ML20059C721
| ML20059C721 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/19/1993 |
| From: | AFFILIATION NOT ASSIGNED |
| To: | |
| References | |
| OLA-2-I-MFP-086, OLA-2-I-MFP-86, NUDOCS 9401060044 | |
| Download: ML20059C721 (23) | |
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MANAGEMENT
SUMMARY
l On October 22 1991, an NRC inspector identified that Containment Wide Range Sump Level Channel 942A indication had dropped below the bottom of its scale.
Work performed appeared to return the indication to normal; the channel was returned to service and the action statement exited.
On October 23 1991, the NRC inspector again identified that channel 942A indication had dropped.
The action statement was entered, and troubleshooting efforts began.
I&C technicians suspected that the indication shifts were due to poor connections between 2LM-942A and its rear edge connector.
The modifier was moved to a different slot in its rack, and the channel was monitored over the next three days with no abnormalities noted.
A formal jumper was then initiated to document the movement of the modifier and cables, and the channel was returned to service and declared operable on October 26 1991.
Channel 942A indication shifted low an additional nine times over the period of November 1991 through March 1992.
In each case the channel indication was returned to norma 2 and the channel declared operable while root cause analysis efforts continued.
Major portions of the channel were replaced on March 23, 1992 and the problem had not recurred since.
The root cause for the indication shift of channel 942A is unknown.
Additional troubleshooting has been unable to isolate the mechanism causing the indication shifts.
Corrective actions identified in this document will minimize the possibility of problem recurrence and ensure prompt detection of indication shifts.
9401060044 930819 PDR ADOCH 05000275 C
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9 DC2-91-TI-N096 D8
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January 25, 1993 LOSS OF WIDE RANGE REACTOR CAVITY SUMP LEVEL CHANNEL 942A I.
Elant conditions:
Unit 2 was in Mode 3 (Hot Standby) or Mode 2 (Startup) during the time frame of this event.
II.
Description of the Problem:
A.
Problem:
l l
On October 10, 1991, containment sump wide range level channel 942A indication dropped below the bottom of its scale.
On October 15, 1991, at 0958 PDT, Unit 2 entered Mode 3.
A' that time, Technical Specification (TS) 3.3.3.6.a became applicable.
On October 22 1991, an NRC inspector noted that the
" slue for Containment Wide Range Sump Level on the Safety Parameter Display System (SPDS) Critical Safety Function CSF-5 was displayed with a question mark.
Operators then examined the recorder for channels 942A and 943A on panel PAM-1 to determine the status of the channels.
They determined that while channel 943A was operating properly, channel 942A was pegged low on the recorder (2LR-942A).
The operators then notified I&C to determine the cause of this indication.
When I&C technicians measured the loop current on channel 942A, they determined that the output ot che enannel had dropped to a low value of loop current (approximately 3.6 milliamperes (mA)).
This symptom was similar to those exhibited in November 1990, where channel failures resulted in generation of NCR DC2 l TI-N076 (Reference 1).
Initial troubleshooting efforts included removing the power fuses for the modifier.
Following this action, channel loop current returned to normal values.
The channel was returned to service and declared operable on October 22, 1991, at 2115 PDT.
The following day, the channel was observed to be again indicating low.
Additional troubleshooting efforts led I&C technicians to believe that the root cause of the
]
indication shifts was poor connections between modifier I
2LM-942A and it's rear edge connector.
The modifier l
l 91NCR%79tTIN(% DPs Page 2
of 23
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DC2-91-TI-N096 D8 January 25, 1993 was moved to slot #2 in its rack, along with its associated cabling.
After monitoring channel performance for three days with no observed abnormalities, the modifier movement was formalized under a jumper log, and the channel was returned to service.
B.
Inoperable Structures, Components, or Systems that Contributed to the Problem:
None.
C.
Dates and Approximate Times for Major Occurrences:
1.
August 21, 1990:
Original failure of channel 942A which resulted in NC" DC2-90-TI-N076.
i 2.
November 6, 1990:
NCR DC2-90-TI-N076 initiated.
Channel 942A experienced repetitive indication shifts over the period of 11/6/90'through 12/13/90 while investigative efforts continued to attempt to determine root cauce.
Replacement 1
of the channel power supply and cleaning of connectors on 11/29/90 appeared to have solved the problem.
On 12/13/90, the channel was i
recalibrated and returned to service.
1 3.
September 28, 1991, 0850 PDT:
Channel 942A discovered failed 91NG%74RN0% nn Page 3
of 23 j
'l DC2-91-TI-N096 D8 January 25, 1993 l
low due to a blown power supply.
The plant was in Mode 6 and the actions of T.S.
3.3.3.6 did not apply.
Investigation showed this power supply failure to be an isolated incident (one other occurrence noted since the four channels were installed in 1987).
The power supply was replaced and the channel was calibrated and returned to service.
4.
October 4,
1991:
NCR DC2-90-TI-N076 closed.
This NCR listed the root cause for the original failure as
" unknown", since thorough troubleshooting and analysis efforts had failed to disclose a failure mechanism which could be positively I
identified as being related to the symptoms displayed.
The NCR was closed after actions taken i
appeared to have corrected the symptoms.
5.
October 7, 1991, 1030 PDT:
Channel 942A indication shifts low (found by 91NCRwminN0% DPs Page 4
of 23
l DC2-91-TI-N096 D8 January 25, 1993 subsequent examination of LR-942A recorder trace).
6.
October 9, 1991, 2300 PDT:
Channel 942A returns to normal value (found by subsequent examination of LR-942A recorder trace).
7.
October 10, 1991, 0500 PDT:
Event Date.
Channel 942A indication again shifts low (found by subsequent examination of LR-942A recorder I
trace).
j B.
October 12, 1991, 1104 PDT:
Channel 942A l
declared operable following calibration described in item (3) above (per T.S.
summary sheet i
attached to SFM logs dated October 12, 1991).
I 9.
October 15, 1991, 0958 PDT:
Unit 2 enters Mode 3.
Channel 942A was required to be operable but was not.
- 10. October 22, 1991, 0958 PDT:
Expiration of T.S.
3.3.3.6 action statement a on channel 942A.
I
- 11. October 22, 1991, 1500 PDT:
Discovery Date.
Channel 942A
(
indication 91NCRWP91 TINT 74 DPs Page 5
of 23
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DC2-91-TI-N096 D8
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January 25, 1993 discovered shifted low.
T.S.
3.3.3.6 Action a entered.
- 12. October 22, 1991, 2115 PDT:
Channel 942A indicating normal values.
Channel declared operable and returned to service.
- 13. October 23, 1991, 1310 PDT:
Channel 942A indication shifts low.
Channel declared inoperable and T.S.
3.3.3.6 action a entered.
- 14. October 23, 1991, 1618 PDT:
Modifier LM-942A moved to slot #2 of 942A rack in panel RRM.
Commence monitoring of channel 942A.
- 15. October 25, 1991:
NCR DC2-91-TI-N096 l
initiated for failure to meet T.S.
3.3.3.6 action statement a requirements (reference items 9, 10, and 11 above).
- 16. October 26, 1991, 1618 PDT:
After monitoring channel 942A loop output for three days with no observed problems, channel returned to service and declared operable.
- 17. November 8 and 12, 1991:
Channel 942A indication shifted low.
The indication shift j
}
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of 23 i
i
DC2-91-TI-N096 D8 January 25, 1993 was noted during monitoring of the channel by I&C and/or Operations personnel, the channel indication was returned to normal and the channel was declared operable before TS 3.3.3.6, Action a was exceeded.
- 18. November 15, 1991:
- 19. December 17, 1991, et al:
Channel 942A indication shifted low on December 17, 1991; January 29, 1992; February 8, 1992; February 13, 1992; February 21, 1992; February 23, 1992 and March 18, 1992.
In each case the indication shift was noted during the surveillance instituted by OE 91-12.
The indication was returned to normal and the channel was declared operable before TS 3.3.3.6, Action a was exceeded.
- 20. March 23, 1992:
Transmitter LT-942A and modifier LM-942A were replaced during a forced outage.
Channel calibrated and 9tNCRWP.91TNM6 DPs Page 7
of 23
l DC2-91-TI-N096 D8
~
l January 25, 1993 returned to service.
D.
Other Systems or Secondary Functions Affected:
None.
E.
Method of Discovery:
An NRC Inspector identified the channel discrepancy during observation of SPDS parameters.
F.
Operator Actions:
Operations Department personnel declared wide range I
containment reactor cavity sump level channel 942A inoperable as required by T.S.
3.3.3.6 and entered the appropriate T.S. Action Statement.
G.
Safety System Responses:
None.
III.
Cause of the Problem:
A.
Immediate Cause:
Containment wide range sump level channel 942A indication shifted low.
B.
Root Cause:
The root cause for the indication shift of Channel 942A is unknown.
Thorough investigation into the design of the channel and the mechanism causing the channel indication to shift has been performed and no definitive cause for this indication shift has been identified.
The following corrective actions were identified and will minimize the probability of recurrence of this problem and will additionally ensure the timely detection of any indication shift for these channels.
The level transmitter and modifier associated with this channel have been replaced.
These l
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of 23 i
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I DC2-91-TI-N096 DB i
January 25, 1993 were the components most suspect for the identified malfunction.
The malfunction has not recurred since their replacement.
J LER 2-90-010 corrective actions implemented training for Operations, Work Planning and I&C personnel to ensure these personnel are aware of the meaning of the blue flashing paths on the Safety Parameter Display System (SPDS).
Corrective action number one below revised STP I-1B to ensure that Operations personnel discover potential or apparent failures of these channels in a timely manner.
Corrective action number two below ensures these channels are not returned to operable status without having adequate compensatory measures in place.
IV.
A.nalysis of the Problem:
A.
Safety Analysis:
i Wide range containment reactor cavity sump level channels are post-accident instrumentation required by Regulatory Guide 1.97 to provide quantitative data about water level inside the containment structure from the 64 foot elevation to the 98 foot elevation.
These data are used to verify the occurrence of a lcss of j
coolant accident (LCr.y and to evaluate plant conditions to assure proper response to an accident.
Using a combination of other instrumentation available as described below, the severity of an accident could l
be evaluated to determine the correct response.
Various annunciators and indicators are available for identifying a LOCA.
During a LOCA, containment pressure and temperature increase; reactor coolant system inventory decreases; and the containment reactor cavity sump level, containment structure sump level, and containment recirculation sump level increase.
The wide range pressure recorders record containment pressure.
The wide range temperature indicators are used to monitor containment temperature.
91NCRWT*9tTIN0% DPs Page 9
of 23 i
5
DC2-91-TI-N096 D8 January 25, 1993 Reactor coolant system (RCS) inventory is monitored by l
pressurizer level indicators and the reactor vessel vide range level indication system.
These indications could be used to diagnose the severity of an accident and assure that the core is adequately cooled.
Levels of the various sumps in the containment building are also monitored.
The narrow range containment structure sump level channels indicate reactor cavity sump level from the 60 foot 4 inch elevation to the 63 foot 6 inch elevation.
The residual heat removal recirculation sump indicators measure the residual heat removal recirculation sump level between the 88 foot elevation and the 96 foot 6 inch elevation.
A LOCA condition could be identified using the narrow range containment structure sump level channels.
Since a LOCA condition is identified by using the diverse instrumentation noted above, if a LOCA condition had occurred, the control room would have been promptly notified so that prompt applicable corrective actions could be taken.
Thus the health and safety of the public were not affected by this event.
B.
Reportability:
1.
Reviewed under QAP-15.B and determined to be non-conforming in accordance with section 2.1.4.
2.
Reviewed under NUREG 1022 and determined to be reportable in accordance with 10 CFR
- 50. 73 (a) (2) (i) (B) in that the LCO for channel 942A was exceeded.
See Licensee Event Report (LER) 2-91-010 for more information.
3.
This problem does not require a 10 CFR 21 report.
4.
This problem does not require reporting via an INPO Nuclear Network entry, however, an inquiry will be made to determine if any other plants have experience similar problems on similar equipment.
5.
Reviewed 10 CFR 50.9 and determined event was not reportable under 10 CFR 50.9 since the event is i
being reported under 10 CFR 50.73.
V.
Corrective _j.ctions:
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DC2-91-TI-N096 D8 January 25, 1993 A.
Investigative Actions:
1.
Determine if the reactor cavity sump level channels were inoperable when 1 mV out of tole ance by reviewing the associated scaling calculations.
RESPONSIBILITY:
D.
Reed COMPLETE DEPARTMENT: I&C Tracking AR: A0249976. AE # 01 2.
Provide the vendor with all available data on the reactor cavity sump level channelm for further failure investigation.
RESPONSIBILITY:
D. Reed COMPLETE DEPARTMENT: I&C Tracking AR: A024997C, AE # 02 3.
Develop a drawing of other UQ775 loads to look for grounds.
RESPONSIBILITY: J.
Hefle.r COMPLETE DEPARTMENT: NECS Tracking AR: A0249976, AE / 07 4.
Determine when other UQ775 loads were added and determine the correlation with the first shift.
Determine if UQ775 is overloaded.
RESPONSIBILITY: J. Hefler COMPLETE DEPARTMENT: NECS Tracking AR: A02499/o, AE # 08 5.
Get electronics expert on site to aid in the investigation.
Obtain new charts on other UQ775 loads for comparison.
Obtain better charts for containment pressure vs. wide range level.
RESPONSIBILITY:
D.
Reed COMPLETE DEPARTMENT: I&C Tracking AR: AC249976, AE # 09 i
6.
Determine if UQ775 loads are T.S.
Schedule a containment purge watch for 942A.
Load up UQ775 and try to cause 942A to shift.
Install a separate P/S 942A 4-20 loop.
This item to remain open to provide for a response in the event of another 91NCRWP.91 TIN 04DPS Page 11 of 23
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DC2-91-TI-N096 DB January 25, 1993 channel shift.
If the channel has not exhibited another anomalous shift by November 30, 1992, this action will be considered completed.
l RESPONSIBILITY:
J.
Reinholdt COMPLETE DEPARTMENT: I&C Tracking AR: A0249976, AE #10 7.
Determine if it is possible to perform a cap fill at power for old Barton System.
RESPONSIBILITY: M.
Calora COMPLETE DEPARTMENT: GC Tracking AR: A0249976, AE # 11 No.
Radiation exposure would be too high for the job to be accomplished at power.
I 8.
If channel 942A shifts again, check all external l
connections, tighten and inspect crimps, and do a visual inspection of the ring lugs.
If a subsequent failure occurs, replace the power supply with a temporary jumper (See item 6).
RESPONSIBILITY:
D.
Reed COMPLETE Department: I&C i
Tracking AR: A0249976, AE / 12
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9.
Determine with TES what failure analysis can be performed.
Continue ongoing failure analysis in order to establish the root cause of channel 942A failure.
l RESPONSIBILITY:
D.
Reed RETURN Department: I&C Tracking AR: A0249976, AE # 17
- 10. Implement a periodic inspection of channel 942 to determine if it is experiencing loss of capillary fill.
RESPONSIBILITY:
D.
Reed COMPLETE Department: I&C Tracking AR: A0249976, AE / 18 B.
Immediate Corrective Actions:
91NCR%7.91TINCM DPs Page 12 of 23
- ~.
P DC2-91-TI-N096 D8 January 25, 1993 1.
Channel 942A was returned to service.
2.
Daily monitoring of channel 942A was initiated by I&C.
This ronitoring was discontinued after transmitter and modifier replacement since the indication shifts were no longer occurring.
C.
Corrective Actions to Prevent Recurrence:
1.
STP I-1B will be revised to require that all CSF display screens of the SPDS be reviewed to identify problems with input channels.
This is a conservative' action to assure that problems with channels that send data to the SPDS are identified in a timely manner.
However, a review of all instrumentation in the control room which normally reads zero determined that only the reactor cavity wide range sump level channels would not be identified in a timely manner with instruments other than SPDS if the channel i
exhibits a zero shift.
In addition, information plaques were installed on the SPDS display panels describing the SPDS signals for a channel problem.
Since the procedure revision has been in effect, the 7 day action statement of TS 3.3.3.6 has not beer.
xceeded.
I RESPONSIBILITY:
D.
Reed COMPLETE Department: I&C Tracking AR: A0249976, AE # 03 Outage Related?:
NO 4
JCO Commitment?:
YES i
NCR Commitment?:
YES CMD Commitment?:
YES t
2.
A memo will be routed to all TRG chairmen describing this event and the importance of implementing adequate compensatory measures for an equipment problem which did not have an identified root cause.
RESPONSIBILITY: Jim Molden COMPLETE DEPARTMENT:
I&C 1
Tracking AR:
A0249976 AE #15 Outage Related?
NO 91NCRWP,91 TIN 0% DPs Page 13 of 23 l
l l
DC2-91-TI-N096 D8 January 25, 1993 JCO Related?
NO NRC Commitment?
YES CMD Commitment?
NO 3.
Additional training is being provided to operators to increase sensitivity to these indication shifts.
These corrective actions are believed to be sufficient to prevent exceeding the 7 day Action statement of TS 3.3.3.6.
l RESPONSIBILITY: John Becerro COMPLETE DEPARTMENT:
Training Tracking AR: A0249976, AE #16 Outage Related?
NO JCO Related?
NO NRC Commitment?
YES C'D Commitment?
NO 4.
LM-942A, LT-942A and the M1 cable from LT-942A to XLT-942A were replaced during the March 1992 forced outage; as these were the components most likely to be causing the indication shifts noted in the NCR.
Since these components were replaced, Channel 942A has not exhibited any further occurrences of the indication shift.
RESPONSIBILITY:
D.
Reed COMPLETE DEPARTMENT: I&C Tracking AR: A0261866 Outage Related?
YES JCO Related?
NO NRC Commitment?
YES CMD Commitment?
NO D.
Prudent Actions (not required for NCR closure):
1.
Submit a supplement to LER 2-91-010 providing the results of investigation into the problem.
I RESPONSIBILITY: Hug /Sisk COMPLETE Tracking AR: A0249976, AE # 04 i
Outage Related?:
NO JCO Commitment?:
NO NCR Commitment?:
YES CMD Commitment?:
NO 2.
Submit an INPO Nuclear Network inquiry requesting 1
9mene9rnwas ors Page 14 of 23 l
l
i DC2-91-TI-N096 D8 January 25, 1993 other plants with similar equipment that has had similar problems provide us their experience in resolving the problems.
RESPONSIBILITY:
D.
Reed COMPLETE Tracking AR: A0249976, AE # 05 Outage Related?:
NO JCO Commitment?:
NO NCR Commitment?:
NO CMD Commitment?:
NO t
VI.
Additional Information:
A.
Failed Components:
None.
i B.
Previous NCRs on Similar Problems:
i 1.
NCR DC2-89-TI-N016:
The events were similar in that both Unit 2 wide range containment reactor cavity sump level channels were declared inoperable.
However, the root cause of that NCR was a single event which rendered both channels inoperable simultaneously (undocumented removal of a seismic brace in panel RRM, which invalidated the seismic qualification of both channels).
The corrective actions for that NCR would not have prevented this event since the root causes are not related.
2.
NCR DC2-90-TI-N076:
The events were similar in that both Unit 2 wide 4
range containment reactor cavity sump level channels were determined to have been inoperable.
The root cause of the event was identified as normal component wearout.
The corrective actions to prevent recurrence were operator and I&C technician training explaining the meaning of the blue flashing path on the SPDS display.
This corrective action should have prevented the event that is the subject of this current NCR.
91NCRWi"91TINf.MDPs Page 15 of 23 i
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DC2-91-TI-N096 D8 January 25, 1993 C.
Operating Experience Review:
1.
Not Applicable.
2.
NRC IE Information Notices, Bulletins, Generic Letters:
None.
3.
None.
D.
Trend Code:
N/A, no root cause could be determined.
E.
Corrective Action Tracking:
The tracking action request is A0249976.
F.
Footnotes and Special Comments:
1.
As discussed in LER 2-91-010, investigative actions are continuing in an attempt to locate the cause of the indication shifts on channel 942A.
If a root cause is determined, the roo.t cause and applicable corrective actions will be reported in a revision to LER 2-91-010.
2.
The revision of STP I-1B provided an adequate compensating measure that alerts the operators to indication shifts in time to repair the channel and return it to service without exceeding the 7 day Action statement of TS 3.3.3.6.
G.
References:
1.
'NCR DC2-90-TI-N076 2.
Operator Statements dated 10/30/91 and 11/4/91 3.
Technical Specification 3.3.3.6.a 4.
Shift Foreman Logs dated 10/15/91 and 10/22/91 9mcawr9mmnuns Page 16 of 23
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DC2-91-TI-N096 D8 January 25, 1993 S.
Chart case 2-88 and 2-89 from 10/10/91 - 10/12/91 6.
SC 1-89 Rev. 2 7.
AR A0249483 8.
E-mail on Safety Analysis 9.
Operability Evaluation 91-12R0
- 10. Timeline H.
TRG Meeting Minutes:
1.
On October 31, 1991, the TRG convened and considered the following:
a.
The TRG discussed the recent history of channel 942A and the circumstances that led to the discovery of the channel being inoperable.
b.
The TRG discussed the failure of the previous event to prevent the recent event.
The TRG determined that STP I-1B should have been revised previously, and agreed that it will be revised as a result of this event.
I&C will review other control room indicators to determine if other I-1B checks shc ld be enhanced.
c.
The TRG discussed the cause of the channel shift.
I&C was not yet able to determine the root cause.
All available data on the channel has been forwarded to the vendor for review.
The vendor will be brought on site to perform additional investigation.
d.
The TRG will reconvene on 11/8/91 to discuss the root cause investigation.
2.
On November 8, 1991, the TRG reconvened and considered the following.
a.
The TRG reviewed the investigative actions.
It was determined that the containment reactor i
cavity sump wide range level channel are the 4
only channels that could fail low and not be 91NCRWP,91 TIN 04DPs Page 17 of 23
DC2-91-TI-N096 D8 January 25, 1993 easily identified except through SPDS.
b.
The TRG discussed the 1 My out of tolerance condition of channel 942A.
Regulatory Compliance was requested to determine if this affects the reportability of the event. (Note:
Since the scaling calculation was used to determine the acceptance criteria of the STP for re-calibration, and the STP is used to determine the operability of the channel, the channel was still inoperable.
Since the channel was inoperable, the event is still l
reportable.
However, the acceptance criteria could be expanded to the FSAR limit.)
The TRG will reconvene on December 10, 1991, to c.
discuss the results of the investigative actions.
3.
On December 10, 1991, the TRc reconvened and discussed the following:
a.
M. Nowlen chaired the meeting.
b.
D.J.
Reed reported that the root cause investigation was still ongoing.
No information was yet available from the vendor to assist in determining the root cause.
It was agreed that the TRG would reconvene on c.
12/20/91 to discuss the results to date of the root cause investigation.
4.
On December 20, 1991, at 10:00 am PST, the TRG reconvened in Room 327 of the administration building to discuss the progress of investigation into the problem.
The following items were discussed:
Arkansas Nuclear One apparently has equipment a.
similar to ours.
They will be contacted by D.
Reed to determine if they have had similar problems.
b.
Clinton apparently has had similar problems and Dennis Caswell is said to be aware of them.
D.
Reed will contact him.
91NCR%P.9mWEDPS Page 18 of 23 1
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'i DC2-91-TI-N096 D8 January 25, 1993 0
c.
The problem seems to be induced when troubleshooting has been performed and may be caused by a floating or improper ground.
There also may be a correlation to plant venting inducing the problem.
4 t
d.
A new activity will be added to the l
troubleshooting work order to do a point-to-point wiring inspection and comparison between channels to identify any differences.
A possibly related problem was identified by e.
Westinghouse about six months ago where silver 4
was migrating through the cases of transistors, forming an oxide on the case of the transistors i
and causing intermittent grounds on the card the transistors are on.
D.
Reed will l
investigate to determine if that phenomenon could be occurring here.
I f.
An INPO Nuclear Network inquiry should be made to determine if this problem has occurred anywhere else and had they fixed it.
g.
This NCR will remain open through 2RS to complete inspections and troubleshooting.
The TRG will reconvene if it is necessary.
5.
On February 25, 1992, at 10:00 am PST, the TRG reconvened in Room 327 of the administration building to review investigative actions.
A status of open action items was given as follows:
a.
Oconee (Duke Power) is the only other power plant that has the same CE system.
They never had the same problems we had, but they had so many other problems with the systems that they threw them away.
They have no spare parts to give or sell us, b.
A visual inspection was performed and a number of minor discrepancies were identified.
However, none were related to the DCPP problem.
c.
Voltage readings were taken on other channels for comparison and no significant differences were noted between the other 3 channels and 91NCRWI*91TINOM DPs Page 19 of 23 y-
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DC2-91-TI-N096 D8 January 25, 1993 2LM-942A.
d.
If nothing was found on the visual inspection, preparations were to be made to replace bin, modifier, and p/s in the cable spreading room.
This could not be done because there is no bin available for it.
e.
QA (Caswell) is contacting Clinton power plant to determine if " moisture trapped inside containment transmitters / corroded contacts" problem could be related to our failures.
f.
It was determined that " migrating silver" problem was not related to our problem.
g.
A jumper to hook recorders to 2LM-942A was developed and implemented.
All modifiers plus voltages to and from the transmitter are being watched.
h.
ECAD and CE are waiting for relief from 7 day /48 hr T.S.
for cable testing.
i.
The transmitter in the warehouse had a 50 ft.
cap fill attached to it.
j.
GC is in the process of determining the status of the existing Barton channels.
If the cable or transmitter is the problem, then a replacement plan for the channel will be developed.
k.
The "G" on DofC for the channel indicates that the "G" wire was spared out in the J-box near transmitter, not grounded.
The TRG was updated on the history of the channel since the time the last TRG convened.
Channel 942A has shifted low five times since the time of the last TRG on December 20, 1991.
A timeline has been included in the reference section to show the sequence of events.
The TRG learned that when the channel shifted on 2/24/92 the power was turned off and then back on and this brought the channel up to normal 91NCRWi"91 TIN 096 DPS Page 20 of 23
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DC2-91-TI-N096 DB January 25, 1993 conditions.
The TRG also learned that their might be some problems with SPDS.
It seems that question marks are not appearing on the screen when they are supposed to.
This will be investigated.
The TRG discussed more possibilities for root cause.
As a result AE #7 through AE # 11 were issued.
6.
On March 4, 1992, at 1300 PST, the TRG reconvened in Room 425 of the administration building to review investigative actions.
An NRC level 4,
NOV was received today on this event.
The NOV was discussed during this meeting.
A status of open action items was given as follows:
a.
A more complete report of the findings of the visual inspection will be provided by Dennis Reed.
b.
ECAD and CE will be brought on site for cable testing.
Dennis Reed will follow this task.
c.
Examination of the requirements to restore the old channels to service would require cap fills in the transmitter legs.
This could not be done at power.
d.
The TRG learned that when the channel shifted on 2/24/92, the power to the channel was left on.
Instead of pulling a fuse the external 4-20 ma loop was opened and closed.
This brought the channel up to normal conditions e.
The potential problems with SPDS will be covered outside this NCR.
See AR A0259647.
4 f.
The TRG noted that although there have been several problems since the one reported in LER 2-91-010-00, all of the subsequent problems were discovered and repaired within the time requirements of the Technical Specifications Action Statement, g.
The TRG noted that during investigative actions 91NCRWPi91 TIN (M.DPS Page 21 of 23 4
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4.
DC2-91-TI-N096 D8 January 25, 1993 performed February 24, 1992, following the determination and re-termination of leads, recorder indication for channel 942A was observed to more closely match channel 943's indication than any time in the recent past.
One theory of the change in channel 942A was that a high impedance connection may have been
- removed, h.
New investigative actions have been initiated.
If channel 942A shifts again:
1.
Check all eight external connections.
2.
Tighten and inspect crimps.
and 3.
Do a visual inspection of the ring lugs.
If a subsequent failure occurs, replace the power supply with a temporary jumper.
The TRG reconvened on March 25, 1992, to discuss corrective actions for the latest shift of containment wide range channel 942A.
The response to the NOV was reviewed and incorporated in the NCR.
The following corrective actions were added:
a.
A memo will be routed to all TRG chairmen describing this event and the importance of implementing adequate compensatory measures for an equipment problem which did not have an identified root cause.
b.
AP C-6S4 will be revised to specifically require compensating measures to ensure maximum availability of the equipment in question until the failure cause can be identified and corrected.
This corrective action was canceled by the TRG as being not needed.
Additional training is being provided to c.
operators to increase sensitivity to these failures.
These corrective actions are believed to be sufficient to prevent exceeding the 7 day Action statement of TS 3.3.3.6.
As discussed in LER 2-91-010, investigative actions are continuing in an attempt to locate the cause of the shifts on channel 942A.
If a root cause is determined for the channel 942A problems, the root cause und applicable corrective actions will be 4
91NCRw?*91 TIN 0% DPS Page 22 of 23 t
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DC2-91-TI-N096 D8 January 25, 1993 r
reported in a revision to LER 2-91-010.
The revision of STP I-1B provided an adequate compensating measure that alerts the operators to indication shifts in time to repair the channel and return it to service without exceeding the 7 day Action statement of TS 3.3.3.6.
This TRG will reconvene to review the revision to LER 2-91-010 on April 19, 1992.
The TRG reconvened on May 7, 1992, to review investigative actions.
Two new investigative actions were added.
1.
Determine with TES what failure analysis can be performed.
Continue ongoing failure analysis in order to establish the root cause of channel 942A failure.
'T 2.
Implement a periodic inspection of channel 942 to determine if it is experiencing loss of capillary fill.
I No root cause has been determined for the channel problems.
The NCR should stay open until the root cause is determined.
The transmitter was replaced.
The old contaminated transmitter was left in the RCA.
The TRG should reconvene on August 14, 1992, i
(AM) unless the root cause is determined before then.
7.
On August 14, 1992, at 10:00 am PDT in room 425 of the administration building the TRG reconvened to review the status of the NCR prior to final signature and presentation to the PSRC for their concurrence and NCR closure.
The TRG will reconvene on September 2, 1992 to sign the final NCR writeup.
ECD for this NCR is December 31, 1992.
8.
On September 1, 1992, the TRG reconvened in room 425 of the administration building at 2:00 pm PDT to discuss final corrections to the NCR writeup and sign the NCR.
I 91NCR%791 TIN 096.DPS Page 23 of 23 A
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