Unconfirmed and unresolved issues

[Overview]

• The 6th Progress Report on the Investigation and Examination of Unconfirmed and Unsolved Issues on the Development Mechanism of the Fukushima Daiichi Nuclear Accident（6.38MB）

[Main body, Attachments, and Supporting information]

[Main Body]

Main Body (UPDATE)（1.97MB）

[Attachment 1]

Overview of MAAP (Provided by Japanese only) (617KB)

[Attachment 2]

List of issues (UPDATE) (2.67MB)

[Attachment 3]

Findings from the latest analyses using MAAP5 (2.76MB)

[Attachment 4]

Status of investigation on estimating the situation of cores and containment vessels (UPDATE) (25.2MB)

[Attachment 5]

Sample analysis to understand the accident situation (NEW) (2.34MB)

[Attachment Earthquake-tsunami-1]

Arrival times of tsunami at the Fukushima Daiichi Nuclear Power Station site (UPDATE) (13.9MB)

[Attachment Earthquake-tsunami-2]

Additional examination of emergency AC power equipment losses due to tsunami (1.84MB)

[Attachment 1-1]

Amounts of water injection assumed in MAAP analysis for Unit-1 (90.9KB)

[Attachment 1-2]

Evaluation of plant status by the fuel range water level indicators of Unit-1 (220KB)

[Attachment 1-3]

Impacts of the earthquake on Unit-1 (711KB)

[Attachment 1-4]

Examination into water injection by fire engines (UPDATE) (1.06MB)

[Attachment 1-5]

Evaluation into the amounts of water injected to Unit-1 by fire engines (447KB)

[Attachment 1-6]

Estimation of Unit-1 accident progression based on the measured data and results of analysis to date (801KB)

[Attachment 1-7]

Examination into heat removal by the Unit-1 isolation condensers (980KB)

[Attachment 1-8]

Relocation behavior of molten fuel to below the core (3.59MB)

[Attachment 1-9]

Estimation of causes of high contamination of RCW piping at Unit-1 (UPDATE) (888KB)

[Attachment 1-10]

Analysis of the hydrogen explosion at Unit-1 reactor building (2.25MB)

[Attachment 1-11]

Estimation of accident progression at Unit-1 based on the air dose rate monitoring data (922KB)

[Attachment 1-12]

Identification of the cause of the high radiation dose rate observed in the southeast area of the first floor of the Unit-1 reactor building (NEW) (2.33MB)

[Attachment 2-1]

Reactor pressure behaviors at Unit-2 (279KB)

[Attachment 2-2]

Containment vessel pressure behaviors at Unit-2 (306KB)

[Attachment 2-3]

Amounts of water injection assumed in MAAP analysis for Unit-2 (111KB)

[Attachment 2-4]

RCIC flow rates of Unit-2 after the loss of power supply (UPDATE) (299KB)

[Attachment 2-5]

RHR system situations after tsunami arrival at Unit-2 (726KB)

[Attachment 2-6]

Behavior of primary containment vessel pressure starting about 12 o’clock on March 14th in Unit-2 (847KB)

[Attachment 2-7]

Correlation between neutrons detected outside the reactor building and fuel melting (243KB)

[Attachment 2-8]

Evaluation of integrity of suppression chamber (S/C) at Unit-2 (619KB)

[Attachment 2-9]

Evaluation of Unit-2 reactor pressure increase after forced depressurization, using a thermal-hydraulic analysis code (1.14MB)

[Attachment 2-10]

Sharp increase of CAMS readings on March 15th at Unit-2 (266KB)

[Attachment 2-11]

FP release behavior at Unit-2 estimated from CAMS readings on March 14th and 15th (UPDATE) (1.37MB)

[Attachment 2-12]

SRV operation states after the core damage at Unit-2 (UPDATE) (999KB)

[Attachment 2-13]

Water level and temperature changes in the suppression chamber (S/C) of Unit-2 (1.48MB)

[Attachment 2-14]

Estimation of reactor water levels at the time when core damage and core melt progressed at Unit-2 (0.98MB)

[Attachment 2-15]

Estimation of the reason why high dose rate was not observed in the auxiliary cooling water system of the Unit-2 reactor (NEW) (1.74MB)

[Attachment 2-16]

Containment pressure drop in Unit-2 during the morning of March 15 (NEW) (1.22MB)

[Attachment 2-17]

Behavior of S/C pressure gauge at Unit-2 after 21:00 on March 14 (NEW) (2.34MB)

[Attachment 2-18]

Evaluation method of the core damage ratio of the Mark-I containment vessel (NEW) (883KB)

[Attachment 3-1]

Reactor pressures during high pressure water injection at Unit-3 (296KB)

[Attachment 3-2]

Amounts of water injection assumed in MAAP analysis for Unit-3 (191KB)

[Attachment 3-3]

Reactor pressure decreasing behavior at about 9:00 on March 13th in Unit-3 (UPDATE) (1.12MB)

[Attachment 3-4]

Reactor pressure changes from about 02:00 to about 12:00 on March 13th at Unit-3 (1.00MB)

[Attachment 3-5]

The cause of RCIC shutdown in Unit-3 (UPDATE) (1.37MB)

[Attachment 3-6]

Dose increase on around March 20th (UPDATE) (1.41MB)

[Attachment 3-7]

Causes of PCV pressure increase at Unit-3 from March 11th to 12th, 2011 (1.03MB)

[Attachment 3-8]

Leaks from the Unit-3 PCV and steam release in a large amount (UPDATE) (844KB)

[Attachment 3-9]

Estimation of reactor water levels at the time when core damage and core melt progressed at Unit-3 (543KB)

[Attachment 3-10]

Evaluation of the fraction of Unit-3 vent gas that flowed into Unit-4 reactor building (756KB)

[Attachment 3-11]

Examination of the water level in the pressure suppression chamber of Unit-3 (NEW) (2.31MB)

[Attachment 3-12]

Accident progression after Unit-3 reactor depressurization (NEW) (3.25MB)

[Attachment 3-13]

Examination of plant conditions during RCIC operation of Unit-3 (NEW) (1.36MB)

[Supporting information 1]

Analysis results from MAAP code published on March 12, 2012 (NEW) (Provided by Japanese only)（829KB）

[Supporting information 2]

Estimation of conditions in the reactor pressure vessels and containment vessels after the Fukushima Daiichi Nuclear Power Station (NEW)（36.4MB）