ML050910127
| ML050910127 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 03/31/2005 |
| From: | Howell A NRC/RGN-IV/DRP |
| To: | Edington R Nebraska Public Power District (NPPD) |
| References | |
| EA-04-131, FOIA/PA-2006-0007 IR-04-014 | |
| Download: ML050910127 (10) | |
See also: IR 05000298/2004014
Text
March 31, 2005
Randall K. Edington, Vice
President-Nuclear and CNO
Nebraska Public Power District
P.O. Box 98
Brownville, NE 68321
SUBJECT:
COOPER NUCLEAR STATION - NRC INSPECTION REPORT
05000298/2004014 - FINAL SIGNIFICANCE DETERMINATION FOR A
PRELIMINARY GREATER THAN GREEN FINDING
Dear Mr. Edington:
The purpose of this letter is to provide you the final results of our significance determination of
the preliminary Greater than Green finding identified in the subject inspection report dated
August 12, 2004. The finding involved the failure to restore the Cooper Nuclear Station
Division 2 service water gland seal water supply to a normal alignment following maintenance
on the discharge strainer. This error, which occurred on January 21, 2004, resulted in
Division 2 of the service water system and Emergency Diesel Generator 2 being inoperable for
21 days. The finding was documented in NRC Inspection Report 05000298/2004014.
In the cover letter of the subject report we informed Nebraska Public Power District (NPPD) of
the NRCs preliminary conclusion and provided NPPD an opportunity to request a regulatory
conference on this matter. On September 27, 2004, a regulatory conference was conducted at
the NRC Region IV office in Arlington, Texas. During this meeting NPPD described their
assessment of the findings, including a detailed discussion of a service water pump test that
determined the impact of running the pump without gland seal water. Additionally, NPPD stated
they agreed with the apparent violation related to this finding and described the corrective
actions taken for the underlying performance deficiency.
The NRC has considered the information developed during the inspection, the additional
information you provided in your letter dated August 9, 2004, the information you provided at
the Regulatory Conference, and the information you provided in your October 7, 2004, letter
following the conference. After evaluating this information, the NRC concluded that a more
realistic failure probability for the service water system should be used. This new probability
reflected the results of your testing, as well as the inherent capabilities of the system.
Additionally, the NRC reviewed information you provided regarding the change in large early
release frequency (LERF) that resulted from the performance deficiency. NRC Inspection
Manual Chapter 0609, Appendix H, defines LERF as The frequency of those accidents leading
Nebraska Public Power District
-2-
to a significant, unmitigated release from containment in a time frame prior to effective
evacuation of the close-in population such that there is a potential for early health effects.
NPPD provided information asserting that effective evacuation of the close-in population could
be achieved prior to a release of radioactivity during the dominant accident sequences. After
review of accident progression timing, the staff determined that the dominant sequences
affected by this finding were not LERF contributors.
On the basis of this information, the NRC has concluded that the inspection finding is of very
low safety significance (Green). The final significance determination is attached as an
enclosure to this letter. The NRC has also determined that a violation was associated with this
issue involving the failure of Clearance Order SWB-1-4324147 SW-STNR-B to provide
adequate instructions to restore the service water system to an operable configuration following
completion of maintenance activities on January 21, 2004. This violation is being treated as a
noncited violation, consistent with Section VI.A of the Enforcement Policy.
If you contest the violation or its significance, you should provide a response within 30 days of
the date of this inspection report, with the basis for your denial, to the U.S. Nuclear Regulatory
Commission, ATTN: Document Control Desk, Washington, DC 20555-0001, with copies to the
Regional Administrator, U.S. Nuclear Regulatory Commission, Region IV, 611 Ryan Plaza
Drive, Suite 400, Arlington, Texas 76011-4005; the Director, Office of Enforcement, U.S.
Nuclear Regulatory Commission, Washington, DC 20555-0001; and the NRC Resident
Inspector at the Cooper Nuclear Station facility.
In accordance with 10 CFR 2.390 of the NRCs Rules of Practice, a copy of this letter
and its enclosures will be available electronically for public inspection in the NRC Public
Document Room or from the Publicly Available Records (PARS) component of NRCs
document system (ADAMS). ADAMS is accessible from the NRC Web site at
http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).
Sincerely,
/RA/ by AVegel for
Arthur T. Howell III, Director
Division of Reactor Projects
Docket: 50-298
License: DPR-46
cc:
Michael T. Boyce, Nuclear Asset Manager
Nebraska Public Power District
1414 15th Street
Columbus, NE 68601
Nebraska Public Power District
-3-
John C. McClure, Vice President
and General Counsel
Nebraska Public Power District
P.O. Box 499
Columbus, NE 68602-0499
P. V. Fleming, Licensing Manager
Nebraska Public Power District
P.O. Box 98
Brownville, NE 68321
Michael J. Linder, Director
Nebraska Department of
Environmental Quality
P.O. Box 98922
Lincoln, NE 68509-8922
Chairman
Nemaha County Board of Commissioners
Nemaha County Courthouse
1824 N Street
Auburn, NE 68305
Sue Semerena, Section Administrator
Nebraska Health and Human Services System
Division of Public Health Assurance
Consumer Services Section
301 Centennial Mall, South
P.O. Box 95007
Lincoln, NE 68509-5007
Ronald A. Kucera, Deputy Director
for Public Policy
Department of Natural Resources
P.O. Box 176
Jefferson City, MO 65101
Director
State Emergency Management Agency
P.O. Box 116
Jefferson City, MO 65102-0116
Nebraska Public Power District
-4-
Chief, Radiation and Asbestos
Control Section
Kansas Department of Health
and Environment
Bureau of Air and Radiation
1000 SW Jackson, Suite 310
Topeka, KS 66612-1366
Daniel K. McGhee
Bureau of Radiological Health
Iowa Department of Public Health
401 SW 7th Street, Suite D
Des Moines, IA 50309
William J. Fehrman, President
and Chief Executive Officer
Nebraska Public Power District
1414 15th Street
Columbus, NE 68601
Jerry C. Roberts, Director of
Nuclear Safety Assurance
Nebraska Public Power District
P.O. Box 98
Brownville, NE 68321
Chief Technological Services Branch
National Preparedness Division
Department of Homeland Security
Emergency Preparedness & Response Directorate
FEMA Region VII
2323 Grand Boulevard, Suite 900
Kansas City, MO 64108-2670
Nebraska Public Power District
-5-
Electronic distribution by RIV:
Regional Administrator (BSM1)
DRP Director (ATH)
DRS Director (DDC)
DRS Deputy Director (KSW)
Senior Resident Inspector (SCS)
Branch Chief, DRP/C (MCH2)
Senior Project Engineer, DRP/C (WCW)
Team Leader, DRP/TSS (RLN1)
RITS Coordinator (KEG)
RidsNrrDipmIipb
J. Dixon-Herrity, OEDO RIV Coordinator (JLD)
CNS Site Secretary (SLN)
W. A. Maier, RSLO (WAM)
G. F. Sanborn, D:ACES (GFS)
K. S. Fuller, RC (KSF)
F. J. Congel, OE (FJC)
OE:EA File (RidsOeMailCenter)
SISP Review Completed: __mch____
ADAMS: / Yes
G No Initials: _mch__
/ Publicly Available G Non-Publicly Available G Sensitive
/ Non-Sensitive
R:\\_CNS\\2004\\CN2004-14RP Final Determination.wpd
RIV:C:DRP/C
SRA:DRS
D:ACES
D:DRP
MCHay;df
DPLoveless
GFSanborn
ATHowell III
/RA/
/RA/
/RA/
AVegel for
3/15/05
3/22/05
3/21/05
3/31/05
OFFICIAL RECORD COPY
T=Telephone E=E-mail F=Fax
Enclosure
Final Significance Determination
Cooper Nuclear Station
Service Water Gland Seal Water Configuration Deficiency
The NRC reviewed the information provided by the licensee in their analysis, PSA-ES63,
Revision 0, "Temporary Alignment of Service Water Division I Gland Water Supply to SW
Pumps in Both Divisions," dated August 9, 2004, plus additional information provided in a letter
dated August 9, 2004, and presented during the Regulatory Conference held on September 27,
2004. Using the additional data provided by the licensee, as well as evaluations and input from
the NRC staff, a final significance determination was performed by modifying the preliminary
evaluation, as appropriate. The documentation that follows is not a stand-alone evaluation.
The reader must also be familiar with the preliminary significance determination documented in
NRC Special Inspection Report 05000298/2004014, Section 1R04.b(3), "Analysis."
I.
Internal Events:
The NRC reviewed the testing data and other pertinent information provided by the
licensee. The following characterizes each of the changes made to the assumptions in
the NRCs preliminary significance determination:
a.
The service water pumps at Cooper will fail to run 50 percent of the time if gland
water is lost for 30 minutes or more. If gland water is recovered within
30 minutes of loss, the pumps will continue to run for their mission time, given
their nominal failure rates.
The NRC determined that the test conducted by NPPD on a representative pump
indicated that service water pumps, when run without gland water, would not
always fail as originally assumed. However, uncertainties in the data and
differences identified between the test configuration and the actual plant
indicated that a significant potential remained that a pump would fail if gland
water were lost for greater than 30 minutes. Therefore, a bounding value of
50 percent was used.
b.
Vital battery depletion is best represented as occurring at 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> following a
station blackout rather than at 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> as modeled in the Standardized Plant
Analysis Risk (SPAR) Model for Cooper. This assumption was based on
resident inspector review of the licensees calculation provided following the
c.
The probability of operators failing to properly diagnose the need to restore
Division II service water gland water to the running pump upon a loss of
Division I service water is 0.4. The NRC calculated this value in the preliminary
significance determination. However, the value was applied to both pumps in the
preliminary significance determination. The NRC applied this value only to the
operating pump in the final significance determination because there would have
been additional time to recover gland water for the standby pump.
-2-
1Odds ratio is a method of accounting for the number of successes as well as failures
when calculating a condition human error probability. This method of accounting for
uncertainties associated with individual performance shaping factors is described in draft
NUREG-CR-XXXXX (INEEL/EXT-02-10309), SPAR-H METHOD, and tends to provide a less
conservative result.
d.
The probability of operators failing to properly diagnose the need to restore
Division II service water gland water to the standby pump upon failure of the
running pump is 0.05. This results in a conditional probability of recovering gland
water to the standby pump, given a failure to recover gland water to the running
pump, of 0.125.
For this calculation, the NRC used the same performance shaping factors used
in the case of the running pump with the following exceptions: the available time
was changed from barely adequate to extra time (0.1) because the time to
perform this action was now greater than 60 minutes, and Odds ratio1 was
applied to better quantify the multiple performance shaping factors.
e.
The conditional probability that Division II service water fails to survive upon
demand given that Division I fails is 2.65 x 10-2.
The NRC developed an event tree to better model the failure of the service water
system without gland water available. This model indicated that, upon a failure
of the running pump, the availability and reliability of the standby pump should be
evaluated. Additionally, the degradation of the test pump observed during the
licensees testing was assumed to reduce the capability of the pumps to fulfill
their mission after running without gland water for any period longer than
30 minutes. The event tree also included a small probability that the pumps
would continue to run for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> without any gland seal water as indicated by
the licensees testing. The NRC then quantified this event tree to obtain the
probability.
The NRC used Assumption b to adjust the baseline SPAR model. The resulting
baseline core damage frequency, CDFbase, was 5.05 x 10-9/hr.
The NRC changed the modified SPAR model discussed in the preliminary significance
determination to account for all changes in assumption discussed above. The NRC
changed the recovery action value from the preliminary determination to the conditional
probability that Division II service water fails to survive upon demand given that
Division I fails provided in Assumption e. The modified SPAR model was requantified
with the resulting current case conditional core damage frequency, CDFcase, of 6.26 x
10-9/hr.
The change in core damage frequency (CDF) from the revised models was calculated
as follows:
CDF = CDFcase - CDFbase = 6.26 x 10-9 - 5.05 x 10-9 = 1.21 x 10-9/hr.
-3-
Therefore, the total change in core damage frequency over the exposure time that was
related to this finding was calculated as:
CDF = 1.21 x 10-9/hr * 24 hr/day * 21 days = 6.10 x 10-7 for 21 days
The final risk significance of this finding is presented in the following table. The
dominant cutsets from the internal risk model were essentially the same as provided in
the preliminary significance determination.
Table I
Final Significance Determination
Evaluation Model Results
Model
Result
Core Damage
Frequency
SPAR 3.03, Revised
(and modified for
final determination)
Baseline: Internal Risk
5.1 x 10-9/hr
Internal Events Risk
6.3 x 10-9/hr
TOTAL Internal Risk (CDF)
6.1 x 10-7
TOTAL External Risk (CDF)
2.3 x 10-7
TOTAL Internal and External Change (CDF)
8.4 x 10-7
II.
External Initiators:
The NRC made no changes to the models, techniques, and assumptions used in
evaluating the external initiators contribution to the CDF from those presented in the
preliminary significance determination. However, the NRC used the changes in
assumption to the internal events evaluation and the revised SPAR model to requantify
the core damage frequency related to internal fires. Internal fire was the only external
initiator determined to affect the CDF in the preliminary significance determination.
The revised values are presented in Table II.
-4-
Table II
Final Significance Determination
External Initiators (Internal Fire) Results
Fire Areas:
Fire Type
Switchgear 1F
Shorts Bus
4.65 x 10-10/hr
Service Water Pump Room
One Pump
1.45 x 10-15/hr
Both Pumps
1.04 x 10-14/hr
CDF for All Fires Affecting the Service Water System:
4.65 x 10-10/hr
Exposure Time (21 days):
5.04 x 102 hrs
Total External Events CDF over the Exposure Period:
2.34 x 10-7
III.
Large Early Release Frequency (LERF):
The NRC reevaluated the portions of the preliminary significance determination related
to the change in LERF. In the regulatory conference, the licensee stated that the
dominant sequences were not contributors to the LERF. Therefore, there was no
change in LERF resulting from the subject performance deficiency. The licensee
indicated that the postulated core damage sequence took more time than the average to
progress to core damage. This provided additional time to core damage and the
relatively short time estimated to evacuate the close-in population surrounding Cooper
Nuclear Station.
LERF is defined in NRC Inspection Manual Chapter 0609, Appendix H, "Containment
Integrity Significance Determination Process" as: "the frequency of those accidents
leading to significant, unmitigated release from containment in a time frame prior to the
effective evacuation of the close-in population such that there is a potential for early
health effect." The NRC noted that the dominant core damage sequences documented
in the preliminary significance determination were long sequences that took greater than
12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to proceed to reactor pressure vessel breach. The shortest calculated interval
from the time reactor conditions would have met the requirements for entry into a
general emergency (requiring the evacuation) until the time of postulated containment
rupture was 3.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. The licensee stated that the average evacuation time for Cooper
from the declaration of a General Emergency was 62 minutes.
The NRC determined that, based on a 62-minute average evacuation time, effective
evacuation of the close-in population could be achieved within 3.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. Therefore, the
dominant core damage sequences affected by the subject performance deficiency were
not LERF contributors. As such, the NRCs best estimate determination of the change
in LERF resulting from the performance deficiency was zero.
-5-
IV.
Conclusion:
Based on reanalysis of the preliminary significance determination, the NRC concluded
that the subject inspection finding was of very low safety significance (Green). This
result was based on a more realistic failure probability for the service water system
derived using the results of the licensees testing program, as well as the inherent
capabilities of the system. The total change in CDF, after adjusting for this revised
system failure probability, was estimated to be 8.4 x 10-7. Additionally, the NRC
determined that there was no change in LERF because, during the dominant accident
sequences, effective evacuation of the close-in population could be achieved prior to the
release.