Katsutoshi Chikudate, a senior executive of Tokyo Electric Power Co. (TEPCO), will replace Masataka Shimizu as the company head, the Yomiuri newspaper said.

The Fukushima Daiichi nuclear power plant was heavily damaged by a powerful earthquake and a subsequent tsunami in mid-March, which resulted in massive radiation leaks. About 80,000 people have been evacuated from a 12-mile zone around the plant, where radiation levels soared following the quake.

TEPCO has come under harsh criticism, including from Japan's Prime Minister Naoto Kan, for insufficient efforts to tackle the nuclear crisis, the worst since the 1986 Chernobyl disaster.

Shimizu, was also criticized for staying in Tokyo for weeks before visiting the Fukushima prefecture in mid-April and apologize to those affected by the disaster, the website said. In March, he was reported to have been suffering dizziness and high blood pressure "through overwork" for a few days.

TEPCO has pledged to bring the crippled Fukushima Daiichi reactors to a stable state by January. The company's loss is expected to reach a historic maximum of $15 billion in the fiscal year ending in March due to recovery efforts, the largest deficit since the company opened in 1951, the NHK website said, quoting an indentified source close to TEPCO.