Authorities will announce July 19 that the first goals toward stabilizing the Fukushima No. 1 nuclear power plant have been largely achieved, despite a rickety system that has barely kept the reactors cooled.
Authorities will announce July 19 that the first goals toward stabilizing the Fukushima No. 1 nuclear power plant have been largely achieved, despite a rickety system that has barely kept the reactors cooled.
The government and Tokyo Electric Power Co. said the reactors are being cooled on a stable basis via a circulating cooling system, which uses contaminated water after treating it.
But water leaks and other problems have frequently forced the water purification unit--the core of the circulating cooling system--to shut down since it started operations on June 17.
TEPCO, the plant's operator, on April 17 released a two-stage road map for bringing the Fukushima plant under control.
Step I called for reactors to be cooled on a stable basis within three months, while Step II called for reactors to be brought to cold shutdowns by January at the latest.
Government and TEPCO officials said the circulating cooling system has kept the reactors cooled without increasing the amount of radioactive water at the site.
They will announce that nitrogen injections have almost completely eliminated the risk of hydrogen explosions, and that the release of radioactive materials beyond the plant premises has been kept to a minimum.
The government will consider lifting an evacuation stand-by zone where residents have been told to be ready for evacuation in an emergency.
The circulating cooling system was introduced as a stopgap measure after TEPCO in May abandoned plans listed in the April road map to fill the containment vessels with water and restore the plant's original cooling systems.
The containment vessels, which were damaged more seriously than expected, could not hold water, and high radiation levels prevented work in reactor buildings.
In the Step II phase, TEPCO plans to repair damaged parts of the containment vessels to submerge the melted fuel.
The unprecedented circulating cooling system purifies highly radioactive water, which is generated when the melted fuel is cooled, and returns the treated water to reactors.
However, the capacity utilization rate of the core water purification unit has remained below the initial target of at least 80 percent of up to 1,200 tons per day. The causes of the shortfall have not been identified.
Restoring the plant's original cooling system is not the only challenge for TEPCO.
At least 31 workers toiling in the summer heat in full face masks have suffered heatstroke.
TEPCO included measures to prevent heatstroke, such as opening an emergency medical care office and increasing resting rooms at the site, when it reviewed the road map on June 17.
But those measures have been insufficient.
Large amounts of radioactive debris remain in the reactor buildings because workers cannot stay there for a long time due to high radiation levels.
Elsewhere on the plant premises, the debris, which was scattered during hydrogen explosions early in the crisis, is being removed and stored in containers.
TEPCO is also adding facilities to measure the amounts of radioactive materials in the air around the plant because more information is necessary to allow evacuees to return.