Fukushima Daiichi

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INES-event
INES [N/A]

Possible Flow of Contaminated Water to the Outside of the Controlled Area

Monitoring instruments (Lines A and B) at the side gutter drainage sounded a “High” alarm at 10:00, followed by an ‘Extremely High’ alarm at 10:10 on 22 February, 2015. Peak values were 5.63 kBq/L at 10:30 for Line A, and 7.23 kBq/L at 10:40 for Line B. The “High” alarm was set at 1.5 kBq/L, and “Extremely High” at 3.0 kBq/L – all the values are for Total Beta.
Multiple drainage gates including one downstream were subsequently closed.
No leakage from tanks was observed, and monitoring posts at the site boundary showed no abnormalities.

Category: Power Reactor Fukushima Daiichi Japan »

INES-event
INES 3

Contaminated water leakage from a water tank

?Regarding the contaminated water leakage from a water tank in the H4 Tank Area at Fukushima Daiichi NPS that was detected on August 19, radioactivities in the leaked water in the dike were found to be:
- Cesium-134: 4.6×101 Bq/cm3
- Cesium-137: 1.0×102 Bq/cm3
- β emitting radionuclides in total: 8.0×104 Bq/cm3
?The amount of the leaked water is estimated to be approximately 300m3, judging from the decrease of water level in the water tank in question.

Category: Power Reactor Fukushima Daiichi »

INES-event
INES 7

Re-evaluation of INES rating; Effect to the Nuclear Facilities from the earthquake on east area of Japan

In March 18, rating of the INES on the events in Fukushima Dai-ichi Nuclear Power Station, by the Tohoku Regional Pacific Ocean Offshore Earthquake is temporary estimated Rating 5. However, Nuclear and Industrial Safety Agency (NISA) estimated total amount of discharge from Fukushima Dai-ichi NPS, using the analytical result of the state of nuclear reactor under the cooperation of Japan Nuclear Energy Safety Organization (JNES). As a result of re-evaluation, total amount of discharged I131 is estimated at 1.3E17Bq, and Cs137 is estimated at 6.1E15Bq.

Category: Power Reactor Fukushima Daiichi »

INES-event
INES 3

Loss of cooling function and water supplying function on the spent fuel pool due to the big tsunami.

Fukushima Dai-ichi Nuclear Power Station Unit 4, which was in shutdown mode, was attacked by the Tohoku regional Pacific Ocean Offshore Earthquake around 14:46 (JST) in March 11, 2011.
After that, the power station was attacked by a tsunami.
Electricity rooms and seawater pump rooms were flooded, and the cooling function and water supplying function on the spent fuel pool became inoperable. The temperature of the spent fuel pool has been increasing, and the water level of the spent fuel pool was thought to be decreasing.

Category: Power Reactor Fukushima Daiichi »

INES-event
INES 5

The core damage by loss of all cooling function due to the big tsunami.

In March 18, rating of the INES on the events in Fukushima Dai-ichi Nuclear Power Station, by the Tohoku Regional Pacific Ocean Offshore Earthquake is temporary estimated Rating 5. However, Nuclear and Industrial Safety Agency (NISA) estimated total amount of discharge from Fukushima Dai-ichi NPS, using the analytical result of the state of nuclear reactor under the cooperation of Japan Nuclear Energy Safety Organization (JNES). As a result of re-evaluation, total amount of discharged I131 is estimated at 1.3*10^17Bq, and Cs137 is estimated at 6.1*10^15 Bq.

Category: Power Reactor Fukushima Daiichi »

INES-event
INES 5

The core damage by loss of all cooling function due to the big tsunami.

Fukushima Dai-ichi Nuclear Power Station Unit 1, 2 and 3, which is in rated power operation, have automatically shut down around 14:46 (JST) in March 11, 2011 because of the Tohoku regional Pacific Ocean Offshore Earthquake.
After that, the power station was attacked by tsunami.
Electricity rooms and seawater pump rooms were flooded, and the cooling function became only the coolant injection of the turbine driven pump. The turbine driven pump operation increased the pressure of the suppression chamber, and it became impossible to continue the operation.

Category: Power Reactor Fukushima Daiichi »

INES-event
INES 5

Abnormal rise of radioactive dosage value at site boundary

The core damage by loss of all cooling function due to the big tsunami.-Provisional 2

Fukushima Dai-ichi Nuclear Power Station Unit 1, 2 and 3, which is in rated power operation, have automatically shut down around 14:46 (JST) in March 11, 2011 because of the Tohoku regional Pacific Ocean Offshore Earthquake.
After that, the power station was attacked by tsunami.

Category: Power Reactor Fukushima Daiichi »

INES-event
INES 3

Effect to the Nuclear Facilities from the earthquake on east area of Japan

14:46 (UTC 5:46) March 11, an earthquake hit east area of Japan. Summary of earthquake and current status of each nuclear facility is as follows;

1. Summary of Earthquake

(1) Time of Occurrence: 14:46 (UTC 5:46) March 11, 2011, Friday
(2) Epicenter: Off-Coast of Sanriku (North Latitude: 38; East Longitude: 142.9), 10km deep, M8.8

2. The status of operation at Power Stations(Number of automatic shutdown(units): 10 (as of 00:30(UTC:11:46), March12)

a. Onagawa Nuclear Power Station (Onagawa-machi and Ishinomaki–shi, Miyagi Prefecture)
(1) The status of operation

Category: Power Reactor Fukushima Daiichi »

INES-event
INES 0

AUTOMATIC SHUTDOWN OF UNIT-2 OF FUKUSHIMA DAIICHI NPP

During operation at rated power, at 3.31 p.m. on September 29, 1992 the plant was automatically shutdown by "Reactor Water Level Low" signal, and the high pressure coolant injection system (HPCI) was activated.
Successive investigation revealed that:

Category: Power Reactor Fukushima Daiichi »

INES-event
INES 0

REACTOR AUTOMATIC SHUTDOWN DUE TO INCORRECT FUNCTIONING OF A MAIN STEAM ISOLATION VALVE

During rated power operation, an automatic reactor shutdown occurred due to signal of "Neutron Flux High". As a result of investigation, it was estimated that since fastening of the rotation preventing pin had been insufficient, which had been attached at the connecting part of between a valve poppet and a valve stem in one of the 8 main steam isolation valves (MSIVs). This pin was damaged by vibration caused from steam flow and detached pilot- and main poppets plugged the main steam line causing increased reactor pressure which resulted in "Neutron Flux High".

Category: Power Reactor Fukushima Daiichi »