go.jp/html/hakusho/h23/h23/html/2-1-3b-3_2.html

Enhanced Measures for Earthquake / Tsunami Stringent Evaluation Method on Earthquake and Tsunami; Particularly Enhanced Tsunami Measures More stringent Standards on Tsunami Define “Design Basis Tsunami” that exceeds the largest in the historical records and require to take protective measures such as breakwater wall based on the design basis tsunami Enlarged Application of Higher Seismic Resistance SSCs for tsunami protective measures are classified as Class S equivalent to RPV etc. of seismic design importance classification ＜Example of tsunami measures（multiple protective measures）＞ ○ Breakwater Wall （prevent inundation to the site） ○ Tsunami Gate　 　（prevent water penetration into the building）

More stringent criteria for active faults Active faults with activities later than the Late Pleistocene (later than 120,000-130,000 years ago) be considered for seismic design Activities in the Middle Pleistocene (later than 400,000 years ago) be further investigated if needed More stringent criteria for active faults More precise methods to define design basis seismic ground motion 3D observation of underground structure of the site Clarification of requirements for “displacement and deformation” in addition to the seismic ground motion Class S buildings should not be constructed on the exposure of active faults Example of geophysical exploration generate shaking at multiple spots by the movement Vibrator The underground structure is explored by generating a vibration by vibrator and analyzing the signals received in a borehole. Vibration Vibration Boring Vibration Receiver