05000327/LER-1993-019
| ML20056D778 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/11/1993 |
| From: | Fenech R, Meade K TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-93-019, LER-93-19, NUDOCS 9308180015 | |
| Download: ML20056D778 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| 3272093019R00 - NRC Website | |
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A 7ennessee we, Aat,cynv Nu 0%e b m r,:mayh., Tearcsee 37m n00 Robert A Fenech W e hesrdom seanan u.a +ar Nn' August 11, 1993 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:
TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO. 50-327 - FACILITY OPERATING LICENSE DPR LICENSEE EVENT REPORT (LER) 50-327/93019 The enclosed LER provides details concerning the closure of containment isolation valves, resulting from a loss of nonessential control air.
This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv) as an event that resulted in the actuation of an engineered safety feature.
Sincerely,
, h4f k'- '-e A-.-
Robert A. Fenech Enclosure ec: See page 2 1791.0 9308180015 930811 i~~'
PDR S
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4 U.S. Nuclear Regulatory Commission Page 2 August 11, 1993 cc (Enclosure):
INPO Records Center Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, Georgia 30339-5957 Mr. D. E. LaBarge, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Fockville Pike Rockville, Maryland 20852-2739 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379-3624 Regional Administrrcor U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, IAJ, Suite 2900 Atlanta, Georgia 30323-2711 1
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NRC fonn 366 U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (6-09T Expires 4/30/92 I LICD(SEE EVENT REFT)RT (LER)
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_ _191 _ Jkj _l20.402(b) l_l20.405(c) lMl50.73(a)(2)(iv) l_l73.71(b)
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__{l01j0]Dj L L l20.405(a)(1)(iii) Ll50.73(a)(2)(i) l__l50.73(a)(2)(viii)(A) l Abstract below and in i l_l20.405(a)(1)(iv) L_]50.73(a)(2)(ii) Lj50.73(a)(2)(viii)(D) l Text, NRC form 366A) l_120J05Lalilliv ) 1 IM,Hia1L2111111 I IMJ3(a)(2)(x) _.1 LICIHSifl DNTACT FOR THISl LR (12)
NAME l TELE @NE_NUMRER lAREACODEl .
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__LIELillam_mplet elXlLCIEQ_SUEMIS110!LDA_1[1 l X l N0 l DATE (15) l I l_j_} l ABSTRACT (Limit to 1400 spaces, i.e., approximately fifteen single-space typewritten lines) (16)
On July 13, 1993, at 1256 Eastern daylight time, the A and B nonessential control air headers were both isolated during implementation of clearance tagging. Clearance tagging was being performed to facilitate scheduled piping modifications on the nonessential control air system. Both headers were inadvertently isolated as a result of an inaccurate drawing that was used to develop the clearance boundary. The drawing continuation flag that provides the continuation reference from one drawing to another incorrectly referenced the wrong location. Nonessential air components, including some containment isolation valves, isolated. Control air was supplied to the components required to operate to ensure safe shutdown or to mitigate the consequences of an accident. Operations personnel quickly determined the cause for the loss of nonessential air, dispatched an operator to reopen some of the closed valves, and restored system air pressure. It was determined that the cause for the drawing error was personnel error. Similar systems were walked down to verify drawing continuation flags. No other drawing continuation flag errors were identified. The drawing error has been corrected.
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NRC Intm Df,(fr 89) l
NRC form 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 31EO-0104 (6-891 Expires 4/30/92 LICENSEE EVENT REPORT (LER)
, TEXT CONTINUATION ;
l FACILITY NAME (1) lDOCKETNUMBER(2)} LER NUMJER (6) l l PAGE (3? :
l l l lSEQUENTIAtl l REVISION] l l l l l Sequoyah Nuclear Plant (SQN), Unit 1 l 1YEARl i NUMBER I lNutg1R_j l l l l Ids 1 Main 13_JLJ71913 I-I O I i I 9 l--I O I O_1_n1_21off_1)I 4 TEXT (If more space is required, use additional NRC Form 366A's) (17) '
I. PIANT CONDITIONS ,
Unit I was in Mode 6 for a refueling outage. ;
II. DESCRIPTION OF EVENT A. Event On July 13, 1993, at 1256 Eastern daylight time (EDT), the A and B nonessential control air headers (EIIS Code LF) were both inadvertently isolated during implementation of clearance tagging. Clearance tagging was being performed to facilitate scheduled piping modifications on the nonessential control air '
! system. Both headers were isolated as a result of an inaccurate drawing that was used to develop the clearance boundary. This error resulted in identification and isolation of the end device valves on one header and the !
J supply isolation valve on the other header, effectively . isolating both A and B ;
nonessential control air headers during clearance tagging. Nonessential air components, including some containment isolation valves (EIIS Code JM),
isolated. Control air was supplied to the components required to operate to
. ensure safe shutdown or to mitigate the consequences of an accident.
Operations personnel quickly determined the cause for the loss of nonessential ;
air, dispatched an operator to reopen some of the closed valves, and restored ;
system air pressure.
B. InoneI_able_fitInclurm_Comprnenta, or SyJLtems_Ihat_ Contributed _to_the_ Event None.
C. Daln_aniAppr.oximate_IimetrI_ Major occurrences July 13, 1993 Operations personnel were in the process of tagging and !
a at 1000 EDT isolating a nonessential control air header to support a '
preplanned piping modification.
a July 13, 1993 The main control room operators began receiving numerous at 1256 EDT alarms.
July 13, 1993 The unit operator realized that the alarms and valve at 1258 EDT closures were a result of a problem with the air system.
The control room crew entered the appropriate procedure.
The tagging AUOs were contacted and instructed to return the last three isolated valves to their normal position.
July 13, 1993 System air pressure and affected equipment were returned l
at 1314 EDT to normal.
NRC f orm 3%(f-89)
NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No 3150-0104
,(6-897 Empires 4/30/92 ,
LICENSEE EVENT REPORT (LER) [
, TEXT CONTINUATION !
1 FACILITY NAME (1) lDOCKETNUMBER(2)} LER_tG_MBER (6) l l PAGE (3) ;
I l l l l$EQUENTIALl lREV?SIONl l l l l [
Sequoyah Nuclear Plant (SQN). Unit 1 l lYEAR l l NUMBER l I NUME[ d l l l l ;
laj51010lDlLlLlL19131-101 1 I 9 l-l 01 0 l Qj J 0Fl 01 4 ;
lEXT (If more space is required, use additional NRC Form 366A's) (17)
)
D. Ot h e r_Syal_em s_p r_Eerondary_Eunc_ tion slfiertsd
)
The drop in nonessential control air pressure caused the essential control air system to automatically isolate from the nonessential portion, and the auxiliary air system compressors started.
The air-operated containment isolation valves for the upper and lower containment radiation monitors, as well as various valves on the glycol portion ,
of the ice condenser system, traveled closed as a result of the loss of air. !
E. Methodaf_ Discovery The condition was annunciated on the main control room panels.
. F. Operator _ Action
! 1he main control room operators immediately entered the appropriate abnormal operating instruction, determined that the condition was the result of i clearance implementation, and took the appropriate steps to restore the nonessential control air system.
G. SafRty_Systen1_BESPORSeR Containment isolation valves failed to their associated loss of air position.
The auxiliary control air system compressors started as required. The main i control room received a train B auxiliary control pressure low alarm.
- Investigation of the alarm determined that the compressor did start and was .
running. Troubleshooting of the equipment determined that the compressor did i j load; however, a valve to the vent muffler failed open. !
III. CAUSE OF EVENT q
A. Immediatel ause i I
1 The closure of the containment isolation valves was the result of a loss of l nonessential control air pressure. ,
4 B. Boog_Cause The root cause was determined to be personnel error during a drawing revision j in 1977, resulting in the drawing continuation flags being swapped for the A i and B headers. This error resulted in identification and isolation of the end device valves on one header and the supply isolation valve on the other header, ,
effectively isolating both A and B nonessential control air headers during clearance tagging. i s !
i I t'm )( 69) i
NRC Fonn 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104
,f6-891 Expires 4/30/92 LICEN3EE EVENT REPORT (LER)
, TEXT CONTINUATION j FACILITY NAME (1) lDOCKETNUMBER(2) I LG_tALMM_R (6) l l PAJE (3) l l l l5EQUENTIALl l REVISION l l l l l Sequoyah Nuclear Plant (SQN), Unit 1 l lYEAR I I NWMBJR I INUt1}fR_j l l l l 1015J0101011171719 IM-10 I i_LO-l 01 0 1 01 dimJ 01 4 1 EXT (If more space is required, use additional NRC Form 366A's) (17)
V. Contrihuting_F3.ctots None.
IV. ANALYSIS OF THE EVENT Operability of safety-related components required for safe shutdown and accident mitigation were not affected by this event. The automatic isolation of the essential control air system performed as required, and nonessential air-suppplied )
components failed to their associated loss of air position. Containment isolation valves failed, as designed on a loss of control air, to their safety-related position. Therefore, this event did not adversely affect the health and safety of the plant personnel or the general public.
V. CORRECTIVE ACTION A. Immediate__COIrec.tive_Actinn Operators evaluated the condition and returned the appropriate valves to their normal positions and system air pressure was restored. Tagging operations were stopped until the drawings could be verified correct or were verified physically before isolation. The remaining valves on the affected clearance were untagged and returned to normal.
B. Aclivn_to_frevent_Re_currsnce Walkdowns were performed of drawing continuation flags on the nonessential control air system, service air system, raw cooling water system, high pressure fire protection system, and portions of the raw service water system. No other continuation flag errors were identified.
The affected drawing has been corrected in order to resolve the subject discrepancy.
VI. ADDITIONAL INFORMATION A. FaileLComponenta None.
B. Erev_inus_SimilarlXents There were no previous reportable events associated with clearance tagging implementation problems as the result of drawing errors.
VII. COMMIIMENTS None.
iMEfoim'M5if--89)
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