ML20059D142
| ML20059D142 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/21/1993 |
| From: | Shiffer J PACIFIC GAS & ELECTRIC CO. |
| To: | |
| References | |
| OLA-2-I-MFP-150, NUDOCS 9401070030 | |
| Download: ML20059D142 (6) | |
Text
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u,, p g;.nr it:ea W eGipra'r January 28, 1991 93 CCI 28 P5 51 PG&E Letter No. DCL-91-020 r q..),
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e U.S. Nuclear Regulatory Comission ATTN: Document Control Desk Washington, D.C.
20555
.4 Re:
Docket No. 50-275, OL-DPR-80 Diablo Canyon Unit 1 Licensee Event Report 1-90-019-00 Actuation of Containment Ventilation Isolation Due to Personnel Error Gentlemen:
Pursuant to 10 CFR 50.73(a)(2)(iv), PG&E is submitting the enclosed Licensee Event Report (LER) concerning an actuation of containment ventilation isolation (CVI) due to personnel error. A PG&E General Construction contract electrician caused a voltage transient on an inverter with a pair of pliers, thus causing the CVI.
This event has in no way affected the health and safety of the public.
Sincerely, f
t, o
. D. Shif cc:
A. P. Hodgdon J. B. Martin P. J. Morrill P. P. Narbut H. Rood NucttAn nicutnew couwS$'09 CPUC W1F^-($
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RECEIVED JAN 2 91991 LMM Corress. Control Center 9401070030 930021 PDR ADOCK 05000275 O
1 UCENSEE EVENT REPORT (LER) i x
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ACTUATION OF CONTAINMENT VENTILATION ISOLATION DUE TO PERSONNEL ERROR g
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On December 27, 1990, at 1431 PST, with Unit 1 in Mode 3 (Hot Standby), a-containment ventilation isolation (CVI) actuation occurred.
This event constitutes an Engineered Safety Feature actuation. The 4-hour, non-emergency report required by 10 CFR 50.72 (b)(2)(ii) was made to the NRC on December 27, 1990, at 1518 PST.
A contract electrician was performig design modifications in an energized radiation monitor cabinet. As the electrician removed the pliers from'the cabinet, the pliers came in contact with the terminals on a fuse block, causing a voltage transient on an inverter. The transient caused alarms on two radiation monitors supplied by the inverter, resulting in the CVI. The root cause was determined to be personnel error (cognitive) in that if the electrician had taped the tool in accordance with standard work practices for working in energized cabinets, electrical contact with the fuse block may not have occurred. A contributory cause was determined to be that a previously issued maintenance bulletin regarding work on energized equipment, which recommends taping tools, had not been reviewed with'the electrician.
To prevent recurrence of this event, all previous maintenance bulletins not distributed to General Construction (GC) will be distributed, tailboard meetings will be held with all GC crews to review previous maintenance bulletins relevant to this event, and the GC training will be revised to assure that maintenance bulletins are included.
51915/0085K i
UCENSEE EVENT REPORT (LER) TEXT CONTINUATION 164465 ner m tray o m u rr.= m err ca m DIABLO CANYON UNIT 1 0l5l0l0l0l2l7l5 90 0l1l9 0l0 2l"l5 f tsi 07)
I.
Plant Conditions Unit I was in Mode 3 (Hot Standby) at 0 percent power.
II.
Description of Event l
-A.
Event:
On December 27,1990, at 1431 PST, a containment ventilation isolation (CVI) actuation occurred on Unit 1.
This event constituted an Engineered Safety Feature actuation. The 4-hour, non-emergency report required by 10 CFR 50.72 was made to the NRC on December 27, 1990, at l
1518 PST.
While perfoming design modifications in a radiation monitor cabinet' in the control room, a Pacific Gas & Electric General Construction l
(GC) contract electrician was bending a smoke detector brace with a pair of pliers. The components in the cabinet remained energized during the work to maintain operability of other equipment.- As the electrician removed the pliers from the cabinet, the pliers came in contact with the terminals on a fuse block for Radiation Monitor (IL)(MON) RM-5, thus causing a voltage transient on inverter _ IY-llA (EF)(INVT). The transient spiked RM-ll and RM-12, causing a CVI signal.
Containment isolation valve FCV-681 closed. All equipment operated as expected.
B.
Inoperable Structures, Components, or Systems that Contributed to the Event None.
l C.
Dates and Approximate Times for Major Occurrences.
1.
Dec. 27, 1990; 14:31 PST:
Event / Discovery date. Inadvertent short to ground causes CVI.
2.
Dec. 27, 1990; 15:18 PST:
The 4-hour non-emergency report i
required by 10 CFR 50.72(b)(2)(ii) was made to the NRC.
D.
Other Systems or Secondary Functions Affected:
None.
51915/0085K
UCENSEE EVENT REPORT (LER) TEXT CONTINUATION
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DIABLO CANYON UNIT 1 0l5l0l0l0l2l7l5 90 0l1l9 0l0 3 l*'l - 5 T437 (17)
E.
Method of Discovery:
The event was immediately apparent to licensed plant operators due to alarms and indications received in the control room.
F.
Operators Actions:
After the operators determined that the CVI was due to.the inadvertent short to ground caused by work in the radiation monitor' cabinet and that no abnomal radiation levels existed, the operators reset the CVI logic and restored the containment ventilation system to its normal.
mode.
G.
Safety System Responses:
Containment isolation valve FCV-681 closed per design. All other valves that sould normally close under a CVI signal already were in the closed position.
FCV-691_ closed on low flow following closure of FCV-681.
III. Cause of the Event A.
Imediate Cause:
Voltage transient on actuation relays for RM-11 and RM-12 caused closure of containment isolation valves FCV-681 and 691.
B.
Root Cause:
Personnel error (cognitive).
During interviews with the electrician,:
it was determined that if the electrician had taped the tool irz accordance with standard work practices, electrical contact with the fuse block may not have occurred.
C.
Contributory Cause:
A previously issued maintenance bulletin regarding work on energized-equipment, which recommends taping tools, had not been reviewed with the electrician.
IV.
Analysis of the Event The voltage transient on the inverter resulted in a CVI actuation.
This actuation is conservative, regardless of plant conditions.. 'If an actual emergency had occurred during the event, the ventilation systems would have been ready to perform their accident prevention functions.
Therefore, the health and safety of the public were not adversely affected by this event.
51915/0085K
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION 164465
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V.
Corrective Actions A.
Immediate Corrective Actions:
All work was stopped to allow for investigation. Operators verified that there were no blown fuses, that the CVI was reset, and that FCV-681 and 691 were reopened.
Surveillance Test Procedure (STP) 1-100A, " Functional Test of Containment Air Radiogas Monitor RM-12 and Containment Air Particulate Monitor RM-II," was performed on RM-ll and RM-12 to verify operability.
B.
Corrective Actions to Prevent Recurrence:
1.
All previous maintenance bulletins which have not been Jistributed to GC will be distributed to them.
2.
Tailboard meetings will be held with all GC Electrical and I&C crews to review previous maintenance bulletins relevant to this event.
3.
The GC training will be revised to assure that maintenance bulletins are included.
VI.
Additional Information A.
Failed Components:
None.
B.
Previous LERs on Similar Events:
1.
LER l-87-021-00, LER 1-89-001-00, LER l-89-011-00, LER 2-90-004-00: The root causes of these CVI actuations were determined to be personnel error by Instrumentation & Controls (I&C) department personnel. The corrective actions were:
(1) additional training for I&C personnel; (2) a new I&C policy requiring de-energization of power circuits during work if feasible; (3) a maintenance bulletin to all technicians stating the need for caution when working on energized circuits; and (4) a design evaluation of a vendor's terminal strips. These corrective actions did not prevent the recent event because of the following reasons: (1) the recent event was caused by GC-Electrical personnel working on equipment that could not feasibly be de-energized; (2) the previous design evaluation of terminal strips was not applicable to this equipment; and (3) maintenance bulletins were not being distributed to GC personnel until after Maintenance Bulletin 007 was issued.
5191S/0085K l
l
UCENSEE EVENT REPORT (LER) TEXT CONTINUATION 164465,
aw, - m um -. m a.
-m; 0l1l9 0l0 5 l*'l 5 DIABLO CANYON UNIT 1 0l5l0l0l0l2l715 90 3w w>
2.
LER 1-88-007-00: The root cause of this CVI actuation was that quality checks were not performed as required by procedures.
Corrective actions focused on assuring completion of quality checks prior to re-energizing electrical circuits.
Since.the recent event occurred during work on energized circuits, the corrective actions did not prevent the recent event.
3.
As discussed in PG&E letter DCL-89-254, dated October 2, 1989,
' Noise Reduction Task Force Final Report regarding LER l-86-007-01, LER 1-86-014-01, LER l-86-015-01, and LER l-87-003-01," power transients affecting CVI-related radiation monitors have caused several CVIs.
Reducing CVIs caused by power transients is being addressed by several corrective actions:
(1) training to reduce power transients caused by human error, (2) adding CVI bypasr, switches to allow disabling of the CVI function during radiation monitor maintenance, and (3) initiating a Radiation Monitor System upgrade program to replace existing radiation monitors with equipment that is less sensitive to electrical. noise.
The time-delay circuitry modification already implemented reduces spurious CVIs caused by noise on the signal input; however, the output relays of the monitors are still sensitive to transients on their power supply (such as in the recent event).
C.
Remarks GC personnel are trained on Maintenance Department administrative and work procedures and perform work in accordance with those procedures.
PG&E feels that no formal procedure regarding work on energized equipment is needed, as precautions against energized equipment are comon knowledge to journeyman electricians, and maintenance bulletins are adequate to dissemir" e additional guidance.
51915/0085K