Nuclear Near-Misses

May 19, 2015
Dave Lochbaum

Nuclear Energy Activist Toolkit #55

UCS launched a series of annual reports on the NRC and nuclear power plant safety in 2011. The reports share a common template for what is covered and how it is presented. The reports have something else in common—unanticipated controversies inside and outside UCS regarding our decision to use “near miss” to describe the events summarized in Chapter 2 of the reports.

Internal debates

Our internal machinations over the “near miss” have not involved debates whether it characterizes the events in the proper context. The hue and cry within UCS has been over whether it should be “near miss or “near-miss.”

To hyphenate or not to hyphenate, that is the question. Apparently, it is a question with three answers: yes, no, and sometimes.

(Because “near miss” sounds remarkably like “near-miss” when speaking, Victor Borge’s phonetic punctuation could be invoked to ensure audiences of oral commentaries will know when hyphens have been utilized and when they have been deliberately with-held.)

Our 2011 report, The NRC and Nuclear Power Plant Safety in 2010: A Brighter Spotlight Needed used “near-miss.”

As did our 2012 report, The NRC and Nuclear Power Plant Safety in 2011: Living on Borrowed Time.

So did our 2013 report, The NRC and Nuclear Power Plant Safety in 2012: Tolerating the Intolerable.

Our 2014 report The NRC and Nuclear Power Plant Safety in 2013: More Jekyll, Less Hyde sustained the trend by using “near-miss.”

I inadvertently triggered hyphen-gate within UCS this year when I drafted this year’s report using “near miss” instead of the conventional “near-miss.” What a faux-pas!

Our technical editor directed me to revert back to “near-miss,” citing the convention in the Chicago Manual of Style. So, I used global search and replace to use “near-miss” throughout the draft.

Game on! Our publications staff informed me that we refer to the Chicago manual for many things, but we use the Merriam-Webster Dictionary to make hyphenation calls. Merriam-Webster, oddly enough, does not use a hyphen in “near miss.” So, I used global search and replace to change back to “near miss.”

Round three! Our media staff chimed in by pointing out that the Associated Press Stylebook does not use a hyphen in “near miss” (maybe explaining why it’s not the Associated-Press Style-book.)

So, I offered to compromise by using “near miss” on the even numbered pages and “near-miss” on the odd-numbered pages in the report. I thought this would appease both the pro-hyphen and anti hyphen factions. But all it did was to irk all the campers in all the camps.

Rather than give away the ending to this non-interesting drama, check out our 2015 report The NRC and Nuclear Power Plant Safety in 2014: Tarnished Gold Standard to see our final decision on whether to hyphenate or not.

External debates

Not only did “near miss” cause considerable turmoil in-house, but it has also generated an astonishing amount of outhouse angst. The NRC and the nuclear industry object to our using the term, with or without the hyphen. They contend that the term is pejorative. If pejorative means “entirely appropriate,” then I whole-heartedly agree.

We explain in each annual report how we select which events at nuclear power plants get summarized and stuck with the “near-miss” label. When the NRC dispatches a special inspection team (SIT), augmented inspection team (AIT), or incident investigation team (IIT) to a site, we automatically include that event in the next annual report. We do not add other events or omit any.

Manual Chapter 0309, Reactive Inspection Decision Basis for Reactors, describes the NRC’s decision-making process and criteria for determining when to send follow-up teams to plants. The procedure indicates the process is invoked after a significant operational event which is defined as being:

A significant operational event is any radiological, safeguards, or other safety-related operational event at an NRC-licensed facility that poses an actual or potential hazard to public health and safety, property, or the environment.

Like beauty, “potential” can vary depending on the eye of the beholder, or even which eye a beholder uses. The procedure contains criteria to help the NRC staff screen out significant operational events having low potential so as to allocate reactive inspection resources only for those events having higher potential. This screening includes two tests: the risk of reactor core meltdown increasing and the risk of containment failure increasing.

NRC Test 1: Risk of Reactor Core Meltdown

Figure 1 is from NRC Manual Chapter 0309. CCDP stands for Conditional Core Damage Probability. The condition is the flood or loss of offsite power or safety equipment failure that caused the significant operational event, which often involved additional equipment malfunctions or operator errors. The NRC’s risk analysts evaluate the availability and reliability of remaining mitigating systems to calculate the change in the risk of core meltdown.

Figure 1 (Source

Figure 1.  (Source: NRC Manual Chapter 0309 Table 1)

“CCDP  < 1E-6” (please note that while this looks like a hyphen it’s really a minus sign, so let’s not relapse into hyphen-gate) means the Conditional Core Damage Probability is less than one in a million per reactor-year. “1E-6 —> 1E-5” means the CCDP is between one in a million and one in 100,000 per reactor-year. And so on.

When the increase is negligible, the significant operational event requires no additional inspection effort by the NRC.

When the significant operational event increases the core meltdown risk by roughly a factor of up to 100, the NRC will dispatch a Special Inspection Team.

When the significant operational event increases the core meltdown risk by roughly a factor of up to 1,000, the NRC will dispatch an Augmented Inspection Team.

When the significant operational event increases the core meltdown risk by roughly a factor of over 1,000, the NRC will dispatch an Incident Inspection Team.

NRC Test 2: Risk of Containment Failure

The NRC’s second risk test determines whether the significant operational event increased the chance of containment failure. In Figure 2, CLERP stands for Conditional Large Early Release Probability. The NRC’s risk analysts evaluate whether the significant operational event increased the chances that the containment would fail causing a large release of radioactivity to the environment shortly after the postulated accident began.

Fig. 2

Figure 2.  (Source: NRC Manual Chapter 0309 Table 2)

Based on the results from these risk tests, the NRC decides when to dispatch SITs, AITs, and IITs to investigate significant operational events with potentially higher risk. Most significant operational events do not trigger SITs, AITs, and IITs. For the past five years, the NRC has averaged about a dozen SITs, AITs, and IITs collectively per year.

We cannot use “significant operational events” in our reports. For while they are considered significant operational events by the NRC, the NRC also applies this term to many other events that do not trigger SITs, AITs, and IITs.

The NRC lacks a term for those significant operational events for which it dispatches SITs, AITs, and IITs. Many, but not all, of the events triggering SITs, AITs, and IITs get captured by the NRC’s Accident Sequence Precursor (ASP) program. But the ASP program also includes many events that did not trigger SITs, AITs, and IITs. The NRC’s ASP evaluations often take years to finish.

We cannot use “accident sequence precursors” in our annual reports because ASPs can be for events happening several years ago.

We use “near-misses” in our reports. And we are not alone.


The International Atomic Energy Agency (IAEA) — seldom if ever confused with Greenpeace, likely to the complete satisfaction of both organizations — published a report in November 2005 titled “Trending of low level events and near misses to enhance safety performance in nuclear power plants.” (That IAEA did not hyphenate “near misses” is not entirely relevant to the situation today. Recall that IAEA’s report was issued way back in the days when Pluto was considered a planet.)

The foreword of the IAEA report stated:

As a result of the effort to enhance safety in operating organizations, incidents are progressively decreasing in number and significance. This means that in accordance with international reporting requirements the amount of collected data becomes less sufficient to draw meaningful statistical conclusions. This is where the collection and trend analysis of low level events and near misses can prove to be very useful. These trends can show which of the safety barriers are weak or failing more frequently. Evaluation and trending of low level events and near misses will help to prevent major incidents because latent weaknesses have been identified and corrective actions taken to prevent recurrence. This leads to improved safety and production. (Bold-facing added by UCS.)

What did IAEA consider to be low level events and near misses?

IAEA binned events into three categories: (1) low level events and near-misses, (2) consequential events, and (3) significant events in order of increasing severity.

Based on the Reporting requirement scale on the left-hand side of IAEA’s chart (Figure 3), low level events and near-misses are reported within the utility company, but not reported to the National Regulator. Only consequential and significant events get reported to the National Regulator.

Figure 3.  (

Figure 3. (Source: IAEA-TECDOC-1477 Figure 1)

IAEA’s near-misses are therefore less severe than the events UCS terms “near-misses” in our annual reports. Plant owners report significant operational events to the NRC. The NRC dispatches SITs, AITs, and IITs only for those significant operational events with actual or high potential hazards. UCS “near-misses” have more potential severity than IAEA’s “near misses.”

Bottom Line

I’m looking past my birthday, Christmas, Groundhog Day, and the 2016 Daytona 500 to UCS’s next annual report on the NRC and nuclear power plant safety. Will we hyphenate “near-miss” as we did in 2011, 2012, 2013, and 2014? Or will stay out on the limb defying both the Chicago Manual of Style and the AP Stylebook by not hyphenating the phrase as we did this year? We’re not telling. It’s a more closely guarded secret than the answer to Who Shot J.R. before the premiere episode of Dallas’ fourth season was broadcast. I have not checked the latest Vegas odds to see if the smart money is going hyphen or no hyphen.

But what’s not a secret is that significant operational events that prompt the NRC to dispatch a SIT, AIT, or IIT will be termed “near-misses” or “near misses” by UCS.

We call them “near-misses” or “near misses” because that’s what they are.

See how nice that works?


The UCS Nuclear Energy Activist Toolkit (NEAT) is a series of post intended to help citizens understand nuclear technology and the Nuclear Regulatory Commission’s processes for overseeing nuclear plant safety.