At 4:00 a. m. on March 28, 1979, a series of unfortunate events caused the core of reactor number 2 at the Three Mile Island Nuclear Power Station near Harrisburg, Pennsylvania, to melt. Although there were no casual­ties, the power unit was a total loss, and the psychological shock to the people in Pennsylvania and the rest of the country counteracted decades of nuclear power promotion.

For all the negative feelings generated by this accident in Pennsylvania, it was not the incident at TMI-2 that stopped the development of nuclear power in its tracks. Economic realities and the fact that the United States had accumulated an overcapacity of power generation had halted nuclear power in its tracks years before. Between 1973 and 1979, 40 nuclear power plant projects had already been cancelled. Since 1978, a year before the Three Mile Island accident, no new nuclear power plants had been autho­rized for construction in the United States. Of the 129 nuclear plants that had been cleared for building, only 53 projects were completed.

Starting with the Shippingport reactor in the late 1950s, nuclear power had seemed economically advantageous over coal-fired power production. Increasing regulatory issues, the rising cost of building sites, and the price of insurance had expanded the cost to the point where nuclear was no lon­ger a bargain. The nuclear power building boom of the 1960s, anticipating a steadily increasing electrical load, had introduced too much generating capability into the economy. The effects of the TMI-2 accident affected the public mood concerning nuclear power. Before the incident, 70 percent of the general public in the United States favored nuclear power. Afterward, the support fell to 50 percent.

On April 27, 1986, a major incident unfolded that would affect the international mood toward nuclear power. A worker at the Forsmark Nuclear Power Plant in Forsmark, Sweden, showed up for work and walked through the radiation-detection portal into the plant. All nuclear workers are checked for radiation as they enter and leave a plant, to keep track of any radiation they may have picked up while working. The alarms went off. A quick check with handheld radiation detectors showed that he was tracking in radiation on his clothes.

This radiation alarm had nothing to do with nuclear activity at Fors — mark. It was due to a major reactor explosion in the Soviet Union, near a town named Pripyat in the Ukraine, 680 miles (1,100 km) away. The day before, at 1:23 a. m. local time, the Chernobyl RBMK reactor no. 4 suf­fered a major power excursion, or uncontrollable increase, during a test of a safety system. An immediate steam explosion tore off the 2,205-ton (2,000-mt) reactor top and the roof of the building it was in and scat­tered radioactive fission products far and wide. Dust went thousands of feet straight up, into the upper atmosphere. When air hit the hot graphite moderator the remains of the reactor caught fire. There were 1,874 tons (1,700 mt) of graphite in reactor no. 4, and it took days for it to burn. Sub­sequent hydrogen explosions only added to the conflagration. Dust from the fire came down in Sweden a day later.

Of the 6,600,000 people living nearby the plant, 56 were killed directly by the accident, and an estimated 9,000 more contracted cancer from exposure to the massive radiation release. The city of Pripyat was quickly and permanently evacuated. Soviet engineering had designed the worst nuclear power reactor in the world, resulting in a radiation release that was so big it was difficult to measure. It made the next-worst disaster, the Windscale fire in England, seem small in comparison. The lasting result was a global slowdown in power plant expansion and a negative change in the collective opinion toward nuclear energy.