CHERNOBYL, Ukraine — Forbidding under a cold, gray sky, the dead atomic power plant here is a living enterprise.

The explosion that struck 25 years ago this month, in the world’s worst nuclear accident, set in motion a major undertaking that today bears on the life of the entire country. It is a model, or a warning, for what could await Japan. The crisis at the Fukushima nuclear plant will at some point be contained — but then there begins a national project from which there is no exit strategy.

Though the turbines are still, and cranes dangle above two unfinished reactors, just as they have for the past 25 years, too radioactive to be moved anywhere else, this is not a ghost town. Trains arrive on freshly laid tracks, workshops in an un-Soviet shade of blue dot the grounds and steam billows from the chimney of a new gas-fired heating plant that sends hot water throughout the complex.

About 3,000 people work here, in decontaminated areas, maintaining and decommissioning the plant. An additional 4,000 work nearby, providing security in the 19-mile-deep exclusion zone — from which residents were evacuated and where entry is possible only with a permit. (The Fukushima zone has a radius of 12 miles.) Exclusion zone workers also handle water-management and forest-fire-suppression duties, part of the never-ending effort to keep contamination from spreading.

And beyond the exclusion zone lies the vast social structure of evacuees, former emergency workers and their families, farmers whose dwindling villages are contaminated but habitable — survivors, many in ill health, battling an implacable government for the care and assistance they believe they deserve.

“I so much hope the Japanese liquidators will be treated better than we were,” said Yuri Andreyev, who was a chief engineer at Chernobyl and now heads the Chernobyl Union, an umbrella group of advocacy organizations.

In its particulars, the Chernobyl disaster differs from Fukushima’s. A badly executed test, rather than a tsunami, led to the explosion at Chernobyl. Open to the air, a graphite fire burned for 10 days, spewing huge amounts of radioactive material; at Fukushima, with a different type of reactor, that couldn’t happen.

But the significance of Chernobyl for Japan lies in the question of what happens next. Even if the scope of contamination is smaller, Fukushima will demand of the Japanese a commitment of unforeseeable dimensions.

“My wife told me, you know the sarcophagus better than you know your own apartment,” said Grigory Panchuk, who until he retired worked to maintain the tomb encasing Reactor 4.

Panchuk lives in Slavutych, a planned community across the Dnieper River from Chernobyl. With its wind-whipped and featureless plaza, it is a model of late Soviet urban planning — except that in place of the usual war memorial stands one to the 30 workers who died after the April 26, 1986, explosion.

Slavutych residents commute by train to the power station. As they arrive, they pass the wide cooling pond, where pumps run full time to keep the water level above dangerously contaminated sediments. Farther on, they should soon be seeing a new sarcophagus.

Panchuk has a ready smile, but he is an unhappy man. Unable, at 60, to work because of poor health, he hasn’t received the full pension he is entitled to as a Chernobyl veteran with a related disability, which in his case is thyroid disease. So like thousands of others, he is going to court to try to make the government pay what it owes him.

The government fights these cases. It says it has no money. About 130,000 people were evacuated from the exclusion zone, and they are entitled, in theory, to an array of benefits. So, too, are those who responded to the accident — the liquidators — and people in villages just outside the exclusion zone.

‘One day we’ll lie down and die. And that’s it.’

Even if money were not an issue, other realities would be the same. Definitions have to be drawn up, medical examinations pursued, year after year, and distinctions made between the natural effects of aging and the consequences of radiation exposure. The worst issues don’t necessarily appear right away: The steepest rise in thyroid cancer in neighboring Belarus came nearly two decades after the explosion.

Panchuk tends to believe that the Japanese will do a better job of it: that the government will uphold its promises, that people won’t be deprived of their due, that corruption won’t warp the entire system.

Maria Krivolapova, 61, worked in a pig-iron plant near Chernobyl. Her husband, Mikhail, was at the power station. After the accident, she loaded sand into helicopters that were trying to put out the fire and she cooked for the crews. The pilots had reported directly from the war that the Soviets were fighting in Afghanistan. She saw one pilot vomit as he stumbled out of his chopper, then fall to the ground.

After eight days, they were ordered to evacuate.

“They told us it would be for three days, and the result was forever,” she said. She was assigned to work on a state farm in a village called Obukhiv, south of Kiev, the capital. She and Mikhail built a rough concrete house, without running water, and she lives there today with her daughter Yelena and her family. They keep goats, pigs, chickens, a cow.

Mikhail died of lung cancer 13 years ago. Yelena, who was 13 in 1986, has a vascular disease that state doctors only recently affirmed as Chernobyl-related, after years of denial.

“We’re not rich, but we’re happy,” Maria said in her unfinished kitchen as she wrestled a batch of her homemade farmer’s cheese into shape. She has thyroid disease, heart disease and high blood pressure. She said she was diagnosed with radiation sickness in June 1986 but her medical records were taken from her. She doesn’t know how much of a pension she is supposed to receive, but she knows she isn’t receiving it.

So one day in March found her in Kiev, at the cramped offices of the Chernobyl Union. Others were there on the same mission: Tatyana Kirilchuk, 53, thyroid disease; Galina Dubrova, 55, who along with her husband and five grown children has thyroid disease, as well as liver and vascular ailments; Tamara Perebeiniz, 62, thyroid disease; Lyudmila Vinokur, 62, thyroid disease. Perebeiniz and Vinokur have disabled husbands at home.

They had come for legal help against the government. They were not optimistic.

In fact, the government plans to cut the benefits that it hasn’t been fully paying anyway.

“There is indignation everywhere,” Andreyev said. “They’re doing this even as the whole world is watching the disaster at Fukushima, and admiring the work of the liquidators there.”

Svetlana Protsyk is head of Ukraine’s Children of Chernobyl committee. The government is supposed to provide finances but has made no payments this year, she said. Her husband was at Chernobyl for three days in 1986, working three-minute shifts as a liquidator. He was back for 10 days in 1987. He was recently paralyzed on one side by a stroke. Her thyroid was removed in 2000. Doctors deny that her health problem is related to Chernobyl.

The question of Chernobyl’s connection to illness is a thorny one. The liquidators are an aging cohort, and Ukraine is not a healthy society. One resident of Slavutych, Lyudmila Leshkovych, said her health might be worse if she had stayed in the heavily polluted industrial city of Zaporozhye to which she was originally evacuated.

A recent United Nations report, drawing on studies by Western researchers, said that 6,000 cases of thyroid cancer could be linked to Chernobyl but that evidence regarding other diseases is inconclusive.

Russian, Ukrainian and Belarusan researchers, however, say their studies show increased incidence of high blood pressure, stroke, vascular disease and non-malignant thyroid diseases among liquidators.

The uncertainty is wearing, though it fades.

“One day we’ll lie down and die,” Leshkovych said. “And that’s it.”

‘They just want people to die off quicker’

The village of Kosachivka stands just outside the exclusion zone. Most of its houses are abandoned. Because it was moderately contaminated, its 400 remaining inhabitants receive government assistance — 20 cents a month — to enable them to buy “clean” food.

“They just want people to die off quicker,” said Vladimir Stepanyets, 54, who spends his time tinkering with an old motorcycle and collecting spent tank shells from a nearby army firing range.

Near Pripyat — the abandoned and now overgrown dormitory city for Chernobyl, where moss grows on the central square and the wind thrums through the rusting Ferris wheel — lies a more haunting place. It was once the village of Kopachi, which happens to mean “Gravedigger” in Ukrainian. Every house there was buried in 1991 because of contamination. When Gravedigger was interred, only a nursery school was left standing, with a memorial to the Soviet soldiers and the fierce battles they fought here in World War II.

“No one forgets. Nothing is forgotten,” reads the plaque on the memorial. But because of Chernobyl there is now no one here to remember.