Q + A-hazards at each reactor of the Japan is devastated by plant - Reuters

Mayumi Negishi and Chizu Nomiyama

TOKYO, April 14. Thu April 14, 2011 6: 48 a.m. EDT

(TOKYO, April 14, Reuters) - the Central Daiichi Fukushima nuclear in the centre of the Japan crisis has six reactors. The plant is operated by Tokyo Electric Power Co (TEPCO).

The following summarizes the main risks as Japanese engineers struggle to deal with the worst nuclear crisis since the collapse of Chernobyl 1986:

WHAT IS THE OVERALL SITUATION?

Two of the reactors are considered safe, but the other four are still volatile. The nuclear safety agency said that the temperature and pressure in all reactors are stable.

Workers have managed to curb chain reactors at no. 1, no. 2 reactions and No.3 resulted after the earthquake struck, but they were unable to cool the reactors in some fuel melted inside reactor cores.

Engineers are now trying to cool the reactors at the point where they can be turned off. Until the cooling pumps or alternatives, are online to continuously cool reactors, workers are obliged to periodically inject new water to maintain the freshness of the fuel, but that creates the most contaminated water.

The immediate challenge is to transfer and store the contaminated water, while at the same time as much as possible the spread of radiation always leaking into the atmosphere and the sea. Currently, workers do not have access to the cooling systems in reactors, no. 1, no. 2 and no. 3.

So far, eight workers suffered injuries of radiation at the Daiichi plant. All have been released from the hospital.

WHAT ARE THE RISKS AT EACH REACTOR?

-REACTOR No 1: 460 - MW (manufacturer GE)

Reactor fuel can melt the most, with TEPCO estimate that 70 per cent of fuel may have been damaged, judging by the released radiation. Detection of neutron in mid-March beams may also mean that flashes of nuclear reaction occurred when the fuel was at its warmest.

Pumps are now injection of freshwater in the reactor and workers hope to install independent power line for pump to another, in the case where an aftershock knocks out the power again.

Workers are also injecting nitrogen into the reactor in the hope of avoiding a repeat of a breath of hydrogen on 12 March, which could endanger the lives of workers, blocking access in the plant and spread rained radiation in the environment.

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