Television footage showed dozens of operatives, all wearing white protection suits, atop the heavily damaged building at unit No. 4, extracting a fuel rod with a crane.
The plant’s operator, Tokyo Electric Power Co. (TEPCO) said earlier the operation was planned for some time this month.
The company said two rods, each measuring around four metres (12 feet), are to be taken out of the fuel pool.
Today’s operation was the first time TEPCO has been able to remove any nuclear material since disaster struck at the plant in March 2011.
Reactors No. 1, 2 and 3 all melted down, but reactor No. 4 was empty when the tsunami crashed ashore.
However, a disabled cooling system led to the fuel pool-where both used and unused fuel was kept-boiling.
That resulted in an explosion after a build up of hydrogen inside the reactor building.
“The company will examine the extent of corrosion on the fuel rods, which may have been caused by the sea water that workers had to use to keep the temperature down,” a company spokeswoman said, without confirming the operation took place on today “for nuclear security reasons”.
Television crews used helicopters to film the operation, defying requests from TEPCO.
More than 1,300 used fuel rods and over 200 unused ones were in the water pool at unit No. 4 when the tsunami hit, the spokeswoman said.