Information Notice 1996-69, Operator Actions Affecting Reactivity

Operator Actions Affecting Reactivity

ML031050475
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, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	12/20/1996
Revision:	0
From:	Martin T T Office of Nuclear Reactor Regulation
To:
References
IN-96-069, NUDOCS 9612160118
Download: ML031050475 (8)

December 20, 1996

NRC INFORMATION NOTICE 96-69: OPERATOR ACTIONS AFFECTING REACTIVITY

Addressees

All holders of operating licenses or construction permits for nuclear power reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alertaddressees to operating events that have affected reactivity. It is expected that recipients willreview the information for applicability to their facilities and consider actions, as appropriate,to avoid similar problems. However, suggestions contained in this information notice are notNRC requirements; therefore, no specific action or written response is required.BackgroundGeneric Letter 85-05, "Inadvertent Boron Dilution Events," dated January 31, 1985, was usedto indicate the staffs position that resulted from the evaluation of Generic Issue 22,"Inadvertent Boron Dilution Events." The generic letter considers an unmitigated borondilution event as a serious breakdown in the licensee's ability to control its plant and stronglyurges each licensee to assure itself that adequate protection against boron dilution eventsexists in its plants. However, the consequences are not severe enough to warrant backfittingrequirements for boron dilution events at operating reactors.In the past several years, this year in particular, there have been numerous events whereoperator actions inappropriately affected reactivity. This information notice highlights severalrecent events in which poor command and control during reactivity evolutions have led tounanticipated conditions.

Description of Circumstances

Byron Unit IOn June 12, 1996, the licensee made four dilutions of the reactor coolant system. Only thefirst dilution was calculated in advance. At the time, Byron Unit I was in cold shutdown for arefueling outage. Fuel had been reloaded into the core, and the reactor head was inposition. The reactor coolant loops were isolated to support steam generator tube inspectionand repair. The reactor coolant system (RCS) boron concentration was 1,984 parts permillion (ppm). The RCS silica concentration was elevated at 4 ppm.96121601 18 '\\8 ttfDK ItE SotfC. ;os IN 96-69December 20, 1996 A series of dilutions was planned to reduce silica levels and bring the RCS boronconcentration closer to the 1,600 ppm starting point for the planned dilution to criticality. Thetarget RCS boron concentration was 1,700 ppm.The operations staff added approximately 7,600 liters [2,000 gallons] of pure, unboratedwater from the primary water storage tank through a feed-and-bleed dilution. A reactoroperator calculated the expected boron concentration after this dilution to be no less than1,837 ppm. The subsequent chemistry sample results indicated a boron concentration of1,942 ppm.On the basis of the chemistry sample result, the reactor operators performed a seconddilution of 7,600 liters [2,000 gallons] without conducting formal calculations expecting toachieve a boron concentration of around 1,800 ppm. The chemistry sample after the seconddilution indicated a boron concentration of 1,877 ppm. Based on this and a subsequentchemistry sample, but without formal calculations, the reactor operators made two additionaldilutions of 15,200 liters [4,000 gallons] each, expecting a final boron concentration of greaterthan 1,700 ppm. The chemistry sample results after the fourth dilution indicated a boronconcentration of 1,521 ppm. The reactor operators added borated water to increase theboron concentration to about 1,585 ppm to ensure adequate shutdown margin. Thelicensee's Technical Specifications require a 1.3-percent shutdown margin, which thelicensee indicated was about 1,164 ppm boron.The licensee determined that the sample line was not adequately purged before the firstthree samples were obtained. However, the sample valve was left open for about 1 hourbefore the fourth sample was taken, which allowed the line to be adequately purged; thus arepresentative sample was obtained.Washington Nuclear Project No. 2On June 27, 19°6, the reactor achieved criticality at Step 8-3 in the rod pull sequence.Criticality was expected at Step 12-18 of the rod pull sequence, with an acceptable range ofachieving criticality (+/- 10 my,) between Steps 11-12 and 14-20. Achieving criticality atStep 8-3 was outside the licensee's self-imposed acceptable range of values and wasapproximately 16 mk,,,,, before the calculated estimated critical position. In accordancewith plant procedures, operators manually inserted control rods-to shut-down the reactor.The estimated critical position calculated for the startup was performed using aninappropriate parameter for the plant conditions. The nuclear engineer selected an incorrectparameter for xenon dependence. The reactor was shutdown for a short period of time andxenon did not completely decay and was incorrectly accounted for in the calculation.During the approach to criticality, members of the control room staff were involved withactivities related to shift turnover, this may have distracted personnel involved with thestartu KY 11IN 96-69December 20, 1996 St. Lucie Unit 1On January 22, 1996, while performing a routine manual boron dilution of the reactor coolantsystem, the board reactor controls operator (RCO) was distracted leading to an over dilutionwith reactor power reaching 101 percent. During the evolution the RCO responded to asecondary plant annunciator and lost track of the routine dilution. He then requested to berelieved by the desk RCO while he prepared his lunch. During the turnover, there was nodiscussion of the dilution in progress which continued for seven minutes until the board RCOreturned and realized his error. The operators took prompt corrective action of stopping thedilution and initiating manual boration.DiscussionAt Byron, an inadequate sampling procedure and inadequate calculations of boronconcentration led to an unexpected dilution of 179 ppm below the target boron concentrationof 1,700 ppm. The licensee determined the chemistry sample procedure to be deficient.This deficiency was originally noted during review of procedures for post-accident sampling;however, the chemistry staff failed to recognize the implications on routine sampling. Thelicensee's dilution procedure was deficient, also, In that It did not have provisions for dilutionswith the loop stop isolation valves closed. The operators calculated the reduced volume forthe dilution calculations and attributed the differences in expected and sample boronconcentrations to the conservative reactor coolant system volume used in the calculation.The reactor operators continued with successive dilutions based on the original calculationand the sample concentrations but failed to adequately question the higher than expectedsample values and to perform acceptable calculations between dilutions in order to determinethe additional dilution amounts.At Washington Nuclear Project No. 2, Shift Nuclear Engineers, because of inadequatetraining on a recent software modification, incorrectly selected a parameter which resulted inthe wrong estimated critical position. These engineers and operators suspected a problemwith the estimated critical position but did not effectively resolve their concerns or expressthem to higher management. The engineers did perform an independent verification whichconfirmed the estimated value; however, they used the same software and input parameters.During the startup, the control room staff realized that the reactor would go critical outsidetheir self-imposed +/- 10 mk,,,,. reactivity band; however, they continued the startupbecause of their interpretation of a poorly written startup procedure. The likelihood ofachieving early criticality was not communicated to upper management, either. Whencriticality was achieved, operators then acted conservatively and manually shut down thereactor.At St. Lucie Unit 1, the board RCO exhibited inattentiveness to a routine evolution affectingreactivity. The RCO initiated the dilution without notifying other control room personnel andfailed to discuss the evolution in progress with his temporary replacement prior to exiting the IN 96-69December 20, 1996 control room. As a result, the senior reactor operator and the other operators were unawarethat a reactivity addition was taking place. Upon returning to the control room, the RCOnoted an alarm which was due to increasing reactor coolant system pressure, realized hiserror, and took prompt corrective actions.Both the Byron and the Washington Nuclear Project events involved a lack of questioningattitude that would have allowed the operators to suspend the ongoing evolutions affectingreactivity until they had an understanding of the unexpected plant indications. Furthermore,all three events contained inappropriate command and control over activities associated withreactivity manipulations.Additional details of these events can be found in the following inspection reports: ByronUnit I IR 50-454/96-05; 50-455/96-05 dated July 31, 1996 [9608120029]; WashingtonNuclear Project No. 2 IR 50-397/96-16 dated September 12, 1996 [96091902751; andSt. Lucie IR 50-247/96-03 dated February 22, 1996 [96071502941.This information notice requires no specific action or written response. If you have anyquestions about the information in this notice, please contact one of the technical contactslisted below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager./Thomas T. Martin, DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: N. D. Hilton, Rill M. S. Miller, Ril(815) 234-5451 (407) 464-7822E-mail: ndh@nrc.gov E-mail: msm@nrc.govR. C. Barr, RIV S. S. Koenick, NRR(509) 377-2627 (301) 415-2841E-mail: rcb3@nrc.gov E-mail: ssk2@nrc.gov

Attachments:

List of Recently Issued NRC Information NoticesArrP c~ hJ PAm IN 96-69December 20, 1996 control room. As a result, the senior reactor operator and the other operators were unawarethat a reactivity addition was taking place. Upon returning to the control room, the RCOnoted an alarm which was due to increasing reactor coolant system pressure, realized hiserror, and took prompt corrective actions.Both the Byron and the Washington Nuclear Project events involved a lack of questioningattitude that would have allowed the operators to suspend the ongoing evolutions affectingreactivity until they had an understanding of the unexpected plant indications. Furthermore,all three events contained inappropriate command and control over activities associated withreactivity manipulations.Additional details of these events can be found in the following inspection reports: ByronUnit I IR 50-454/96-05; 50-455/96-05 dated July 31, 1996 [9608120029]; WashingtonNuclear Project No. 2 IR 50-397/96-16 dated September 12, 1996 [9609190275]; andSt. Lucie IR 50-247/96-03 dated February 22, 1996 [9607150294].This information notice requires no specific action or written response. If you have anyquestions about the information in this notice, please contact one of the technical contactslisted below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.original signed by D.B. MatthewsThomas T. Martin, DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts:N. D. Hilton, Rill(815) 234-5451E-mail: ndhenrc.govM. S. Miller, RII(407) 464-7822E-mail: msm@nrc.govR. C. Barr, RIV(509) 377-2627E-mail: rcb3@nrc.govS. S. Koenick, NRR(301) 415-2841E-mail: ssk2@nrc.gov

Attachments:

List of Recently Issued NRC Information NoticesTech Editor has reviewed and concurred on 9/24/96OFC TECH D:DRCH C:PECB:DRPM D:

CONTACT

S _AJNAME BABoger AEChaffee* aDATE 09/24/96 11/15196 12/12/96 1243,96fi- ----. -p- k kisiWI-[UMIC-NAL KtVUUKU WJTjDOCUMENT NAME: 96-69.1N IN 96-December , 1996 At St. Lucie Unit 1, the board RCO exhibited inattentiveness to a routineevolution affecting reactivity. The RCO initiated the dilution withoutnotifying other control room personnel and failed to discuss the evolution inprogress with his temporary replacement prior to exiting the control room. Asa result, the senior reactor operator and the other operators were unawarethat a reactivity addition was taking place. Upon returning to the controlroom, the RCO noted an alarm which was due to increasing reactor coolantsystem pressure, realized his error, and took prompt corrective actions.Both the Byron and the Washington Nuclear Project events involved a lack ofquestioning attitude that would have allowed the operators to suspend theongoing evolutions affecting reactivity until they had an understanding of theunexpected plant indications. Furthermore, all three events containedinappropriate command and control over activities associated with reactivitymanipulations.Additional details of these events can be found in the following inspectionreports: Byron Unit 1 IR 50-454/96-05; 50-455/96-05 dated July 31, 1996[9608120029]: Washington Nuclear Project No. 2 IR 50-397/96-16 dated September12, 1996 [9609190275]; and St. Lucie IR 50-247/96-03 dated February 22. 1996[9607150294].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.Thomas T. Martin, DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: N. D. Hilton, RIII M. S. Miller, RII(815) 234-5451 (407) 464-7822E-mail: ndh@nrc.gov E-mail: msm@nrc.govR. C. Barr, RIV S. S. Koenick. NRR(509) 377-2627 (301) 415-2841E-mail: rcb3@nrc.gov E-mail: ssk2@nrc.gov

Attachments:

List of Recently Issued NRC Information NoticesOFC TECH

CONTACT

S D:DRCH C:PECB:DRPM D:DRNAME

• BABoger* AEChaffee TMa rtinDATE 09/24/96 11/15/96 1fi t296 &s, S;iJ /-V96LUFFICIAL RLLURU LUWYJDOCUMENT NAME: G:\SSK2\REACTIVE.RV3

~ i~ IN 96-December , 1996 This information notice requires no specific action or written response. If you have anyquestions about the information in this notice, please contact one of the technical contactslisted below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.Thomas T. Martin, DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts:N. D. Hilton, Rill(815) 234-5451E-mail: ndh@nrc.govM. S. Miller, Ril(407) 464-7822E-mail: msmenrc.govR. C. Barr, RIV(509) 377-2627E-mail: rcb3@nrc.govS. S. Koenick, NRR(301) 415-2841E-mail: ssk2@nrc.gov

Attachments:

List of Recently Issued NRC Information Noticed) '/4/xOFC TECH D:DRCH C:PECB:DRPM D:DRPM

CONTACT

SNAME __ _ _ BABoger t AEChaffee TTMartinDATE /R/96 --F/ I/96 / /96 I //96[OFFICIAL RECORD COPY)DOCUMENT NAME: G:\SSK2\REACTIVE.RV3

.I,. .I .AttachmentIN 96-69December 20, 1996 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to96-6896-6796-6696-6596-64Incorrect Effective DiaphragmArea Values in Vendor ManualResult in Potential Failureof Pneumatic DiaphragmActuatorsVulnerability of EmergencyDiesel Generators to FuelOil/Lubricating Oil Incom-patibilityRecent MisadministrationsCaused by Incorrect Cali-brations of Strontium-90Eye ApplicatorsUndetected Accumulationof Gas in Reactor CoolantSystem and InaccurateReactor Water LevelIndication During ShutdownModifications to Con-tainment Blowout PanelsWithout AppropriateDesign Controls12/19/9612/19/9612/13/9612/11/9612/10/96All holders of OLsor CPs for nuclearpower reactorsAll holders of OLsor CPs for nuclearpower reactorsAll U.S. NuclearRegulatory CommissionMedical Use Licenseesauthorized to usestrontium-90 (Sr-90)eye applicatorsAll holders of OLsor CPs for nuclearpower reactorsAll holders of OLsor CPs for nuclearreactorsOL = Operating LicenseCP = Construction Permit