The Yomiuri Shimbun said the rules will take effect in July, but many objected to the regulations and said the rules may delay the use of the technology.
Cables coated with flammable materials are used in at least 13 reactors in safety zones, The Yomiuri Shimbun reported, and changing them to flame retardant materials may take years.
The NRA presented an outline of the rules to a panel Monday.
Under the new rules, Japanese nuclear plants will be required to undertake new safety measures to prevent fires, detect and extinguish fires and reduce fire damage.
The Yomiuri Shimbun said the construction rules were revised in 1975 after an accident in the United States.