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Press Releases 2017

Press Release (Dec 25, 2017)The 5th Progress Report on the Investigation and Examination of Unconfirmed and Unresolved Issues on the Development Mechanism of the Fukushima Daiichi Nuclear Accident

TEPCO has been investigating and examining 52 unconfirmed and unresolved issues on the development mechanism of the Fukushima Daiichi Nuclear Accident, in order to make progress on decommissioning work and continuous improvements of safety technology at nuclear power stations.

In this 5th Progress Report, we show the investigation and examination results for 6 of the 52 issues.

Moreover, the investigation and examination to understand the development mechanism of all 10 high-priority issues was completed by the 4th progress report.

[Main body and Attachments of Full Report]

Main Body (UPDATE)(PDF 1.46MB)PDF
[Attachment 1]:Overview of MAAP (Available in Japanese only)(PDF 617KB)PDF
[Attachment 2]:Findings from the latest analyses using MAAP5 (PDF 3.14MB)PDF
[Attachment 3]:Findings from the latest analyses using MAAP5 (PDF 2.76MB)PDF
[Attachment 4]:Status of investigation on estimating the situation of cores and containment vessels (UPDATE)(PDF 7.29MB)PDF
[Attachment Earthquake-tsunami-1]:Arrival times of tsunami at the Fukushima Daiichi Nuclear Power Station site(PDF 2.97MB)PDF
[Attachment Earthquake-tsunami-2]:Additional examination of emergency AC power equipment losses due to tsunami (NEW)(PDF 1.84MB)PDF
[Attachment 1-1]:Amounts of water injection assumed in MAAP analysis for Unit-1(PDF 90.9KB)PDF
[Attachment 1-2]:Evaluation of plant status by the fuel range water level indicators of Unit-1(PDF 220KB)PDF
[Attachment 1-3]:Impacts of the earthquake on Unit-1(PDF 711KB)PDF
[Attachment 1-4]:Examination into water injection by fire engines(PDF 0.98MB)PDF
[Attachment 1-5]:Evaluation into the amounts of water injected to Unit 1 by fire engines(PDF 447KB)PDF
[Attachment 1-6]:Estimation of Unit-1 accident progression based on the measured data and results of analysis to date(PDF 801KB)PDF
[Attachment 1-7]:Examination into heat removal by the Unit-1 isolation condensers(PDF 980KB)PDF
[Attachment 1-8]:Relocation behavior of molten fuel to below the core(PDF 3.59MB)PDF
[Attachment 1-9]:Estimation of causes of high contamination of RCW piping at Unit-1(PDF 1.00MB)PDF
[Attachment 1-10]:Analysis of the hydrogen explosion at Unit-1 reactor building (NEW)(PDF 2.25MB)PDF
[Attachment 1-11]:Estimation of accident progression at Unit-1 based on the air dose rate monitoring data (NEW)(PDF 923KB)PDF
[Attachment 2-1]:Reactor pressure behaviors at Unit-2(PDF 279KB)PDF
[Attachment 2-2]:Containment vessel pressure behaviors at Unit-2(PDF 306KB)PDF
[Attachment 2-3]:Amounts of water injection assumed in MAAP analysis for Unit-2(PDF 111KB)PDF
[Attachment 2-4]:RCIC flow rates of Unit-2 after the loss of power supply(PDF 106KB)PDF
[Attachment 2-5]:RHR system situations after tsunami arrival at Unit-2(PDF 634KB)PDF
[Attachment 2-6]:Behavior of primary containment vessel pressure starting about 12 o'clock on March 14th in Unit-2(PDF 847KB)PDF
[Attachment 2-7]:Correlation between neutrons detected outside the reactor building and fuel melting(PDF 243KB)PDF
[Attachment 2-8]:Evaluation of integrity of suppression chamber (S/C) at Unit-2(PDF 619KB)PDF
[Attachment 2-9]:Evaluation of Unit-2 reactor pressure increase after forced depressurization, using a thermal-hydraulic analysis code(PDF 1.14MB)PDF
[Attachment 2-10]:Sharp increase of CAMS readings on March 15th at Unit-2(PDF 265KB)PDF
[Attachment 2-11]:FP release behavior at Unit-2 estimated from CAMS readings on March 14th and 15th(PDF 850KB)PDF
[Attachment 2-12]:SRV operation states after the core damage at Unit-2 (PDF 1.67MB)PDF
[Attachment 2-13]:Water level and temperature changes in the suppression chamber (S/C) of Unit-2(PDF 1.48MB)PDF
[Attachment 2-14]:Estimation of reactor water levels at the time when core damage and core melt progressed at Unit-2 (NEW)(PDF 0.98MB)PDF
[Attachment 3-1]:Reactor pressures during high pressure water injection at Unit-3(PDF 296KB)PDF
[Attachment 3-2]:Amounts of water injection assumed in MAAP analysis for Unit-3(PDF 191KB)PDF
[Attachment 3-3]:Reactor pressure decreasing behavior at about 9:00 on March 13th in Unit- 3(PDF 439KB)PDF
[Attachment 3-4]:Reactor pressure changes from about 02:00 to about 12:00 on March 13th at Unit-3(PDF 1.00MB)PDF
[Attachment 3-5]:The cause of RCIC shutdown in Unit 3(PDF 440KB)PDF
[Attachment 3-6]:Dose increase on around March 20th (PDF 1.43MB)PDF
[Attachment 3-7]:Causes of PCV pressure increase at Unit-3 from March 11th to 12th, 2011 (PDF 1.03MB)PDF
[Attachment 3-8]:Leaks from the Unit-3 PCV and steam release in a large amount (PDF 905MB)PDF
[Attachment 3-9]:Estimation of reactor water levels at the time when core damage and core melt progressed at Unit-3 (NEW)(PDF 543KB)PDF
[Attachment 3-10]:Evaluation of the fraction of Unit-3 vent gas that flowed into Unit-4 reactor building (NEW)(PDF 756KB)PDF

Previous press releases about Progress Reports #1-4 can be accessed here.

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