ML20059C831
| ML20059C831 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/19/1993 |
| From: | AFFILIATION NOT ASSIGNED |
| To: | |
| References | |
| OLA-2-I-MFP-098, OLA-2-I-MFP-98, NUDOCS 9401060122 | |
| Download: ML20059C831 (14) | |
Text
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NCR DC1-92-OP-N062.Rev.30 rp f 2 9 9J3 January 27, 1993
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REACTOR TRIP / BYPASS BREAKER SEISMIC CLIPS NOT INSTALLED I.
Plant Conditions Unit 1 was in Mode 1 (Power Operation) at 100% power.
II.
Description of Event A.
Summary:
On December 3, 1992, Instrument and Control personnel discovered that the Unit One Reactor Trip and Bypass breakers did not have the required seismic clips installed as required by plant operating and surveillance test procedures and Design Change Memorandum S-38A, " Plant Protection System."
A review of operating records indicates that the clips were not installed when the reactor trip and bypass breakers were made available for service on November 3,
- 1992, during unit restart from 1RS.
Both Reactor Trip Breakers were declared inoperable, and Tech Spec 3.0.3 was entered.
The seismic clips were properly installed within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, and Tech Spec 3.0.3 was exited with no further plant actions.
B.
Background:
The reactor trip and bypass breakers are provided with reactor trip ~b]which restrain the breakers so that the seismic clips reakers are secured in their fully racked in position and the bypass breakers are secured in their fully racked out position.
The primary purpose for these clips is to maintain breaker cell position during a seismic event to ensure that the features provided by the circuit breaker auxiliary switches and cell interlock switches function properly during and after the event.
The primary features of the auxiliary switches and cell interlock switches is to provide a main turbine trip and a P-4 interlock signal when the reactor trip breakers open.
The reactor trip function does not require the breakers to be seismically restrained.
DCM No. S-38A states that the restraints must be installed for the circuit breakers to be operable.
The clips are normally installed using operating procedure A-3:IV, " Manual Operation of Reactor Trip Breakers,"
92NCRWP\\920PN062.PSN Page 2
of 14 9401060122 930819 PDR ADOCK 05000275 O
1 NCR DC1-92-OP-N062 Rev. O I.
January 27, 1993 and installation is mentioned in STPs I-16Al and I-16A3, which remove and return a train of the Solid State Protection System from service for testing.
During these tests, the seismic clips are removed from both bypass breakers, then re-installed following those tests.
C.
Event
Description:
On October 27, 1992, with Unit one in Mode 5, I&C personnel performed STP I-16D2, " Actuation Logic Test of the Protection System Logic (Modes 5 or 6). "
As required by this test procedure, the Reactor Trip and Bypass Breakers were left in the " Racked Out" position.
The seismic clips were not installed on the Reactor l
Trip breakers, since the breakers must be racked in for
{
installatica, and were cpparently loc-ely installed on the bypass breakers at this time.
The system remained in this configuration until November 11, 1992, when Operations performed STP M-18 and STP M-22A.
The performance of STP M-18, " Functional Test of Turbine Trip from Reactor Trip," requires that all combinations of Reactor Trip and Bypass breaker configurations be tested.
The operator performing these tests noted that at the beginning of this test that both Reactor Trip Breakers and Both Bypass breakers were fully racked out.
The seismic clips were not installed on the trip breakers (they can only be installed if the breakers are fully racked in) and were loosely installed on the bypass breakers.
Since the operator's past experience was that the Instrument and Control Technicians installed and removed the seismic clips, he notified the Shift Foreman that the clips were installed on the bypass breakers and requested assistance from-I&C or clarification on how he was to proceed.
The Shift Foreman instructed the operator to remove the clips from the bypass breakers and perform the STP, and that he would make arrangements for I&C to install the clips following the test.
The shift foreman made an entry in his personal notepad as a reminder to contact I&C to arrange for the clips to be installed.
The Operator completed STP M-18, which left the system in the normal, at-power configuration (trip breakers racked in, bypa'm breakers racked out).
STP M-22A was i
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NCR DC1-92-OP-N062 Rev. O January 27, 1993 also performed, but it required no further manipulation of the reactor trip or bypass breakers.
The Shift Foreman and Licensed Operator were not concerned about the seismic clip installation since the trip breakers were not required at the time, and normal, at power testing routinely removed the seismic clips from both bypass breakers.
The note to request I&C to install i
the seismic clips was overlooked due to the normal Mode 4 preparation activity in the control room, and was forgotten.
The reactor trip breakers remained in their normal configuration without the seismic clips installed until December 3, 1992, when, prior to performing STP I-16A2B, it was noted by I&C personnel that the clips were not installed on either the bypass breakers or the reactor trip breakers.
Upon discovery, the I&C technicians notified their foreman, who notified the Shift Foreman.
Following review of the Design Criteria Memorandum, the i
Shift Foreman concluded that both reactor trip breakers were inoperable, and entered Tech Spec 3.0.3.
I&C and Operations personnel re-installed the braces on Reactor Trip Breaker A, and exited 3.0.3, declaring the Unit to l
be now in the 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> action statement associated with inoperable reactor trip breakers.
Approximately 10 i
minutes later, the seismic clips were re-installed in trip breaker B, and both reactor trip sistems were declared Operable.
STP I-16A2B was then completed as r
planned.
Based on the information contained in the Design Criteria Memorandum and discussion with the System Engineer and Operations Management, a 1 Hour Non-Emergency report was initiated in accordance with 10 CFR 50.72 (b) (1) (ii) (B), plant operation outside of j
design basis.
Subsequent review and discussions in the TRG regarding previous. evaluations indicate that the plant was not outside of its design basis.
The evaluations concluded that the reactor trip breakers would be able to perform their safety functions of tripping the reactor and generating a P-4 signal (ref. 3 and ref. 4).
D.
Inoperable Structures, Components, or Systems that Contributed to the Event:
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F NCR DC1-92-OP-N062 Rev. 0 January 27, 1993 None.
E.
Dates and Approximate Times for Major Occurrences:
1.
October 27, 1992 STP I-16D2 was completed by I&C personnel, all reactor trip and bypass breakers were left racked out in accordance with that procedure.
2.
November 11, 1992 STP M-18 was performed by Operations i
Personnel.
Seismic i
clips were noted to be not installed, but later plans to notify i
I&C maint. to correct i
the situation were overlooked.
3.
Dec.
3, 1992; 09:44 PST I&C personnel discovered that seismic clips were.not installed.
4.
Dec.
3, 1992, 10:10 PST Shift Foreman declared the unit in Tech Spec 3.0.3 due to both trip breaker trains being inoperat _' e.
5.
Dec.
3, 1992, 10:24 PST Tech Spec 3.0.3 was exited as clips were installed in trip breaker A.
6.
Dec.
3, 1992, 10:32 PST Both trip breaker trains declared operable with clips now installed in trip breaker B.
7.
Dec.
3, 1992, 10:36 PST A 1-hour non-emergency report was initiated to NRC in accordance with 92NCRWP\\920PN062.PSN Page 5
of 14
NCR DC1-92-OP-N062 Rev. O January 7,
1993 10 CFR 50.72 (b) (1) (ii) (B).
F.
Other Systems or Secondary Functions Affected:
i None.
G.
Method of Discovery:
The event was discovered by I&C personnel during the scheduled performance of STP I-16A2B.
H.
Operator Actions:
None.
I.
Safety System Responses:
None.
III.
Cause of the Event A.
Immediate Cause:
The immediate cause of the event is that the reactor trip breaker seismic clips were not installed during the start-up from 1RS.
B.
Determination of Cause:
1.
Human Factors:
a.
Communications:
Communications was a factor in this event since the request for I&C to install the seismic clips following the performance of STP M-18 was dropped by the Shift Foreman.
b.
Procedures:
Procedures contributed to this event since the operations procedures and engineering STPs did not clearly communicate the operability requirements associated with the reactor trip and bypass breaker seismic clips.
c.
Training:
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I NCR DC1-92-OP-N062 Rev. 0 January 27, 1993 1
Training contributed to this event since the plant operators did not clearly understand the requirements for the seismic clips in H reactor trip breakers.
I d.
Human Engineering:
No human engineering factors can be found that appear to be a causal factor to this event.
e.
Management System:
Management systems were a contributor since no procedure or other programmatic method existed to ensure that the reactor trip and bypass.
breakers were properly configured with the seismic clips installed during plant r_ art-up.
2.
Equipment / Material:
No equipment, material, or design issues have been found that contributed to this event.
C.
Root Cause:
The root cause of this event is a programmatic problem, in that no procedural or programmatic controls were in place to ensure that the reactor trip and bypass breakers were properly secured with seismic clips. prior to entering a mode where the trip breakers or the P-4 signal was required.
D.
Contributory Cause:
The contributory causes to this event were:
1.
Inadequate communication due to inattention by the operations shift foreman.
Following performance of STP M-18, the operator performing the test consulted with the shift foreman concerning the need to have ILC personnel install the seismic clips.
The shift foreman noted this item on his personal notepad, but, due to the high levels of activities associated with preparing the plant for a planned mode 2 entry, the note was overlooked and no requests to I&C were made, i
92NCRWP\\920PN062.PSN Page 7
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NCR DC1-92-OP-N062 Rev. O January 27, 1993 2.
Lack of knowledge by the licensed operations personnel concerning the operability requirements associated with the seismic clips.
The real requirements for the clips are to maintain reactor trip and bypass breaker positions to ensure that the P-4 function provided by the breaker auxiliary switches and cell interlock-switches will reliably function.
The operators felt the clips were more associated with operabil_ty of the trip breakers to provide a reactor trip function, so no urgency was felt to install the clips in mode 3, since the reactor trip system was otherwise disabled at this i
time.
3.
Unclear or inadequate information in the design change memorandum for the reactor trip breaker seismic clips.
The statement in the DCM infers that the clips are required for overall breaker operability, but does not provide any details associated with the P-4 interlock or other features associated with the breaker cell interlock or auxiliary switches.
l IV.
Analysis of the Event I
A.
Safety Analysis.
)
A safety analysis was performed by the reactor trip system vendor as a part of NCR DCO-88-EM-005, which was i
written following discovery that the seismic clips had I
not been installed on either unit since plant start-up.
The key points of this analysis are:
l 1.
The seismic clips are not required for the trip breaker system to perform the reactor trip l
function.
The reactor will trip (Control Rod drives would be de-energized) even if the reactor trip and bypass breakers fell completely from their cell during a seismic event.
i H
2.
Without the seismic clips, the system will perform i
its safety function of providing a P-4 signal and tripping the turbine.
If the breakers were not properly secured during a postulated seismic event, it is possible that the P-4 signal might prematurely be initiated, tripping the turbine before the reactor trips, but this would result in a reactor trip from a diverse portion of the 92NCRWP\\92OPN062.PSN Page 8
of 14 i
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i NCR DC1-92-OP-N062 Rev. 0 January 27, 1993 reactor protection system, and a turbine trip at power is a previously analyzed event.
The conclusions of the previous analysis were that no inoperable conditions existed, and this analysis clearly envelopes the existing event, so the conditions that existed had no impact on the health and safety of the public or plant workers.
B.
Reportability.
1.
Reviewed under QAP-15.B and determined to be non-conforming in accordance with Section 2.1.8 as a problem requiring a nonconformance by management direction.
2.
Reviewed under 10 CFr. 50.72 and 10 CFR 50.73 per NUREG 1022 and determined to be not reportable.
The 12/11/92 TRG determined that the operability of the reactor trip breakers was not affected by this event.
3.
Reviewed under 10 CFR Part 21 and determined that I
this problem will not require a 10 CFR 21 report, since it is being evaluated under 10 CFR 50.72/73.
This problem will not be reported via an INPO 4.
Nuclear Network entry.
Reviewed under 10 CFR 50.9 and determined to be not 5.
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:
1.
The seismic clips were properly installed on the Unit 1 Reactor Trip and Bypass breakers shortly following discovery of the problem.
2.
The Unit 2 Trip and Bypass breakers were inspected to ensure that all seismic clips were properly 92NCRWP\\920PN062.PSN Page 9
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NCR DC1-92-OP-N062 Rev. O January
_7, 1993 installed.
The inspection revealed no problems with these components on Unit 2.
B.
Investigative Actions:
None.
C.
Corrective Actions to Prevent Recurrence:
b 1.
Operating Procedures will be revised to ensure that the reactor trip breakers are properly configured prior to entering Mode 3.
RESPONSIBILITY:
J.
Skaggs ECD:
5/1/93 DEPARTMENT: Operations Engineering PGOE
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Tracking AR:
A0287511, AE #01 Outage Related? Yes OUTAGE: 2RS OE Related?
No NRC Commitment? No CMD Commitment? Yes 2.
An Operations Incident Summary will be issued for this event.
The incident summary will clarify the operability requirements associated with the reactor trip and bypass breaker seismic clips.
RESPONSIBILITY:
S.
Fridley ECD:
2/1/93 DEPARTMENT: Operations Management PGOM Tracking AR:
A0287511, AE #02 Outage Related? No OE Related?
No NRC Commitment? No CMD Commitment? No 5
3.
Revise DCM No. S-38A to clarify the requirements J
for the seismic clips in the reactor trip breakers.
RESPONSIBILITY:
J.
Hefler ECD:
5/1/93 j
DEPARTMENT:
NECS Engineering I&C NCEI Tracking AR:
A0287511, AE #03 Outage Related? No OE Related?
No NRC Commitment? No CMD Commitment? No D.
Prudent Actions (not required for NCR closure) 92NCRWP\\920PN062.PSN Page 10 of 14 4
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NCR DC1-92-OP-N062 Rev. 0 January 27, 1993 1
1.
An AT-EWR has been submitted to delete the seismic clips from the plant design, or if this is not i
possible, modify the clips so the design is more I
compatible with the operating requirements.
Tracking AR:
A0270554 VI.
Additional Information A.
Failed Components:
i None.
1 B.
Previous Similar Events:
NCR DCO-88-EM-N005 was initiated following discovery that the seismic clips had not been installed p_r i
design following initial plant start-up.
Corrective actions for this NCR included revising operating procedures to include seismic clip installation during routine testing.
This corrective action failed to prevent the present event since no actions were taken te ensure that the configuration was proper during i
subsequent plant start-ups (test procedures and requirements are different in Modes 5-6 from those in Modes 1-4).
See also the discussion in the 1/5/93 TRG meeting minutes below.
C.
Operating Experience Review:
1.
NPRDS:
Not applicable.
l 2.
NRC Information Notices, Bulletins, Generic Letters:
i
)
None.
l
~
A search of the NOS Operating Experience Assessment database under keywords BREAKER AND REACTOR TRIP AND SEISMIC ANALYSIS, and INSTALLATION AND SEISMIC SUPPORT revealed no applicable items.
}
3.
\\
3 None.
A search of the NOS Operating Experience Assessment database under keywords BREAKER AND REACTOR TRIP AND SEISMIC ANALYSIS, and INSTALLATION j
AND SEISMIC SUPPORT revealed no applicable items.
)
i j
92NCRWP\\920PN062.PSN Page 11 of 14 i
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NCR DC1-92-OP-N062 Rev. O January 27, 1993 D.
Trend Code:
Responsible department OP (Operations), and cause code A4 (Programmatic Deficiency).
I E.
Corrective Action Tracking:
1.
The tracking action request is A0287511.
2.
Are the corrective actions outage related?
Yes.
F.
Footnotes and Special Comments:
None.
G.
References:
1 Technical Specification 3.0.3 1.
Technical Specification 3.3.1 Action Request A0287386 2.
Action Request A0287444 3.
NCR DCO-88-EM-N005 Memorandum from NECS (M. Tresler) to DCPP (J.
Townsend) dated January 15, 1988, " Seismic Qualification of Reactor Trip Breakers" (CHRON106266)
Letter from Westinghouse (J. Hoebel) to PG&E (J. Shiffer) dated January 14, 1988, "DB-50 Switchgear Safety Evaluation" (CHRON106266, also CHRON106237)
Letter from Westinghouse (J. Hoebel) to PG&E 4.
(J. Shiffer) dated July 9, 1987, "FSAR Loss of External Electrical Load / Turbine Trip Event" (CHRON098830)
LER 1-87-010 (Voluntary)
Letter from Westinghouse Owners Group (J.
Triggiani) to Distribution dated March 6,
- 1989,
" Reactor Trip on Turbine Trip Position Statement (MUHP-1067)" (CHRON164312) 5.
Design Criteria Memorandum (DCM) S-38A, " Plant Protection System" i
6.
Prudent action AR A0270554 92NCRWP\\920PN062.PSN Page 12 of 14
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I NCR DCl-92-OP-N062 Rev. 0 January 27, 1993 I
H.
TRG Meeting Minutes:
On December 11, 1992, the initial TRG convened and considered the following:
1 1.
The TRG reviewed the event and a previous NCR and Westinghouse safety evaluation (ref. 3), which document the initial discovery in 1988 that we had not installed the seismic clips during construction /startup.
The evaluation concluded that the reactor trip breakers would be able to perform their safety functions of tripping the reactor and generating a P-4 signal.
Therefore, the breakers were always operable, we were never i
outside our design basis, and did not need to enter TS 3.0.3.
2.
As a result of the previous NCR, the normal at-power test procedure contained instructions to verify that the seismic clips were re-installed after monthly testing.
However, a different test procedure is used for testing in Modes 5 and 6, and this procedure did not ensure that the clips were in place prior to startup.
3.
Based on the previous Westinghouse evaluation, this event is not reportable and the TRG discussed potentially cancelling the NCR and tracking the 3
corrective actions with a QE.
The TRG agreed to reconvene approx. 12/16/92.
On December 18, 1992, the TRG reconvened and considered i
the following:
1.
This event will remain a nonconformance per management's direction.
Proposed root cause and l
corrective actions are provided above.
i 1
2.
The text of the 1988 Westinghouse evaluation notes that missing seismic clips will not prevent the breakers from performing their safety functions; however, relay chattering may cause an inadvertent turbine trip.
The letter noted that there was an ongoing evaluation of the potential for an inadvertent turbine trip (a Condition II event) to cause a Condition III Complete Loss of Flow event.
92NCRWP\\920PN062.PSN Page 13 of 14 i
NCR DCl-92-OP-N062 Rev. O January 2/,
1993 3.
The above concern may cause the TRG to re-evaluate reportability and whether the plant was outside its design basis.
The TRG agreed that NECS support would probably be required for the next TRG reconvene.
This TRG will reconvene on approximately 1/5/93.
(Subsequent to the 12/18/92 TRG, a 1989 letter from the Westinghouse Owners C-aup (WOG) was discovered, providing WoG's basis for concluding that a turbine trip without reactor trip is not a [ credible] design basis scenario (ref. 4).)
On January 5, 1993, the TRG reconvened and considered the following:
1.
The TRG discussed that there is no operability concern, and no reportability concern (reference NECS (M. Khan)'s response to A0287386, AE01).
2.
However, there is a cualification concern about i
removing the clips in the future.
The breakers were seismically qualified with the clips in place, so justification for removing them would require seismic re-evaluation and a submittal to the NRC.
5 3.
The TRG reviewed corrective actions taken as a result of the previous NCR.
They would not have i
prevented the current event, because the two events are actually different events with different causes.
The previous NCR dealt with the o"iginal installation and communication of design information being inadequate, whereas the current event is concerned with checking that the clips are reinstalled after routine testing.
4.
The TRG reviewed corrective actions and ECDs.
This TRG is not expected to reconvene, and the overall ECD for NCR closure is 6/1/93.
I.
Remarks:
None.
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