Westinghouse Electric Co., once synonymous with America's industrial might, wagered its future on nuclear power — and lost.

Now a unit of Japanese technology giant Toshiba Corp., Westinghouse filed for bankruptcy-court protection, citing as much as $10 billion in debt.

The move marks the end of a troubled era, which began in 1999, when the company ditched its other businesses to focus on reactors. Since then, nuclear power has failed to catch on because of the cost of building reactors in communities that often oppose them and declining costs for competing technologies.