A ventilation fan with no filters was used for three days after a radiation leak at an atomic research laboratory in Tokai, Ibaraki Prefecture, the lab’s operators said Tuesday.
This means that radioactive substances may have continued to escape from the facility after the operators reported the leak to regulators on the night of May 24.
The radiation leak occurred around 11:55 a.m. May 23 at the Japan Proton Accelerator Complex (J-PARC).
The fan started around 5:30 p.m. May 23 to reduce radiation levels inside the complex and continued running until 11 a.m. May 26, according to the operators, the Japan Atomic Energy Agency and the High Energy Accelerator Research Organization.
Yujiro Ikeda of J-PARC said that an order to stop the fan failed to reach officials at the complex.
The fan was also used for about 15 minutes starting at 3:15 p.m. May 23.