Radiation Dose measured at exhaust stack monitor of Fukushima Daiichi Nuclear Power Station

Radiation dose

• * Wind direction and wind speed are measured at the same level as the top of the exhaust stack by the weather measuring device on the west side of the off-site parking lot.
• * In case of heavy rain, wind direction and wind speed may not be measured accurately.
• * In the case that wind speed is less than 0.5 m/s, wind direction is shown as “-“ and wind speed is shown as “CALM”
• * From October 1st, 2024, location of the weather measuring device has been changed from the west side of the seismic isolation building to the west side of the off-site parking lot.

Announcement

• *On March 30, 2021, archives were updated. Please click “Past measurement results (on and after March 25, 2021) are found here” for additional archives.
• *The monitoring equipments on the Unit 1 to 4 exhaust stacks are currently out of use due to the accident.
• *Data may be missing due to regular inspection or cleanup work.

• Past measurement results (on and after March 25, 2021)

Exhaust stack

An exhaust stack is a facility to release the air inside the building at the power station and the exhaust gas enerated by vacuuming the condenser. Unlike a regular chimney, the air used inside the building is released from the exhaust stack. As the released air contains a small amount of radioactive materials, an activated carbon type noble gas hold-up device and filters are used to mitigate its impact on the environment.

Exhaust stack monitor

An exhaust stack monitor is an equipment to measure the radiation dose of the air released from the power station to the environment.

Measurement unit: cps (count per second)

1 cps represents that 1 radiation ray was measured in 1 second by a radiation counter.