It turns out that the U.S. Nuclear Regulatory Commission has calculated the odds of an earthquake causing catastrophic failure to a nuclear plant here. Each year, at the typical nuclear reactor in the U.S., there's a 1 in 74,176 chance that the core could be damaged by an earthquake, exposing the public to radiation.
In contrast [to the seismic core damage frequency], the containment performance analyses conducted under the IPEEE program did not produce sufficient quantitative information to allow the estimation of either LERF or public dose.
This seems to be a clear cut factual error that's misleading and disingenous -- be it intentionally or unintentionally so. It seriously discolors the estimates and makes them something they explicitly are said to NOT be by the NRC.
No, Jason, the article is about core damage, which the NRC says would release radiation. You've decided that I must have been talking about something else, which I wasn't, and now you're saying, why aren't about that something else...
Seismic CDF is the probability of damage to the core resulting from a seismic initiating event. It does not imply either a meltdown or the loss of containment, which would be required for radiological release to occur. The likelihood of radiation release is far lower.
The chance of a core damage from a quake at Indian Point 3 is estimated at 1 in 10,000 each year. Under NRC guidelines, that's right on the verge of requiring "immediate concern regarding adequate protection" of the public.
You're cherry picking. You've decided that the weighted average is the right column to use. Based on what? The NRC staff prefers the column that we've used, the "weakest link." That's the number it sent us, when it sent us one number for each plant. And as the report explains, the NRC has no basis on which to weight the averages, so it says a weighted average wouldn't be meaningful.
Do you have a contact at the NRC who can substantiate your claims? How can you weight data without having a factor to do so? If you get me this information I can [edit my article].
Virtually always weighted data is what you would use in a case like this, as the data is typically weighted by the frequency of occurrence of the event (e.g. a probability of the probability). It's possible your correct, that would just be a bit unusual.
Did an NRC spokesperson tell MSNBC's Bill Dedman that the weighted risk was invalid and to use the weakest link model?
The weighted average is not invalid (see Answer 5 below). All of the values in Appendix D were developed by NRC staff. Table D-1 in Appendix D uses the (2008) US Geological Survey (USGS) seismic source model, but the Seismic Core Damage Frequency results were developed by US NRC staff. The USGS seismic source model is the same one used to develop the USGS National Seismic Hazard Maps.
Tables D-1 through D-3 in Appendix D of the US NRC study show the “simple” average of the four spectral frequencies (1, Hz, 5 Hz, 10 Hz, peak ground acceleration (PGA)), the “IPEEE weighted” average and the “weakest link” model. These different averaging approaches are explained in Appendix A.3 (simple average and IPEEE weighted average) and Appendix A.4 (weakest link model). The weighted average uses a combination of the three spectral frequencies (1, 5, and 10 Hz) at which most important structures, systems, and components of nuclear power plants will resonate. The weakest link is the largest SCDF value from among the four spectral frequencies noted above.
Most nuclear power plant structures, systems, and components resonate at frequencies between 1 and 10 Hz, so there are different approaches to averaging the Seismic Core Damage Frequency (SCDF) values. By using multiple approaches, the NRC staff gains a better understanding of the uncertainties involved in the assessments.
The weakest link model is a method for evaluating the importance of different frequencies of ground vibration to the overall plant performance. The model and its details are not integral to understanding the fundamental conclusions of the study.
The US Nuclear Regulatory Commission study, released in September, 2010, was prepared as a screening assessment to evaluate if further investigations of seismic safety for operating reactors in the central and eastern US (CEUS) are warranted, consistent with NRC directives. The report clearly states that "work to date supports a decision to continue …; the methodology, input assumptions, and data are not sufficiently developed to support other regulatory actions or decisions." Accordingly, the results were not used to rank or compare plants. The study produced plant-specific results of the estimated change in risk from seismic hazards. The study did not rely on the absolute value of the seismic risk except to assure that all operating plants are safe. The plant-specific results were used in aggregate to determine the need for continued evaluation and were included in the report for openness and transparency.
The plant-specific results were used in aggregate to determine the need for continued evaluation and were included in the report for openness and transparency. The use of the absolute value of the seismic hazard-related risk, as done in the MSNBC article, is not the intended use, and the NRC considers it an inappropriate use of the results.
I don't mind criticism at all, but twisting of facts...
How much risk is too much? Is a roller coaster safe only if no one ever dies? If one passenger dies every 100 years? Every year?
Plants have seismic margin and the results of the GI-199 Safety/Risk Assessment confirm that overall seismic risk estimates remain small. GI-199 is not an adequate protection issue.
The study is still under way and it is too early to predict the final outcome. However, the NRC staff has determined there is no immediate safety concern and that overall seismic risk estimates remain small. If at any time the NRC determines that an immediate safety concern exists, action to address the issue will be taken. The NRC is focused on assuring safety during even very rare and extreme events. Therefore, the agency has determined that assessment of updated seismic hazards and plant performance should continue.
Mr. Mink (sic) chastises me for using the weakest-link number in the NRC report, but that's the number the NRC staff provided to me. Several times I sent to Mr. Mick a copy of the spreadsheet the NRC sent to me, containing the weakest-link model as the single number it reported for the risk estimates. (We already had the eastern and central plant data from the report; this spreadsheet, for all plants, gave us the western plant data as well, as we told our readers.) Mr. Mink (sic) fails to mention this in his article. The point, as I told him, was that the NRC staff uses the weakest-link model as the best representation of the risk, and, as I explained to our readers, this is the most conservative estimate. I also pointed out to Mr. Mink that the NRC report describes that its actually has no basis for knowing how to weight a weighted average in this case; he fails to mention this.The NRC says, "the results were not used to rank or compare plants." Mr. Mink (sic) twists this: "In other words Mr. Dedman claimed the study looked at all plants and discussed what risk they were at. It did not." That's completely nonsensical. Yes, the NRC looked at all the plants, and made an estimate of the risk at each one. Did it rank them? No. We ranked them, from the NRC data, just as we explained in the original article.If the newspapers starts reporting the American League East standings in alphabetical order, the reader is free to arrange them by winning percentage.
Perhaps you're naive. Perhaps you have a bias for nuclear power. Perhaps -- who knows? But for some reason, you've fallen for the oldest page in the government PR playbook: the non-denial denial.