TOKYO (Kyodo) -- The operator of the Fukushima Daiichi nuclear power complex said it retrieved the second sample of melted fuel Wednesday from one of the reactors hit by a massive earthquake and tsunami over a decade ago.

The debris extracted from the No. 2 reactor by Tokyo Electric Power Company Holdings Inc. is believed to weigh 3 grams or less, out of the estimated 880 tons remaining in the Nos. 1 to 3 units that melted down during the nuclear crisis that began in March 2011.

TEPCO hopes to expand data on the solidity and components of the debris to come up with ways to remove the rest effectively and store it safely.

The retrieved sample is scheduled to be sent from Fukushima Prefecture to a research institute in neighboring Ibaraki Prefecture after its weight and radiation levels are measured.

"We hope it will further contribute to the accumulation of knowledge toward removing the debris among other works for decommissioning," Chief Cabinet Secretary Yoshimasa Hayashi told a press conference.

TEPCO inserted a retrieval device, functioning like a fishing rod, into the containment vessel on April 15, and grabbed the sample two days later with the gripper on its tip at a location 1 to 2 meters closer to the center than in the previous retrieval project.

After confirming that radiation levels were equivalent to 0.1 millisievert per hour at 20 centimeters from the sample, workers completed the retrieval at 10:15 a.m. Wednesday by collecting an aluminum container carrying the debris, according to TEPCO.

Last November, TEPCO retrieved the first melted fuel sample, weighing 0.7 gram, from the No. 2 unit. The sample analysis revealed that it contains uranium and zirconium, used as cladding for fuel rods.