Tokyo Electric Power Co is set to reveal a net loss of as much as $18 billion on Friday to account for the disaster at its Fukushima nuclear power plant, media say, the biggest corporate loss in Japan outside of the financial sector.

President Masataka Shimizu, 66, will step down to take responsibility for the disaster and radiation leaks at the plant, making way for senior executive Katsutoshi Chikudate, 69, the Yomiuri newspaper said.

Engineers are battling to bring the plant under control more than two months after a 9.0 magnitude earthquake and deadly tsunami led to the worst nuclear crisis since Chernobyl.

The disaster has triggered a drop of more than 80 percent in Tokyo Electric's share price and prompted the government to step in with a fund to handle compensation claims that some analysts say could top $100 billion.

For the business year that ended March 31, the company, commonly known as Tepco, will likely reveal a 1.5 trillion yen net loss after accounting for the cost of scrapping reactors at the Fukushima complex and writing off tax assets, the Yomiuri newspaper reported.

The Nikkei business daily estimated the loss for the business year at 1 trillion yen.

Chikudate hails from Iwaki, a city just outside the evacuation zone around the stricken nuclear power plant.

Currently its auditor, he joined the utility in 1966, two years before Shimizu. Both executives worked in the utility's planning department at the same time for three years from 1992.

TEPCO declined to comment on the media reports.

Tokyo Electric's priority right now is to get the situation at the Fukushima Daiichi plant under control, and from that perspective, it makes sense to promote someone from within since they will likely to be able to do that faster than someone from outside, said Hirofumi Kawachi, a senior energy analyst at Mizuho Investors Securities Co.

Chikudate spent three years as the deputy head of the power company's nuclear division a decade ago. In 2007, when he was executive vice president, he apologized to regulators after TEPCO admitted it had covered up two emergency reactor shutdowns.

Shimizu did not make any public appearances in the two weeks that followed the March 11 disaster, sparking criticism that the

company lacked leadership as it fought to bring the plant under control.

Shortly after, Shimizu was hospitalized with dizzy spells as TEPCO's share price plummeted and the company lurched close to collapse.

It was saved when banks offered emergency loans and the government promised a bailout to help the firm compensate households and businesses forced to evacuate from around the Fukushima plant.

The spread on Tepco's five-year credit default swaps, insuring its five-year debt reached a record 762 basis points late on Thursday.

The spreads have more than tripled since the government's chief spokesman Yukio Edano last week suggested banks waive some of TEPCO's debt raising concern the government may not support the company.

Under the state's current rescue plan, TEPCO will have to pay the state back, hobbling its earnings for years to come.

A 1.5 trillion-yen loss would exceed the 812 billion deficit booked by Japan's biggest telephone utility, Nippon Telegraph and Telephone in the year to March 31, 2002 and the 795 billion yen loss by industrial conglomerate Hitachi Ltd. two years ago.

In a bid to raise cash, TEPCO is likely to sell assets worth about 600 billion yen, the Nikkei business daily said.

The biggest gem in its asset portfolio is a 7.9 percent stake in KDDI, a telecommunications company that owns Japan's No. 2 mobile phone network. The stake is worth 201 billion yen based on Thursday's closing price.

Its top 10 stock holdings in companies not directly involved in its generating business amount to little more than 200 billion yen combined, while TEPCO values the stocks on its books at 310 billion yen.

Most of its investments however are locked up in its generating and transmission infrastructure, with 60 percent of 13 trillion yen in assets on its balance sheet accounted for by nuclear plants and other fixed assets.

Shares of TEPCO fell 1.7 percent to 352 yen outpacing a 0.3 percent gain in the benchmark Nikkei 225 index.

($1=81.61 yen)

(Reporting by James Topham, writing by Tim Kelly: Editing by Chris Gallagher and Neil Fullick)