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From an unexpected source — the Wall Street Journal — comes a bit of insight into the blithe safety assurances we get from the Nuclear Regulatory Commission every time there’s a question, issue, or event at a nuke plant.

The article, from Tuesday’s WSJ, is entitled “Earthquake Risks Probed at U.S. Nuclear Plants.” A nice pleasant little breakfast read there.

The gist of the article: in the wake of the Fukushima Daiichi incident, even as NRC officials were delivering their breezy “no threat to public health or safety, everything hunky-dory, please move along” reassurances, something very different was going on inside the agency. Take it away, WSJ…

Privately, though, internal emails from March show staffers at the federal Nuclear Regulatory Commission fretted about the public attention on the potential earthquake vulnerability of some U.S. plants. Since 2005, the agency had been working on a study of seismic hazards that is far from complete but showed good reason to worry about two dozen reactors.

Earthquake dangers have long been known in the American West. Most of the new concern is focused on the central and eastern U.S. (The list of “about two dozen” plants includes Seabrook, but not VT Yankee.)

Now, the risk of a big quake in, say, New Hampshire or South Carolina or Michigan is far lower than in California. But it isn’t zero. And quakes are especially feared “…because earthquakes produce tremendous forces, but also because they are impossible to predict.”

How did this new concern come to the fore? Well, in applications for new nukes filed since 2005, utilities included environmental reviews. And…

NRC staffers say they noticed something in some applications for proposed new plants to be built adjacent to existing reactors: Using updated scientific information, seismic experts hired by the utilities produced “hazard” calculations showing a potential for stronger earthquake-caused ground motion than the original plants were designed to handle.

In other words, the utilities’ own experts reckoned there was an increased chance that an existing reactor could be struck by an earthquake that could overwhelm its ability to shut down safely.

Now, the additional risk from an earthquake is relatively small. It’s low on the list of concerns about nuclear power. To me, the key item to take from this story is that even the NRC itself doesn’t necessarily believe its own public-relations pablum.