The operator of the tsunami-crippled Fukushima Daiichi nuclear power plant began removing extremely radioactive spent fuel rods from a damaged storage pool of the No. 4 reactor on Tuesday, after successfully completing transfer of 22 new fuel assemblies to a more stable storage space. The operation requires extreme caution, as any damage to the spent fuel rods or the casks will cause high-level radiation. There are currently 180 unused fuel rods and 1,331 spent fuel rods in the pool. Each rod, four meters long and containing uranium, are first put into a water-filled cask inside the pool by crane to prevent accidental contact with air, which could cause overheating or contamination. Once the cask isa filled with 22 fuel assemblies, it will be lifted out and transferred to an outside storage pool about 100 meters away, which gives more stable conditions for keeping the fuel cool. Last week, Tokyo Electric Power Company (TEPCO) started operations for unused fuel rods, which are less radioactive, and the workers finished transferring the first cask containing 22 new fuel rod assemblies on Friday. The utility said there were no problems with the first round of transfer. The fuel extraction is the first critical step in a decommissioning process that could take 40 years. According to TEPCO, removal work of more than 1,500 nuclear fuel assemblies in the No. 4 unit spent fuel pool is expected to be completed by the end of next year. Unlike three other units at the plant, the No. 4 reactor did not suffer a meltdown at the time of the 2011 accident, as it was not in operation and all of its fuel rods were in a storage pool on a top floor of the reactor building. But a hydrogen explosion severely damaged the reactor building, raising concern that another major earthquake could cause cracks in the pool to leak water, which would expose the rods to the air. The Fukushima plant was devastated in March 2011, when the magnitude-9 earthquake and tsunami triggered a series of meltdowns and explosions. On Monday, International Atomic Energy Agency (IAEA) experts kicked off a review of Japan's efforts to scrap the plant. During the 10-day mission, the 19-member team is expected to inspect the decommissioning process and future plans for containing the ongoing radiation crisis. In particular, the IAEA team is focusing on the efforts to manage the contaminated water at the site and on the activities to transfer the fuel assemblies from the No. 4 reactor to a safer storage condition, team leader Juan Carlos Lentijo told a press conference in Tokyo on Monday.