The Nuclear Regulation Authority (NRA) plans to establish a system for measuring thyroid gland radiation levels of nearby residents in the immediate aftermath of a nuclear power plant accident, during a review of the government's nuclear emergency response guidelines being undertaken this fiscal year.
Revisions will likely include a requirement to measure radiation levels of children under the age of 18 and pregnant women, who are most vulnerable to radiation exposure.
Radioactive iodine released during serious accidents such as a core meltdown can cause cancer if it enters the body and collects in the thyroid gland, which is located below the Adam's apple. Children are particularly susceptible.
The NRA has reached a point at which it will soon use a highly accurate portable radiation measurement device, spurring the review. A team of experts was set up in February to begin discussions on revising the guidelines.
Officials are particularly concerned about areas where radiation levels reach 500 microsieverts per hour, which requires immediate evacuation, and those where levels continuously exceed 20 microsieverts per hour, which requires temporary relocation.
The NRA is considering mainly targeting children under the age of 18, pregnant women and nursing mothers in such areas.
Radioactive iodine-131 released in a nuclear accident halves in about eight days, highlighting the importance of taking measurements immediately after an accident to determine radiation exposure levels.
However, the measurement target until now was unclear and the response system and equipment were insufficient.
Although there have been no confirmed cases of health problems among residents living in the vicinity of Tokyo Electric Power Company Holdings Inc.'s Fukushima No. 1 nuclear power plant where a major accident occurred in 2011, only about 1,000 of the 370,000 children under the age of 18 in Fukushima Prefecture have had their thyroid gland radiation levels measured.
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