By William Sweet, the author of "Kicking the Carbon Habit: Global Warming and The Case for Renewable and Nuclear Energy." (THE NEW YORK TIMES, 26/04/06):
TWENTY years ago, a huge plume of radiation spread west from the Chernobyl nuclear plant. Dozens of emergency workers were killed at the scene, while vast tracts of land were evacuated and still lie fallow. Rates of thyroid cancer soared among children in Ukraine, Belarus and Russia, and sustained exposure to low levels of radiation in the area has killed or will yet kill thousands, perhaps tens of thousands, of adults. The exact number of casualties will never be known.
For decades before Chernobyl, the public had been assured that nuclear reactors could not explode like bombs and that the association of reactors with nuclear weapons was essentially false. By calling those claims into question, the accident, together with the disappointing performance of atomic power plants during the 1970's and 1980's, pretty much guaranteed that no reactor projects would be initiated for the remainder of the century.
And yet, though it went unnoticed at the time and has been inadequately appreciated since, Chernobyl also cast into relief the positive features of the reactors used in the United States and most other advanced industrial countries.
The reactor at Chernobyl belonged to a class that was especially vulnerable to runaway reactions. When operating at low power, if such reactors lost water, their reactivity could suddenly take off and very rapidly reach a threshold beyond which they could only explode. Making matters worse, surprisingly little more pressure than normal in the machine's water channels would lift its lid, snapping the vital control rods and fuel channels that entered the reactor's core.
On the night of April 25, 1986, poorly trained and supervised plant operators conducted an ill-conceived experiment, putting the machine into the very state in which reactivity was most likely to spike. Within a fraction of a second, the reactor went from being barely on to power levels many times higher than the maximum intended.
This kind of accident cannot happen in the so-called light water reactors used in the United States and most of Western Europe and Asia. In these reactors, the water functions not only as a coolant but as a "moderator": self-sustaining nuclear chain reactions cannot take place in its absence. This is a very useful passive safety feature. If coolant runs low, there is still a danger of a core meltdown, because the fuel retains heat; but the reactor will have automatically and immediately turned itself off.
Still, critics and opponents of nuclear energy have wondered whether utility companies are competent enough to manage anything so complex as a reactor. The question is a reasonable one. In the 1980's, some anti-nuclear groups joined with free-marketeers to promote electricity deregulation. They reasoned that if utilities were no longer guaranteed cost-plus returns on investments — the cushy sort of regulation that had prevailed for a century in the utility industry — they would stop investing in expensive nuclear power plants that were difficult to run.
The utility industry has responded to deregulation by reorganizing itself. And as it happens, companies have emerged that specialize in managing nuclear power plants. Although their record is somewhat mixed (Exelon, for example, stands accused of having carelessly let tritium, a radioactive isotope, leak from three Illinois reactors), on the whole the performance of nuclear power plants has improved substantially.
In 1986, the average American nuclear plant produced electricity barely 57 percent of the time. In 2004, the average plant was running productively more than 90 percent of the time.
This improvement has come just in time. The effects of global warming are disturbingly obvious, and yet the United States has fallen dangerously far behind its response. If we're to get into step with the world effort to reduce greenhouse gases, we are going to need to rely more, not less, on carbon-free nuclear energy.