Japan quake: Nitrogen pumped into nuclear reactor

The process of injecting nitrogen could take several days, engineers say

Continue reading the main story

Japan quake

• Hard wait for plant town evacuees
• Tepco shares hit record low
• Reactor leaks: Aerial view
• Aid worker's diary

Workers in Japan have begun injecting nitrogen into one of the reactors at the crippled Fukushima Daiichi nuclear plant to prevent more hydrogen blasts.

The gas is being pumped into reactor 1 of the six-unit plant which was damaged by last month's quake and tsunami.

Explosions caused by a build-up of hydrogen gas happened in three reactors in the aftermath of the 11 March quake.

Earlier, workers succeeded in plugging a gap leaking highly radioactive water from the plant into the Pacific Ocean.

The plant's operator, Tepco (Tokyo Electric Power Co), said it had injected chemical agents to solidify soil near a cracked pit of reactor 2 that was the source of the leak.

Since the earthquake knocked out cooling systems, workers have been pumping water into reactors to cool fuel rods, but must now deal with waste water pooling in and below damaged reactor buildings.

Radioactive iodine

Technicians began injecting nitrogen, an inert gas, at 0131 local time Thursday (1631 GMT Wednesday), said Makoto Watanabe, a spokesman for Japan's nuclear agency.

A Tepco official was quoted by Reuters news agency as saying that it was "necessary to inject nitrogen gas into the containment vessel and eliminate the potential for a hydrogen explosion".

Continue reading the main story

Fukushima update (6 April)

• Reactor 1: Damage to the core from cooling problems. Building holed by gas explosion. Radioactive water detected in reactor and basement, and groundwater. Hydrogen gas building up again.
• Reactor 2: Damage to the core from cooling problems. Building holed by gas blast. Highly radioactive water detected in reactor and adjoining tunnel. Crack identified in containment pit now plugged.
• Reactor 3: Damage to the core from cooling problems. Building holed by gas blast; containment damage possible. Spent fuel pond partly refilled with water after running low. Radioactive water detected in reactor and basement
• Reactor 4: Reactor shut down prior to quake. Fires and explosion in spent fuel pond; water level partly restored
• Reactors 5 & 6: Reactors shut down. Temperature of spent fuel pools now lowered after rising high

• Q&A: Health effects of radiation

The process could take several days, officials said.

The prevention of further hydrogen explosions - like those that had ripped through reactors 1 and 3 - is seen as a priority, because blasts could spew more radiation and damage the reactors.

On Wednesday engineers managed to plug the the leak from the pit in reactor 2. It is thought to have been the source of high levels of radiation found in seawater nearby.

In order to stem the leak, Tepco injected ''water glass'', or sodium silicate, and another agent into the pit.

Desperate engineers had also used sawdust, newspapers and concrete in recent days to try to stop the escaping water.

The government's top spokesman said workers could not rule out other leaks at the reactor.

Meanwhile, engineers are continuing to pump some 11,500 tonnes of low-level radioactive seawater into the sea so the more highly contaminated water can be stored in waste buildings.

Officials said this water would not pose a significant threat to human health, but local fishermen have reacted angrily.

In a letter, the largest fisheries group accused the government of an "utterly outrageous" action that threatened livelihoods.

On Tuesday, elevated levels of radioactive iodine - about twice the legal limit for vegetables - were found in small fish caught off Ibaraki prefecture to the south of Fukushima.

The government has promised compensation for the fishing industry and Tepco has already unveiled plans to compensate residents and farmers around the nuclear plant.

The number of people known to have died in the earthquake and tsunami has now reached 12,494, with another 15,107 still missing, according to police.