Previous exposures to radiation have been through airborne contact or direct exposure to X-rays and gamma rays being emitted from the reactor facilities.

Water seeped into the boots of the two workers, coming into contact with their skin. A third worker was protected by his clothing and was not hospitalized.

It is not clear if the men also suffered conventional burns because of heat from the water. Experts said the damage could be mitigated by thoroughly washing the workers’ skin to remove any radioisotopes that were present. Any radiation burns that might have occurred would then be treated like normal thermal burns.

Both men, one in his 30s and the other in his 20s, were exposed to about 180 millisieverts of radiation. The third worker, who was not hospitalized, was exposed to 173 millisieverts. The Japanese government raised the maximum permissible exposure level at the plant to 250 millisieverts per year, so all three are near their maximum cumulative dose.

Workers at the facility stopped spraying water on the No. 3 reactor overnight Thursday but expect to begin again Friday morning.

Meanwhile, the United Nations meteorological agency said weather conditions were changing at the site and that, by Saturday, prevailing winds again would be blowing any radiation released by the plant out to sea.