Provisional Translation(Feb.7,2013 Rev.0）

February 6, 2013

New Safety Standards (SA) Outline (Draft)

For Public Comment0February 6, 2013

New Safety Standards (SA) Outline (Draft)

Table of Contents
Foreword
1. Definitions
2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(1) Common Requirements① Requirements for alternate equipment② Requirements for portable alternate equipment③ Requirements for recovery work
④ Requirements for permanent alternate equipment⑤ Miscellaneous Requirements(2) Preparation of procedures, implementation of drills, and development of emergency
response organizational system(3) Countermeasures for reactor shutdown(4) Countermeasures for cooling reactor at high pressure(5) Countermeasures for depressurization of reactor coolant pressure boundaries(6) Countermeasures for cooling reactor at low pressure(7) Countermeasures for securing an ultimate heat sink after an accident(8) Countermeasures for cooling, depressurization and radioactive material mitigation ofcontainment vessel (Containment vessel spray)(9) Countermeasures for heat removal and depressurization of containment vessel(10) Countermeasures for cooling melted core fallen to the bottom of the containment vessel(11) Countermeasures against hydrogen explosions inside the containment vessel(12) Countermeasures against hydrogen explosions inside the reactor building, etc.
(13) Countermeasures for cooling, shielding and ensuring the sub-criticality of spent fuelstorage pools(14) Countermeasures for securing make-up water and water sources1(15) Countermeasures for securing electricity sources(16) Control room(17) Emergency response facilities(18) Instrumentation facilities(19) Radiation monitoring facilities(20) Communications equipment(21) Countermeasures for preventing off-site radioactive release
3. Accident Management for External Events beyond Design Basis(1) Accident management with portable equipment, etc.
(2) Specific safety facilities
4. Evaluation of the Effectiveness of Countermeasures against Severe Accidents(1) Evaluation of the effectiveness of countermeasures against severe core damage andcontainment vessel failure(2) Evaluation of the effectiveness of countermeasures against severe fuel damage in spent fuelstorage pools(3) Evaluation of the effectiveness of countermeasure against severe fuel damage in a shutdown
reactor(Caution)
 This document contains the new safety standards (Severe Accident Management) outline
compiled based on the discussions by the “The Study Team on the New Safety Standards
for Light Water Reactor for Electric Power Generation”.
 This document compiles regulatory requirements in a free format. Legislative structure,definitions of terms, and detailed provisions shall be determined in the future in accordancewith legal examples.

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Foreword
This section gives an overall view of the new regulatory requirements for severe accident
management. Section1~4 and Section 6~9 are the requirements for reactor license permit and thedetails of them are mentioned in this draft. Section 5, 10 and11 are neither the requirements forreactor license permit nor the subjects of public comment, which will be considered further in the
future.
(Countermeasures against Severe Core Damage)
1 Licensees shall take countermeasures against severe core damage assuming beyond thedesign basis accidents. (Hereinafter referred to as, “Countermeasures against Severe Core
Damage”).
(Countermeasures against Containment Vessel Failure)
2 Licensees shall take countermeasures against Containment Vessel failure assuming acontainment vessel failure mode considerable. (Hereinafter referred to as,“Countermeasures against Containment Vessel failure”).
(Countermeasures against Severe Fuel Damage in Spent Fuel Storage Pools)
3 Licensees shall take countermeasures against severe fuel damage in spent fuel storage pools
assuming an accident considerable that may cause severe fuel damage in spent fuel storage
pools. (Hereinafter referred to as, “Countermeasures against Fuel Damage in Spent Fuel
Storage Pools”).
(Countermeasure against Severe Fuel Damage in a Reactor during Shutdown)
4 Licensees shall take countermeasures against severe fuel damage in a reactor during
shutdown assuming an accident considerable that may cause severe fuel damage in a
Reactor during Shutdown. (Hereinafter referred to as, “Countermeasure against Severe Fuel
Damage in a Reactor during Shutdown”).
(Activities for improving safety margin)
5 Licensees shall take a measure to improve the safety margin of equipment for design basis
requirement against natural phenomena and external human events, as far as reasonably
practicable.
(Accident management with portable equipment, etc.)
6 Licensees shall establish procedures to cool reactor, containment vessel and spent fuelstorage pools and minimize the release of radioactive material in the event of large-scale
damage to the plant as a result of a large-scale natural disaster or act of terrorism, etc., suchas the intentional airplane crash, and shall prepare a system for taking action as well as
equipment, such as portable equipment, etc., in accordance with these procedures.
3

(Specific Safety Facilities)
7 Licensees shall construct robust specific safety facilities designed to withstand acts ofterrorism, etc., such as the intentional airplane crash etc., in order to suppress the release ofa large amount of radioactive material due to the containment vessel damage in the event
severe core damage caused by acts of terrorism, etc., such as the intentional airplane crashetc.,(Comprehensive Countermeasures for Suppression of Release)
8 Licensees shall prepare means to suppress the release of radioactive material to outside of
the site in order to comprehensively manage various accidents such as severe core damage
and Containment Vessel failure, or sever fuel damage in spent fuel storage pools(Evaluation of the Effectiveness of Countermeasures against Severe Accidents)
9 Licensees shall establish optimal severe accident countermeasures such as below,
considering not only accident sequence groups and containment vessel failure modes
specified by the Nuclear Regulatory Authority (NRA) in advance but also those regarded asindicating significant core damage frequency and detrimental impact throughimplementation of internal event probabilistic risk assessment (PRA) (individual plantexamination (IPE)) and external event PRA (individual plant examinations for external
events (IPEEE)) at each plant. Licensees shall evaluate the effectiveness of thosecountermeasures for severe accident.
a. Countermeasures against severe core damage
b. Countermeasures against Containment Vessel failurec. Countermeasures against severe fuel damage in spent fuel storage poolsd. Countermeasure against severe fuel damage in a reactor during shutdown(Comprehensive Risk Assessment Including an Impact Assessment for beyond Design Basis
External Events)
10 Licensees shall assess the impact on safety function by beyond design basis external events
as well as by design basis internal and external events in accordance with the following
methods and shall implement a comprehensive risk assessment for those events considering
their voluntary activities.
a. Internal event PRA (IPE)b. External event PRA (IPEEE)c. Safety margin evaluation (so-called Stress Tests)
d. Airplane Crash impact assessment

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(Reflection of the Latest Knowledge and Continuous Improvements)
11 Licensees shall continuously improve the safety of nuclear reactor facilities based on the
results of comprehensive risk assessment considering the latest knowledge related to reactor
safety.

5New Safety Standard (SA) Outline Draft
1. Definitions (SA-related)
Terms used in this outline draft shall be defined as follows.
① “Equipment for design basis requirement” refers to, equipment newly installed in order to meetthe requirements of the new safety standard (Design Basis) outline as specified separately.
② “Alternate equipment” refers to, equipment prepared to substitute required function in the eventthat Equipment for design basis requirement loses safety function for some reason.
③ “Portable alternate equipment” refers to, alternate equipment that can be moved.
(Self-propelled equipment included).
④ “Permanent alternate equipment” refers to, alternate equipment that is not intended to be
moved for use and already connected to the nuclear facilities in advance.
⑤ “Severe accident mitigation equipment” refers to, equipment used to prevent Containment
Vessel failure after severe core damage.
⑥ “Beyond design basis accidents capable of severe core damage” refers to, an abnormal
situation where safety related SSCs designed to manage design basis accidents have lostsafety function resulting in the possibility of severe core damage and an abnormally hugeamount of release of radioactive material from the nuclear facility. Even though consideredextremely low the occurrence frequency, those accidents are assumed to evaluate the safetylevel of the nuclear facilities or the effectiveness of countermeasures for severe accident.
⑦ “Accident sequence group” refers to, the sub-categorization of accident sequences based on
event progression and the similarity between accident mitigation operations.
⑧ “Containment vessel failure mode” refers to, the physical phenomena, the cause of containment
vessel failure that may occur in conjunction with severe core damage and affect thecontainment vessel integrity.
⑨ “Specific safety facilities” refers to, facilities with function to suppress a large amount ofradioactive material release caused by containment vessel failure in the event of severe coredamage or almost damaged core as a result of acts of terrorism, etc., such as the intentional
airplane crash, etc.
⑩ “Cliff edge” refers to, a large deviation from normal condition caused by rapid transient as aresult of a small deviation in one parameter; that is an abrupt and dramatic deviation of NPP
responding to a small fluctuation in input data. Furthermore, a small deviation refers to, theloss of function of a single equipment or system, damage to a single structure, a single
operation error, or the limit values of plant parameters, such as temperature or pressure that
could greatly alter plant conditions.

62. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(1) Common Requirements① Requirements for alternate equipment[Basic Requirements](Capacity, environmental conditions and load conditions, operability)
1 Alternate equipment shall effectively function as required during beyond design basis
accidents.
a. Alternate equipment shall be designed to have suitable capacity required to manage
design basis accidentsb. Alternate equipment shall be designed to function as required with sufficient reliability
under environmental and load conditions supposed during beyond design basis
accidentsc. Alternate equipment shall be designed to guarantee operability under the conditions
associated with beyond design basis accidents.
(Diversity and dispersed installation)
2 When installing alternate equipment particularly important to safety, both equipment for
design basis requirement and alternate equipment shall be deployed dispersedly at the siteand secure the diversity of drive power sources for them as necessary so as not to lose
intended safety function due to common factors.
(Note: The need for this is mentioned for each countermeasure).
(Detrimental impact prevention)
3 Alternate equipment shall be installed so as not to cause any detrimental impact onequipment for design basis requirement.
(Easy Changeover )4 Equipment and procedures shall be designed so as to allow easy and certain changeoverfrom normal line configurations in the event that equipment for design basis requirement
is used for a purpose of severe accident countermeasures other than its originally intendeduse.

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2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(1) Common Requirements② Requirements for portable alternate equipment[Basic Requirements](Capacity)
1 Portable alternate equipment shall be designed with suitable capacity margins inaccordance with equipment reliability to have the required capacity to manage beyond
design basis accidents.
(Diversity)
2 Portable alternate equipment shall be as diverse as possible so as to substitute for
equipment for design basis requirement and permanent alternate equipment.
(Reliable connections)
3 Measures shall be taken to standardize connection methods to ensure that portable
alternate equipment and permanent equipment can be easily and surely connected and thatsuch equipment can be used interchangeably between systems and units. Furthermore,
multiple connections shall be prepared and the location of these connections shall bedispersed.
(Robust conduits, etc.)
4 Internal conduits, valves, and electric cables beyond the connection point shall have thesame seismic resistance as equipment for design basis requirement for which they are to
substitute.
(Storage places)
5 Portable alternate equipment shall be dispersed in different locations where are not easily
impacted by external events (earthquakes, tsunami, etc.). Portable alternate equipment
shall be stored in different locations from permanent alternate equipment.
(Field work environment)
6 The installation locations of portable alternate equipment shall enable the installation,connection, operation, and recovery work under conditions associated with beyond designbasis accidents by selecting suitable place supposed not to be affected severely by theaccident and enhancing the shielding performance.
(Securing access routes)
7 Access routes should be designed and managed effectively so as to ensure the availabilityof required access routes outside of buildings needed to transport portable alternate
equipment.

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[Requirement details](Capacity)
A Portable alternate equipment capacity margins for portable alternate power sources andportable cooling injection equipment shall be as follows.
(a) 200%/unit to provide two connections per unit.
(b) 100% backup during malfunctions and 100% standby exclusion through inspections andmaintenance.
(c) 100% refers to performance that can effectively provide necessary function in the event of
beyond design basis accidents.
(Robustness)
B “Having equal seismic resistance” refers to, the ability to maintain intended function even after
suffering equal seismic motion.
(Storage places)
C Portable alternate equipment shall be stored in locations in consideration of intentional
airplane crash. For example, locations isolated more than 100m from reactor buildings thatwould not be simultaneously affected along with the reactor building. Otherwise, locations
should be robust enough to withstand an airplane crash.

92. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(1) Common Requirements③ Requirements for recovery work
[Basic Requirements](Securing spare parts, etc.)
1 So as to conduct replacement or maintenance of component particularly important tosafety, suitable spare parts and tools necessary for replacing shall be secured.
(Storage place)
2 Spare parts shall be stored in dispersed locations withstanding the impact of external
events (tsunami, earthquake, etc.).

(Securing access routes)
3 Access routes should be designed and managed effectively so as to ensure the availabilityof required access routes outside of buildings needed to confirm the damage status ofequipment and perform recovery work.

[Requirement Details](Securing spare parts)
A “tools necessary for replacing” refers to, equipment necessary for operation under various
weather conditions, etc., operational vehicle for removing debris, lighting equipment needed
for night work.
.

102. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(1) Common Requirements④ Requirements for permanent alternate equipment[Basic Requirements](Improving reliability)
1 Even if portable alternate equipment can be used to maintain necessary function in theevent that equipment particularly important to safety loses function, in order to further
improve reliability, as a rule, permanent alternate equipment shall be installed.
(Described in detail in the following pages)(Robustness)
2 Permanent alternate equipment shall have the same earthquake and tsunami resistance as
equipment for design basis requirement for which it is to substitute. Permanent alternate
equipment shall be diverse in its application to the equipment for design basis requirement
for which it is to substitute.

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2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(1) Common Requirements⑤ Miscellaneous requirements[Basic Requirements](Permanent severe accident mitigation equipment)
1 Permanent severe accident mitigation equipment, such as filtered containment vessel
venting system, etc., shall adhere to the requirements for alternate equipment even if it is
not considered alternate equipment.
2 As a rule, permanent severe accident mitigation equipment may not be shared by morethan two nuclear facilities. However, this rule shall not apply if risk can be reduced bysharing the equipment under the condition that no other detrimental impact is caused.
(Assistance)
3 Measures prepared in advance at a site (alternate equipment, spare parts, fuel, etc.) shallenable the continued management of an accident for seven days after occurrence of theevent. A plan to enlist assistance from external organizations shall be created upon
consultation and agreement by pertinent organizations. Measures prepared in advanceoutside the site (alternate equipment, spare parts, fuel, etc.) shall be able to provide
assistance for six days after occurrence of the event.
.

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2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(2) Preparation of procedures, implementation of drills, and development of emergency responseorganizational system[Basic Requirements]
Procedures shall be created in advance, personnel drill, and a necessary system for securingpersonnel created so as to allow an accident that exceeds design basis accidents to be dealt
with accurately and flexibly.
[Requirement Details](Note: When licensing a nuclear reactor the following basic plan shall be confirmed along with thedetails of succeeding regulations, such as operational safety program approval.)
A Procedures shall be created in accordance with the following.
(a) Procedures shall compile types of information required to ascertain plant status in a limited
amount of time and accurately make decisions in regard to the implementation of severe
accident countermeasures, methods for obtaining this information, and judging criteria in
preparation for the loss of all AC and DC power sources, and multiple failures of safetysystem devices and instrumentation.
(b) Procedures shall clarify in advance the standards for determining what operations should beprioritized in order to prevent core damage and containment vessel failure. (Including SLCS,
sea water usage and venting.)(c) Procedures shall be created appropriately for both operators and supporting organizations so
as to allow the implementation of detailed severe accident countermeasures in accordancewith the development of the event. Furthermore, if procedures are divided into multiple types
in accordance with how an event develops the organization of these documents, as well as thestandards for transitioning between procedures, shall be clarified.
(d) Measurable parameters used as standards for determining the implementation of actual severe
accident countermeasures, such as water level, pressure, and temperature, etc., shall be clearlystated in the procedures. Furthermore, parameter behavior forecasts, impact assessment items,
and monitoring parameters, etc., during implementation of severe accident countermeasures
shall be compiled in the procedures.
(e) A procedure to manage an event at the point when precursors of the event are discovered (forexample, reactor shut down and cooling operations when a large tsunami warning has been
issued) shall be created.
B Drill shall conform to the following requirements.
(a) Since severe accident countermeasures must be diverse enough to manage various plantsituations, education and drill related to such countermeasures shall enable trainees toimprove their knowledge of the behavior of a plant during a severe accident.
(b) In addition to periodical education to improve the understanding of basic knowledge basedon the role of each personnel, practice drills used to comprehensively confirm theeffectiveness of severe accident countermeasure implementation organizations and support
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organizations shall be planned.
(c) Along with acquiring on-the-job drill by replacing parts through voluntary maintenance andinspection activities implemented on a normal basis, personnel shall also become intimatelyfamiliar with the plant and spare parts through daily maintenance.
(d) Personnel shall be trained how to manage accidents under various conditions such as highradiation levels, and during the nighttime and in bad weather.
(e) Through normal maintenance and inspection activities personnel shall be trained andprepared so as to enable them to quickly use information and manuals related to equipment
and equipment used during accidents.
C System for securing personnel(a) The sharing of responsibilities and persons in charge of organizations implementing severe
accident countermeasures and assisting organizations shall be established, and a system thatenables the effective implementation of severe accident countermeasures created.
(b) Implementation organization refers to organizations that implement severe accident
countermeasures, such as operators, and organizations that transport and operate alternate
equipment.
(c) Implementation organizations shall be able to respond even in the event of simultaneous
severe accidents at all units.
(d) Chief reactor engineers shall work full-time at each unit.
(e) Such supporting organizations as technical support organizations that give technical advice tothe implementation organization, and operations support organizations that prepare an
environment that allows the implementation organization to focus on severe accident
countermeasures, etc., shall be created.
(f) Implementation organizations and support organizations shall be created under conditions that
require implementation of severe accident countermeasures. Furthermore, the smoothsummoning of personnel shall be enabled by implementing periodic call-out drill during
which necessary personnel gathers at the plant in accordance with a system of communicationeven during nights and holidays.
(g) The functions of the severe accident countermeasure implementation organization andassisting organizations, as well as the function of each unit created within the assistingorganizations shall be clarified and a leader established for each unit.
(h) The chain of command shall be clarified. Alternate chains of command shall also be preparedin the event that the commander, etc., is absent.
(i) Facilities and equipment shall be organized so as to effectively engage in the aforementioned
implementation system.
(j) A system that allows supporting organizations to inform internal and external organizations asnecessary of plant status and the status of implementation of severe accident countermeasures,and provide a wide variety of information shall be created.
(k) A system for receiving support outside the power station shall be constructed.

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2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(3) Countermeasures for reactor shutdown[Basic Requirements]
Prepare equipment and procedures for maintaining the integrity of the reactor coolant
pressure boundaries and the containment vessel while maintaining reactor sub-criticality inorder to prevent severe core damage in the event of an anticipated transient without scram(ATWS), or indications of such an event*.

[Requirement Details]
A “Indications of such an event” refers to, cases where it is assumed from changes in parameters,such as reactor output and reactor pressure, etc., that the reactor has not scrammed regardless ofwhether or not the reactor must be scramming (emergency reactor shutdown).
B “Equipment and procedures for maintaining reactor sub-criticality” refers to, the measuresdescribed below or measures that have the same or better effect.
Common to BWR, PWR(Procedures)(a) Manually scram the reactor in the event that ATWS indications are detected.
For BWR(Permanent alternate equipment)(b) Installation of an alternate control rod insertion circuit (ARI) independent from the reactor
scram system from sensor output to final activator input.
(c) Installation of a device that automatically trips the reactor coolant recirculation pump inorder to control reactor output in the event that ATWS indications are detected. The pumpshall be manually tripped if it is not automatically tripped.
(d) Installation of a standby liquid control system (SLCS) response level control capability.
Judging criteria for startup shall be clearly described.
(e) The SLCS shall be started manually in the event that unstable output vibrations aredetected during an ATWS.

15

For PWR(Procedure)(f) If indications of an ATWS are detected the auxiliary feed water pump will be automaticallystarted and the turbine tripped in order to suppress reactor output. If this fails, it shall bedone manually.
(g) If indications of an ATWS are detected a sufficient amount of boric acid shall be inserted
by chemical volume control equipment and emergency core cooling equipment.

16

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(4) Countermeasures for cooling reactor at high pressure[Basic Requirements]
The installation of equipment and procedures for cooling the reactor using alternate
methods or by restoring reactor cooling function in order to prevent severe core damage inthe event that reactor cooling function is lost when reactor coolant pressure boundaries are athigh pressure.

[Requirement Details]
A “Equipment and procedures for cooling the reactor” refers to, the measures described below ormeasures with the same or better effect.
(Portable alternate equipment)(a) Preparing measures (procedures, portable alternate equipment, equipment, etc.) for startingup the RCIC, emergency condenser (BWR), or turbine drive auxiliary feed water pump
(PWR) through valve operation using portable alternate equipment on site (batteries,
nitrogen tanks, etc.) and continuing operation for a sufficient period of time* assuming thatall AC and DC power sources have been lost.
*: Time needed to prepare and implement “reactor coolant pressure boundary
depressurization countermeasures” and “cooling countermeasures during reactor coolant
depressurization”.
(Field operation)(b) Preparing measures (procedures, equipment, etc.) for starting up the RCIC, emergency
condenser (BWR), or turbine drive auxiliary feed water pump (PWR) through valves
operated by manpower in the field assuming cases where all AC and DC power sources
have been lost and attempts to use alternate equipment resulted in failure.
(Restoration)(c) Enabling startup of the high-pressure insertion system by connecting alternate AC powersource and continuing operation for a sufficient period of time. (BWR)(d) Enabling startup of the motorized auxiliary feed water pump by connecting alternate AC
power source and continuing operation for a sufficient period of time. (PWR)(Monitoring, control)(e) Creating means (procedures, portable alternate equipment, equipment, etc.) for estimating
reactor water level (BWR and PWR) and steam generator water level (PWR) assuming thatall AC and DC power sources have been lost.
17

(f) Creating means (procedures, portable alternate equipment, equipment, etc.) for confirming
the operational status of important safety equipment, such as the RCIC, assuming that all
AC and DC power sources have been lost.
(g) Creating means (procedures, equipment, etc.) for controlling reactor water level and steam
generator water level assuming that all AC and DC power sources have lost.
(Suppressing accident escalation)(h) Creating procedures for injecting coolant from the standby liquid control system (SLCS)
and control rod drive mechanism water pressure system (CRD) in order to suppress
accident escalation.

18

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(5) Countermeasures for depressurization of reactor coolant pressure boundaries[Basic Requirements]
Preparing equipment and procedures, etc., for depressurizing reactor coolant pressure
boundaries by restoring depressurization function, or by alternate means, in order to prevent
severe core damage and containment vessel failure in the event that depressurization
function is lost when reactor coolant pressure boundaries are at high pressure.

[Requirement Details]
A “Equipment and procedures, etc., for depressurizing reactor coolant pressure boundaries”
refers to, the measures described below of measures with the same or better effect.
(Logic additions)(a) Addition of depressurization automated logic for activating the automatic depressurization
function of safety relief valves at low reactor water levels. (BWR).
(Portable alternate equipment)(b) Manual equipment or portable alternate AC power source equipment shall be prepared so
as to enable activation of the depressurization valves (relief safety valves (BWR), main
steam relief valve and pressurizer relief valve (PWR)) and depressurization of reactor
coolant pressure boundaries even in the event of DC power loss.
(c) Portable compressors or nitrogen tanks shall be prepared so as to enable activation ofdepressurization valves and depressurization of reactor coolant pressure boundaries if
depressurization valves are air operated valves.
(d) The conditions that enable activation of depressurization valves shall be clarified.
(Recovery)(e) Recovery procedures using alternate power sources shall be created so as to enable
activation of depressurization valves and depressurization of reactor coolant pressure
boundaries even in the event of DC power loss.
(SGTR)(f) The aforementioned steam generator shall be isolated in the event of a steam generator
tube rupture (SGTR). Procedures shall be created to enable depressurization of reactor
coolant pressure boundaries through activation of pressurization relief valves, etc., in theevent that the steam generator cannot be isolated. (PWR)(ISLOCA)(g) Damaged areas of reactor coolant pressure boundaries shall be isolated in the event of aninterface system LOCA. Procedures shall be created that enable depressurization of reactor
coolant pressure boundaries through activation of relief safety valves (BWR), main steam
relief valves and pressurizer relief valves (PWR) in order to depressurize the reactor andsuppress leaks of reactor coolant in the event that isolation is not possible.

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2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(6) Countermeasures for cooling reactor at low pressure[Basic Requirements]
The installation of equipment and procedures for cooling the reactor using alternate
methods or by restoring reactor cooling function in order to prevent severe core damage andprevent containment vessel failure in the event that reactor cooling function is lost whenreactor coolant pressure boundaries are at low pressure.

[Requirement Details]
A “Equipment and procedures for cooling the reactor” refers to, the measures described below ormeasures with the same or better effect.
(Alternate equipment)(a) Alternate equipment shall be diverse and independent from equipment for design basis
requirement and dispersed over a wide area.
(b) Portable alternate equipment shall be available and ready for use.
(c) Permanent alternate equipment that operates off of principles differing from equipment for
design basis requirement shall be installed in order to manage cases where severe coredamage is imminent.
(Recovery)(d)Means for recovering equipment for design basis requirement through the connection ofalternate AC power sources, etc., shall be devised.

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2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(7) Countermeasures for securing an ultimate heat sink after an accident[Basic Requirements]
The installation of equipment and procedures for carrying heat to an ultimate heat sinkusing alternate methods or by restoring ultimate heat sink system (UHSS) function in order toprevent severe core damage and containment vessel failure in the event that UHSS function is
lost.

[Requirement Details]
A “Equipment and procedures for carrying heat to an ultimate heat sink” refers to, the measuresdescribed below or measures with the same or better effect.
(Core damage prevention)(a) Alternate equipment shall be installed in order to prevent core damage.
(b) Alternate equipment shall be diverse and independent from equipment for design basis
requirement and dispersed over a wide area.
(c) Assuming ultimate heat sink lost due to a loss of water intake function, at BWR’s there
should be sufficient time to connect an onsite alternate UHSS truck and carry heat to an
ultimate heat sink within a fixed period of time during which reactor cooling function is
maintained by forcing heat to accumulate in the suppression pool. Furthermore, at PWR’s
it shall be possible to carry heat to an ultimate heat sink by removing heat using secondary
systems such as the turbine drive auxiliary feed water pump and main steam relief valves.
(Containment vessel failure prevention)(d) Severe accident mitigation equipment shall be installed in order to prevent containment
vessel failure.
(e) Transferring heat from the containment vessel vapor part (however, this excludes
suppression chamber vapor parts in BWR’s that have MARK-1 containment vessels) thatare not impacted detrimentally by core meltdowns or submergence.
(f) In order to further improve reliability equipment shall be installed that is independent fromthe aforementioned severe accident mitigation equipment and dispersed over a wide area.
(Specific safety facilities)
B Use of alternate auxiliary cooling as the aforementioned means shall follow the following.
(a) Installation of alternate auxiliary cooling equipment.

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2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(8) Countermeasures for cooling, depressurization and radioactive material mitigation ofcontainment vessel (Containment vessel spray)[Basic Requirements]
1

Installation of equipment and procedures for using containment vessel alternate coolant
injection spray equipment in order to lower temperature and atmospheric pressure inside
the containment vessel in order to prevent severe core damage in the event of beyond
design basis accidents in conjunction with the loss of containment vessel atmosphericcooling function.

2

Installation of equipment and procedures for using containment vessel alternate coolant
injection spray equipment in order to reduce the temperature, atmospheric pressure andradioactive material concentration inside the containment vessel in order to prevent
containment vessel failure in the event of severe core damage .

[Requirement Details]
A “Containment vessel alternate coolant injection spray equipment” refers to, the measuresdescribed below or measures with the same or better effect.
(Portable alternate equipment)(a) Portable containment vessel alternate coolant injection spray equipment shall be installed
under the assumption that containment vessel coolant injection spray equipment that needs
design standards (pumps or water sources) will lose function.
(b) Containment vessel alternate coolant injection spray equipment drive power sources shallbe diversified and the equipment shall be dispersed over a wide area in order to ensure thatthe function of such equipment, including equipment for design basis requirement andalternate equipment, is not lost due to common factors.
(Permanent alternate equipment)(c) Permanent containment vessel coolant injection spray equipment shall be installed in orderto further improve reliability. (Specific safety facilities)(Dual-use)(d) Containment vessel alternate coolant injection equipment may be used for both purposesof preventing core damage and preventing containment vessel failure.

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2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(9) Countermeasures for heat removal and depressurization of containment vessel[Basic Requirements]
Installation of equipment and procedures for reducing the atmospheric pressure andtemperature inside the containment vessel in order to prevent containment vessel failure in theevent of severe core damage .

[Requirement Details]
A “Equipment and procedures for reducing the atmospheric pressure and temperature inside thecontainment vessel” refers to, the measures described below or measures with the same or
better effect.
(a) Installation of filtered containment vessel venting system.
(Radioactive material reduction countermeasures)(b) Filtered containment vessel venting system shall reduce the amount of radioactive material
contained in exhaust.
(Flammable gas countermeasures)(c) Filtered containment vessel venting system shall be equipped with countermeasures forpreventing explosions due to flammable gases.
(Detrimental impact prevention)(d) Piping of filtered containment vessel venting system shall not be shared with othersystems, devices (for example, SGTS) or those of other units, etc. However, this need not
be the case if there are no detrimental effects.
(Field operation)(e) The isolation valves for filtered containment vessel venting system shall be able to beopened and closed easily and surely by manpower.
(f) Radiation protection countermeasures, such as shielding and isolation, etc., shall be
implemented in order to enable operation of filtered containment vessel venting system inthe field using only manpower and even in times of severe core damage.
(Portable alternate equipment)(g) Measures, such as having required equipment and materials on hand nearby, etc., shall be
implemented in order to enable operation of isolation valves for filtered containment vessel
venting system even in the event of drive power loss.
(Rupture discs)(h) Bypass valves shall be juxtaposed if rupture discs are to be used. However, this shall not
apply to cases where rupture discs set to rupture at sufficiently low pressures are used so as
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not to impede the use of filtered containment vessel venting system.
(Containment vessel connection position)(i) It shall be possible to events of the containment vessel vapor part (however, this excludes
suppression chamber vapor parts for BWR’s that have MARK-I containment vessels) so as
to avoid the impact of submersion or melted core material that may fall or be disbursed
within the containment vessel.
(Radiation protection)(j) Radiation protection countermeasures, such as shielding, etc., shall be implemented inorder to reduce exposure from highly reactive filters, etc., after use.
(Specific safety facilities)(k) Equipment for reducing the atmospheric pressure and temperature inside containment
vessels shall be made redundant, and one piece of containment vessel filters/venting
equipment shall be deemed a specific safety facility in order to further improve reliability.

24

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(10) Countermeasures for cooling melted core fallen to the bottom of the containment vessel[Basic Requirements]
Installation of equipment and procedures for injecting coolant into the bottom of thecontainment vessel in order to cool (suppress MCCI and the spread of core meltdown) melted
core fallen to the bottom of the containment vessel and in order to prevent containment vessel
failure in the event of severe core damage.

[Requirement Details]
A “Equipment and procedures for injecting coolant into the bottom of the containment vessel inorder to cool (Suppress MCCI and the spread of core meltdown) melted core fallen to thebottom of the containment vessel” refers to, the measures described below or measures withthe same or better effect.
(a) Installation of equipment for injecting coolant into the bottom of the containment vessel.
(b) Equipment for injecting coolant into the bottom of the containment vessel shall be
redundant, diversified, independent, and dispersed over a wide area. (However, this shallexclude flow channels and piping above structures inside buildings.)(c) Preparation of portable equipment for injecting coolant into the bottom of the containment
vessel (example, pump trucks, pressure resistant hoses, etc.). (Flow channels insidebuildings used for connecting portable equipment for injecting coolant into the bottom of
the container vessel shall be laid out in advance.)(d) Permanent equipment for injecting coolant into the bottom of the containment vessel shallbe deemed as specific safety facilities in order to further improve reliability.
(e) This equipment shall be compatible with alternate AC power sources.

25

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(11) Countermeasures against hydrogen explosions inside the containment vessel[Basic Requirements]
Installation of equipment and procedures for preventing hydrogen explosions insidecontainment vessels in order to prevent containment vessel failure in the event of severe coredamage.

[Requirement Details]
A “Equipment and procedures for preventing hydrogen explosions” refers to, the measuresdescribed below or measures with the same or better effect.
<BWR>(a) Atmosphere inactivation.
<PWR reactor types that require it>(b) Installation of hydrogen concentration control equipment.
(c) Hydrogen concentration control equipment shall be installed as specific safety facilities inorder to further improve reliability.
<Common to both PWR and BWR>(d) Explosion prevention equipment, radioactive material reduction equipment, and hydrogenand reactive material concentration measurement equipment shall be installed when
discharging hydrogen gas outside the containment vessel.
(e) Installation of monitoring equipment that can measure to certain extent the possibility offluctuations in hydrogen concentration during severe core damage.
(f) This equipment shall be compatible with alternate AC power sources.
(g) Creation of procedures for preventing hydrogen explosions caused by hydrogen andoxygen produced through the radiolysis of water following severe core damage .
.

26

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(12) Countermeasures against hydrogen explosions inside the reactor building, etc.
[Basic Requirements]
Installation of equipment and procedures for preventing damage to the reactor building andcontainment vessel annulus by a hydrogen explosion in the event of severe core damage.

[Requirement Details]
A “Equipment and procedures for preventing damage caused by a hydrogen explosion” refers to,
the measures described below or measures with the same or better effect.
(a) Installation of hydrogen concentration control equipment or hydrogen release equipmentwith explosion prevention and reactive material reduction functions.
(b) Installation of monitoring equipment that can measure to certain extent the possibility offluctuations in hydrogen concentration during envisioned accidents.
(c) This equipment shall be compatible with alternate AC power sources.

27

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(13) Countermeasures for cooling, shielding and ensuring the sub-criticality of spent fuel storage
pools[Basic Requirements]
1

Installation of equipment and procedures for preventing criticality, shielding, and coolingthe fuel in spent fuel storage pools in the event of beyond design basis accidents inconjunction with a loss of spent fuel storage pool cooling function or cooling water
injection function, or the leak of a small amount of pool water.

2 Installation of equipment and procedures for mitigating fuel damage and preventing
criticality in the event that spent fuel storage pool water level cannot be maintained due toa leak of a large amount of water.

[Requirement Details]
A “leak of a small amount of pool water” as mentioned in 1 refers to, a pool water leakenvisioned as part of envisioned accident 2 defined in the “4.(2) Evaluation of theeffectiveness of countermeasures against severe fuel damage in spent fuel storage pools. ” A“leak of a large amount of water” refers to, a leak that exceeds the envisioned amount of poolwater leaked as part of envisioned accident 2.
B The equipment and procedures mentioned in 1 above shall be the measures described below ormeasures with the same or better effect.
(a) The installation of alternate cooling water injection equipment.
(b) Alternate cooling water injection equipment shall be able to maintain pool water leveleven in the event of a loss of equipment for design basis requirement cooling, coolingwater injection function and a small-scale leak.
(c) Portable alternate cooling water injection equipment (for example, cooling water injection
line, pump trucks, shall be prepared as alternate cooling water injection equipment.
C The equipment and procedures mentioned in 2 above shall be the measures described below ormeasures with the same or better effect.
(a) The installation of spray equipment.
(b) Spray equipment shall be able to maintain few cooling even in the event that spent fuelstorage pool water level cannot be maintained by alternate cooling water injection
equipment.
(c) Spray equipment shall be prepared as portable spray equipment (for example, sprayheaders, spray lines, pump trucks).
28

D

The monitoring of spent fuel storage pools shall follow the following in accordance with theequipment and procedures mentioned in 1 and 2 above.
(a) Spent fuel storage pool water level, pool water temperature, and air dose rate above thepool shall be able to be measured to the extent that these parameters will fluctuate as aresult of an accident that exceeds design basis accidents.
(b) This measurement equipment shall be compatible with alternate AC power sources.
(c) Pool status shall be monitored by cameras.

29

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(14) Countermeasures for securing make-up water and water sources[Basic Requirements]
Installation of equipment and procedures that secures sufficient water sources necessary todeal with severe core damage and provides the necessary amount of water from these water
sources to equipment for design basis requirement and alternate equipment in addition toequipment for design basis requirement were sources.

[Requirement Details]
A “Equipment and procedures that provide the necessary amount of water from these water
sources to equipment for design basis requirement and alternate equipment in addition toequipment for design basis requirement were sources” refers to, the measures described below
or measures with the same or better effect.
(a) Must be able to provide sufficient water from the time beyond design basis accidents
occurs until it is managed.
(b) Multiple alternate freshwater sources (for example, water storage tanks, dams, reservoirs,etc.) shall be secured.
(c) The sea must be able to be used as a water source.
(d) Transfer routes from each water source are secured.
(e) Transfer hoses and palms from alternate water sources shall be prepared in advance.
(f) Water source changeover procedures shall be described to ensure that the water supply is
not cut off.
(g) Alternate recirculation equipment shall be installed in order to make recirculationequipment, which uses the containment vessel as a water source, redundant. (PWR).

30

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(15) Countermeasures for securing electricity sources[Basic Requirements]
The installation of equipment and procedures for securing electricity required to prevent
severe core damage, prevent containment vessel failure, prevent spent fuel storage pool fueldamage, and prevent damage to fuel during reactor shutdown.

[Requirement Details]
A “Equipment and procedures for securing electricity required” refers to, the measures described
below or measures with the same or better effect.
(Onsite DC power sources)(a) Onsite permanent DC power source equipment shall be able to provide electricity for 8hours without load cutoff. However, “without load cutoff” does not include cases whereload can be easily cut off from the main control room. In addition, such equipment shall beable to provide electricity for the remaining 16 hours, for a total of 24 hours after cutting
off unnecessary load.
(b) Installation of portable DC power source equipment that can provide electricity for 8hours without load cutoff (not including cases where load can be easily cut off from themain control room), and in addition, can provide electricity for the remaining 16 hours, fora total of 24 hours after cutting off unnecessary load.
(c) One more on-site permanent DC power equipment system (third system) shall be installed
in order to further improve reliability.

B(Alternate power source equipment)
Installation of alternate power source equipment.
(d) Alternate equipment, including Onsite DC power source equipment, shall be diverse(cooling type), independent and dispersed over a wide area.
(e) Portable alternate power sources (for example, power trucks, batteries) shall be madeavailable and ready.
(f) There shall be sufficient time within a fixed period during which electricity can besupplied from Onsite DC power source equipment to connect portable alternate powersources and begin supplying electricity.
(g) Installation of permanent alternate power sources (for example, gas turbine generators, DC
power source equipment, battery recharging equipment)
31

C

D

(Sharing electricity)
Electricity shall be able to be shared between units(a) Electric cables shall be laid out in advance and be able to be connected manually.
(b) Spare electric cables shall be prepared in case laid out electric cables cannot be used.
(Alternate on-site electric equipment)
Installation of alternate on-site electric equipment (MCC, PC, MC, et.).
(a) Alternate onsite electric equipment, including equipment for design basis requirement,
shall installed so that all of the on-site electric equipment does not lose function for acommon reason, at least one system maintains function, and so that people can approachthe equipment.

32

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(16) Control room
[Basic Requirements](Control room)
1 Installation of equipment and procedures that enable operators to remain in the control
room and respond to an event as much as possible in the event of severe core damage.
2 A secondary control room shall be installed in case operators cannot remain in the main
control room.
[Requirement Details]
A “Equipment and procedures that enable operators to remain in the control room and respond toan event” refers to, the measures described below (when conforming through management(masks, tanks, etc.,) in addition to ventilation and shielded design of the control room), or
measures with the same or better effect.
(a) Control room power sources (ventilation, lighting, etc.) shall allow electricity provisionfrom alternate AC power sources.
(b) The livability of the control room in the case of severe core damage shall be evaluated asfollows.
i) Livability should be assessed assuming the severest result obtained from successful
accident sequence (containment vessel failure prevention countermeasures, such asfiltered containment vessel venting system, etc., effectively function after severe coredamage) from among the containment vessel failure modes envisioned in the evaluationof the effectiveness.
ii) Operators are wearing masksiii) A shift system is employediv) Judging criteria shall be preventing operators from receiving an effective dose of no
more than 100mSv over seven days.
(c) Furthermore, the livability of the secondary control room shall be evaluated in this mannerassuming that the secondary control room must be used to manage the event in the casethat containment vessel failure prevention countermeasures do not effectively function. In
this instance, the assumed amount of release radioactive material shall be on par with thatof the TEPCO Fukushima Daiichi NPS accident (for example, release volume from thereactor building shall be X% of inventory/hour X Y hours. Weather conditions of
cumulative wind appearance frequency of Z%).
(d) The secondary control room shall be deemed a specific safety facility.

33

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(17) Emergency response facilities[Basic Requirements](Situation room)
Installation of equipment and procedures to allow the situation room to maintain function as alocal command center, such as communicating with the relevant parties both inside andoutside the power station, and accommodating required personnel, while giving necessary
countermeasure instructions in the event of an accident that exceeds design basis accidents.

[Requirement Details]
A “Equipment and procedures to allow the situation room to maintain function as a local
command center” refers to, the measures described below or measures with the same or better
effect.
(a) The situation room shall be seismically isolated and not lose function as the result of adesign standard earthquake, and it shall also not be impacted by design standard tsunamis.
(b) The situation room shall be compatible with alternate AC power sources.
(c) Equipment that allows reactor facility information necessary for countermeasure
instructions to be ascertained shall be installed.
(d) The situation room should be equipped with equipment for countermeasure staff(dosimeters, masks, etc.) as shall enable sufficient radiation control.
(e) Records required for the deliberation of materials and countermeasures shall be on hand.
(f) Enough food and drinking water to continue activities for one week without outside
assistance shall be stored in the situation room.
(g) The situation room shall be designed to be shielded, and have redundant and independent
ventilation systems in order to ensure livability.
(h) The livability of the situation room during accidents that exceeds design standards shall beassessed as follows.
i) The assumed amount of release radioactive material shall be on par with that of the
TEPCO Fukushima Daiichi NPS accident (for example, release volume from thereactor building shall be X% of inventory/hour X Y hours. Weather conditions of
cumulative wind appearance frequency of Z%).
ii) Excluding cases where special protection measures have been implemented, thesituation room shall be assessed under the assumption that countermeasure personnel
will not be wearing masks inside the situation room when plumes pass overhead, etc.
iii) The shift system will be considered.
iv) Judging criteria shall prevent operators from receiving an effective dose of no morethan 100mSv over seven days.
(i) Area sectioning shall be implemented so as to allow monitoring and the changing of work
clothes while preventing contamination from being carried into the situation room of theemergency response facilities where the outside of the situation room has been
contaminated by radioactive material.

34

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(18) Instrumentation facilities[Basic Requirements]
Installation of equipment and procedures for estimating necessary plant data in the eventthat some normal and emergency instruments have malfunctioned due to beyond design basis
accidents.

[Requirement Details]
A “Equipment and procedures for estimating necessary plant data” refers to, the measuresdescribed below or measures with the same or better effect.
B Furthermore, “necessary plant data” refers to, plant status information that must be ascertainedin order to have core damage prevention countermeasures and containment vessel failure
prevention countermeasures deliberated by operators succeed.
(a) Clarification of the capability of instruments to ascertain plant status under conditions of
beyond design basis accidents. (Maximum measurable temperature, etc.)(b) Preparation of means for estimating plant status in the event that the conditions mentioned
above are exceeded.
i) Preparation of means for estimating temperature, pressure, and water level inside thereactor pressure vessel.
ii) Preparation of means for estimating the amount of cooling water injected into thereactor and reactor pressure vessel.
iii) Parameters needed to make such estimates should be prioritized in advanceconsideration of accuracy from among multiple parameters.
(c) Parameters required to manage beyond design basis accidents, such as temperature,pressure, water level, hydrogen concentration, and dose rate inside the reactor containment
vessel shall be able to be monitored, measured, and recorded.
(d) Preparation of means for measuring and monitoring especially important parameters
during loss of DC power sources (for example, testers, conversion charts, etc.).

35

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(19) Radiation monitoring facilities[Basic Requirements]
1

Installation of equipment and procedures for monitoring, measuring, and recording
radioactive material released from nuclear facilities and radiation conditions in the event ofsevere core damage.

2 Installation of equipment and procedures for measuring and recording wind direction andwind speed, etc.

[Requirement Details]
A “Equipment and procedures for monitoring, measuring, and recording radioactive material
released from reactor facilities” refers to, the measures described below or measures with thesame or better effect.
(a) Monitoring equipment shall be able to measure radioactive material and radiation assumed
to be released in the event of core damage and containment vessel failure.
(b) A sufficient number of monitoring cars and portable alternate monitoring equipment shallbe available and ready so as to substitute for monitoring posts in the event of function loss.
(c) Monitoring equipment shall be compatible with alternate AC power sources.
(Recovery work)
B Background radiation reduction countermeasures shall be deliberated so as to avoid situations
where radiation levels cannot be measured due to contamination of the area after an accident.

36

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(20) Communications equipment[Basic Requirements]
Installation of equipment and procedures for communicating with necessary parties bothwithin and outside the nuclear power plant in the event of beyond design basis accidents.

[Requirement Details]
A “Equipment and procedures for communicating with necessary parties” refers to, the measuresdescribed below or measures with the same or better effect.
(a) Communications equipment shall be compatible with alternate AC power sources.

37

2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)(21) Countermeasures for preventing off-site radioactive release[Basic Requirements]
Installation of equipment and procedures for suppressing off-site radioactive release in theevent of severe core damage and spent fuel storage pool fuel damage or failure of thecontainment vessel.

[Requirement Details]
A “Equipment and procedures for suppressing off-site radioactive release” refers to, themeasures described below or measures with the same or better effect.
(a) Installation of equipment that allows the reactor building to be sprayed with water.
(b) Water spraying equipment shall be able to deal with aircraft fuel fires.
(c) Water spraying equipment shall be able to be moved and spray water on the reactor
building from multiple directions.
(d) A quantity of water spraying equipment that equals half the number of plants onsite(rounded number) shall be prepared under the assumption that such equipment will be
used simultaneously for multiple plants.

38

3. Accident Management for External Events beyond Design Basis(1) Accident management with portable equipment, etc.
[Basic Requirements](Accident handling with portable equipment, etc.)
Procedures shall be created for the following items under editions where the plant has
suffered large-scale damage due to a large-scale natural disaster or acts of terrorism such as
the intentional airplane crash. Furthermore, equipment and a structure designed to enable these
activities in accordance with the aforementioned procedures shall be prepared.
a. Activities to extinguish a large-scale fireb. Countermeasures to mitigate fuel damagec. Countermeasures to minimize the release of radioactive materiald. Countermeasures to maintain necessary water levels in the spent fuel storage pools andcountermeasures to mitigate fuel damage(Note) Requirements are described in “2. Severe Accident Countermeasure Requirements(Primary equipment for each countermeasure)”[Requirement Details]
A Activities to extinguish a large-scale fire” refers to the following.
(a) The preparation of procedures for engaging in fire extinguishing activities using a foam
release cannon under the assumption of an external fire resulting from the intentional
airplane crash. (In the event that function is lost due to a fire inside the control building
resulting from the intentional airplane crash, containment vessel failure shall be prevented
by specific safety facilities. Refer to the following pages)
B

The creation of procedures that envision a large-scale natural disaster for the following items
from “2. Severe Accident Countermeasure Requirements (Primary equipment for eachcountermeasure)”.
(4) Cooling countermeasures when reactor coolant is at high pressure(5) Depressurization countermeasures for reactor coolant pressure boundaries(6) Cooling countermeasures when reactor coolant is at low pressure(7) Countermeasures for securing an ultimate heat sink after an accident(8) Containment vessel cooling, depressurization and radioactive material mitigation
countermeasures39

(9) Containment vessel heat removal and depressurization countermeasures(10) Countermeasures for cooling melted core fallen to the bottom of the containment vessel(11) Countermeasures for preventing hydrogen explosions inside the containment vessel(12) Countermeasures for preventing hydrogen explosions inside the reactor building, etc.
(13) Countermeasures for cooling, shielding and ensuring the sub-criticality of spent fuelstorage pools(14) Countermeasures for securing make-up water and water sources(15) Countermeasures for securing electricity sources(21) Countermeasures for preventing off-site radioactive releaseC

Creation of procedures for the items above that envision acts of terrorism, such as theintentional airplane crash.

40

3. Accident Management for External Events beyond Design Basis(2) Specific safety facilities[Basic Requirements](Definitions)〇 “Specific safety facilities” refers to, facilities that function to suppress the release of a large
amount of radioactive material due to damage of the containment vessel in the event that thecore is, or may be, remarkably damaged as a result of terrorism, etc., such as the intentional
airplane crash, etc. (Reprint)(Specific safety facility requirements)
1 Specific safety facilities must be installed in accordance with the following.
a. Specific safety facilities shall be equipped with adequate measures for preventing the lossof necessary function due to the intentional crashing of a large airplane into the reactor
building.
b. Specific safety facilities shall be equipped with adequate measures for preventing the lossof necessary function due to standard seismic motion and standard tsunamis.
c. Specific safety facilities shall be installed with equipment required to prevent containment
vessel failure.
d. Equipment shall be designed so as to allow use over a fixed period of time.
(Creation of a system that allows specific safety facility function to be maintained)
2 A system that allows specific safety facility function to be maintained shall be created.

[Requirement Details]
A “Specific safety facilities shall be equipped with adequate measures for preventing the loss ofnecessary function due to the intentional crashing of a large airplane into the reactor building”
mentioned in 1.a. refers to, for example, ensuring that Specific safety facilities are far enoughaway from the reactor building (for example over 100 m) so as to prevent simultaneous
failure of both facilities, or the housing of specific safety facilities in a robust structure thatcan withstand the intentional airplane crash.
B “Specific safety facilities shall be equipped with adequate measures for preventing the loss ofnecessary function due to standard seismic motion and standard tsunamis” mentioned in 1.b.
refers to, applying the same design standard allowable limits for design standard seismic
motion and standard tsunamis (for example, applying design standard margins for standard
seismic motion), but implementing countermeasures that differ in character from design
standard protective measures (diversity). For example, whereas equipment for design basis
requirement have rigid structures, specific safety facilities shall be seismically isolated, haveearthquake resistant structures, and shall be housed in buildings that are guaranteed to be41

watertight or in buildings located on high ground.
C The requirements of 1.a. and 1.b. need not be satisfied by a single facility and may rather besatisfied by multiple facilities.
D “Specific safety facilities shall be installed with equipment required to prevent containment
vessel failure” mentioned in 1.c. refers to the following equipment.
(Normal plant examples)(a) Depressurization function for reactor coolant pressure boundaries: Equipment for reactor
depressurization operation from secondary control room(b) Core internal meltdown cooling function: Equipment for injecting low pressure coolingwater inside the reactor(c) Function for cooling melted core material that has fallen to the bottom of the containment
vessel: Equipment for cooling water injection into the bottom of the containment vessel(d) Containment vessel cooling/depressurization/radioactive material reduction function:
Equipment for injecting cooling water into containment vessel sprays(e) Containment vessel heat removal/depressurization function: Filters/venting (excluding
exhaust stacks)(f) Support function: Power source equipment, instrument equipment, secondary control room,communications equipment(g) Equipment related to the equipment mentioned above (example: depressurization valves,pipes, etc.)(h) The secondary control and shall have controlling function for controlling operation of“equipment required to prevent containment vessel failure”.
(i) Communication equipment shall be installed in the secondary control room and enablecommunication with the main control room, on-site situation room and other necessary
departments.
(j) Power source equipment shall provide electricity to “equipment required to prevent
containment vessel failure” and shall fulfill the requirements for Specific safety facilities
mentioned in 1.a. and 1.b.. Portable alternate power sources and permanent alternate powersources shall be able to be connected to the aforementioned power source equipment.
Furthermore, even though power source equipment is part of specific safety facilities it
shall be able to be leveraged in the event of the possibility of severe core damage .
E The “fixed period of time” mentioned in 1.d. refers to, the period of time until outside
assistance can be received (for example, at least seven days). Equipment shall be designedwith sufficient capacity to enable functioning of necessary equipment.

42

4. Evaluation of the Effectiveness of Countermeasures against Severe Accidents(1) Evaluation of the effectiveness of countermeasures against severe core damage[Basic Requirements](Evaluation of the effectiveness of countermeasures against severe core damage)
1 Licensees must assume beyond design basis accidents which may cause severe damage tothe core, and perform an evaluation of the effectiveness of countermeasures against coredamage in regards to the following.
a. The capability to prevent the core from being severely damaged and sufficiently cool it.
b. Pressures to which reactor coolant pressure boundaries are subjected are below maximum
use pressures or pressure limits.
c. Pressures to which containment vessel boundaries are subjected are below maximum usepressures or pressure limits.
d. Temperatures to which containment vessel boundaries are subjected are below maximum
use temperatures or temperature limits.
(Evaluation of the effectiveness of countermeasures against containment vessel failure)
2 Licensees must devise countermeasures for preventing damage to the containment vessel
assuming containment vessel failure mode that may occur in conjunction with severe coredamage. (Hereinafter referred to as, “Containment Vessel failure Prevention
Countermeasures”). (Reprint)
3

Licensees must confirm the effectiveness of countermeasures against containment vessel
failure.

[Requirement Details](Evaluation of the effectiveness of countermeasures against severe core damage)
A “beyond design basis accidents which may cause severe damage to the core” refers to, thefollowing accident sequence groups during which structures, systems and devices that are
required to be designed to not hinder reactor safety in the event of abnormally dramaticchanges during operation or a design basis accident have lost safety functions, and there is thepossibility of severe core damage . Furthermore, the accident sequence groups of (a) must becovered regardless of the deliberation results of the accident sequence groups of (b).
(a) Accident sequence groups described by the Nuclear Regulatory Authorityi) BWR
43

・High-pressure/low pressure cooling water injection function loss
・High-pressure cooling water injection/depressurization function loss
・All AC power loss (including “All AC/DC power source loss”)
・Decay heat removal function loss
・Reactor shutdown function loss
・Cooling water injection function loss during LOCA
・Containment vessel bypass (interface system LOCA)ii) PWR・Secondary system heat removal function loss
・AC power loss (including “All AC/DC power source loss”)
・Rector auxiliary cooling water system function loss
・Containment vessel heat removal function loss
・Reactor shutdown function loss
・ECCS cooling water injection function loss
・ECCS recirculation function loss
・Containment vessel bypass (interface system LOCA, steam generator tube rapture)(b) Accident sequence groups that produce significantly frequent core damage selected
through individual plant internal event probabilistic risk assessment (PRA) and external
event PRA (that are applicable).
i) Assessed through individual plant internal event probabilistic risk assessment (PRA)
and external event PRA, or similar methods.
ii) If as a result accident sequence groups that cause a significant frequency or impact andare not included in the accident sequence groups described by the Nuclear Regulatory
Authority are identified, they shall be added as accident sequence groups that require
countermeasures.
B“The capability to prevent the core from being remarkably damaged and sufficiently cool it”
refers to, fulfillment of the following requirements. However, this shall not apply to cases
where sufficient scientific evidence has been offered in regards to the maximum temperatureof fuel cladding tubes and the amount of oxidation.
(a) Fuel cladding tube maximum temperature shall be below 1200℃.
(b) The amount of oxidation of fuel cladding tubes shall be less than 15% of the thickness ofthe cladding tube prior to remarkable oxidation reaction.

44

C

The requirements of 1.b. need not be fulfilled if the cause of the event is loss of reactor
coolant pressure boundary, such as LOCA.

D

The basis for and adequacy of using pressure limits and temperature limits as judging criteria
must be proven.

E

Core damage prevention countermeasure efficacy assessments shall follow “Core Damage
Prevention Countermeasure Efficacy Assessment Standard Assessment Methods (tentativename)”.

(Evaluation of the effectiveness of countermeasures against containment vessel failure)
F“Containment vessel failure mode” mentioned in the second paragraph refers to the following.
Furthermore, the containment vessel failure modes of (a) must be covered regardless of thedeliberation results of the containment vessel failure modes of (b).
(a) Containment vessel failure modes described by the Nuclear Regulatory Commissioni) Static load caused by atmospheric pressure/temperature (containment vessel
over-pressurization/over-heating)ii) High pressure melted matter release/direct heating of containment vessel atmosphereiii) Interaction of melted fuel outside the reactor and coolantv) Direct contact with containment vessel (shell crash)vi) Interaction between melted core and concrete(b) Containment vessel failure modes that produce significantly frequent failure selected
through individual plant internal event probabilistic risk assessment (PRA) and external
event PRA (that are applicable).
i) Assessed through individual plant internal event probabilistic risk assessment (PRA)
and external event PRA, or similar methods.
ii) If as a result containment vessel failure modes that cause a significant frequency or
impact and are not included in the containment vessel failure modes described by the
Nuclear Regulatory Authority are identified, they shall be added as accident sequencegroups that require countermeasures.

G“effectiveness of countermeasures against containment vessel failure” refers to thefulfillment of the following requirements, as necessary, for the containment vessel failuremodes mentioned above.
(a) Pressures to which containment vessel boundaries are subjected shall fall below
maximum use pressures or pressure limits.
45

(b) Temperatures to which containment vessel boundaries are subjected shall fall below
maximum use temperatures or temperature limits.
(c) Total release volume of radioactive material shall not exceed release volume
performance requirement values.
(d) Reactor coolant pressure shall be reduced to below 2.0MPa until reactor pressure vessel
failure.
(e) Containment vessel boundary function shall not be lost due to heat/mechanical load
resulting from the quick interaction between melted fuel outside the reactor and coolant.
(f) Prevention of the detonation of hydrogen that may cause containment vessel failure.
(g) Fulfillment of the requirements of (a) even in the event that flammable gas accumulates
and burns.
(h) Melted core material that has fallen on top of the floor of the containment vessel shallnot spread across the floor and come in direct contact with the containment vesselboundary.
(i) The support function of containment vessel structural parts and primary containment
vessel boundary function shall not be lost due to corrosion caused by core meltdown.
H

The basis for and adequacy of using pressure limits and temperature limits as determination
standards must be proven.

I“Prevention of the detonation of hydrogen that may cause containment vessel failure”
mentioned in (f) shall fulfill the following requirements.
(a) Hydrogen concentration inside the containment vessel shall fall below 13vol% converted
under dry conditions and oxygen concentration shall fall under 5vol%.

J

Evaluation of the effectiveness of countermeasures against containment vessel failure shallfollow the “Containment Vessel failure Prevention Countermeasure Efficacy Assessment
Standard Assessment Methods (tentative name)”.

46

4. Evaluation of the Effectiveness of Countermeasures against Severe Accidents(2) Evaluation of the effectiveness of countermeasures against severe fuel damage in spent fuelstorage pools[Basic Requirements](Evaluation of the effectiveness of countermeasures against severe fuel damage in spent fuelstorage pools)
1 Licensees must devise countermeasures for preventing severe damage to fuel assuming thepossibility of an accident that that may cause severe damage to fuel stored in spent fuelstorage pools (Hereinafter referred to as, “Pool Fuel Damage Prevention
Countermeasures”). (Reprint)
2 Licensees must evaluate the efficacy of the Pool Fuel Damage Prevention Countermeasures
mentioned in the preceding paragraph and confirmed that they meet the following
requirements.
a. Top of active fuel is submergedb. A water level that shields radiation is maintainedc. Sub-criticality is maintained[Requirement Details]
A “An accident that that may cause severe damage to fuel stored in spent fuel storage pools”
refers to, the following accidents that have the potential to damage fuel stored in spent fuelstorage pools.
(a) Envisioned accident 1:
Pool water temperature rises and water level drops due to evaporation as the result of amalfunctioning auxiliary feed system (required by design standards) causing auxiliary
feed failure.
(b) Envisioned accident 2:
A small amount of cool water is lost due to the siphoning effect, etc., and pool water level
decreases.
B Spent fuel storage pool fuel damage prevention countermeasure efficacy assessments shallfollow the “Spent Fuel Storage Pool Fuel Damage Prevention Countermeasure Efficacy
Assessment Standard Assessment Methods (tentative name)”.

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4. Evaluation of the Effectiveness of Countermeasures against Severe Accidents(3) Evaluation of the effectiveness of countermeasure against severe fuel damage in a shutdown
reactor[Basic Requirements](Evaluation of the effectiveness of countermeasure against severe fuel damage in a shutdown
reactor)
1 Licensees must devise countermeasures for preventing damage to fuel assuming thepossibility of an accident that that may cause damage to fuel in shutdown reactors(Hereinafter referred to as, “Shutdown Fuel Damage Prevention Countermeasures”).
(Reprint)
2 Licensees shall assess the effectiveness of the Shutdown Fuel Damage Prevention
Countermeasures” mentioned in the preceding paragraph and confirm that they fulfill thefollowing requirements.
a. Top of active fuel is submergedb. A water level that shields radiation is maintainedc. Sub-criticality is maintained[Requirement Details]
A “Accident that may cause damage to fuel in shutdown reactors” refers to, the following
accidents that may result in damage to fuel in shutdown reactors. Furthermore, the accident
sequence groups of (a) must be covered regardless of the deliberation results of the accident
sequence groups of (b).
(a) Accident sequence groups described by the Nuclear Regulatory Authorityi) Decay heat removal function loss (loss of cooling function during shutdown caused by
RHR)ii) Loss all AC poweriii) Reactor coolant leakiv) Loss of function to maintain reactors sub-criticality(b) Accident sequence groups that produce significantly frequent fuel damage selected
through individual plant internal event probabilistic risk assessment (PRA) during
shutdown.
i) Assessed through individual plant PRA during shutdown or other compatible methods.
ii) If as a result accident sequence groups that cause a significant frequency or impact and48

are not included in the accident sequence groups described by the Nuclear Regulatory
Authority are identified, they shall be added as accident sequence groups that require
countermeasures.
B

Shutdown reactor fuel damage prevention countermeasure effectiveness assessments shallfollow the “Shutdown Reactor Fuel Damage Prevention Countermeasure Efficacy Assessment
Standard Assessment Methods (tentative name)”.

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