在日本福島核電廠事故陰影下談核能問題 Fukushima Nuclear Crisis (Cause, Consequence, Lessons, Challenges)

在日本福島核電廠事故陰影下談核能問題

Fukushima Nuclear Crisis(Cause, Consequence, Lessons, Challenges)

锺赐贤 (Philip T. Choong)北京大学

May 5, 2011

4/27/2011 Fuku Crisis 1

• General Introduction 基本核能概念介紹– What is nuclear energy? Where is it used today? 甚麼是核能 ? 用於何處 ?– Different types of nuclear reactor around the world. 全球核電廠的類別– Basic description of LWR nuclear power plant. 沸水式以及壓水式核電廠簡

• Fukushima Daiichi Crisis 福島一号核電廠危機– Troubled Fukushima Daiichi plants. 福島第 1 核電廠概況– Sequence of major events at Fukushima Daiichi 福島核電廠危機始末 – What are the contributors to the crisis? 事故發生的主因– What is the latest status? Is the crisis over? 目前最新情況如何 ? 危機結束了嗎 ?– Potential impacts on LWR technologies 事故對輕水式反應爐技術的衝擊

• Aftermath of Radiation Leakage from Fukushima plants 福島核電廠幅射物洩漏後果– Basic knowledge of radiation in biological world 核幅射基本常識以及生物界中的幅射– Background radiation in daily life 日常生活環境中的幅射– What people should know about radiation from Fuku crisis? 大眾對福島核電廠幅射物洩漏應有的認識– Tips to reduce radiation exposure in your body 如何使身體減少接受幅射

• Beef-up Nuclear Power Plants Safety Standards Practice 各國對加強核電廠安全問題的做法– Would PWR Be More Robust in SBO? 在長時間停電下輕水式反應爐安全嗎 ?– Susceptibility of 台电 NPP to Meltdown 台电核电厂堆熔化易感性– Imposing “Walk-Away Safe” requirement 设立”不必介入”安全條款

• The Necessity of Nuclear Energy 核能的必要性 I– Impacts on Energy Independence and Carbon Emissions 能源独立与地球暖化問題– High-Temperature Pebble-bed Gas-cooled Rectors 高溫球床氣冷反應堆– New opportunities for China 飞來橫祸 - 因祸得福

• Final Words - A Rational and Balanced View 平衡理性的結語

• Q&A (问题和解答 )4/27/2011 Fuku Crisis 2

基本核能概念介紹What is nuclear energy?

• Radioactive decay energy (alpha, beta, gamma, neutron, etc.)

• Nuclear fission• Nuclear fusion


Where is nuclear energy used?

• Weapons• Electricity production• Submarine and ship propulsion• Medical diagnostics• Food processing• Agriculture• Detectors• Heating, desalination & Many others


10 MW PWR Launched in 1954

1950, ANL built and operated the first submarine reactor prototype, the Zero Power Reactor I (ZPR-1) for Westinghouse Electric to fit in 28 feet submarine beam.


Shippingport Pressure Vessel


Schematics of PWR Power Station


About 1/3 of commercial power reactors in USA are of BWR type; ¾ of nuclear power plants in Taiwan are of BWR type including the latest BWR-6 GEN-III type.4/27/2011 Fuku Crisis 8

中国实验快堆 - Critical in Spring of 2010


Russian RBMK High Power Channel-type Reactor


CANDU Schematics


Pebble-Bed High-Temperature ReactorHTR-PM (China)

Wu Zongxin, INET, Introduction of HTR-PM Demonstration Project, IAEA Technical Meeting on the Safety of HTGRs, Beijing, October 2007.4/27/2011 Fuku Crisis 12

Fukushima I: Early Generation II


BWR Mark I Nuclear Island-3D


BWR Mark I Containment During Construction


BWR Internals


BWR Sub-Channels


Mark II BWR ECCS System


Distribution of 55 Nuclear Power Plants


Fukushima I & II


21

Fukushima Daiichi Nuclear Station Fukushima Daiichi Nuclear Station• Six BWR units at the Fukushima Nuclear Station:

– Unit 1: 439 MWe BWR, 1971 (unit was in operation prior to event)– Unit 2: 760 MWe BWR, 1974 (unit was in operation prior to event)– Unit 3: 760 MWe BWR, 1976 (unit was in operation prior to event)– Unit 4: 760 MWe BWR, 1978 (unit was in outage prior to event)– Unit 5: 760 MWe BWR, 1978 (unit was in outage prior to event)– Unit 6: 1067 MWe BWR, 1979 (unit was in outage prior to event)

• Six BWR units at the Fukushima Nuclear Station:– Unit 1: 439 MWe BWR, 1971 (unit was in operation prior to event)– Unit 2: 760 MWe BWR, 1974 (unit was in operation prior to event)– Unit 3: 760 MWe BWR, 1976 (unit was in operation prior to event)– Unit 4: 760 MWe BWR, 1978 (unit was in outage prior to event)– Unit 5: 760 MWe BWR, 1978 (unit was in outage prior to event)– Unit 6: 1067 MWe BWR, 1979 (unit was in outage prior to event)

Unit 1

4/27/2011 Fuku Crisis

Status of Fukushima Daiichi Plantas of March 2011


Fukushima I Operating History


Fuel Assembly in Fukushima Reactors


BWR Mark I Nuclear Island


SFP during Refueling


Fukushima I Before Big Quake


28

福島一号核電廠危機 Event Initiation福島一号核電廠危機 Event Initiation• The Fukushima nuclear facilities were

damaged in a magnitude 8.9 earthquake on March 11 (Japan time), centered offshore of the Sendai region, which contains the capital Tokyo.– Plant designed for magnitude 8.2 earthquake.

An 8.9 magnitude quake is 7 times in greater in magnitude.

• Serious secondary effects followed including a significant tsunami, significant aftershocks and a major fire at a fossil fuel installation.

• The Fukushima nuclear facilities were damaged in a magnitude 8.9 earthquake on March 11 (Japan time), centered offshore of the Sendai region, which contains the capital Tokyo.– Plant designed for magnitude 8.2 earthquake.

An 8.9 magnitude quake is 7 times in greater in magnitude.

• Serious secondary effects followed including a significant tsunami, significant aftershocks and a major fire at a fossil fuel installation.


Location of Quake Center


Many Versions and Interpretations of Events

• Tokyo Electric Company• 台湾电力公司• TSC• Unofficial AREVA• Micro Simulation Technology


Summary March 11-15, 2011


Summary March 11-15, 2011


33

Initial ResponseInitial Response

• Nuclear reactors were shutdown automatically. Within seconds the control rods were inserted into core and nuclear chain reaction stopped.

• Cooling systems were placed in operation to remove the residual heat. The residual heat load is decreasing from 6.6% of the heat load under normal operating conditions.

• Earthquake resulted in the loss of offsite power which is the normal supply to plant.

• Emergency Diesel Generators started and powered station emergency cooling systems.

• One hour later, the station was struck by the tsunami. The tsunami was larger than what the plant was designed for. The tsunami took out all multiple sets of the backup Emergency Diesel generators.

• Reactor operators were able to utilize emergency battery power to provide power for cooling the core for 8 hours.

• Operators followed abnormal operating procedures and emergency operating procedures.

• Nuclear reactors were shutdown automatically. Within seconds the control rods were inserted into core and nuclear chain reaction stopped.

• Cooling systems were placed in operation to remove the residual heat. The residual heat load is decreasing from 6.6% of the heat load under normal operating conditions.

• Earthquake resulted in the loss of offsite power which is the normal supply to plant.

• Emergency Diesel Generators started and powered station emergency cooling systems.

• One hour later, the station was struck by the tsunami. The tsunami was larger than what the plant was designed for. The tsunami took out all multiple sets of the backup Emergency Diesel generators.

• Reactor operators were able to utilize emergency battery power to provide power for cooling the core for 8 hours.

• Operators followed abnormal operating procedures and emergency operating procedures.


34

Loss of MakeupLoss of Makeup• Offsite power could not be restored and delays occurred obtaining and connecting

portable generators. • After the batteries ran out, residual heat could not be carried away any more.???• Reactor temperatures increased and water levels in the reactor decreased,

eventually uncovering and overheating the core.• Hydrogen was produced from metal-water reactions in the reactor.• Operators vented the reactor to relieve steam pressure - energy (and hydrogen)

was released into the primary containment (drywell) causing primary containment temperatures and pressures to increase.

• Operators took actions to vent the primary containment to control containment pressure and hydrogen levels. Required to protect the primary containment from failure.

• Primary Containment Venting is through a filtered path that travels through duct work in the secondary containment to an elevated release point on the refuel floor (on top of the reactor building).

• A hydrogen detonation subsequently occurred while venting the secondary containment. Occurred shortly after and aftershock at the station. Spark likely ignited hydrogen.

• Offsite power could not be restored and delays occurred obtaining and connecting portable generators.

• After the batteries ran out, residual heat could not be carried away any more.???• Reactor temperatures increased and water levels in the reactor decreased,

eventually uncovering and overheating the core.• Hydrogen was produced from metal-water reactions in the reactor.• Operators vented the reactor to relieve steam pressure - energy (and hydrogen)

was released into the primary containment (drywell) causing primary containment temperatures and pressures to increase.

• Operators took actions to vent the primary containment to control containment pressure and hydrogen levels. Required to protect the primary containment from failure.

• Primary Containment Venting is through a filtered path that travels through duct work in the secondary containment to an elevated release point on the refuel floor (on top of the reactor building).

• A hydrogen detonation subsequently occurred while venting the secondary containment. Occurred shortly after and aftershock at the station. Spark likely ignited hydrogen.


35

Misleading Core Damage SequenceMisleading Core Damage Sequence

Core Uncovered Fuel Overheating Fuel melting - Core Damaged

Core Damaged but retained in vessel Some portions of core melt

into lower RPV head

Containment pressurizes. Leakage possible at drywell

head

Releases of hydrogen into secondary containment


This is an incorrect depiction of multi-sub-channel BWR core.

Fuku Crisis

Sequence of major events at Fukushima Daiichi 福島核電廠危機始末

Containment Isolation Closing of all non-safety related

Penetrations of the containment Cuts off Machine hall If containment isolation succeeds, a

large early release of fission products is highly unlikely

Diesel generators start Emergency Core cooling systems are

supplied

Plant is in a stable safe state

4/27/2011 36

Fuku Crisis

Fukushima Daiichi Sequence of Major Events-1

11.3. 15:41 Tsunami hits the plant Plant Design for Tsunami height of up

to 6.5m Actual Tsunami height >7m Flooding of

Diesel Generators and/or Essential service water

building cooling the generators

Station Blackout Common cause failure of the power

supply Only Batteries are still available Failure of all but one Emergency core

cooling systems

4/27/2011 37

Fuku Crisis

Reactor Core Isolation Pump still available

Steam from the Reactor drives a Turbine

Steam gets condensed in the Wet-Well

Turbine drives a Pump Water from the Wet-Well gets

pumped in Reactor Necessary:

Battery power Temperature in the wet-well

must be below 100°C

As there is no heat removal from the building, the Core isolation pump cant work infinitely


4/27/2011 38

Fuku Crisis

Reactor Isolation pump stops 11.3. 16:36 in Unit 1

(Batteries empty) 14.3. 13:25 in Unit 2

(Pump failure) 13.3. 2:44 in Unit 3

(Batteries empty)

Decay Heat produces still steam in Reactor pressure Vessel

Pressure rising

Opening the steam relieve valves Discharge Steam into the Wet-Well

Descending of the Liquid Level in the Reactor pressure vessel


4/27/2011 39

Fuku Crisis

Measured, and here referenced Liquid level is the collapsed level. The actual liquid level lies higher due to the steam bubbles in the liquid

~50% of the core exposed Cladding temperatures rise, but still

no significant core damage

~2/3 of the core exposed Cladding temperature

exceeds ~900°C Balooning / Breaking of the cladding Release of fission products form the

fuel rod gaps


4/27/2011 40

Fuku Crisis

~3/4 of the core exposed Cladding exceeds ~1200°C Zirconium in the cladding starts to

burn under Steam atmosphere Zr + 2H20 ->ZrO2 + 2H2

Exothermal reaction furtherheats the core

Generation of hydrogen

Unit 1: 300-600kg Unit 2/3: 300-1000kg

Hydrogen gets pushed via the wet-well, the wet-well vacuum breakers into the dry-well


4/27/2011 41

Fuku Crisis

at ~1800°C [Unit 1,2,3]

Melting of the Cladding Melting of the steel structures

at ~2500°C [Block 1,2]

Breaking of the fuel rods debris bed inside the core

at ~2700°C [Block 1] Melting of Uranium-Zirconium

eutectics

Restoration of the water supply stops accident in all 3 Units???No,No,No.

Unit 1: 12.3. 20:20 (27h w.o. water) Unit 2: 14.3. 20:33 (7h w.o. water) Unit 3: 13.3. 9:38 (7h w.o. water)


4/27/2011 42

Fuku Crisis

Release of fission products during melt down

Xenon, Cesium, Iodine,… Uranium/Plutonium remain in core Fission products condensate to

airborne Aerosols

Discharge through valves into water of the condensation chamber

Pool scrubbing binds a fraction of Aerosols in the water

Xenon and remaining aerosols enter the Dry-Well

Deposition of aerosols on surfaces further decontaminates air


4/27/2011 43

Fuku Crisis

Containment Last barrier between Fission

Products and Environment Wall thickness ~3cm Design Pressure 4-5bar

Actual pressure up to 8 bars Normal inert gas filling (Nitrogen) Hydrogen from core oxidation Boiling condensation chamber

(like a pressure cooker)

Depressurization of the containment Unit 1: 12.3. 4:00 Unit 2: 13.3 00:00 Unit 3: 13.3. 8.41


4/27/2011 44

Fuku Crisis

t

Positive and negative Aspects of depressurizing the containment

Removes Energy from the Reactor building (only way left)

Reducing the pressure to ~4 bar Release of small amounts of Aerosols

(Iodine, Cesium ~0.1%) Release of all noble gases Release of Hydrogen

Gas is released into the reactor service floor

Hydrogen is flammable


4/27/2011 45

Fuku Crisis

Unit 1 und 3 Hydrogen burn inside the reactor

service floor Destruction of the steel-frame roof Reinforced concrete reactor building

seems undamaged Spectacular but minor safety relevant


4/27/2011 46

Fuku Crisis

Unit 2 Hydrogen burn inside the reactor

building Probably damage to the condensation

chamber(highly contaminated water)

Uncontrolled release of gas from the containment

Release of fission products Temporal evacuation of the plant High local dose rates on the plant site

due to wreckage hinder further recovery work

No clear information's why Unit 2 behaved differently


4/27/2011 47

Fuku Crisis

Current status of the Reactors Core Damage in Unit 1,2, 3 Building damage due to various burns

Unit 1-4 Reactor pressure vessels flooded in all

Units with mobile pumps At least containment in Unit 1 flooded

Further cooling of the Reactors by releasing steam to the atmosphere

Only small further releases of fission products can be expected ???


4/27/2011 48

Fuku Crisis

The Fukushima Daiichi Incident Radiological releases

4/27/2011 49

Fukushima Daiichi After 311


Fuku Crisis

Spend fuel stored in Pool on Reactor service floor

Due to maintenance in Unit 4 entire core stored in Fuel pool

Dry-out of the pools

Unit 4: in 10 days Unit 1-3,5,6 in few weeks

Leakage of the pools due to Earthquake?

Consequences Core melt “on fresh air “ Nearly no retention of fission products Large release

Fukushima Daiichi Sequence of Major Events inSpent Fuel Pool

4/27/2011 51

Fuku Crisis

Fukushima Daiichi Sequence of Major Event inSpent Fuel Pool-cont

Spend fuel stored in Pool on Reactor service floor

Due to maintenance in Unit 4 entire core stored in Fuel pool

Dry-out of the pools

Unit 4: in 10 days Unit 1-3,5,6 in few weeks

Leakage of the pools due to Earthquake?

Consequences Core melt in Unit 1, 2, 3 Nearly no retention of fission products Large release to air and ground

4/27/2011 52

Spent Fuel Pool on Fire in Unit 4


Fukushima Daiichi as of March 16, 2011


事故發生的主因• Off-site power wiped out during initial quake on

March 11, 2011 (2:46pm)• Back-up Diesel Generator System destroyed by

tsunami less than an hour later• Back-up Battery of Unit 1 failed after two hours• 14 meters tsunami also destroyed many other

infrastructure in and around the plant.• Crisis Management and Coordination very poor,

made the consequence a lot worse than necessary.


How Would PWR Perform in SBO?

• Sub-cooled water in PWR vessel would provide many more hours before core uncovered

• PWR’s intermediate coolant loop and larger containment could also give more reaction time

• Passive Decay Heat Removal still a “must” to survive prolonged SBO


Pressure Vessel and Containment


目前最新情況如何 ? 危機結束了嗎 ?

• Crisis not over yet, still evolving– New INES as of April 12, 2011 is 7

• Unit 1,2,3 and 4 cannot never be used again• Clean-up may not be possible, entombment may

be necessary• Surrounding area may become waste land• Future of Unit 5 and 6 is questionable• Future of nuclear power in Japan ???• Japan may become even less competitive


IAEA INES Levels


BWR in Taiwan


Taiwan Nuclear Power Plants

Chinshan Kousheng

Maanshan4/27/2011 Fuku Crisis 61

Taipow’s Chinshan is Similar to Fuku Unit1


Additional Beef-ups at Taipower


Recommended SBO Response

• New response to SBO should proceed along multiple parallel paths: – Restoration of the electrical grid ASAP– Recovery of backup diesel generators ASAP– Acquisition of additional batteries – Acquisition of mobile generators – Bring in water tanks to refill Spent Fuel Pool– Bring in crushed ice to cool Spent Fuel Pool


Lessons (Near-Term)• Station Black-Out has been a long-standing but unresolved

issue and it needs an urgent revisit for a satisfactory resolution.

• Emergency Operating Procedures (EOP) needs revisit. • Severe Accident Management Guidance Strategies (SAMG),

which is a worst-case beyond-the-design-basis package needs revisit– Backup power concept and requirement need reassessment– Residual heat removal concept needs reassessment– Off-site water supply uncertainty– Injecting sea water is one of the final options

• Steam-metal chemical reaction heat load issue• Overall Defense-in-Depth strategy needs revisit


Lessons (Long-term)

• Light Water Reactor might not be best for wide-spread civilian use

• What (safety requirement) is adequate for USA , might not be adequate for other countries

• Passive safety concept is better than layer upon layer of defense mechanism

• “Walk-away Safety” is superior and should be a new system design goal?


Micro-Simulation Technology PCTRAN Analysis

( 濮励志 )


Provided by Mr. Seong-Deuk Jo of International Atomic Energy Agency

(IAEA)


Comparison of Decay Heat Estimates

Time after Shutdown

Decay Pwr fraction

0.01 s 0.066010 s 0.039630 s 0.031360 s 0.02701 hour 0.01071 day 0.004710 day 0.0022


PCTRAN Simulation of Fuku Unit 1










Part II of PCTRAN Simulation


Potential Impacts on Nuclear Reactor Technology

• Based on past experience: – Windscale Fire on Oct’57 doomed UK’s Magnox

reactor technology– Chernobyl Disaster on Apr’86 doomed USSR’s

RBMK reactor technology• Fukushima Disaster could doom BWR if not all

LWR reactor technology• Most likely, life-extension for Generation II

plants will be very difficult to get approval


Impacts on Nuclear Energy • Nuclear resurrection momentum nearly

stopped– New orders will be slowed down– Existing constructions will be stretched– Life-extension application approval questionable– EU will have second thought on nuclear option – NRC will revisit SBO EOP and SAMG– China has no BWR but will tighten SBO rules


Impacts on Nuclear Energy (cont)

• Passive Safety may become a New requirement• “Walk-away Safety” will receive more attention• Liability insurance premium cost will shoot up• Uranium price could drop substantially• Procurement of big-ticket items will be a lot easier


Impact on Carbon Emission

• Environment will suffer with more carbon emission;

• each reactor shut-down or cancel will likely increase 6 million tons CO2 discharge every year.


各國對加強核電廠安全問題的做法

• 张国宝 has spoken in Shenzhen last April that China will stay course on nuclear option but will strengthen safety standards

• US will continue nuclear option but will revisit safety standards via a two-prong approach: 90-day quick look followed by a more in-depth review

• France will continue nuclear option but will review safety standards

• Germany has reversed its decision last year on nuclear power life extension

• Italy will not reconsider revising constitution for nuclear


核幅射基本常識以及生物界中的幅射

• 1 mSv = 100 mRem• Average American gets 4-6 mSv• Each hour in airplane 0.006 mSv• Airline worker limit < 9mSv• Nuclear worker <20 mSv• Lethal dose ~4-5000 mSv• Radon is biggest contributor of background

radiation and US lung cancer death• Background dosage 2-4 mSv (1.5-100 mSv)


Average Radiation Exposure in USA(Each Trip to China increases 2-3%)


EPA Data on Radiation Exposure


日常生活環境中的幅射(National Council of Rad and Measurement and ANS)


如何使身體減少接受幅射• Don’t smoke• Avoid second-hand smoke• Spend more time outdoor• Spend more time near sea or lake• Minimize air travel• Minimize use of granite or rocks indoor• Seal all cracks on floor and walls• Open windows whenever possible


The Necessity of Nuclear Energy 核能的必要性

• Rising global warming• Rising atmospheric CO2 ppm• Rising per capita CO2 emission, ton/person/yr• Only nuclear power is an alternative to coal-

fired power • Carbon tax could force to switch to nuclear

power as fast as practical


Global Warming


http://en.wikipedia.org/wiki/File:Instrumental_Temperature_Record.png

Atmospheric CO2 ppm Data


Total and per capita CO2 emissions (2008) Country

Total Emissions (Million metric tons ofCO2)

Per Capita Emissions(Tons/capita)

1. China 6017.69 4.58 (17)

2. United States 5902.75 19.78 (2)

3. Russia 1704.36 12.00 (5)

4. India 1293.17 1.16 (20)

5. Japan 1246.76 9.78 (9)

6. Germany 857.60 10.40 (7)

7. Canada 614.33 18.81 (3)

8. United Kingdom 585.71 9.66 (10)

9. South Korea 514.53 10.53 (6)

10. Iran 471.48 7.25 (14)

11. Italy 468.19 8.05 (12)

12. South Africa 443.58 10.04 (8)

13. Mexico 435.60 4.05 (18)

14. Saudi Arabia 424.08 15.70 (4)

15. France 417.75 6.60 (16)

16. Australia 417.06 20.58 (1)

17. Brazil 377.24 2.01 (19)

18. Spain 372.61 9.22 (11)

19. Ukraine 328.72 7.05 (15)

20. Poland 303.42 7.87 (13)


现阶段电源结构中，火电比重过大4/27/2011 Fuku Crisis 90

China’s U Reserve Very SmallBut Large Th Reserve

Important Considerations for Energy Independence Goal

– Nuclear Safety : Walk-away safety – Resource security: Abundant Th reserve– Nuclear proliferation : Export potential– Global Warming : CO2 Emission– Thermal pollution : Local regional warming– Energy conservation : Conversion efficiency– Waste disposal & Environment protection– Least cost of electricity : Cheaper than coal– Ownership of key Intellectual properties


核電廠設計趨勢 - 地平線上的新希望

• Redouble efforts toward safer, more energy efficient and cost-effective nuclear reactor technology

• Speed up implementation and transition to Generation IV reactor concepts

• High Temperature Pebble-bed Reactor is the best hope


Current Types of Nuclear Power Reactors

There are about 400 power reactors in operation world-wide. None of them can survive prolonged Station Blackout without some core meltdown except for HTR-10 in China.


Safer and More Efficient Concepts


Advanced HTRGWD (Gao-Wen-Dui) Module

04/21/23 Integrated Low Carbon Energy System 96

GWD Fuel Elementswith

Improved Kernel and Pebble Coatings

04/21/23 Integrated Low Carbon Energy System 97

平衡理性的結語• No Practical Alternative to Nuclear Power for

Countries like China• Nuclear Safety is of Paramount and Foremost

Importance• Inherent Safety is Superior to Engineered

Safety • So Far, only Pebble-Bed Reactor Has

Demonstrated to Possess “Walk-Away” Safety Characteristics


Opportunities and Challenges Arise( 因祸得福 )

• China to step up to forefront of nuclear power technology by default– Leading on Generation III+ PWR (EPR and AP1000)– Leading on Generation IV reactor (HTR-PM)

• China can offer to help Taiwan phasing out nuclear power entirely via cross-strait power transmission lines.

• China should take the lead-role in advocating the “Walk-Away” safety requirement in international bodies such as WANO, IAEA and WEC.

• Good Opportunity to Transition from Uranium to Thorium Fuel Cycle• China is capable of developing the cost-effective, safe and

proliferation resistant Gao-Wen-Dui (GWD) in cooperation with its emerging wind power technology to create the most environmentally friendly energy enterprise.



Defense-in-Depth


False Redundant Power Sources

• Off-site Power from multiple grids• Multiple On-site Diesel Generators

– Diesel fuel only for seven days– Subject to common cause failure

• Back-up Battery– Not capable of running any ECCS pumps– For monitors, valves and digital equipment only


Documents

在日本福島核電廠 事故 陰影下談核能問題 Fukushima Nuclear Crisis (Cause, Consequence, Lessons, Challenges)

在日本福島核電廠事故陰影下談核能問題 Fukushima Nuclear Crisis (Cause, Consequence, Lessons, Challenges)