Workers have entered a reactor building at Japan’s Fukushima nuclear plant for the first time since it was damaged by March’s earthquake and tsunami.

Plant operator Toyko Electric Power said a dozen staff are installing new ventilation systems in reactor number one to filter out radioactive particles from the air.

Toyko Electric president Masataka Shimizu has met with evacuees forced out of their homes by the disaster.

Shimizu received a stinging rebuke when he and fellow executives visited a shelter inside the 20 kilometre exclusion zone set up around the stricken plant.

Evacuees lambasted Shimizu, calling him a liar for previous company claims that the atomic plant was earthquake-proof.

The TEPCO boss then bowed in apology to beg forgiveness.

Fukushima started to leak radiation when the devastating March 11 tremor knocked out its cooling systems.

The earthquake and tsunami killed at least 14,000 people, left 11,000 missing and destroyed thousands of homes.

Japan should be celebrating its extended spring break, known as Golden Week.

But volunteer organisations are reporting that thousands of people are rushing to sign up to help clear the wreckage on the country’s northern coast.