ML14307B038
| ML14307B038 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 11/03/2014 |
| From: | Troy Pruett NRC/RGN-IV/DRP |
| To: | Limpias O Nebraska Public Power District (NPPD) |
| George G | |
| References | |
| EA-14-090 IR 2013005 | |
| Download: ML14307B038 (11) | |
See also: IR 05000298/2013005
Text
UNITED STATES
NUCLEAR REGULATORY COMMISSION
REGION IV
1600 E LAMAR BLVD
ARLINGTON, TX 76011-4511
November 3, 2014
Oscar A. Limpias, Vice President - Nuclear
and Chief Nuclear Officer
Nebraska Public Power District
Cooper Nuclear Station
P.O. Box 98
Brownville, NE 68321-0098
SUBJECT: RESPONSE TO DISPUTED NON-CITED VIOLATION 05000298/2013005-01,
"FAILURE TO PROMPTLY IDENTIFY AND CORRECT A CONDITION
ADVERSE TO QUALITY"
Dear Mr. Limpias:
In your letter of May 20, 2014, Nebraska Public Power District (NPPD) contests a Green NRC-
identified violation that was dispositioned as a non-cited violation (NCV). Specifically, NPPD
disputes the use of 10 CFR Part 50, Appendix B, Criterion XVI, Corrective Action, as the basis
for the NCV. The NCV involved a failure to promptly identify and correct a condition adverse to
quality involving an inadequate evaluation of the diesel generator fuel oil (DGFO) storage tank
vents and their ability to perform the specified safety function in the event of a tornado missile
impact.
On June 13, 2014, we acknowledged your letter and informed you that we would review your
basis for contesting the NCV and provide the results of our evaluation by written response. The
NRC performed a detailed review of the facts associated with this violation and the use of
10 CFR Part 50, Appendix B, Criterion XVI. In addition, we reviewed NPPDs engineering
evaluation (EE), EE 10-060, Evaluation of the Diesel Generator Fuel Oil Tank Vents After a
Tornado Strike, Revision 0.
In your May 20 letter, you stated, in part, that the evaluation of the DGFO storage tank vents
ability to withstand a tornado missile strike was adequately resolved under Condition Report
CR-CNS-2010-05211. This Condition Report CR referenced engineering evaluation EE 10-060
which validated that the DGFO storage tanks and vents would remain operable after a tornado
missile strike to the vents. However, the NRC found that engineering evaluation EE 10-060
contains no definitive analytical basis to conclude that the vent lines would not be damaged by
postulated tornado generated missiles and the requisite corrective and preventive measures
failed to address the nonconforming design condition (see enclosure). Therefore, the NRC has
concluded that the violation occurred as stated in the aforementioned inspection report and the
NCV will stand.
O. Limpias -2-
In accordance with 10 CFR 2.390 of the NRCs Rules of Practice and Procedure, a copy of
this letter will be available electronically for public inspection in the NRCs Agencywide
Document Access and Management System (ADAMS). ADAMS is accessible from the NRC
Website at http://www.nrc.gov/reading-rm/adams.html (the Public Reading Room).
Sincerely,
/RA/
Troy W. Pruett, Acting Director
Division of Reactor Projects
Docket No.: 50-298
License No.: DPR-46
Enclosure:
1. NRC Evaluation and Conclusion
cc w/ enclosure:
Electronic Distribution for CNS
SUNSI Review ADAMS Publicly Available Non-Sensitive Keyword:
By: RML Yes No Non-Publicly Available Sensitive NRC-002
OFFICE DRS/SRI:EB1 DRP/C:PBC DRS/EB1:BC SES:ACES C:ACES OE DRP:D
NAME RLatta:RDL GGeorge TFarnholtz RBrowder VCampbell GGulla TPruett
SIGNATURE /RA/ /RA DAllen /RA WSifre /RA/CMaier /RA/ /RA/E /RA/
for/ for/ for
DATE 8/20/14 8/20/14 8/21/14 10/28/14 10/29/14 10/30/14 10/31/14
Letter to Oscar A. Limpias from Troy W. Pruett dated November 3, 2014
SUBJECT: RESPONSE TO DISPUTED NON-CITED VIOLATION 05000298/2013005-01,
"FAILURE TO PROMPTLY IDENTIFY AND CORRECT A CONDITION
ADVERSE TO QUALITY"
Electronic distribution by RIV:
Regional Administrator (Marc.Dapas@nrc.gov)
Deputy Regional Administrator (Kriss.Kennedy@nrc.gov)
Acting DRP Director (Troy.Pruett@nrc.gov)
Acting DRP Deputy Director (Jason.Kozal@nrc.gov)
DRS Director (Anton.Vegel@nrc.gov)
DRS Deputy Director (Jeff.Clark@nrc.gov)
Senior Resident Inspector (Jeffrey.Josey@nrc.gov)
Resident Inspector (Christopher.Henderson@nrc.gov)
Branch Chief, DRP/C (Gerond.George@nrc.gov)
Senior Project Engineer (Ray.Azua@nrc.gov)
Project Engineer (Paul.Nizov@nrc.gov)
Project Engineer (Michael.Langelier@nrc.gov)
CNS Administrative Assistant (Amy.Elam@nrc.gov)
Public Affairs Officer (Victor.Dricks@nrc.gov)
Public Affairs Officer (Lara.Uselding@nrc.gov)
Project Manager (Eric.Oesterle@nrc.gov)
Branch Chief, DRS/TSB (Geoffrey.Miller@nrc.gov)
ACES (R4Enforcement.Resource@nrc.gov)
RITS Coordinator (Marisa.Herrera@nrc.gov)
Regional Counsel (Karla.Fuller@nrc.gov)
Technical Support Assistant (Loretta.Williams@nrc.gov)
Congressional Affairs Officer (Jenny.Weil@nrc.gov)
RIV Congressional Affairs Officer (Angel. Moreno@nrc.gov)
RidsOEMail Resource
OE Specialist (Gerald.Gulla@nrc.gov)
NRC EVALUATION AND CONCLUSION
Statement of Violation 05000298/2013005-01
As documented in NRC Inspection Report 05000298/2013005, the subject non-cited violation
was described as follows:
Failure to Promptly Identify and Correct a Condition Adverse to Quality
Introduction. The inspectors identified a Green non-cited violation of 10 CFR Part 50,
Appendix B, Criterion XVI, Corrective Actions, associated with NPPDs failure to promptly
identify and correct a condition adverse to quality. Specifically, from July 2010 to present, the
licensee failed to properly evaluate the diesel generator fuel oil (DGFO) storage tank vents to
demonstrate their ability to perform their specified safety function in the event of a tornado
generated missile.
Description. While performing plant walk downs, the inspectors noted that the DGFO storage
tank vent lines appeared to be susceptible to tornado missile impact. Specifically, the vent lines
were approximately 1 foot apart, and the inspectors questioned whether a single tornado
generated missile could render both vent lines incapable of performing their intended safety
function. Based on the review of pertinent licensing basis documents, the inspectors
determined that Appendix F of the USAR states, in part, that the licensee complies with Draft
General Design Criteria GDC-2, published July 11, 1967, which requires that systems and
components needed for accident mitigation remain fully functional before, during, and after a
tornado event. It was also noted that Updated Safety Analysis Report (USAR) Chapter I-5,
Section 5.2, defines Class I structures and equipment as, Structures and equipment whose
failure could cause significant release of radioactivity or which are vital to a safe shutdown of
the plant and removal of decay and sensible heat. Additionally, USAR Chapter XII-2,
Section 2.1.2.3, identifies the Standby Diesel Generator System and Auxiliaries as Seismic
Class I equipment. However, based on the review of the licensees design basis documents,
the inspectors were unable to locate an evaluation of the safety-related vent lines that
demonstrated their ability to withstand a tornado missile impact.
The inspectors also noted that Station Procedure 5.1 WEATHER, Operations During Weather
Watches and Warnings, Revision 12, Section 7.4, directed that, in the event of a tornado
impact to the site, operators would inspect the vent lines, and if they were damaged, one of the
diesel generator fuel oil tank fill lines was to be opened. The inspectors determined this to be a
compensatory action, which brought into question whether the vent lines were adequately
protected from tornado generated missiles.
In response to these issues, NPPD initiated Condition Report CR-CNS-2013-03720. As
documented in this condition report, the licensee identified that during the 2010 NRC
Component Design Basis Inspection (CDBI), NRC inspectors had similar questions and
Condition Report CR-CNS-2010-05211 had been initiated to address these questions.
However, the licensee subsequently closed Condition Report CR-CNS-2013-03720 with no
explicit corrective actions specified.
Enclosure
Based on the review of Condition Report CR-CNS-2010-05211, it was noted that it had been
initiated in response to questions regarding a statement in the licensees design control
document for the diesel generators which dealt with tornado missile protection for the DGFO
storage tank vents.
Specifically, the design control document stated, in part, that The vent pipe concerns were
satisfactorily resolved during the 1991 EDSFI, and the inspectors had requested NPPDs
evaluation for the DGFO storage tank vents and fill valves with respect to tornado missile
protection. NPPD examined the basis for this statement and determined that it had been
erroneously identified during their evaluation of a finding at another facility where the NRC had
questioned the adequacy of fill and vent connections with respect to impact from a tornado
generated missile. However, during their review, NPPD determined that a documented
evaluation of the fill and vent lines ability to withstand a tornado missile impact could not be
located.
The corrective actions specified in Condition Report CR-CNS-2010-05211 also included
direction to provide a formal analysis of the diesel generator fuel oil storage tank vent lines
pertaining to tornado missile protection. In response to this action, NPPD developed EE 10-
060, Evaluation of the Diesel Generator Fuel Oil Tanks. The inspectors reviewed EE 10-060
and determined that it did not adequately evaluate the DGFO vent lines with regard to their
ability to withstand tornado generated missiles. Alternatively, the EE assumed that the vents
were short runs of pipe and if impacted by a missile there would be no damage to the fuel oil
storage tank. The evaluation also discussed manual action condition reports that could be
implemented if the vent lines were damaged by a tornado generated missile.
The inspectors determined that the assumptions associated with the vent lines ability to
withstand a missile impact were inadequate and that NPPD had failed to correct a previously
identified condition adverse to quality. Specifically, Condition Report CR-CNS-2010-05211
identified that NPPD did not have a documented evaluation that demonstrated the DGFO vent
lines ability to withstand a tornado missile impact, and the corrective actions to address this
condition were based on inadequate assumptions in the engineering evaluation.
Analysis. NPPDs failure to promptly identify and correct a condition adverse to quality was a
performance deficiency. This performance deficiency is more than minor, and therefore a
finding, because it is associated with the design control attribute of the Mitigating Systems
Cornerstone, and affected the cornerstone objective to ensure the availability, reliability, and
capability of systems that respond to initiating events to prevent undesirable consequences.
Using Inspection Manual Chapter 0609, Appendix A, The Significance Determination Process
(SDP) for Findings At-Power, dated July 1, 2012, inspectors determined this finding to have
very low safety significance (Green) because it: (1) was not a deficiency affecting the design
and qualification of a mitigating structure, system, or component, and did not result in a loss of
operability or functionality; (2) did not represent a loss of system and/or function; (3) did not
represent an actual loss of function of at least a single train for longer allowed outage time, or
two separate safety systems out-of-service for longer than their technical specification allowed
outage time; and (4) did not represent an actual loss of function of one or more nontechnical
specification trains of equipment designated as high safety significance in accordance with the
licensees maintenance rule program. The finding has a cross-cutting aspect in the area of
human performance associated with decision-making component because the licensee did not
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ensure that the proposed action was safe in order to proceed, rather than unsafe to disapprove
the action H.1(b).
Enforcement. Title 10 CFR Part 50, Appendix B, Criterion XVI, Corrective Actions, requires,
in part, that measures shall be established to assure that conditions adverse to quality, such as
failures, malfunctions, deficiencies, deviations, defective material and equipment, and
nonconformances are promptly identified and corrected. Contrary to the above, from July 2010
to present, measures established by NPPD failed to assure that an identified condition adverse
to quality was corrected. Specifically, NPPD failed to evaluate the lack of tornado missile
protection for the DGFO storage tank vents and demonstrate their ability to perform their
specified safety function in the event of a tornado missile impact. This violation is being
treated as a non-cited violation, consistent with Section 2.3.2.a, of the Enforcement Policy.
The violation was entered into NPPDs corrective action program as Condition Report
CR-CNS-2014-00146. (NCV 05000298/2013005-01, Failure to Promptly Identify and Correct a
Condition Adverse to Quality).
Summary of NPPDs Response
In response to violation 05000298/2013005-01, NPPD provided a reply contained in a letter
from O. Limpias to the NRC dated May 20, 2014, which disputes the use of 10 CFR Part 50,
Appendix B, Criterion XVI, Corrective Action, as the basis for the Non-Cited Violation.
As stated in this letter, NPPD denied that a violation of NRC requirements had occurred,
in that, NPPD had previously evaluated this condition as documented in Condition Report
CR CNS-2010-05211, which was initiated in response to a question identified during the
2010 Component Design Basis Inspection (CDBI). NPPD also indicated that they had re-
evaluated these results and concluded the original evaluation remained valid. Specifically,
Engineering Evaluation (EE)10-060, Evaluation of the Diesel Generator Fuel Oil Tank Vents
After a Tornado Strike, Revision 00, evaluated the DGFO storage tank design to satisfy the
design basis events delineated in IEEE-308-1970, Table 1, consistent with the pre-General
Design Criteria 2 requirements contained in Appendix F of OPPDs Updated Safety Analysis
Report (USAR). As stated in your letter, EE-10-060 provided a technical basis on the location of
the vents, how much of the vents are exposed to missile impacts, and also discussed that these
vent lines are cast in place thus minimizing the amount of load transferred to the DGFO storage
tanks by a missile strike. Therefore, the EE concluded that transfer of the minimal load would
not damage any part of the tank below the fuel level, validating that the DGFO storage tanks
and vents would remain operable after a tornado strike to the vents.
The method of evaluation for assessing the ruggedness of these structural components was
based on guidance contained in USAR Appendix C, Section 3.1.2, Components Designed
Primarily by Empirical Methods, which contains provisions for component design primarily by
empirical methods.
Additionally, NPPD indicated in its letter that EE-10-060 included a postulated impact to the
DGFO storage tank vents after a design basis tornado and recommended a defense-in-depth
action for the operations staff to visually check the DGFO storage tank vents for any
obstructions. This information was provided to document the basis made in response to the
1991 Electrical Distribution System Functional Inspection (EDSFI) comment that Cooper
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Nuclear Station (CNS) did not require any operator actions to ensure that the vent or fill lines
were not obstructed as noted in the Diesel Generator Design Criteria Document material.
NPPDs letter also states that, during the 2013 fourth quarter inspection period, the NRC
Resident Inspectors questioned the technical basis provided in EE-10-060. NPPDs letter
further stated that, the original EE preparer and the responsible supervisor were no longer
employed by NPPD. Accordingly, NPPDs Design Engineering staff completed a sensitivity
calculation, NEDC 13-046, DG Storage Tank Vent Line Tornado Missile Durability. This
calculation utilized similar design inputs and basis from NEDC 11-077, DG Day Tank Vent
Line Missile Protection Evaluation, which addressed the previous question identified in the
2010 CDBI inspection.
As noted in NPPDs letter, the results of NEDC 13-046 are similar to NEDC 11-077, in that the
vent line stays rigid and does not crimp or bend, thereby maintaining its venting capabilities.
The letter indicated that the vent piping construction is also similar, in that, both the DGFO
storage tank vents (2-inch diameter) and the Diesel Generator Day Tank vents (6-inch diameter)
use schedule 40 steel pipe. In addition, the letter provided another comparison that if the
larger vent is robust enough to handle a tornado missile, then the smaller pipe would be just
as robust due to the similarity in pipe wall thickness. Furthermore, NPPDs letter stated that;
NEDC 13-046 independently validated the technical adequacy of the conclusions from
EE 10-060, that the DGFO storage tanks would remain operable after a tornado strike to the
vents.
In conclusion, NPPDs violation denial letter stated that the previous NRC CDBI question related
to the DGFO storage tank vents ability to withstand a tornado missile strike was adequately
resolved under Condition Report CR-CNS-2010-05211 and appropriately evaluated in a timely
manner commensurate with 10 CFR 50, Appendix B, Criterion XVI.
NRC Analysis
Consistent with the guidance provided in Policy Guide 0560-6 Region IV Enforcement
Procedures, NRC staff performed an independent review of the documentation associated with
this finding. Based on the results of this review, it was determined that the requirements of the
Draft General Design Criteria, Criterion 2, published July 11, 1967, clearly establish the design
function of systems and components of reactor facilities, which are essential to the prevention of
accidents that could affect public health and safety or to mitigation of its consequences. These
systems and components are required to be designed, fabricated, and erected to performance
standards that will enable the facility to withstand, without loss of the capability to protect the
public, the additional forces that might be imposed by natural phenomena such as tornados.
Furthermore, the system design basis requirements contained in the Cooper Nuclear Station
USAR, Chapter XII, Section 2.3.3.2.2, Tornado Generated Missiles, specifies that all Seismic
Class I Structures are designed to provide protection against the following tornado generated
missiles;
- A 35-foot long utility pole with a 14-inch butt with an impact velocity of 200 miles per hour.
- A one-ton missile such as compact-type automobile with an impact velocity of 100 miles
per hour and a contact area of 25 square feet.
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- A two-inch extra heavy pipe, 12 feet long.
- Any other missile resulting from failure of a structure or component or one which has
potential of being lifted from storage or working areas at the site.
Additionally, Cooper Nuclear Stations Design Basis for the DGFO system includes the following
requirements;
- The standby diesel generator system must be capable of withstanding the most severe
conditions anticipated at the location of the plant. As referenced in USAR, Chapter VIII,
the design basis events are described in IEEE-308-1970, Table I. This table includes
postulated earthquake, wind, hurricane, and tornado effects as natural phenomena
design bases. Additionally, Table I of IEEE-308-1970 lists accident generated missiles
as one of the events that the emergency diesel system must be designed to withstand.
- The fuel oil subsystem must provide sufficient fuel to operate the standby diesel
generator under all postulated conditions.
- The safety classification of the essential emergency diesel system including the diesel
fuel oil tank vents is Seismic Class 1.
The NRC concluded that the DGFO storage tank Seismic Class 1 vents were not assured to be
designed, fabricated, and erected to withstand the additional forces imposed by natural
phenomena such as tornados, as required by the licensing basis stated above. Specifically, the
evaluation performed in accordance with CNS-CR-2010-05211 and the associated EE-10-060,
did not adequately demonstrate that the DGFO storage tank vent lines would maintain its ability
to withstand a postulated tornado missile impact without loss of function. Although the
evaluation references the location of the vents, the area of exposure of the vents to missile
impact, and generally discusses the material composition of the vents and the inferred minimal
load transferred to the DGFO storage tanks, no definitive analytical basis was identified for
concluding that the vent lines would not be damaged by the postulated tornado generated
missile and they would remain functional. Although NPPDs compensatory actions dealt with
the initial operability condition, the requisite corrective and preventive measures failed to
address the nonconforming design condition, concerning the DGFO storage tank vents
tornado missile protection, initially identified as a performance deficiency in NRC CDBI
Report 05000298/2010007.
Based on the independent review of EE-10-060, it was determined that the document did not
technically evaluate the DGFO vent lines with regard to its ability to withstand the full spectrum
of tornado generated missiles described above. Specifically, EE-10-060 incorrectly assumed
that the vents were low profile rigid sections of pipe and if impacted by a missile there would be
no damage to the fuel oil storage tank. EE-10-060 further stated that If both vents are clamped
and the vents are not restored promptly, one or both of the fill caps can be opened to provide
venting of the tank. However, this compensatory action failed to adequately address the
dynamic effects of a postulated tornado missile impact on the DGFO vent lines. Furthermore, it
was determined that although EE-10-060 identified that USAR Section 2.3.3.2.2 Tornado
Generated Missiles, requires that all Class I Structures are to provide protection against
tornado generated missiles, no corresponding corrective actions were initiated to address this
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documented design deficiency. Additionally, USAR Section 2.1.2.3 states that the Standby
Diesel Generator System and Auxiliaries are Class I Equipment. However, EE-10-060 failed to
identify any specific corrective measures to address this nonconforming condition.
As stated in Manual Chapter 0326, Section 07.02, Timing of Corrective Actions, the NRCs
expectations are that licensees establish a schedule for completing corrective actions when a
structure, system, or component is determined to be degraded or nonconforming. This
guidance further states that licensees should address any degraded or nonconforming condition
in a timeframe commensurate with the safety significance of the condition. If the licensee does
not resolve the degraded or nonconforming condition at the first available opportunity or does
not appropriately justify a longer completion schedule, then the staff would conclude that
corrective action has not been timely and would consider taking enforcement action.
Based on the guidance contained in Manual Chapter 0326, the unprotected DGFO storage tank
vents represent a nonconforming condition. Specifically, the installed vents do not comply with
the established design requirements of protecting Seismic Class I components from postulated
tornado generated missiles and are, therefore, nonconforming. Additionally, the independent
review of NPPDs violation denial, which relies on the postulated plastic deformation of the
2-inch carbon steel vent lines, is non-conservative, in that, it does not account for the worst
case conditions and did not include the full spectrum of missile hazards specified in USAR
Chapter XII, Section 2.3.3.2.2, Tornado Generated Missiles.
Furthermore, as described in NPPDs violation denial letter, the method of evaluation for
assessing the ruggedness of these structural components was predicated on guidance from
USAR Appendix C, Section 3.1.2, Components Designed Primarily by Empirical Methods.
Based on the review of this methodology, it was determined that the guidance provided in
Section 3.1.2 is limited to the use of testing and experienced-based seismic qualification of
equipment for use in nuclear power plants. However, given the absence of explicit industry
testing data and empirical experience related to missile strikes on piping, the use of this seismic
qualification methodology to justify the nonconforming condition associated with protection of
the DGFO storage tank vents from tornado generated missiles is inappropriate.
Additionally, as stated in NPPDs violation denial letter, the results of NEDC 13-046 are similar
to NEDC 11-077, in that the vent line stays rigid and does not crimp or bend, thereby
maintaining its venting capabilities. The letter also asserts that NEDC 13-046 independently
validated the technical adequacy of the conclusions from EE-10-060, that the DGFO storage
tanks would remain operable after a postulated tornado missile strike to the vents. However,
during the independent review of NEDC 13-046 and NEDC 11-077, it was determined that both
of these calculations erroneously classified the vent lines as non-Seismic Class1 components.
Therefore, the DGFO vent lines appear to have been inappropriately evaluated against the
tornado missile spectrum for non-Seismic Class1 equipment. It was also determined that
NEDC 13-046 incorrectly references documents that are not part of CNS current licensing basis
and that this calculation contains non-conservative assumptions (i.e. vents were low profile
rigid sections of pipe) regarding the modeling of the vent lines. Therefore, the results of
NEDC 13-046 and NEDC 11-077 were determined to be technically inaccurate and immaterial
to the nonconforming condition associated with the DGFO storage tank vents.
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NRC Conclusion
We have concluded that the finding and NCV for failing to assure that an identified condition
adverse to quality was promptly corrected to meet the requirements in 10 CFR Part 50,
Appendix B, Criterion XVI as documented in NRC Inspection Report 05000298/2013005 are
valid. The failure to perform a proper engineering evaluation of the DGFO storage tank vents to
demonstrate the ability to perform its specified safety function as required by the licensing bases
in the event of a tornado generated missile has not been documented.
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