A Massachusetts man pleaded guilty in a case involving illegally importing and selling radioactive material from Russia, federal prosecutors said Monday.

Jacob D. Miller, 44, pleaded guilty to importing nuclear material without lawful authority as well as being a felon in possession of ammunition; being a felon in possession of explosive materials; mailing hazardous materials; and possession of child pornography, federal prosecutors said in a statement.

Miller’s lawyer did not immediately respond to a request for comment Monday night.

His pleas were filed Thursday under an agreement with the U.S. Attorney’s Office for the District of Massachusetts, which said Miller is a felon who was convicted in 2004 for possessing child pornography and possessing an explosive device.

After prison, he was warned by the state of Massachusetts about the alleged sale of depleted uranium on eBay, authorities said in a statement in April 2025.

He launched a business called Collect The Periodic Table, selling samples of chemical elements, including radioactive plutonium, and toxic thallium, federal prosecutors said.

Miller sold the elements from his residence in South Hadley, Massachusetts, just outside Springfield, and through a third-party retailer, they said.

Prosecutors said he sent plutonium to 67 customers in the United States and abroad in late 2020 and early 2025. He used the U.S. Postal Service to deliver the element despite a law prohibiting its transport through mail, they said.

An April 2025 search of Miller’s residence turned up a half dozen rifles, explosive powder and ammunition, all in violation of the law because of his status as a felon, prosecutors said. Authorities also said they found child sexual abuse material on his laptop and cellphone, they said.

“Miller has exhibited a long-standing and unlawful obsession with explosives, dangerous chemicals and radioactive substances dating back to at least 2002,” the U.S. Attorney’s Office for the District of Massachusetts said in a 2025 statement.

It said a search of his residence in 2002 turned up “an apparent rocket launcher,” a pipe bomb, and video of Miller setting off improvised explosive devices.

He was convicted in state court of possessing those devices, the U.S. Attorney’s Office said.

Sentencing in the latest case is assigned to U.S. District Court Judge Mark G. Mastroianni and is scheduled for Jan. 21, 2027.

Miller faces the possibility of 46 years or more in prison, though it’s not clear if the judge intends to allow sentences for each charge to be served concurrently, which could reduce that time.