ML20059M848
| ML20059M848 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/18/1993 |
| From: | AFFILIATION NOT ASSIGNED |
| To: | |
| References | |
| OLA-2-I-MFP-032, OLA-2-I-MFP-32, NUDOCS 9311190379 | |
| Download: ML20059M848 (11) | |
Text
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NCR DC2-93-EM[NO37 Rev. 00
.~..:.n DRAFT:
July 22, 1993 93 rr 28 P5 28 MANAGEMENT
SUMMARY
During STP V-3PS, Auxiliary Feedwater Pump discharge valve LCV-109 failed to open electrically.
The valve closed in accordance with step 12.5.4 of the procedure, but when it was to be reopened per step 12.5.5, it would not.
Acceptance criteria is for LCV-109 to stroke fully open in less or equal to 20 seconds.
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92NCRWP\\293EMNO37.PGD Page 1
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'NCR DC2-93-EM-NO37 Rev. 00$
9 DRAFT:
July 22, 1993 NCR DC2-93-EM-N037 j
LCV-109 FAILED TO STROKE 'OPEN -
I.
Plant Conditions
=!
Unit 2 was in Mode 1- '(Power Operation).at 100%' power.
II.
Descriotion'of Event 1
A.
Summary:-
During STP V-3PS, Auxiliary.Feedwater Pumpl' discharge valve'LCV-109. failed to1open electrically.
The valve closed in accordance.with.
step 12.5.4 of the procedure,;but when it was to.
be reopened per step 12.5.5,iit would;not.
B.
Background:
List applicable Tech. Specs, STPs, Administrative Procedures, and departmental or company policies and give a.brief summary of their-requirements.
Provide any additionalLinformationtdescribing j
equipment or system operation'that'will' help'the q
reader understand the event.-
)
- l C.
Event
Description:
During STP V-3P5, Auxiliary FeedwaterTPump discharge valve LCV-109 failed to open electr'ically.
The valva closed in acc6Edance with step 12.5.4 of the procedure, but:when it was to be reopened per step 12.5.5,.it would not.
Operations attempted to determine what.the' exact problem was.
When'they opened the breaker. cubicle to observe the operation of'the contactors they observed the following:
When the control switch was taken to the closed H
position, the closed contactor pulled in for about 2 seconds. Then when the control switch.was taksn 4
to the open position, the open contactor pulledEin' d
for about 2 seconds
'The open contactor would not:
pull in on any further attempts unless the switch
.l was taken to the'close position forLseveral
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NCR DC2-93-EM-NO37 Rev. 00 DRAFT:
July 22, 1993 seconds first.
Operations then went to the valve to listen for any unusual sounds and then when the valve was operated, (again close first, then open), the valve opened fully. No unusual noises were heard from the valve.
==
Conclusion:==
The torque switch was preventing.the valve from opening.
After the valve was'stroqued from the fulled closed position to the 10% open position several times, the torque switch freed up and allowed the valve to move full travel.
it is unknown if the problem is due to a faulty torque switch, improper setpoint of the torque switch or a problem with the valve that was resolved after a few partial strokes.
A new' torque was installed and the post maintenance tests show new torque switch to be functioning properly.
j D.
Inoperable Structures, Components, or Systems that Contributed to the Event:
The torque switch in LCV-109 was preventing the valve from opening.
E.
Dates and Approximate Times for Major Occurrences:
1.
July 15, 1993; __:__ PST:
Event date./discov ery date. During STP V-3P5, Auxiliary Feedwater Pump discharge valve LCV-109 failed to open electrically.
F.
Other Systems or Secondary Functions Affected:
None.
G.
Method of Discovery:
During STP V-3P5, Auxiliary Feedwater Pump discharge valve LCV-109 failed to open electrically.
H.
Operator Actions:
None.
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i NCR DC2-93-EM-NO37 Rev. 00 DRAFT:
July 22, 1993 I.
Safety. System Responses:
None.
III.
Cause of the Event A.
Immediate Cause:
A malfunctioning torque switch would not permit valve FW-2-LCV-109 to fully close.
B.
Determination of Cause:
]
A.
Causal Factors:
1.
Communications:
j i
Not a factor.
2.
Procedures:
Not a factor.
3.
Training-Not a factor.
I 4.
Human Factors:
Not a factor.
5.
Management System:
,,, i Not a factor.
j 6.
Equipment / Material:
The torque switch was inspected and determined that the switch contact was not closing.
If the switch had been properly balanced the valve would have properly operated.
The Electrical Department had.
assumed that the' vendor supplied equipment was properly set.
C.
Root Cause:
To be determined.
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NCR DC2-93-EM-NO37 Rev. 00 DRAFT:
July 22, 1993 D.
Contributory Cause:
To be determined.
IV.
Analv_ sis of the Event A.
Safety Analysis:
The safety function of the AFW~LCVs'is to maintain a sufficient inventory of water in.the' steam generators (SGs) in the event of a loss of main.
feedwater'through valve or pump failureLor feedwater-line' break.
The. torque switch that malfunctioned was'for the valve closing direction seating of FW-2-LCV-109 (turbine driven auxiliary i
There are three events for t
which.the AFW LCVs are required to.close: SG tube rupture (SGTR), main feedwater line break (MFLB) and main steam line break.(;MSLB).
For a SGTR the concern is to prevent the main steam lines from filling with water since the lines and supports are not seismically qualified for that_ condition.
Also, overfill could result in the SG being water-solid that would lead.to water relief through the SG safety valves.
Dose i
consequence. analysis for a.SGTR are based on' steam-4 release to atmosphere.
Water relief ~could carry significantly greater activity to the' atmosphere.
l i
For this accident'itLis assumed that operators can identify the accident type and isolate flow to the faulted-SG within 30 minutes.
.If:FW-2-LCV-109 did I
not fully close from a remote electrical _ signal operators could manually' complete _the valve closure.
For a MFLB the concern is. primary system heat up due to loss of heat transfer capability in.the SGs.
This accident has been analyzed for both offsite power available and unavailable.
No core damage will occur in either event.
For MFLB the design basis'for the AFW system requires that it deliver a. total of 440 gpm; 1
(minimum) to at least two intact SGs~within ten-minutes.
The requirements for a MSLB are1similar, although the cooling requirements _are not as-
.Iin-restrictive.
A worst case MSLB on steam lead'4 92NCRWP\\293EMN037.PGD Page 5
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t NCR.DC2-93-EM-NO37 Rev. 00-4 DRAFT:
July 22',;1993 the GE/GW area will cause.SG 2-4 to depressurize
~
and result in a' harsh!environmentLin that area-which could disable:FW-2-FCV-38,5FW-2-LCV-113 and FW-2-LCV-115.
As a' result of the MSLB, all three-AFW pumps would receive: a start signal..It'can be' assumed that a single active-failure offemergency.
diesel generator 2-2 (bus H) prevents the operation of AFW pump.2-2.
AFW pumps 2-1 and 2-3 would start and, due to'theLreduced backpressure, deliver-large runout flows to the faulted. steam-
.l line's SG.
Because FW-2-LCV-113 and FW-2-LCV-115
- t were disabled by the harsh environment:they>are f
not able to perform their. runout protection function, and therefore, AFW pump 2-3lis l
conservatively assumed to trip on.overcurrent.:
This leaves only AFW pump.2-1 which would deliver nearly al' its flow to'tha faulted steam'line's.
j SG.
Due to the' unbalanced torque switch, this flow cannot be isolated from'the controlEroom or manually due to the harsh environment.
However,-
operating procedure 0-22, " Emergency Operation Of-Motor Operated Valves", permits an operatoritot remotely, electrically close, valve'FW-2-LCV-109 from it's motor's b'reaker cubicle with a signal-that bypasses the faulty torque' switch'.
In accordance with the evaluation crit'eria of NUREG-1022, the single failure of a component in.a system which has redundancy is not a-reportable event or a. condition tnac willLadversely affect 1
plant safety.
Previousfevaluations werel overly conservative but are retained as' shaded-text for historical information.
~
?
Thus, the health and safety of the;public,were not adversely affected by this condition.
B.
Reportability:
1 1.
Reviewed under QAP-15.B and determined to be non-conforming in accordance with Section-l 2.1.8.
2.
Reviewed under 10'CFR 50.72 and 10 CFR.50.73 per NUREG 1022 and determined'not~to be' i
reportable.
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I' NCR DC2-93-EM-NO37 Rev. 00 DRAFT:
July 21, 1993 j
3.
Reviewed under 10 CFR Part 21 and determined that this problem does not involve defects in vendor-supplied services / spare parts in stock.
4.
This problem will not be reported via an INPO Nuclear Network entry.
5.
Reviewed under 10 CFR 50.9 and determined to be not reportable since this event does not have a significant implication for public health and safety or common defense and security.
6.
Reviewed under the criteria of AP C-29 requiring the issue and approval of an OE and determined that an OE is not required.
V.
Corrective Actions A.
Immediate Corrective Actions:
The torque switch on the Limitorque motor operator for valve FW-2-LCV-109 was replaced and appropriately adjusted.
B.
Investigative Actions:
1.
Verify that the operator maintained the switch in the closed position for a period of five seconds during the troubleshouting test of LCV-109.
RESPONSIBILITY: A. Toy ECD: 07/29/93 DEPARTMENT:
Predictive Maintenance l
Tracking AR:
A312387, AE STATUS:
INITIATED.
2.
Initiate a Work Order to look at the control l
switch and the motor starter.or contactor for proper operation.
RESPONSIBILITY:
R. Hanson-ECD: 08/06/93 l
DEPARTMENT:
Electical Mbintenance Tracking AR:
A312387, AE STATUS:
INITIATED.
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1 NI NCR DC2-93-EM-NO37 Rev; 00' l
DRAFT:
July;.22, 1993 l
l 3.
Establish a Work Order to' stroke the valve on-
'I accelereted frequency (everyL31~ days) fin:the i
presence af' Electrical-Maintenance.'
RESPONSIBIL.:TY: R. Hanson' ECD: 07/29/93:
DEPARTMENT:
Electical? Maintenance ~
j Tracking AR:
-A312387,..AE.# __
STATUS:
INITIATED.
1 i
4.
Check the maintenance 1historyson the other-fiveLSMB.000' valves to determinefif'their.
' torque ~ switches were'ever balanced.on site; RESPONSIBILITY:
C. Short".. ECD: 08/06/931
. DEPARTMENT:
Electical Maintenance 1 i
TrackingfAR:
.A312387, AE #__.
STATUS:
INITIATED.
T C.
Corrective Actions to Prevent Recurrence:
1.
To be= determined.
RESPONSIBILITY:
' ECD:
DEPAR'IMENT:
Tracking AR_:
'A0
, AE ' #_..,
j Outage Related? Yes/No OUTAGE:.( R_Jor U_FO).
OE'Related?
.Yes/No
.NRC Commitment? Yes/No I
CMD Commitment? Yes/No t
D.
Prudent Actions L (not required [ for[NCR ' closure)
To be determined.
VI.
Additional Information 1
A.
Failed Components.:
i None.
B.
Previous Similar Events:
l A.
Failed Component.(s):
The torque switch on the Limitorqueimotor operator of valve FW-2-LCV-109.
t
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92NCRWP\\293EMNO37.PGD Page Et of 7
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NCR DC2-93-EM-N037 Rev. 00
. DRAFT:
July 22, 1993 1
I B.
Previous NCRs on Similar. Problems:
l None.
C.
Operating Experience ~ Review:
1.
NPRDS:
A search of the database was performed using the manufacturer-Limitorque,-Model SMB, and the< keyword torque switch.
The system returned approximately 1500 items using the'specified search parameters.
Out of the 1500 items approximately 90 failures can be attributed to switch-i setpoints.
2.
NRC IE Information Notices, Bulletins j
and Generic Letters:
IE Notice-86-71 was reviewed.- This notice was. concerned with cracked limit switches, therefore it is not1 applicable to this' event.
j l
3.
l SER~38-87.provided guidance.on1 checking a
the. balance'on newlyLinstalled-limitorques.
The~ corrective actions for this'SER include revising MP E-53.10C to i
provide guidance'on balancing for all the types of-Limitorques installed inLthe-
)
plant.
At the time of the procedure 1
revision ~no SMB-000. type' actuators, which were required to torque inLthe closed direction, were installed in1the' plant.
Therefore, the type of' actuator discussed in this NCR was not included-'in the procedure revision.
4.
LERs:
LER 83-014 was reviewed.
This LER'is not applicable because'the torque' switch-malfunction was' attributed to binding in the switch.
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Li' s,..
.s NCR DC2-93-EM-NO37 Rev. 00 DRAFT:
July 22, 1993 D.
Trend Code:
XX-C2(Main Supplier-material deficiency),
[
EM-C3(Electrical Maintenance-improper installation).
To be determined.
C.
Operating Experience Review:
1.
NPRDS:
~
Not applicable.
2.
NRC Information Notices,' Bulletins, Generic LettJrs:
To be determined.
3.
To be determined.
D.
Trend Code:
Responsible department __, and cause code __.
E.
Corrective Action Tracking:
1.
The tracking action request is-A0
.. ~ <.
2.
Are the correctiva actions outage'related?
To
{
be determined.
j I
F.
Footnotes and Special Comments:
TBD.
G.
References:
1.
Initiating Action Request-A0311830.
2.
Tracking AR.
H.
TRG Meeting Minutes:
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i NCR DC2-93'-EM-NO37 Rev.
00.'
DRAFT:
July 122, 19934
~i i
On July 22,- 1993, the TRG convened'and'consideredi
,i the following:
-t, The TRG reviewed:the event.
35% of'the valve-1 travel. Torque' switch problem. The valve.'openeds properly.
Torque switchjout'of= balance.
Relied-on the open torque._ Contacts.in the~open-direction.
After the torque 1 switch.was replaced,-
the. valve worked ~aod'and the valve was-declared-operable. Best as found balamnce/
1 I.
Remarks:
i i
j None.
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s 1
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