Just as the nuclear industry faces growing uncertainty brought on by the crisis in Japan, Toshiba Corp. (6502.TO) is having to spend more than $1.6 billion to raise its stake in U.S. nuclear energy firm Westinghouse to 87% from the current 67%.

Not only that, the move appears at odds with Japanese electronics giant's efforts to diversify its energy-related businesses beyond nuclear power after the disaster at the Fukushima Daiichi plant, where some of the reactors were supplied by Toshiba.

Toshiba didn't choose to buy more shares in the
U.S. subsidiary. Shaw Group Inc., which holds 20% of Westinghouse, decided this week to exercise its right to sell the stake back to the Japanese parent company, in accordance with an agreement struck in 2006 when Shaw bought the shares.

Analysts say the cost of funding an increased stake may stretch Toshiba's balance sheet in the short term, though not dramatically. But more importantly, it means the company's fortunes are likely to be tied closer to the nuclear power industry even as the sector faces fresh questions over safety, long delays in the building of new plants and intensifying competition as more players focus on emerging markets for new construction projects.

In late May, Toshiba President Norio Sasaki warned that the company's target of 39 orders for nuclear reactors and Y1 trillion in sales in its nuclear business may have to be delayed beyond the previously expected March 2016.

"A larger stake in Westinghouse now doesn't sound desirable," said
SMBC Friend Research Center analyst Masao Banba. The return on any investment in nuclear power may worsen due to delays in plant construction plans, he said. "Demand is still there, but it will just take longer to achieve the same targets."

Since March, Toshiba has tried to strengthen its energy business in areas other than nuclear power, saying it had contemplated such a move prior to the March 11 crisis.

In May, the company announced a $2.3 billion deal to acquire Landis + Gyr, a Swiss maker of advanced power meters, a key component for highly efficient power-distribution systems using the latest information technology. Toshiba also agreed in May to buy roughly one-third of Unison Co. (018000.KQ), a South Korean maker of wind power equipment.

Shaw's stake sale was prompted in part by the yen's surge. The Louisiana-based engineering company had issued yen-denominated debt to finance its purchase of Westinghouse shares in 2006. Since then, the debt has increased by more than 50% in U.S. dollar terms to about $1.7 billion as the yen has risen to record levels against the greenback.

The put options Shaw is exercising require Toshiba to purchase the shares at a price equivalent to at least 96.7% of the principal amount of the bonds Shaw originally issued.

For Toshiba, this creates expenses equivalent to more than a half of its cash balance, which stood at Y224.24 billion ($2.9 billion) as of the end of June. It could place a burden on its balance sheet for the short term, even though the company wouldn't have to rely on new share issues or other dilutive fundraising methods, analysts say.

"A temporary financial impact (from the share purchase) will be inevitable," said Toshiba spokesman Keisuke Ohmori. He said that the company may use some of its cash and is also considering short-term bank loans. Toshiba also said in a press release that it may seek new investors in Westinghouse

"This surely isn't good timing, because now is the time to be defensive about spending," said Yuichi Ishida, an analyst at Mizuho Investors Securities.

Other current shareholders in Westinghouse include
Kazakhstan uranium supplier Kazatomprom, which holds 10%, and Japan 's IHI Corp. (7013.TO) with a 3% stake.