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

2. <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

3. 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

4. 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

5. 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　

6. 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

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

8. 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

9. 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

10. 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

11. 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)

12. 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)

13. 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

14. 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

15. 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

16. 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.

17. 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, Lower: Fire fighting white paper, 2011 edition,

18. 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）

19. More stringent criteria for active faults
Active faults with activities later than the Late Pleistocene (later than 120, ,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