Individual monitoring for external exposure of workers in FDNPS

The accident at the Fukushima Daiichi Nuclear Power Station (FDNPS) in March 2011 resulted in an increase in air dose rate throughout the premises and a significant change in the work environment. The main radiation source was Cs-137, which was contaminated by fallout spreading throughout the premises, and direct and scattered radiation from the reactor buildings (R/B) contributed significantly. To ensure the steady progress of decommissioning work, dose reduction measures have been implemented through facing and removal of high-dose debris. The planned dose is calculated after consideration of engineering and administrative dose reduction measures taken, such as reducing the work time, using remotely operable robots, and installing shielding. This information is set out in a radiation work admission (RWA), which is checked by the radiation control department before work is started. The effectiveness of the dose reduction measures confirmed by the results of the work is developed in the work plan for similar work to be carried out in the future, and the decommissioning work is carried out with further dose reduction.