Update to Information Sheet Regarding the Tohoku Earthquake
The Federation of Electric Power Companies of Japan (FEPC) Washington DC Office
As of 12:00PM (EST), April 27, 2011
- Revised Estimate of Reactor Core Damage Ratio
- On April 27, TEPCO announced the revised estimate of reactor core damage ratio (the percentage of damaged fuel rods against the entire amount of fuel rods in the reactor core) due to the data correction of radiation dose measured by CAMS (Containment Atmospheric Monitoring System). The estimated ratios of the entire reactor core damage of Unit 1,2, and 3 were revised as follows:
After Correction | Before Correction | |
Unit 1 (as of 3/15 3:25PM JST) | approximately 55% | approximately 70% |
Unit 2 (as of 3/15 3:25PM) | approximately 35% | approximately 30% |
Unit 3 (as of 3/14 4:20AM) | approximately 30% | approximately 25% |
- Radiation Levels
- The concentration of radioactive nuclides from the seawater sampled at the screen device (installed to remove waste before the intake of seawater) of Unit 2 and sampled near the seawater discharge point (south side) of Fukushima Daiichi Nuclear Station were as follows:
Nuclides (half-life) | Concentration (Unit : Bq/cm3) | Ratio | |||||
Sampled inside the silt fence at the screen of Unit 2 | Sampled outside the silt fence at the screen of Unit 2 | Sampled at south side discharge point | Maximum Permissible Water Concentration (d) | a / d | b / d | c / d | |
4/26 7:27AM (a) | 4/26 7:22AM (b) | 4/26 2:10PM (c) | |||||
I-131 (8 days) | 1.3 x 102 | 7.7 x 101 | 2.7 x 10-2 | 4.0 x 10-2 | 3,300 | 1,900 | 0.68 |
Cs-134 (2 years) | 2.4 x 101 | 1.7 x 101 | 1.3 x 10-1 | 6.0 x 10-2 | 400 | 280 | 2.2 |
Cs-137 (30 years) | 2.5 x 101 | 1.7 x 101 | 1.3 x 10-1 | 9.0 x 10-2 | 280 | 190 | 1.4 |
- At 3:00PM (JST) on April 27, radiation level at main gate (approximately 3,281 feet from Unit 2 reactor building) of Fukushima Daiichi Nuclear Power Station: 51 micro Sv/hour.
- At 3:00PM on April 27, radiation level at west gate (approximately 3,609 feet from Unit 2 reactor building) of Fukushima Daiichi Nuclear Power Station: 22.6 micro Sv/hour.
- Measurement results of environmental radioactivity level around Fukushima Nuclear Power Station announced at 4:00PM on April 27 are shown in the attached PDF file. English version is available at: http://www.mext.go.jp/
english/incident/1304082.htm - For comparison, a human receives 2,400 micro Sv per year from natural radiation in the form of sunlight, radon, and other sources. One chest CT scan generates 6,900 micro Sv per scan.
- Plant Parameters
Unit 1 | Unit 2 | Unit 3 | Unit 4 | Unit 5 | Unit 6 | |
pressure inside the reactor core (gauge pressure, MPa) | 0.445 | -0.018 | -0.053 | - | 0.003 | 0.010 |
4/27 11:00AM | 4/27 11:00AM | 4/27 11:00AM | - | 4/27 6:00AM | 4/27 6:00AM | |
pressure inside the primary containment vessel (absolute pressure, MPaabs) | 0.155 | 0.075 | 0.1029 | - | - | - |
4/27 11:00AM | 4/27 11:00AM | 4/27 11:00AM | - | - | - | |
water level inside the reactor core (meter) *1 | -1.65 | -1.5 | -1.85 | - | +1.561 | +2.174 |
4/27 11:00AM | 4/27 11:00AM | 4/27 11:00AM | - | 4/27 6:00AM | 4/27 6:00AM | |
temperature of the reactor vessel measured at the water supply nozzle (degrees Fahrenheit) | 266.0 | 248.5 | 180.1 | - | - | - |
4/27 11:00AM | 4/27 11:00AM | 4/27 11:00AM | - |
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