ML17200C945
| ML17200C945 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 07/14/2017 |
| From: | Hamilton D FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-17-216 IR 2017009 | |
| Download: ML17200C945 (6) | |
See also: IR 05000440/2017009
Text
FENOCŽ FirstEnergy
Nuclear Operating
Company David B. Hamilton
Vice President
-July 14, 2017 L-17-216
A ITN: Document
Control Center U.S. Nuclear Regulatory
Commission
DC 20555-0001
SUBJECT:
Perry Nuclear Power Plant Docket No. 50-440, License No. NPF-58 Perry Nuclear Power Plant P.O. Box 97 10 Center Road Perry, Ohio 44081 440-280-5382
Response
to NRC Inspection
Report 05000440/2017009
and Preliminary
White Finding On June 5, 2017, the Nuclear Regulatory
Commission
(NRC) issued Inspection
Report 05000440/2017009
and a Preliminary
White Finding to the Perry Nuclear Power Plant. This Inspection
Report contained
a Preliminary
White Finding and Apparent
Violation
- 05000440/2017009-01
"Unsuitable
Application
of Surge Suppression
Diodes in Standby Diesel Generator
Control Power Circuitry."
In a letter dated June 14, 2017, the FirstEnergy
Nuclear Operating
Company (FENOC) notified
the NRC of our choice to submit a written response
to the Inspection
Report. Attached
is FENOC's response,
which adds some clarification
to the initial apparent
violation.
We have reviewed
the preliminary
white finding and we believe the description
of the performance
deficiency
does not comport with the root cause and it does not accurately
characterize
the issue. The attachment
provides
detail of the disputed
language.
We respectfully
request your consideration
of this information
prior to issuing the final violation.
There are no regulatory
commitments
contained
in this letter. If there are any questions
or if additional
information
is required,
please contact Mr. Nicola Conicella, Regulatory
Compliance,
at (440) 280-5415.
Sincerely,
David Hamilton
Vice President
Perry Nuclear Power Plant L-17-216
Page 2 Attachments
Response
to Apparent
Violation 05000440/2017009-01
"Unsuitable
Application
of Surge Suppression
Diodes in Standby Diesel Generator
Control Power Circuitry"
cc: NRG Branch Chief -Jamnes Cameron NRG Project Manager -Kimberly
Green NRG Regional
Administrator
-Cynthia D Pederson
NRG Director
of Reactor Projects
-Patrick L. Louden NRG Resident
Inspectors
Attachment
l-17-216
Page 1of4 Violation
Details Inspection
Report 05000440/2017009,
dated June 5, 2017, contained
the following
Preliminary
White Finding for the Perry Nuclear Power Plant (PNPP): Preliminary
White. The inspectors
identified
a finding preliminarily
determined
to be of low to moderate
safety significance
(White),
and an associated
apparent
violation
of Title 10 of the Code of Federal Regulations
(10 CFR) 50, Criterion
Ill, "Design Control,"
for the licensee's
failure to implement
measures
for the selection
and review for suitability
of application
of voltage suppression
diodes installed
in the control circuitry
for the Division
2 Standby Diesel Generator,
which was a component
subject to the requirements
of 10 CFR Part 50, Appendix
B. Specifically,
Engineering
Change Package 04-0049 failed to consider
the effects of a shorted diode on the control circuitry
for the Division
2 Standby Diesel Generator,
and instead,
introduced
new components
(diodes)
into the control circuitry
that resulted
in the eventual
failure of this safety-related
equipment.
This rendered
the standby diesel generator
and unable to start for longer than its technical
specification
allowed outage time, which was a violation
of Technical
Specification
3.8.1, "AC Sources-Operating."
The licensee
documented
the issue in CR 2016-13183,
and subsequently
replaced
the failed component
and then modified
circuitry
to remove the replacement
diode and the remaining
diodes from similar components.
, The inspectors
determined
that the licensee's
failure to evaluate
the effects of voltage suppression
diode failure on the Standby Diesel Generator
control circuit was contrary
to the requirements
of 10 CFR Part 50, Appendix
B, Criterion
Ill and a performance
deficiency
which was within the licensee's
ability to foresee and prevent.
The inspectors
determined
that the performance
deficiency
was of more than minor significance
because it was associated
with the design control attribute
of the mitigating
systems cornerstone
and adversely
affected
the cornerstone
objective
to ensure the availability,
reliability,
and capability
of systems that respond to initiating
events to prevent undesirable
consequences
(i.e., core damage).
Specifically,
the design of the Division
2 Standby Diesel Generator
control circuit resulted
in the inoperability
and unavailability
of the Division
2 Standby Diesel Generator
from April 2, 2015, to November
8, 2016, when the failed diode was replaced.
A Significance
and Enforcement
Review Panel, using IMC 0609, Appendix
A, "Significance
Determination
Process for Findings
At-Power,"
dated June 19, 2012, preliminarily
determined
the finding to be of low-to-moderate
safety significance.
The inspectors
did not identify
any cross-cutting
aspects associated
with this finding because the condition
had existed si.nce at least 2007, when the diodes were originally
installed
in the DC control power circuits,
and therefore,
was not indicative
of current plant performance.
(Section
40A2.1) Response
The FirstEnergy
Nuclear Operating
Company (FENOC) does not agree with the performance
deficiency
as described.
FENOC asserts that the design was adequate
Attachment
Page 2of4 and appropriate
for use in the control circuit and without the manufacturing
defect would have functioned
as designed.
The Apparent
Violation
as described
has these main points that FENOC does not agree* with: * Installation
of surge suppression
diodes in the SDG control circuit was not evaluated
and, without mitigation
for failure,
was not appropriate
for the SDG control power circuit.
- Installation
of surge suppression
diodes provided
no safety benefit to the SDG control system. * The diode failure rendered
the standby diesel generator
and unable to start for longer than its technical
specification
allowed outage time. Details Installation
of surge suppression
diodes in the SDG control circuit was not evaluated
and, without mitigation
for failure,
was not appropriate
for the SDG control power circuit.
- The effects of a diode failure were considered
as an aggregate
evaluation
of parts rather than component
by component
individual
evaluations.
The Updated Safety Analysis
Report (USAR) does not discuss the reliability
of SDG components
at the level that the change was being made. For the SDG engine and generator,
the USAR only discusses
malfunction
of the SDG as a unit with the result being the loss of one divisional
SDG. There are no failure modes and effects analysis
in the USAR for subcomponents
of the diesel generator
itself, the speed control system or its controls.
- No new failure modes were introduced
by the addition
of surge suppression
diodes as addressed
in NEI 96-07 "Guidelines
For 10 CFR 50.59 Evaluations"
section 4.3.6. The 50.59 Evaluation
for ECP 04-0049 states "Reliability
of the new components
has been based on industry
experience
and experience
at other nuclear facilities
.... [operating]
experience
was reviewed
through [Institute
of Nuclear Power Operations]
and no adverse trends were noted for the new components."
- The diodes were installed
consistent
with IEEE recommended
practice
for Powering
and Grounding
Electronic
Equipment
Section 10.4.4.1,
Contact Suppression,
which states, this is standard
practice
in any industrial
control system. It also states that the first choice in a DC circuit is a flyback diode for voltage suppression.
The IEEE standard
does not provide mitigation
strategies
for
failure.
Installation
of surge suppression
diodes provided
no safety benefit to the SDG control system. * The use of suppression
diodes does provide a safety benefit in that the voltage suppression
helps to minimize
arcing and degradation
of contacts
that interrupt
current to the relays (reference
the Root Cause Report for CR 2016-14456).
It was later determined
that the diodes could be removed without significantly
impacting
components
in the Division
1 and 2 125 VDC control circuitry
and the increased
risk could be managed through preventative
maintenance
(PM) frequency
controls.
Attachment
Page 3of4 The diode failure rendered
the standby diesel generator
and unable to start for longer than its technical
specification
allowed outage time. * Continuity
testing in May 2016 demonstrated
that the diode was not shorted,
therefore,
had not failed upon de-energization
in April 2015. The apparent
violation
stated that the test conducted
in May 2016 was not a valid test. Although
continuity
testing would not have detected
an internal
manufacturing
defect, it was an adequate
test to determine
if the diode was shorted,
which would have precluded
the SDG from performing
its intended
function.
- The root cause concluded
the cause to be a defective
diode (cracked
die). It is not clear at what point in time the degradation
of the diode would have progressed
to the point of failing upon re-energization.
With a cracked die in the diode, there are multiple
stressors
that could have affected
it, including
temperature
changes.
Therefore,
there is no firm evidence
demonstrating
that the diode was failed in May 2016. As such, with the absence of firm evidence
otherwise,
it should be assumed that the diode failed at the time of discovery.
Conclusion
FENOC asserts the following:
- Installation
of surge suppression
diodes in the SDG control circuit was appropriately
evaluated
and was appropriate
for the SDG control power circuit.
- Installation
of surge suppression
diodes provided
a safety benefit to the SDG control system. * The diode failure did not render the SDG inoperable
and unable to start for longer than its technical
specification
allowed outage time. The root cause determined
the failure to be a manufacturing
defect in the specific
diode that was installed
in the Division
2 SDG that was to protect the components
within the SDG start circuitry.
This was supported
by independent
laboratory
diode testing and a 1 OCFR Part 21 notification,
by the vendor who supplied
the diodes, of a manufacturing
defect internal
to the diode with the same date code as the installed
diode. The supplier
of the diodes used non-conservative
acceptance
criteria
for initial diode leakage tests during their dedication
process.
As a result, the potential
exists that a diode was supplied
from the manufacturer
in a degraded
condition
and was not detected
during commercial
grade dedication
process.
In the absence of a manufacturing
defect, the diodes were sufficient
for the application.
FENOC agrees that loss of control power to the Division
2 SDG should not have occurred
and has taken corrective
actions to prevent recurrence.
Individual
components,
such as diodes, purchased
under our Quality Assurance
(QA) program are assumed to be reliable.
In the NRC's Enforcement
Policy, section 3.5, the NRC may refrain from issuing enforcement
action for violations
resulting
from matters not within a licensee's
control,
such as equipment
failures
that were not avoidable
by reasonable
licensee
QA measures
or management
controls.
FENOC believes
this to be the case in that this manufacturing
defect was not detected
through the supplier's
commercial
grade dedication
process.
Hence, FENOC believes
NRC discretion
is warranted based
on our understanding
of the deficiency
and the root cause conclusions.
FENOC respectfully
Attachment
Page 4 of 4 requests
that this performance
deficiency
be re-evaluated
and discretion
applied as per the NRC's Enforcement
Policy section 3.5. i