A nuclear engineer from Northern California has been sentenced to more than four years in federal prison for sending threatening letters, including to President Bush.

Prosecutors say Michael Lee Braun mailed nearly 60 letters over a five-year period after the 2001 terrorist attacks. First Lady Laura Bush and former Defense Secretary Donald Rumsfeld were among his targets.

Most contained a white powder the letters described as poison but actually was baking soda.

The 53-year-old from the Sacramento suburb of Elk Grove was arrested in 2006 after mailing threats to Bush, Vice President Dick Cheney and Rep. John Doolittle, R-Rocklin.

The letters were sent days before Bush was to appear at a Doolittle fundraiser in his Northern California district.

Braun was an engineer at the now-closed Rancho Seco nuclear power plant south of Sacramento.

He was sentenced Friday to four years and three months in prison. He also must pay $54,000 in fines and damages.