L-2023-099, Pump Relief Request 10 (PR-10), One-Time Request for an Alternative to the American Society of Mechanical Engineers (ASME) Operation and Maintenance (OM) Code for the Auxiliary Feedwater (AFW) 2C Pump
| ML23208A057 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 07/26/2023 |
| From: | Strand D Florida Power & Light Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-2023-099 | |
| Download: ML23208A057 (1) | |
Text
U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington D C 20555-0001 RE:
St. Lucie Nuclear Plant, Unit 2 Docket No. 50-389 Renewed Facility Operating License NPF-16 L-2023-099 10 CFR 55a(z)(2)
July 26, 2023 Pump Relief Request 10 (PR-10), One-Time Request for an Alternative to the American Society of Mechanical Engineers (ASME) Operation and Maintenance (OM) Code for the Auxiliary Feedwater (AFW) 2C Pump Pursuant to 1 O CFR 50.55a(z)(2), Florida Power & Light Company (FPL) hereby requests for St Lucie Nuclear Plant Unit 2 (St Lucie), Nuclear Regulatory Commission (NRC) approval of a proposed alternative to American Society of Mechanical Engineers (ASME) Operation and Maintenance (OM) Code 2004/2006a, Subsection ISTB-6300, Systematic Error. The proposed alternative would provide on a one-time basis, relief from the ASME OM ISTB-6300 requirement to conduct a retest of the Auxiliary Feedwater (AFW) 2C Pump until plant conditions are appropriate to support a comprehensive pump test in accordance with ASME OM ISTB-3400. The requested relief follows the discovery of a test instrument employed during the prior AFW 2C pump comprehensive test that was subsequently determined to be outside the allowable calibration tolerance. Compliance with the ASME OM ISTB-6300 requirement to conduct a retest would necessitate a unit shutdown and thereby constitute a hardship without a compensating increase in safety.
The enclosure to this letter provides FPL's evaluation of the proposed alternative. The requested relief would apply on a one-time basis and would expire upon the next St Lucie Unit 2 entry into MODE 3. The enclosed evaluation demonstrates with reasonable assurance that the AFW 2C pump will operate acceptably in the interim.
FPL requests that the proposed relief request is processed on an expedited basis to support approval by March 24, 2024, which is the date the current surveillance period for the AFW 2C pump would expire.
This letter contains no new regulatory commitments.
Should you have any questions regarding this submission, please contact Mr. Kenneth Mack, Fleet Licensing Manager, at 561-904-3635.
Sincerely, Dianne trand General Manager, Regulatory Affairs Florida Power & Light Company Enclosure cc:
USNRC Regional Administrator, Region II USNRC Project Manager, St. Lucie Nuclear Plant, Units 1 and 2 USNRC Senior Resident Inspector, St. Lucie Nuclear Plant, Units 1 and 2 Mr. Clark Eldredge, Florida Department of Health Florida Power & Light Company 6501 S. Ocean Drive, Jensen Beach, FL 34957
St. Lucie Nuclear Plant, Unit 2 Docket No. 50-389 St. Lucie lnservice Test Program Pump Relief Request 10 (PR-10)
Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2) for the Auxiliary Feedwater (AFW) 2C Pump
- 1.
ASME Code Component(s) Affected:
The following plant equipment is affected:
Component Tag No.
Description Safety Class AFWPP 2C AFW Pump (Steam Driven) 3
- 2.
Applicable Code Edition and Addenda
L-2023-099 Page 1 of 4 Enclosure ISTB Group B
ASME Code for Operation and Maintenance of Nuclear Power Plants 2004 Edition, 2006 Addenda (ASME OM Code 2004/2006a)
St. Lucie Unit 2 is in the fifth 120-month Pump and Valve lnservice Testing interval, which began February 11, 2018, and will expire February 10, 2028.
- 3.
Applicable Code Requirement
ASME OM Code, Subsection ISTB-6300, Systematic Error, states, in part, when a test shows measured parameter values that fall outside the acceptance range... that have resulted from an identified systematic error, such as... inaccurate instrumentation, the test shall be rerun after correcting the error.
- 4.
Reason for Request
The requested relief follows the discovery of a vibrometer employed during the previous AFW 2C pump comprehensive test that was subsequently determined to be outside the allowable calibration tolerance.
The AFW 2C pump comprehensive pump test which utilized the faulty vibrometer was conducted March 16, 2023, during the SL2-27 refueling outage. The test is performed every two-years as required by St.
Lucie Unit 2 Technical Specification (TS} Surveillance Requirement (SR) 4.7.1.2.d and the St. Lucie lnservice Testing (1ST} Program. The comprehensive test frequency aligns with the biennial test frequency requirement specified in ASME OM Code Table ISTB-3400-1, lnservice Test Frequency, for Group B pumps. During the comprehensive test, AFW flow is directed to the steam generators to simulate design basis accident conditions. Amongst other required parameters, pump vibration velocity (inches/second) readings are measured and trended. Consistent with Table ISTB-3400-1, the AFW 2C pump is additionally tested each quarter while aligned to recirculate AFW flow to the condensate storage tank (CST).
The vibrometer is an EMERSON vibration monitor, model CSl2140, which is calibrated to meet the test instrument requirements of ASME OM Code Table-lSTB-3510-1.
In May 2023, the subject vibrometer was determined to be outside the allowable calibration tolerance upon noticing lower than expected vibration (velocity) measurements on a tested pump that had been recently overhauled. The low readings were confirmed to be out of tolerance with a site predictive maintenance vibrometer. Extent of condition identified several other tests with lower than expected readings on pumps that had not undergone corrective maintenance or repair. The issue was documented in the St. Lucie corrective action program (CAP) and the affected pumps were satisfactorily retested except the AFW 2C pump due to plant conditions required. The vibrometer was previously calibrated in August 2022 and was due for recalibration in August 2023. Following the discovery, the vibrometer was sent out for immediate re-calibration. However, the post-calibration results did not yield
St. Lucie Nuclear Plant, Unit 2 Docket No. 50-389 St. Lucie lnservice Test Program Pump Relief Request 10 (PR-10)
L-2023-099 Page 2 of 4 Enclosure sufficient data to ascertain the actual vibration readings from the March 2023 comprehensive test. As a result, FPL could not confirm that the measured values were within the acceptable range for pump vibration and concluded that a retest in accordance with ASME OM ISTB-6300 was required prior to the expiration of the current surveillance period. The prior comprehensive pump test was satisfactorily completed September 26, 2021. Accordingly, the current surveillance period with 25% grace, as allowed by 10 CFR 50.55a(b)(3)(x), will expire March 24, 2024. Compliance with the ASME OM ISTB-6300 requirement to conduct a retest would require a unit shutdown to establish the plant conditions necessary to support the comprehensive test.
- 5.
Proposed Alternative and Basis for Use:
- a.
Basis for Use The proposed alternative would authorize on a one-time basis, relief from the ASME OM ISTB-6300 requirement to conduct a retest of the AFW 2C pump until plant conditions were appropriate to support a comprehensive pump test in accordance with ASME OM ISTB-3400. The authorization would expire upon the next unit entry into MODE 3, which would occur on or before the Fall 2024 scheduled refueling outage.
Performance of the AFW 2C pump comprehensive test cannot be conducted with the unit online due to the plant conditions required to perform the test. This test can only be performed in Mode 3 with Steam Generator level greater than 40%. The Steam Generator level limitation is necessary to prevent water hammer that could potentially damage the feed ring support.
- b.
Historical performance The first comprehensive test for the AFW 2C pump was performed in 2009 following the fourth 1ST program update to the ASME OM 2001-03 Code in 2008. The currently used reference value for the AFW 2C pump comprehensive test was developed in 2011. Since then, all comprehensive tests have been performed satisfactorily, with no ASME OM Code 'Alert' or 'Action' level limit exceedances. In particular, the vibration readings have been stable with no adverse trends.
The current AFW 2C pump quarterly code run (on recirculation) reference values were developed in 2000 to revise the action limits to include instrument uncertainty. With the program update in 2008, the group classification for the AFW 2C pump was changed and vibration data was no longer required during the quarterly code run. Since 2000, all quarterly recirculation tests have been performed satisfactorily, with no ASME OM Code 'Alert' or 'Action' level limit exceedances.
The table below was recreated from the AFW 2C pump quarterly test database maintained by plant operators. The SL2-26 comprehensive test data of 9/26/21 had been inadvertently added whereas the SL2-27 comprehensive test of 3/16/23 is appropriately not listed. The 3/14/23 test indicates pump vibration measurements were taken, though not required, using the faulty vibrometer during an unrelated post-maintenance test following AFW 2C pump governor valve maintenance.
AUXILIARY FEEDWATER 2C PUMP QUARTERLY (RECIRCULATION) TEST HISTORY TEST INLET DISCH.
HEAD IPV IPH OPV OPH PRESS PRESS REMARKS DATE (PSIG)
(PSIG)
(FT)
(IN/S)
(IN/S)
(IN/S)
(IN/S) 6/15/23 17 1350 3075.23 5/22/23 16.8 1350 3075.7 Code Run for Bad Vibrometer 0.166 0.1665 0.1273 0.1215 OPA (IN/S) 0.0806
St. Lucie Nuclear Plant, Unit 2 Docket No. 50-389 5/11/23 17 1350 3/14/23 15 1340 2/9/23 17.4 1350 11/17/22 17 1350 8/4/22 17.2 1350 5/5/22 16.8 1340 2/3/22 16.8 1350 11/4/21 17 1340 9/26/21 17 1245 8/5/21 17 1340 St. Lucie lnservice Test Program Pump Relief Request 10 (PR-10) 3075.2 Quarterly Code Run (QCR) SAT 3056.8 QCRSAT 3074.3 QCRSAT 3075.2 QCRSAT 3074.8 QCRSAT 3052.6 QCRSAT 3075.7 QCRSAT 3052.16 QCRSAT 2832 SL2-26 Full Flow Test 3052 QCRSAT 0.0223 0.0173 0.1042 0.0975 L-2023-099 Page 3 of 4 Enclosure 0.0192 0.0222 0.0776 0.0716 0.0255 0.0858
- IPV = Inboard Pump Vertical; IPH = Inboard Pump Horizontal; OPV = Outboard Pump Vertical; OPH = Outboard Pump Horizontal OPA = Outboard Pump Axial During the AFW 2C pump comprehensive test which utilized the faulty vibrometer, all other pump performance measurements yielded satisfactory results. Following the identification of the lower-than-expected vibration readings for the AFW 2C pump, a quarterly test was performed on 5/22/23 to confirm acceptable pump vibration. Since pump vibration was taken while in recirculation, the measurements would be expected to be elevated as compared to the comprehensive test vibration readings. Even with the elevated vibration, the measured pump vibrations were below the 'Alert' level established for the comprehensive test (see below), indicating acceptable pump performance and thereby, a satisfactory comprehensive test on 3/16/23 if not for the faulty vibrometer.
Pump Vibration Inboard Inboard Outboard Outboard Outboard Measurement Pump Pump Pump Pump Pump Location Vertical Horizontal Vertical Horizontal Axial (IPV)
(IPH)
(OPV)
(OPH)
(OPA)
Comprehensive Test 0.325 in/sec.
0.325 0.2627 0.2355 0.216 Alert Level*
5/22/23 0.166 0.1665 0.1273 0.1215 0.0806 Test Results
- 2-OSP-09.02C, 2C Auxiliary Feedwater Pump Refueling Shutdown Pump and Valve Test
- c.
Performance Monitoring During the proposed period of relief from the retest requirements of ASME OM ISTB-6300, AFW 2C pump performance will continue to be monitored and trended by quarterly recirculation testing in accordance with ASME OM Code Table ISTB-3400-1. Current trending of the quarterly recirculation and biennial comprehensive inservice testing has not identified adverse trends in pump performance. Accordingly, there is reasonable assurance that the AFW 2C pump will perform consistent with safety analysis assumptions during the proposed period of relief.
In addition, the St. Lucie predictive maintenance (PDM) program performs qualitative analysis of the AFW 2C pump overall health each refueling cycle through vibration measurements and oil sampling. The latest PDM report from March 16, 2023, concludes that the pump and steam turbine are both "green" with acceptable vibration patterns, levels, and trends. Though the vibration values were within the ASME OM Code action limits, they are not credited for inservice testing since the equipment is not calibrated to ASME OM Code requirements and the measurements are taken at the true vertical and horizontal axis, which are different points than those used for inservice testing. However, the PDM data reveals stable trends overall.
St. Lucie Nuclear Plant, Unit 2 Docket No. 50-389 St. Lucie lnservice Test Program Pump Relief Request 1 O (PR-10)
L-2023-099 Page 4 of 4 Enclosure In addition, a work order to perform the comprehensive test for the AFW 2C pump has been added to the forced outage schedule in the event entry into MODE 3 occurs before the next refueling outage in September 2024.
- d.
Conclusion The proposed alternative wou Id delay retest of the AFW 2C pump comprehensive test until the next MODE 3 entry when plant conditions are appropriate. Historical testing during recirculation and comprehensive flow conditions have not demonstrated signs of pump degradation. Quarterly testing under recirculation conditions and PDM analysis are an effective means of monitoring pump health in the interim. The proposed alternative to the retest requirement of ISTB-6300 will continue to assure AFW 2C pump operational readiness without compromising public health and safety.
- 6.
Duration of Proposed Alternative:
The proposed alternative would be applicable for the St. Lucie Fifth 10-Year 1ST Interval.
The authorization would be restricted to the AFW 2C pump on a one-time basis and would expire upon the next Unit 2 entry into MODE 3.
- 7.
Precedent:
No precedent was identified for the proposed alternative to ASME OM ISTB-6300.