WHAT CAN YOU say about the situation at the Diablo Canyon nuclear reactor? The facts aren't all in yet, but it appears, as protesters have insisted for years, that the plant is not sufficiently earthquake-proof. But that doesn't mean that the members of the Abalone Alliance--a quintessentially California happening of underworked TV actors and overgrown flower children, complete with folk songs and "affinity groups"--were right. At best they were right for completely the wrong reasons.

Opposition to Diablo Canyon stems from its proximity to an active earthquake fault that was not discovered until long after construction began. (The site, incidentally, was chosen in a joint effort that included the utility and prominent environmental groups.) In order to withstand seismic stresses, piping in a reactor has to be specially strengthened in particular places. There are actually two reactors at Diablo Canyon, and they are mirror images of each other (like your right and left hands). Apparently in making the extremely complicated seismic calculations, blueprints for the two units were switched, so that reinforcements in Unit One are where they should be in Unit Two and vice versa. So Unit One, which was just about to receive its operating permit, might not be able to withstand an earthquake.

Is this another failure of the Nuclear Regulatory Commission? Probably not. The error was at a level of detail far below what the NRC can detect in its audits. To have found it, the agency would need a staff big enough to duplicate everything a utility and its subcontractors do, and that would create an impossible mess. At some level the NRC has to be able to rely on the utilities' quality control. This mistake--at the very reactor the industry has made the symbol of the costs of unnecessary regulatory delay--seems to reinforce those who believe that the utilities simply aren't up to the task of managing nuclear plants.

On the other hand there is the argument that just as at Three Mile Island the system worked: the mistake was caught in time. True, but just barely. The mistake was found by someone reviewing plans for Unit Two, which is still under construction. It was missed in all the reviews of Unit One. One or both of the reactors could easily have gone to full power without its ever having been found.

No matter how big the problem eventually turns out to be at Diablo Canyon, the nuclear industry is likely to have lost a little more public confidence-- confidence it desperately needs to retrieve. Unfortunately the mindless school of nuclear protest may gain in the process. Counting ourselves among those who want to see nuclear power prove to be safe and economically competitive, we hope the incident will send a message to the industry that it still needs to try harder.