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{{Adams
#REDIRECT [[CNS-17-048, Supplemental Response to Preliminary White Finding, Apparent Violations, and NRC Inspection Report 05000414/2017012; Enforcement Action 17-122]]
| number = ML17276A345
| issue date = 09/29/2017
| title = Supplemental Response to Preliminary White Finding, Apparent Violations, and NRC Inspection Report 05000414/2017012; Enforcement Action 17-122
| author name = Simril T
| author affiliation = Duke Energy Carolinas, LLC
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000414
| license number =
| contact person =
| case reference number = CNS-17-048, EA-17-122, IR 2017012
| document type = Letter, Licensee Response to Enforcement Action, Licensee Response to Notice of Violation
| page count = 6
}}
See also: [[followed by::IR 05000414/2017012]]
 
=Text=
{{#Wiki_filter:"'e ENERGYr. CNS-17-048  
September
29, 2017 U.S. Nuclear Regulatory
Commission
Attention:
Document Control Desk Washington, D.C. 20555-0001
Subject: Duke Energy Carolinas, LLC (Duke Energy) Catawba Nuclear Station, Unit 2 Docket Number 50-414 Tom Simril Vice President
Catawba Nuclear Station Duke Energy CN01VP I 4800 Concord Road York, SC 29745 o: 803. 701.3340 f: 803. 701.3221 tom.simril@duke-energy.com
Supplemental  
Response to Preliminary  
White Finding, Apparent Violations, and NRC Inspection  
Report 05000414/2017012;  
Enforcement  
Action 17-122 References:
1. NRC Letter from Joel T. Munday to Tom Simril dated August 22, 2017, Catawba Nuclear Station -NRG Inspection
Report 0500041412017012
and Preliminary
White Finding (ADAMS Accession
No. ML 17234A678)
2. Catawba Nuclear Station Letter from Tom Simril to NRC dated August 29, 2017, Response to Catawba Nuclear Station -NRG Inspection
Report 0500041412017012
and Preliminary
White Finding; EA 17-122 (ADAMS Accession
No. ML 17243A129)
On August 22, 2017, Duke Energy received NRC Inspection
Report 05000414/2017012 (Reference
1) describing
a preliminary
White finding associated
with Catawba Nuclear Station's
2A Emergency
Diesel Generator
diode failure event on April 11, 2017. The Inspection
Report provided Duke Energy the option of either (1) attending
and presenting
at a regulatory
conference
or (2) submitting
our position in writing within 40 days. Duke Energy's response* (Reference
2) stated that a written response would be provided within 40 days. This letter provides Duke Energy's written response.
Pursuant to the provisions
of 1 O CFR 2.201, Duke Energy has prepared the attached statement
in response to the subject finding. Duke Energy acknowledges
the preliminary
White significance
determination
and does not contest the finding. There are no regulatory
commitments
contained
in this letter or the enclosure.
www.duke-energy.com 
United States Nuclear Regulatory
Commission
Page 2 September
29, 2017 Please address any questions
regarding
this matter to Cecil A. Fletcher II, Manager Nuclear Regulatory
Affairs at 803-701-3622.
Sincerely, Tom Simril Vice President, Catawba Nuclear Station Enclosure:
Catawba Nuclear Station, Supplemental
Response to Preliminary
White Finding, Apparent Violations, and NRC Inspection
Report 05000414/2017012;
Enforcement
Action 17-122 xc: 
L_ __ United States Nuclear Regulatory
Commission
Page 3 September
29, 2017 xc: C. Haney Region 11 Administrator
U.S. Nuclear Regulatory
Commission
Marquis One Tower 245 Peachtree
Center Avenue NE, Suite 1200 Atlanta, GA 30303-1257
J. D. Austin Senior Resident Inspector
U.S. Nuclear Regulatory
Commission
Catawba Nuclear Station M. Mahoney (addressee
only) Project Manager U.S. Nuclear Regulatory
Commission
11555 Rockville
Pike Mailstop 0-8H4A Rockville, MD 20852 
Catawba Nuclear Station Supplemental
Response to Preliminary
White Finding, Apparent Violations, and NRC Inspection
Report 05000414/2017012;
Enforcement
Action 17-122 Enclosure
Significance
Determination
NRC Inspection
Report 05000414/2017012 (Reference
1) states that based on subsequent
review, the NRC has preliminarily
determined
the finding to be White (i.e., low-to-moderate
safety significance).
In accordance
with NRC Inspection
Manual Chapter (IMC) 0609, Significance
Determination
Process, the NRC determined
that the issue required a detailed risk evaluation
because the finding repres_ents
an actual loss of function of a single train for greater than its Technical
Specification
allowed outage time. Duke Energy has performed
its own detailed risk evaluation, and agrees with the NRC significance
determination
that this represents
a finding of low to moderate safety significance.
Restatement
of Violation
The following
violations
from the NRC Inspection
Report are associated
with the preliminary
White finding. "Technical
Specification
5.4.1.a, "Procedures," requires, in part, that procedures
shall be established, implemented, and maintained
covering the applicable
procedures
recommended
in Appendix A of Regulatory
Guide 1.33, Revision 2. Section 9.b of Appendix A to Regulatory
Guide 1.33, Revision 2, requires, in part, that "preventive
maintenance
schedules
be developed
to specify inspection
or replacement
of parts that have a specific lifetime." The licensee established
Procedure
AD-EG-ALL-1202
to provide direction
for implementing
the preventive
maintenance
program. Section 5.3 of Procedure
AD-EG-ALL-1202, requires that maintenance
strategies
for equipment
within the scope of the preventive
maintenance
program be developed
by considering operating
experience, corrective
maintenance
history and SSC performance.
10 CFR 50, Appendix B, Criterion
XVI, "Corrective
Actions," requires, in part, that conditions
adverse to quality be promptly identified
and corrected.
Contrary to the above, as of April 11, 2017, the licensee failed to ensure that adequate preventive
maintenance
activities
were developed
and adjusted for the EOG excitation
system by incorporating
operating
experience.
Specifically, the licensee did not effectively
incorporate
operating
experience
documented
in Condition
Report 1566561 into the preventive
maintenance
activities
for EOG excitation
system diodes. As a result, a condition
adverse to quality associated
with the elevated diode temperatures
was uncorrected.
This caused the 2A EOG output breaker to trip open during monthly surveillance
testing. The licensee entered this condition
into its corrective
action program as Condition
Report 2116069. The 2A EOG was returned to service on April 14, 2017 following
replacement
of the excitation
system diodes. This violation
is being treated as an apparent violation
pending a final significance
determination." Reason for Violations
The violations
were attributed
to a trip of the 2A Emergency
Diesel Generator (EOG) during a scheduled
operability
periodic test (PT/2/A/4350/002A)
on April 11, 2017. Three minutes after reaching full load and 39 minutes after closing the generator
output breaker, the 2A EOG output Page 1 of 3 
i Catawba Nuclear Station Supplemental
Response to Preliminary
White Finding, Apparent Violations, and NRG Inspection
Report 05000414/2017012;
Enforcement
Action 17-122 breaker 2ETA-18 tripped on overcurrent. This
caused Catawba Nuclear Station (Catawba)
Unit 2 to enter a Technical
Specification (TS) 72 hour shutdown action statement.
Troubleshooting
identified
the direct cause for the overcurrent
trip as a loss of generator
excitation
resulting
from the shorting of the excitation
system voltage regulator
bridge rectifier
diode CR4. Although the NRG inspection
report states "the 2A EOG was returned to service on April 14, 2017," after the replacement
of all the diodes, the 2A EOG successfully
passed its operability
periodic test (PT) and was declared operable on April 13, 2017. Following
a similar diode failure diode in 2005, Catawba did not effectively
evaluate internal and external operating
experience (OE) to recognize
the need to take mitigating
action. Similarly, Catawba failed to effectively
evaluate the 2012 Turkey Point IER L3 12-41. Following
the April 11, 2017, 2A EOG diode failure, a Root Cause Evaluation
was conducted
by Duke Energy to determine
the cause of the diode failure. Corrective
Actions Completed
* On April 12, 2017, the 2A EOG failure investigation
process (FIP) identified
a shorted voltage regulator
bridge rectifier
diode CR4. The failed diode, the remaining
five diodes for the 2A EOG, three silicon-controlled
rectifiers (SCRs), and the power-driven
potentiometer (PDP) were all replaced.
* Complete 4/12/2017
-2A EOG * The diodes on all the EDGs were replaced in May 2017 with new diodes that were inverse voltage tested to ensure that there were no latent deficiencies.
* Complete 5/13/2017
-1A EOG * Complete 5/08/2017 -1 B EOG * Complete 5/24/2017
-2A EDG * Complete 5/19/2017
-28 EOG * An 18-month diode and SCR replacement
preventive
maintenance
activity was established
for the current set of diodes. * Com,plete
9/18/2017
-All EDGs ... The corre.ctive
actions planned and other actions planned do not represent
an all-inclusive
list that will be implemented
as a result of this event; however, the following
are deemed noteworthy.
These actions will be tracked to completion
in accordance
with the Corrective
Action Program (CAP). Any changes to the actions or schedules
noted below will be made in accordance
with the Site's CAP. Corrective
Actions Planned Page 2 of 3 
Catawba Nuclear Station Supplemental
Response to Preliminary
White Finding, Apparent Violations, and NRC Inspection
Report 05000414/2017012;
Enforcement
Action 17-122 Corrective
Actions Planned * Interim Action -Implement
an engineering
change to replace EDG voltage regulator
bridge rectifier
diodes with a diode model type rated for higher reverse voltage and forward current. This action is scheduled
to be completed
by February 28, 2018. Other Actions Planned * Modify the EDG voltage regulator
for all four EDGs to improve design margin. Modifications
will be based on the results of a detailed simulation
of the voltage regulator.
This action is scheduled
to be completed
by May 31, 2021. * Review Cat 1 components
that do not have vendor recommended
replacement
preventive
maintenance
activity.
Determine
acceptability
based on: o Industry reliability
data from academic, military or other technical
sources, o Catawba operating
history, and o Industry operating
experience.
This action is scheduled
to be completed
by December 7, 2017. Full Compliance
Although additional
actions, as described
above, are ongoing, full compliance
was achieved on April 13, 2017, when the 2A EDG successfully
passed its monthly surveillance
testing, PT/2/A/4350/002A, "Diesel Generator
2A Operability
Test." Page 3 of 3
}}

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