KNOXVILLE, Tenn. (AP) — An 84-year-old nun was sentenced Tuesday to nearly three years in prison for breaking into a nuclear weapons complex and defacing a bunker holding bomb-grade uranium, a demonstration that exposed serious security flaws at the Tennessee plant.

Two other peace activists who broke into the facility with Megan Rice were sentenced to more than five years in prison, in part because they had much longer criminal histories of mostly non-violent civil disobedience.

Although officials said there was never any danger of the protesters reaching materials that could be detonated or made into a dirty bomb, the break-in raised questions about safekeeping at the Y-12 National Security Complex in Oak Ridge. The facility holds the nation's primary supply of bomb-grade uranium and was known as the "Fort Knox of uranium."

After the break-in, the complex had to be shut down, security forces were re-trained and contractors were replaced.

In her closing statement, Rice asked the judge to sentence her to life in prison, even though sentencing guidelines called for about six years.

"Please have no leniency with me," she said. "To remain in prison for the rest of my life would be the greatest gift you could give me."

She said the U.S. government was spending too much money on weapons and the military, and she told the judge about the many letters of support she had received, including one from youth in Afghanistan.

"This is the next generation and it is for these people that we're willing to give our lives," she said.

Rice, Greg Boertje-Obed (bohr-CHEE' OH'-bed) and Michael Walli all said God was using them to raise awareness about nuclear weapons and they viewed the success of their break-in as a miracle.

Their attorneys asked the judge to sentence them to time they had already served, about nine months, because of their record of good works throughout their lives.

Rice is a sister in the Society of the Holy Child Jesus. She became a nun when she was 18 and served for 40 years as a missionary in western Africa teaching science.

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Walli's attorney said the activist served two tours in Vietnam before returning to the U.S. and dedicating his life to peace and helping the poor. Walli said he had no remorse about the break-in and would do it again.

"I was acting upon my God-given obligations as a follower of Jesus Christ," he told U.S. District Judge Amul Thapar.

The judge said he was concerned the demonstrators showed no remorse and he wanted their punishment to be a deterrent for other activists. He was also openly skeptical about whether the protesters caused any real harm and challenged prosecutors to prove it. Assistant U.S. Attorney Jeff Theodore said they had destroyed the "mystique" of the "Fort Knox of uranium."

On July 28, 2012, the three activists cut through three fences before reaching a $548 million storage bunker. They hung banners, strung crime-scene tape and hammered off a small chunk of the fortress-like Highly Enriched Uranium Materials Facility, or HEUMF, inside the most secure part of complex.

They painted messages such as, "The fruit of justice is peace," and splashed baby bottles of human blood on the bunker wall.

"The reason for the baby bottles was to represent that the blood of children is spilled by these weapons," Boertje-Obed, 58, a house painter from Duluth, Minn., said at trial.

Although the protesters set off alarms, they were able to spend more than two hours inside the restricted area before they were caught.

When security finally arrived, guards found the three activists singing and offering to break bread with them. The protesters reportedly also offered to share a Bible, candles and white roses with the guards.

The Department of Energy's inspector general wrote a scathing report on the security failures that allowed the activists to reach the bunker, and the security contractor was later fired.

Some government officials praised the activists for exposing the facility's weaknesses. But prosecutors declined to show leniency, instead pursing serious felony charges.

Prosecutors argued the intrusion was a serious security breach that continued to disrupt operations at the Y-12 complex even months later.

Attorneys for Rice and Walli, 65, both of Washington, D.C., said the protesters were engaged in a symbolic act meant to bring attention to America's stockpile of nuclear weapons, which they view as both immoral and illegal under international law.

Boertje-Obed's wife, Michele Naar-Obed, said before the hearing that she would figure out a way to deal with the sentence, whatever it was. Her real concern was that her husband's actions and imprisonment were not in vain.

"What I'm hopeful for is that people really could appreciate what he did and why he did it and who he did it for. He did it for all of us," Naar-Obed said.

The activists were found guilty on May 8 of sabotaging the plant and damaging federal property.

On Tuesday, about 75 supporters filled the courtroom and an overflow room where they watched the proceedings on a video feed. At a previous hearing, friends of the defendants testified to their good characters and kind hearts, saying the three had dedicated their lives to pursuing peace and serving the poor.

In addition to the prison sentences, each is required to spend an additional three years of supervised release and jointly pay nearly $53,000 in restitution.