The situation at the Fukushima Dai’chi nuclear power plant of Japan has just been reported to be worse than previously estimated, but still nowhere close to Chernobyl. A couple of days back, on 12th April, the Japanese Nuclear and Industrial Safety Agency reviewed the situation and updated their previous rating of 5 to a maximum of 7 on the International Nuclear and Radiological Event Scale (INRES). The only incident in history to get the rating of 7 is Chernobyl.
What is INRES?
The INRES scale is a scale used by International Atomic Energy Agency (IAEA) to gauge and compare the different incidents of radioactive spillage or similar disasters. A low rating on the scale involves the misplacement of small doses of lightly radioactive substances and small radioactive doses, which can be easily washed off’. A high rating, like that of Chernobyl, involves a widespread spillage or release of high amounts of radioactive substances into the air or into the sea. The rating can be done for an entire disaster site or for certain specific areas of the site.
Ratings since the tsunami
The INRES ratings have changed a number of times since the tsunami struck the plant. Earlier each of the cores had been rated with a 5, meaning that they posed a danger of emitting large amounts of radioactive material, if not handled with utmost care. The recent ratings were given for the entire plant, and not just of the reactors, adjusting to the spread of radioactive materials in the air and the dumping of the same into the neighbouring sea. It also recognises the fact that the entire area needs to be treated with considerable caution and not just the reactor cores.
Comparisons with Chernobyl
Given that, before Fukushima, Chernobyl was the only incident to score a 7 on this scale, the comparisons are inevitable, but, many experts feel, unfair. Most of the radioactive material released has been towards the Pacific Ocean, where it has no chances of poisoning human habitat areas. Further, the radioactive wastes that have been dumped into the ocean pose quite little threat due to the high degree of dilution. This has called into question the validity and the use of the rating system, especially when it has high potential of misleading the public.
Cleaning up the mess
Cleaning up the Fukushima mess may take more than 10 years, experts feel. The immediate concern is cooling the core with sufficient water, all the while keeping it submerged. This involves pumping water in and out periodically, and then disposing the lightly radioactive water into the sea. The core is kept under about 20 feet of water, which also helps in shielding the radiations from the core. Japanese authorities are also considering using robots for cleanup of the innermost parts of the reactors, but nothing has been implemented as yet.
The situation is more stable than a few days back and the reactors are no longer throwing up new surprises. The cooling system is being repaired and should be operational soon.