ML17328A027

LER 89-009-00:on 890331,discrepancy Noted in Westinghouse P-250 Computer Calculated Thermal Power Value Which Could Lead to Exceeding Rated Thermal Power.Caused by Not Including blowdown-mass Enthalpy term.W/890501 Ltr

ML17328A027
Person / Time
Site:	Cook
Issue date:	05/01/1989
From:	Postlewait T, Will Smith INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-009, LER-89-9, NUDOCS 8905110124
Download: ML17328A027 (7)

Text

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ACCESSION NBR:8905110124 DOC.DATE: 89/05/01 NOTARIZED: NO DOCKET g FACIL:50-316 Donald C. Cook Nuclear Power Plant, Unit 2, Indiana & 05000316 AUTH. NAME AUTHOR AFFILIATION POSTLEWAIT,T.K. Indiana Michigan Power Co. (formerly Indiana & Michigan Ele SMITH,W.G; Indiana Michigan Power Co. (formerly Indiana & Michigan Ele RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 89-009-00:on 890331,rated thermal power exceeded due to computer program error.

W/8 ltr..

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES RECIPIENT COPIES RECIPIENT COPIES A.

ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD3-1 LA 1 1 PD3-1 PD .1 1 D STANG,J 1 1 INTERNAL: ACRS MICHELSON ACRS WYLIE 1,

1 1

1 ACRS MOELLER AEOD/DOA 2

1 2

1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DS P 2 2 DEDRO 1 1 IRM/DCTS/DAB 1 1 NRR/DEST/ADE 8H 1 1 NRR/DEST/ADS 7E 1 0 NRR/DEST/CEB 8H 1 1 NRR/DEST/ESB 8D 1 . 1 NRR/DEST/ICSB 7 1 1 NRR/DEST/MEB 9H 1 . 1 NRR/DEST/MTB 9H .1 1 NRR/DEST/PSB 8D 1 1 NRR/DEST/RSB 8E 1 1 NRR/DEST/SGB 8D 1 1 NRR/DLPQ/HFB 10 1 1 NRR/DLPQ/QAB 10 1 1 NRR/DOEA/EAB 11 1 1 NRR/DREP/RPB 10 2 2 NRR/iBR . SIB 9A

- 1 1 NUDOCS-ABSTRACT 1 1 02 1 1 RES/DSIR/EIB 1 1 RES/DSR/PRAB 1 1 RGN3 FILE 01 1 1 R

EXTERNAL: EG&G WILLIAMS,S 4 4 FORD BLDG HOY I A 1 1 L ST LOBBY WARD 1 1 LPDR 1 1 NRC PDR 1 1 NSIC MAYS,G 1 1 NSIC MURPHY,G.A 1 1 D S

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NRC Form 366 US. NUCLEAR REOULATORY COIMIISSION (94)3)

APPROVED OMB NO. 31600104 EXPIRESI 6/31/SB LICENSEE EVENT REPORT (LER)

FACILITY NAME (II DOCKET NUMBER (2)

D. C. Cook Nuclear Plant Unit Two o 5 o o o3 16.>OFO 5 TITLE (4)

Rated Thermal Power Exceeded on Unit Two Due .to Computer Program Error EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED IS)

'E.AR SEQUENTIAL BEY+~ DAY YEAR FACILITYNAMES DOCKET NUMBER(S)

MONTH DAY YEAR NUMBER +2 NVMBEII MONTH ml:

Cook Plant 0 5 0 0 0 3 1 6 0 3 3 1 8 9 8 9 0 0 9 0 0 05 01 8 9 0 5 0 0 0 THIS REPORT IS SUBMITTED PURSUANT T 0 THE REOUIREMENTS OF 10 cFR (I; (Coact! one or morr of the Iollo>>inc) (11 OPERATINQ MODE (9) 20.402(O) 20.406(c) 60.73I ~ l(2I(N) 73.71(II)

POWER 20.405(a)it)(ll SOW(c)(II 50.73(al(2l(rl 73.71(c) 1 0 0 '20.406( ~ )(I)(BI 50.36(c) (2) 60.73(al(2)(rB) OTHER ISpeclly In AOrtioct priory cnd ln Trot, Hi)C Form 20.406(el(1) IIIII 50.73(a) (2((l) 50.73(c) (2)(rllll(A) SSBAI 20AOS(el(1)(lrl 50.73(el(2)DII 50.73(a) (2)(rlB)(B) 20.406( ~ I (1)(r) 50.73(a) (2) (III) 50,73(a) (2)(el LICENSEE CON'TAC'7 FOR THIS LER (12I NAME TELEPHONE NUMBER T. K. Postlewait AREA COOK Technical Engineering Superintendent COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) 616465-5901 MANUFAC. MANUFAC. FPORTABL tgic)IIN PI" coi

'co CAUSE SYSTEM COMPONENT TURER TO NpROS CAUSE SYSTEM COMPONENT TURER TO NPRDS I(4;PQ.NI!2!

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SUPPLEMENTAL REPORT EXPFCTED (14) MONTH DAY YEAR EXPECTED SUBMISSION DATE (16)

YES Ill yer, cor>>Plr to EXPECTED S (IB4IISSIDH DA TEI NO ABSTRACT ILimlt to lc00 rpecer, I e., epprooimetely liftren rlncle.opere typr>>ritten linrU (15)

On March 31, 1989, with Unie Two operating at 100 percent reactor thermal power (Unit One in refueling), it was suspected that a discrepancy exist'ed if in the Westinghouse P-250 computer calculated thermal power value, which, true, would lead to exceeding Rated Thermal Power. Investigation revealed the blowdown-mass enthalpy term (m h ) was not included in the Thermal Output Program. Assumed worst case analysis indicated a potential 1.8 percent difference between the P-250 calculated and actual thermal power.

This took into account plant conditions in which maximum computer program code error existed and assumed actual blowdown flow was 50 percent of t: he blowdown compensation (constants). Actual detailed evaluation has confirmed a 0.81 percent error fcr Unit Two. It is expected that detailed evaluation on Unit One, following startup, will similarly reduce the actual power deviation. It should be noted that, although the errors in the P-250 program have existed since initial startup, the Cook units have been administratively restricted to 90 and 80 percent power, respectively, for essentially the entire cycle of the existing fuel. Unit Two is now operating conservatively using no compensation for blowdown flow (actual reactor thermal power is less than P-250 calculated thermal power). Prior to Unit One seartup, changes will be made to ensure it will operate conservatively. Enhancement to the P-250 computer program is being pursued.

~rE2-8905110124 890501 PDR ADOCK 05000 16 NRC Form 366 (9 63)

S PDC

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION (943)

LICENSEE EVENT REPORT ILER) TEXT CONTINUATION APPROVEO OMS NO. 3)50&104 EXPIRES: 8/31/88 FACILITY NAME (11 OOCKET NUMBER (ll LER NUMSER (6) PAGE (3)

SEOUSNTIAL R5j REVISION NUMSSR IV~. NUMSSR D. C. Cook Nuclear Plant Unit Two 0 5 0 0 0 3 1 6 8 9 0 0 9 0,0 0 2 OF 0 5 TEXt /// more <<>>oe /e oerr))e L rree erreo'o>>/ HRC %%drrrr 368l3/ (IT)

Conditions Prior To Occurrence Unit One in Mode 6 (Refueling)

Unit Two in Mode 1 (Power Operation) at 100X power Descri tion of Event On March 31, 1989, with Unit Two operating at 100 percent reactor therm'al power (Unit One shut down for refueling), it was suspected that a discrepancy existed in the Westinghouse P-250 computer (EIIS/ID) calculated thermal power value, which, if true, would lead to exceeding Rated Thermal Power, when operating at calculated 100 percent Rated Thermal Power. The unit had been operating at an administrative limit of 80 percent reactor thermal power, as a steam generator conservation measure, for approximately four years and was recently returned to 100 percent reactor thermal power. The steam generator startup flashtank (EIIS/WI-TK) had been in operation for an extended amount of time since unit startup on March 17, 1989. At 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br />, steam generator blowdown was removed from startup flashtank operation. Following isolation of blowdown flow and the removal of the P-250 computer compensation (constants) (mbd) for blowdown, the licensed Control Room Reactor Operators noticed an increase in the P-250 calculated thermal power of approximately 1 percent with no indicated change to NI, power. Operations immediately reduced reactor power until the cause of the P-250 calculated reactor thermal power increase could be found.

To operate conservatively, the Unit Two procedure for placing/removing steam generator blowdown in/out of service was modified (at approximately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on March 31, 1989) such that no feedwater flow compensation would be made for blowdown (i.e., actual reactor thermal power will always be less than P<<250 calculated reactor thermal power while blowdown is in service).

On April 14, 1989, investigation revealed a possible deficiency with the P-250 Thermal Output Program. On April 21, 1989, following review of the situation by Westinghouse, it was verified that the blowdown-mass enthalpy term (m dh d) was not included in the Thermal Output Program Code. This program error has existed since initial criticality in both Unit One and Unit Two. It affects P-250 calculated reactor thermal power nonconservatively whenever blowdown (either the startup or normal flashtank operation) is in service. The errors caused by this missing term are 35.1 MWt or 1.08 percent of rated thermal power (Unit One startup flashtank), 6.0 MWt or 0.18 percent of rated thermal power (Unit One normal flashtank), 27.5 MWt or 0.81 percent of rated thermal power (Unit Two startup flashtank) and 7.3 MWt or 0.21 percent or rated thermal power (Unit Two normal flashtank).

~0 6 CPOI 19SS S)O NRC FORM SSSA IO II1'I

NRC Form 3$ 8A U.S. NUCLEAR REOULATORY COMMISSION (943)

LICENSEE EVENT REPORT ILER) TEXT CONTINUATION APPROVED OMS NO. 3I50&(04 EXPIRES: 8/31/88 FACILITY NAME (1) OOCKET NUMSER (2) LER NUMSER (8) PACE (3)

SEOUENTIAl ~re'EVISION YEAR @i NUMOER IO@ NUMSER D. C. Cook Nuclear Plant Unit TEXT ///moro Two Fico /r ror)rr(IFIL Irro ~ H/IC Fomr 38((AO) (17) 0 5 0 0 0 3 1 6 8 9 0 0 9 0 0 0 3 OF 0 5 Descri tion of Event, Continued Real SGTO (mf mbd)h t mf hf + mbdhbd Error mbdhbd SGTO m Steam Generator Thermal Output m mass of feedwater fw m mass of blowdown bd h

stm enthalpy of steam h

fw enthalpy of feedwater h enthalpy of blowdown The MWt power increase the operators noted on the March 31, 1989 incident was approximately one percent. This corresponds to the 0.81 percent power error for Unit Two startup flashtank operation caused by the missing blowdown-mass enthalpy term.

Cause of Event Investigation revealed the blowdown-mass enthalpy term was not included in the Thermal Output Program. This Thermal Output Program was supplied by Westinghouse prior to initial criticality. The program code was reviewed by Westinghouse and verified deficient on April 21, 1989.

Analysis of Event The Unit Two accident analyses were performed with consideration of the fact that actual core power may deviate from Rated Thermal Power. This means the reactor was assumed to be at 102 percent of Rated Thermal Power, unless the limiting case was a lower power level or a spectrum of powers was analyzed.

Similar 2 percent allowances are made for the Unit One analyses. For the Unit One analyses performed with the Westinghouse Improved Thermal Design Procedure, however, the 2 percent allowance is built into the DNBR limit for DNBR transients. The 2 percent allowance is intended to cover calorimetric error or short-term drifts in power.

'C.S ~ CPOI 1988 S20-189 UIOO I' NRC FORM 34OA Io FTI

NRC Form 3ddA U.S. NUCLEAR REOULATORY COMMISSION (343)

LICENSEE EVENT REPORT ILER) TEXT CONTINUATION APPROVED OMB NO. 319)WIOE EXPIRES: B/31/BB FACILITY NAME (1) DOCK ET NUMBE R Il) LER NUMBER (S) PACE (3)

YEAR Na Yam SEOVENTIAL NVMdER I REVISION NVM ER D. C. Cook Nuclear Plant Unit TEXT ///moro Two Z>>co ie seRrsros/, u>> ~ /VRC %%dnrr 3//EA's/ (IT) o 5 o o o 3 1 6 8 9 0 0 9 0 0 04o"05 Anal sis of Event, Continued The largest P-250 calculated reactor thermal power deviation caused by the missing blowdown-mass enthalpy term would have occurred on Unit One during startup flashtank operation. An analysis of the 'assumed worst case, which took into account actual blowdown flow being 50 percent of the P-250 blowdown compensation (constants), shows a 58.6 MWt or 1.8 percent (Unit One) and 46.0 MMt or 1.3 percent (Unit Two) difference between actual and P-250 calculated thermal power. Actual deviations of calculated thermal power on Unit Two confirm the 0.81 percent error due to the missing m dh d term.

Therefore, no significant error in md is believed to exist on nit Two.

There is no reason to believe that tVie 1.8 percent worst case error for Unit One would not similarly be reduced (to 1.08 percent) following verification of the blowdown flow computer constants upon return to service of the unit.

This maximum power deviation, due to blowdown error, of 1.8 percent of Rated Thermal Power is bounded by the 2 percent allowance in the accident analysis and therefore no significant threat to public health and safety existed.

The condition is determined to be reportable per 10 CFR 50.73 (a)(2)(i)(B),

as operation prohibited by the plant's Technical Specifications (T/S).

(T/S 3.2.6 requires power to be less than or equal to 100 percent power.

License conditions C(1) clarifies this to be a ~stead state power of 100 percent). The report is considered necessary only because of literal interpretation of the T/S and license requirements. The blowdown error appears to be an unanticipated systematic error which takes us out of literal compliance. The safety analysis assumed a 2 percent error in steady state reactor power to account for calorimetric errors. We believe the intent of the T/S was to ensure steady state reactor power did not exceed 100 percent power as indicated to the operators, with the 2 percent allowance accounting for deviations between the indicated and actual power.

Fuel cycle burnup tolerances were also affected. For Unit Two, the effect of the burnup was within the cycle burnup tolerance provided by the fuel vendor. For Unit One,, the effect on burnup is being reviewed by the fuel vendor prior to unit startup.

~ II.S. CPOr Iddd-33(I-Sdd trddff NRC FORM SSEA 14R31

NRC Form 388A US. NUCLEAR REOULATORY COMMISSION (843)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMS NO. 3150&108 EXPIRES: 8/31/88 FACILITY NAME (I) DOCKET NUMSER (ll LE R NUM8 E R (8) PACE (3)

YEAR 5EOVENTIAL REVISION D. C. Cook Nuclear Plant NVM ER NVMEER Unit TEXT /// more Foeoe Two ir /eqr/irerL Iree ~ H/IC Forrrr 38848/ ()7) o s o o o 3 1 6 8 9 0 0 9 0 0 0 5 DF0 5 Corrective Action Immediate compensating action for Unit Two was completed on March 31, 1989, via a procedure modification. The procedure for placing/removing steam generator blowdown in/out of service was modified such that no compensation would be made for blowdown whenever it is in service. Corresponding modifications will be made to the Unit One procedure prior to unit startup.

This modification conservatively bounds both of the potential sources of error (i.e., the missing blowdown-mass enthalpy term and the possible non<<conservative blowdow'n compensation (constants)). However, the procedure modification causes the units to operate at less than 100 percent actual Rated Thermal Power when blowdown is in service. We are investigating possible enhancements to the P-250 computer code. These enhancements would allow the units to operate at actual full Rated Thermal Power with blowdown in service.

Failed Com onent Identification None.

Previous Similar Events None.

NRC FORM 388A

'0.8. CPOI 1888-538-$ 88 IIPIIl(I lo II3)

Indiana Michigan Power Company Cook Nuclear Plant P.O, Box 458 Bridgman. Ml 49106 616 465 5901 INDlANA NICHlGiAN POWER May 1, 1989 United States Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Operating License DPR-74 Docket No. 50-316 Document Control Manager:

In accordance with the criteria established by 10 CFR 50.73 entitled Licensee Event Re ortin S stem, the following report is being submitted:

89-009-00 Sincerely, W. G. Smith, Jr.

Plant Manager WGS:clw Attachment cc: D. H. Williams, Jr.

A. B. Davis, Region M. P. Alexich III P. A. Barrett J. E. Borggren R. F. Kroeger NRC Resident Inspector J. F. Stang, NRC R. C. Callen G. Charnoff, Esa.

Dottie Sherman, ANI Library D. Hahn INPO PNSRC A. A. Blind S. J. Brewer/B. P. Lauzau