The wife of a former U.S. naval engineer pleaded guilty on Friday to helping her husband try to sell secrets about U.S. nuclear submarines to an unknown foreign country.

The guilty plea by Diana Toebbe, 46, was part of a deal with prosecutors that calls for her to get a much shorter prison sentence than her husband.

Her husband, Jonathan Toebbe, 42, admitted on Monday to conspiring with his wife to disclose restricted data, a violation of the Atomic Energy Act that carries a maximum sentence of life in prison. [nL1N2UP1XA]

His plea agreement calls for him to face a likely sentence of between 12 years to 17 years in prison. Dianne Toebbe pleaded guilty to the same offense, but her plea deal calls for a sentence in the range of three years.

Both defendants will be sentenced at later court hearings that have not yet been scheduled.

Prosecutors alleged in an October indictment that the Toebbes tried to sell government secrets about nuclear submarine propulsion to an unidentified foreign country.

Jonathan Toebbe, who had a top-secret security clearance, communicated with an undercover FBI agent posing as a foreign official over the course of several months, the Justice Department said.

At one point, Toebbe hid a digital memory card containing documents about submarine nuclear reactors in half a peanut butter sandwich at a "dead drop" location in West Virginia while his wife acted as a lookout, according to the department.

The memory card contained "militarily sensitive design elements, operating parameters and performance characteristics of Virginia-class submarine reactors," it said.

An FBI agent testified during a court hearing in October that Toebbe asked for $5 million in cryptocurrency in exchange for the secret submarine information. A payment the FBI made to Toebbe worth about $100,000 has not been located, the agent said.