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A self-revealed finding of very low safety … A self-revealed finding of very low safety significance (Green) and associated NCV of Title 10 CFR Part 50, Appendix B, Criterion III, Design Control, and Criterion IV, Procurement Document Control, was identified for the licensees failure to establish measures to ensure that the applicable regulatory requirements and design bases were correctly translated into specifications and instructions. In addition, the licensee failed to establish measures to assure that the applicable regulatory requirements and design bases, which were necessary to assure adequate quality, were suitably included or referenced in the documents for procurement of equipment. Specifically, 125-Volt DC Breakers 72-01 and 72-02 were purchased and installed with thermal overloads and instantaneous trips enabled. The design basis stated that the breakers were non-automatic and only actuated manually. As a result, on September 25, 2011, when an electrical fault occurred on Panel D11-2, the left train 125-Volt DC bus was lost, because the instantaneous trip device on Breaker 72-01 automatically actuated, propagating the fault through the bus, which resulted in a reactor and turbine trip, and plant transient. This issue was documented in the licensees corrective action program as CR-PLP-2011-4835 and CR-PLP-2011-4965 and at the end of the special inspection the licensee was still performing an evaluation to determine the causes and to develop corrective actions. As a remedial corrective action prior to plant startup, the licensee implemented a temporary modification to increase the breaker instantaneous trips and performed an operability evaluation, with compensatory actions for the 125-Volt DC system. The inspectors determined that the finding was more than minor in accordance with IMC 0612, Power Reactor Inspection Reports, Appendix B, Issue Screening, dated December 24, 2009, because it was associated with the Mitigating Systems Cornerstone attribute of Equipment Performance, and affected the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, lack of coordination between Panel D11-2 protective device (FUZ/D11-2) and Breaker 72-01 resulted in the loss of the left 125-Volt DC bus and two preferred AC power sources and complicated plant shutdown during the reactor trip on September 25, 2011, when an electrical fault occurred while working on Panel D11-2. The risk assessment associated with the event on September 25, and the complication caused by the breaker opening, is evaluated and described in the preliminary Yellow AV. The inspectors determined the finding, related to the design deficiency, could be evaluated using the SDP in accordance with IMC 0609, Significance Determination Process, Attachment 0609.04, Phase 1 - Initial Screening and Characterization of findings, Table 4a for the Mitigating Systems cornerstone. The inspectors answered Yes to Question 1 in Column 2. Therefore, the inspectors determined that this finding could be screened as having very low safety significance (Green), because the finding was a design deficiency confirmed not to result in loss of operability or functionality of a system safety function. In addition, the inspectors also determined that the finding affected the fire protection safe shutdown strategies. Therefore, screening under IMC 0609, Appendix F, Fire Protection Significance Determination Process, was required. Based on review of IMC 0609, the inspectors concluded that the finding represented a moderate degradation within the post-fire safe shutdown category and performed a Phase 2 analysis. Based on the licensees evaluation for the loads the inspectors determined that this finding screened as having very low safety significance (Green) per Task 2.3.5, screening check for lack of fire ignition sources and fire scenarios. The inspectors did not identify a cross-cutting aspect associated with this finding because Breakers 72-01 and 72-02 were procured and installed in 1981 and therefore, the finding was not reflective of licensees current performance.flective of licensees current performance.

Discovered date

23:59:59, 31 December 2011 +

Docket

05000255 +

Equipment trip

Turbine Trip + and Reactor Trip +

Event date

23:59:59, 31 December 2011 +

Finding integer

8 +

Finding type

Non-cited violation +

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Identified by

Self-revealing +

Inspection Manual Chapter

NRC Inspection Manual 0609 +, NRC Inspection Manual 0612, Power Reactor Inspection Reports + and NRC Inspection Manual 0609/Appendix F +

Inspection procedure

IP 93812 +

Inspection report

IR 05000255/2011014 +

Inspector

A Scarbeary +, Alan Dahbur +, Jack Giessner + and Robert Krsek +

Modification date"Modification date" is a predefined property that corresponds to the date of the last modification of a subject and is provided by <a rel="nofollow" class="external text" href="https://www.semantic-mediawiki.org/wiki/Help:Special_properties">Semantic MediaWiki</a>.

12:57:32, 25 September 2017 +

Person

A Scarbeary +, Alan Dahbur +, Jack Giessner + and Robert Krsek +

2011Q4 +

Green +

23:59:59, 31 December 2011 +

Title