Information Notice 1990-28, Potential Error In High Steamline Flow Setpoint
UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555April 30, 1990NRC INFORMATION NOTICE NO. 90-28: POTENTIAL ERROR IN HIGH STEAMLINEFLOW SETPOINT
Addressees
- All holders of operating licenses or-construction permits for boiling waterreactors (BWRs).
Purpose
- This information notice is intended to alert addressees to possible errors inthe method used to determine the proper setpoints.for-the steamline flow dif-ferential pressure instruments that initiate isolation of the High PressureCoolant Injection (HPCI) and Reactor Core Isolation Cooling (RCIC) systemsat a limit corresponding to a specific percentage of the rated steam flow.It is expected that recipients will review the information for applicabilityto their facilities and.consider actions, as appropriate, to avoid similarproblems. However, suggestions contained in this information notice do notconstitute NRC requirements; therefore,-no specific action or written responseis required.
Description of Circumstances
- On November 30, 1989, during a.surveillance test of the HPCI system at theFitzPatrick Nuclear Power Plant, automatic isolation of the steam admissionvalves on high steamline flow occurred (Docket No. 50-333; LER No. 89-025-00).An-intensive series.of tests was initiated to identify the root cause of thisevent. To perform these tests, additional instrumentation was connected tothe steamline flow instruments to determine the differential pressure detectedby the instrumentation. This testing led to the determination that the signalthat resulted from startup of the turbine was close to the Isolation setpointand, in some cases, was greater than the setpoint. Because the isolation set-point was in accordance with the value specified in the technical specifications,and because no leakage or reason for a high-flow condition could be found, apossible problem either with the value specified for the setpoint or with theamount of steam needed to start the turbine, or both, was identified.Discussion:At FitzPatrick, the HPCI system is a steam turbine driven Emergency CoreCooling System designed to supply makeup water to the reactor vessel in900420359- K)-IN 90-28April 30, 1990 the event of a loss-of-coolant accident. The high steam flow isolation ofthe HPCI turbine is designed to shut the steamline isolation valves to theturbine if the steam supply piping ruptures. At FitzPatrick, this.flow signalis derived by sensing the differential pressure that results from flow throughthe steam supply piping at an elbow in the piping. If this differentialpressure, expressed in inches of water, reaches the value given in the tech-nical specifications, the isolation valves close.The accepted value of steam flow that indicates that a break in the steam-line has occurred is typically 300 percent of the rated steam flow. Thedetermination of the differential pressure that corresponds to this flow,and hence the Indication that a steamline break has occurred is the subjectof General Electric Nuclear Services Information Letter (SILI No. 475.* Theanalytic method described in the SIL applies to HPCI and RCIC systems and usesmeasured data from the as-built system operating under rated conditions in thesurveillance test mode, rather than using purely theoreticaltanalysis, tocalculate the differential pressure that would exist at 300-percent flow.This differential pressure then becomes the setpoint for the switch thatinitiates isolation of the system. However, other methods based on soundengineering principles may also be appropriate.At FitzPatrick, as part of the root cause determination, the intensive seriesof tests found that the actual differential pressure setpoint that caused thel1solati on nniurresspned-tu approx-imately-200-pereent-flow, -an--that-the-staxtup--of the HPCI system occasionally caused the flow to reach this value. Such asetpoint is conservative from the viewpoint of the safety function of the highsteamline flow trip, but it adversely affects the reliability of the HPCIsystem. Performing the calculations in accordance with SIL No. 475 resultedin the removal of this conservatism from the setpoint and in the restorationof the reliability of the HPCI system.The HPCI system had operated with the setpoint conservatism for 14 years untilseveral recent changes were made to the system. These changes Included testmethodology improvements, hydraulic actuator replacement (which resulted inthe need for additional steam for turbine startup), and turbine stop valverewiring. Setting the setpoint according to Revision 2 of SIL No. 475 pro-vides the proper value for initiation of the Isolation function.*Revision 2 of SIL No. 475 was issued November 28, 1988, by the GeneralElectric Company, San Jose, California. As noted in Revision 2, errors inthe original and in Revision I have been corrected in Revision IN 90-28i: April 30, 1990 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact thetechnical contact listed below or the appropriate NRR project manager.Charles E. ossl, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor Regulation
Technical Contact:
D. LaBarge, NRR(301) 492-1421
Attachment:
List of Recently Issued NRC Information Notices-_ _ _ i an _ * -' i 5 14 -4it --;~
I 'AttachmentAIN 90-N8prIl 30, 1990Page I of ILIST OF RECENTLYV ISSUEDNRC INF0RHATIhN NOTICESInsormatuon Date orHotie No. Subeet Issuance Issued to90-27 Clarification of the 4130/90 All uranium fuelRecent Revisions to the fabrication andRegulatory Requirments conversion facilitiesfor Packaging of UrnniumNexafluords 41. l) forTransportationS9W70, Possible Indications of 4/26/90 All holders of OLsSupp. I MisrepresenUted Vendor or CPs for nuclearProducts power reactors.90-26 Inadequate Flow of 4/24/90 All holders of OLsEssential Service Water or CPs for nuclearto Rooe Coolers end Heat power reectors.Exchangers for EngineeredSafety-Feature Systeme90-25 Lost of Vital AC Power 4/16o90 All holders of OLswith Subsequeit Reactor or CPs for nuclearcoolent Systee Heat-Up power reactors.90-24 Transportation of Model 4/10/90 All NRC licenseesSpec 2-T Radiographic authorized to use.Exposure Device transport, or operateradiographic exposure-devices and sourcechangers..90-29 Improper Installation of 4/4/90 All holders of OLsPatel Conduit Seals or CPs for nuclearpower reactors.90-22 Unenticipoted Equipuent 3/23/90 All holders of OhsActuations Fellowing or CPs for nuclearRestoration of Power power reactorsto Rosemeust TransmitterTrip Units90-21 Potential Failure of Motor- 3/22/90 All holders of OLsOperated Butterfly Valves or CPs for nuclearto Operate Because Valve power reactors.Seat Friction was Under-stistted0L
- Operating LicenseCP
- Construction PermitUNITED STATESNUCLEAR REGULATORY COMMISSIONWASHINGTON, D.C. 20555OFFICIAL BUSINESSPENALTY FOR PRIVATE USE, $300FIRST CLASS MAILPOSTAGE b FEES PAIDUSNRCPERMIT No. 5 E7
..- .vIN 90-28April 30, 1990 This information notice requires iyou have any questions about the 1technical contact listed below orio specific action or written response. IfInformation in this notice, please contact thethe appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor Regulation
Technical Contact:
D. LaBarge, NRR(301) 492-1421
Attachment:
List of Recently Issued NRC Information NoticesDocument Name:INFO NOTICE -LABARGE, KADAMBI*SEE PREVIOUS CONCURRENCES*OGCB:DOEA:NRR*PD11:DRP:NRRNPKadambi DLaBarge03/28/90 04/03/90*RPB:ADMTechEd04/17/90*C/OGCB:DOEA:NRRCHBerlinger04/20/90 IN 90-XXApril xx, 1990 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact thetechnical contact listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor Regulation
Technical Contact:
D. LaBarge(301) 492-1421
Attachment:
List of Recently Issued NRC Information NoticesDocument Name: INFO NOTICE -LABARGE, I*SEE PREVIOUS CONCURRENCES*OGCB:DOEA:NRR*PD11:DRP:NRRNPKadambi DiaBarge03/28/90 04/03/904/4~10*RPB:ADMTechEd04/17/90(ADAMB IC/O 'B~$~RRICHB r gerI04/X/90 1D/DOEA:NRRCERossi04/ /90 IN 90-XXMarch xx, 1990 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact thetechnical contact listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor Regulation
Technical Contact:
D. LaBarge(301) 492-1421
Attachment:
List of Recently Issued NRC Information Notices1 V't Nm- NO IIt Name:} INFO NOTICE -LABARGE, KADAMBINPKadambi03/M/90NRR PD11:DRP:DLaBargec0//S /90RPB :ADMTechEd-j403/ /90fl17/WC/OGCB:DOEA:NRRCHBerlinger03/ /90D/DOEA:NRRCERossi03/ /90