Nuclear power rebounding in US as delayed plants come on line. New construction seen early in 21st century as builders learn from past

You might call it a delayed reaction. Nuclear power, which until recently appeared down for the count in the United States, is coming off the canvas with a flurry of plant openings in the next few years. Then will come a construction hiatus, assured by the fact that no license to build a nuclear power plant has been sought since 1978.

But that could well be followed by renewed activity in construction of ``nukes,'' as the problem-plagued industry benefits from lessons of the past. A source at the US Department of Energy estimates that a significant number of construction permits will be issued in time for new plants to become operational early in the 21st century.

Meanwhile, some long-delayed nuclear power plants are on the verge of going on-line, even though arguments continue over who will pay for their highly inflated construction costs, how much their output is needed, and whether safety concerns have, indeed, been met:

Unit 2 of California's Diablo Canyon nuclear plant (near San Luis Obispo) was granted a license Aug. 1 for eventual full-power operations. Diablo Unit 1 began full operation May 8. Foes insist the coastal, twin-reactor facility will be unsafe and vow to continue fighting it.

Undamaged Unit 1 of the two-reactor Three Mile Island nuclear facility near Harrisburg, Pa., was started up Oct. 3 and is expected to be at full power in about three months. Meanwhile, cleanup of Unit 2, where the worst accident in the history of nuclear power occurred 61/2 years ago, is expected to take another two to three years. Opposition to reopening Unit 1 was not strong, but few observers believe Unit 2 will ever be reactivated.

New Hampshire's Seabrook 1 nuke, its cost quadrupled by years of protest and construction delay, is expected to begin ``hot functional'' testing in November, with eventual power production anticipated around mid-1986. (The hot functional phase is a test of all the nonnuclear components of the plant.) Though opponents vow to continue to fight the facility, which is close to heavily used beaches, the state Supreme Court permitted resumption Oct. 1 of full construction on Unit 1. Seabrook Unit 2 is not e xpected to be finished in the foreseeable future.

Connecticut's third reactor at the Millstone nuclear facility in Haddam is expected to go into full production next May.

And, according to the Energy Information Administration (EIA) of the Energy Department, perhaps 47 nuclear power plants across the nation could begin producing electricity by the end of the 1980s.

A new EIA report says that by the end of 1984 there were 86 nukes producing 71.2 gigawatts (a gigawatt is 1 billion watts), 13.6 percent of total electricity generation in the US. In 1990, the EIA projects, nuclear plants will be producing about 110 gigawatts.

But, the government experts say, ``no new nuclear power generating units will be ordered in the United States sufficiently early to allow their operation by the year 2000.''

Not all the problems that created that construction gap have disappeared, and not all of the 47 nukes still in various stages of construction are certain to be completed. Even those that have been given green lights, or at least proceed-with-caution signals, by the US Nuclear Regulatory Commission (NRC) are still being fought by antinuclear power groups.

Organizations like the Seacoast Antipollution League in New Hampshire and the San Luis Obispo Mothers for Peace in California continue to press their cases against nuclear power. For many of the nuclear plants, the questions of who will pay construction costs inflated by legal battles, design flaws, and other unforeseen obstacles remain to be settled. Long after some of the nukes have begun to provide electricity to heat household irons and power high-tech factories, arguments over whether ratepayers or

stockholders will bear construction cost burdens will be continuing.

New Hampshire Gov. John Sununu has estimated that protests and legal actions by antinuclear groups have added $2 billion to the cost of the Seabrook project. Construction of two units was projected to cost just under $1 billion when it began in 1972; now Seabrook 2 is unlikely to be built and the cost of Seabrook 1 is put at $3.7 billion.

Government and industry experts indicate that the travail of the past couple of decades has not been without its rewards. The lessons of Three Mile Island and other less-dramatic setbacks have been taken to heart by both industry and regulators.

Opposition forces -- especially those who presented rational objections that led to detection of flaws and resulted in improved design as well as much-needed safety features -- may well have contributed to the viability of nuclear power in the next century, when it could be a much-needed alternative to fossil fuels.

It is also expected that other challenges -- particularly the cost of ``decommissioning'' worn-out reactors and the safe disposal of spent but still-radioactive fuel -- will have been met within a decade.

Already the NRC has extended the period for which nuclear licenses are valid by 10 years -- from 30 to 40, and researchers say it may be possible to extend the life of reactors even further.

Utility officials, now severely challenged to find the best means of meeting unexpectedly high construction costs for nukes, still maintain that, over the long haul, these power plants will save customers money.

In its recent report, the EIA notes that other countries' use of nuclear power ``has increased considerably in the past year. . . . Both France and Belgium now produce more than half their electricity from nuclear power'' and Sweden and Taiwan are approaching that proportion.