ML20084E161
| ML20084E161 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 08/12/1974 |
| From: | Amish K ROCHESTER GAS & ELECTRIC CORP. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| Shared Package | |
| ML20084E164 | List: |
| References | |
| NUDOCS 8304140365 | |
| Download: ML20084E161 (2) | |
Text
..
E b
'O N
n i
W)
W
~
j
_?
y-f, \\;(
i-N0CHESTER GA5 AND ELE CTRIC CORPORATION e 89 ECT LYElWE, ROUIE11LR. N.Y. ItM9 cfy.:
Ain,.w3.,,u.
(%-:
mi ~
,,%,,...m.
..34 m oo
- s. y+
n,n m e
.. m August 12, 1974 g-k,..
Mr.. James P. O'Rollly, Director N
Directorate of Regulatory Operations
- s. u :.
Rogion 1
'd j U; S. Atomio Energy Commission
,, '7 7}; 7 ;
631 Park Avenue King of Prussia, Ponnsylvania 19406
.f. -
Stfbject:
AAalysis of the charging pump choke filter vont lino failuros
- ( :q C
R1 E. Ginna Nuolear Power Plant, Unit No.1 Docket No. 50-244 8.%
Doar Mr. O'Railly:
O.1
,gn-
. N?
On July 16, 1974 an interim report was submitted conocrning abnormal ooourrences 74-12 and(74-132 These involved failures which occurrod O[.p.j at differont times at wdlds on oaoh end of the 3/4 inch vent nipple located b..
on the pump discharge side of the charging pump choko !!!!er. SinceJuly
.C ;,1 16, 1974 reports of independent analysis and investigative action have y*'
been recejvod from Bochtel Corporation and Southwest Roscaroh Institute.
i}.
Along with the independent analysos, an in-house review of the history of
$d the vent lino' failures was made inoluding a review of stu(lpa of the original ovaluation and design of the charging pump filte
( 'C. l ~
ofter the installation of the choke filter in 1971/;rpystem H and the analysis
/
The original vent line fillot welds were installed with the Shlolded Metal I
Aro Welding Process. These welds had a 189 site of about S/8 inch which is larger than a normal fillot wold on a 3/4 inoh pipe., On December 11, 1973 a pin hole loak was discovered in the wold between the nipple and weldolet. This leak was the result of a pore which propagated to the base of the weld, The two original fillet wolds were removed and replaced with a new nipple and fillet wolds with a leg sizo of about 3/4 inch using the Gas Tungston Aro Welding Procedure. These welds failed bn the following dates:
A.
June 29,1974 - wbld betwoon nipple and valve s
l B,
July 2,1974
- weld between n.ipple and weldolat.
=
t
~
The failure of the wold between th6 nipple and valve which occurred on June 29, 1974 was analyzed and the following information was obtained. The metallurgical analysis revealed a major crack with no secondary fissuring or evidence of corrosion. The sample was basloally freo of sensitization; therefore, it was concluded that the failure was the result of a fatigue mechanism.
8304140365 740812 E
PDR ADOCK 05000244 S
,8 g
. ; ~ :5... ' * -l:+ ~
,-:.: y _' ; A
+
O pt y :., 4 p a j; g % &. g, q+ r
.g. g.(f n.
%murstra cAs h rc Tkhar.
hh s8t r v ko. 2 pe u hugust T2,1974 io Mr. Janinc P. O'Itcilly The crookod fillet wold between the woldolet and nipple whloh was discovorod on July,2,1974 Was dotormined to bn the result of a orack that popagated c
I through the wold from an area wht rt there was no fusion. This failure was
' aobolorated because the area of L halon setod as a stress riser thus causing the ausceptibilitysto fatigub and f Jure.
/
Th6 welds inada as a repair to the. leck of Dooomber 11, 1973 were normal for 3/4 inch socket wolds and wwe adeqaate for the internal possure pulsations exerted on the system and tbs dynamic stressos due to system vibration at normal conditions. Ilowever, based on data o tainod in the original evaluation and design of the charging pump filter system p/ 1t has boon concludr.d that various modes of operation of the charging pump system could result in dynamio vibration of suffiolent magnitude to produce a combined stress which caused the fatiguo failure in these wolds, Consequently these replacer.,ent wolds were of insuffiolont sizo to recognize the dynamio responso of the system. Review of the stress analysis mado for this sytem veriflod this inadoquacy. Thorofore, to prevent recurrence of the fatigue failure, the vont line was reinstalled wit)(
fillet wolds of the following leg sizes:
A.
Valvo'to nipple - 1/2 inch log sir.o B.
Woldolot to nipple - 3/4 inch log size.
The stress levels in the wolds should'now be reduced by a factor of about 6 to 1.
The NBARB concurr951 with this oorrectivo measuso.
The Plant Operations Review Committeo approvod the additional recommendation to install a temporary support, bracket designed to min!mizo vibrations in the vont line under any mode of oporation.
The Plant Operations Review Committee also approved the final corrective action which is planned for our next refueling outage and will consist of rolocating the vent line to the dcwnstream side of the charging pomp choke filter, no chche futor was installod in 1971 to eliminate pulsatipna which resulted in similar fatigua failures of pipe stub end connections.f/ This filter effectively reduced the pulsations in the charging pump system by several orders of magnitude.
Sinoo the vent line which failed is located upstream of the filter it is subjoot R
to high dynamic pulsations as a result of the variable spood operation of the charging pumps. Relocation of th!a vent lino downstrearn of the choke filter, e
as well as the corrective measures stated above, should prevent this problem from recurring in the futuro.
Very tyuly yours, h
Keith W.'. Amish T i., ;
b c.eib'.
g Southwest Research Institute Report, "SGA Pic3d Evaluation and Pulsation Analysis" Oune 22-26, July 6-10,1970)
M' Southwest Research Institute Report, " Charging Dystem Pilter Analysis" (May 10-12,197 M Mb. -
j,
- gQMQ.'gd.; fy
- 1 e
- +/
'fi.p(,,{ 4 ' 7
.' g j. g - / %
p,.y &
.(.b. y y p m.g i
.