Busche's complaints are part of a string of whistle-blower and other claims related to the design and safety of an unfinished waste treatment plant at Hanford.
Busche, 50, said she was called into the office Tuesday morning and told she was being fired for cause.
"I turned in my key and turned in my badge and left the building," Busche told The Associated Press in a telephone interview from Richland.
Busche worked for URS Corp., which is helping build a $12 billion plant to turn Hanford's most dangerous wastes into glass. Construction of the plant has been halted over safety concerns. Busche has filed complaints with the federal government, alleging she has suffered retaliation since filing her original safety complaint in 2011.
Hanford was created by the federal government in the 1940s as part of the top-secret project to build the atomic bomb, and cleanup costs today run about $2 billion annually.
Central to the cleanup is dealing with 53 million gallons of highly radioactive waste left from decades of plutonium production for the nation's nuclear weapons arsenal. The waste is stored in 177 aging underground tanks, many of which have leaked, threatening the groundwater and the neighboring Columbia River.
The U.S. Department of Energy is investigating Busche's safety concerns, while the U.S. Department of Labor is reviewing her complaints about retaliation and harassment.
URS Corp. said in a statement it encourages employees to raise safety concerns.
"We do not agree with her assertions that she suffered retaliation or was otherwise treated unfairly," URS said, adding Busche was fired for reasons unrelated to the safety concerns. "Ms. Busche's allegations will not withstand scrutiny."
The Energy Department, which owns Hanford, said it was informed of the firing after the fact. "The department was not asked to and did not approve this action," the agency said in a news release.
A one-of-a-kind plant is being built to convert the waste into glasslike logs for permanent disposal underground, but it has faced numerous technical problems, delays and cost increases.
Busche is the second Hanford whistle-blower to be fired by URS in recent months. Walter Tamosaitis, who also raised safety concerns about the plant, was fired in October after 44 years of employment.
Busche, who worked at the plant for nearly five years, said she had been expecting to be fired for the past month.
"Right now I will take a deep breath, file for unemployment and start another lawsuit for wrongful termination," Busche said.
She declined to reveal her salary but called herself a "highly compensated executive." Busche was a manager of environmental and nuclear safety at the waste treatment plant construction site, and her primary job was ensuring compliance with dangerous waste permits and safety documents.
Tom Carpenter of the watchdog group Hanford Challenge called Busche's firing an act of desperation.
"They couldn't make her leave," Carpenter said. "Hanford's war on whistle-blowers has taken a new victim."
Busche worked at Energy Department nuclear complexes her entire career, generally in nuclear safety, quality assurance or regulatory compliance.
Busche filed her most recent complaint in November, alleging she has suffered retaliation by URS and Bechtel National Inc., the plant's main contractor. She filed the new complaint with the Labor Department.