ML16342A662
| ML16342A662 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/27/1999 |
| From: | Poslusny C NRC |
| To: | NRC |
| References | |
| RTR-REGGD-01.121, RTR-REGGD-1.121 TAC-M98283, TAC-M98284, NUDOCS 9901280263 | |
| Download: ML16342A662 (4) | |
Text
CATEGORY 2
'REGULA'Y INFORMATION DISTRIBUTI h" SYSTEM (RIDS)
ACCESSION NBR:9901280263 DOC.DATE: 99/01/27 NOTARIZED,:, NO FACIL:50-275 Diablo Canyon Nuclear Power Plant, Unit 1, Pacific Ga 50-323 Diablo Canyon Nuclear Power Plant, Unit 2 Pacific Ga AUTH.NAME AUTHOR AFFILIATION POSLUSNY,C.
NRC - No Detailed AffiliationGiven RECIP.NAME RECIPIENT AFFILIATION NRC - No Detailed Affiliation'Given DOCKET"5 05000275 05000323
SUBJECT:
Informs that based on info provided as result of phone call held last week, insufficient data appears to be available to fully resolve risk issues associated with cracks returned to service using W extending above tubesheet.
DISTRIBUTION CODE:
DFOID COPIES RECEIVED:LTR I ENCL Q SIZE:
TITLE: Direct Flow Distribution:
50 Docket (PDR Avail)
NOTES:
Ci A
E' RECIPIENT ID CODE/NAME INTERN ': FILE ENTER Ol EXTERNAL: NOAC gg)(p p(Z)nq 0 lent(Q COPIES LTTR ENCL RECIPIENT ID CODE/NAME NUDOCS-ABSTRACT NRC PDR COPIES
'TTR ENCL 2'
N NOTE TO ALL "RIDS" RECIPIENTS:
PLEASE HELP US TO REDUCE WASTE. TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT THE DOCUMENT CONTROL DESK (DCD)
ON EXTENSION 415-2083 TOTAL NUMBER OF COPIES REQUIRED:
LTTR 4
ENCL
J~rh s(er pos(usny - Riskque.wpd a/
Page 1
Based on information provided as a result of the phone call held last week, it appears that there is insufficient data available at this time to fullyresolve risk issues associated with cracks returned to service using W* extending above the tubesheet.
The staff believes that modifications to the repair criteria consistent with the guidance in NRC Regulatory Guide 1.121 would resolve the staff's severe accident risk concerns.
The staff presently recognizes that the proposed repair criteria do not specifically consider allowances for degradation growth. The licensee may wish consider modifying the requirement specified in 4.4.5.4.11(e)2 to specify consideration of growth rates.
Performance objectives could also be included to ensure that the staff's concerns stemming from analyses completed in NUREG-1570 are resolved.
As discussed during the phone call, such a modification may be as follows, "Axialcracks in tubes returned to service using W*shall have the upper crack tip below the BWT by a distance such that at the end of the subsequent operating cycle the entire crack remains below the tubesheet secondary face. The distance determined by the licensee should consider allowances for nondestructive testing measurement uncertainty and crack growth."
In order to evaluate the methodology to demonstrate the performance objective included in the technical specifications, the licensee should submit to the staff the criteria established to determine the necessary distance to preclude the growth of axial cracks that are returned to service into the freespan region. The licensee may also wish to consider the location of the BWT with respect to the top of the tubesheet.
The staff will review the proposed methodology to verify that the bases of the performance goals consider the factors recommended by the staff. Ultimately, the licensee must demonstrate that the performance goals are satisfied through a condition monitoring assessment at the end of the cycle.
In addition, the licensee should submit for staff review, the criteria it will"utilizeto demonstrate at the end of each operating cycle that the performance objectives are met. This criteria should include allowances for NDE uncertainty and should demonstrate that there is a low probability that any of the identified flaws have extended into the freespan area above the tubesheet.
I L((Jsld Qs(wgo~
l3ocl~ Ndp r( D - 2.yd' 3 ~ 3 9'701280263 990i27 PDR ADOCK 05000275 P
PDR r
/
~800~) 7
+pc
~(rr( &l((Dyr(
(
GIadrt
'c N