Thursday, March 17, 2011

No Seismic Risk List at the NRC

Earlier today, an article appeared on that raised a few eyebrows:

The reactor with the highest risk rating is 24 miles north of New York City, in the village of Buchanan, N.Y., at the Indian Point Energy Center. There, on the east bank of the Hudson, Indian Point nuclear reactor No. 3 has the highest risk of earthquake damage in the country, according to new NRC risk estimates provided to

A ranking of the 104 nuclear reactors is shown at the bottom of this article, listing the NRC estimate of risk of catastrophic failure caused by earthquake.

This is what reporters should do – try to ferret out information- and what reporters should not do – incorrectly present the information.

The problem here is that NRC has no such ranking and no such list. Instead, the “list” is something much more tentative in nature:

The objective of the GI-199 Safety/Risk Assessment was to perform a conservative, screening-level assessment to evaluate if further investigations of seismic safety for operating reactors in the central and eastern U.S. (CEUS) are warranted consistent with NRC directives. The results of the GI-199 SRA should not be interpreted as definitive estimates of plant-specific seismic risk. The nature of the information used (both seismic hazard data and plant-level fragility information) make these estimates useful only as a screening tool. The NRC does not rank plants by seismic risk.

If I read this correctly, the NRC was loosely compiling some information to use as guidance for taking further steps. The information was not intended to be considered definitive. Here’s what the NRC considers definitive.

During the mid-to late-1990s, the NRC staff reassessed the margin beyond the design basis as part of the Individual Plant Examination of External Events (IPEEE) program. The results of the GI-199 assessment demonstrate that the probability of exceeding the design basis ground motion may have increased at some sites, but only by a relatively small amount. In addition, the Safety/Risk Assessment stage results indicate that the probabilities of seismic core damage are lower than the guidelines for taking immediate action.

That’s more like it. Ground motion (or ground acceleration) is different than a Richter scale measurement, but both concern earthquakes.

Operating nuclear plants in the United States remain safe, with no need for immediate action. This determination is based on NRC staff reviews of updated seismic hazard information and the conclusions of the Generic Issue 199 Screening Panel. Existing plants were designed with considerable margin to be able to withstand the ground motions from the “deterministic” or “scenario earthquake” that accounted for the largest earthquake expected in the area around the plant.

I’m not enough of a seismologist to know how the Japan earthquake fits into this equation.

In any event, we need to wait until Japanese authorities have determined the relative damage done to the Fukushima Daiichi plant by the earthquake and by the tsunami.

MSNBC might do better to tone down sensationalism and recognize the complexity of the issues involved in an “earthquake list.”

1 comment:

Atomikrabbit said...

MSNBC viewers don't want science, nuance, or complexity - they want their raw meat antinuclear talking points.