If you thought that the evaluation of the seriousness of a nuclear accident was scientifically rigorous, then it seems you were wrong; it is (also) a highly political matter. Thus, only after the local elections of 10 April did the Japanese government recognise that the Fukushima Daiichi distaster reached level 7, the highest level on the INES scale 
Tokyo had first announced, against all evidence, that it was just an accident of level 4 (which produces only “minor release of radioactive material probably not requiring the implementation of planned contra-measures other than the supervision of local foods”). This ranking was maintained between 12 March and 18 March, during the phase of intense release of radioactivity (the leaking of radioactive gases, explosions, fire ..)! Then, Tokyo claimed the accident did not exceed the level 5 (ie. “limited” radioactive leaks). This succession of lies did not prevent the governing party losing the local elections (however, its defeat might have been even more severe if the truth had been told earlier). The government must now prepare the population for a sustainable nuclear crisis: the company responsible for the site, Tepco, announced - with no guarantee! - that it will take 6 to 8 months to shut down the plant (in terms of its decommissioning, no one knows what will happen).
French nuclear authorities, keen to appear to be acting transparently without actually doing so, let it be known that the accident Fukushima was level 6. Yet instead of rejoicing in the belated openness of their Japanese counterparts, they are now being rather more circumspect.
Everything in effect lies in the symbolism. No one “shows” that means the severity level 6 (“more than 5, less than 7” in the delicately chosen words of one expert questioned about this on television). We can therefore expect further claims that catastrophe will be avoided. In contrast, level 7 inevitably evokes Chernobyl. It must be recognised therefore that we are dealing with a disaster, and have been so from the start. It must also be admitted that a nuclear catastrophe can occur in one of the most technologically advanced countries in the world.
However imperfect it may be, the information provided in Japan fully justifies the reclassification of the accident at level 7 on the INES scale. However, reflecting the importance that this question has been given by the nucleocrat lobby, the International Atomic Energy Agency (IAEA) has been mobilised. Tokyo’s admission was followed by a veritable media offensive to say that we could in no sense compare Fukushima to Chernobyl, because the radioactivity released so far (but what of tomorrow?) is only 10% of that which leaked in 1986.
It is very difficult to compare the emission levels of radioactivity when the official figures supplied are so lacking in credibility and are also incomplete. The Japanese authorities have not disclosed the assumptions and calculations underlying their conclusions. Only air emissions have been taken into account and not the very important marine discharges. The strength of the radiotoxicity can not be estimated because too few radionuclides have been taken into account. It is extremely urgent that in Japan independent organisations be allowed to make independent measurements, as Criirad does in France. International antinuclear networks should help to develop the necessary equipment.
All that being said, Fukushima is worse than Chernobyl in several ways. Firstly, because it involves four reactors at the same time, not one (a scenario that had never been considered by international authorities). Because the tonnage of nuclear fuel present at the facility in Fukushima Daiichi is much larger (1760 tons instead of 180 tonnes in reactor No. 4 at Chernobyl). Also because it can not be attributed to the irresponsibility of ’sorcerer’s apprentice’ engineers (as was done in 1986). It has also defied all the assurances given about the risks (the possibility of an earthquake of force 9 in this part of Japan had been ruled out). And because it has lasted much longer - and continues to release radioactivity. Finally, it occurred 25 years after the traumatic experience of Chernobyl, in a plant supposed to be much more secure - and in Japan, not in a state in terminal crisis like the then Soviet Bielorussia/Ukraine.
By lying for a month about the severity of the accident, the Japanese government has not taken the measures it should have to protect the public and workers working on the site. In deliberately clouding the issue, French and international nuclear authorities have tried to prevent any real debate on energy policy. A straightforward denial of the right to information and democratic choice is the real problem.
On April 3, activist Kazuyoshi Sato spoke at a rally held near the site of the nuclear crisis. “I have engaged in the activities of our Fukushima Network for Denuclearization for more than 20 years, but we are now confronted with the ongoing nuclear disaster”. 
We do not want to face the same bitter reckoning in relation to other plants, whether in France, Japan or elsewhere. We must abandon nuclear power. Now.