ML20059E527
| ML20059E527 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/19/1993 |
| From: | AFFILIATION NOT ASSIGNED |
| To: | |
| References | |
| OLA-2-I-MFP-075, OLA-2-I-MFP-75, NUDOCS 9401110259 | |
| Download: ML20059E527 (9) | |
Text
__
!8 dp -E75 Sz3 -D&2 T-MFP'73 NUCLEAR RECUtATORY COMMISSION 4M@93%3N001 D5bep4m F
'r Docht No. 9'h['hi,1 *MQ Ni *l EE !$~
DC2-M tu. :e of EDfR_6A3MMt' f_@ E!".6 March 10, 1993 sun _ ____ _._ _
,. </
Ar, _. _ _ _ _.
..a7
'93 CCI 28 P6 :09 o~ - M
_ __.c,w C.'
,1 EJ" 'll A
1AIC.
1
~
63;Ct4I I
/b J
DC2-93-MM-N001 DG 2-2 FAILED TO ACHIEVE RATED VOLTAGE DURING M-9A MANAGEMENT
SUMMARY
On December 29, 1992, during STP M-9A, DG 2-2 output voltage only reached 105V then decayed to 90V at a stable 900 rpm and 60 hz (ref. 1).
The acceptance criteria is 110V to 128V at 60 i 1.2 Hz within 13 seconds from the start signal (ref.
2).
Preliminary investigation determined the failure to achieve rated voltage was due to mispositioning of the slip ring brushes.
The cause of the mispositioning has been l
identified as inadvertent and undetected movement of the -
slip ring brushes due to loosened brush rigging mounting bolts during inspection of the shaft end for thrust load a 4al movement followed by retightening of the mounting bolting without slip ring brush position inspection.
l On March 10, 1992, the TRG reconvened in room 604 of the l
administration building at 10:00 am PST to sign this NCR and identify it as ready for PSRC review and concurrence for closure.
^
1 l
l 93NCR%%93MMNOO!JCN Page 1
of 11 9401110259 930819 DR ADOCK 05000c]S.-
t :
r DC2-93 -MM-N001 D5 March 10, 1993 5.
Dec. 30, 1992, 2225 PST:
DG 2-2 declared operable after a successful M-9A (ref. 6).
E.
Other Systems or Secondary Functions Affected:
None.
F.
Method of Discovery:
Utility personnel, during the performance of an STP identified the problem.
G.
Operator Actions:
i None required.
H.
Safety System Responses:
None required.
III.
Cause of the Event A.
Immediate Cause:
DG 2-2 failed to reach an acceptable output i.
voltage during an STP M-9A test.
B.
Determination of Cause:
1.
Human Factors:
l a.
Communications: No Electrical Maintenance i
personnel were involved with the generator shaft axial thrust load movement inspection.
b.
Procedures: Inadequate information was contained in the maintenance procedure.
c.
Training:
N/A.
d.
Human Factors:
N/A.
l 9mcam93MMNOOUCN Page 4
of 11
/
t l
.r h
DC2 MM-N001 D5 March 10, 1993 e.
Management System:
N/A.
2.
Equipment / Material:
a.
Material Degradation:
N/A.
b.
Design: N/A.
c.
Installation:
N/A.
d.
Manufacturing:
N/A.
e.
Preventive Maintenance: N/A.
f.
Testing:
N/A.
g.
End-of-life failure:
N/n.
C.
Root Cause:
The root cause for the generator slip ring brush mispositioning was inadequate information available to inform personnel of the extent of potentially affected subassemblies during generator bearing cover removal.
D.
Contributory Cause:
Barring the engine over with the generator bearing end cover removed, without provision for holding the slip ring brushes in place is not a normal evolution.
The measurements were requested by NECS - Engineering as a means for obwaining
)
comparison data that might be useful in determining the cause for the DG 2-3 vibration problem.
IV.
Analysis of the Event i
A.
Safety Analysis:
Safety-related (Class 1E) electrical loads are supplied from three 4160V vital buses (F, G, and _
H) for'each unit.
Each vital bus can be supplied from the 500kV Switchyard, the 230kV Switchyard, the main generators, or the DGs.
The DGs can provide power for engineered safeguards (Class 1E)-
l 93NCRW93MMNOO1.JCN Page 5
of 11
.i DC2 - 9 3 -MM-N001 D5 l
March 10, 1993 motors and loads used for emergency core cooling, reactor shutdown and other vital safety functions when the main generators and offsite power sources are not available in the event of a loss-of-offsite power or other design-basis event.
During a design-basis event,' with DG 2-2 in a degraded condition, one bus of vital 4160V power would not have be_.4 available for Unit 2 support.
However, DGs 2-1 and 1-3 were available to provide power to the other two Unit 2 vital 4160V buses during the time that DG 2-2 was inoperable.
Since only two vital buses are necessary to support DCPP accident analysis, the health and l
safety of the public were not adversely affected by this event.
l B.
Reportability:
1.
Reviewed under QAP-15.B, "Nonconformances,"
and determined to be non-conforming in accordance with Section 2.1.2.
2.
Reviewed under 10 CFR 50.72 and 10 CFR 50.73 per NUREG 1022 and determined to not be reportable.
Determined to be reportable in accordance with Regulatory guide 1.108 as a valid failure of EDG 2-2 to start.- For more information see Special Report 92-06 (Att.
Two).
3.
This problem will not require a 10 CFR 21 report.
l 4.
This problem will not be reported as an INPO Nuclear Network entry.
5.
Reviewed under 10 CFR 50.9 and determined the event was not reportable.
6.
Reviewed under the criteria of administrative procedure (AP) C-29, "Cperability Evaluation,"
requiring the issue and approval of an OE and determined that an OE is not required.
V.
Corrective Actions l 93NCRWP\\93MMNOOlJCN Page 6
of: 11
)
u 9
1 s
DC2 MM-N001 D5 March 10,-1993 i
A.
Immediate Corrective Actions:
i The generator shaft end assembly was. disassembled and the slip ring brushes were replaced.
B.
Investigative Actions.
1.
For the TRG's review, create proposed revisions to the vendor manual and appropriate maintenance procedures to' include a diagram-and/or " caution" note that the end bearing l
place, and that.the brushes should be checked.
j cover bolts also hold the brush bracket in 1
i by Electrical Maintenance during reassembly.-
RESPONSIBILITY:
JL. Price RETURN Mechanical Maintenance (PGMC)
AR A0289815,~AE:# 01-l C.
Corrective Actions to Prevent Recurrence:
i 1.
Create a Field Change' Transmittal (FCT) to the vendor manual to' include a diagram and/or
" caution" note that'the end bearing cover bolts also hold-the brush bracketLin' place, I
and that the brushes'should be checked by l
l Electrical Maintenance ~during reassembly.
i RESPONSIBILITY:
L.-Price RETURN i
Mechanical Maintenance - (PGMC) '
Tracking AR:
A0289815, AE # 03' l
Outage Related?-No
(
OE Related?
No NRC Commitment? Yes CMD Commitment? No-2.
Revise Maintenance Procedures MP E-21.1 and M-21.27 to include a diagram and/or " caution" l
note that the end bearing cover bolts also hold the brush bracket in place,'and that-the brushes should be checked by during.
reassembly.
RESPONSIBILITY:
L. Price RETURN 1
Mechanical Maintenance-(PGMC)
AR A0289815, AE # 04 Outage Related? No
- l MNCRWMMMMNOOUCN Page
'7' of 11 i
o
c' v
DC2 MM-NC 01 DS Nkrch'10, 1993 OE Related?
No NRC' Commitment? Yes CMD Commitment? Yes 3.
Request the creation of lamacoids cautioning.
that whenever the end cover _is_ removed, brushes should be checked during reassembly, and the installation of the lamacoids to agree with the revised MP M-21.27.
Install the lamacoids following approval'of the revised procedure.
RESPONSIBILITY:
L.
Price RETURN Mechanical Maintenance AR A0289815, AE # 05 Outage Related? No OE Related?
No NRC Commitment? Yes CMD Commitment? No D.
Prudent Actions (not required for NCR closure):
1.
System Engineering to pursue the interpretation of " valid-failure" versus "non-valid-failure" for DG start testing as relates to the recent DG 2-2 event.
RESPONSIBILITY:
C.
Pendleton ECD: 3/19/93 System Engineering (PTEB)
AR A0295561 2.
System Engineering to evaluate the current practice of utilizing an existing'STP as a post-maintenance functionality verification test considering the ramifications of STP failure and subsequent LCOs.
l l
RESPONSIBILITY: S. Bednarz ECD: 3/19/93 l
System Engineering (PTEB)
VI.
Additional Information A.
Failed Components:
1 i
None.
l nucawnnuunooucN Page 8
of 11 l
w
lf*
DC2 - 9 3 -MM-N001 D5 March 10, 1993 i
B.
Previous Similar Events:
l None.
l C.
Operating Experience Review:
1.
NPRDS:
N/A.
2.
NRC Information Notices, Bulletins, Generic Letters:
None.
3.
None.
D.
Trend Code:
B2 (procedure deficiency, incomplete) - MM (Mechanical Maintenance)
E.
Corrective Action Tracking:
1.
The tracking action request is A0289815.
2.
Corrective actions are not outage related.
F.
Footnotes and Special Coraments:
None.
G.
References:
l 1.
AR A0289381 (initiating AR).
2.
STP M-9A.
3.
4.
Clearance 00039086.
5.
W/O C0108802.
6.
Clearance 00039093.
l 93NCRWPN93MMNOOlJCN Page 9
of 11
%.'(;
- DC2 MM-N001 D5-
~
March 10, As93 7.
AR A0287232, AE #.25.
H.
TRG Meeting Minutes:
1.
On January;7, 1993, at 3:00'pm'PSTfin room'424 of.the administration building the'TRG metrfor the initial time to discuss the failure.of~DG 2-2 to meet the acceptance criteria of STP'M-9A on December' 99,.1992..
It<wasEidentified thatino procedure describes the relationship between the mounting bolts for the generator bearing ~ shaft cover _and the slip ring brush rigging.
A' suggested corrective _ action was.to revise procedures to provide.this'information'.
The TRG will reconvene on' January 15, 1993.
2.
On January 15, 1993, the TRG reconvened to-discuss causes-for this eventrand corrective.
actions. 'It was determined 1that the NCR cannot be closed until submittalfof'Special' Report 92-06 (due'to the NRC January 28,.
1993) (Att. ; 2).
Corrective actions as noted above were identified and it.was agreed ~to reconvene the 13tG following Special Report 92--
06 submittal to-confirm those actions necessary to complete this.NCR.
3.
On February 11, 1993, the'TRG' reconvened at 1:00 pm PST in room 533 of the administration building-to discuss the~special report ~(Att.-
Two) and any' actions required to complete this' NCR.
Investigative and corrective actions, as noted herein, were reviewed.and minor revisions made.
to the personnel assigned and scheduled completion dates.as appropriate.
Two new prudent actions were-identified as noted herein.
The estimated' completion date.for this NCR is April 30, 1993.
This:NCR writeup will be distributed'for comment,.withfcomments expected by March!4,-1993, and a reconvene with. the intent-of signing 1 completion 'of this -
NCR is planned for March 10, 1993.
l 93NCRWM93MMN001JCN Page 10- of 11
.-. -....... -. -.---.=__ _ __
DC2 MM-N001 D5 March 10, 1993-1 4.
On March 10, 1992, the TRG' reconvened-in' room:
. i 604 of the administration building at'10:00 am l
PST to sign this1NCR and identify'it as ready for PSRC review and concurrence.for-closure.
I.
Remarks:
None.
J.
. Attachment (s):
1.
DG Generator' Bearing Area Drawing 2.
Special' Report.92-06
'l i
i j
l
- s 1
-)
1 l
i l
l l 93NCRW93MMNOOlJCN Page 11 of '11 v....,
.,-,.-.....-..,,4