An effort to remove the hazardous spent fuel rods in the storage pool teetering above reactor 4 at the crippled Fukushima No. 1 nuclear complex might start as soon as Tuesday, a source close to Tokyo Electric Power Co. said.

Fuel extraction operations began Nov. 18 with the removal of 22 fresh fuel assemblies, which are easier to handle than spent fuel. Next up, however, is a batch of 22 spent fuel assemblies, which could heat up and release radiation if damaged during the process.

The project is part of a yearlong effort to remove more than 1,000 assemblies from the spent fuel pool, which was deemed one of the major hazards in the early stages of the Fukushima crisis, which saw the cores of reactors 1 to 3 melt in March 2011.

Unit 4 was badly damaged by a hydrogen explosion but avoided a meltdown because it had already been de-fueled for scheduled maintenance work.