Tokyo - An atomic research lab in northern Japan has reported a radiation leak that may have affected about 55 people, though none have been hospitalised and no impact was expected outside the facility, the lab says.
The Japan Atomic Energy Agency said the accident occurred on Thursday in its Hadron experimental facility at the Japan proton accelerator research complex in the town of Tokaimura, where at least two previous radiation accidents have occurred.
Researchers were trying to generate particles by directing a proton beam at gold when their equipment overheated, causing the evaporation and release of radioactive gold, the government-run Jaea said in a statement on Saturday.
The leak originally was thought to have been contained inside the lab and when a ventilation fan was switched on the radiation spread, it said.
The Jaea said it was studying the potential environmental impact from the radiation leak, but did not expect any effect on surrounding areas.
Six researchers were found to have been exposed, Kyodo News Agency reported.
Initial tests showed that another 24 likely had been exposed.
Japan's nuclear industry has been in crisis since the March 2011 accident at the tsunami-hit Fukushima Dai-ichi nuclear plant, the country's worst-ever atomic energy disaster.
Most of Japan's nuclear plants remain closed after they were shut down for safety checks.