ML20203B095
| ML20203B095 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 02/18/1998 |
| From: | Mccoy C SOUTHERN NUCLEAR OPERATING CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 50-424-96-11, 50-425-96-11, LCV-0910-F, LCV-910-F, NUDOCS 9802240205 | |
| Download: ML20203B095 (7) | |
Text
'
C. K. McCoy So thern Nuclear Vice ":esident
- Op: rating Cxpery.Inc.
Vogtle Project 40 inverness Center Perkway P.O Box 1295 Birmingham Alabama 35201 Tel 2059923122 fox 2059920403 Fet;ruary 18, 1998 SOUTHERN COMPANY Docket No.
50-424,425 y,,,y,,5,,,, nu, s,1g -
U. S. Nuclear Regulatory Commission LCV-0910-F 4
ATTN: Document Control Desk Washington, D. C. 20555 Ladies and Gentlemen:
VOGTLE ELECTRIC GENERATING PLANT ADDITIONAL INFORMATION RELEVANT TO REELY TO A NOTICE OF VIOLATION On January 30,1997, by letter number LCV-0910-C, Southern Nuclear Operating Company (SNC) submitted a response for Vogtle Electric Generating Plant (VEGP) to violations first identified in Nuclear Regulatory Commir an (NRC) Integrated Inspection Report Nos. 50-424; 425/96-11, which covered an inspection conducted from September 29,1996, through N_ovember 9,1996, at.d discussed at an Enforcement Conference (EA 4
96-479) on December 19,1996. The Notice of Violation was issued as an enclosure to the NRC's letter of December 31,1996, su.nmarizing the proceedings of the meeting and later referenced in NRC Integrated Inspection Reports 50-424,425/96-12, dated January 17,1997. As requested by the NRC, the original response to the NOV stated that an engineering evaluation would be conducted to identify an appropriate method of performance testing safety related pump motor coolerr This revised response is being submitted to the NRC to describe changes to the performance testing methodology for certain safety-related pump motor coolers as addressed in the original response. In this enclosure, a transcription of only one of the two original violations and SNC's response is shown with applicable revision marks indicating changes. The other violation response contained in the original reply to the NOV is unchanged.
t Should you have any auestions feel free to contact this office.
1 j
Sincerel,
i hvuN C. K. McCoy xc and enclosure: (continued next page)
CKM/CTT/afs 9802240205 900218 PDM ADOCK 05000424' G
PDR.
U. S. Nuclear Regulatory Commission Page 2 of 2 LCV-0910-F
Enclosure:
Additional Information Relevant to Reply to NOV (50-424 / 96-479-01013)
\\
xc: Southern NuslegSperating Company Mr. J. B. Beasicy, Jr.
Mr. M. Sheibani NORMS U. S. Nuclear Regulatory Commission Mr. L. A. Reyes, Regional Administrator Mr. D.11. JafTe, Senior Project Manager, NRR Mr. John Zeiler, Senior Resident Inspector, Vogtle o
ENCLOSURE VOGTLE ELECTRIC GENERATING PLANT-UNITS 1 & 2 ADDITIONAL INFORMATION RELEVANT TO REPLY TO NOTICE OF VIOLATION NRC INSPECTION REPORTS 50-424.425 / 96-11 VIOLATION "A" (50-424/96-479-01013)
The following is a transcription of violation "A" as cited in the Notice of Violation (NOV):
"During an NRC inspection conducted on September 29 through November 9,1996, [a]
violation of NRC requirements [was] identified. In accordance with the ' General Statement of Policy and Procedures for NRC Enforcement Actions,' (NUREG-1600),
[a] siolation [is] listed below:
A.
Technical Specification (TS) 3.5.2 Limiting Condition for Operation, Emergency Core Cooling System (ECCS) Subsystems - Tm Greater than or Equal to 350 *F, requires that two independent ECCS subsystems be opercble when in modes 1, 2, or 3. Each subsystem is comprised of one operable centrifugal charging pump, one operable safety injection pump, one operable residual heat removal heat exchanger, and one operable residual heat removal pump.
TS 3.5.2 Action Statement (a) requires that with one ECCS subsystem inoperable that the :aoperable subsystem be restored to operable status Wda 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in Hot Standby within the next six hours and in slot shutdown within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
Contrary to the above, from at least Rptember 30,1991, through October 23, 1996, when Unit I was operated in modes 1,2, and 3, the licensee failed to maintain two independent ECCS subsystems operable, and the provisions of TS 3.5.2 Action Statement (a) ware not met. Specifically, the Unit 1, Train B safety injection pump (IB SIP) was inoperable due to blocked cooling flow to one of its motor coolers and approximately one-third flow to its other motor cooler.
(01013)
This is a Severity Level III problem (Supplement I)."
RESPONSE TO VIOLATION "A"(50-424/96-479-01013)
Admission or Denial of the Violation:
This violation occurred as stated in the notice of violation.
I
ENCLOSURE
{
VOGTLE ELECTRIC GENERATING PLANT-UNITS 1 & 2 l
ADDITIONAL INFORMATION RELEVANT TO REPLY TO NOTICE OF VIOLATION NRC INSPECTION REPORTS 50-424.425 / 96-11 Reason for the Violation:
On October 15,1996, a plant equipment operator noticed that the return line from one of the two Unit I safety injection pump (SIP) B motor coolers was warmer than the other. Since thi coolers are supplied by a common header personnel were unable to explain the different temperatures and a work order was written to investigate. On October 22,1996, one of the two Unit SIP B motor coolers was disassembled and personnel found its tubesheet was blanked off with gasket material.
During disassembly / reassembly, personnel noted the possibility of reversing the plenum and determined that a plan was warranted for checkmg other motor coolers. A field verification of temperature differentials was initiated and on October 25,1996, personnel inspected the other Unit SIP B motor cooler to ensure ; roper plenum installation and found this cooler had a reversed plenum. The effect of this configuration was that cooling v
+ flow made only one pass through this Unit 1 SIP B motor cooler rather than the Ngn vithree passes through the cooler.
The cause of this siolation was improper gasket installation and inadequate procedural guidance resulting incorrect assembly of the motor coolers. A review of work orders determined that the as-found motor cooler assemblies' configurations had been in place at seast since 1991, and possibly since original construction. Therefore, the inoperability of the IB SIP in conjunction with the out-of-service time due to normal maintenance / testing for the 1 A SIP resulted in a failure to maintain two independent ECCS subsystems operable.
While SIP B was incapable # performing its intended safety function, the incidence of SIP A unavailability during unit operation in Modes 1,2, or 3, was found to average approximately 2 and 1/2 hours per year. This condition was addressed by performing an evaluation of the VEGP probabilistic safety assessment (PS A) model which assumed an unavailability of 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> per year. This evaluation determined that the impact on the annual VEGP core damage frequency (CDF) due to the inadvertent unavailability of SIP B for an entire year, would be an increase of about 5.3 percent. Also from a review of the PS A model, it was concluded that this condition does not significantly amplify the impact on CDF resulting from any concurrent normal equipment mainteaance, such as charging pumps, RHR pumps, or SIP A. It was also determined that this condition caused the calculated annual VEGP large early release frequency (LERF) to increase by approximately 48 percent. The accident sequences causing this increase are related to the likelihood of core damage following a steam generator tube rupture event. From the current evaluation, as a percentage of CDF, the contribution of this LERF would only increase to 5.2 percent, which amounts to a negligible impact on the overall VEGP containment performance capability.
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ENCLOSURE l
VOGTLE ELECTRIC GENERATING PLANT-UNITS 1 & 2 ADDITIONAL INFORMATION RELEVANT TO REPLY TO NOTICE OF VIOLATION NRC INSPECTION REPORTS 50-424.425 / 96-11 The above risk assessment was performed assuming that at least one SI pump (in conjunction with a centrifugal charging pump and a residual heat removal pump) was required to mitigate the spectrum of LOCAs to prevent core damage. However, Westinghouse, VEGP's nuclear steam supply system vendor, was asked to reevaluate the small break loss-of coolant accident (SB LOCA) for the impact of the loss of an SI pump. The SB LOCA analysis was determined to be limiting with respect t., the loss of the SI pumps. The existing VEGP SB LOCA analysis of record (AOR) was performed with the 1985 Westinghouse SB LOCA Accident Evaluation Model using the NOTRUMP code.
Since that time a new methodology has been approved by the NRC for use which features improvements that lead to increased ECCS flow to the reactor coolant system (RCS) as well as enhanced depressurization in the RCS. Westinghouse used this 2
methodology in their evaluation of this event for VEGP. Specifically, a generic Westinghouse pressurized water reactor input deck was used with VEGP specific centrifugal charging pump and SIP flows. First an evaluation was performed to demonstrate that the generic model with VEGP specific flows was sufliciently close to the VEGP SB LOCA AOR for comparison purposes. Having successfully demonstrated a valid comparison, a range of postulated break sizes of 1.5",2.0", and 3.0" was evaluated to confirm the limiting break size. The limiting single failure ofloss of a complete train of ECCS was assumed, and the remaining operating SIP was assumed to fail after one hour. The one-hour time frame was based on a conservative engineering evaluation of the impact ofloss of motor cooling on the SIP motor. It was determined that the SIP motor could be conservatively expected to operate for at least one hour.
The results of the evaluation demonstrated a limiting peak clad temperature 1936 'F, which demonstrates that adequate margin to the 10 CFR 50.46 limits remain.
Finally, there was no event during the period from 1991, until the IB SIP was returned to operable status that would have required safety injection.
Corrective Steps Which Have Been Taken and the Results Achieved:
1.
The gasket that blanked ofTthe Unit 1 SIP B motor cooler t ' esheet was o
. removed and a properly cut gasket was installed. Also, the plenum was correctly aligned.
2.
Upon discovery, a field verification of temperature differentials of other similar safety-related motor coolers was performed with one reversed plenum detected on the Unit 2 containment spray pump (CSP) Train A motor cooler. The plenum installatior, was corrected. Subsequent additional inspections have confirmed 3
ENCLOSURE l
VOGTLE ELECTRIC GENERATING PLANT-UNITS 1 & 2 ADDITIONAL INFORMATION RELEVANT TO REPLY TO NOTICE OF VIOLATION NRC TNSPECTION REPORTS 50-424.425 / 96-11 correct plenum orientations, and the plenums were permanently marked accordingly.
3.
The inspection scope was expanded to non safety related pumps and reversed plenums weie found on one of the two non-safety related auxiliary component cooling water (ACCW) system pumps on each unit. These were subsequently corrected.
4.
An evaluation of the impact to the qualified life of the Unit 1 SIP B motor was performed and concluded there was only an insignificant reduction in the motor's qualified life.
Corrective Steps Which Will Be Taken to Avoid Further Violations:
1.
To address functional testing following motor cooler reassembly, maintenance procedure 27118-C, " Westinghouse Large Frame Motor Heat Exchanger Maintenance" and engineering support procedure 83308-C," Flow Testing of Salety-Related NSCW System Coolers", was revised to include the functional l
testing criteria and instructions on performing the test. Listed are the methods which will be utilized:
Utilizing Polysonics, flow will be verified through each motor cooler by a,
one of two methods: 1) measure each individual motor cooler flow, or 2) when it is not possible to measure each individual motor cooler flow, measure the combined flow for both associated motor coolers and measure flow through at least one individual motor cooler in order to calculate the other. This test will ensure that the coolers have been vented properly and that normal flow exists to each cooler, b.
An independent verification of proper plenum orientation via the " match-marks" after cooler reassembly will be performed.
2.
An engineering evaluation was conducted in order to identify an appropriate method for performance testing of safety-related pump motor coolers.
The test method implemented for the Component Cooling Water pump (CCW),
Centrifugal Charging Pump (CCP) and Residual Heat Removal (RHR) pump motors involved calculating an expected motor stator temperature. A similar testing methodology for the Containment Spray (CS) and Safety Injection (SI) pump motor coolers was not feasible considering the insuflicient run time to achieve steady state conditions due to the limited run times allowed for these 4
ENCLOSURE VOGTLE ELECTRIC GENERATING PLANT-UNITS 1 & 2 ADDITIONAL INFORMATION RELEVANT TO REPLY TO NOTICE OF VIOLATION NRC INSPECTION REPORTS 50-424.425 / 96-11 pumps. The method determined to be most appropriate for these pumps was to track motor heatup curves to identify degradation from an established baseline. A procedure was developed and approved May 31,1997, incorporating the above.
test methods.-
The test method for the RHR, CCP, and CCW motor coolers was revised following Engineering review of IR7 baseline data. Currently the test method incorporates thermal modeling results for these exchangers and more accurately measures the cooler performance. Since thermal performance testing cannot be accomplished for the CS and Si pump motor coolers, heatup rate data collected during limited pump runs will ba monitored and trended.
All Unit 1 baseline testing for the pump motor coolers was completed by the end of the IR7 refueling outage and the results evalt [ :d to be acceptable. The Unit 2 motor cooler baseline testing will be completed by the end of the 2R6 refueling outage. Based on the results of the baseline testing, testing frequencies will be established.
The testing of the pump motor coolers is aimed primarily at identifying gross malfunctions on the NSCW side of the motor coolers, such as internal bypass or blockage of NSCW flow due to incorrect assembly of the heat exchanger. Based on future test results and trends, the test acceptance criteria for the pump motor coolers may be adjusted accordingly. Additionally, the test acceptance criteria and associated test conditions do not constitute design bases information and would not generally be used as stand alone information to make operability determinations.
3 Date When Full Comoliance Will Be Achieved:
Full compliance was achieved on October 23,1996, when the IB SIP was returned to operable status.
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