ML20010E344
| ML20010E344 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/07/1981 |
| From: | Anderson N Office of Nuclear Reactor Regulation |
| To: | Martin C Neely Research Reactor, ATLANTA, GA |
| References | |
| NUDOCS 8109030372 | |
| Download: ML20010E344 (17) | |
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August 7,1981 Professor C. S. Martin k
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081 A 78 School of Civil Engineering
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co* d d @ oer q Georgia Tech h
h Atlanta, Georgia 30332
Dear Professor Martin:
The enclosed information on the San Onofre water hammer event we discussed today was presented to the NRC staff at a meeting last week.
In addition to the information in the enclosures, I will give you a brief sumary of the event.
San Onofre 2 was undergoing pre-operational testing and was at hot shutdown condition. The water level in steam generator #2 was decreased.
to a level well below the feed ring. The feed ring drained in a time i
estimated to be between 30 minutes and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> through the themal sleeve. He feed ring was allowed to fill with saturated steam and was maintained in this condition for approximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The water level in the feedwater piping was believed to have remained at the level of the entrance to the feed ring. The test was initiated by ramping the feedwater from 0 to 1200 gpm in about 30 seconds using the turbine driven auxiliary feed pump and one electric motor driven auxiliary feed pump. An acoustic monitor was in place on the feedwater pipe and plant personnel were stationed near the steam generator to listen for water harr'er noise. The acoustic monitor did not indicate any perturbations in the feed pipe and the observers did not detect any noise. The damage to the feed ring was discovered later during an inspection of the steam generator.
Combustion Engineering and Southern California Edison calculated that a pressure load of 500 to 700 psi was created due to condensation in the feed ring and there was apparently no wat9" slugging involved.
We are including this event in our experience sumary on water hamers but at this time do not consider it to be of sufficient safety significance to impact our resolution of the Water Hamer Unresolved Safety Issue and our continuing study of water hammer phenomena.
STRIBUTMN.
Central Fi1e) (WI)
GIB Reading' A-1 Task File A. Serkiz
!!ewton R. Anderson, Section 1.cader N. Anderson Generic Issues Branch K. Kniel Division of Safety Technology
Enclosures:
As Stated 006029 omcc > D.ST:GIB.
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8109030372 010807 PDR ADOCK 0500036 oan) 08../.... /. 81 h
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'o UNITED STATES E % y.qf' g NUCLEAR REGULATORY COMtvilSSION
- ,.3W.. gC W ASHING TON, D. C. 20555 N
e August 7, 1981 i
Professor C. S. Martin School of Civil Engineering Georgia Toch Atlanta, Georgia 30332
Dear Professor Martin:
The encicsed information on the San Onofre water hammer event we discussed today was presented to the NRC staff at a meeting last week.
In eddition to the information in the enclosures, I will give you a brief suncary of the event.
San Onofre 2 was undergoing pre-operational testing and was at hot shutdown condition. The water level in steam generator #2 was decreased to a level well below the feed ring. The feed ring drained in a time estimated to be between 30 minutes and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> through the tiiermal sleeve. The feed ring was allowed to fill with saturated steam and was maintained in this condition for approximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The water level h: the feedwater piping was believed to have remained at the level of the entrance to the feed ring. The test was initiated by ramping the feedwater from 0 to 1200 gpm in about 30 seconds using the turbine driven auxiliary feed pump and one electric motor driven auxiliary feed pump. An acoustic monitor was in place on the feedwater pipe and plant personnel were stationed near the steam generator to listen for water I, amer noise. The acoustic monitor did not indicate any perturbations in the feed pipe and the observers did not detect any noise. The damage to the feed ring.was discovered later during an inspection of the steam l
generator.
l Combustion Engi m ering and Southern CaliTornia Eaison calculated that a pressure load ot 500 to 700 psi was created due to condensation in the feed ring and there was apparently no water siugging involved.
We are including this event in our experience sumary on water hammers but at this time do not consider it to be of sufficient safety significance to impact our resolution of the Water Hamer Unresolved Safety Issue and our continuing study of water hamer phenomena.
1 INewton R. Anderson, Section Leader l
Generic Issues Branch i
l Division of Safety Technology
Enclosures:
As Stated
0 e
July 31, 1931 PRELItiII;ARY REPORT OF CC:DITIO:; 0F FEEDUATER PIPE ASSEMBLY Ifl SA.*i 0;0FRE U:11T 2, T10. 2 STEAM GEilERATOR The danaged pipe is in Steca Generator E0ES (SCE designation).
The CE Chattanooga designation is Steam Generator 2.
This Steam Generator is also referred to as the fiorth Steam Generator.
The feedwater pipe is located in the down co;aer approximately 75" below the Steam Separator Support Deck (Can Deck).
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Support qq
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Page 1 of 9
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The feedwater pipe assembly is supported on four (4) brackets. These brackets are welded to 'the pressure boundary with full penetration welds. The brackets 90, 1660, 1940 and 2700 locations.
The feedwater nozzle 0
are located at the and water distribution box is located at the 00 position.
j 00 Feedwater nozzle i X i
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Page 2 of 9 w
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3 The feedwater pipe is fabricated from SA-106-Grade B,12" schedule 40 pipe'
'(ncminal wall thickness 0.406"). The feedwater pipe assembly is mde in two sections. These sections are referred to herein as the 0-900 section and the 0-2700 section. The 0-900 section is supported at the feedwater distributfon box and on brackets located at the 900 and 1660 positions.
The 0-270 section is stdported at the feedwater distribution box and on brackets located at the 2700 and 1940 position.
J-Tube 1 l00 J-Tube 1 nh
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J-Tube 38 J-Tube 38 1800 The discharge nozzles on top of the feedwater pipe are referred to as J-Tubes.
There are 38 J-Tubes in each section of the feedwater pipe assembly.
The J-Tubes are numbered starting at the feedwater distribution box.
In the 0-90 section the numbering system is clockwise (as viewed frcm top of ring) and counter clockwise in the 0-2700 section.
Page 3 of 9 1
2
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Condition Of The Feed later Distribution Box
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Rotation in the plane of the paper.
(Note: the rotation is greatly 1
deformed condition exaggerated)
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.All four bolts sheared offt t
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Condition Of Feed-tater Pipe Assembly 0-90 Section Tr.e visual deforcation of the feedwater ring starts approximately 10" frc., the water distribution box (Pipe ovality checks indicate that the cif ca:a tion starts about 2" from the box).
The sketch below describes
- he condition of the pipe beh.een J-Tubes 4 and 5.
t i
Pressure Ecundary
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1 1/2" -
x 3 3/16"-
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The above condition is typical up to J-Tube 9 after which the deformation switches from vertical to horizontal.
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.The sketch below describes the condition between J-Tubes 9 and 10.
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l Tt above cross section is typical until approximate J-Tube 19 (cross section is rotating counter clockwise as J-Tube 19 is approached. J-Tube is located imediately prior to the 900 support bracket). At this location the -
I pipe regains the original round shape. This condition remains to the end of the pipe section. There is no apparent deformation of the end plate.
Page 6 of 9 l
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3.
Condition Of The Feedaater Pipe Assembly 0-2700 section.
'The visual defomation starts about 18" (between J-Tubes 2 and 3) from the, water distribution box. The sketch below depicts the pine cross section
'between,J-Tubas 4 and 5.
s 6 7/8"
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15" 5 7/16" Pressure Boundary
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The above cross section remains past J-Tube 6.
The defomation switches from vertical to horizontal between J-Tubes 7 and 10.
Past J-Tube 10 the defort:ation is horizontal.
The sketch below depicts the pipe cross section between J-Tubes
'14 and 15.
Pressure Boundary j
Some metal contact on I.D. between top and bottom of pipe 1
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This condition is typical (although less crushing) up tc J-Tube 20.
Past J-Tube 21 the ring regains its original circular cross section.
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1 Page 8 of 9 l
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a 4.
Condition of,Supoort Brackets..,
All brackets have been visually inspected and no defects were detected. A KT inspection revealed some minor indications in three of the six brackets.
It is believed that these indications are not a result of the loading that occurred during the feed-water sparger collapse. The indications are probably porosity or slag and they can be removed. No welding to the pressure boundary will be required.
5.
Condition of U-bolts 0 bracket). U-bolts were stretched upward beyond the a)
(090 elastic limit. Bolts did not fail but assembly loose.
b)
(0 166 bracket). Condition is the same as described in 5(a) above.
0 c)
(0 2700 brackets).
Both U-bolts failed at the threads.
U-bolts deformed beyond elastic limit.
0 d)
(0 194 bracket).
Condition' is the sar.e a,s described in 5-(c) above.
Page 9 of 9
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/ /- FEEDWATER SPARGER BUCKLIflG CONSIDERATIONS DAMAGE MECHANISM: SUDDENLY APPLIED DIFFERENTIAL PRESSURE FACTORS WHICH REDUCE THE LGAD CARRYING CAPACITY OF THE PIPE: (A) 0VALITY (B) VARIATION IN THICKNESS (C) HOLES IN THE PIPE (D) UNBALANCED 6 P LOADING O psyyw-%.p p W*1. wep M %gv W W-
- -ed
l',' FEEDWATER SPARGER COLLAPSE MODE 5 3/4" 17" a r t \\p /'/' n g 3 3/4". - \\ N.' / $ h \\ ,N S _ ECTION VIEW \\ , Buckling "' C ^ ' ^ c 5 5 Fbde 2 s, 450-y I l N' l N M Hole \\ \\[h '/ i N / 1N f/ ! N f N / N Q' 5 1/ /p 3 \\ f N 1 1/2" l 'x / -x 17" b 3 3/16" e i 1 ELASTIC - PLASTIC BUCKLIflG l10DE 1 At:ALYSIS l10 DEL a
t ~ FEEDWATER DISTRIBUTOR B0X SUPPORTS AND LOADING _Feedwater Distribution Box ~ l[ s E 'p[ ' ' -.____,ta un s _v Unbalanced . j f_ , il t.P Loading {--M-- jd, .O O ,O O 6 Original condition i \\ Rotation in the plane of the paper. (Note: the rotation is greatly exaggerated) deformed condition 3 g3 .All four, bolts sheared off. ,o 1 i - - - - - ' - ~ ' ^ ^ - ^ -- - ~ - - ~ ~ ^ ~ ~ ~ ~
[ "b. J. if FEEDWATER SPARGER SUPPORTS AND SUPPORT LOADING .$.f fA I '% / A \\ Unbalanced s f LP Loading \\ 4 A It! h * '. \\;t /q Q3'. DI [-[=-)*7,s R -/ R( - L 3 ,j .. _ l l 1 r\\ \\' li 'l\\ ~// \\ \\\\ R 'R N /? Ns y y \\ h 'lj-(k\\W f ~ >n n g( W -- p.... ~.. - !r v 9 / SECi!O.'l VIE'.1 BB -}}