Transcript IAEA Senior Regulators Meeting 18 March 2011

Nuclear administration after the nuclear
accident in Japan
March ,2013
Kenkichi HIROSE
Contents
1. Occurrence of the nuclear accident
2. Significant administrative points learned from
the accident at the Fukushima Dai-ichi Nuclear Power
Station
3. New framework of nuclear administration
4. Situation of nuclear liability
5. Reinforcement of safety of nuclear power plants
(reference ) Electricity production in Japan
1. Occurrence of the nuclear accident
2
Six BWR type nuclear power plants at Fukushima Dai-ichi NPS
started operation in the 1970s.
Unit 1
Unit 2
Unit 3
Unit 4
Unit 5
Unit 6
Electric output(MWe)
460
784
784
784
784
1100
Commercial operation
1971/3
1974/7
1976/3
1978/10
1978/4
1979/10
Reactor model
BWR3
BWR4
PCV model
Number of fuel
assemblies in the core
BWR5
Mark-1
400
548
Mark-2
548
548
548
764
Four BWR type nuclear power plants at Fukushima Dai-ni NPS
started operation in the 1980s.
Unit 1
Unit 2
Unit 3
Unit 4
Electric output(MWe)
1100
1100
1100
1100
Commercial operation
1982/4
1984/2
1985/6
1987/8
Reactor model
PCV model
Number of fuel
assemblies in the core
BWR5
Mark-2
764
Mark-2 Advance
764
764
764
3
Unit 1 ～5 at Fukushima Dai-ich NPS has flasktype primary containment vessel (PCV)
(source : TEPCO)
4
Before the earthquake and tsunami 3 plants were
under operation, and 3 plants were under periodic
inspection at the Fukushima Dai-ichi Nuclear
Power Station.
Under operation
• Unit 1
• Unit ２
• Unit ３
Under periodic inspection
• Unit 4 ( all the fuel were removed from the reactor to the spent fuel pool)
• Unit５
• Unit６
5
Epicenter of Tohoku District - off the Pacific Ocean Earthquake was
approximately 130km off the coast of Sanriku.
Occurrence: 14:46 March11, 2011
Mw(moment magnitude): 9.0
Epicenter: approximately 130km
off the coast of Sanriku
(at 38.10 degrees north latitude,
142.86 degrees east longitude
and 23.7km deep)
Map of JMA seismic intensities observed
during the main shock.
6
Loss of cooling capability caused core melt at Unit 1, Unit 2 and
Unit 3.
Shutdown of reactors and loss
of external power supply due
to earthquake
Start-up of emergency power
generators
All emergency diesel diesel generators
stopped except for one generator in
Unit6 due to tsunami
(11 emergency diesel power generator
stopped, and one generator(with air
cooling)survived.)
Loss of all AC power supply
except for Unit6
Core cooling system not using
AC power
(Unit1:IC(isolation condenser), Unit2 (RCIC(reactor
core isolation cooling system), Unit3: RCIC and HPCI
(high pressure core injection system)
Stop of core cooling system not
using AC power
Water injection from a fire
extinguishing line
(Unit1:pure water->sea water, Unit2: sea water
Unit3: pure water-> sea water)
(Unit 5 took power supply from Unit6 on 13 March).
During this time without cooling, the fuel
was exposed and core melt started,
generating hydrogen
7
Water was injected into the reactors via fire extinguishing
line using fire trucks as accident management.
(source : TEPCO)
Water was injected into the spent fuel pool at Unit 4
by concrete pump car.(source: TEPCO)
9
Hydrogen explosion occurred at the upper part of reactor
building at Unit 1, Unit 3 and Unit 4. (source : TEPCO)
Total view
Unit4
Unit1
Unit3
Unit2
10
Dose rates measured by monitoring car at the site
showed the high level of March 15.
11
Measurement of airborne concentration showed steady
decline of release from March to August 2011.
12
Radioactive materials were accumulated in the north-east
direction due to the winds of days of release of them.
(source : airborne monitoring by MEXT and DOE)
as of July 2,2011
13
Two stages of evacuation areas were set from March to April 2011.
(As of August 3, 2011)
14
2.Significant administrative points learned
from the accident at the Fukushima Dai-ichi
Nuclear Power Station
(1)Training responding to severe accidents should
be enhanced. (No.1)
 Conclusion
 Effective training to respond to accident restoration at
nuclear power plants and adequately work and
communicate with relevant organizations in the wake of
severe accidents was not sufficiently implemented up to
now. For example, it took time to establish
communication between the emergency office inside the
power station, the Nuclear Emergency Response
Headquarters and the Local Headquarters and also to
build a collaborative structure with the Self-Defense
Forces, the Police, Fire Authorities and other
organizations which played important roles in responding
to the accident. Adequate training could have prevented
these problems.
(1)Training responding to severe accidents should
be enhanced. (No.2)
 Lessons learned
 Reflecting on the above issues, we enhance training to
respond to severe accidents by promptly building a
structure for responding to accident restoration,
identifying situations within and outside power plants,
facilitating the gathering of human resources needed for
securing the safety of residents and collaborating
effectively with relevant organizations.
(2)Central control of emergency supplies and
equipment and setting up rescue teams should be
established. (No.1)
 Conclusion
 Logistic support has been provided diligently by those
responding to the accident and supporting affected
people with supplies and equipment gathered mainly at J
Village. However, because of the damage from the
earthquake and tsunami in the surrounding areas shortly
after the accident, we could not promptly or sufficiently
mobilize rescue teams to help provide emergency
supplies and equipment or support accident control
activities. This is why the on-site accident response did
not sufficiently function.
(2)Central control of emergency supplies and
equipment and setting up rescue teams should be
established. (No.2)
 Lessons learned
 Reflecting on the above issues, we introduce systems for
centrally controlling emergency supplies and equipment
and setting up rescue teams for operating such systems
in order to provide emergency support smoothly even
under harsh circumstances.
(3)Responses to combined emergencies of both
large-scale natural disasters and prolonged
nuclear accident needs to be reinforced. (No.1)
 Conclusion
 There was tremendous difficulty in communication and
telecommunications, mobilizing human resources, and
procuring supplies among other areas when addressing
the nuclear accident that coincided with a massive
natural disaster. As the nuclear accident has been
prolonged, some measures such as the evacuation of
residents, which was originally assumed to be a shortterm measure, have been forced to be extended.
(3)Responses to combined emergencies of both
large-scale natural disasters and prolonged
nuclear accident needs to be reinforced. (No.2)
 Lessons learned
 Reflecting on the above issues, we prepare the
structures and environments where appropriate
communication tools and devices and channels to
procure supplies and equipment be ensured in the case
of concurrent emergencies of both a massive natural
disaster and a prolonged nuclear accident. Also,
assuming a prolonged nuclear accident, we enhance
emergency response preparedness including effective
mobilization plans to gather human resources in various
fields who are involved with accident response and
support for affected persons.
(4)A clear division of labor between relevant
central and local organizations should be
established. (No.1)
 Conclusion
 Communication between local and central offices, as well as with
other organizations, was not achieved to a sufficient degree, due
to the lack of communication tools immediately after the accident
and also due to the fact that the roles and responsibilities of each
side were not clearly defined. Specifically, responsibility and
authority were not clearly defined in the relationship between the
NERHQs Nuclear Emergency Response Headquarters and Local
NERHQs Headquarters, between the Government and TEPCO,
between the Head Office of TEPCO and the NPS on site, or
among the relevant organizations in the Government. Especially,
communication was not sufficient between the government and
the main office of TEPCO as the accident initially began to
unfold.
(4)A clear division of labor between relevant
central and local organizations should be
established. (No.2)
Lessons learned
 Reflecting on the above issues, we review and
define roles and responsibilities of relevant
organizations including the NERHQs, clearly
specify roles, responsibilities and tools for
communication while also improving institutional
mechanisms.
“Nuclear Emergency Response Headquarters” was responsible
for nuclear emergency including the instruction of evacuation.
(Law Cabinet Decisions)
Nuclear Emergency
Response
Headquarters
Chief:Prime Minister
Cabinet Office
Local Nuclear Emergency Response
HQs (Inside Prefectural Office of Fukushima)
Government - TEPCO Integrated
Response Office
(including assistance from overseas)
Team in charge of
Assisting the
Lives of Victims
around the Nuclear
Power Plant
Cabinet Office
Liaison Meetings
among relevant
ministries and agencies
Team in charge of
Responding to the
Economic Impact caused
by the Nuclear Power
Station Incident
(review meetings of ministerial
Cabinet
Secretariat
level
if necessary)
24
Off-site center near the site was given up due to high-level
radiation. (source : Agency of Natural Resources and Energy)
25
(5)Communication relevant to the accident should
be enhanced. (No.1)
 Conclusion
 Communication to residents in the surrounding area
was difficult because communication tools were
damaged by the large-scale earthquake. The
subsequent information to residents in the surrounding
area and local governments was not always provided
in a timely manner. The impact of radioactive materials
on health and the radiological protection guidelines of
the ICRP, which are the most important information for
residents in the surrounding area and others, were not
sufficiently explained. Japan focused mainly on
making accurate facts publicly available to its citizens
and has not sufficiently presented future outlooks on
risk factors, which sometimes gave rise to concerns
about future prospects.
(5)Communication relevant to the accident should
be enhanced. (No.2)
Lessons learned
 Reflecting on the above issues, we will reinforce
the adequate provision of information on the
accident status and response, along with
appropriate explanations of the effects of
radiation to the residents in the vicinity. Also, we
keep in mind having the future outlook on risk
factors included in the information delivered
while incidents are still ongoing.
(6)Clear definition of widespread evacuation areas
and radiological protection guidelines in nuclear
emergency should be made. (No.1)
 Conclusion
 Immediately after the accident, an Evacuation Area and Inhouse Evacuation Area were established, and cooperation of
residents in the vicinity, local governments, police and
relevant organizations facilitated the fast implementation of
evacuation and “stay-in-house” instruction. As the accident
became prolonged, the residents had to be evacuated or stay
within their houses for long periods. Subsequently, however, it
was decided that guidelines of the ICRP and IAEA, which
have not been used before the accident, would be used when
establishing Deliberate Evacuation Area and Emergency
Evacuation Prepared Area. The size of the protected area
defined after the accident was considerably larger than a 8 to
10km radius from the NPS, which had been defined as the
area where focused protection measures should be taken.
(6)Clear definition of widespread evacuation areas
and radiological protection guidelines in nuclear
emergency should be made. (No.2)
 Lessons learned
 Based on the experiences gained from the accident, the
Japanese Government makes much greater efforts to
clearly define evacuation areas and guidelines for
radiological protection in nuclear emergencies.
International criteria for the radiation protection was introduce
to respond to the situation of accident continuation.
30
20 mSv/year was introduced for accident continuation.
Standard for the radiation dose
(1)Integrated radiation dose in the normal
situation.
• Public radiation exposure dose limit.
1 mSv/year
Authority
• Notice of Ministry of Economy, Trade and Industry
• “Public notices which provides the dose limit based on the
provisions of the rules about establishment operation etc.
• Of the practical use nuclear reactors for electricity generation”
Article 3:radiation dose out of the peripheral surveillance area.
• ICRP recommendation Publication 60 (1990):Dose limit of the
public radiation exposure.
(2)Integrated dose at the time of the
accident
(a) Standard for avoiding large radiation
exposure in the early stage of the accident
outbreak
10mSv (indoor sheltering)
50m Sv (evacuation)
• The guidance of the Nuclear Safety Commission
• “About the disaster prevention measures such as nuclear energy
facilities”
• IAEA safety requirements GS-R-2 “Preparedness and Response for
a Nuclear or Radiological Emergency” (2002)
(b)Standard of the radiation
Protection in the emergency
situation(accident continuation)
20-100 mSv
• ICRP recommendation Publication 103 (2007)
• IAEA safety requirements GSG2 “Preparedness and Response for
a Nuclear or Radiological Emergency” (2011)
(C)The radiation protection
Standard in the situation where the pollution
after the accident has come to a settlement
should be taken into the consideration
1-20 mSv/year
• ICRP recommendation Publication 103 (2007)
• Reference level for protecting the public in the situation where
the pollution after the accident has come to a settlement should
be taken into the consideration (existing situation)
ICRP: International Commission on Radiological Protection
31
(7) Safety regulatory bodies should be reinforced.
(No.1)
 Conclusion
 Governmental organizations have different responsibilities for
securing nuclear safety. For example, NISA of METI is
responsible for safety regulation as a primary regulatory body,
while the Nuclear Safety Commission of the Cabinet Office is
responsible for regulation monitoring of the primary
governmental body, and relevant local governments and
ministries are in charge of emergency environmental
monitoring. This is why it was not clear where the primary
responsibility lies in ensuring citizens’ safety in an emergency.
Also, we cannot deny that the existing organizations and
structures hindered the mobilization of capabilities in promptly
responding to such a large-scale nuclear accident.
(7) Safety regulatory bodies should be reinforced.
(No.2)
 Conclusion
 Reflecting on the above issues, the Japanese
Government separates NISA from METI and start to
review implementing frameworks, including the NSC and
relevant ministries, for the administration of nuclear
safety regulations and for environmental monitoring.
(8) Legal structures, criteria and guidelines should
be established and reinforced. (No.1)
 Conclusion
 Reflecting on this accident, various challenges have
been identified regarding the establishment and
reinforcement of legal structures on nuclear safety and
nuclear emergency preparedness and response, and
related criteria and guidelines. Also, based on the
experiences of this nuclear accident, many issues will be
identified as ones to be reflected in the standards and
guidelines of the IAEA.
(8) Legal structures, criteria and guidelines should
be established and reinforced. (No.2)
 Lessons learned
 Therefore, the Japanese Government reviews and improve
the legal structures governing nuclear safety and nuclear
emergency preparedness and response, along with related
criteria and guidelines. During this process, it reevaluates
measures taken against age-related degradation of existing
facilities, from the viewpoint of structural reliability as well as
the necessity of responding to new knowledge and expertise,
including progress in system concepts. Also, the Japanese
Government clarifies technical requirements based on new
laws and regulations or on new findings and knowledge for
facilities that have already been approved and licensed-- in
other words, it clarifies the status of retrofitting in the context
of the legal and regulatory framework. The Japanese
Government makes every effort to contribute to improving
safety standards and guidelines of the IAEA by providing
related data.
(9)Human resources for nuclear safety and nuclear
emergency preparedness and responses should
be developed. (No.1)
 Conclusion
 All the experts on severe accidents, nuclear safety,
nuclear emergency preparedness and response, risk
management and radiation medicine should get together
to address such an accident by making use of the latest
and best knowledge and experience. Also, it is extremely
important to develop human resources in the fields of
nuclear safety and nuclear emergency preparedness
and response in order to ensure mid- and long-term
efforts on nuclear safety as well as to bring restoration to
the current accident.
(9)Human resources for nuclear safety and nuclear
emergency preparedness and responses should
be developed. (No.2)
 Lessons learned
 Reflecting on the above-mentioned issues, the Japanese
Government enhances human resource development
within the activities of nuclear operators and regulatory
organizations along with focusing on nuclear safety
education, nuclear emergency preparedness and
response, crisis management and radiation medicine at
educational organizations.
(10) A safety culture should be thoroughly
instilled. (No.1)
 Conclusion
 All those involved with nuclear energy should be
equipped with a safety culture. “Nuclear safety culture” is
stated as, “A safety culture that governs the attitudes and
behavior in relation to safety of all organizations and
individuals concerned must be integrated in the
management system” (IAEA, Fundamental Safety
Principles, SF-1, 3.13). Learning this message and
putting it into practice is the starting point, the duty and
the responsibility of those who are involved with nuclear
energy. Without a safety culture, there will be no
continual improvement of nuclear safety.
(10) A safety culture should be thoroughly
instilled. (No.2)
 Lessons learned
 Reflecting on this viewpoint, Japan establishes a safety
culture by going back to the basics, namely that pursuing
defenses in depth is essential for ensuring nuclear
safety, by constantly learning professional knowledge on
safety, and by maintaining an attitude of trying to identify
weaknesses as well as room for improvement in the area
of safety.
3.New framework of
nuclear administration
3.1 Establishment of new regulatory
organization
-New act “Act for Establishment of the
Nuclear Regulation Authority”-
41
(1) Concept of protection of the environment is
introduced for the first time into the purpose of the Act
for Establishment of the Nuclear Regulation Authority.
 In order to solve the problem caused by the removal of the
problems of verticality of government organization with
respect to the policy on the use of nuclear power, the
administrative organization of the one responsible for the
function of both the regulation and promotion of the use of
nuclear energy, as well as always the occurrence of accidents
in the use of nuclear power implementation you, or to develop
the necessary measures in order to ensure safety in the use
of nuclear power in light of international standards that
standing recognition assumed that they must do one's utmost
best and to prevent it, has been established the nuclear
Regulation Authority as well as responsible to a central office
to be exercised ex officio chairman and members of the
Commission that is independent fairness neutral based on
expertise, people's lives, property protection and health have ,
with the aim of contributing to the security of our country, as
well as the preservation of the environment.
(reference) IAEA Safety Fundamentals
[Principle7:Protection of present and future
generations]
 People and the environment, present and future,
must be protected against radiation risks.
(2) The NRA was established ensuring independence.
 As a highly independent committee, the NRA was
established as an external organ of the Ministry of the
Environment.
 Thorough separation of regulation and use, department
of nuclear safety regulations of the Nuclear and
Industrial Safety Agency was separated from the Ministry
of Economy, Trade and Industry and was transferred to
the NRA.
 The NRA establishes its own rule of Standards for
nuclear safety regulations, etc.
 For ensuring nuclear safety, the NRA has the right of
recommendations to the heads of the relevant
administrative organs.
(3) The NRA has the Nuclear Regulatory Agency as
the secretariat.
 The NRA consists of Chairman and four
members of the Commission.
 As the secretariat of the NRA, the Nuclear
Regulatory Agency was established.
(4) All the nuclear safety regulations are
centralized into the NRA.
 Regulation of Nuclear ship that the Ministry of Land,
Infrastructure and Transport was responsible, regulation
of nuclear power reactors that the Nuclear and Industrial
Safety Agency of Ministry of Economy, Trade and
Industry was responsible, regulation of research reactors
and regulation of the use of nuclear fuel material that the
Ministry of Education was responsible are centralized
into the regulation of the NRA. Thus all the nuclear
safety regulations are centralized into the NRA.
(5) All kinds of nuclear regulations are centralized into
the NRA.
 All kinds of nuclear regulations are centralized
into the NRA.
• Nuclear security
• Nuclear non-proliferation safeguards
• Radiation monitoring
• Regulation of radioisotope
(6) The Nuclear Safety Commission was abolished
when the new regulatory system was built.
 The Nuclear Safety Commission was
responsible for the the so-called “double-check
function.
 The Nuclear Safety Commission was abolished
and the necessary functions was integrated into
the NRA.
 The NRA formulates its own standards and
guidelines which are required for nuclear safety
regulations.
3.2 Reinforcement of safety regulation
-Revision of the Nuclear Reactor Regulation
Law-
49
(1) Requirement of severe accident management
was legalized.
 Before the Fukushima accident, severe accident
management is required on a operators’
voluntary basis.
 Requirement of severe accident management
was legalized after the accident.
Accident management were utilized to mitigate the
condition of severe accident.
Items
Contents
Alternative coolant
injection
• Lines via condensate water makeup systems from
the condensate storage tanks as the water sources
• Lines via fire extinguishing systems and
condensate water makeup systems from the filtrate
tanks as the water sources
PCV vent facilities
• PCV vent facilities were installed to bypass the
standby gas treatment system so that they can
vent the PCV when the pressure is high.
Power interchange
facilities
• Power interchange facilities have been installed
such that the power supply of the alternating
current source for power machinery (6.9kV) and
the low voltage alternating current source (480V)
can be interchanged between adjacent reactor
facilities (between Units 1 and 2, between units 3
and 4, and between Unit 5 and 6).
51
(2) The revised law requires the back fit system for
existing nuclear facilities.
 The revised law incorporates the latest findings on
technical standards and introduces the system requiring
compliance with the new standards for facilities also
already obtained permission (back fit system).
 In order to facilitate the rapid deployment of facilities
related to nuclear power reactor facilities, the revised law
introduces the system of type approval of equipment to
eliminate duplication of examination licensing to
improved safety, etc.
(3) Operational limits of 40 years for nuclear power
plants are introduced.
 The revised law defines 40 years as the time to drive a
power reactor from the date that they pass the inspection
before use.
 However, the revised law gives a chance of the approval
of the extension to the extent of the period specified by a
Cabinet Order not exceeding 20 years, and only once
under the condition that upon expiration of such period, a
operator meets the standards established by the rules of
the NRC to ensure the safety based on the situation of
deterioration such as reactor caused due to the
operation of a long period of time.
(4) Regulatory measures to ensure safety for
facility which disasters occurred is introduced.
 The revised law requires the operator to create
implementation plans and to take measures
along a line with that plan, when it is particularly
necessary to manage the facility from the point
of view of physical protection or prevention of
disasters further at the facility which nuclear
disaster occurs, after operators have taken
emergency measures, and when the authorities
specifies the nuclear facility as special nuclear
facility.
3.3 Reinforcement of emergency
preparedness
55
(1) Nuclear emergency preparedness conference
is established in the Cabinet.
 Nuclear emergency preparedness conference is
established in the Cabinet, under close collaboration with
relevant organizations.
 The conference promotes the implementation of
measures to ensure the overall efforts of the government
in case of nuclear accidents and to promotes the
implementation of measures based on the nuclear
emergency response guidelines.
 The conference promotes the implementation of
comprehensive measures to long-term efforts by a
number of interested parties in the case of nuclear
accident occurred. (Amendment of the Atomic Energy
Basic Law)
(2) Disaster drills of nuclear operators are
strengthened.
 The NRA is able to check the status of the
implementation of a nuclear operators’
emergency drills, to issue an order of necessary
improvement and to give penalties for any
violations.
(3) Function of “Nuclear Emergency Response
Headquarters” is reinforces.
 Prime Minister is designated as the head of the
Nuclear Emergency Response
Headquarters(NERH), Chief Cabinet Secretary,
Minister of the Environment and chairman of the
NRC are designated as deputy head of the
NERH, and all the members the cabinet are
designated as the members of the NERH ,thus
reinforcing the function of the NERH.
4. Situation of nuclear liability
Basic legal framework of nuclear liability was made
in 1961.
 Basic legal framework of nuclear liability was
made in 1961.
(1)"Law on Compensation for Nuclear Damage"
• general framework
(2) "Act on the indemnity agreement for
compensation of nuclear damage"
• Indemnification agreements between the
operators and the central government

•

•
•
Supplementary legal framework of nuclear liability was
established due to large-scale damage caused by the
Fukushima nuclear accident.
(1)”Agency of Support for Nuclear Liability” was enacted
on July 2011.
All the electric utilities join this agency to support
payment of nuclear liability by TEPCO. And the central
government gives financial support to this agency.
(2)”Act on Urgent Measures for Nuclear Damage related
to the Accident of year Heisei 23”
The Government makes a temporary payment in
advance to the person to whom the specific nuclear
damage was made in order to support the person.
The amount of the temporary payment shall be in an
amount not less than 1/2 of the estimated amount of a
specific nuclear damage.
61
“Disputes Committee on Nuclear Liability” showed basic
guideline for implementation of nuclear liability.
 Eligible for compensation is as follows;
• Residents in the areas related to evacuation
• Agriculture, forestry and fishery businesses
• Food industry
• Tourist agent
• Manufacturing companies
• Service industry
• Others
 Compensation covers not only direct damage
but also indirect damage and harmful rumor.
62
5. Reinforcement of safety of nuclear power
plants
Countermeasures against tsunami were required to strengthen safety of BWRs.
Fire Engine
Power Supply Car
Fuel Pool
Reactor Containment
DC Power Supply
(Battery)
Emergency
Diesel Power
Generator
External Power Supply
Reactor
Pressure Vessel
Alternative Water Injection
Reactor Core
Isolation
Cooling System
Emergency Reactor
Cooling System
Pressure Suppression Chamber
Cooling Pump
Ventilation
Stack
Sea Water Pump
Pressure Suppression Chamber
Pressure Suppression Chamber
電源車
64 64
Countermeasures against tsunami were required to strengthen safety of PWRs.
Ｍ
Emergency Diesel
Power Generator
Main
Water
Supply
Electric Pump
For Fire
Extinguisher
water
Fresh
Water
Tank
External
Power
Supply
Turbine Driven
Auxiliary Feed Water
Pump
To Fire
Extinguisher
Water System
Diesel
Pump
for Fire
Extinguisher
Reactor Vessel
Condensate tank
(6) Connection of Power Supply Car
Reactor Containment
Containment Spray
Ｍ
Ｍ
Pressure
Accumulat
or Tank
Contro
l Rod
Containment
Spray Pump
Main Steam
Reactor
Auxiliary Building
Turbine Driven Auxiliary Feed Water Pump
High Pressure
Injection Pump
Residual Heat
Removal Pump
Diesel Generator
To Steam
Turbine
Steam for
Drive
Main Water Supply
Ｍ
Ｍ
Injection of
Boric Acid
Water
(7) Water Injection to Spent Fuel Pit
Reactor
Vessel
Primary
Coolant
Pump
Containment
Sump
Spent Fuel
Pit
Ｍ
Sea Water Pump
To
Sea
Reactor Building
Condensate
Tank
Reactor
Containment
Auxiliary Electric Water
Supply Pump
Fire
Hydrant
Ｍ Component Cooling Water
C Pump
Ｍ
Steam
Generator
Ｍ
Fire Engine,
etc.
Water Supply
Pressure
Accumulator Tank
M
External Power Supply
(3) & (4) Injection of Boric Acid Water from
Pressure Accumulator tank, shut-off of the valve
Main Steam
Steam Generator
Ｍ
Water
Tank
for
Refueling
(2) & (5) Water supply / cooling of steam
generator, supply water to condensate tank
Loss of Safety Pumps function
(1) Loss of External Power Supply
Water Supply
Supply water to make
up for lowered water
level
boundar
y
Fire Engine
Cooler
Spent
Fuel Pit
(in
auxiliary
building)
Cooling Pump (2 units)
65
Comprehensive safety assessment (stress test) are required to
implement for other NPS.
 Comprehensive safety assessments are conducted
based on new procedures and rules, with reference to
the stress tests introduced in Europe, for enhancing the
safety of nuclear power stations and ensuring safety and
reliance for citizens and residents.
 Preliminary assessment: The nuclear power stations,
that are under shutdown due to regular inspections and
are prepared for start-up, are successively assessed on
the safety margins of their facilities and equipment
essential for safety against beyond-design-basis events.
 Secondary assessment: Taking into account the
implementation status of stress tests in Europe and what
have been reviewed by the Investigation Committee on
the Accidents at the Fukushima NPS, all nuclear power
stations including the stations under operation and those
evaluated in the preliminary assessment are assessed
on the comprehensive safety margins.
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In the stress test safety margins for structural integrity of
components and piping are evaluated.
Material strength confirmed by testing
Elastic range
Allowable limits of
design standards
Stress assumed to be exerted
in design basis earthquakes
(calculated value)
Secondary
Safety factors
Preliminary
Total margin
Material strength defined in the
standard
Stress-strain curve
Tension
Irreversible deformation
(plastic deformation)
Fracture
×
Large load
(fracture)
Load (small deformation)
Safety margins
Values prescribed in the NSC Regulatory Guides and technical standards are
used as allowable limits in preliminary assessment. Values exceeding allowable
limits are applicable if it is technically verified in the preliminary assessment that
the structure’s integrity and functions are maintained. Factual assessment is
conducted during secondary assessment to obtain values that cause the loss of
structural integrity and functions.
Load removal
(no deformation)
Deformation
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(reference )
Electricity production in Japan
Power generation capacity in Japan
(from the bottom: nuclear, thermal (coal), hydro, thermal(natural gas),
thermal(petroleum), pumped-storage, new energy)
(Unit: 10000 kW)
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Power generation in Japan
(from the bottom: nuclear, thermal (coal), hydro, thermal(natural gas),
thermal(petroleum), pumped-storage, new energy)
(Unit: 100 million kWh)
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Thank you for your attention.