at 16:12 jst, self defence force (sdf) chinook helicopters were preparing to pour water on unit 3, where white fumes rising from the building was believed to be water boiling away from the fuel rod cooling pond on the top floor of the reactor building, and on unit 4 where the cooling pool was also short of water. the mission was cancelled when helicopter measurements reported radiation levels of 50 msv. at 21:06 pm jst, the government reported that major damage to reactor 3 was unlikely but that it nonetheless remained their highest priority.