ML083020604
| ML083020604 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 10/27/2008 |
| From: | Reyes L Region 2 Administrator |
| To: | Brandi Hamilton Duke Energy Carolinas, Duke Power Co |
| References | |
| EA-08-220, IR-08-009 | |
| Download: ML083020604 (9) | |
See also: IR 05000369/2008009
Text
DEC 1
UNITED STATES
NUCLEAR REGULATORY COMMISSION
REGION II
SAM NUNN ATLANTA FEDERAL CENTER
61 FORSYTH STREET, SW, SUITE 23T85
ATLANTA, GEORGIA 30303-8931
October 27, 2008
Mr. Bruce H. Hamilton
Vice President
Duke Power Company, LLC
d/b/a Duke Energy Carolinas, LLC
McGuire Nuclear Station
12700 Hagers Ferry Road
Huntersville, NC 28078-8985
SUBJECT: FINAL SIGNIFICANCE DETERMINATION OF WHITE FINDING AND NOTICE
OF VIOLATION (NRC INSPECTION REPORT NO. 05000369/2008009 AND
05000370/2008009, MCGUIRE NUCLEAR STATION)
Dear Mr. Hamilton:
This letter provides you the final significance determination of the preliminary greater than Green
finding discussed in NRC Inspection Report No. 05000369/2008008 and 05000370/2008008,
dated August 20, 2008. The finding involved a failure to correct a significant condition adverse
to quality related to macro-fouling of the nuclear service water (RN) strainer backwash system.
The finding also involved an apparent violation of 10 CFR 50, Appendix B, Criterion XVI.
At your request, a Regulatory Conference was held on September 18, 2008, to discuss your
views on this issue. During the meeting, your staff described Duke Energy Carolinas, LLC
(DECs) assessment of the significance of the finding, and the corrective actions taken to resolve
it, including the root cause evaluation of the finding. DEC highlighted four differences between
its risk assessment and the NRCs preliminary estimate as documented in our Inspection Report
of August 20, 2008. In summary, the differences involved the period of RN system vulnerability,
the probability of RN pump failure, the loss of instrument air initiator frequency, and credit for
certain operator actions. Based on these differences, DEC concluded that the finding was of
very low safety significance (Green). Enclosure 2 provides additional details of the differences
as discussed above, and the NRCs basis for its final significance determination. DEC did not
contest the apparent violation of 10 CFR 50, Appendix B, Criterion XVI, but attributed the root
cause of the issue to a change to the plants configuration without a comprehensive
understanding of the design and licensing bases of the RN system.
After considering the information developed during the inspection and information provided by
DEC at the regulatory conference, the NRC has concluded that the finding is appropriately
characterized as White. In summary, the NRC agreed that a reduction to the change in the core
damage frequency estimate was appropriate, based on some of the factors and information
presented by DEC at the conference. Although the magnitude of the reduction was
considerable, the NRC concluded that the final significance of the finding is appropriately
characterized as low to moderate, increased importance to safety (i.e., White), as discussed in
detail in Enclosure 2.
DEC 2
You have 30 calendar days from the date of this letter to appeal the staff=s significance
determination for this finding. Such appeals will be considered to have merit only if they meet
the criteria given in NRC Inspection Manual Chapter 0609, Attachment 2.
The NRC has also determined that the failure to correct a significant condition adverse to quality
related to macro-fouling of the RN strainer backwash system is a violation of 10 CFR 50
Appendix B Criterion XVI, Corrective Action, as cited in the enclosed Notice of Violation (Notice).
The circumstances surrounding the violation were described in NRC Inspection Report No.
05000369/2008008 and 05000370/2008008. In accordance with the NRC Enforcement Policy,
the Notice is considered escalated enforcement action because it is associated with a White
finding. This violation is identified as: VIO 05000369,370/2008009-01, Failure to Take
Adequate Corrective Action for Implementation of Safety-Related RN Strainer Backwash.
Accordingly, for administrative purposes, apparent violation AV 05000369,370/2008008-01 is
considered closed.
You are required to respond to this letter and should follow the instructions specified in the
enclosed Notice when preparing your response.
Because plant performance for this issue has been determined to be beyond the licensee
response band, we will use the NRCs Action Matrix to determine the most appropriate NRC
response for this event. We will notify you, by separate correspondence, of that determination.
In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter, its
enclosures, and your response, will be made available electronically for public inspection in the
NRC Public Document Room or from the NRC=s document system (ADAMS), accessible from
the NRC Web site at http://www.nrc.gov/reading-rm/adams.html. To the extent possible, your
response should not include any personal privacy, proprietary, or safeguards information so that
it can be made available to the Public without redaction.
Sincerely,
/RA/
Luis A. Reyes
Regional Administrator
Docket Nos.: 50-369, 50-370
Enclosures:
1. Notice of Violation
2. NRC Basis for Final
Significance Determination
cc w/encls: (See page 3)
DEC 3
cc w/encls:
Bruce Hamilton Lisa F. Vaughn
Vice President Associate General Counsel
McGuire Nuclear Station Duke Energy Corporation
Duke Power Company, LLC d/b/a Duke 526 South Church Street-EC07H
Energy Carolinas, LLC Charlotte, NC 28202
Electronic Mail Distribution
Kathryn B. Nolan
Steven D. Capps Senior Counsel
Engineering Manager Duke Energy Corporation
Duke Power Company, LLC d/b/a Duke 526 South Church Street-EC07H
Energy Carolinas, LLC Charlotte, NC 28202
Electronic Mail Distribution
David A. Repka
Scotty L. Bradshaw Winston Strawn LLP
Training Manager Electronic Mail Distribution
Duke Power Company, LLC d/b/a Duke
Energy Carolinas, LLC County Manager of Mecklenburg County
Electronic Mail Distribution 720 East Fourth Street
Charlotte, NC 28202
Kenneth L. Ashe
Regulatory Compliance Manager Beverly O. Hall
Duke Power Company, LLC d/b/a Duke Chief, Radiation Protection Section
Energy Carolinas, LLC Department of Environmental Health
Electronic Mail Distribution N.C. Department of Environmental
Commerce & Natural Resources
R. L. Gill, Jr. Electronic Mail Distribution
Manager
Nuclear Regulatory Issues & Industry Affairs Dhiaa M. Jamil
Duke Power Company, LLC d/b/a Duke Group Executive and Chief Nuclear Officer
Energy Carolinas, LLC Duke Energy Carolinas, LLC
Electronic Mail Distribution Electronic Mail Distribution
Senior Resident Inspector
Duke Energy Corporation
William B. McGuire Nuclear Station
U.S. NRC
12700 Hagers Ferry Rd
Huntersville, NC 28078
_________________________ X SUNSI REVIEW COMPLETE
OFFICE RII:DRP RII:DRS RII:EICS RII:DRP RII:ORA NRR OE
SIGNATURE /RA/ /RA/ /RA By Wert/ /RA/ /E-mail/
NAME SRose RBernhard CEvans JMoorman VMcCree MCummgham JWray
DATE 10/10/08 10/09/08 10/14/08 10/ /2008 10/20/08 10/16/08 10/17/08
E-MAIL COPY? YES NO YES NO YES NO YES NO YES NO YES NO YES NO
NOTICE OF VIOLATION
Duke Power Company, LLC Docket Nos. 50-369, 50-370
d/b/a Duke Energy Carolinas, LLC License Nos. NPF-9, NPF-17
McGuire Nuclear Station EA-08-220
Units 1 and 2
During an inspection completed by the NRC on August 20, 2008, a violation of NRC
requirements was identified. In accordance with the NRC Enforcement Policy, the violation is
set forth below:
10 CFR 50 Appendix B Criterion XVI, Corrective Action, states that measures shall be
established to assure that conditions adverse to quality, such as deficiencies, deviations,
and non-conformances are promptly identified and corrected. In the case of significant
conditions adverse to quality, the measures shall assure that the cause of the condition
is determined and corrective action taken to preclude repetition. This requirement is
implemented through the Duke Quality Assurance Program Topical Report and
procedure NSD 208, Problem Identification Process.
Contrary to the above, between 2003 and August 7, 2007, the licensee failed to correct a
significant condition adverse to quality related to macro-fouling of the nuclear service
water (RN) strainers, in that the corrective action that was implemented failed to ensure
that the design and licensing basis required capability for manual strainer backwash be
maintained during accident conditions. Specifically, the 2003 plant modification that was
implemented to address macro-fouling (i.e., upgrade and reclassification of the strainer
backwash function to safety-related): (1) utilized non-safety-related instrument air (VI) to
maintain each RN pump=s strainer backwash discharge valve open, but did not provide a
means to manually open (or bypass) the discharge valve to support backwash operations
upon a loss of VI; and (2) did not account for the impact on timely operator response
from higher strainer macro-fouling rates and expected (nuisance) strainer differential
pressure alarms (without fouling) at the onset of high RN flow events (i.e., safety injection
(SI) and loss of VI). As such, there was a lack of reasonable assurance that the RN
system would be able to perform its safety-related function upon a SI or loss of VI event
during periods of macro-fouling.
This violation is associated with a White finding for Units 1 and 2.
Pursuant to the provisions of 10 CFR 2.201, Duke Energy Carolinas, LLC, is hereby required to
submit a written statement or explanation to the U.S. Nuclear Regulatory Commission, ATTN:
Document Control Desk, Washington, DC 20555-0001 with a copy to the Regional
Administrator, Region II, and a copy to the NRC Resident Inspector at the facility that is the
subject of this Notice, within 30 days of the date of the letter transmitting this Notice of Violation
(Notice). This reply should be clearly marked as a "Reply to a Notice of Violation; EA-08-220"
and should include for each violation: (1) the reason for the violation, or, if contested, the basis
for disputing the violation or severity level, (2) the corrective steps that have been taken and the
results achieved, (3) the corrective steps that will be taken to avoid further violations, and (4) the
date when full compliance will be achieved. Your response may reference or include previous
docketed correspondence, if the correspondence adequately addresses the required response.
If an adequate reply is not received within the time specified in this Notice, an order or a
Enclosure 1
2
Demand for Information may be issued as to why the license should not be modified,
suspended, or revoked, or why such other action as may be proper should not be taken. Where
good cause is shown, consideration will be given to extending the response time.
If you contest this enforcement action, you should also provide a copy of your response, with the
basis for your denial, to the Director, Office of Enforcement, United States Nuclear Regulatory
Commission, Washington, DC 20555-0001.
Because your response will be publicly available in the NRC Public Document Room or from the
NRC=s document system (ADAMS), to the extent possible, it should not include any personal
privacy, proprietary, or safeguards information so that it can be made available without
redaction. If personal privacy or proprietary information is necessary to provide an acceptable
response, then please provide a bracketed copy of your response that identifies the information
that should be protected and a redacted copy of your response that deletes such information. If
you request withholding of such material, you must specifically identify the portions of your
response that you seek to have withheld and provide in detail the bases for your claim of
withholding (e.g., explain why the disclosure of information will create an unwarranted invasion
of personal privacy or provide the information required by 10 CFR 2.390(b) to support a request
for withholding confidential commercial or financial information). If safeguards information is
necessary to provide an acceptable response, please provide the level of protection described in
In accordance with 10 CFR 19.11, you may be required to post this Notice within two working
days.
Dated this 27th day of October 2008
Enclosure 1
NRC Basis for Final Significance Determination
On September 18, 2008, the NRC held a Regulatory Conference with representatives of Duke
Energy Carolinas, LLC (DEC), McGuire Nuclear Station (MNS), to discuss a finding involving a
failure to correct a significant condition adverse to quality related to macro-fouling of the nuclear
service water (RN) strainer backwash system. At the conference, DEC highlighted four
differences between its risk assessment and the NRCs preliminary estimate as provided in NRC
Inspection Report No. 05000369,370/2008008, dated August 20, 2008. The information below
provides a summary of DECs information as presented at the conference, and the basis for the
NRCs final significance determination.
I. Event Frequency/Period of Macro-Fouling
DEC: The period of RN system vulnerability was reduced by: (1) eliminating periods of
discerned high flow due to testing and maintenance; (2) eliminating periods of discerned
transient flow conditions due to increasing/decreasing pump flow or starting/stopping a pump
(included partially clogged impulse line on the low side of the differential pressure (dP) switch
for the 2A RN pump); (3) eliminating periods of low frequency automatic backwashes that
were not considered to challenge the associated RN pump; and (4) attributing macro-fouling
solely to fish and therefore, based on dissolved oxygen levels, considered a limited seasonal
occurrence.
NRC: Lacking any other supporting information, all strainer backwash events over a year
period were initially considered. Reflective of DECs arguments presented at the Regulatory
Conference, fish was subsequently considered the only source of RN strainer macro-fouling
for the time period in question. Accordingly, the effective exposure period was narrowed to
7/15/07 - 8/10/07, based on bait fish concentrations shown in 2007 echogram survey results
provided by DEC. In effect, this eliminated those preceding backwash occurrences identified
by DEC to be attributable to transient flow conditions (including the partially clogged 2A RN
pump impulse line) and system maintenance/surveillance. It is likely that the fouling rates
are greater for those periods where HI strainer dP alarms occur more frequently. However,
because definitive strainer fouling rate data (actual or from testing) does not exist without the
influence of the 900 gpm backwash, several sensitivity risk studies were conducted. One
calculation was made using the assumptions from the original Significance Determination
Process (SDP), only modified for the assumption that the only macro-fouling that occurs is
from fish between 7/15/07 - 8/10/07. Another calculation was made assuming all HI strainer
dP alarm occurrences within the effective time period (7/15/07 - 8/10/07) were reflective of
fish in the common low level intake RN pump suction and, therefore, equally detrimental to
all RN pumps, no mater what the frequency. In addition, if an initiating event occurred prior
to a fish run, and if the strainer backwash function had not been reset, additional exposure
time was added. The second calculation added this time prior to each HI dP occurrence,
whereas the first calculation just added a single 24-hour exposure to the total hours.
II. Probability of RN Pump Failure
DEC: The exposure period was further reduced by 50% based on perceived pump
survivability, from net positive suction head (NPSH)/pump flow testing results, during
Enclosure 2
2
discerned periods of low fouling (i.e., backwashes less than 1 per hour, 6 or less
backwashes total on any one train, and quick clearing alarms). Inherent in this reduction,
was the assumption of a linear strainer fouling rate and 1 psid across the strainer for each HI
dP alarm (increasing no more than 6 psid). Based on DECs NPSH/pump flow testing
results, an additional 6 psid across the strainer would not have an adverse impact on the
associated RN pump and its ability to provide sufficient flow.
NRC: It is acknowledged that DECs NPSH/pump flow testing demonstrated RN pump
survivability with as little as 8 feet of NPSH and 9500 gpm flow. However, in absence of
definitive strainer fouling rate data (without the influence of the 900 gpm backwash) that
relates fish input to strainer dP, the impact of strainer fouling cannot be bounded within the
test conditions of the pump. Similarly, the application of linear fouling rates and quick
clearing alarms that result in no more than 6 psid across the strainer is not justifiable. As
such, an additional 50% pump survivability factor was not credited.
III. Loss of Instrument Air Initiator Frequency
DEC: The NUREG CR/6928 data from 2002 was updated using MNS data and two industry-
related events [7.4E-3/yr].
NRC: The NUREG CR/6928 data from 2002 was updated using applicable industry data
(three events) [9.69E-3/yr]. Use of this value is consistent with the usage rules for the NRCs
SDP. The licensee has a plant specific Loss of Instrument Air fault tree. The third industry
event was credited but had a lower impact. The NRC uses a single initiating event value (i.e.
no fault tree).
IV. Additional Operator Action
(a) Recovery of RN with the other (donor) Unit or the containment ventilation cooling water
system (RV).
DEC: This recovery action was applied to safety injection (SI) events on the effected
Unit. It was assumed that the donor Unit is not in a SI event and has two RN pumps
available. A human reliability analysis (HRA) failure rate of 5.2E-2 was applied for use of
the Unit 2 crosstie, and a failure rate of 8E-4 was applied for use of either RN or RV.
NRC: DEC has not performed a flow calculation which proves the donor pump is
capable of supplying any essential heat exchanger required flow rates on either Unit
when aligned to the Unit crossover supply header. However, it is recognized that
procedural guidance was in place for the subject exposure period to use the second RN
pump from the donor Unit to supply the degraded Unit. During those times, it is
recognized that the risk to the donor Unit would increase somewhat. Overall, a failure
rate of 0.1 was applied for cross tying RN to account for the human actions and the
chance that a strainer failure will occur on the donor unit due to macro-fouling or other
causes. The NRC assumed that the RV strainers fouling will be alarmed on the plant
operator aid computer. Also, the operators will be in AP-20, which would have them
cross-tie and monitor RV. However, credit for RV did not seem as reasonable, because
of the reasons previously stated in the Phase 3 Summary that was enclosed in
Enclosure 2
3
Inspection Report 05000369,370/2008008, dated August 20, 2008. Those reasons
included the reduced flow available from the RV pumps, their susceptibility to strainer
macro-fouling due to their reliance on the low level intake as a source of water, and the
lack of significant/hierarchical cues/alarms that the RV system is fouled.
(b) Use of Condensate for Secondary Side Heat Removal
DEC: This recovery action was applied to loss of instrument air sequences. Having
recently tested the manual valves and check valves in the steam generator tempering
lines, DEC applied an HRA failure rate of 1.7E-2.
NRC: It is agreed that the use of condensate for secondary side heat removal is a viable
recovery action for loss of instrument air sequences. Due to the multiple actions required
outside the control room and dependence between the event and previously performed
human actions, a failure rate of 0.1 was applied.
Based on the above, the NRC performed calculations to estimate the change in core
damage frequency. The calculation incorporated those items agreed to above, and used
a method for calculating exposure period that treated the HI strainer dP alarm
occurrences within the reduced exposure period as equally detrimental to all RN pumps.
In addition, the exposure period included times that compensate for the initiating events
that could occur prior to periods of high strainer fouling. The NRCs best estimate of the
change in CDF is 4.7E-6 for both units. Accordingly, this is assessed to be a White
finding.
Enclosure 2