ML20012E668

LER 90-006-00:on 900227,plant Operation in Excess of Licensing Basis.Caused by Failure of Computer to Synchronize File Addresses in Task 3D.Heat Balance Calculations Reverified Using Data from Plant Variable Computer

ML20012E668
Person / Time
Site:	Beaver Valley
Issue date:	03/29/1990
From:	Noonan T DUQUESNE LIGHT CO.
To:
References
LER-90-006, LER-90-6, ND3MNO:2045, NUDOCS 9004060079
Download: ML20012E668 (6)

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i L March 29, 1990 i ND3MNO:2045 l Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-64 LER 90-006-00 United States Nuclear Regulatory Commission Doctiment Control Desk Washington, DC 20555 Gentlemen In accordance with Appendix A Beaver Valley Technical Specifications, the following rev1 sed Licensee Event Report is submitted:

i LER 90-006-00, 10 CFR 50.73.a.2.ii.B, " Plant Operation in Excess of Licensing Basis".

Very truly yours, WY T. P. Noonan General Manager Nuclear Operations s1

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March 29, 1990

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cc Mr.. William T. Russell '

Regional Administrator United States Nuclear Regulatory Commission l Region 1 475 Allendale Road i King of Prussia, PA 19406  !

C. A. Roteck, Ohio Edison 1

Mr. Peter Tam,' BVPS Licensing Project Manager-  :

United States Nuclear Regulatory Commission  !

Washington, DC 20555  ;

J. Beall, Nuclear Regulatory Commission, l BVPS Senior Resident Inspector i Dave Amerine  !

Centerior Energy  !

6200 Oak Tree Blvd.  !

Independence, Ohio 44101  :

INPO. Records Center- i Suite 1500 I 1100 circle 75 Parkway  ;

Atlanta, GA 30339 '

G. E. Muckle, Factory Mutual Engineering, Pittsburgh Mr. J.-N..Steinmetz, Operating Plant Projects Manager

!: Mid Atlantic Area l' Westinghouse Electric Corporation Energy Systems Service Division Box 355 i Pittsburgh, PA 15230 -j American Nuclear Insurers c/o Dottie Sherman, ANI Library i The Exchange Suite 245  !

e 270 Farmington Avenue Farmington, CT 06032  :

Mr. Richard Janati l Department of Environmental Resources  !

P. O. Box.2063 '

. 16th Floor, Fulton Building Harrisburg, PA 17120 Director, Safety Evaluation & Control Virginia Electric & Power Co.

P.O. Box 26666 One James River Plaza i Richmond, VA 23261 i, if

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l l l On 2/27/90 at 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />, Operations personnel performed a daily heat balance calculation (HBC) which showed a calculated reacter power of 2663.3 megawatts thermal (MWt), or 100.4%. Turbine load was immediately reduced until reactor power was less than 2652 MWt. An investigation was initiated, since no reactor power changes were performed within the last 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. A computer program (Task 3D), that performs averaging calculations used in the HBC, was found to have aborted on 2/18/90. This 1 program retained the last calculated value until it was updated on 2/26/90. All HBCs performed from 2/18/90 through 2/27/90 l

were invalid utilizing the computer values. The HBC parameters affected were steam generator feedwater flow, pressure and steam flow for all three loops. The cause for the aborted computer program was internal error in data acquisition. Operations c personnel have been instructed to independently verify computer l values against control room instrumentation. There were no  ;

safety implications. A review of thermal output, utilizing data  ;

from an independent computer system, showed plant operation at '

100.4%. This is below the evaluation contained in the Updated Final Safety Analysis Report, Section 3.4.3.4.1, which discusses i steady state operation at 101% reactor power and concludes that l core safety limits are not exceeded.

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010 0l2 0' 0 14 DESCRIPTION On 2/27/90 at 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />, Operations personnel performed a daily heat balance calculation which showed a calculated reactor power of 2663.3 megawatts thermal (MWt), or 100.4%. Turbino load was immediately reduced until reactor power was less than 2652 MWt. An investi this discropancy, gation was initiated to determine the cause ofsince no reactor power within the last 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. This investigation determined that a computer program (Task 3D " Average and Integrate"), that performs averaging ca)culations used in the heat balance calculation, wan found to have aborted on 2/18/90. This program retained the last eniculated value until it was updated at 1302 hours0.0151 days <br />0.362 hours <br />0.00215 weeks <br />4.95411e-4 months <br /> on 2/26/90. All heat balance calculations performed from 2/18/90 through 2/27/90 were invalid utilizing the computer calculated average values. The heat balance ca3culation paremeters affceted were steam generator feedwater flow pressure and steam flow for all three loops. Additiona$

averaging parameters not used in the heat balance calculation were also affected. None of those computer parameters are used for Technical Specification surveillanco verifications. The axial flux difference (AFD) alarm during this time period was also inoperable as this computer program also provides average values of axial flux difference.

CAUSE The cause for this event, as determined by the computer engineer was a failure of the computer to synchronize file addresses, in i Task 3D, between two files, prompting the cot.puter to abort the task. This type of computer problem is not readily detectable by the operators because there are no error messages or computer prompts displayed as a result of an aborted program at the operators computer console. Reactor power was raised above 100%

due to two adjustments of the excore nuclear instrumentation. i Those adjustmonts, performed on 2/19/90 and 2/24/90, reduced the excore nuclear instrumentation indication downward on each occasion (0.3% on 2/19/90 and 0.5% on 2/24/90). A review of plant thermal output for each of these occasions, utilizing an

' independent computer system, showed actual power to be less than 100%. Subsequently, when reactor power was increased on each occasion to the 100% indicated value, this resulted in a  ;

i cumulative effect of increasing actual power. This offect was ,

not identified until the performance of a heat balance calculation performed on 2/27/90, after the computer was rebooted on 2/26/90. A review of the independent computer -

i, system, showed actual power to be greater than 100% (100.4%) ,

from 0145 hours0.00168 days <br />0.0403 hours <br />2.397487e-4 weeks <br />5.51725e-5 months <br /> on 2/26/90 to 0130 hours0.0015 days <br />0.0361 hours <br />2.149471e-4 weeks <br />4.9465e-5 months <br /> on 2/27/90.

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! CORRECTIVE ACTIO11S The following corrective actions have boon tahon as a result of this event

1. All heat balance calculations performed during the tino period from 2/10/90 through 2/27/90, were roverifiod using data f rom the Plant Variable Computer (PVC) ,

which receives information independently from the plant computer. These verifications showed thermal output greater than 100% for the timo period of 2/26/90 0145 hours0.00168 days <br />0.0403 hours <br />2.397487e-4 weeks <br />5.51725e-5 months <br /> to 2/37/90 0130 hours0.0015 days <br />0.0361 hours <br />2.149471e-4 weeks <br />4.9465e-5 months <br />.

2. A review of Axial riux Differenco values, recorded by the operator using control board indicators, for the time period from 2/18/90 through 2/27/90 was porformed. This review showed that axial flux difference was within the required band the entire time period.

3. Operations personnel have boon provided with administrativo guidanco requiring a verification that plant computer heat balance parameters are responding to statistical variations by observing those values against control room indications.

4. A review of reactor coolant system gross activity samples,ities abnormal were found.for the time period, was performed and no

5. Operations personnel have been instructed to verify heat balance calculations utilizing independent parameters whenever the excoro nuclear instrumentation indication is adjusted in a downward (indication lowerod) manner.

PREVIOUS OCCURRENCES Thero have boon no previously reported events of this type. A i review of the computer engineers log showed aborted computer programs on three occasions since February 1987. Task 3D van found to have aborted on 5/1/09, however, thoro woro no operational concerns as the plant had been operating at 90%

since 4/17/09, as part of a fuel oxtension ovelution in support of the upcoming seventh Rofueling outago.

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REEQEIABILITY This event is being reported in accordance with 10 CTR 50.73.a.2.ii.B. as an event that is outside the Licensing basis.

SAFETY IMPLICATIONS There were no safety, imp.ications as'a result of this event. A review of reactor coolant system gross activity sampics, for the time period, was performed and no abnormalities were found indicative of potential fuci damage. The Updated Final Safety Analysis Section 3.4.3.4.1, discusses steady state operation Report,ious at var power levels to assess the core thermal design to determine the maximum heat removal ca flow subchannels. This included testing at 101%pability reactor power. in all This testing showed that the core safety limits, as presented in the Technical Specifications, are not exceeded. Additionally, operation at 1024, above the design rating of 2652 MWt, has been assumed and evaluated for various operational transients in Sections 14.1.7, 14.1.8, 14.2.5, 14.2.6 and 14.3 of the Updated Final Safety Analysis Report. These evaluations concluded that there were no safety implications resulting for these events.

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