Japan’s nuclear watchdog decided Sept. 3 to instruct municipalities that host nuclear power plants to install atmospheric monitoring systems that can detect radioactive plumes in accidents and warn residents of the dangers.

Central government grants can be used to set up the monitoring stations within a 30-kilometer radius of all nuclear power plants, the Nuclear Regulation Authority (NRA) said.

A plume containing radioactive substances emerges after a reactor meltdown and can spread over wide areas via wind. The substances can contaminate the ground in rainfall.

In the event of a serious nuclear accident, the atmospheric monitoring systems will measure radiation concentrations in the air every 10 minutes to determine if a plume has indeed formed.

One system will consist of a maximum 48 measurement devices--three at each of 16 different areas from the plant.

To minimize radiation exposure among residents, the measurement figures will be shared in real time and improve the accuracy of data used to issue evacuation orders or warnings to remain indoors, according to an NRA official.

Monitoring posts have been set up across the nation to measure radiation dosage rates. However, it is difficult to determine if the radiation measured has been deposited on the ground from a plume drifting in the air.

The NRA will also instruct the municipalities to prepare emergency power sources for the monitoring systems in case electricity stops in a nuclear plant emergency.