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The NRC said: “The finding stems from an NRC special inspection regarding an electrical fire that led to the declaration of an Alert at Fort Calhoun on June 7, 2011. The fire started in a replacement electrical breaker where poor alignment between components and inadequate maintenance increased the electrical resistance on some parts, causing them to heat up and fail. Soot and smoke from the resulting fire then knocked out power to a redundant electrical system used for distributing power to vital equipment needed for the safe shutdown of the plant. The plant was shut down at the time because of flooding along the Missouri River.

The fire resulted in the loss of spent fuel pool cooling for approximately 90 minutes and could have resulted in the loss of a safety function or multiple failures in systems used to mitigate a severe accident, had one occurred. In the event of a serious accident, operators would have had to take compensatory measures to safely shut the plant down.http://www.nrc.gov/docs/ML1210/ML12107A432.pdf

16 June 2011, US Army Corps of Engineers Fort Calhoun Reactor Flooding
16 June 2011, US Army Corps of Engineers

In 2012 the situation appears to have been swept under the rug. The NRC reported: “The second, under NLI NCR-422, was the result of the switchgear fire at Fort Calhoun Station in June 2011. NLI initiated NCR-422 after receiving information from Fort Calhoun Station that the design change for the modification could have been the cause of the fire event. NLI conducted an evaluation, which showed, through engineering design review and testing of the new breaker design, that there was no defect in the new design.http://www.nrc.gov/docs/ML1226/ML12265A100.pdf AZZ had just bought NLI in 2012: http://www.prnewswire.com/news-releases/azz-incorporated-signs-agreement-to-acquire-nuclear-logistics-inc-149458875.html

What Nuclear Logistic Inc [NLI]-the US NRC FINALLY said in 2014 seems to clearly implicate poor choice and defective Schneider breakers. GE breakers would have been a US design. The Schneider Masterpact is a French design. ABB would also have been European (a Swedish or Swiss design).
Additional details:
“- This issue does not affect all of the cradles identified above. Since the issue is a result of incorrect manufacturing tolerances, it will not be present on all cradles.
“- The overheating issue could be a problem with replacement circuit breakers for GE AK-50 circuit breakers. Due to the construction of the switchgear cubicles, there can be vertical misalignment of the stabs in the switchgear. If the primary disconnect float is not adequate, the overheating issue identified above could occur.
“- The overheating issue is expected to be much less prevalent or non-existent on the replacements for GE AKR and ABB K-line circuit breakers. The construction of the switchgear cubicles results in good vertical alignment of the stabs in the switchgear, so the amount of cradle finger vertical float is not as critical.
http://www.nrc.gov/docs/ML1407/ML14071A477.pdf http://www.nrc.gov/reading-rm/doc-collections/event-status/event/2014/20140227en.html

Compare what the NRC reported in 2011 and 2014:
The fire started in a replacement electrical breaker where poor alignment between components … The overheating issue could be a problem with replacement circuit breakers for GE AK-50 circuit breakers. Due to the construction of the switchgear cubicles, there can be vertical misalignment of the stabs in the switchgear. If the primary disconnect float is not adequate, the overheating issue identified above could occur.

Nuclear Power Stations most at risk were believed to be:
OPPD-Ft. Calhoun/LGSB4 with Masterpact NW breaker/AHX30701/18/Original breakers: GE AK-50. OPPD replaced all AHX30701 with narrower disconnect p/n R300112 [Nebraska]
TVA-Browns Ferry/LGSB4 and LGSB21 with Masterpact NW breaker/AHX30701/28/Original breakers: GE AK-50. [Alabama]
FENOC-Beaver Valley/LGSB4 Masterpact NW breaker/AHX307O1/20/Original breakers: GE AK-50
[Pennsylvania]
We would add River Bend because 1) The original breakers were also GE and 2) reported ongoing problems with the Masterpact Breakers: Entergy-River Bend/LGSB9 Masterpact NW breaker/R300112/5/ Original breakers: GE AKR-50. Narrower disconnect. [Louisiana]
See: http://www.nrc.gov/docs/ML1407/ML14071A477.pdf and
http://www.nrc.gov/reading-rm/doc-collections/event-status/event/2014/20140227en.html

Some ideas as to why the 2012 report appears to have involved sweeping facts under the rug:
When Region IV staff recommended in a written report that NRC assemble an “Augmented Inspection Team” (the second most aggressive means of investigating safety problems) to inspect the 2011 fire at the Fort Calhoun Station, Region IV management altered the report to instead recommend a less-intense, paperwork-focused “Special Inspection Team” without the concurrence of the NRC staff who had recommended the more aggressive approach…
Rep. Markey’s letter outlines a series of troubling new allegations that have come to light in the wake of the Congressman’s inquiry last month regarding allegations that the current Deputy Division Director of the Division of Reactor Projects in NRC’s Texas-based Region IV office has actively retaliated against individuals who bring safety concerns to his attention. These latest allegations made by whistleblowers include disturbing accounts of interference with and alteration of safety findings at the Ft. Calhoun Nuclear Station, San Onofre Nuclear Generating Station and Fermi Nuclear Power Plant, and mistreatment of technical staff by Region IV management with verbal berating, workplace humiliation, and lowered performance ratings after years of outstanding reviews. A recent resignation of a member of NRC’s Advisory Committee on Reactor Safeguards due reportedly to inappropriate nuclear industry influence over that body, and a 3-2 NRC vote to overrule Chairman Jaczko’s proposal to include the troubled Fort Calhoun Station on the agenda of a Commission meeting also raise concerns.
http://www.markey.senate.gov/news/press-releases/markey-releases-new-whistleblower-allegations-other-documents-citing-lack-of-confidence-in-nrc-inspector-general
https://web.archive.org/web/20140829115358/http://www.markey.senate.gov/news/press-releases/markey-releases-new-whistleblower-allegations-other-documents-citing-lack-of-confidence-in-nrc-inspector-general
NRC Red Report Fort Calhoun Nuclear Reactor Fire 2011
There is a lot of radiation in spent fuel pools. Even though Fort Calhoun has only has one small nuclear reactor, a little less than half the size of the San Onofre ones, a spent fuel loss of cooling accident would still be very serious, especially in the context of the river flooding.
San Onofre Cesium 137 vs. Chernobyl by Donna Gilmore SanOnofreSafety
SanOnofreSafety diagram. See more: https://sanonofresafety.org