ML19353B045
| ML19353B045 | |
| Person / Time | |
|---|---|
| Site: | Mcguire |
| Issue date: | 11/27/1989 |
| From: | Tucker H DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8912110101 | |
| Download: ML19353B045 (11) | |
Text
{{#Wiki_filter:'ll-I Duke Iburt Comj>a. 7 Hu is hw I'O &a 331M ikr/>vudent Charlotte. N C 2Cl2 Kuclear l'roductson (TN)373 4L11 { DUKE POWER November 27, 1989 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 i
Subject:
McGuire Nuclear Station, Unit 2 ( Docket No. 50-370 Diesel Generator Special Report Gentlement Pursuant to Technical Specification (T.S.) 6.9.2 as specified by T.S. 4.8.1.1.3, find attached a special report concerning a Valid Failure on Diesel Generator 2B, and supplemental information resulting from the seventh Valid Failure in the last 100 Valid Tests for Diesel Generators 2A and 2B, combined. If you have any questions, please contact S.E. LeRoy at (704) 373-6223. Very truly youts, 5 /nek,/g llal B. Tucker SEL/486 Attachment xc: Mr. S.D. Ebneter, Administrator Mr. P.K. Van Doorn, NRC U.S. Nucicar Regulatory Commission Senior Resident Inspector Region II McGuire Nuclear Station 101 Marietta St., NW, Suite 2900 Atlanta, Georgia 30323 Mr. D.S. Ilood, Project Manager Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 l-INPO Records Center Suite 1500 l 1100 circle 75 Ptrkway Atlanta, Georgia 30339 8912110101 891127 f I1 ) PDR ADOCK 05000370 3 PNV e i
U.S. Nuciccr R:gultt:ry Commicsion Document Control Desk November 27, 1989 Attachment No. 1 Duke Power Company McGuire Nuclear Station Diesel Generator 2B Special Report On October 27, 1989 at 0853, a Valid Failure (start attempt no. 759) occurred on Diesel Generator (DG) 2B. The start attempt was made to perform the DG operability surveillance test (PT/2/A/4350/02B). The engine failed to roll on starting air indicating a failure to energize the starting air solenoid valves (2VG65, 66, 67 and 68). Work request no. 139953 was initiated to investigate the start failure. Troubleshooting revealed the 50% contacts on speed switch S1A2 had failed which prevented the energizing of relay RVG1 which picks up the starting air solenoid valves. Temporary Modification no. 5986 was issued to remove the SIA2 speed switch 50% functions from the circuit. -The DG can-functionally perform with only one speed switch (S1A1) performing the 50% functions. Start attempt no. 760 was made at 1648 to verify the DG would function properly after installation of the temporary modification. The operability surveillance test (PT/2/A/4350/02B) was run satisfactorily and the DG was subsequently declared operable. Prior to this failure, actions were taken to'procurt a new type of speed switch because the manufacturer no longer supported the model currently installed. The new' speed switch has been identified and ordered. When the new switch is ;eceived the temporary modification will be cleared via a permanent modification to install the new speed' switch. The new switches will be instilled on all four DGs as soon as practical. This was the 6th Valid Failure in the last 20 Valid Tests and the 7th Valid-Failure in'the last 100 Valid Teste for DG 2B, This is also the 7th Valid Failure in the last 100 Valid Tesw. of DG 2A and 2B combined. (see for additional information required for the combined 7th Valid Failure). Surveillance test frequency remains weekly. t i f
t 7 E U S. Nuc10er R:gulctory Commiccion Document Control Desk November 27, 1989 i I Attachment No. 2 Duke power Company r McGuire Nuclear Station. Unit 2 Diesel Generator Supplemental Report McGuire Technical Specification 4.8.1.1.3 requires that additional L information be provided (par USNRC Regulatory Guide 1.108 Revision 1 section C.3.b) if the number of failures in the last 100 valid tests (on a j per nuclear unit basis) is greater than or equal to 7. On October 27, 1989 a valid failure occurred on DG 2B. This failure was the 7th valid failure in the last 100 valid tests for the Unit 2 DGs. Reliability Improvement Measures The following are descriptions and basis for corrective measures, taken or planned, to increase the reliability of the DGs On October 27, 1989 DG 2B failed to start due to a failure of the 50%- contact on speed switch S1A2. A modification will be performed on all McGuire DGs to install a new type. speed switch. The switches have been identified and are on order. The now switches should improve control system reliability. On October 5, 1989 DG 2B failed to start. The apparent failure was solenoid valve 2VGSV5172 not opening (though the failure mode discovered was a failure to close). 1. The valve was replaced. Although the failure made would not repeat on the test bench, no further problems of this nature have been noted. 2. The control air line filter and solenoid valve were checked for' foreign metal shavings such as the one found in the failed solenoid and no problem was found. This is considered to be a random failure. On September 29, 1989 DG 2B failed to start due to either burned contacts on relay RVG1 or the 50% contact on a speed switch as discussed above. The root cause was originally thougnt to bn the burned contacts but af ter discovery of the speed switch failure (October 27. 1989) a case can be made for that having also caused this failure. 1. Relay RVG1 was replaced. Work requests were written to replace this relay on the other DGs also. -
r 'U.S. Nuc1 = r R gulctory Commic: ion November 27, 1989 t 2. A station problem report (SPR-2403) was initiated as a result of a self initiated technical audit (SITA) to change the circuit design for RVG1 such that four solenoids are not energized through the same set of contacts. This change will be made as part of the station modification process as soon as practical. On August 29, 1989 DG 2B failed because the start time for voltage buildup to 4160V was 11.024 seconds versos the Technical Specification requirement of 11 seconds. The root cause of this problem was a damaged speed sensor. 1. The mechanical periodic tests will be changed to remove the speed sensor prior to outage maintenance work and replace it before running the engine after completion of the work. 2. An order for new sensors was expedited. All 4 DGs' sensors will i be inspected and the gap between the camshaft gear teeth and the sensor will be increased to 0.030 inch. 3. The speed sensors will be checked for damage overy 9 months. On July 27, 1989 DG 2B failed during a 24 hour surveillance test (after 14 hours) when 2 fuses in the voltage regulator feedback control circuit blew causing generator VARS to peg high. Operations personnel manually tripped the DG breaker. The root cause of the blown fuses is not certain but a contributing cause was high room ambient temperature causec' by the f ailure of a room ventilation recirculation damper. 1. A temporary modification was initiated to lock the recirculation damper d osed. The damper was later repaired and the temporary modification was c1 cared. 2. A control transformer and a circuit card in the voltage regulator were replaced as a preventative measure due to the high ambient temperature. i On July 26, 1989 DG 2B had a start failure because the Technical Specification time limit on attaining 4160V (11 seconds) was exceeded (11.070 seconds). The cause'of the failure could not be determined at the time-of failure but has since been determined to be the damaged speed sensor that also caused the failure on August 29, 1989 (discussed previously). m This failure was originally classified as an invalid test but has been . changed to_a valid failure upon further study. The speed sensor was likely -damaged by maintenance activities during the outage; however, the damage scenario could not be agreed upon so this test is conservatively considered a valid failure, On December 15, 1988 DG 2B failed due to a low lube oil pressure trip. Results of the investigation were not conclusive but it is thought that air in the instrument line resulted in the trip. hL i~.- p U.S. Nuc1= r R gulatosy Commiccion November 27, 1989 1. Tubing was blown out with station air. 2. The lube oil pressure trip switch was recalibrated. As a result of the numerous control related failures experienced since the Unit 2 outage (EOC 5), a team has been formed to review areas that could provide reliability improvements on the DGs.. Maintenance Engineering Services has assigned a lead individual to work on DG elect rical/ control / instrumentation problems full time for 6 months. lie will work with the DG System Engineer to develop action items for improving short and long term reliability. Assistance also will be provided by 1AE technicians who have DG cxperience, an Operations Engineer, Hechanical Engineering. Performance and Projects personnel on an as needed basis. Some of the areas to be reviewed are as follows: 1. Pending station modifications. 2. The recently completed DG Reliability Centered Maintenance Study. 3. PMs/ pts / Maintenance procedures. 4. Instrumentation adequacy. 5. A new engine monitoring system currently being installed. 6. Vendor training needs. An engine monitoring system is being installed on Unit 2 now and Unit I during the next outage. This system will add many new data points relating to engine performance.. When in full operation it will provide much needed data to help monitor degraded operation and to help troubleshoot more accurately with fewer engine starts, in addition to the monitoring system, work is also pregressing on an EPRI sponsored project to add artificial a intelligence to the DG data collection and evaluation. Engins Reliability Assessment Considering the 7 valid failures in the last 100 valid tests, DG 2A had 0 , failures in 37 tests and DG 2B had 7 failures in 63 tests. Two approaches can be used to estimate the reliability. One approach treats each DG as having a separate failure ratn. The failure rate for each engine is calculated and the two rates are then multiplied and suctracted from unity to give a system r611 ability. The second method treats both DGs as having an average failure rate of 7 out of 100 tests (thus each is 93% reliable). The estimated failure rate at a 50% nonfidence level (established by NUREG 75/87 Appendix 7-A) is derivot
- t. sing statistical i
methods assuming a chi-squared distribution. ; l' .t
n~>~K ( U.S. Nucltct Regulct:ry Commission November 27.-1989 ' Using the first method, DG 2A has a known failure rate of 0 which would imply a reliability of 100%. DG 2B has a known failure rate of 0.1111 which corresponds to a reliability of 88.9% (this is very close to the_ average estimated reliability calculated at the 50% confidence level, 88.3%). The system reliability is thus 100%. + Using the second method, the sjatem reliability is between 99.1% and 99.7% at a 50% confidence level. F Both methods exceed the 99% goal at a 50% confidence level established by NUREG 75/87 Appendix 7-A. L Basis For Continued Operation i The unit will continue to be operated because reliability of the emergency DG power source exceeds that proposed in the NUREG and a comprehensive-reliability improvement program is in place. Summary Of Tests A[ The McGuire Technical Specifications currently require that the DG operability test'(PT/2/A/4350/02) be performed once every 31 days if four i valid failures (VF) or less have_ occurred in the last 100 valid attempts, i and if one VF or less has occurred in the last.20 valid attempts. ? Otherwise,_the testing will be performed weekly. The following is'a summary' of the 2A and 2B start attempts.- f VF = valid failure VS = valid success IT = invalid test l IF = invalid failure i Valid Engine 2A Engine 2B Attempt 2A _ Test 2B Test Number Start Result Date Start Result 100
- 10-27-89 759 VF (S1A2 speed f
99 10-19-89 758 VS switch) 98 10-12-89 757 VS 97 10-07-89 756 VS 755 IT i 754 IT 753 IT 752 IT 96
- 10-05-89 751 VF (2VGSV5172) 95 752 VS 10-03-89 94 751 VS 09-29-89 09-29-89 750 IT 93 09-28-89 749 VS L
Y f we v v v
T =5 7.- ,4 i g 7 w, .e' U.S. Nuclear Reg'ul;ttry Conniccion ~ November 27, 1989 i Valid' Engine 2A Engine 2B l -Attempt- .2A Test 2B-Test l Number' , Start. Result Date Start Result: t -92 748-VS 91
- 747 VF (SIA2 or RVG1)-
j 90 09-22-89 746 VS 89'- 750 VS 88 749 .VS 09-21-89 748 IT. 09-15-89 87 09-14-89 745 VS 'i 86-09-07 744- .VS- -l 85 09-05-89 ~743 -VS 'j- '742 IT 741 IT 747 IT '09-04-89 ,j 746 'IT 09-01-89 84 745 VS 08-31-89 i 83 740 VS 08-30-89 739 IT l 738 IT 737= IT- -i 736" IT 735 IT [ 734 IT 733'- IT l 08-29-89 732 IT i 731 IT -82 *' 08-29-89 730 .VF (speed sensor) 1 81' 729 VS J 08-24-89 728 -IT 727 IT 80~ 744 VS 743 'IT 742 IT p 741: IT 23-89 740 IT 739 IT. b 738' IT 08-22-89 l I F' '737-IT f 736 IT 735 IT 08-21-89 ..F 734 IT ] N 733 IT 732-IT { b 731 IT f 730 IT L-729 IT 4 728 IT- -l n I s i i. g a, i L."
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U* Q (U.S. Nuc16 rI.Resultt:ry Comunicsion November 27,'1989.: 4 r q Valid . Engine 2A Engine.2B i Attempt 2A Test 2B Test j Number. Start Result Date' Start-Result 79- '727. VS-08-19-89 726 IF 08-18-89 .[ a 725' -IT r
- .724" IT i
b: 723. .IT s 722 IT: l L
- 721; IT' 08-17-89
'i f.~ 720 IT I '719 IT F 78 !718L VS
- 08-16-89 b
77 717 VS ? L-
- 76
-716- -VS -j L. '715 .IT 08-15-89 I, 75 .714-VS E 74: 713 VS' [ 712-IT ?
- r. -
711-IT. Ii ' 710 IT i I 709 -IT l [i -708 IF- +l ~1F 707 IF '- 08-14-89 706 ~705' IF/ s 07-31-89 '726 1 IT j g i: C 07-30-89 725 VS- 'l 73 724' IT,
- (
722 1T-j V. ~ 723-3 IT l L 4 : y-721 IT i 07-30-89~ 720 IT a L 719 .IF -{ [ 72 07-29-89 ' 718 VS p 717-IT-
- i.
f - 716 IT E. 715 IT "~ B_ 714 IT-1F 71;*L 07 27 713 VF.(Volt Reg fuses) h 70 *' 04 26-89 712 VF (speed sensor) '69 07-25-89 711 VS = 710' VS Y3-68 l. 709 IT -) 708 IT 707 IT II... 706 IT b h 705 IT r -J b 1 l
y: w. n t U!S. Nuclear'Reguldt ry Commicsion: [f .. November-27, 1989 g o Valid Engine 2A Engine 2B' Attempt. 2A Test. 2B Test Number. Start' Result. 'Date Start , Result ~ 67 704 VS 07-15-89 07-09-89 704~ IT '66 07-03-89 703-VS-65-703 VS' 06-21-89 64 702 'VS' .06-20-89 L 701 IT-f. 63 06-06-89 702 VS -62 700 YS 05-19-89 [K - >60- ~04-27-89 700 VS - 61 05-11-89 701 VS T'"' 59 699 VS 04-24-89 F 58 20-89 699 VS 57 - 04-13-89 698 VS F 56 04-06-89 097 VS 04-02-89 696 IT E 55 '03-30-89 695 VS 54-648 VS 03-29-89; H 697 IF-03-28-89 '696 IT~ 53 23-89 694 VS p 03-16-89; 693 VS i 52
- U 51 03-09-89
~692 VS '695 IT 03-03-89 694 IT- "~ 693 IT
- 697, IT 50 03-02-89 691 VS
- 49 691
.VS 02-24-89 48 02-23-89 690 VS 47: 02-17-89' 689 VS 688 IT 687 IT 686 IT ~46' 02-09-89 685 VS 45 02-02-89 684 VS ~44-690 VS 01-30-89 l 43 01-26-89 683 VS 42 01-19-89 682 VS'- 41-01-12-89 681 VS 40 01-05-89 680 VS 39 689 VS 01-04-89 l 38f 12-29-88 679 VS 37 12-22-88 678 VS ~ 12-21-88 677 IT i _.
!.4 9
- U.S. Nuclear R:gulttery Comunic?. ion' November 27, 1989 l
Valid ~ Engine 2A Engine 2B Attempt 2A Test 2B Test f Number Start Result-Date Start , Result 12-15-88 676 IT 675 IT L 674 IT 36 '- 673 VS ? .35
- 672 VF (air in lube oil) f 34 688 VS 33 12-07-88 671 VS i
32' 687 VS 12-06-88 l 31 12-02-88 670 VS = 30-11-25-88 669 VS 29 11-17-88 668-VS l V 28 '11-10-88 667 VS i 27 686 VS 11-04-88' 'i 685 IT l '26 11-03-88 666 VS L 25 10-27-88 665 VS L 10-20-88 664 IT 24' 663 VS L-23 684-VS 22. 683 VS 10-18-88 .21. 10-13-83 662 VS -t 682~ VS 10-11-88 -19 10-06-88 661 VS 18~ 681 VF 10-05-88 '17 09-29-88 660: VS j 16 680 VS 09-27-88 15 09-22-88 659 VS t b 14 679-VS 09-21, 13 678 VS 09-16-88 12. 09-15-88 658 VS 657 IT a 11' ~677 VS 09-13-88 ~! 10 -- 09-08-88 656 VS
- l 9
676 VS 09-06-88 8 09-01-88 655 VS 7-675-VS 08-30-88 i 6 -674 VS 08-23-88 '5-654 VS p '4. 08-18-88 653 VS 3 673-VS 08-16-88 j 2'- 08-11-88 652 VS j 1_ 672-VS 08-09-88 t f -o -1
,'-(_ g. p. + v e, a ' U.S. Nuclear Reguic.t. cry Commie: ion J y November 27. 1989-j r Y g [ The totals are as follows:: t t. f DG 2A~ DG 2B - t fG .n : 37 Valid Successes-56 Valid Successes [ t, .0 Valid Failures 7 Valid Failures 38' Invalid Tests 44 Invalid Tests i f4 6: Invalid Failures 1 Invalid Failure l l t p i.. i b { 1. L. r i, f.i 5 + s r p, l 1 - r i i
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