Built in 1972 on the shores of Cape Cod Bay, Pilgrim Nuclear Power Station has been the subject of controversy and concern for decades. Now it’s scheduled to close in the next few months. This is part one of a three-part series on the plant as it heads towards permanent shutdown in mid-2019. Read parts two and three.

Pilgrim Nuclear Power Station in Plymouth is one of the worst performing power plants in the country, and it’s scheduled to shut down permanently in four months. Built in the 1970s, it's been continuously supplying the region with power since 1989, but for security reasons, only a few people besides employees have been inside.

The power plant is a simple rectangular building, sitting on the edge of picturesque Cape Cod Bay. To get there, you turn off a winding, wooded road onto long driveway lined with signs that caution against trespassers. As you approach the plant, you can hear the transformer humming as it feeds electricity to the grid through overhead powerlines.

Before entering the reactor room, I’m given a hard hat and something the workers call “nuclear jewelry.” It’s a lanyard with plastic badges and a dosimeter, which measures radiation.

"We have to have everyone who goes into the reactor building wear a dosimeter," Joseph Lynch, external affairs manager for Entergy, explained. "That’ll be your record while you’re on site of any radiation you picked up."

The other badges give me access to certain areas of the plant, like the reactor room. I'm taken there next, and scanned in and given a briefing on where I can and can't go. The reactor building has an airlocked entry because of an air pressure difference between the outside and the reactor.

"Because the reactor building is kept at a different pressure from here, you’ll feel a difference in the pressure as you go in, and then we’ll be in the reactor building," Lynch said. He explained that in the event of an accident in the reactor room, air pressure would flow in, and not out, helping to contain any radioactive dust that could be expelled.

Oddly, the inside of the reactor building looks unassuming, like a big gymnasium. There aren't many large machines, and there are no loud noises, just a soft humming. In the center of this room, I stand on top of a few colored tiles.

Just under those non-descript tiles and my feet, is a huge nuclear reactor. Inside the reactor are slim rods filled with uranium, all submerged underwater. The nuclear reaction heats the water to steam, which turns the turbines, creating electricity. There’s no noise or smell to indicate how much power is being created. And that’s the point.

"Nuclear energy does not generate large amounts of carbon, compared to fossil fuels," said Edwin Lyman, a senior global security scientist with the Union of Concerned Scientists.

Back when Pilgrim was built in the 1970s, nuclear power was thought of as the answer to making clean energy that could be “too cheap to meter.”

"So many people saw it as a potential way to help mitigate global warming in the future, but that will only be an option if it can be maintained as safely and securely as possible," Lyman said.

This brings us to the question of spent fuel. When the plant closes, all those uranium rods in the reactor will be stored in concrete containers, which Entergy plans to keep on site for the next 60 years. This is what many critics are worried about the most. And Lyman explained that the cost of managing nuclear fuel safely is one reason it’s never quite lived up to its promise of being an affordable energy source.

"Nuclear power is not too cheap to meter. It’s turned out to be one of the more expensive forms of generating electricity, and it also has big safety and security concerns," Lyman said.

Before leaving the reactor, my dosimeter is checked again. It shows I received less radiation than I would on a flight from Boston to Los Angeles. The final checkpoint is a machine that looks like an upright tanning bed. It scans me with lasers for any radioactive material that may have landed on me, and counts down.

The countdown for Pilgrim has already begun as the plant enters its final months before decommissioning.