Awwal 02, 1432 H/April 6, 2011, SPA -- Japan began pumping nitrogen gas into a crippled nuclear reactor, refocusing the fight against the world's worst nuclear disaster in 25 years on preventing an explosive buildup of hydrogen gas at Fukushima Daiichi power plant, Reuters reported. Workers started injecting nitrogen into the containment vessel of reactor No. 1 on Wednesday night, following a morning breakthrough in stopping highly radioactive water leaking into the sea at another reactor in the six-reactor complex. "It is necessary to inject nitrogen gas into the containment vessel and eliminate the potential for a hydrogen explosion," an official of plant operator Tokyo Electric Power (TEPCO) told a news briefing. The possibility of another hydrogen explosion like those that ripped through reactors 1 and 3 early in the crisis, spreading high levels of radiation into the air, was "extremely low," he said. But TEPCO suspected that the outside casing of the reactor vessel was damaged, said the official. "Under these conditions, if we continue cooling the reactors with water, the hydrogen leaking from the reactor vessel to the containment vessel could accumulate and could reach a point where it could explode," he added. Although engineers succeeded after days of desperate efforts to plug the leak at reactor No. 2, they still need to pump 11.5 million litres (11,500 tonnes) (3.04 million U.S. gallons) of contaminated water back into the ocean because they have run out of storage space at the facility. The water was used to cool overheated fuel rods. Nuclear experts said the damaged reactors were far from being under control almost a month after they were hit by a massive earthquake and tsunami on March 11. The growing concerns of nearby South Korea and China about radioactive fallout from Japan were underscored when China's health ministry reported trace amounts of radioactive iodine in spinach in three Chinese provinces. The two western neighbours of Japan have reportedly complained they have not been fully informed about TEPCO's plans to release radioactive water into the Pacific Ocean. "We are instructing the trade and foreign ministries to work better together so that detailed explanations are supplied especially to neighbouring countries," Chief Cabinet Secretary Yukio Edano told a news conference on Wednesday. Experts insisted the low-level radioactive water to be pumped into the ocean posed no health hazard to people. "The original amount of radioactivity is very low, and when you dilute this with a huge body of water, the final levels will be even lower than legal limits," said Pradip Deb, senior lecturer in Medical Radiations at the School of Medical Sciences, Royal Melbourne Institute of Technology University. The government is preparing to revise guidelines for legal radiation levels, designed for brief exposure to high levels of radiation in emergencies and not cumulative absorption, for people living near the damaged plant. Workers are struggling to restart cooling pumps -- which recycle the water -- in four damaged reactors. Until those are fixed, they must pump in water to prevent overheating and meltdowns, but have run out of storage capacity for the seawater when it becomes contaminated. Radioactive iodine detected in the sea has been recorded at 4,800 times the legal limit, but has since fallen to about 600 times the limit. The water remaining in the reactors has radiation five million times legal limits. Martin Virgilio, a top official for the U.S. Nuclear Regulatory Commission, said at a House of Representatives hearing that the NRC did not believe that the core of Fukushima's reactor No. 2 had melted down. Earlier, Democratic congressman Edward Markey had said the NRC informed him that the core had become so hot it had probably melted through the reactor pressure vessel.
