ML20063G090
| ML20063G090 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 07/23/1982 |
| From: | Dixon O SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8207280123 | |
| Download: ML20063G090 (8) | |
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SouYH CAROLINA ELECTRIC & GAS COMPANY post oerica som ve4 Cotuhemia. south CanoWNA 29218 O. W. DixoN. dR.
v.ca Paes or%v July 23, 1982 Nue... o.....o~s Mr. Harold R. Dentcn, Director Office of Nuclear mactor mgulaticn U. S. Nuclear Regulatory Comnissicn Washingtcn, D. C.
20555
Subject:
Virgil C. Sunrner Nuclear Staticn Docket No. 50/395 Technical Specificaticns
Dear Mr. Dentcn:
In the Proof md Review Cbpy of the Technical Spcificaticns for the Virgil C. Sunner Nuclear Staticn, Surveillance 4.3.1.1 requires that an incore/excore calibraticn be performed every 92 calmdar days. It is requested that this surveillance frequency be changed to 92 Effective Full Power Days (EFPD). Since the prpose of this surveillance requiremmt is to account for the effects, if any, of fuel depleticn cn the excare pwer range detectors, the fregumcy of the calibraticn should be based cn fuel burnup rather thm calendar days. Mis would be ccnsistmt with the requirenents in Secticn 3/4.2, Ibwer Distributicn Limits, which utilize EFFD to accomt for variaticns in care physics grameters.
%e following discussicn is Irovided to support our psiticn that a surveillance frequency of 92 EFPD is justified. he following references are the technical bases for this discussicn:
1.
Virgil C. Smmer Nuclear Staticn, Technical Specificaticns.
2.
Excore Detector Recalibraticn, Using Quarter-Core Flux Map, R. A.
Kerr, June 1976, NCAP-8648, Ncn-ProIrietary.
3.
Axial Xmcn Transient Tests at the Ibchester Gas & Electric Reactor, J. C. Ice, Jme 1971, NCAP-7964, Ncn-Pro 1rietary.
4.
Virgil C. Suntner Nuclear Staticn, FSAR, Qiapter 4.3.
%e objective of the incore/excore calibraticn is to develop a relaticnship betwem core axial offset md the axial offset as measured by the execre pwer range detectors.
(See Attachment I - Definiticns). Mis is acccmplished by initiaticn of m axial xmcn perturbaticn. %e intet is to gcnerate various axial flux shapes which will occur during normal and transimt opraticns. As core axial flux shap changes during the oscillaticn, axial offset is measured by the leveable Incore Detector System 80 00 9207280123 820723 PDR ADOCK 05000395 A
' Mr. Dmtcn July 23, 1982 j
Page 2 1
(MIDS) m d the excore power rmge detectors. A typical test seque1ce is depicted cn Attachmmt II.
A correlaticn is derived betwest care axial 1
offset, as determined by MIDS, and each excare power rmge detector. In example of the incore/excare correlaticn is treseited cn Attachmmt III. mis relaticnship is thm employed in calibraticn of the excore power range top md bottm detector isolaticn amplifiers and the axial offset emptnent of the calculated cuertemperature delta T reactor trip setpoint.
Deviaticn in axial offset, as measured by the excare power range detectors, from core axial offset is attributable to instrmentaticn drift md variaticn in the incore/excare relaticnship. It cm be demcnstrated that these comptnents which lead to axial offset errar are separable. Instrummt drift is addressed during normal channel calibraticn as specified in Technical Specificaticn 4.3.1.1. md is accomted for in the overtemperature delta T instremtaticn errar malysis. %e tacit assmpticn in the calibraticn is that the incare/excore relaticnship has not changed. B us, any instrumeit errar is zerced during the calibraticn md axial offset (excore) will agree with axial offset (incare). However, if the incore/excore relationship has changed, thm axial offset, as measured by excare power range detectors, will not agree with core axial offset after the calibraticn. %us, the effects which alter the incore/excare relaticnship are not instrummt related, but depmdelt uptn variaticns of care rhysics grameters.
An alteraticn in the incare/excare correlaticn is dm to neutrcn flux redistributicn in the radial md axial directicn md the associated change in sptial relaticnship with the excare pwer range detectors. %is Erocess occurs as a result of fuel depleticn aid has been dem:nstrated to be slowly varying with core burnup.
Wo tests were ocnducted at the Ibchester Gas md Electric lbact;r (Ref. 3) as prt of a pogram to demcnstrate that the fuel depleticn effects do not cmgomise the ability to ntnitor care power distributicn prameters with the excore nuclear detectors. Se tests were ccnducted at 1550 megawatt days pr metric tcnne uranium (WD/MIU) md 7700 WD/MIU, enploying the technique of axial xeicn perturbaticn to geierate axial flux redistributicn.
As demcnstrated cn Attachmmt IV, the excore detectors were adequate to mmitar axial pwer distributicns in a depleted core. As demcnstrated by the same attachmmt, axial offset as gedicted by the excare power range detectors did not vary nore than 1%, which is well within the 3% limit which bounds the safety malysis.
%e above test and operating experience at other plants dertrnstrate the capbility of the excore pwer range detectors to accurately measure axial offset. We have discussed the frequelcy of performing the incare/excore calibraticn with our NSSS vmdar and Westinghouse reccmmmds a calibraticn priod of cnce every 92 EFPD.
Mr. Dmtm July 23, 1982 Page 3
%e incore/excore calibraticn subjects the reactor to m axial xencn prturbatim. It should be noted that while the perturbaticn is well within the oprating limits of the plant, such maneuvers increase the ptential for a reactor trip and may degrade fuel performance. As demmstrated by the tests rm at the Ibchester Gas and Electric Reactor, the incore/excore relatimship does not change rapidly due to fuel depleticn. mus, the requirement to prform this calibraticn cn a 92 calendar day basis is mnecessary.
Ibrformance of the calibraticn every 92 EFPD is Imre than adequate to assume that the instranstaticn is within safety malysis assumptims.
If you have any questicns, please let us know.
Very truly yours, 1
O. W. D' LDS:abm Ehclosure cc:
V. C. Stamer w/o Attachments L. D. 91ealy G. H. Fischer w/o Attachments A. R. Kocn H. N. Cyrus w/o Attachments M. N. Browne T. C. Nichols, Jr.
G. J. Braddick O. W. Dixcn, Jr.
M. J. Virgilio M. B. Whitaker, Jr.
J. L. Skolds J. P. O'Reilly J. B. Knotts, Jr.
H. T. Babb B. A. Bursey D. A. Nauman J. B. Cookingham C. L. Ligcn (NSBC)
F. K. Maginum W. A. Williams, Jr.
NICF l
R. B. Clary File O. S. Bradham I
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ATTACHMENT I to NRC letter of 7/23/82 DEFINITIONS I.
INCORE AXIAL OFFSET TOP HALF BOTTOM HALF TOP HALF BOTTOM HALF TOP HALF I
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