ML20058L221
| ML20058L221 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 08/02/1990 |
| From: | Haseltine J YANKEE ATOMIC ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BYR-90-108, NUDOCS 9008070079 | |
| Download: ML20058L221 (2) | |
Text
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' W $ANKEEATOMICELECTRICCOMPANY;
'$G'l's*go7";'l" l
Sb% N S80 Main Street, Bolton. Massachusetts 01740-1398 -
. YANKEE August 2, 1990 BYR 90-108
-United States Nuclear Regulatory Commission Document Control Desk-Washington, DC 20555 5'
References:
(a) License No. DPR-3 (Docket No. 50-29)
(b) USNRC Letter to Yankee, dated July 31, 1990
Subject:
PTS Sensitivity Study (N
Dear Sirs:
As requested in Reference (b), we-have performed a PTS sensitivity study l
for a variety of mean. values of reference temperatures for the four materials l
in the beltline region. The results are presented in the attached table.
Using the fracture mechanics results for the maximum mean values of reference temperature for each material, a through-wall crack frequency of 1
5 x'10-7 per year is obtained, which is below the Regulatory Guide 1.154 i
criteria of 5 x 10-6 per year. This represents an extremely conservative j
' result when it is compared with the nominal result shown in the table-from the l
July 9, 1990 Yankee evaluation of less than 7 x 10-9 per year.
The sensitivity study used the.same distributions of input parameters, flaw density..and simulations for the-fracture mechanics as the July 9, 1990 Yankee evaluation. The variation of fluence in the plate and weld materials was modeled.. Flaw length was modeled with a six to one aspect ratio for initiation and infinite length for arrest except for the lower plate, which used one-half the length of the lower plate for arrest because the majority of the plate sees minimal fluence.
l The study used five of nine transient cases from the July 9, 1990 Yankee evaluation.
Each transient case not used was bounded by one of the other
. cases and the same fracture mechanics result was assigned. The total through-wall' crack frequency was then determined by using the event frequencies from all transients and the conditional failure probabilities from the fracture mechanics.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY lh ja$
9003070079'900802
?
PDR ADOCK 05000029 J. D. Haseltine P
PDC Project Director
.g JDH/gjt/WPP72/84
- g. r 9 u
o Attachment cc: USNRC Region I
/
USNRC Resident Inspector, YNPS Il {
s;..
.G.
- Table 1
~
Through-Wall Crack Frequency For Yankee Beltline Materials Mean Reference Temperature Sensitivity Range (F)
-Material Nominal Maximum Axial Welds 140 230 Circ. Weld 228 360 Upper Plate 190 280 Lower Plate 183 325 Total Through-Wall Crack Frequency
<7E-09 5.0E-07 4
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