The Pennsylvania Department of Environmental Resources was incorrectly identified as the Pennsylvania Emergency Management Agency in The Washington Post Sunday editions. The references were to the air raid siren set off on March 30 and to the partial evacuation of the area recommended the same day. CAPTION: (NEW-LINE)Picture 1, Three Mile Island, where America's worst nuclear accident took form in quick, inexorable steps. By John McDonnell-The Washington Post; Picture 2, The control room at Three Mile Island with horseshoe-shaped panel 40 feet long displaying 1,200 warning lights color-coded in red and green. Newsweek magazine photo; Map, By Dave Cook-The Washington Post; Picture 3, Signs of the times near Three Mile Island: Notice of evacuation plan and contest. UPI; Illustration, The Washington Post; Picture 4, At right: Electrical cords belonging to control system atop nuclear reactor vessel at Three Mile Island in photograph taken last year. Cylinders forming a rectangle are part of control rod system used to speed up or slow down nuclear fission. AP; Picture 5, Metropolitan Edison's Jack Herbein explaining sequence of nuclear accident. At news conference he said: "We didn't injure anybody with this accident; we didn't seriously contaminable anybody, and we certainly didn't kill anybody." UPI; Picture 6, Two-year-old Dionne Baylor sleeping in the evacuation center in Hershey. AP

The first warning that something was wrong came when a double-tone claxon blast went off in the control room.

Until then, the only sound intruding on the Susquehanna River in the early morning hours was the deep hum of the big bank of turbines hooked up on the south end of Three Mile Island Nuclear Reactor No. 2.

After three months on the line, No. 2 seemed at last to have shaken out its kinks.

Since it began operations just one day before the end of 1978, No. 2 had proved to be a continuing source of frustration. By starting up before the yearend, the plant qualified its owners for as much as $40 million in federal tax credits and write-offs. In the ensuing days of January, it had been shut down for a two-week interval while engineers from the Metropolitan Edison Co., operators of the reactor downriver from Harrisburg, Pa., traced sources of leaks in the piping and pump system.

But on the morning of March 28, the 889-megawatt plant was going full blast. Large plumes of water vapor drifted from the tips of its two 372-foot cooling towers into the olrilly air.

In the most detailed account yet published on the accident at Three Mile Island nuclear power plant, this article and ensuing installments chronicle the human error and flaws of technology that contributed to America's worst nuclear mishap.

Encased in thick concrete walls and behind bullet-proof windows and reinforced steel doors, the regular four-man crew of control room operators was sitting the watch.

The control room is a vision from science fiction. It sits under the shadow of the 190-foot-high domed reactor containment building. Inside, a horseshoe-shaped panel stretches 40 feet along three walls lined with dials, gauges and 1,200 warning lights color-coded red and green.

This was the scene inside the control room when, shortly before 4 a.m., something went wrong.

Across the Susquehanna, the nearest house to the reactor belongs to Holly and John Garnish. Their red brick ranch house sits just across Route 441 from the plant on the corner of Meadow Lane. Like most of their neighbors, the Garnishes slept in the shadow of the giant cooling towers across the river.

But that morning, Holly Garnish awoke with a start. Outside, in the direction of the plant, a loud roar came from Three Mile Island.

"Picture the biggest jet at an airport and the noise it makes," she recalled. "That's what I heard. It shook the windows, the whole house."

Her husband did not awaken. She looked at the alarm clock, on the night table. It read 3:55 a.m. "I remember because I got up and put the dog outside," she said.

Over on the island, American's worst nuclear accident was taking form in quick, inexorable steps.

A pump that sends hot water to the steam generator failed for reasons still unexplained. Instantaneously, a second pump fedding cooling water to the reactor shut down. It had been fed water from the first pump.

A sensor-"realizing" that the steam generator no longer was receiving water - immediately shut down the plant's giant turbine. With electronic prescience the reactor sensed that the turbine did not want any more steam. A switch was automatically thrown, and a powerful jet of steam shot up from the plant's turbine building at a pressure of 1,000 pounds per square inch.

That was the noise that awakened Holly Garnish.

Only three to six seconds has passed from the start of the incident when yet another event occurred: a relief valve automatically opened to blow off superheated, radioactive water within the containment structure.

No more than six seconds later, the reactor "scrammed;" the control rods that stop the chain reaction inside the reactor vessel automatically dropped into place among the fuel rods. In effect, the reactor was shut down. Fisioning inside the uranium fuel rods immediately began to slow down.

The pressure inside the reactor vessel then began to fall. This should have been the signal for the open relief valve to close. Instead, it stayed open, apparently stuck. Pressurized steam went right on pouring out of the reactor.

The instant the main pumps failed, three auxiliary coolant pumps kicked on. Unhappily, valves that should have been open in the auxiliary feed-water system were closed, locking out the water the pumps were trying to drive.

As water was lost, the temperatures inside the reactor began to soar. Readings climbed 30 degrees in less than three seconds.

In the control room, "bells were ringing, lights were flashing, and everybody was grabbing and scratching," said one Nuclear Regulatory Commission source.

The shift supervisor, sitting in a glass-walled office facing the console, bolted out onto the main floor and took charge.

The pressure, meanwhile, continued to plunge, causing more water in the reactor vessel to flash into the steam and escape through the open relief valve.

At that point - if all systems had been working properly - what had been an usually but not yet serious occurrence automatically would have been brought under control.

Afterward Nuclear Regulatory Commission officials singled out the valve problem as a key one during daily briefings later with the press gathered in the nearby Middletown Brough Hall. "There would have been an entirely different outcome if they [the pumps] had been operational, as they should have been," said Harold R. Denton, NRC s chief of reactor operations.

Apprarently the valves were closed for routine maintenance, in violation of one of the most stringent rules that the Nuclear Regulatory Commission has. The rule states simply that auxiliary feed pumps can never all be down for maintenance while the reactor is running.

"If you take all of these pumps out at once, even for limited time," said an NRC source, "you're supposed to hit the down button and shut the reactor down in a hell of a hurry."

With no fresh, cold water reaching the steam generator and the reactor, the operators in the control room - whether they realized it or not - were in real trouble.

The steam generator had begun to boil dry, taking even more water out of the cooling system. In the reactor vessel, even though the chain reaction had been essentially halted, heat was still being generated as fission wound down. Temperatures in the reactor continued to climb.

Pressures continued to fall in the reactor because the relief valve was still stuck open. "The flow through that valve could have been terminated by pressing the right button in the control room," said a source at Babcock & Wilcox Co., builder of the reactor. "That was ultimately done but it was done 132 minutes later."

Two minutes into the accident, the pressure fell to 1,600 pounds per square inch, automatically turning on the plant's emergency core cooling system. There was still time to prevent these mishaps from mushrooming into a major accident.

For still unexplained reasons, an operator in the control room turned off the two pumps that drive the emergency cooling system. He shut down one pump 4 minutes 30 seconds into the accident and the second pump six minutes later.

The prevailing theory at the NRC and Babcock & Wilcox is that he was looking at only one of two gauges he should have cheecked.

He thought he saw fluid rising in the pressurizer, suggesting that the reactor vessel was still filling with water.

"So he thinks, 'Ah, ha, I've got the system full of water; any more I pump in there is just going to spill on the floor,'" an NRC source said. "Big mistake!"

What was really happening was that pressure was still plunging, water was still flashing into steam, and water levels inside the reactor vessel were in fact dropping.

Much of the water was still spurting out of the reactor vessel through the open pressure valve into the containment.

Only 7 1/2 minutes after the start of the accident, the radioactive water on the floor of the containment building was two feet deep. The buildinghs sump pumps at this point automatically comes on, rushing the water out of the containment structure into tanks in the auxiliary building.

This development would come back to haunt the operators in the days ahead.

"It would have been a help if they had recognized that they ought to cut off that containment sump pump," and NRC source said. "It should have occurred to them: 'Let's not pump it out to the auxiliary building. Let's just leave it in the containment until we know what's going on.'"

Eight minutes after the start, an operator the control room must have realized the auxiliary cooling system hadn't worked because he threw the switch he should have throw eight minutes earlier to unlock the closed valves in the feedwater line, turning on the system.

In three more minutes, an operator restarted the emergency core cooling system that had been mistakenly turned off. For the next 50 minutes, the accident appeared to have diminished in size. Reactor pressure stopping falling. The water level inside the reactor vessel was still sufficient to cover the tops of the 36,000 fuel rods. Though some fuel rods were probably perforated by thermal shock at the start of the accident, they still had not suffered any heavy damage.

"The core had pretty much been covered up to that point," a Babcock & Wilcox source sadi. "While things weren't real good, things were correctable."

Then, the inexplicable happened again.

Though the cooling pumps had come back on, they were not running smoothly. In fact, they had begun to vibrate as they strained to drive cooling water to a reactor whose pressure had fallen so dramatically.

An operator turned off four cooling pumps, two at 1 hour 15 minutes and two more at 1 hour 40 minutes into the accident. The NRC still has no explanation for these moves, though one explanation could have been concern that the pumps were straining so hard they were about to fail.

"The operators obviously were worried about the pumps damaing themselves," a Babcock & Wilcox source said, "but turning them off was a bad idea."

When the fial two pumps were stopped, the water level in the reactor vessel plunged again, uncovering the core and fuel rods for the first time. Heat in the reactor began building up rapidly. Within 14 minutes, the temperature at the top of the reactor had climbed right off the scale.

In the control room, the computer monitoring the temperatures in the dome of the reactor printed readings up to 750 degrees, then began printing question marks. Ir printed question marks for much of the next eleven hours.

Nobody in the plant had any idea that the reactor core had become uncovered - but uncovered it was. The water level had dropped at least four feet below the top of the core, uncovering one-third of the fuel rods. The stainless steel cladding (coating" in the rods had begun to crumble, creating rubble at the top of the core.

Highly radioactive fission products now began to pour from fuel rods that were rupturing in the matter of minutes. The cladding on no fewer than 20,000 of the 36,000 rods is believed to have been oxidized, plunging radioactivity into the reactor coolant. The only thing providing cooling to the fuel rods for the next 11 hours was the steam flashing out of what little water stayed in the bottom of the reactor vessel.

Meanwhil, the number of persons in the control room continued to grow. Executives began arriving in a steady stream in the chilly predawn to join the superintendent of operations, who arrived 20 minutes after the incident started.

"An hour or two after it happened, the place was swarming with white hats," said a control room operator who had been on duty at neighboring Three Mile Island Plant No. 1. "They were looking the thing over, and trying to figure out what to do."

As first light began to break over Three Mile Island, it was becoming increasinly clear to the worried officials that they had a serious threat of radiation leakage.

Shortly before 7 a.m., an emergency siren began to wail - the signal that workers at the Three Mile Island plant should evacuate certain critical areas.

A number of workers dashed for their cars, hoping to get across the bridge to the mainland before they would be confined to the island as a precautionary measure. Two cars made it before the gate slammed.

At 7:02 company officials notified the Dauphin County civil defense office that they had declared a site emergency.

The situation, however, was even worst that they thought.

Back in the control room, less than 20 minutes later, an alarm sounded. An automatic detector in the containment, set to activate when the radiation level reaches 8 rems, had gone off.

Three Mile Island now had become a general emergency.

When word of the trouble at Three Mile Island first filtered out of the plant, the insitutions of crisis management lurched slowly into motion.

Kevin J. Molloy, Dauphin County civil defense director, was boiling water for coffee in his home at Hummelstown when the first call came from a dispatcher warning of a "site emergency" at the nuclear power plant. The time was 7:02 a.m. - more that three hours after the first sign of troble.

That same minute Clarence Deller of the state's Emergency Management Agency logged in a call from a Metropolitan Edison shift supervisor also warning of an emergency at Three Mile Island.

Molloy and Deller began spreading the alarm through a network of local civil defense officials, mayors and state authorities. "My first reaction was: Do we have to evacuate?" Molloy recalled.

It was not until 10 a.m. that Dr. Harold Denton, the chief of reactor operations for the Nuclear Regulatory Commission, was called out of a meeting at the agency's Bethesda headquarters to be informed that a "relatively serious sort of event" had occurred at Three Mile Island.

Yet at 7:20 a.m. Met Ed official Dick Bensel told Molloy's dispatcher that a "general" emegency was under way. That meant bigger trouble than the initial alert but not necessarily enough to evacuate residents.

But by 7:30 a.m. a review of evacuation procedures was already being proposed by the state civil defense agency. "We told them not to begin an evacuation until they were instructed to do so by this office," siad agency spokesman John Comey.

(In a February 4, 1974 letter Met Ed wrote Middletown borough officials that "even the worst possible accident postulated by the AEC [Atomic Energy Commission] would not require evacuation of the borough of Middletown. . . it can be seen that it is unnecessary to have specific evacuation routes identified. . . "

At about 8 a.m. retired Army colonel Oran Henderson, one of the senior military officers in the Mylai operation in South Vietnam more than a decade earlier, was on the phone to Gov. Richard Thornburgh. Henderson, the top official in the state's civil defense apparatus, knowledged afterward that he didn't know what to do or what to recommend at that point. "We lacked so much knowledge about what was going on," he said.

Shortly after 9 a.m. Wednesday, the calls came in to the Old Executive Offical Building in Washington, D.C., almost simultaneously and Jessica Tuchman Matthews fielded them in such rapid-fire order that now she can't remember which one came first.

One was from the situation room in the basement of the West Wing of the White House. The other was from NRC headquarters.

They were calling Matthews, who is the president's National Security Council staff expert on nuclear energy reactors, to report that one had gone bad up at Three Mile Island, Pa., which is a place she had never even thought about.

She remembers mostly that it was all very incomplete. A turbine had tripped; partial loss of coolant; question of possible offsite release of radiation.

Matthews hung up the phones and immediately wrote a short memo - a few paragraphs - to alert her boss, Zbigniew Brzezinski, about what was happening. The memo was taken from her third floor office across the driveway to the White House. Brzezinski immediately took it in to brief President Carter. It was about 10 a.m. Wednesday. "It looked like things were under control," Matthews recalled.

Evacuations was on the minds of state officials early in the day. But no one was prepared to recommend it.

Dauphin County had experienced emergencies before. In 1972 and 1975 the Susquehanna River had flooded. On both occasions Kevin Molloy's office was on alert.

But the severity of what was happening at Three Mile Island was slow to penetrate. For much of the citizens and officialdom of the surrounding communities the plant had been accepted as an economic boon. Word of earlier malfunctions at the plant and been carefully contained and the prevailing local view was that the benefits far outweighed the possible dangers.

Nonetheless, Robert Reid, the mayor of Middletown, just three miles from the plant, became an increasingly angry man from the moment he first got word of the trouble - while he was teaching a high schol government class.

Reid tried but was unable to reach officials of Metropolitan Edison in Reading until 11 a.m. When he finally reached them there was no mention of radiation danger. Furthermore, Ried had little idea of how he would deal with the challenger of a largescale evacuation.

Shortly after he began mayor 18 months ago, Reid had decided the city needed a diaster evcuation plan. He assigned the task to Middletown civil defense director Donald (Butch) Ryan. On March 28, the date of the accident, the plan was still in drafting stages.

Had an evacuation order come from the state capital at Harrisburg, Middletown would have had to improvise.

(At a press coneference Wednesday night in Harrisburg Lt. Gov. William W. Scranton III assured: "We do not expect there to be any kind of necessity for evacuation. . . "

The adjoining town of Royalton - the closest community of the nuclear plant - was equally unprepared. Two days after the accident, its 74-year-old mayor, Charles B. Erisman, still had not been told by Met Ed that there was a problem on Three Mile Island.

"About 75 percent of our people are retired and half of them have no way out," Erisman said of the town's 1,040 residents.

Reid, nonetheless, expressed the prevailing attitude of charitable coexistence with the nuclear genie of Three Mile Island. "You know," he said, pointing out of his office toward the railroad tracks, "I've always been more worried about that than Three Mile Island." A train rumbled by loaded with toxiv chemicals.

At the King of Prussia, Pa., regional office of the Nuclear Regulatory Commission, agroup of technicians gathered by 8 a.m. and established a crisis repsonse center. Their view was detached, as was appropriate for professionals.

"We has an open line to the control room (at Three Mile Island) in about 30 minutes," said Thomas Elsasser, the NRC state liaison officer. "There was no tension or apprehension at that point.

"We knew that since they had got the radiation alarm there was something wrong there. But we knew the plan was shut down, and there had been no release of radioactivity.

At 8:45 a.m. six NRC inspectors piled into the office's emergency vehicle, a red station wagon with flashing roof lights, and began a highspeed run down the Pennsylvania Turnpike to Harrisburg, 86 miles away.

In Bethesda, chief of reactor operations Denton was confused by the fragmentary information trickling in from the field, particularly the reports of radioactivity. He was deeply worried by the possibility of reactor fuel damage. "We never had any incident of fuel overheating in a lightwater reactor plant before," he said afterward. Fuel damage raised the specter of a reactor "meltdown."

Two additional carloads of NRC officials soon left Bethesda and raced northward across the rolling Maryland and Pennsylvania countryside to link with the team from the King of Prussia office.

When the NRC inspectors converged on the scene the cparicious forces of technology had another surprise: Three Mile Island phones were jammed.

Two different telephone companies, Pennsylvania Bell and United Telephone, served the opposite shores of the Susquehanna River. Three Mile Island is served by both companies.

"There was just a terrible communications problem," Denton said. "All the phone lines were jammed up there. You got only bits and pieces."

As the day progressed, the surprises were increasingly ominous. Officials watched with growing concern the reports trickling into the NRC response center of high radiation levels in the plant's auxiliary building.

Denton, ironically, had packed his bags the previous day for a trip to Phoenix and then to sign off on the safety systems for a controversial new nuclear plant in California. It was a trip he never made.

Wednesday night Denton and his task force of NRC officials felt things were under control. The levels of radiation that were being monitored, they thought, corresponded to damage affecting about 1 percent of the fuel in the reactor - a relatively low level.

"We had a rough sequence of things that had gone wrong, we thought. We didn't know what the cause was. I thought it had been a small loss-of-coolant accident," Denton said.

Despite the feeling that things were substantially in hand, Denton decided to stay on that night at the crisis center.

At about 2 a.m., Thursday, he decided to grab one of the cots and a blanket that had been stored there. He lugged them down to an empty office where he caught a few hours' sleep.

The first word to the outside world came in the form of an "urgent" message - a signal of more than routine but hardly castastrophic import - over the Associated Press wire at 9:06 a.m. on Wednesday. It said: "Officials at the Three Mile Island Nucleafr plant have declared a 'general emergency,' a state police spokesman said today.."

There were no details, no explanation of what a "general emergency" was. AP quoted "spokesman" james cox as saying that "whatever it is, is contained in the second nuclear unit."

That enough, however, to fuse the explosion of news media attention that was by 1:30 to surround the plant with some 120 reporters, photographers and television technicians. The three networks as well as local television stations and newspaper from Philadephia, Harrisburg and Baltimore were prowling the grounds, clustering about anyone who seemed to be in a position to speak authoritatively about what had happened.

Residents from nearby Middletown, Royalton, Londonderry and elsewhere, poured out to the scene - bewildered by events at the plant and bedazzled by the occupation army of news figures and government technicians. Mike Connor, 10, skipped school for the day. He decided he would set up a hot dog stand but his mother, Rita, said no. John Garnish boasted that he had been interviewed by five different local television stations, by ABC, by Newsweek and by the New York Darily News.

"Sixty Minutes will be here any minute," he predicted with the confidence of a newborn media star.

That night Walter Cronkite opended his nightly CBS television news program with these words:

"It was the first step in a nuclear nightmare as far as we know at this hour, no worst than that. But a government official said that a breakdown i an atomic plant in pennyslvania today is probably in the worst nuclear accident to date. . . "

Three Mile Island at that point became indelibly engraved as a historic place name in the nuclear era.

If it did nothing else, the accident at Three Mile Island injected new urgency into the national power.

Demonstrations, sit-ins, plant shut-downs, occasional radiation leaks - none evoked the unthinkable aspects of living with the nuclear power as starkly as the accident that Wednesday morning. What often had been dismissed as impossible now seemed to be unfolding on the banks of the Susquehanna.

Ironically, the accident at Three Mile raised the issue of nuclear safety all over just as it had become the least urgent of the three basic parts of the debate on nuclear power. The last few years had seen the threats of the spread of nuclear weapons and the disposal of radioactive waster become more central to the debate than the issue of safety.

In more than 20 years of operations in the United States, there had never been a nuclear accident as threatening to property and human life as Three Mile Island.

Thousands of reactor operating plan-years in the civilian power program have gone by without the loss of a single life. Not a single accident involving the nuclear propulsion system has ever befallen the world's nuclear navies. Only once before, in 1961, when Army technicians mistakenly started a chain reaction while working on a test reactor, had there been a fatality from a nuclear accident.

Nuclear advocates had hammered home this safety record. One famous assessment on which they relied was the so-called Rasmussen report of 1975, a probability study which said the likelihood of nuclear castrophe is very low.

But the Rasmussen report also identifies certain sequence of events which if says are not as unlikely as others. One is called "TMLQ" in the code of the study. It means loss of feedwater plus failure of a safety valve. It is exactly what happened at Three Miles Island.

If ever a meltdown were to occur, according to the controversial study, this is one of the likely ways it might happen.

In the latter half of the last decade, the nuclear debate has inflamed sections of more than 40 states, dividing communities and even households. sit-ins, walks-ins, pray-ins and shout-ins have been held for and against nuclear power. There are dozens of different bumper stickers damning and praising nuclear power.

The most debated issued in the nuclear controversy and isuse in the nuclear controversy had not been the safety of plants like Three Mile Island. It has been whether it is safe to bury the wastes that can remain radioactive for thousands of years.

Second to that is the issue of nuclear weapons proliferation. When India exploded at atomic bomb almost five years ago with the plutonium it extracted from the spent fuel in a nuclear, that issue grew dramatically in importance. Just Friday, the United States suspended economic aid to Pakistan over evidence Pakistan was headed in the same direction.

With antinuclear ranks certain to grow because of Three Mile Island, the debate may once again shift back to safety. At the very least, the nuclear electricity industry faces new and stiffer regulations and could raise costs, shut down some plants and delay others.

It could be worse. The hearings the nuclear industry faces in the House and Senate for the next year over Three Mile Island may bring the types of stiff controls and demands that grind the industry to a halt. It has already slowed to a walk. Last year, only two new nuclear plants were ordered by U.S. electric companies, down from a peak of 41 ordered in the wake of the 1973 Arab oil embargo.In the last three years, 31 nuclear projects were canceled or defered.

Real opposition to nuclear power surfaced in 1968 and has been growing since. That was the year Sports Illustrated published an article entitled: "The Nukes in Hot Water." It raised questions about the impact of nuclear hot water discharge on sportsmen's fishing reels.

Asalternative to muclear power, its critics advocate hydro, coal, wind and geothermal energy as the answers to the nation's energy needs. They regard as the most promising energy source the sun, which could provide limitless heat and electricity without polluting or endangering the air and water.

Solar technology has already made defineable inroads in hot-water heating for individual homes, an appealing alternative to diminishing and increasing costly oil and gas. But the time and expense involved in a harbassing of the sun's power as a major energy source is enormous.

At this point there seems little prospect from either political or technological stand-points that the nation will reverse its commitment to nuclear energy.

The consequence of the Three Mile Island accident is that it will undoubtedly shake the unquestioning acquiescence with which many Americans have accepted nuclear power as the chief ingredient in the nation's long-term energy base.

That may also be its only blessing.

At Three Mile Island the abstractions of the national debate over nuclear power were reduced to frightening particulars: escaping radiation, a "minor" hydrogen explosion, radioactive contamination of the Susquehanna River, the specter of a fallout cloud over the east Coast.

These were the ponderables weighing on the team of government and corporate technocrats struggling to confine the damage. The crisis managers from state and federal agencies as well as the company contractors gathered in an overnight trailer settlement, a technological campground, across the river from the reactor complex. The mood was shifting from the smugness of scientific certainity to humility, skepticism and increasingly, fear that the something had been unleashed over which science appeared to have lost control.

Though on Wednesday, March 28, the planths managers assured the Nuclear Regulatory Commission that the reactor itself was under control, the federal counterparts were skeptical.

Inside the reactor vessel the pressure in the cooling system was fluctuating wildly. Each time the pressure went up blasts of radioactive steam would shoot out of the relief valve, escaping into the containment structure.

A series of alarms warned the control room team of the increasing radiation level inside the containment shell. Yet no one pushed the button that would have sealed off the structure. It was not isolated until the rapidly rising presurre in the building resulting from intermittent steam bursts triggered the automatic cutoff mechanism in the plant.

By mid-morning, Wednesday, with the heat readings in the core going off the scale and printing questions marks on the computer, plant officials were getting desperate over their inability to bring the temperatures down.

At 11:30 a.m., officials decided to "blow down" the system - to try to reduce the pressure in the cooling system to 400 pounds per square inch. This was the level which would permit them to turn on the huge pumps normally used to bring the reactor to a "cold shutdown."

At first, all seemed to be going well. But within the system the coolant was bubbling like campagne. Officials worried that as the pressure on the coolant system dropped, bubbles would be released, forming a pocket of explosive gas at the top of the reactor vessel.

At bout 2 p.m., with pressure almost down to the point where the huge cooling pumps could be brought into play, a small hydrogen explosion jolted the reactor.

The explosion set off the emergency sprays up near the dome of the containment structure, which began pouring 5,000 gallons of white sodium hydroxide solution all over the reactor.

Officials in the control room - who now had their first definitive sign that gas bubbles had formed in the reactor - reluctantly abandoned their effort to depressurize the system.

At 5:30 p.m., they decided to try to bring the pressure back up in an effort to collapse the bubbles. They also decided to try to restart the main reactor coolant pump, which had shut down at the start of the accident.

When it started, water began to circulate again through the reactor, finally immersing the top of the core, which had been left exposed and disintegrating for more than 11 hours.

During the course of Wednesday night, the situation in the reactor began to stablize. The temperature started to come down, and pressure was held around 1,000 pounds per square inch.

On Thursday morning, confident Metropolitan Edison utility officials began a public relations campaign to persuade the public the situation soon would be in hand.

Appearing on ABC's "Good Morning America," Met Ed President Walter M. Creitz told viewers that the plant soon would be safety closed down without injury to anyone.

At a late morning press conference in Hershey, Pa., Creitz introduced Met Ed's top technical official, John G. Herbein, who was quickly ambushed by a pack of reporters.

Why, someone asked, had the company waited three hours to warn area residents of the accident.

"There was no delay," Herbein insisted. "We were carrying out normal plant procedures up to 7 a.m."

He admitted that it was "unusual" that the reactorhs pressurizer relief valve had stuck in the open position, releasing radioactive water into the containment. And he acknowledged for the first time that there may have been human error in the control room. But like Creitz, he continued to walk a delicate line. What the company believed - or at least wanted the public to believe - was that the danger had passed.

Still the reporters pressed him. "I live a mile from the plant," yelled one. "What are you going to be doing to protect my family?" "Mr. Herbein," another shot out, "is your plant a lemon?"

Suddenly someone else grabbed the microphone. It was Middletown's mayor, Robert Reid. Why, he demanded, hadn't his community been told of the danger for three hours? Herbein apologized, promising to do better.

Finally, with 24 television cameras zeroing in on his perspiring face, Herbein's composure broke: "We didn't injure anybody with this accident; we didn'r seriously contaminate anybody, and we certainly didn't kill anybody."

Nobody had died at Three Mile Island.

Meanwhile, radioactive gas and steam were building up to potentially explosive levels in the auxiliary building. Company officials were forced to vent radioactive gases into the atmosphere.

As a result, the spread of radiation was now at the forefront of concern, although little had been done to assure systematic monitoring of radiation levels in the area.

Early Thursday afternoon, Congress, in the form of two visiting delegations, made its appearance on the stage in Pennsylvania. Company officials gave them the same assurances they had given to the press eariler. The politiciasn were skeptical.

The company, seeking not to offend the visiting dignitaries, allowed one congressman, John Wydler (R-N.Y.), to go into the island. Later it allowed Pennsylvania Lt. Gov. William W. Scranton III into the auxiliary building for a personal inspection. "I was suited up in an extraordinary suit," he told reporters after the visit. Asked how he felt, he replied cheerily, "I feel fine."

An NRC official and privately, "I'm sure he got some exposure."

By late afternoon on Thursday, it appeared that the company's soothing reassurances no longer squared with the reality inside the reactor core. Met Ed's credibility was coming in for a licking.

Part of the problem was simply the volume of requests for information coming into the company's small public relations staff. One PR man said the company received 4,000 inquiries during the first two days of the crisis.

Other voices added to the confusion. Two prominent academicians, both critics of nuclear power, made their appearance in the Three Mile Island drama to join the issue, with the company.

Dr. Ernest Sternglass, a radiology professor from the University of Pittsburgh, said he had done samples at the Harrisburg airport, three miles north of the Three Mile Island site. They showed radiation levels 15 times the normal amount expected at the airport, Sternglass said.Dr. George Wald, a retired Harvard Biologist, warned of the effects from radiation on pregnant women and children.

By midafternoon calls were pouring into the offices of the governor and other state officials from worried expectant mothers.

What might be termed the coup de grace to the day's confusions came late Thursday afternoon when all phone communications went out between the Three Mile Island control room and the command post across the river.

"For several hours, there these guys were trying to keep atop of the situation using walkie-talkies," an NRC source said. "The whole situation - simple incredible."

But there was one more startling breakdown to come. Just after midnight, a press aide for the state Department of Environmental Resources turned up in the deserted pres room on the second floor of the state capitol. The department, in an untimely release, said that because Met Ed's holding tanks at Three Mile Island were dangerously overloaded with radioactive waste, the utiliy had for hours flushed the water into the Susquehanna during the afternoon. When it learned of the flushing, the state had ordered it halted.

But no one bothered to tell the communities downstream.

Early Friday morning, one of the small planes cricling continuously above the Three Mile Island plant picked up a disturbing signal - a high and unexpected plume of fresh radiation coming from the stack alongside the auxiliary building.

Witnin the minutes the reading had flashed down to NRC headquarters in Washington and back to Gov. Richard Thornburgh's office, setting off a string of reactions that would suddenly escalate Wednesday's incident into a full-blown crisis.

The first word reaching Washington that morning indicated that the radiation level above the plant had hit 1,200 millirems. NRC officials, alarmed by the strength of the radiation and even more by its very existence, bypassed normal channels and quickly alerted the Pennsylvania Emergency Management Agency in Harrisburg, which in turn notified Thornburgh's office of the new problem. Shortly after 9 a.m., radios in the Harrisburg area informed the public that there was an "uncontrolled release of radiation" coming from Three Mile Island.

In fact, what that small plane had picked up was a deliberate venting of radioactive gas by Metropolitan Edison, part of an effort by company technicians to relieve pressure that was ominously building up in a holding tank. But the company had failed to give the necessary warnings to state or federal officials and so authorities, unaware that the venting was deliberate and not part of a spreading accident, set in motion extraordinary plans to protect the residents of the area.

In Washington, in the basement of West Wing of the White House, the Situation Room is equipped with the most complete electronic instrumentation possible to assure the president of the best intelligent communication. Two of the machines are the Assocaited Press and United Press International wire service tickers - and it was these mchines that first let the president's staff know early Friday that things had taken a turn for the worse in Pennsylvania.

With the new report of radiation, the Situation Room called the National Security Council's Jessica Matthews, who quickly wrote a memo to national security affairs adviser Zbigniew Brzezinski, who briefed the president. Carter then called Joseph Hendrie, chairman of the Nuclear Regulatory Commission.

Suddenly the situation was unpredictable and the outlook was not good.

Carter asked Hendrie: What can we do to help you?What do you need. Hendrie answered immediately. They needed to get another team to the site and better communications. Carter's aides already knew that. They had tried to reach Thornburgh's office in Harrisburg and had been unable to get a call through for half an hour.

Brzezinski got his military aide, Col. William Odum, on the case and within an hour helicopters were landing at the Bethesda Naval Hospital pad to pick up the team from NRC headquarters in Bethesda to ferry them to Three Mile Island. Meanwhile the White House signal corps was installing "drop lines," which plugged the Pennsylvania state offices at Harrisburg and the control room at the nuclear plant into the White House switchboard. It was done in four hours.

This spreading sense of trouble, however, had somehow missed state and federal officials nearest to the plant. At about 8:30 a.m., E. C. McCabe of the NRC told reporters huddled at the door of his trailer across the Susquehanna from the plant that his monitors had measured "a maximum of 20 millirems for a few minutes and then it dropped off very fast."

At about the same time, William Dornsife of the State Department of Environmental Resources was telling his superiors that radiation levels that morning appeared lower than the day before.

And just before 9 a.m., as he headed through the plant's north gate. NRC supervisor Carl Berlinger said he knew nothing about a radiation leak. "I'm sure they wouldn't let us in there if there was a serious health problem."

But in Harrsiburg the tension continued to ratchet upward. Thornburg, totally dependent on the conflicting advice of experts, felt compelled to act - but not to order.

At 10 a.m. he urged everyone within 10-mile radius of the plant to stay indoors until further notice.

The word spread immediately down Highway 441 to Middletown, where Mayor Robert Reid and civil defense chief Butch Ryan sent sound trucks into the street to warn residents to take cover. "Stay tuned to television and radio for more information," the loudspeakers boomed. "Do not call friends and neighbors. . . keep the telephone lines open." Similar warnings were issued in other communities near the plant.

Inside the borough hall, Ryan was hustling his volunteers toward the streets with radiation counters. He handed one of the yellow Geiger counters to a worker and gave blunt instructions: "If you read 100 or more on this thing, you get your ass back here. DON'T go on the radio. I don't care if you use a siren or what.Just get back here."

Reid and his aides called the schools. Cancel recesses, they said. Every child must eat lunch at school. No one goes into the streets.

"Our phones are going haywire," a civil defense worker told the mayor. No wonder, Reid said.

But the mayor wasn't heeding the governor's advise to stay inside. In minutes, he had driven from the town hall to the American Legion post, where officials of Metropolitan Edison had scheduled a press conference.

Even as Reid was arriving and the semicirle of tripods and hot lights was forming near the stage at the front of the legion hall, another act in the growing sequence of confusion began.

At 11:15 - whether deliberately or accidentally - the air raid sirens began to wail across the city of Harrisburg. Some now believe it was the work of an employee in the Department of Environmental of Resources, trying to reinforce Thornburgh's warning to stay indoors. Instead, it had the opposite effect. Back at the legion post in Middletown, a television technician in contact by walkie-talkie with Harrisburg turned to a colleague: "People in Harrisburg are running around like crazy," he said.

At the same instant, Middletownhs overloaded phone system went dead.

It was with that prelude that John Herbein of Met Ed began his delayed press conference. "Conditions," he said, "are stable."

Under questioning, Herbein admitted that the company had deliberately vented radioactive gas into the atmosphere for 45 minutes that morning, from 7:30 until 8:15. He also admitted that the venting had caused radiation levels above the plant that were higher than expected. But he disputed the NRC readings of 1,200 millirems. The levels, he said, was closer to 350 millirems.

Nor did Herbein see any need for panic. "It's certainly the civil defense's prerogative to take those steps," he said, "but we don't think it was necessary. If the civil defense chooses to tell inhabitants of Middletown to keep their windows and doors shut, that's their prerogrative." And then, almost defiantly, he added: "We have our windows and doors open."

Almost lost in this free-for-all between the company and the media was Herbein's passing mention of a bubble of hydrogen gas apparently building up in the reactor core.

"It's serious, but not to the extent that we have to evacuate the citizenry," he said.

But in Harrisburg, Gov. Thornburgh was being told just the opposite. Since urging all residents to stay indoors, the governor had raced through a series of phone calls and meetings, seeking to understand more fully the events of the morning and the potential danger they held for his state. The plain fact was that no one then knew the extent of the danger of low-level radiation to the residents closest to the plant, but by then no one was willing to take chances.

Thornburgh met with officials from the Pennsylvania Department of Environmental Resources, who urged him to order a partial evacuation, even though they believed the radiation levels were still below the danger level.

A similar recommendation came from NRC Chairman Hendrie in Washington. His experts had advised him that the gas bubble then building was potentially more serious than Herbein had hinted to the press. Hendrie told Thornburgh he should urge-not order-people to begin to move out.

Thornburgh also conferred with Carter about the problem. They agreed there was no reason for panic. But at the White House, Brzezinski had called the president's assistant for intergovernmental relations, Jack Watson, to tell him that the situation on Three Mile Island was "at best uncertain." Watson would become the chief link between the governor and the White House. Within minutes, Mathews and Odum were in Watson's office briefing him and his chief aide, Gene Eidenberg.

Eidenberg recalls that he asked how serious it could become and that Matthews replied: "This could be very serious."

Still uncertain of conditions at the plant, Thornburgh decided he must act again. At noon, he called reporters to the media center on the sixth floor of the state Capitol.

"I am advising those who may be particularyly susceptible to the effects of radiation, that is, pregnant women and pre-school-age children, to leave the area within a 5-mile radius of the Three Mile Island facility until further notice."

Despite the governors' repeated efforts to play down the severity of the situation, the effect of the evacuation order was chilling. In Middletown, a convoy of 26 yellow school buses began lining up on the edge of town to take people to the Hershey sports arean 11 miles away.

Near the town hill, five small children clung tightly to their mother and each other. "Mommy, I'm scared. Mommy, I'm scared."

At the Middletown Elementary School mothers arrived running to retrieve their children.

"The kids were calm, but we had a hard time keeping the parents from panicking," said Joe Prokopchop, the principal.

Bonnie Morgan, 19, and Clarence Bankes, the father of the child she was expecting any day, came into the borough hall after hearing the warning. Their eyes were red. They were distraught, scared.

"Nervous" That's not the word for it," Clarence said.

By then traffic was thickening on Union Street, the town's main drag. Cars loaded with clothing and suitcases began crawling up the hill heading out of town.

As the painful exodous mounted, Mayor Reid stood in front of the borough hall watching. He had just issued orders to his 13-man police force to shoot all looters.