Due to the Earthquake with an intensity of 8.9 in Rictor scale, which was one order of magnitude higher than the Design basis of the Reactors, all the 11 Reactors which were in the vicinity, including the 3 operating at Fukushima site, promptly shut down as per design requirements.
Due to this earthquake, there was no damage whatsoever to any of the 11 Reactors, some of which were operating and some were under planned shut down. This establishes the fact that the Nuclear Reactors can be designed and operated safely for quake intensities as high as 8.9 with quakes in close vicinity, without any damage to any structure or equipments and piping.
The instruments and emergency power systems also performed to precision as per design requirements.
The cooling of the Reactors was instantly taken over by the emergency DG sets when the power grid collapsed due to the earth quake / tsunami.
But the subsequent tsunami which hit the Fukushima coast after about 45 minutes of the quake, flooded the DG sets which were kept at about 6 m elevation in tune with the design basis tsunami height of 5 m. But since the actual tsunami was about 15 m high, the DG sets were flooded. This was the root cause of the whole problem.
Since there were no portable DG sets near the plant site with Plug suitable for the emergency power Socket at the plant, there was inordinate delay in resuming the Reactor core cooling, which is very critical in the initial few hours.
This resulted in the partial damage to the fuel in all the three Reactors and there was Hydrogen generation due to the hot Zircolloy clad reaction with water. This Hydrogen which was to have been recombined and released in small quantities as and when they are generated as per the design basis were not released for reasons not yet identified.
This resulted in accumulation of Hydrogen at the top of the building outside the Reactor vessels. When the concentration of Hydrogen reached the threshold level, auto ignition of Hydrogen took place releasing the accumulated steam which contained radioactive substances into the air.
Subsequently, external cooling was done using sea water. This sea water coming out of the core had some radioactive substances like Cesium. But since the fuel is not leacheable with sea water, the radioactive level in the sea water discharged from the Reactors was very low. Part of this water got into the trench and leaked / over flowed back to the sea.
The air borne radioactive particles, which contained mostly Iodine and Cesium settled down mostly in the 30 KM vicinity, with traces carried away as far away as 150 KMs.
The people in the vicinity were promptly evacuated when it was clear that the emergency core cooling could not be restored and the external cooling method was also not effective during the initial stages. It is only the general public and media perception taht the authorities delayed the evacuation. By delaying the evacuation delibeately, what are they going to gain ? No one wants to think rationaly.
The core cooling systems in all the 3 affected Reactors were completely restored within few days and the radioactive discharge to the environment completely stopped.
As of now, the removal of radioactive substances ( mostly Cesium ) from the contaminated sea water which has been accumulated within the Reactors is in progress using a makeshift treatment plant.
Though one can detect the presence of Cesium in soil in about 10 KM radius even today, the concentration levels are very low for it to cause any health hazards. The Iodine which contributed to the major quantity of radiation discharge into the atmosphere is almost non existent now due to its half life of just 8 days as against 30 years for Cesium.
The only problem to be tackled today is to ensure that the Cesium contaminated food products do not get into the market. Adequate care has been taken in this direction.
It shall be clearly understood that the Cesium particles are spread out here and there and they are not present uniformly every where.
The radiation exposure to the human beings due to the presence of Cesium particles here and there is not at all a cause for concern. This shall be clearly understood by the people.
The radiation at a distance few meters away from the Cesium particle is almost nil. Hence, presuming that all the time the total radioactivity of the Cesium particle is attacking all the people in the vicinity uniformly, and estimating the probability of cancer based on this misconception is total absurdity.
The Reactors are expected to be made accessible for the assessment of the extent of core damage in the next few months.
After this, the method of removal and disposal of the damaged fuel will be done. It is not an insurmountable task given the advanced remote controlled Robots available today. Very soon it is going to be done in Chernobyl also.
The general public, about 50,000 of them who are yet to be relocated back around the plant site, can be rest assured that majority of them, baring few thousands who were within say 5 KM will be allowed to go back to their home.
The long term consequences of this accident are almost negligible. This is coraborated by the much lower cancer incidences in Hiroshima / Nagasaki and the Chernobyl compared to that postulated and feared earlier.
The quantity of radioactive substances, especially the problematic Cesium, is also much less in the Fukushima accident compared to the Horoshima / Nagasaki and Chernobyl.
So, the Readers may take a fresh look at the entire events keeping aside the perception based risks widely spread out by the media. People may recollect the media hype created at the time when the steam cloud which was moving out of the Reactors were dubbed as “radiation clouds” and it was expected to contaminate USA, China, Russia, India and every where !
No one really wants to know what happened to that “radiation cloud” and how many people were killed !.
In the whole process NOT A SINGLE soul has died due to this nuclear related accident. .
(However, Readers may note, at least 15,813 people were killed as a result of the earthquake and tsunami while 3,971 others remain still missing).
The media always writes about the death toll of the stunami while writing about the Fukushima accident. It is a deliberate move to malign the nuclear industry.
The Readers must distinguish between the tsunami effect and the nuclear accident.
Are Regulators And The Nuclear Industry Applying The Valuable Lessons Learned From Fukushima?: Arnold Gundersen (Fairewinds Associates)