Information Notice 1993-67, Bursting of High Pressure Coolant Injection Steam Line Rupture Discs Injures Plant Personnel

Bursting of High Pressure Coolant Injection Steam Line Rupture Discs Injures Plant Personnel

ML031070135
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000349, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	08/16/1993
From:	Grimes B K Office of Nuclear Reactor Regulation
To:
References
IN-93-067, NUDOCS 9308100248
Download: ML031070135 (14)

U -AUUNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555August 16, 1993NRC INFORMATION NOTICE 93-67: BURSTING OF HIGH PRESSURE COOLANT INJECTIONSTEAM LINE RUPTURE DISCS INJURES PLANTPERSONNEL

Addressees

All holders of operating licenses or construction permits for nuclear powerreactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to remind addressees of the hazards associated with steam drivencoolant injection systems such as the high pressure coolant injection (HPCI)system and the reactor core isolation cooling (RCIC) system at BWRs and theauxiliary feedwater system at PWRs. It is expected that recipients willreview the information for applicability to their facilities and consideractions, as appropriate, to avoid similar problems. However, suggestions Xcontained in this information notice are not NRC requirements; therefore, nospecific action or written response is required.BackgroundThe purpose of HPCI steam exhaust rupture discs is to protect the HPCI turbinecasing and associated exhaust piping from an overpressure event if the normalexhaust path to the suppression pool becomes blocked. At Quad Cities Station,two 40.6-cm [16-inch] stainless steel discs are installed in series with a6.4-cm [2.5-inch] spacer between them to allow for a pressure sensorinstrumentation line. The pressure sensor, while serving no control function,actuates an alarm in the control room at 68.9 kPa [10 psig] to alert theoperators that the inner disc is leaking. The normal range of the HPCIexhaust steam pressure is 172 to 207 kPa [25 to 30 psig].- The HPCI highexhaust pressure turbine trip setpoint is 689 kPa [100 psig] and is sensed bypressure sensors located downstream from where the section of pipingcontaining the rupture discs branches off from the exhaust piping. Thesection of piping containing the rupture discs is mounted vertically over theturbine exhaust and vents directly to the HPCI room. Pressure greater than1034 kPa [150 psig] in the exhaust line will cause the inner disc to ruptureand impact the outer disc, releasing steam into the HPCI room.

Description of Circumstances

During a quarterly inservice test of the HPCI pump at the Commonwealth EdisonQuad Cities Station, Unit 1, on June 9, 1993, the exhaust steam line rupture9308100248F QrRi IN 93-67August 16, 1993 discs burst, releasing steam into the HPCI room, burning, and slightlycontaminating, five workers. The rupture discs burst within one second afterthe turbine was started. Fire doors between the Unit 1 and Unit 2 HPCI roomswere blown off their hinges into the Unit 2 HPCI room. Both sets of doubledoors that are part of the secondary containment boundary were also blownopen. The floor latch on the inner containment door was bent; the outer doorswere also slightly damaged, but were repaired, closed and sealed approximately35 minutes after the event. The steam release was terminated by automaticisolation of the steam supply line on high HPCI turbine area temperature about20 seconds into the event.DiscussionUpon investigating the event, the licensee determined that water hadaccumulated in the turbine casing because the drain system level switches forthe Unit 1 HPCI system had failed. In April 1992, the licensee performed areliability-centered maintenance study which recommended the level switches beincluded in the preventive maintenance program but the recommendation had notbeen acted on at the time of the event. The Unit 2 HPCI drain system levelswitches were also found to be inoperable.The slug of water created during the HPCI turbine roll passed from the turbinecasing to the vertical exhaust line and compressed the air in the 40.6 cm[16 inch] line containing the rupture discs. The resulting pressure pulsecaused the inner rupture disc to burst, which impacted the outer disc asdesigned and caused it to burst as well. The exhaust line pressure sensors,located in the horizontal 61 cm [24 inch] exhaust line that tees off from thevertical 40.6 cm [16 inch] rupture disc line, did not detect a high pressure(see Figure 1). The pressure switches were within tolerance and should haveimmediately isolated the steam supply upon sensing a high exhaust pressurebefore the rupture discs burst. The fact that a high exhaust line pressurewas not detected indicates two possible causes for the disc rupture. Eitherthe inner rupture disc was degraded and burst at lower-than-design pressure,or the pressure pulse actually exceeded the design pressure and caused thedisc to burst, relieving the exhaust line pressure before the downstreampressure sensors detected a high pressure condition.While inspection of the rupture discs did not reveal any degradation fromcorrosion or aging, the vendor, Black Sivalls & Bryson, Inc, stated that thediscs are warranted for one year of service under normal conditions. The HPCIand RCIC rupture discs at Quad Cities Station had been in service for 20 yearsand were not part of any scheduled inspection or preventive maintenanceprogram. When consulted about the event, the vendor advised against using thespare discs in the plant storeroom because they were purchased at the sametime as the failed discs. The licensee later replaced the failed discs withnew units. Before this event, the licensee recently replaced a HPCI rupturedisc during a refueling outage at the Dresden Station, a plant similar to QuadCities, after finding a crack in the disc during an inspection. The rupturediscs were inspected at the Dresden station as part of an enhancement to thepreventive maintenance program that was recommended by a reliability-centeredanalysi I IIN 93-67August 16, 1993 The steam injured five workers, four of whom were participating in the HPCIpump surveillance test. The fifth, and m6st severely. injured worker was ahealth physics technician in the room on routine rounds, who was not aware ofthe danger posed by the surveillance test. The test procedure contained nospecific guidance on room occupancy. Interviews with the workers revealedthat they had performed the surveillance in the past and were familiar withthe process. This familiarity may have led to a relaxed attitude towardpersonal safety. The workers stated that during previous surveillances theysometimes evacuated the room before rolling the turbine, or stood near thedoors to be ready to escape. The licensee made no routine announcement overthe plant paging system to alert plant personnel before the HPCI-turbinestart, and the workers were not prepared for the turbine to start.A lack of constant communication between the workersand the control room mayhave contributed to the personnel injuries. If a control room operator hadbeen in contact with the workers in the HPCI room during the turbine roll, theworkers would have been aware of the impending turbine start and, after start,the steam supply might have been manually-isolated or the turbine manuallytripped before the automatic isolation caused by the high area temperatureointhe HPCI room.When the Unit 1 HPCI rupture disc failure caused the fire doors to be blownoff their hinges and into the Unit 2 HPCI room, one of the doors impacted apipe hanger in the room and moved it 5.1 centimeters [2 inches]. If the steamrelease had resulted from a high energy line break from the inlet side of theHPCI steam line instead of the exhaust line, the damage to the Unit 2 HPCIsystem could have been more severe. While high energy line breaks have beenanalyzed for safety systems at all plants, the doors to rooms containing highenergy steam lines may not have been included in the analysis. For example,at Duane Arnold Energy Center, the licensee discovered that while the HPCI andRCIC rooms were qualified for pressures of 26.2 kPa [3.8 psig], the doorsbetween these rooms and the reactor building would yield at 6.9 kPa [1 psig].The licensee for the Quad Cities Station will implement a preventivemaintenance schedule for both the HPCI and RCIC rupture discs and the levelswitches. The licensee will review the surveillance test procedure andevaluate the missile hazard created by the fire doors. The licensee replacedthe rupture discs for the Unit 2 HPCI and RCIC systems with new ones after theevent at Unit 1 and is considering burst testing the removed discs todetermine if they are degrade IN 93-67August 16, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation (NRR) project manager.Brian K. Grim s, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts: Clark Vanderniet, RIII(708) 790-5594David Skeen, NRR(301) 504-1174

Attachments:

1. Figure 1, "Simplified Layout of Quad CitiesStation HPCI Turbine Exhaust Steam Line"2. List of Recently Issued NRC Information Notices Cq~0crcOCd) h r-4 0\TOSUPPRESSIONPOOL1OUTER RUPTURE DISC _____CLOSABLE CHECKCHECK VALVE VALVE IINNER RUPTURE DISC[1 In]240.6 cm[16 in]VENT TOHPCI ROOMSTEAM INLET LINEFROM "B" MAINSTEAM LINELOCKEDOPENIIIIIRX BLDGIIII50.8 cm[20 In]61 cm[24 In]HPCI ROOM25 cm[10 In]D NOTES:1. PRESSURE SWITCH ACTUATES ALARM IN CONTROL ROOM WHEN PRESSURE BETWEEN THE INNER RUPTURE DISC AND OUTERRUPTURE DISC IS GREATER THAN 68.9 kPa [10 psig]. ALARM IS FOR INNER RUPTURE DISC LEAK DETECTION.2. REDUNDANT PRESSURE SWITCHES IN EXHAUST STEAM LINE TRIP THE HPCI TURBINE IF PRESSURE IS GREATER THAN 689 kPa [100 psig].3. RUPTURE DISC MAXIMUM DESIGN BURST PRESSURE IS 1034 kPa [150 psig].Figure 1 -Simplified Layout of Quad Cities Station HPCI Turbine Exhaust Steam Line Attachment 2IN 93-67August 16, 1993 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to93-6693-6593-6493-6393-6293-6193-6093-5993-58Switchover to Hot-LegInjection FollowingA Loss-of-CoolantAccident in Pres-surized Water ReactorsReactor Trips Causedby Breaker Testingwith Fault ProtectionBypassedPeriodic Testing andPreventive Maintenanceof Molded Case CircuitBreakersImproper Use of SolubleWeld Purge Dam MaterialThermal Stratificationof Water in BWR ReactorVesselsExcessive Reactor CoolantLeakage Following A SealFailure in A ReactorCoolant Pump or ReactorRecirculation PumpReporting Fuel Cycle andMaterials Events to theNRC Operations CenterUnexpected Opening ofBoth Doors in AnAirlockNonconservatism in Low-Temperature OverpressureProtection for Pressurized-Water Reactors08/16/9308/13/93-08/12/9308/11/9308/10/9308/09/9308/04/9307/26/9307/26/93All holders of OLs or CPsfor pressurized waterreactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor boiling water reactors.All holders of OLs or CPsfor nuclear power reactors.All fuel cycle and materialslicensees.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor pressurized-waterreactors.OL = Operating LicenseCP = Construction Permit l--IN 93-67August 16, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation (NRR) project manager.orig /s/'d by CIGrimes/forBrian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:Clark Vanderniet, RIII(708) 790-5594David Skeen, NRR(301) 504-1174

Attachments:

1. Figure 1, "Simplified Layout of Quad CitiesStation HPCI Turbine Exhaust Steam Line"2. List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCE.OFC *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-IIINAME DSkeen JMain PWen CVandernietDATE 07/08/93 , 07/08/93 07/14/93 07/14/93OFC *C:DRS:R-III *SC:OEAB:DORS *C/OEAB/DORS *C:SPLB:DSSANAME GWright I RDennig AEChaffee CEMcCrackenDATE [ 07/14/93 1 07/15/93 07/15/93 ]07/16/93I__ _ iOFC*D:DSSA*C/OGCB:DORSD/DORS A^rNAME AThadani GMarcus BGrimes tDATE 07/24/93 07/29/93 0,S/\o/93 V[OFFICIAL RECORD COPY]DOCUMENT NAME: 93-67.IN

\-IN 93-XXJuly XX, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts: Clark Vanderniet, RIII(708) 790-5594David(301)Skeen, NRR504-1174

Attachment:

List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCE.*D:DSSAAThadani07/24/93OFC *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-IIINAME DSkeen JMain PWen CVandernietDATE J 07/08/93 07/08/93 07/14/93 07/14/93OFC *C:DRS:R-III *SC:OEAB:DORS *C/OEAB/DORS *C:SPLB:DSSANAME GWright RDennig AEChaffee CEMcCrackenDATE J 07/14/93 07/15/93 107/15/93 J07/16/93.Y.OFCC/OGCB:DORSD/DORSNAME GMarcus ifM BGrimes TDATE 07/.9/93 07/ /93[OFFICIAL RECORD COPY]DOCUMENT NAME: IN93 XX.QC1 IN 93-XXJuly xx, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:Clark Vanderniet, R-III(708) 790-5594David Skeen, NRR(301) 504-1174

Attachment:

List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCEOFFICE *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-IIINAME DSkeen JMain l PWen CVandernietDATE07/08/9307/08/9307/14/9307/14/931'I*C:DRS:RIII *SC:OEAB:DORS *C:OEAB:DORS C:SPLBAS* D: DSS 3q %GWright RDenning AChaffee CEMcCracken ACThadani07/14/93 [07/15/93 07/15/93 -07/2/f93 07/2A/93C:OGCB:DORSD: DORSGHMarcus BKGrimes07/ /93 07/ /93DOCUMENT NAME: QCHPCIIN.WENC 5 G-4J -z--l -2'J 4 3-- -k k- 9 C J-

IN 93-XXJuly xx, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:Clark(708)Vanderniet, R-III790-5594David Skeen, NRR(301) 504-1174

Attachment:

List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCEOFFICE *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-IIINAME DSkeen JMain PWen CVandernietDATE07/08/9307/08/9307 114/9307/14/93L, _, I_,__ _ .., __ ...I_ I -*C:DRS:RIII S ODORS EAB:DORS C:SPLB:DSSA D:DSSAGWright R enn afaf' afee CEMcCracken ACThadani07/14/93 [ 3 07/j</93 07/ /93 07/ /93C:OGCB:DORSD:DORSGHMarcus BKGrimes07/ /93 07/ /930DOCUMENT NAME: QCHPCIIN.WEN

-E7/14/9312:53 ?03 787905538417463837P. 0',This infiyou havethe techRoactorIN 93-XXJuly xx. 1993 Irmation notice requires no specific action or written response. Itany questions about the information in this noticet please contactlcal contmct listed below or the appropriate Office of Nuclearr.gulmtion (NRR) project manager.Brian K. Grimes, DirectorDivision of sOrating RGOM SupportOffice of Nuclear Reactor RegulationTechnic~l contactsClark Vanderniet, R-II1(708) 790-5594Oavid Skeen NRR(301) 604-1174Attach4nt: List of Recently Issued NRC Information Notices/._ _ *,,1'SEL PR -.IUUb 6UNCUUMM6C,OFFIC D _ *TECH:,ED -I _ I RNAME _ JGnMain PI_. .,I -- '^A j"IR na jai4I 7/1k01.%0J//Y//93I1UATI I uJ 1 b I W ._ II nF&-flIA I C:PBDS :ISS I ----.n J T TVcr P. rAn

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Attachment:

List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCEIOFFICE *OEAB:DORS *TECH:ED _ _GC i'O W DRS:R-IIINAME DSkeen JMain PWen CVandernietDATE07/08/9307/08/9307/ W/9307/ /93C:DRS:RIII SC:OEAB:DORS C:OEAB:DORS C:SPLB:DSSA D:DSSAGWright RDenning AChaffee CEMcCracken ACThadani07/ /93 J07/ /93 07/ /93 07/ /93 07/ /93..IC:OGCB:DORSD:DORSGHMarcus BKGrimes07/ /93 07/ /93DOCUMENT NAME: QCHPCIIN.WEN I' >OFC OEAB:DORS SC/OEAB:DORS PUB:ADM C/OEAB:DORSNAME DSkeen o RDennig Tech Ed T7av LY AChaffee[DATE 17/g/93 / /93 7/P /93 / /93OFC OGCB:DORS C/DRS/R-III DRS/R-IIINAME PWen GWright CVandernietDATE / /93 / /93 / /93OFC TECH BRANCH CHF TECH BR C/OGCB:DORS D/DORSNAME l GMarcus l BGrimesDATE / /93 / /93 / /93 1 / /93 l[OFFICIAL RECORD COPY]DOCUMENT NAME: IN93 XX.QC1