Five workers at a nuclear research facility in Ibaraki Prefecture, northeast of Tokyo, had their gloves and shoes exposed to radioactive materials Tuesday, the operator of the facility said.
The Japan Atomic Energy Agency said up to 24 becquerels of radioactive materials were found inside the noses of three of the workers, prompting the agency to check whether they face the danger of internal exposure to radiation.
An official at the agency said it is hard to say the detected level is "extremely small," although it does not pose an immediate threat to their health.
There were no radiation leaks outside the fuel research building of its Oarai Research & Development Center, the agency said.
A bag used to cover a container for nuclear fuel materials tore when the workers were inspecting another container that included it, according to the agency.
The workers -- all men in their 20s to 50s -- wore masks to cover their mouths and noses but could have inhaled the radioactive materials. None of the five has complained of ill health, the agency said.
Masato Kato, a senior official at the agency, said the workers were following "ordinary procedures" during their inspection work.
Nuclear materials used for research are stored at the building, where researchers handle plutonium and uranium to conduct studies on new types of fuel for a fast reactor.
The Oarai Research & Development Center is home to the High Temperature Engineering Test Reactor and the Joyo experimental fast reactor that the agency aims to restart.
