Information Notice 1990-65, Recent Orifice Plant Problems
UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555October 5, 1990NRC INFORMATION NOTICE NO. 90-65: RECENT ORIFICE PLATE PROBLEMS
Addressees
- All holders of operating licenses or construction permits for nuclear powerreactors.
Purpose
- This information notice is intended to alert addressees to recent problems thathave been identified with orifice plates. It is expected that recipients willreview the information for applicability to their facilities and consideractions, as appropriate, to avoid similar problems. However, suggestionscontained in this information notice do not constitute NRC requirements;therefore, no specific action or written response is required.
Description of Circumstances
- Recent licensee and NRC inspections have identified two problems associatedwith orifice plates. Namely, the installation of orifice plates in the reversedirection and the deformation of orifices in the direction of flow.With respect to the first of the two problems, on August 8, 1988, operators atthe San Onofre Nuclear Generating Station, Unit 1, discovered-an error inseveral daily calorimetric power calibrations. Further investigation revealedthat one of the three feedwater flow indicators was providing flow indicationthat was lower than the actual feedwater flow. This error resulted in theindicated power on the nuclear instrumentation system being adjusted as much asfour percent lower than the actual reactor power. The licensee determinedthat the orifice plate for the deficient flow indicator was installed backwards,causing the indicated flow to be less than the actual flow. Subsequent evaluationshowed that all accident scenarios described in the Final Safety AnalysisReport produced acceptable results despite the error. In 1985, San Onofre Unit1 reported a similar event (LER 50-206/85-014).During an NRC walkdown of the containment spray system at the Farley NuclearPlant in April 1989, inspectors found that an orifice plate in a flow elementhad been installed backwards. The flow element provided spray additive tankflow indication in the control room. The licensee subsequently found fourother orifice plates, used in the charging system, the auxiliary feedwatersystem, and the containment spray system, that were reversed. Similarly, inJuly 1989 the Shearon Harris Nuclear Power Plant found a reversed orificeplate. This orifice plate also was used to determine the flow rate for thecontainment spray system spray additive tank.( < O 9 2 8 1 6 6 v 7C
IN 90-65October 5, 1990 Reversed orifice plates have also been found at the Salem Nuclear Generat-ing Station, Brunswick Steam Electric Plant, Waterford Steam Electric Plant,Surry Power Station, and North Anna Power Station. At the Salem plant, inMay 1989, the flow metering orifices for the high-head cold leg safety injectionline were found installed backwards. After the orifices were correctlyinstalled, the indicated flow rate was 15 percent greater. At Brunswick, inFebruary 1989, the licensee discovered a flow restricting orifice installedbackwards in the high-pressure core injection minimum flow line, and in twoother systems. Waterford experienced problems with low indicated flow in therecirculation line of a high pressure safety injection pump. The problem wastraced to a reversed flow orifice in May 1989. At Surry in August 1989, an NRCinspector discovered a reversed flow orifice after the completion of a correctiveaction program aimed at flow orifices. Further walkdowns by the licenseeidentified two additional flow orifices installed backwards. At North Anna inSeptember 1989, a total of nine flow orifices were determined to be installedbackwards. Only orifices which are accessible during power operation wereinspected. The root cause of these events has generally been determined to beinadequate procedures for and inspection of installations.In February 1989, a second problem with orifice plates was identified atBrunswick, i.e., several flow restricting orifices were deformed in the direc-tion of flow. The orifices were located in the residual heat removal system,the core spray injection and minimum flow line, and the high-pressure coolantinjection system. Each of the orifice plates was manufactured from A240-316-statless-steel-arnd-was 8-inch-thik- _ltisth-icknes-Swas based on standardorifice design that did not consider the thickness needed to prevent deforma-tion caused by flow and the differential pressure across the orifice plate.In one instance, the orifice bore had increased from 1.021 inches to 1.088inches, and the plate had ballooned outward approximately 0.5 inch. Subse-quently, the licensee evaluated the design of the orifice plates using allow-able material stresses, orifice plate geometric configurations, and system flowrates. The results of this evaluation indicated that the applied stressexceeded several times the allowable material yield stress. The licenseedetermined that the root cause of the deformation was an inadequate designthickness specification.Discussion:An orifice plate is commonly used as a primary flow element, and produces adifferential pressure from which a flow rate can be determined., Orifice plateshave a handle on which pertinent data is permanently marked, such as orificediameter, flange size, pressure rating, and, as appropriate, the word "In-let." The two most common types of orifice plates are squared edge and bevelededge. On a beveled edge orifice plate that is properly installed, the wordInlet" faces the inlet direction and the beveled edge faces the outlet direc-tion. A square edged orifice plate is not dependent upon orientation toperform its function. However, Installation procedures for both types oforifice plates should be consistent. A beveled orifice plate that is installedbackwards would provide a lower differential pressure across the flow element,resulting in a flow rate measurement that is lower than the actual flow rate.
IN 90-65October 5, 1990 Orifice plates are also used as flow restrictors, to provide a specifichydraulic resistance in a piping system to limit flow rate. A failure ofthe orifice plate could cause excessive recirculation or bypass flow, which maydecrease the flow being delivered to the main flow path during an accident.The failure of the orifice plate could also reduce the hydraulic resistance inthe system, increasing the total pump flow rate and the probability of centrif-ugal pump runout. Runout could damage the internal components of the pump,lead to inadequate net positive suction head, and overload the pump motor.Increased flow rates in the orificed line could also lead to increased pipevibration and erosion. In addition, permanently deformed orifice plates couldprovide inaccurate flow measurements.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.A Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: Scott Sparks, Region II(404) 331-4187Andrew Kugler, NRR(301) 492-0834Attachment: List of Recently Issued NRC Information Notices
- IIAttachment 1IN 90-51October 5, 1990Page I of ILIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESIntormation cat. orNotice no. SubJect Issuance Issued to90-64 Potential for Comma-Mode 10/4/90 All holders ofFailure of High Pressure OLs or CPs forSafaty Injectlon Pumps or pressurized-waterRelease of Reactor Coolant reactors.Outside Containment DuringA Loss-Of-Coolant Accident90-43 Management Attention to the 10/3/90 All fuel cycleEstablishment and Main. licensees possess-tenance of A Nuclear Ing more thanCriticality Safety Program crtrcal mssquantities ofspecial nuclearmaterial.90-42 Requirements for Import 9/25/90 All irradiatedand Distribution of gemstone importersNeutron-Irradiated Goes end distributors.and all non-powerlicensees.90-41 Potential for Residual 9/20/90 All holders ofHeat Removal Pump OLs or CPs forPump Damage Caused By nuclear powerParallel Pump interaction reactors.90-60 Availability of Failure 9/20/90 All holders ofData In the Government. OLs or CPs forIndustry Data Exchange nuclear powerProgram reactors.90-59 Errors In the Use of 9/17/90 All medicalRadioactive todine-131 licensees.90-58 Improper Handling of 9/11/90 All NRC medical-Opttaft& Strontiua.9L ._ iceasees.Beta Radiation Applicators90-S7 Substandard, Refurbished 9/5/90 All holders of OLsPotter S Brumfield Relays or CPs for nuclearMisrepresented As Nw power reactors.OL
- Operating LicenseCP
- Construction PermitUNITED STATESNUCLEAR REGULATORY COMMISSIONWASHINGTON, D.C. 2055OFFICIAL BUSINESSPENALTY FOR PRIVATE USE. $300FIRST CLAS MAILPOSTAGE & FEES PAIDUSNAC:PERMIT@ No a9 IN 90-65October 5, 1990 Orifice plates are also used as flow restrictors, to provide a specifichydraulic resistance in a piping system to limit flow rate. A failure ofthe orifice plate could cause excessive recirculation or bypass flow, which maydecrease the flow being delivered to the main flow path during an accident.The failure of the orifice plate could also reduce the hydraulic resistance inthe system, increasing the total pump flow rate and the probability of centrif-ugal pump runout. Runout could damage the internal components of the pump,lead to inadequate net positive suction head, and overload the pump motor.Increased flow rates in the orificed line could also lead to increased pipevibration and erosion. In addition, permanently deformed orifice plates couldprovide inaccurate flow measurements.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager., n- Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: Scott Sparks, Region II(404) 331-4187Andrew Kugler, NRR(301) 492-0834Attachment: List of Recently Issued NRC Information NoticesDocument Name: ORIFICE*SEE PREVIOUS CONCURRENCES**SEE PREVIOUS FAX CONCURRENCE*OGCB:DOEA:NRR **RII *RPB:ADM C/OGCB:DOEA:NRR D/DOEALI _-AJKugler SSparks TechEd CHBerlinger CERossir09/06/90 09/10/90 09/12/90 09/26/90 W/, /90
IN 90-XXSeptember xx, 1990 Orifice plates are also used as flow restrictions, which provide a specifichydraulic resistance in a piping system to limit the flow rate. A failure ofthe orifice plate could cause excessive recirculation or bypass flow, which maydecrease the flow being delivered to the main flow path during an accident.The failure of the orifice plate could also reduce the hydraulic resistance inthe system, increasing the total pump flow rate and the probability of centrif-ugal pump runout. Runout could damage the internal components of the pump,lead to inadequate net positive suction head, and overload the pump motor.Increased flow rates in the orificed line could also lead to increased pipevibration and erosion. In addition, permanently deformed orifice plates couldprovide inaccurate flow measurements.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:Scott Sparks, Region II(404) 331-4187Andrew Kugler, NRR(301) 492-0834Attachment: List of Recently Issued NRC Information NoticesDocument Name: ORIFICE*SEE PREVIOUS CONCURRENCES**SEE PREVIOUS FAX CONCURRENCE*OGCB:DOEA:NRRAJKugler09/06/90**RIISSparks09/10/90*RPB:ADMTechEd09/12/90CB:DOEA:NRRCHBerlinger094 /90D/DOEA:NR?,,CERoss I09/ /90
IN 90-XXSeptember xx, 1990 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:Scott Sparks, Region II(404) 331-4187Andrew Kugler, NRR(301) 492-0834Attachment:List of Recently Issued NRC Information NoticesDocument Name:ORIFOGCB:DOEANRRAKugler 4t09/06/90RII #SSparks09/ /90RPB:ADMTechEd ,*09/ /90C/OGCB:DOEA:NRRCHBerlinger09/ /90D/DOEA:NRRCERossi09/ /90* sm A-TAcutc F&X)c ComcuARE.E4C#* Sm A1C(ED M iCgAeENJ c
- Ant w a = -T -!.Z ' d "IU101.0,_i izC 1 06/0 T/60V,_=z=,=, .0 6 Ntl-JM-2 *93N WONA40IN t0-OSeptber xx,Page 3 af 31990.4This *' -= .VJ; o' req.l~ir '] n peciflt 1.;tdfln or written r nsponsS. Ifyou Ce, F1t.tiCf1n *outi4, V ;fcrmtsor 1i this nc1tsce. pse contact oneof the technfcal (orltactb VIst*d belcm or ttd !prOnr4j*t NRR pro~ect .ioarger,Charqes C. RiOsOi DirectorDivision Ic)l. iratl'onal Events AsselssmotOffif- ot Wu :lear Reactor egiltltfllchm-Cal CWntG4%.SScott(404)I+parkt. PAcgilo IlDJ1,31-413-1Andreu Kugl9r nRR(301) 492.083$LiSt of Receltly issued NRC Ith(I i1 at4n NotielsAttachfrlet:OGCBfD0' -A;,dR.-'I 4/1 -09/06/90OkifRI I ViSSparks09d/ 0/90RP3~ ADMT ehEd09/ /90C/OGCB DO5A:NRRCH3erl ingero,/ /90D/DOEA: NRPCERs9 909! /90
.90 Sg ?0 p 39 IN 90-XXSeptember xx, 1990I This Information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:Scott Sparks, Region II(404) 331-4187Andrew Kugler, NRR(301) 492-0834Attachment:List of Recently Issued NRC Information NoticesDocument Name:ORIFOGCB:DOEA:NRRAKugler09/ /90RIISSparks09/ /90RPB:ADMTechEd MYWr-09/]i/0C/OGCB:DOEA:NRRCHBerlinger09/ /90D/DOEA:NRRCERossi09/ /90