Beige is the new black for imprisoned Sister Megan Rice, an 84-year old Catholic nun and anti-nuclear activist.

The nun, who spent 40 years teaching in the poorest parts of Africa and returned to the U.S. due to malaria, is now living in deplorable prison conditions, wearing a beige uniform and stuffed in with 111 other women into a single room at a federal prison right here in New York City.

Her criminal odyssey began in 2012, when she and two other activists from the Plowshares anti-nuclear organization — Michael Walli, 63, and Gregory Boertje-Obed, 57 — were dropped off in the middle of the night outside the Y-12 Oak Ridge nuclear facility outside Knoxville, Tenn.

It’s one of the largest nuclear facilities in the United States, and she was there to bring to the attention of all Americans the dangers of unimpeded nuclear proliferation.

Armed with spray paint, bolt cutters and a few other supplies, they first hung large banners on the facility’s chain-link fence, then cut 14-inch inverted L-shape openings in the three fences that “protect” the facility.

They crawled through the openings they had cut, then stood up and walked to the building — easily avoiding any electronic motion sensors and video cameras — without encountering a single guard.

Once they reached the highly enriched uranium-materials facility, “I wrapped some pillars in crime tape,” she told Daily News. “We splashed a vial of human blood on the wall.”

They spray-painted quotes from the Bible such as, “Swords into plowshares,” and banged on the building with hammers. Then they waited to be arrested. They waited some more.

Finally, “We saw a car with a guard slowly driving up. He stopped, and radioed to the police that protesters had gotten in.”

The TV series “Orange Is the New Black” has women living in opulence compared with the real-life conditions of Sister Megan and her fellow inmates, who have been shoved into the Metropolitan Detention Center, designed generally to hold male prisoners until trial, not to hold women after conviction.

Sister Megan’s “cell” is a gymnasium-size dorm unit with 60 bunkbeds for the 111 women, placed a few feet apart. Along one wall are six half-enclosed toilet stalls, six sinks and six shower stalls, and in the middle of the room, 10 dining/work/play tables that can seat 60 women. There is no outdoor courtyard and no mess hall, and food is passed on trays to the women individually through a small window. Little occupational or addiction therapy, no real shot at education other than a GED.

The women eat in the same unit in which they defecate, sleep, shower and wash.

And this is the United States of America, where “Real Housewife” and federal prisoner Teresa Giudice lives in luxury at the federal prison in Danbury, Conn., compared to the inhumane conditions Sister Megan and her cellmates are enduring in New York City.

“In prisons around this country — so overcrowded by unjust laws, poverty and war-making — the patience and endurance of those I live with here is a constant source of admiration and hope that change is possible when the focus can be on what is of real value to the common good,” Sister Megan said.

Her crime? Breaking into a federal nuclear facility at age 82.

The nun ended up proving, in this age of easy terrorism, both how unguarded and how vulnerable our nuclear facilities are to even low-level terrorists.

Her actions, underreported by the media and downplayed likely because of the embarrassment caused to the White House and federal prosecutors, proved that it is harder to break into a convenience store than it is to break into a federal nuclear facility.

I got to meet the sister last week, months after applying for clearance, being denied and then finally getting approval. On a freezing cold night, I walked into the Metropolitan Detention Center and stored everything in a locker but a few one dollar bills allowed for the vending machines.

At 5 p.m., the official start of visiting hours, we were brought into a large, chilly room with armless chairs lined up in rows overseen by one guard. On one side was a sad “playroom” for the prisoners’ children, perhaps 8-by-10 feet, with nothing but a few dirty stuffed animals.

Visiting was supposed to be from 5 p.m. to 7:30 p.m., but it wasn’t until 5:45 p.m. that prisoners were brought in.

I recognized Sister Megan — she was the only 84-year-old woman. She also had a big smile, wide-spread arms and a missing front tooth.

She wore a prison-issued sweatsuit under her beige uniform to combat the cold in the visitor’s room.

“I don’t think I’m supposed to wear the sweatsuit, so they may not allow me to,” she said without a hint of self-pity.

Instead a guard came by to admonish her for moving her chair a few inches out of line in order to lean forward to look at me as we spoke. She immediately pushed it back.

Sister Megan Rice was born in 1930 in New York City — her father was an obstetrician and her mother held a Ph.D. from Columbia University.

At 18, she became a nun, studying at Harvard and earning degrees in biology from Villanova and Boston College. She joined the order of Sisters of the Holy Child Jesus.

She knew she’d go to prison for breaking into the nuclear facility as a protest, she told me, but believes it’s up to people without children who have nothing to lose to take the risks others can’t afford.

“The question — how can we overcome the secrecy and blatant distortion of the truth of the horrific risks to planet Earth’s survival as we know it as long as we fail to transform the nuclear weapons and energy industries into possible, life-enhancing alternatives, and begin with dismantlement now? We are all equally responsible to stop known crimes, according to our unique gifts and abilities,” Sister Megan said.

The Y-12 Nuclear Facility, which they breached in less than seven minutes, and which can theoretically be breached by real terrorists, houses 100,000 tons of highly enriched uranium. According to Robert Gleason, author of “The Nuclear Terrorist” from Tor-Forge, this uranium is bomb-grade and so explosive that one grapefruit-size chunk, if dropped onto another chunk of the same size from a height of 6 feet, would cause an explosion at least half the size of Hiroshima. The weapons-grade highly enriched uranium held there is, in fact, the most dangerous, destabilizing substance in the world. There is enough uranium to wipe out life as we know it, and yet it was guarded by a few rent-a-cops at this federally financed facility.

Sister Megan was sentenced to 35 months — in part because of her age — for interfering with national security and damaging property. Her co-defendants got 62 months each. Earlier they were ordered to pay $52,000 for the estimated damage, which she says the government never substantiated. She believes the damage was no more than a few hundred dollars. The facility didn’t bother to find or even fix the cuts in the fences for five months — until they were shown them by members of Plowshares.

The three are responsible for paying back the $52,000, about which Sister Megan said, “None of us has any assets anyway. (I live my) vow of poverty.”

In fact, upon sentencing, the sister told the judge, “Please have no leniency with me. To remain in prison for the rest of my life would be the greatest gift you could give me.”

After serving at another federal lockup, Sister Megan was transferred last year to the Brooklyn center, to the single floor opened to house the 111 female prisoners.

The thousands of male prisoners there — who are treated more humanely and not crowded into a single room (Al Sharpton once served 90 days there) — include suspected Al Qaeda terrorist Abid Naseer, accused of plotting to bomb the U.S. and Britain; and suspected murder procurer/drug trafficker Ross Ulbricht, aka Dread Pirate Roberts of the online marketplace Silk Road.

Sister Megan’s lawyer, Marc Shapiro, told me, “With headlines these days, we, as a society, are on high alert and take very seriously claims that individuals desire to undermine the national defense. Regardless, when the three senior citizens entered the facility to spread their message of global peace, (they) engaged in no behavior that injured or could have injured our national defense.”

Unlike her counterparts on TV, Sister Megan is incredibly serene despite the horrifying conditions that are impossible to comprehend in America in 2015. She says she’s content to live her life among the “beautiful women here who are my friends,” doing God’s work. The only thing she needs is a dental bridge so that she may once again have a front tooth.

Sister Megan Rice is scheduled for release in November. She will be 85.