Additional Report of the Japanese
Government to the IAEA
– The Accident at TEPCO’s Fukushima NPSs –(Second report)
September 2011
Nuclear Emergency Response Headquarters

1

Introduction
Since June, each unit of Fukushima Dai-ichi NPS has been making
a stable progress; the amount of released radioactive materials andthe radiation exposure of workers have been significantly reduced,
and the restoration from the accident has been steadily proceedingwith Step 2, which sets as its target “the release of radioactive
materials is under control and the radiation dose is being significantly
held down”.
Meanwhile, off-site actions such as decontamination of thesurrounding areas are being taken, and at the same time, an on-siteplan after the settlement of the accident is also being developed.
Further, as a means to respond to the lessons, establishment of arenewed safety regulatory and administrative system has been clearly
announced.
Developments of these situations are described as follows.

2

Major Actions taken since June
(1) Each unit of Fukushima Dai-ichi NPS has been making a stable
progress, and the amount of released radioactive materials has
been significantly reduced.
(2) Radiation exposure has also been significantly reduced.
(3) Efforts to settle the accident have been made to reach Step 2.
(4) Establishment of a renewed safety regulatory and administrative
systems has been clearly announced.
(5) Comprehensive safety assessments on the safety of nuclear power
stations (stress tests) will be conducted.

(6) Off-site actions such as decontamination are being actively taken.
(Chapter 2)(7) An on-site plan after the settlement of the accident is now being
developed. (Chapter 3)(8) More detailed comprehension and organization of the facts thathave been found so far are being made.
3

Table of Contents
First Chapter:

Situation of the Accident andActions Taken

Second Chapter: Off-site Responses

Third Chapter:

On-site Plans

4

Chapter 1 The Accident and Actions taken so far
1. The stable condition of each unit of Fukushima Dai-ichi
NPS and reduction of release of radioactive materials
2. Reduction of radioactive exposure

3. Transition to Step 2 for the settlement of the accident
4. Establishment of a renewed safety regulatory andadministrative systems

5. Efforts on the comprehensive safety assessments(stress tests) of NPS
6. Comprehension and organization of other facts
5

1. The stable condition of each unit of

Fukushima Dai-ichi NPS and reductionof release of radioactive materials

6

The current situation of each unit of
Fukushima Dai-ichi NPS(1) Unit 1
 Cooling with water at a rate of approximately 3.6 m3/h
→ Stably remaining below 100C at present(2) Unit 2
 Cooling with water at a rate of approximately 3.8 m3/h
→ Stably remaining below 130C at present(3) Unit 3
 Cooling with water at a rate of approximately 7.0 m3/h
→ Stably remaining below 120C at present

7Status of Units 1, 2 and 3 of Fukushima Dai-ichi NPS(As of August 31)
Unit

Unit 1

Unit 2

Unit 3

Status of water injection to
the reactor

Fresh water feeding by feedwater system
Flow rate: 3.6m³/h

Fresh water feeding by feedwater system
Flow rate: 3.8m³/h

Fresh water feeding by feedwater system
Flow rate: 7.0m³/h

Reactor Water Level

Fuel range A: Downscale
Fuel range B: -1,650mm

Fuel range A: -1,850mm*
Fuel range B: -2,200mm*

Fuel range A: -1,350mm*
Fuel range B: -1,850mm*

Reactor Pressure

0.017 MPa g(A)- MPa g(B)0.014 MPa g(A)- MPa g(B)-0.187 MPa g(A)-0.100 MPa g(B)Temperature around thereactor vessel

Temperature in feed-water
nozzle: 92.2 ºC
Temperature at reactor vessel
bottom: 87.4 ºC

Temperature in feed-water
nozzle: 106.9 ºC
Temperature at reactor vessel
bottom: 113.5 ºC

Temperature in feed-water
nozzle: 118.6 ºC
Temperature at reactor vessel
bottom: 109.2 ºC

Pressure in D/W,
S/C

D/W: 0.1259 MPa abs
S/C: 0.105 MPa abs

D/W: 0.115 MPa abs
S/C: Downscale

D/W: 0.1015 MPa abs
S/C: 0.1810 MPa abs

StatusEach plant receives electricity from external power supplies. The process is carried on ensuring
reliability of cooling function by installing temporary emergency diesel generators and the seawater
pump etc.

* These data may be modified when TEPCO makes evaluates them.

8Units 1, 2 and 3(Current Temperature Condition of the RPV Bottom)

9Reduction of Release of Radioactive Materials(1) The amount of released radioactive materials has beensignificantly reduced.
 Initially high levels of released materials(1015–1016 Bq/h)→ Currently low level (108 Bq/h)(2) The preventive measure for discharging into the sea
has been strengthened.
 Implementing measures such as pit closure and silt
fence installation(3) The environmental monitoring system has beenenhanced.

10

Fukushima Dai-ichi NPS: Trends in the Airborne
Concentration of Radioactive Materials

11

Air Dose Rate Map(As of August 11, 2011)12

The state of enhancement measures to prevent contaminated waterfrom flowing out and mixing with the sea

2011/9/17版

13

＃６

＃５

＃１

＃２

＃３

＃４

④ ③

Monitoring around the Fukushima Dai-ichi NPS②①

福島第一Side
5,6放水口北側（5,6u放水口から北側に約30m地点)放射能濃度（Ｂｑ／L）
Northernof the Water Discharge Canal of 5 and 6

Near the物揚場付近
Shallow Draft
Quay
福島第一
海水放射能濃度（Ｂｑ／L）

1.0E+06

1.0E+07

I-131
Cs-134
Cs-137① ②

1.0E+05

I-131
Cs-134
Cs-137

1.0E+06

1.0E+05

1.0E+04
1.0E+04

1.0E+03
1.0E+03
Cs-137告示濃度（90 Bq/L）
Cs-134告示濃度（60 Bq/L）
I-131告示濃度（40 Bq/L）

1.0E+02

1.0E+01

Cs-137告示濃度（90 Bq/L）
Cs-134告示濃度（60 Bq/L）
I-131告示濃度（40 Bq/L）

1.0E+02

1.0E+01

7月19日～25日は悪天候のため未採取

1.0E+00

1.0E+00
4/19

1.0E+07

4/26

5/3

5/10

5/17

5/24

5/31

6/7

6/14

6/21

6/28

7/5

7/12

7/19

7/26

8/2

4/19

8/9

5/10

5/17

5/24

5/31

6/7

6/14

6/21

6/28

7/5

7/12

7/19

7/26

8/2

8/9

1.0E+07
I-131
Cs-134
Cs-137③ ④

1.0E+05

1.0E+04

1.0E+04

1.0E+03

1.0E+03

Cs-137告示濃度（90 Bq/L）
Cs-134告示濃度（60 Bq/L）
I-131告示濃度（40 Bq/L）

1.0E+02

1.0E+01

I-131
Cs-134
Cs-137

1.0E+06

1.0E+05

Cs-137告示濃度（90 Bq/L）
Cs-134告示濃度（60 Bq/L）
I-131告示濃度（40 Bq/L）

1.0E+02

1.0E+01

1.0E+00
4/19

5/3

福島第一 2号機バースクリーン付近海水放射能濃度（シルトフェンス外側）（Ｂｑ／L）
At Unit 2 (Outside the Silt Fence)

福島第一 1～4号機取水口内北側海水放射能濃度（Ｂｑ／L）
Inside the Water
Intake Channel (Northern Side) for Units 1 to 4

1.0E+06

4/26

1.0E+00
4/26

5/3

5/10

5/17

5/24

5/31

6/7

6/14

6/21

6/28

7/5

7/12

7/19

7/26

8/2

8/9

4/19

4/26

5/3

5/10

5/17

5/24

5/31

6/7

6/14

6/21

6/28

7/5

7/12

7/19

7/26

8/2

8/9

14

Environmental Monitoring:
Enhancing the System(1) Coordination with concerned ministries and agencies,
local government officials and the nuclear operator in
the August 2 “Monitoring Coordination Meeting.” A
Comprehensive Monitoring Plan was developed and air
dose rates, etc. were systematically measured.
(2) The concentration of radioactive materials in the dust
above the sea, seawater, and soil of the seabed off thecoast of Miyagi, Fukushima, and Ibaraki Prefectures,etc. has been continuously measured.

15

2. Reduction of radioactive exposure

16

The Status of Radiation Exposure for Workers(1) Radiation exposure doses for workers (external andinternal doses) have been significantly reduced; thevalue 22.4mSv in average in March was reduced to
3.1mSv in average in May.
(2) In March, there were six workers whose exposure dose
exceeded the 250 mSv emergency dose limit forworkers (among them, the maximum exposure dose
was approximately 670 mSv).

17

Survey on Health Care of Residents in
Surrounding Areas The “Fukushima Prefecture Health Monitoring Survey,”
targeting the approximately two million residents ofFukushima Prefecture, has been started.
 A basic survey is being implemented based onrecords of behavior.
 Then, a detailed survey will be implemented based on
the basic survey (expected to target approximately
200,000 people).
 Ultrasonography of the thyroid gland is being
conducted for all Fukushima residents 18 years of age
or younger.

18

3. Transition to Step 2 for the settlementof the accident

19

Efforts to Settle the Accident(Transition to Phase 2)

 Confirm the following to complete Phase 1 andtransition to Phase 2 on July 19:
 The trend of radiation dose is steadily reducing.
 The cooling of the reactors and spent fuel pools is
progressing.
 Processing of accumulated water is progressing.

20Current Status of “Roadmap towards Restoration from the Accident at
Fukushima Dai-ichi NPS, TEPCO” (Revised edition)

21

Overview of Major Countermeasures in the Power Station as of August 17

22

Circulating Injection Reactor Cooling System
Storage and treatment of high contaminated water
Classification
High contaminated water
Treated water (salt water)
Treated water (condensed)
Processed water (fresh)
Fresh water

Treated Water(Condensed Water)
Receiving Tank

Filtered
Water Tank

Treated Water(Fresh Water)
Receiving Tank

BufferTank

Reactor Building

Desalting System(RO system)

Liquid Waste
Feeding Tank

Radioactive Waste
Treatment Building (High
Temperature Incinerator)

Turbine Building

RPV

Condenser
Radioactive Waste
Treatment Building (MainProcess Building)
PCV

Treatment System(Cesium Absorber)(Decontamination
System)Waste Sludge
Spent Vessel

23

Track Records of Contaminated Water Processing

Operation factor rate & amount processed
Accumulated treatment amount (tons), facility
operation factor (%)

Management of the water level of theaccumulated water within the turbine building24Spent Fuel Pool: Alternative Cooling System (Unit 1)25

Main Issues in Step 2(1) Issue 1
Cooling the reactors: Evaluation of necessary flow rate of injecting
water to achieve “cold shutdown condition”.

(2) Issue 2
Cooling the spent fuel pools: Achieving more stable cooling in all of
the Units 1 through 4.
(3) Issue 3
Treating accumulated water: Decreasing the total amount ofaccumulated water and increasing the treatment volume to increase
the water injection into the reactors.
(4) Issue 4
Shielding groundwater: Preventing the spread of contamination into
the sea.
(5) Issue 5
Preventing the spread of radioactive materials in theatmosphere/soil: Mitigation of release of radioactive materials.
26

4. Establishment of a renewed safety
regulatory and administrative systems

27

Enhancement of Safety Regulatory and
Administrative Systems
 The establishment of a “Nuclear Safety and Security
Agency” (provisional name) was approved by the
Cabinet meeting on August 15.
 Intent: to separate regulation from utilization

 Positioning of the agency: as an external agency of
the Ministry of Environment starting in April 2012
 Necessary legislation: Established “Task Force for the
Reform of Nuclear Safety Regulatory Bodies” (onAugust 26)

28

Concept of the Nuclear Safety and Security Agency(tentative name)(1) Centralize nuclear safety regulatory roles, which thus
far have been divided among various ministries(2) Develop a crisis management structure for the first
response system, such as positioning experts to
respond to emergencies(3) Supervise the environmental monitoring function,
including SPEEDI(4) Ensure high-quality staffing, including establishment of
an “International Nuclear Safety Training Institute”(provisional name)295. Efforts on the comprehensive safetyassessments (stress tests) of NPS

30

Comprehensive Safety Assessment(Stress Test)
Comprehensive safety assessments will be conducted based on
new procedures and rules, with reference to the stress tests introducedin Europe, for enhancing the safety of nuclear power stations andensuring safety and reliance for citizens and residents.

(1) Preliminary assessment:
The nuclear power stations, that are under shutdown due to regularinspections and are prepared for start-up, will be successively
assessed on the safety margins of their facilities and equipment
essential for safety against beyond-design-basis events.

(2) Secondary assessment:
Taking into account the implementation status of stress tests in
Europe and what have been reviewed by the Investigation
Committee on the Accidents at the Fukushima NPS, all nuclear
power stations including the stations under operation and thoseevaluated in the preliminary assessment will be assessed on thecomprehensive safety margins.
31Safety margins for structural integrity of components and piping(Preliminary and Secondary assessments)
Material strength confirmed by testing

Elastic range

Allowable limits ofdesign standards

Stress assumed to be exerted
in design basis earthquakes(calculated value)

Secondary

Safety factors

Preliminary

Total margin

Material strength defined in thestandard

Stress-strain curve
TensionIrreversible deformation(plastic deformation)

Fracture×
Large load(fracture)
Load (small deformation)

Safety margins

Values prescribed in the NSC Regulatory Guides and technical standards areused as allowable limits in preliminary assessment. Values exceeding allowable
limits are applicable if it is technically verified in the preliminary assessment thatthe structure’s integrity and functions are maintained. Factual assessment isconducted during secondary assessment to obtain values that cause the loss ofstructural integrity and functions.

Load removal(no deformation)

Deformation

32

6. Comprehension and organization ofother facts

33

(1) The Tohoku District-Off the Pacific Ocean
Earthquake and the resulting tsunamis

34

Tohoku District-Off the Pacific Ocean Earthquake
and resulting tsunamis
・ A large slip of 55m to not quite 70m was estimated for the Tohoku
earthquake in the shallow part of the plate boundary along the Japan
Trench.
・ There is a high probability that

the Tohoku earthquake was a giant earthquake of M9 in viewpointof long period ground motions;

however, it had the same characteristics as an M8 earthquake inviewpoint of short period ground motions.

・ It is likely that

the large slip in the shallow area along the Japan Trench,and the overlap effects of tsunami waves due to rupture delays
associated with the interlocked rupturing of multiple source areas
had large effects on tsunami water levels.
35Based on
Based onBased onlong-period groundshort-period groundSourcegeodetic
data rupture process (Fault model)
motionmotion

55 m~70 m Mw7.8

Mw8.2
Mw8.4
Mw7.7
Mw7.7

Model proposed by Irikura
Model proposed by GSI and JCG

Model proposed by JNES

・data: land area GPS observation and・moment magnitude: Mw 9seafloor crustal deformation observation ・location of large slip: along the・ the maximum slip: 55 m
Japan Trench・the number of asperities: 5・concentrating in the deep part west to
the hypocenter・total energy: (as of moment magnitude)
Mw 8.5・ There is a high probability that the Tohoku earthquake was a gigantic
earthquake of M9 in terms of long-period ground motions,・ yet hat at the same time characteristics of an earthquake of M8 in termsof short-period ground motions.
36

Tsunami source rupture process(Tsunami source model) Comparison of simulated tsunami waveform (blue) andobserved one (red)Offshoreareas
Off the southerncoast of Iwate
prefecture
G802

8
6
4
2
0
-2
-4
-6
-8
0

FT02_J13_foward/col:8

Simulation (J13)
Observed

15

30

45

60

75

90

105

TP換算_潮位除去_福島第一波高計記録03111430-03111530/col:2

Nuclearsites

Wave height (m)Dai-ichi NPS

FT02_FK1/col:31

J13 : Fukushima 1

15

Fukushima
Fukushima
Dai-ichi NPS

No data due to failure of tide gauge

10

Simulation
Observed

5
0
-5

-10
-15
0

15

30

45

60

75
90
Time(min)

105

120

Time elapsed after the occurrence of the earthquake

150

Simulation
Observed

10
5
0
-5

-10
-15
0

15

地盤変動考慮_TK2_実測波形/col:2

Tokai Dai-ni
Tokai Dai-ni NPS
NPS

135

FT02_ExtEF_ABCDEF/col:2

J13 : Onagawa

15

Wave height (m)Result of water level simulation using tsunami source model：• Offshore areas： The simulated tsunami waveforms being consistent
with the shape of the short-period ones of theobserved first wave
• Nuclear sites ： The simulated tsunami waveforms being consistent
with observed ones
⇒Amount of large slips and asperities：
Locating in the shallow areas (400 km) along the Japan Trench, and resulting in the
maximum slip of above 70 m
⇒Delay in rupture start time of multiple seismic source areas：
It is likely that overlap effect of tsunami waves due to the rupture delay had a great
impact on tsunami water levels.

Onagawa
Onagawa NPS
NPS

Wave Height(m)(f) aggregate slips(m)tsunami(m)HeightWaveof height(e) 270 seconds after
the earthquake
occurrence

tsunami (m)HeightHeight(m)Wave of110726_TP換算後に潮位除去_女川観測記録_20110311_matlab/col:2(d) 210 seconds after
the earthquake
occurrence120

Time(min)Time elapsed after the occurrenceof the earthquakeof tsunami (m)HeightWave Height(m)(a) 30 seconds after the (b) 90 seconds after the (c) 150 seconds after
earthquake
earthquake
the earthquake
occurrence
occurrence
occurrence

The short-period
waveformsof the first G802
wave

G802/col:2

(m)
Wave
Height(m)Wave height Analysis results using tsunami source model: Trends in distribution of slips(a~e) and the aggregate slips (f).

30

45

60

75

90

105

120

Time elapsed after theTime(min)occurrence of the earthquake

135

150

FT02_TK2/col:15

J13 : Tokai 2

15

Simulation
Observed

10
5
0
-5
-10
-15
0

15

30

45

60

75

90

105

120

Time elapsed after theTime(min)occurrence of the earthquake

135

150

37

(2) Initial Release of Radioactive Materials
in the Accident of Fukushima Dai-ichi
NPS

38

Measurement Results Dose Rates by
Monitoring Car at Fukushima Dai-ichi NPS

39

Release of Radioactive Materials:
Initial Release Trends (Bq/h)40

(3) The Situation of Each Unit of
Fukushima Dai-ichi NPS

41

The Situation at Each Unit of Fukushima Dai-ichi NPS(Field situations obtained from interviews with workers, etc.)(1) Rubble strewn by tsunami→ Access routes cleared to ensure fire engine access(e.g. Unit 1)(2) Darkness→ Work on vent valves for the primary containment
vessel proceeded by torchlight (e.g. Unit 1)(3) Shortage of electric power→ Car batteries from employees’ cars were collected tooperate valves for alternative water pumps (e.g. Unit 3)(4) Effects of hydrogen explosion→ The initial alternative pumping lines burst, and work
started on constructing new lines (e.g. Unit 2)42Unit 1: Reactor Pressure Vessel (RPV)
Temperature Transition

43

Unit 1: Spent Fuel Pool Evaluation Results

44Unit 2: RPV Temperature Transition

45

Unit 2: Spent Fuel Pool Evaluation Results

46Unit 3: RPV Temperature Transition

47

Unit 3: Spent Fuel Pool Evaluation Results

48Unit 4: Spent Fuel Pool Evaluation Results

49Unit 4: Installation of Support Structures at the
Bottom of the Reactor Building’s Spent Fuel Pool50

Situation at the Reactor Buildings of
Fukushima Dai-ichi NPS, Units 1 to 4
Unit1 - 4
Unit4

Unit1

Unit3
Unit2

51

(4) Situation of Other NPSs Affected by the Tohoku
District-Off the Pacific Ocean Earthquake andthe resulting tsunamis (Event Tree)

52

⑩
⑪
⑫
Removal of decay heat fromcontainment vessel

Cold shutdown, coredamaged, PCV damage, etc.

PCV vent (before coredamaged)⑨

Removal of heat using RHRRestoration of RHR functions(including restoration ofseawater pump functions andalternative power supply)⑦⑧
Core coolingMotor-driven pumps (otherthan ECCS), (MUWC, etc.)
and depressurizing operation(SRV)

Motor-driven pumps (ECCS,
HPCS, LPCS, LPCI)⑥

Turbine-driven injection lines④⑤
AC power supply

Main steam/watersupply/condensation lines

Power supply
interchangeability③

Emergency diesel generators②
Reactorshutdown

External power①
Accident

Reactor scrammed

No.
Event

Earthquake and tsunami

Transitional Changes in the Accident According to
the Function Event Tree⑬
Core
status53

Situation Transition in the Accident at Other NPSs
(Fukushima Dai-ni NPS)

54

Situation Transition in the Accident at Other NPSs
(Onagawa NPS)

55

Situation Transition in the Accident at Other NPSs
(Tokai Dai-ni NPS)

56

(5) Response regarding Evacuation Areas,
etc57

4. Response regarding Evacuation Areas, etc(1) Restricted Area: On April 22, a Restricted Area wasestablished and all access to the area was prohibited. Now,
temporary access is allowed for residents and those acting in
the public interest.
(2) Deliberate Evacuation Areas: On April 22, Deliberate
Evacuation Areas were established in areas where dose wasincreasing. Most residents had already evacuated.
(3) Evacuation-prepared Areas in Case of Emergency: On April
22, areas for which preparations must be made to evacuate
in the event of an emergency were established for thoseareas where such preparation was required. Now, efforts tolift such restrictions are actively being made.
(4) Specific Areas Recommended for Evacuation: In June,
Specific Areas Recommended for Evacuation were
established for areas with high dose. The number of suchareas is currently 227 (245 households).
58

Map of Restricted Area, Deliberate Evacuation Areas, Evacuation-prepared Areas inCase of Emergency, Specific Areas Recommended for Evacuation(As of August 3, 2011)59

(6) Measures to Address Agricultural Products, etc.

60

7. Measures to Address Agricultural Products, etc.
(Provisional Regulatory Values)

61

Measures to Address Agricultural Products, etc. :Individual Items(1) Tea: Tea, which appears to have a large amount of radioactive
cesium, is “deeply cropped.”(2) Beef: There was some beef from cattle which appear to have eaten
straw containing radioactive cesium. After this discovery, information
calling for attention while handling rice straw was distributed.
(3) Rice: In areas with high concentrations of radioactive cesium in thesoil, a preliminary survey was implemented in the step before
harvesting. The concentration measurements after harvesting areplanned based on the survey results. No radioactive materials
exceeding the provisional regulatory values have been detected (asof August 31).

62