ML20128F650
| ML20128F650 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 09/27/1996 |
| From: | Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-80-13, NUDOCS 9610080150 | |
| Download: ML20128F650 (4) | |
Text
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v lEB 80-13 PECO NUCLEAR esco m c -
A Unit of PECO Energy
$aNPIN September 27,1996 l
Docket No. 50-277 License No. DPR-44 U.S. Nuclear Regulatory Commission Attn: Document Control Center j
Washington, DC 20555
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Subject:
Peach Bottom Atomic Power Station, Unit 2 Core Spray in-Vessel Piping
Dear Sir:
l The purpose of this letter is to provide additional information regarding crack like indications identified in the Peach Bottom Atomic Power Station, Unit 2 "B" loop Core Spray System Tee Box cover plate.
Attachment A provides additional information regarding applied loads used for the determination of the allowable flaw sizes for the core spray line cover plate. This letter supplements our telephone conversation on this subject i
which occurred at 14:30 on September 27,1996.
Additionally, an inspection of the PBAPS, Unit 2 "C" loop core spray sparger Tee Box using an enhanced VT-1 visual inspection, with a resolution of.5 mil, revealed no recordable indications. The results of this inspection supplement our conclusions that there are no generic implications due to indications identified on the PBAPS, Unit 2 "B" loop core spray header Tee Box cover plate.
If you have any questions, please contact us.
Very truly yours,
.0. Y G. A. Hunge J, 8,
Director Licensing Section Attachment cc:
H. J. Miller, Administrator, Region I, USNRC W. L Schmidt, USNRC Senior Resident inspector, PBAPS a:cas l
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Subject:
. Peach Bottom Unit 2 Core Spray hop B Applied Loads This letter proLides a discussion of the applied landing us.d for th. J.e.rmia. tion orth.
allowable flaw izes for the core spray line cover plate.
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j The 1.eds used in the ownelysis were those Rom the ar across the core spray line pipe and the impingement of flow onto the cover plate. These are considered the only significant loadings
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on the cover plate at the time of core spray irdection. The cover plate is positioned such thar
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y.u. ora. us. syrmy uno suen as tne meaner to elbow welds 3
and downcomer welds. Durmg core spray iriection. the pressure drop across the tee box wall i
is 133.2 pai. The flow during indection is 7825 gpm. This results in a load of 7702 lbs due to the pressure difference and 1468 lbs due to flow impingement. Thus, the totalload is 9170
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lbs.
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j The failure mode considered in causing failure (blow-out) of this section is caused by the AP
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and flow impingement loads which act to push the cover out. Based on previous analyses of core spray piping, the seismic loads in the cover plate are smalt In addition, the thermal loads
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are small and tend to cause a " ring type ofload (normal type stress not shear) on the cover j
plate location. This type ofloading would not cause a net section type of failure and does not i
contribute to the shear failure (blow-out) mode being considered here. In considering the
- shear type of failure, the Gow stren is taken as one-half of that for normal stress j
(ow = 3S,./2). which essentially increases the safesy far. tar by a factor era.
- r During installation of the line, there were instances were some movement of the line may have induced stressei in the vicinity of the 3 o' clock and 9 o' clock locations (fit-up movements).
Analyses for this piping line and previous analyses have confirmed that there is a localized intensification of tensile bending stress in the 3 o' clock and 9 o' clock cover plate locations.
and that the strisses at the 12 o' clock and 6 o' clock location are opposite in sign. This intensification in stress at the 3 o' clock and 9 o' clock locations would contribute to the initiation ofindications and crack propagation in the thickness direction as does the weld residual stress. The observation ofindications at the 3 o' clock and 9 o' clock locations is consistent with this stress behavior.' It should be noted that these normal types of stress do t
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l not contribute to the shese " blow-out" failure being considered for the cover plate or net-section faihire.
It should be noted that piping expansion stresses, which are low in this case, are also divided by the safety factor in the equation which de6nes the stress state at collapse for flux welds.-
This reduces the expansion stresses even thrther.
I Please contact ye ifyou have any questions, 1
J.
s L. Herrara Principal Engine er Engineering & Licensing Consulting SeMees (408) 925-6316 k. AX (408) 925-1150 t
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