Japan halts Hamaoka nuclear plant

Engineers worked in small teams on 10-minute shifts to limit their exposure to the radiation

The operator of Japan’s quake-hit Fukushima Daiichi nuclear plant has released new images of the interior of the crippled No 1 reactor building.

The photos were taken on Thursday after workers were allowed in for the first time to install a ventilation system.

Work is continuing to restore vital cooling systems at the plant, with extra water being pumped in to submerge containment vessels and cool fuel rods.

The cooling systems were knocked out by the 11 March quake and tsunami.

Explosions took place at four of the plant’s six reactors and engineers have been working to stabilise the plant ever since.

A 20km (12 mile) mandatory evacuation zone has been put in place around the plant because of concern about radiation levels – forcing some 80,000 residents to leave their homes.

A photograph taken by one of the 12 workers to enter the No 1 reactor building on Thursday, showed an engineer in protective clothing carrying a radiation monitor mounted on a pole.

The men worked in small teams on 10-minute shifts in order to limit their exposure to the contaminated atmosphere while they installed the ventilation system and filters.

Another photograph shows four air ducts and behind them a pale green door leading to the exit.

The ventilation system is venting contaminated air and returning clean air into the reactor building

The power station operator, Tepco, said it will take about three days to vent the contaminated air, filter it, and return purified air to the building.

The radiation levels inside the reactor buildings must be lowered before new cooling systems can be installed.

In the meantime extra water is being pumped in to the No 1 reactor building as part of a new cooling strategy, approved by Japan’s nuclear safety agency.

Tepco said it expects the additional water to cool and decrease pressure in the containment vessel.

The firm said it plans to complete construction of the new cooling system for the No 1 reactor in late May or early June, local media report.

Engineers aim to achieve a cold shutdown of the plant by the end of the year, but some doubt whether this target can be achieved.

Restoring the cooling systems is seen as vital to bringing the crisis under control, as the current emergency measure of continually injecting water from outside has created pools of highly radioactive water within the plant.

Water with lower levels of contamination was released into the sea last month so the more highly contaminated water could be moved to on-site storage.

A total of 14,841 people are confirmed to have been killed by the earthquake and resulting tsunami. Another 10,063 remain missing, according to the latest police figures.

Japan’s recovery bill has been estimated at $300bn (£184bn) – making this already the most expensive disaster in history.

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