said in a statement on Monday that it expected to have several minority investors in but that it would retain a controlling stake of more than 51 percent.
The deal is expected to be completed in about six months.
Toshiba was selected last month as the preferred bidder for Westinghouse, a top supplier of nuclear-plant technology and Chinese nuclear power, following multiple rounds of bidding over the past several months.
Nuclear power was out of favor after the Chernobyl disaster in 1986 raised concerns about the financial and environmental cost of dealing with radioactive waste. But it has recently .
Concern over the security of power supplies and growing demand worldwide for energy has fueled a surge in crude oil prices, prompting fuel-hungry countries such as China to expand
A source told Reuters last month that Toshiba had outbid its rivals, which includedof the United States and Japan's .
Initial expectations were for Westinghouse to fetch about $1.8 billion, though a source familiar with the situation said last month that the price would be about $5 billion.
The deal is expected to expand significantly the Japanese conglomerate's potential customer base. Toshiba offers boiling water reactors (BWRs), while Westinghouse specializes in the more widely used pressurized water reactors (PWRs).
"PWR represents about 60 percent of the global market, while BWR accounts for less than 30 percent," said Tomoko Murakami, a senior researcher at the Institute of Energy Economics in Japan.
"Moreover, in China and the United States, where active construction of new reactors can be expected, PWR is set to remain the dominant technology."
But the acquisition may strain Toshiba's financial standing and cause the company, the world's fourth-largest chipmaker and third-largest notebook computer maker, to spread its resources too thin, analysts said.
Responding to those concerns, a Toshiba executive said last week that Toshiba could easily cover its part of the acquisition with cash flow. He said Toshiba usually generates 300 billion yen ($2.5 billion) worth of free cash flow in a three-year period.
But the comment failed to allay market concerns entirely.
"Its cash flow is in good condition this business year, but it will be tough in the next business year, even without the Westinghouse deal, because capital spending on semiconductors will increase," J.P. Morgan Securities Asia senior analyst Yoshiharu Izumi said.
As Japan's second-biggest electronics conglomerate, Toshiba offers a wide range of products from nuclear reactors to hot-selling NAND-type flash memory chips. The company is planning to launch new flat-panel TVs using advanced panels called surface conduction electron emitter displays this year.
State-owned British Nuclear Fuels, which runs the Sellafield nuclear fuel-reprocessing plant in northwest England, said in July that it wanted to sell Pittsburgh-based Westinghouse.
Shares in Toshiba closed down 0.5 percent at 744 yen on Monday, underperforming the Tokyo stock market's electrical machinery index, which slid 0.28 percent.