IR 05000456/1990018

Insp Repts 50-456/90-18 & 50-457/90-20 on 900817-1030.No Violations or Deviations Noted.Major Areas Inspected: Selected Startup Core Performance Testing & Surveillances Performed Subsequent to Initial Core Reload

ML20062F602
Person / Time
Site:	Braidwood
Issue date:	11/16/1990
From:	Phillips M, Rescheske P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20062F597	List: IR 05000456/1990018 ML20062F593
References
50-456-90-18, 50-457-90-20, NUDOCS 9011280067
Download: ML20062F602 (9)

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U.S. IlUCLEAR REGULATORY WiifilSS10tl i

REG 10tl III

Reports flo. 50-456/90018(DRS);50-457/90020(DRS)

Docket flos. 50-456; 50-457 Licuises No. IlPF-72; NPF-77

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Licensee: Commonwealth Edison Company-Opus West III 1400 Opus Place  !

Downers Grove, IL 60515 Facility flame: Braidwood Nuclear Power Station-Units 1 & 2 Inspection At: Braceville, IL 60407 Inspection Conducted: August 17 throu9h October 30, 1990 -!

Inspector: we x1h If /6,/90 7e~gg/fR$ Rescheske b'atd '

Approved By; 4e w de H f 16, / 90

)hillips, Chief k r-

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11o W .' Datb'

Operational Programs Section inspection Summay Ins ection Ln August 17 through October 30, 1990 (Reports No. 50-456/90018(DRS); ,

5- 75020(DRS))  ;

Areas Inspected: Routine, unannounced, safety; inspection of selected startup '

core performance testing and surveillances performed for the Braidwood Unit 2 ' startup sul~ luent to the initial core reload (IP.61702, 61705,.61706, 61707, 61708,61710,72700). Also-included in this' inspection was the review of previously identified items (IP;92701, 92702). .

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Results: tio violations, deviations, or significant1 concerns were identified during this inspection.- Two previously identified violations involving  :

control of temporary alterations and plant modification's were closed. One- ;

previously identified open item will remain open.1 Based on the inspector's 4 review of procedures and completed tests, the licensee's. methodology was

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considered technically adequate and the quality;of documentation was generally ,

good.. The plant .1uclear engineering staff was' very knowledgeable in the. area .

of core performar.ce, and had a good understanding of their duties and ~!

responsibilitie L

.y 9011280067 901119 i PDR ADOCK 05000456 Q PDC p ,

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i REPORTDETAIM

Persons Contacted D. E. O'Brien, Technical Staff Superintendent E. W. Carroll, Regulatory Assurance ,

R. C. Herbert, Safety Assessment .

P. G. Holland, Regulatory Assurance  !

D.11. Kapinus, Reactor Engineer I

, C.11. Wiegand, Lead Nuclear Engineer '

The above persons attended the exit meeting held on September 13, 199 [

Other persons were contacted during the-course of the inspection, including members of the licensee's engineering and operations staff, ,

and representatives from Corporate Nuclear Fuel Services-(NFS). Action on Previously identified items  !

i (0 pen)Openitem(50-456/90013-02(DRP);50-457/90016-02(DRP)): NRC .[

to review licensee investigation and actions following problems experienced in July 1990. involving peaking factors and-Fxy limit The open item will remain open and is discussed in Paragraph 3.p of this repor ! (Closed) Violation (50-456/90002-01(DRS)';50-457/90002-01(DRS)): ,

Failure to provide design control measures for temporary alterations i commensurate with those applied to the original design. 'Immediate licensee action was to stop approving safety-related temporary- -

alterations until a mechanism was in place to ensure'the appropriate review was performed and a determination of suitability of parts and material was completed prior to installation of safety-related ,

temporary alterations. Subsequent actions. included: ' verification that the subject installed temporary alteration (example-given in -

violation) was acceptable, review of all existing safety-related- -

temporary alterations and verification.of the suitability of-parts and material for the specific application, and revision of the temporary alteration ~ procedure;BwAP 330-2. to ensure appropriate reviews were completed prior to installing temporary. alterations -

(i.e., seismic considerations,' suitability and acceptability- of . '

parts and material). All corrective _ actions have been completed satisfactorily, and this item is considered close ; (Closed) Violation (50-456/90002-02(DRS)):- Failure to update la surveillance procedure affected by a modification, which resulted in not satisfying a Technical Specification (TS) surveillanc ;

requirement and issuance of a LE immediate licensee action wa to initiate a deviation report, enter a LCO, and verify that the T'

was me Subsequent corrective action was to conduct. training ofJ

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the event and root cause and to revise the station modification checklist (BwAP1610-TI),toensureindividualdepartmentalreviews of the impact of a modification on their procedures. In addition, a new checklist (BwAP 1610-T10) was created to document the reviews for the procedural impact of a modification. All corrective actions have been completed and this item is considered close . Startup Testing and Surveillances The inspection focused on selected startup core performance testing and surveillances performed for the Braidwood Unit 2 startup subsequent to-the initial core reload. The inspector reviewed the licensee's procedures, and testing criteria and results, for satisfying the requirements in TechnicalSpecification(TS) Sections 3/4.1, 3/4.2,'and portions cf 3/4.3, involving reactivity control' systems, power distribution limits, and nuclear instrumentation. The following written procedures and' complete tests were reviewed by the inspec;or and determined to be acceptable, unless otherwise note DwVS 500-3, " Reload Startap physics Tests following' Refueling."

This procedure defined the sequence of testing and referenced the majority of-the startup testing and surveillances reviewed during the inspection. The testing required by the procedure was performed from llay 21 through June 29, 199 Bw051.1.1.1.e-2, " Unit Two Shutdown liargin Surveillance During Operation." This procedure was )erformed on May 26, 1990, prior to-5% rated thermal power (RTP). T1e results satisfied TS 4.1.1.1. withthecalculatedavailableshutdownmargin(SDil)greaterthan-1300 pcm. C Curve BookBwCB-2)

(ycle 2 data _(predicted was used in the cal worths)

_culation,from the Braidwood Unit 2 BwVS 500-5, " Rod and Boron Worth lleasurements." This procedure was performed or.11ay 25 and 26,1990, to determine hot zero power (ilZP)

critical boron concentrations and integral and differential rod worths. The boron endpoint method.was used to measure critical boron concentration; and rod and boron worths were_ determined using rod swap techniques and compared to the predicted' worths. The results of the testing satisfied the acceptance criteri BwVS 1.1.3.a-1, "lioderator Temperature Coefficient - Low Power."

This procedure was performed on llay 26, 1990, prior to 5% RTP, by calculating:theisothermal. temperature _ coefficient (ITC)for.various heatup and cooldown cycle Using data from the Nuclear Design it was determined Report (e.g.,. doppler that the moderator temperature temperature coefficient),)

coefficient (!1TC would remain ,

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negative throughout Cycle 2, which satisfied TS requirement-4.1.1. BwVS 2.3.2-1, "Nucicar Enthalpy Rise flot Channel Factor and RCS .

Total- Flow Rate Check." This: procedure was performed on June 2 and '

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June 13,1990, prior to 75% RTP.. - The nucicar enthalpy rise ho ~

channel factor (NFDH) and reactor coolant system (RCS) flow rate were calculated using a recent incore f1_ux map. The results fro the surveillances satisfied the requirements of TS 4.2.3.2.a.- ,

f. During power acsension testing, BwVS 500-3 required.the quadran '

power tilt ratios' (QPTR) to be determined at various. power level [

using flux map data. The.results of this testing were acceptable i (QPTR less than 1.02), except for a small. tilt indicated at 30% RTP- -

(June 1 1990), during the first full core flux map. Reactor power waslimItedto50%RTPuntilanotherfluxmapwasperforme !

2Bw05 2.4.1.a-1, " Unit Two Quadrant Power Tilt Ratio Calculation," !

was successfully performed on June 15, 1990, above 50% RTP, using ,

indicated power range detector currents. This procedure was'a l routine surveillance performed to satisfy TS 4.2.4. g. 2Bw05 2.1.1.a-1, " Axial Flux Difference Weekly Surveillance." "This-surveillance was initially performed on fiay 27, 1990, at about 15% ' i RTP, and verified that the indicated axial flux difference (AFD) fo '

each excore channel was within the limits in accordance with TS 4.2.1.1.a. The indicated AFD was within the allowable target band of the flux difference curves in BwCB- ,

h. BwVS 2.1.3-1, " Quarterly Measurement of-Target Axial Flux. Difference."- .

This procedure was performed on Augutt 21, 1990, at about 99%.RTP, :

to satisfy the monthly surveillance requirement:in TS-4.2. The-

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actual AFDs for each excore channel'were measured, the projected' ,

100% power target AFDs were calculated, and the BwCB-2, Revision 21, -

curves and process computer were updated to reflect the current i target slopes and bands. The quarterly surveillance- requirement of f TS 4.2.1.3 was also met by the performance of this procedure. The !

BwCB-2 Cycle 2 curves had previously been updated on May 16, June 25, July 10, and July 24, 1990.^ 'f 1. BwVS 3.1.1-5, "Incore-Excore Axial Flux Quarterly Calibration." '

This procedure was performed on June 12,'1990, at about'49%.RTP,

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n and on June 20, 1990, at'about 96% power. The procedure was used to calibrate the excore AFD circuitry: such that it indicated'incore -

axial flux,.and to satisfy the surveillance requirements of TS  ;

fable 4.3- j. BwVS 1.3.4-1, " Rod Drop Time". This procedure was performed during i llay 21-24, 1990, prior to reactor critical..for all shutdown and control rods. The licensee used an automatic rod drop test system-and the rods were timed by computer. All rod drop times were less ,

than 2.7 seconds which met the TS requirement 4.1. a -l

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I k. 2BwVS 2.3.5-1, " Reactor Coolant System Flow Measurement." This procedure was performed on June 22-26, 1990 at about 97 satisfy TS 4.2.3.5. TheflowratecalculatIonswereper%RTP,toformed using i calorimetric data. The methodology, calculations, and results, were ,

adequate to verify that RCS flow rate met the acceptance criteri ,

i 1. 2Bw05 3.1.1-2, " Unit Two Power Range High Flux Setpoint Daily i ChannelCalibration(Calorimetric)." This procedure was used t t perform a channel calibration of the power range nuclear

instrumentation (PRNI) high flux setpoint daily when above 15%  !

RTP as required by TS' Table 4.3-1. A secondary side calorimetric was performed and the excore channel gains were adjusted to within ,

2% of the calculated power. The licensee used computer points and '!

calculational methods (computer) to perform the surveillance. The ins ector reviewed the calorimetrics completed on May 27 1990(14%- .

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RTP , and June 14, 1990 (49% RTP); and independently performed manual calculations on August 29, 1990 (100% RTP),usingrecorde and instrument data. The licensee's methodology and results were considered adequate, m. BwVS 1.1.1.2-1, " Core Reactivity Balance." This procedure was used to calculate the overall core reactivity balance and compare it to tne predicted values, as required by TS 4.1.1.1.2. This surveillance i was performed every 31 effective full power days (EFPD) to demonstrate

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that a reactivity anomaly did not exist (actual within 1000 pcm of predicted). The licensee normally used computer methods to perform- '

the calculation. The inspector reviewed the surveillances completed on June 26,1990(96% RTP), and July 25,1990(89% RTP);and inde RTP) pendently

, using performed manual the calculational method' calculations onlicensee's outlined in the August 29,1990(100% i procedure and data from BwCB-2.. The inspector noted that certain steps in the calculation could not be performed as written and needed clarification. The licensee agreed to. revise the procedure to correct these steps. No further concerns were'note BwVS 1.1.1.2-2, " Core Reactivity Balance Normalization," was performed -

on August 6, 1990, to renormalize the predicted equilibrium full  ;

power RCS boron concentration as a function of burnup (to correspond to actual core condition), prior to 60 EFPD, as required by TS 4.1.1.1.2. Figure 11 in DwCB-2 was updated on August 8, 1990,  ;

to reflect the new data, n. BwVS 500-4, " Initial Criticality. After Refueling and Nuclear Heating l Level." This arocedure was performed on May 25, 1990,- to achieve criticality su) sequent to core reload. For the initial critical, the licensee withdrew control rods to step 180 on control Bank D (CBD) and diluted to reactor critical. The inverse count rate ratio (ICRR) was tabulated every 10-15 minutes-during dilution i

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(approximately 60 gpm), and RCS sampics were taken during approach-to critical. 2BwGP 100-7, " Reference Reactivity Data' Calculation and Estimated Critical Condition Calculation " was performed on llay 24,1990, topredict.thecriticalboronconcentration. The predicted critica s condition was very close to the actua Bw05 1.1.1.1.c-1, "ECC Above Control Rod Insertion Limit Startup Surveillance," was also performed prior to critical to verify that TS 4.1.1.1.1.c was satisfie As a result of the concerns with predicting critical conditions identified ~at the B 50-455/90007(DRS))yronPlant(InspectionRe)ortNos.-50-454/90008(DR BraidwoodforpredIc.theinspector.reviewedtiemethodologyusedatting critic from the eight-fold count rate. The criticality documentation was reviewed and found acceptable for startups conducted for finit 1 (January 13 June 6, and August 13,1990) and Unit 2 (June 8 and June 9,1990). The inspector noted, however, that~BwGp 100-7 did not provide adequate'(detailed) direction for evaluating the estimated critical condition (ECC) based on the eight-fold count rate, and for determining that the difference between:the predicted critical condition and the ECC was:within the 500 pcm administrative limi The licensee had a major revision to the procedure drafted, and sent-to typing on September 4.1990.. The approval and implementation of-this revision siould adequately resolve the inspector's concer On October 21, 1990, the? licensee suspended a'startup and inserted-controlrodsonUnit1due,toanunexpecteddifference(approximately-750 pcm) between the ECC-(based on the eight-fold count rate) and the predicted critical. The inspector. held-discussions on October 30, 1990 (via tele-conference), with, licensee representatives regarding the startup attempt. According to the licensee, the core burnup was between middle-of-life-(liOL) and end-of-life (EOL), and an-t interpolation between the two rod worth curves (Unit 1 BwCB) was L performed for the predicted critical calculation. .The licensee

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investigation showed that.using-the 140L curves would have resulted in meeting the 500 pcm administrative criteria._ Further, the

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inaccuracies in the 2-dimensional computer methodology used at-Braidwood could have-contributed about'350 pcm error to the prediction. Additional administrative controls were implemented for the approach to critical. and the subsequent unit startup was

, successful. The licensee's actions were considered conservative, I and the inspector had no further concerns regarding the Unit 1 startup attempt and predicted critical calculation..

, o.- The licensee's procedures for obtaining flux maps of.the core.' included:

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l Bw0P 10-3, "Incore 140veable Detectors Flux liapping Procedure,":and BwvS 3.3.2-1, " Moveable Incore Detector's Operability Check L' Data y

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. . I from flux mapping were used for performing TS surveillances involving power distri

>ution limits, such as,(QPTR, andheatfluxhotchannelfactorFqz). NFDH,.

Flux maps peaking factor Fxy, were routinely i obtained monthly, and required stable reactor conditions for a >

rede l p(e.g.termined length

, load following of time, may dependent necessitate on prior stabilizing the reactor operation unit up to i 48hourspriortomappingthecore). The. inspector observed ,

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portions of the performance of flux mapping on August 29, 1990 '

(100%RTP) includ thefirstfewmaps.ingcompletionoftheprerequisitesandconducting j t

p. 2BwVS 2.2.2-1, " Heat Flux Hot Channel Factor Checkout Using Peaking ,

Factors." This procedure (along with a current flux map) was used >

for evaluating Fxy to determine if. Fc(z) met the requirements of TS l; 4.2.2. The surveillance was requirec to be performed every 311EFP BwVS 2.2.3-1, " Heat Flux Hot Channel Factor Verification,"'was .i performed when Fr.y exceeded the core limits to verify that the Fxy .!

margin was less than the Fq(z) margin remaining at that core heigh If Fq(z) exceeded the TS limits, then reactor )ower must be reduced <

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(and a LCO entered). The ins e completed on June 2 (30% RTP)pei io surveillancesRTP),during ar- reviewed andJune.16,1990(49% t i power ascension testing, ,

On 18,1990(1455 Fq(z)July (in the upper core region) by approximately. The j

0.45%. MWD /ItTU b licensee entered a LC0 and reduced power by 1% (to 98% RTP), in i accordance with the TS. The, licensee immediatel  :

corporate engineers (Nuc1 car Fuel Services, NFS)y contacted their and Westinghouse

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representatives for assistance in evaluating the anomaly. -Based on theevaluation(letterdatedJuly 19. 1990),:the licensee conducted an Onsite Review (OSR No.90-090) on July 20, 1990, and documented a change to the Braidwood Unit 2 Cycle 2 Core Operating Limits *

, Report. The. values for the Fxy. limits were revised (increased) tc l

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reflect the removal of an uncertainty factor (grid penalty. margin)-

deemed to be unnecessary. A 10 CFR 50.59-safety evaluation was i performed and the change'was approved. ~On July 20, 1990, with  !

reactor power stable at 98% RTP for 48-hours, the surveillance.was . ,

performed again. Using the revised limits, the licensee considered thesurveillancetobesuccessful(Fq(z)limitsnotexceeded),.and ,

exited the LC0 for TS 3.2.2.2. On July 26, 1990, thelicensee(NFS)~

determined that the tet.hnical basis used for the revised Fxy limits -

I wasincorrect.-AnOnssteReview(OSRNo.90-091)-washeld. .The  ;

data from:the July 20 flux map was reevaluated using the original' i Fxy limits and found to be acceptabl !

l r On August 17, 1990, the inspector held discussions with licensee ,

representatives, including' members of the plant nuclear engineering staff and NFS, to discuss root cause and corrective action regarding- ,

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thetechnicalerrors,andpossiblereaso'nsforFq(z)exceedingits

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i limit. Two factors which may'have. contributed to the faile .

surveillance on Jul 17, 1990, were reactor stability (the unit had 't been load following and that only 48 of'58 core locations had been :

traced (flux mapped . The apparent cause:of the technical. error was inadequate review by NFS, that _si Westinghouse and NFS used

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difference computer models. . The Westinghouse code compensated for the grid penalty factor, whereas, the code used by NFS required an input. A more detailed review could have identified the 1act that :

the penalty was required for both computer models. The licensee has-' *

implemented administrative flux map stability requirements which :

included specifying conditions required prior to performing a flux ;

map (e.g., curtailing load following maneuvers for at least 48-56 a hours prior to mapping). In' addition. the.next flux map was required ,

to be obtained in two week On August 2,1990(2094 MWD /MTV burnup), the licensee ~obtained the-next flux map and Fq(z) satisfied the TS.. However, fxy (up)er core region) exceeded the core limit. The required action for t11s condition was to perform additional flux maps. The licensee continued to obtain flux maps' at two-week intervals. The upper core :

Fxy exceeded the limit at the next flux map.at 2602 MWD /MT Both [

the upper and lower core'Fxy were less than the limit at 3174 >

MWD /MT For the next four flux. maps, the'last performed at 5406' '

11WD/MTV on October 24, 1990, the upper core Fxy was below the limit and continued on a downward trend. -However, the lower core Fxy exceeded the limit and was increasing above the limit. The licensee was closely monitoring the Fxy trends and the effect on the Fq(z) .i margin, and planned to continue obtaining flux maps every two weeks. Based on predictive analysis,-the licensee did not expect tne -l lower core Fxy to increase significantly over the next 1000-2000 ItWD/MTV core tournu Theaboveissues(technica1'errorandFq(z) limits)-wereconsidered 'I to be an open item in NRC Resident _' Inspection Reports No. 50-456/90013; No. 50-457/90016.. This open item will remain open pending:-  !

satisfactory Fxy results, and/or_ the assurance that the' Fxy margin-will not exceed the Fq(z) margin,in the lower core region; and HRC review of the licensee's investigation of the' technical error  :

regarding Fxy limit No violations, deviations, on.significant concerns were identifie A previously identified open item was addressed and will remain ope . Exit Meeting The-inspector met with the-licensee _ igresentatives (denoted 'in paragraph .1). I o

on September 13, 1990. The inspector summarized _the scope and findings 4 (

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of the inspection and the licensee' acknowledged the statements'madeLby- '!

the inspector. The inspector also' discussed the likely informational. ' '

content of the inspection report with regard to documents or processes; reviewed by the inspector during the inspection and the licensee did.not :!

identify any such documents / processes as proprietar '

Furtherdiscussionswereheld(viatele-conference):withlicenseeL  !

representatives regarding the open item and the Unit 1 startup attempt: . !

on October 21, 1990. The inspection period ended on.on October 30, 199 i

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