Discussions of nuclear energy and its future seem so often to focus on the physics: the type of uranium needed for fuel, whether it can be enriched into bomb-grade material, the properties of nuclear plant waste, the probabilities of a melt-down. All vitally important, yet there's another side of nuclear energy that must be acknowledged in any fruitful discussion, though it's often ignored or slighted. It's simply that nuclear energy is a business, large and complicated and with a remarkable history. Mark Hertsgaard's goal in ''Nuclear Inc.'' is to explain that side of the issue to us in a straightforward and thorough way, and he has largely succeeded.
Most readers will be familiar with the major players: Westinghouse, General Electric, McDermott, and such giant construction companies as Bechtel and Fluor. But it may be surprising to learn just how sorry is the state into which the nuclear power industry has fallen. There have been no orders for domestic nuclear reactors - none - since 1977. There have, however, been 57 order cancellations. The total number of reactors on order peaked in 1974 at 228 and has been sliding steadily down ever since; as of November 1982, the number was 159.
Over the past 30 years the industry has invested billions in nuclear energy, convinced that if ever there was a sure thing (though it might take time), this was it. Their optimism did seem incontrovertible: We will assuredly run out of oil, and we will just as certainly never run out of nuclear power, if we choose to generate it. Yet this sure bet has not paid off, and it's slightly astonishing to hear Dr. Bertram Wolfe, GE's vice-president for nuclear power, suggest that for the industry as a whole it may never. ''It's questionable whether we will ever be cumulatively profitable,'' he notes, ''whether the returns on the business will ever make up for our losses plus the interest they would be accruing.''
This is the crux. It's obvious, but sometimes overlooked, that no matter how safe nuclear energy is made, it will not exist on any significant scale unless it is profitable - which it currently is not. Hertsgaard sees some chance of change, but the problems are formidable. For example, government regulations on reactor safety are constantly changing, causing reactor construction schedules to stretch out - sometimes to double their original length, multiplying costs severalfold. Yet if the new safety regulations weren't issued and another accident on the scale of Three Mile Island occurred as a result, that would be, Hertsgaard contends, the end of nuclear energy in this country. Either way, it's bad news for the industry. There's no easy solution to the regulation quandary. As Hertsgaard points out, ''Reagan, after all, can only make promises for the four years he is president. But investments in nuclear power must be safeguarded from risk for ten, twenty, even thirty years.''
It's to Hertsgaard's credit that he doesn't opine on whether the industry should survive. He isn't visibly pro- or anti-nuke, an admirable stance that can sometimes become bromidic (''All that can be said with certainty is that the struggle over nuclear power is far from ended.''). This book isn't the ''stunning expose'' promised in its steamy promotional copy. But it is well done , consistently interesting, occasionally surprising, and worthwhile.