The health and labor ministry released the preliminary results of tests on how much radiation they had been exposed to as they worked at the Fukushima Dai-ichi plant.
Three men are control room operators and the five others worked to restore power that was knocked out by the earthquake and tsunami March 11.
The government soon after the disaster raised the radiation limit for men to 250 millisieverts from the standard 100 millisieverts so workers could tackle the emergency.
Last Friday, the government said the first two workers who reached the government's limit had been exposed to more that double that amount. It reprimanded Tokyo Electric Power Co. and demanded an investigative report within a week.
The two men were exposed to 678 millisieverts and the other man 643 millisieverts
-- about 100 CT scans -- mostly by inhaling radioactive particles, NISA spokesman Hidehiko Nishiyama said.
TEPCO said those two men had no immediate health problems but would be monitored long-term because they have a higher lifetime risk of developing cancer.