3/11/11 : the strongest quake in Japan’s recorded history.
two 50-mile-thick slabs of the earth’s crust heaved in a grinding 80-million-year-old conflict between tectonic plates.
The quake unleashed energy 24,000 times stronger than the atomic bomb dropped on Nagasaki in 1945, pushed part of Japan coastline 3.6 meters closer to the U.S.
the nuclear facility stood up to the quake, only to fail when the tsunami that followed
The temblor had triggered the automatic shutdown of the Dai-Ichi’s three operating reactors as designed
engineers thought they'd have to monitor the situation but that was about all
BUT the quake knocked out a transformer station about 10 kilometers away, severing the utility’s connection to the electricity grid and the power needed to keep reactor cooling systems operating.
The tsunami he was witnessing surged 2.4 kilometers inland,
The upheaval hurled about 67 cubic kilometers of ocean at Japan’s coast, or enough to flood all of Manhattan a mile deep
Within an hour the tsunami would smash into 860 kilometers of Japan’s coastline at heights the U.S. National Oceanic and Atmospheric Administration estimated as high as 24 meters.
The plant, built on a layer of rock 10 meters above sea level, was pummeled by a wave as high as 15 meters that flooded parts of the facility in six meters of seawater
What the earthquake had failed to do, the tsunami now achieved: It overwhelmed the engineering defenses at Dai-Ichi.
Seawater flooded the basements of turbine buildings and other sites, disabling 12 of the 13 back-up generators and destroying electrical switching units.
Salt water shorted electric circuitry, depriving the reactors of power for cooling and triggering a nuclear disaster
At about 3:41 p.m., almost an hour after the quake, Dai- Ichi lost alternating-current power at the three operational reactors as the generators failed.
Tepco immediately informed the government it had experienced “station blackout” as required by nuclear emergency regulations.
Without cooling, nuclear reactors are like giant kettles left to boil. Water covering the fuel rods inside begins to turn to steam, exposing the rods that melt and emit radiation upon contact with air.
We lost the ability to assess the performance of the emergency core cooling system because meters designed to check the water flow rates in the No. 1 and No.2 reactors failed.
At 4:36 p.m., less than two hours after the quake, Tepco was forced to acknowledge it had lost control of the reactors. Nine minutes later, the company notified the government.
about 24 hours after the quake, a hydrogen explosion inside the No. 1 reactor building caused radiation levels to rise.
after 62 hours after tsunami, further 2 explosions occurred
after 62 hours after tsunami, further 2 explosions occurred
A second threat emerged from spent-fuel pools, about 40- feet deep and located at the top of the reactors. The spent fuel rods also need to be cooled and covered with water to prevent them melting and emitting radiation.
Then a spent fuel pool ignited - a terrifying event, a game changer
Tepco now had three reactors without cooling systems and a fourth with a spent fuel pool fire spewing radiation into the air.
Five kilometers away at the nuclear safety agency’s offsite center, Yokota said radiation levels set off a constant warning ping at detectors in the office
The stopgap methods to cool the reactors and spent-fuel rods were having little effect, he said, with the use of salt water adding a further complication from corrosion.
“Even as firefighters pumped water into the reactors, the levels wouldn’t rise, and you can’t determine the reason without getting inside
On March 29, Tepco was able to restore lighting in the control room of the No. 4 reactor as engineers slowly made progress in fighting the crisis.
No comments:
Post a Comment