ML20010A533

Forwards LER 81-016/03L-0.Detailed Event Analysis Submitted

ML20010A533
Person / Time
Site:	Cooper
Issue date:	07/09/1981
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20010A534	List: ML20010A533 ML20010A539
References
CNSS810408, NUDOCS 8108110520
Download: ML20010A533 (2)

Text

_ - _ - - - _ - - - - - - _ -

l' .

a o COOPER NUCLE AR ST ATION xb;_ Nebraska Public Power District "A"EnTM%;"'si.^T^

-. =- ==:=-- = =:= a n =_=--_=====---===-=n l

CNSS810408 July 9, 1981 l

(

l 6- p

~ ' -\

Mr. K. V. Seyfrit, Director ~g U.S. Nncicar Regulatory Commission Q-gjh c

Office of Inspection and Enforcement Q Regica IV b ,1 2.

611 Ryan Plaza Drive Suite 1000 dp # ^3' Arlington, Texas 76011 .

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.1 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on June 10, 1981. A licensee event report form is also enclosed.

Report No.: 50-298-81-16 Report Date: July 9, 1981 Occurrence Date: June 10, 1981 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

A condition occurred which resulted in operation with a Reactor Protection System (RPS) instrument setting less conservative than those established in Sections 2.1.A.l.a and 2.1.A.l.d of the Tech-nical Specificatio1s.

Conditions Prior to Occurrance:

The reactor was operating at 61% of rated thermal power during a startup from refueling.

Description of Occurrence:

The core thermal power calculation was found to be incorrect due to an invalid feedwater flow input to the process computa.r.

Designation of Appaient Cause of Occurrence:

The apparent cause of the occurrence was personnel error. 76)~A

.5

/ i 8108110520 810709 PDR ADOCK 05000298 S PDR U 2[

)

Mr. K. V. Seyfrit July 9, 1981 Page 2.

Analysis of Occurrence:

The plant process computer is used to determino compliance with thermal limits as stated in the Technical Specifications. The thermal limit calculations depend largely upon a core heat balance (megawatts thermal reactor output) which is in turn altost totally a function of the feedwater flos signals to the process computer.

During startup following the Spring 1981 refueling outage, the feedwater flow value in the process computer was found to be in error. Investigation revealed the feedwater flow transmitter millivolt signals were not being converted correctly to a flow reading by the process computer. During the outage, the range of the feedwater flow transmitters was changed from o + 6 X 10 6 lb/hr to O + 7 X 106 lb/hr. The conversion coefficients were changed accordingly. After the error in core thermal power was discovered, it was found thac the conversion coefficient had changed back to the old values for the 0 + 6 X 10geenlb/hrdynamically ranpe.

The conversion coefficient base values used by the computer program that dynamically changes the coef ficients (based upon feedwater '

temperature and density effects) had not been changed. As a re-sult, when this program ran the first time, the conversion coef-ficients were set to the old incorrees values. This problem was attributed to personnel error.

The feedwater flow value in the process computer was incorrect for approximately 61 hours7.060185e-4 days <br />0.0169 hours <br />1.008598e-4 weeks <br />2.32105e-5 months <br />. The thermal power calculation erroneously indicated 53% of rated power when it actually was 61%. This con-dition was discovered at the maximum power level attained subse-quent to reectse etartup. Since the thermal limits were acceptable under conditions of maximum possible error, evaluation indicates that all thermal limits were acceptable during the period this condition existed. This occurrence had no adverse effect on the public health and safety. This event is not repetitive.

Corrective Action:

The feedwater flow conversion coefficients in the process computer were corrected. The plant personnel involved have thoroughly ,

reviewed this error and how it occurred. No further action is necessary as the change to the feedwater flow transmitter range is a one time change.

Sincerely,

&Lw b.

L. C. Lessor Station Superintendent Cooper Nuclear Station i LCL:cg Attach.

L ~j