Fukushima isn't Chernobyl in several critical ways, particularly in how the reactors were constructed, the kind of damage done, and operational errors in dealing with both reactors:
There is a key difference, he says, in the type of explosions at Fukushima and Chernobyl. At the Ukrainian plant 25 years ago, he explains, a series of operating errors and misjudgments resulted in an explosion and fire releasing toxic smoke that contained parts of the fuel rods and graphite particles into the atmosphere. At Fukushima, however, there have only been steam explosions.The geographical differences are key in just how many people are affected by the spread of radiation downwind; because the prevailing winds take airborne particles from Fukushima out over the Pacific Ocean, the population affected by radiation is much lower.
Also, there have been no reported deaths so far due specifically to radiation at Fukushima, where at least five workers have died from other operational mistakes. The initial explosion at Chernobyl killed two workers, and then 28 of the firemen and emergency clean-up workers died in the first three months after the explosion because of radiation exposure.
Still, Oka concedes that it is very difficult to tell exactly what percent of the fuel rods have melted at Fukushima, and therefore how much radiation has actually leaked.
"Fukushima has its own unique risks, but comparing it to Chernobyl is going too far. Fukushima is unlikely to have the kind of impact on the health of people in neighboring countries, the way Chernobyl did," nuclear specialist Kenji Sumita at Osaka University told Reuters.
Geography exacerbated the Chernobyl incident. While that radiation spread to the Ukrainian countryside and blew over Europe, much of the Fukushima radiation has dispersed over the Pacific Ocean. Greenpeace’s Mr. Myllyvirta says the Fukushima crisis would be much worse if Japan was a landlocked country.
TEPCO is continuing to attempt to bring the situation under control, and aftershocks continue to shake the region and can affect efforts to bring outside power to the reactors so that coolant systems can be operated to keep the reactors and the spent fuel pools cool. The aftershocks shut down the coolant systems for about an hour, but were restarted. This will be an ongoing problem and concern given that significant aftershocks are expected to continue for the next several months. The backup systems that have been put in place aren't protected against a possible tsunami, which is what caused all the problems at Fukushima to cascade into the troubles that TEPCO are dealing with now.
The overheating reactors at Fukushima Daiichi have two layers of backup functions in case of a power cut—diesel-powered generators and emergency fire pumps—so they can continue receiving cooling water. But these functions require workers to turn them on manually. This became a problem Monday as a tsunami warning forced all workers to move to a shelter on the plant grounds.UPDATE:
"These disruptions must be solved rapidly as a prolonged lack of cooling would easily end the respite they have managed to maintain," said Tetsuo Iguchi, a professor of radiation engineering at Nagoya University.
Two more earthquakes shook Japan early Tuesday, but there were no immediate reports of damage or injuries, with the levels of magnitude smaller than recent aftershocks that have struck.
The Japan Meteorological Agency said the first quake hit the Fukushima area at 8:06 a.m. with a magnitude of 4.0. The second quake struck in the ocean east of Tokyo area at 8:08 a.m. with a magnitude of 6.3, shaking the downtown Tokyo area.
Despite the lesson from the earlier quake and tsunami that rendered the plant's backup cooling systems fully dysfunctional, officials acknowledge the temporary cooling functions at the plant aren't prepared for large tsunamis.
The seven point INES rates nuclear emergencies based on how far the radiation has spread beyond containment. With Fukushima, while each of the 4 damaged reactors are individually rated as level 5 emergencies, the combined situation rates a 7 - due to the complexities of dealing with containment, the spread of radiation outside containment facilities, and the immediate region.