A former Los Alamos National Laboratory scientist was sentenced to five and a half years in prison Wednesday after pleading guilty in trying to help Venezuela develop a nuclear weapon, ABC News reports via The Associated Press.

Pedro Leonardo Mascheroni and his wife, Majorie Roxby Mascheroni, both pleaded guilty back in 2013. They admitted to helping develop a nuclear weapon for Venezuela by working with an undercover FBI agent who acted like a representative of the country.

Majorie received 366 days in prison for conspiring with her husband to sell nuclear secrets, and he faces up to five and a half years in prison with 10 years of supervised release.

Mascheroni was under investigation for nearly a year before his indictment. The FBI later took away computers, letters, photographs, books and cell phones from the couple's home in Los Alamos.

Mascheroni, a naturalized U.S. citizen and native of Argentina, previously denied any allegations and said the United Sates government was wrongly targeting him as a spy.

Yet, he told the undercover agent he could help Venezuela develop a nuclear bomb within 10 years, according to the 22-count indictment.

Mascheroni told the agent details of developing the bomb, saying that Venezuela would use a secret underground nuclear reactor that would produce plutonium and an open above-ground reactor that would produce nuclear energy.

The former scientist said in the past those allegations were wrong, and he only approached Venezuela after the United States rejected his ideas that a hydrogen-fluoride laser could produce nuclear energy.

The Argentina native worked in the nuclear weapons design division at the Los Alamos lab from 1979 until 1988 after being laid off. His wife also worked there between 1981 and 2010 as a technical writer.

Mascheroni said he began approaching other countries only after his ideas were rejected by the lab, and he was motivated with the idea of cleaner and less expensive nuclear weapons.