ML20029C936
| ML20029C936 | |
| Person / Time | |
|---|---|
| Site: | Hatch, Grand Gulf, Cooper, Pilgrim, Vermont Yankee, FitzPatrick File:NorthStar Vermont Yankee icon.png |
| Issue date: | 04/06/1994 |
| From: | Chaffee A Office of Nuclear Reactor Regulation |
| To: | Grimes B Office of Nuclear Reactor Regulation |
| References | |
| OREM-94-012, OREM-94-12, NUDOCS 9405030048 | |
| Download: ML20029C936 (15) | |
Text
4 Apri 6l 1994 MEMORANDUM FOR:
Brian K.
Grimes, Director Division of Operating Reactor Support FROM:
Alfred E.
Chaffee, Chief Events Assessment Branch Division of Operating Reactor Support
SUBJECT:
OPERATING REACTORS EVENTS BRIEFING MARCH 30, 1994 - BRIEFING 94-12 On March 30, 1994, we conducted an Operating Reactors Events Briefing (94-12) to inform senior managers from offices of the Commission, AEOD, RES, EDO, OE, NRR, and regional offices of selected events that occurred since our last briefing on March 23, 1994. lists the attendees.
presents the significant elements of the discussed events.
There were no scrams reported for the week ending March 27, 1994.
No significant events were identified for input into the NRC Performance Indicator Program.
Robert L. Dennig
/for/ Alfred E.
Chaffee, Chief Events Assessment Branch Division of Operating Reactor Support
Enclosures:
As stated cc w/ enclosures:
See next page DISTRIBUTION:
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D. Matthews (PDII-3)
F. Gillespie, NRR (12G18)
Acting ADPR, NRR (12G18)
S.
Varga, NRR (14E4)
J.
Calvo, NRR (14A4)
G.
Lainas, NRR (14H3)
J.
Roe, NRR (13E4)
J.
Zwolinski, NRR (13H24)
E. Adensam, NRR (13E4)
A. Thadani, NRR (12G18)
B.
Sheron, NRR (7D26)
M.
Virgilio, NRR (8E2)
S.
Rosenberg, NRR (10E4)
C.
Rossi, NRR (9A2)
B.
Boger, NRR (10H3)
F.
Congel, NRR (10E2)
D.
Crutchfield, NRR (11H21)
W.
Travers, NRR (11B19)
D.
Coe, ACRS (P-315)
E.
Jordan, AEOD (MN-3701)
G.
Holahan, AEOD (MN-9112)
L.
Spessard, AEOD (MN-3701)
K.
Brockman, AEOD (MN-3206)
S. Rubin, AEOD (MN-5219)
M.
Harper, AEOD (MN-9112)
W.
Bateman, EDO (17G21)
F.
Ingram, PA (2G5)
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A.
Bates, SECY (16G15)
T. Martin, Region I R.
Cooper, Region I S.
Ebneter, Region II J.
Johnson, Region II S.
Vias, Region II J. Martin, Region III E. Greenman, Region III L.
Callan, Region IV A.
Beach, Region IV X.
Perkins, Region IV/WCFO bec:
Mr. Sam Newton, Manager Events Analysis Department Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339-5957 I
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April 6, 1994 MEMORANDUM FOR:
Brian K.
Grimes, Director Division of Operating Reactor Support FROM:
Alfred E.
Chaffee, Chief Events Assessment Branch Division of Operating Reactor Support
SUBJECT:
OPERATING REACTORS EVENTS BRIEFING MARCH 30, 1994 - BRIEFING 94-12 On March 30, 1994, we conducted an Operating Reactors Events Briefing (94-12) to inform senior managers from offices of the Commission, AEOD, RES, EDO, OE, NRR, and regional offices of selected events that occurred since our last briefing on March 23, 1994. lists the attendees.
presents the significant elements of the discussed events.
There were no scrams reported for the week ending March 27, 1994.
No significant events were identified for input into the NRC Performance Indicator Program.
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v Alfred E.
- Chaffee, lig G f
Events Assessment raw Division of Operating'ph' Reactor Support
Enclosures:
As stated cc w/ enclosures:
See next page
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't ENCLOSURE 1 LIST OF ATTENDEES OPERATING REACTORS EVENTS FULL BRIEFING (94-12) l MARCH 30, 1994 l%!ig QFFICE NAME OFFICE A. CHAFFEE NRR T.
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ROSSI NRR 1
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SKEEN Niu; D. MATTHEWS NRR K. GRAY NRR R. JONES-NRR
. E. BENNER URR J.
DEAN OEDO D. WHEELER NRR G.
BURDICK RES S. ROSENBERG NRR M. RUBIN OCM/IS W.
BECKNER NRR J. ROSENTHAL AEOD G.
REPLOGLE NRR TELEPHONE ATTENDANCE (AT ROLL CALL)
Reaions Resident Inspectors
- Region I Hatch Region II Region III Region IV 1
Region V IIT/AIT Team Leaders Misc.
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OPERATING REACTORS EVENTS. BRIEFING 94-12 LOCATION:
10 Bil, WHITE FLINT WEDNESDAY, MARCH 30, 1994 11:00 A.M.
HATCH, UNIT 2 LOSS OF SHUTDOWN COOLING 1
1 VARIOUS BWRs LOSS OF SHUTDOWN C00 LING'DUE TO PRESSURE TRANSIENTS l]
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' PRESENTED BY:
EVENTS ASSESSMENT BRANCH DIVISION OF;0PERATING REACTOR SUPPORT,'NRR.
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HATCH, UNIT 2 LOSS 0F SHUTDOWN COOLING
. MARCH 17, 1994 PROBLEM THE RESIDUAL HEAT REMOVAL (RHR) INJECTION VALVE CLOSED AND CAUSED'AN INITIALLY UNKNOWN LOSS OF ALL FORCED CIRCULATION THROUGH THE REACTOR VESSEL.
CAUSE AN ENGINEER, WHILE PREPARING FOR UPCOMING MAINTENANCE LIFTED A WIRE BUNDLE IN A CONTROL PANEL-AND OBSERVED-ARCING AT A RELAY.
A BLOWN FUSE-IN A PRIMARY CONTAINMENT.
ISOLATION CIRCUIT CAUSED THE DISCHARGE VALVE IN THE ONE OPERATING RHR LOOP TO CLOSE.
SAFETY SIGNIFICANCE DURING A REACTOR SHUTDOWN WITH A TIME (H: HIGH DECAY. HEAT, THE REACTOR VESSEL LOST SHUTDOWN COOLING AND BECAME PRESSURIZED.
MAINTAINING THE CAPABILITY T0 REMOVE' DECAY H
HEAT DURING REACTOR SHUTDOWN REQUIRED.0PERATOR DETECTION OF DEGRADED PLANT CONDITIONS FOLLOWED BY A NUMBER OF CORRECTIVE ACTIONS.
DESCRIPTION OF EVENT.
REACTOR WAS IN COLD SHUTDOWN; REACTOR HAD BEEN' SHUTDOWN' ABOUT 30 HRS.
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1 CONTACT:
J. CARTER, NRR/ DORS /EAB AIT:
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REFERENCE:
10 CFR 50.72 #26952 SIGEVENT: TBD i
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<LHATCH, UNIT 2 2-94-12 ci LOOP A 0F RHR WAS SHUTDOWN BUT AVAILABLE.
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ALL OTHER LOW PRESSURE CORE COOLING SYSTEMS WERE OPERABLE 1
HEAD VENT WAS OPEN; HEAD VENT IS FOR VENTING NON-CONDENSIBLE GASES.
q REACTOR VESSEL HEAD BOLTS REMAINED TENSIONED.
DRYWELL HEAD HAD BEEN REMOVED.
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IN PREPARATION FOR UPCOMING REPLACEMENT OF RELAYS, AN ENGINEER WAS VERIFYING THE WIRING IN A PANEL.
Mr ARCING'WAS OBSERVED AND PROMPTLY REPORTED TO THE OPERATORS; SUBSEQUENTLY DETERMINED TO HAVE RESULTED IN-A BLOWN FUSE THAT INITIATED CLOSURE OF ISOLATION VALVES 0 11:31-HRS.
o OPERATORS CHECKED PLANT STATUS AFTER BEING TOLD OF ARCING.
o ATTEMPTED TO OPEN THE RHR DISCHARGE VALVE @ 11:41 WHICH WAS FOUND-CLOSED.
ATTEMPTED T0 RESET. ISOLATION SIGNAL.
VALVE WENT OPEN, THEN CYCLED CLOSED.
o INCREASED REACTOR VESSEL: WATER LEVEL-@ 11:45 TO ASSURE l
NATURAL CIRCULATION.
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,7: HATCH, UNIT 2 94-12 o- '0PERATORS OBSERVED: INLET TEMPERATURE TO REACTOR WATER-CLEANUP SYSTEM WAS INCREASING.
REACTOR PRESSURE WAS INCREASING, BUT NOT OBSERVED-BY OPERATORS MONITORING CONTROL ROOM INDICATORS (0-1200 PSI RANGE).
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BEGAN PREPARATIONS TO GET-RHR LOOP A INTO OPERATION.
PLACED RHR LOOP A INTO OPERATION 0 12:55 HRS o
HEAT EXCHANGER IN RHR LOOP A PLACED IN SERVICE AND TEMPERATURE IN RWCU INLET LINE WAS OBSERVED TO HAVE PEAKED AT ABOUT 195 F 0 12:55 HRS.
o A BLOWN FUSE WAS REPLACED AND RHR DISCHARGE VALVE 15B RESET; LOOP B OPERABLE 0 13:25 HRS.
o AT ABOUT 14:00 HRS A FLANGED INSTRUMENT CONNECTION WAS-LOOSENED AND A PLUME OF STEAM WAS OBSERVED.
o ANOTHER LOSS OF SHUTDOWN COOLING WITH THE SAME l
INITIATING EVENT OCCURRED IN APRIL 1993; MINIMAL DECAY LOAD DURING THAT EVENT.
-F0LLOWUP o
A REVIEW 0F THE COMPUTER RECORDS DISCLOSED THAT ONE PRESSURE INSTRUMENT-(0-1200 PSIG) INDICATED THAT A PRESSURE OF ABOUT 9 PSIG MAY HAVE OCCURRED; COMPUTER-SYSTEM HAD GREATER SENSITIVITY.
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HATCH, UNIT-2 94-12 o
. GENERAL' ELECTRIC ISSUED SIL 357, JUNE 1981, " CONTROL OF REACTOR VESSEL TEMPERATURE / PRESSURE DURING SHUTDOWN."'
DISCUSSED THERMAL STRATIFICATION AND-SURFACE TEMPERATURES AB0VE 212 F.
DISCUSSED POTENTIAL FOR SURFACE TEMPERATURES AB0VE 212 F AND STEAMING.
- o GENERAL ELECTRIC WAS ASKED TO EVALUATE THE EVENT.
ESTIMATED A PRESSURE OF BETWEEN 5 AND 8 PSIG-C0dLD HAVE BEEN PRESENT.
THE AVERAGE COOLANT TEMPERATURE WAS ESTIMATED TO.
HAVE BEEN A' MAXIMUM OF 210 F;-PER TECHNICAL SPECIFICATIONS MODE CHANGES AT 212 F.
o REACTOR VESSEL METAL TEMPERATURE NEAR AREA 0F.FEEDWATER N0ZZLE WAS-215 F..
o REACTOR. CAVITY HAS BEEN FLOODED AND CONNECTED TO THE SPENT FUEL P0OL BY 14:00 ON MARCH 19.
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A PREVIOUS MODIFICATION OF THE VENT PIPING RESULTED.IN ABOUT A 1 FT LONG.SECTION OF THE 100 FT OF VENT PIPING q
BEING ONLY 1/2"; THE REST OF-THE PIPING IS.A NOMINAL 2" a
DIAMETER.
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THE RESIDENT STAFF IS PERFORMING A SPECIAL INSPECTION ~
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.AND" PLANS TO ISSUE'A SPECIAL' INSPECTION REPORT.
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RESIDENT INSPECTORS AND. PROJECT MANAGER ARE PLANNING 1R)
EVALUATE ANY LICENSEE SUBMITTAL, ANALYSIS'BY GENERAL ELECTRIC.
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y 94-12 j
VARIOUS BWRs-LOSS OF-SHUTDOWN COOLING H
DUE TO PRESSURE TRANSIENTS ~
umss PRESSURE TRANSIENTS (IN SOME CASES, WATER HAMMER) IN THE SHUTDOWN COOLING PIPING HAVE CAUSED SHORT DURATION LOSSES OF SHUTDOWN COOLING.
CAUSE CLEARING OR COLLAPSE OF AIR OR STEAM VOIDS IN THE SHUTDOWN COOLING PIPING CAUSE THE PRESSURE SWITCHES' PROTECTING THIS LOW-PRESSURE PIPING TO SENSE A HIGH PRESSURE ISOLATION LCONDITION.-
SAFETY SIGNIFICANCE-POTENTIAL DAMAGE T0. SAFETY-RELATED EQUIPMENT DUE TO WATER HAMMER.
DISCUSSION o
COOPER:
e ON MARCH 17, 1994, THE PLANT LOST SHUTDOWN COOLING FOR 13 MINUTES.
TEMPERATURE INCREASED FROM 184*F
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TO 189*F.
VESSEL LEVEL DECREASED.7 INCHES.
c CONTACT:
N. HUNEMULLER,,NRR/ DORS.
AIT:-HQ_
REFERENCE:
50.72 #26953, PNO-IV-94-006
~SIGEVENT: NO
.LER 50-271/93-018 50.72 #25822, LER 50-293/93-019 50.72 #25534, I.R.'s 50-333/93-17 & 93-28 j
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VARIOUS.BWRs 94-12 c
at SHUTDOWN COOLING HAD BEEN INITIATED 2 1/2 HOURS EARLIER.
THE HEAD VENTS HAD BEEN OPENED 44 MINUTES EARLIER WHEN TEMPERATURE HAD BEEN REDUCED BELOW.
200*F.
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e THE COLLAPSE OF A VOID IN THE RHR OR REACTOR j
RECIRCULATION PIPING WAS IDENTIFIED AS:THE MOST i
PROBABLE CAUSE.
o VERMONT YANKEE e
ON DECEMBER 17, 1993, A SHUTDOWN COOLING. ISOLATION OCCURRED.WHILE ATTEMPTING TO START AN RHR PUMP.
WHEN THE-INJECTION VALVE WAS THROTTLED 0 PEN ~ VESSEL LEVEL DECREASED 3 INCHES.
SHUTDOWN COOLING WAS ESTABLISHED WITH THE SAME RHR PUMP 13 MINUTES LATER j
AFTER REFLUSHING.
e THE APPARENT CAUSE OF THE EVENT WAS THE PRESENCELOF q
AIR OR STEAM VOIDS IN THE-SHUTDOWN: COOLING LOOP WHICH PRODUCED PRESSURE SURGES IN THE SYSTEM.
o PILGRIM j
e ON JULY 22, 1993, A SHUTDOWN COOLING. ISOLATION OCCURRED WHEN AN RHR PUMP WAS. STARTED ANDLTHE.
INJECTION VALVE WAS OPENED T0. INITIATE SHUTDOWN-1 COOLING FLOW..
SHUTDOWN COOLING WAS SUCCESSFULLYJ REINITIATEDLTWO MINUTESLLATER.
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.THE CAUSE WASLDETERMINED TO BE A-MOMENTARY PRESSURE TRANSIENT THAT-ACTUATED THE PROTECTIVE HIGH-PRESSURE SWITCHES.
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,.VARIOUS~BWRs 3-94 -
co FITZPATRICK e
ON FEBRUARY 25, MARCH 11, AND MAY 19, 1993, SHUTDOWN COOLING ISOLATIONS OCCURRED WHILE ATTEMPTING TO PLACE SHUTDOWN COOLING IN SERVICE.
ON ALL THREE OCCASIONS, SHUTDOWN COOLING WAS SUCCESSFULLY ESTABLISHED ON THE SECOND ATTEMPT.
DURING THE SECOND ATTEMPT ON MAY 19, 1993, TEN MINUTES AFTER THE-FIRST ATTEMPT, REACTOR WATER j
LEVEL DECREASED 17 INCHES.
THIS WAS ATTRIBUTED TO THE MOVEMENT OF WATER FROM THE DOWNCOMER REGION, WHERE LEVEL IS MONITORED, T0'THE MOISTURE u
SEPARATORS UPON PUMP START.
THE LICENSEE'S ENGINEERING REVIEW ~ CONCLUDED THAT.
l THE ROOT CAUSE OF THE ISOLATION SIGNALS WAS-TRAPPED l
AIR IN THE INSTRUMENT TUBING FOR ONE OF THE--
1 PROTECTIVE PRESSURE SWITCHES.
THE IMMEDIATE-CORRECTIVE ACTION WAS TO ENSURE THE SENSING LINE WAS PROPERLY VENTED AND-BACK-FILLED PRIOR T0 PLACING SHUTDOWN COOLING IN SERVICE.
LONG-TERM-CORRECTIVE ACTION WILL BE'TO RE-ROUTE THE SENSING LINE TO ELIMINATE THE AIR TRAP.
PREVIOUS SIMILAR EVENTS
.o ON APRIL 20, 1992, JULY, 29, 1991,.AND MARCH 14, 1991, COOPER, GRAND GULF AND VERMONT YANKEE, RESPECTIVELY, EXPERIENCED SIMILAR EVENTS.
DEFICIENCIES IN THE SHUTDOWN COOLING WARMING PROCEDURES WERE IDENTIFIED'FOR ALL THREE EVENTS.
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.VARIOUS BWRs 4-94-12 o
IN JUNE-1976, G.E. ISSUED SIL NO. 175 BECAUSE SEVERAL BWRs HAD EXPERIENCED WATER HAMMER IN THE RHR/ RECIRCULATION PIPING DURING PRIMARY SYSTEM C00LDOWN, IN PREPARING FOR OR WHILE IN THE SHUTDOWN COOLING MODE.
NO DAMAGE WAS IDENTIFIED, HOWEVER, THE SIL DISCUSSED THE PROBABLE CAUSES AND RECOMMENDED CORRECTIVE ACTIONS.
AIR VOIDS CAN FORM DURING DRAINING, FLUSHING OR-FILLING OF THE PIPING.
STEAM VOIDS CAN BE CREATED ANYTIME THE WATER PRESSURE IS ALLOWED TO FALL BELOW THE SATURATION PRESSURE.
AIR OR STEAM VOIDS CAN ACCUMULATE IN THE SHUTDOWN COOLING PIPING ANYWHERE-A HUMP OR LOOP EXISTS THAT IS NOT ADEQUATELY VENTED.
THE SUBSEQUENT CLEARING OF THE AIR OR COLLAPSE.0F THE STEAM V0ID CAUSES A SHUTDOWN COOLING ISOLATION DUE TO A SENSED HIGH PRESSURE AND MAY CAUSE A WATER HAMMER.
e G.E. RECOMMENDED THAT PLANTS THOROUGHLY REVIEW THE SHUTDOWN COOLING MODE OF OPERATION WITH PARTICULAR ATTENTION TO VENTING, DRAINING, FLUSHING,. FILLING, AND WARMUP PROCEDURES.
G.E. ALSO RECOMMENDED CAREFUL CONTROL OF FLOW RATES AND PRESSURELTO MINIMIZE THE FORMATION OF VOIDS OR AT LEAST TO MORE GENTLY CLEAR VOIDS.
FOLLOWUP o
.THE PLANTS APPEAR TO BE: COMMUNICATING WITH EACH OTHER AND WITH-G.E. TO DETERMINE FURTHER PREVENTIVE OR MITIGATIVE ACTIONS.
VARIOUS BWRs 94-12 o
REGION III IS CURRENTLY DEVELOPING-A SUPPLEMENT TO INFORMATION NOTICE 87-10, " WATER HAMMER DURING RESTART OF RHR PUMPS."
THE NEED TO INCORPORATE INFORMATION ON WATER HAMMER DURING SHUTDOWN COOLING WILL BE EVALUATED.
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