A Japanese atomic plant operator Wednesday removed an unused fuel assembly on a trial basis at a damaged power station for the first time since last year’s disaster while another company planned to restart a reactor, local media reported.

Reactor 4’s building at the Fukushima Daiichi Nuclear Power Station holds a storage pool filled with 1,535 nuclear fuel rod assemblies, including 204 unused ones.

Left uncovered

The pool has been left uncovered since a hydrogen explosion last year blew off the upper part of the outer wall of the containment building.

Chie Hosoda, a spokeswoman for the plant’s operator Tokyo Electric Power Co, said the operation would help understand the condition of other fuel assemblies.

She declined to comment on reports that the operator planned to remove another fuel assembly Thursday.

Experts warned that the spent fuel rods at reactor 4 could trigger a catastrophe despite the government’s declaration in December that the plant had been brought under control.

A March 2011 earthquake and tsunami led to meltdowns at three of its six reactors. But each of the three units holds fewer assemblies than reactor 4.

The operator will start to remove spent fuel rods from the plant in December 2013.

Meanwhile, Kansai Electric Power Co planned to reactivate a nuclear reactor in western Japan late Wednesday, the second since last year’s atomic disaster, despite strong public opposition. Unit 4 at the Oi Nuclear Power Plant was scheduled to start power transmission Saturday and be in full operation on July 25, the JapanneseKyodo News agency reported.

Kansai Electric Power Co restarted reactor 3 on July 1.

In mid-June, Prime Minister Yoshihiko Noda approved the restart of the two reactors over public opposition and experts’ warnings of fault lines near the complex.