ML20064E438

/99X-1 on 780413:with All Rods Out at Beginning of Core Life,Hot Zero Pwr Moderator Temp Coefficient Revealed It Was More Positive than 0 Delta K/K/F in Tech Spec,Due to Positive Mtc for the all-rods-out Configuration

ML20064E438
Person / Time
Site:	North Anna
Issue date:	11/13/1978
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML20064E436	List: ML20064E435 ML20064E438 ML20064E442
References
LER-78-026-99X, LER-78-26-99X, NUDOCS 7811170184
Download: ML20064E438 (3)

Text

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- LICENSEE EVENT REPORT

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• Updata Report - Previous Report Dats 4-21-78 i CONTROL BLOCK: l l l l l l l (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) li l 6 l@

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60 61 DOCKET NUM8ER 63 69 EVENT OATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h I

5_[2j 0 l Measurement of all rods out, beginnina of core life. hot zero power moderator l I

o , 3 , ; temperature coefficient (MTC) revealed it was more positive than 0 AK/K/ F as l l jo , I i ; stated in T.S. 3.1.1.4. A value of +1.126 AK/K/ f w1s_ obtained. The health and l I 10151 I safety nf the opneral nnblic were not affected.

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33 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS I

Ii I011Startup physics testing revealed the presence of a positive MTC for the all rods out I

i i Iconfiguration. Rod withdrawal limits were instituted to restore a negative MTC.

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f I al l I-i 4 I so 7 0 9 OTHER STATUS 015 Y DISCOVERY OESCRIPTION

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Update R: pert - Previous R:p;rt Data 4-21-78 1 9

Virginia Electric and Power Company North Anna Power Station, Unit No. 1

Attachment:

Page 1 of 2 Docket No. 50-338 Report No. LER 78-026/99X-1 ,

Positive Moderator Coefficient On 4/13/78, analysis of startup physics testing data revealed that a positive moderator temperature coefficient (MTC) was present at the all rods withdrawn, beginning of core life, hot zero thermal power condition. The finalized data indicated an isothermal temperature coefficient of -0.979 pcm/ F, which converts to an MTC of +1.126 pcm/*F when corrected for the Doppler Contribution

(-2.105 pcm/*F), was present with an RCS boron concentration of 1322 ppm. The rod withdrawal limits illustrated by the attached figure have been instituted. '

It is estimated that a core burnup of 3000 MWD /MTU will be required to restore the MTC within its limits.

' The withdrawal limits will apply throughout the entire first cycle of the "-

m-unit or until a negative MTC for the ARO configuration is verified by measurement.

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