WILMINGTON, DEL./TOKYO (Reuters) - Westinghouse Electric Co, a unit of Japanese conglomerate Toshiba Corp <6502.T>, filed for bankruptcy on Wednesday, hit by billions of dollars of cost overruns at four nuclear reactors under construction in the U.S. Southeast.

Bankruptcy will allow Pittsburgh-based Westinghouse to assess whether to continue construction of the first new U.S. nuclear power projects in three decades for utility companies SCANA Corp <SCG.N> and Southern Co <SO.N>. The company also provides nuclear design, engineering and decomissioning work around the globe, and said in court filings that its nuclear fuel and power plant servicing operations are "very profitable."

Westinghouse and affiliates intend to use bankruptcy to "isolate them from the one specific area of their businesses that is losing money: their construction of nuclear power plants in Georgia and South Carolina," the company said in a filing in Manhattan's U.S. Bankruptcy Court.

For Toshiba, the filing will help keep the parent company afloat and ringfence it from soaring liabilities from Westinghouse