ML20128D257
| ML20128D257 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Limerick |
| Issue date: | 07/25/1983 |
| From: | Martin R NRC |
| To: | Nilesh Chokshi, Pearring J, Reiter L NRC |
| Shared Package | |
| ML19292B772 | List:
|
| References | |
| FOIA-84-624 NUDOCS 8505280544 | |
| Download: ML20128D257 (6) | |
Text
.
JBA JUL 131983 STRUCTURRL mECHROKS
"""""" A S S OCI A T E S wnummuunna a e.... e...
SMA 14302.01 516o Bren Street,i.ewport Beach. cam. 9266o (714) 833 7552 g
h bVb)bb July ll, 1983 h Mdd Nb y(%
Dr. John Reed J. R. Benjamin and Associates, Inc.
I Mountain Bay Plaza g-444 Castro Street, Suite 501 Mountain View, California 94041 g
Dear John:
During the Limerick PRA review meeting on July 8,1983, you raised some questions which I could not answer off the top of my head. The following responses should clear up the issues.
The first question was regarding an apparent inconsistency between the response factors for piping and for valves. These response factors should be the same as valve response is predicated upon piping response.
Initially the piping response factors were developed on the assumption tha t 1% damping had been used in the original design analysis when in fact 0.5% was specified. The valve response factors were calculated using the correct damping of 0.5%.
The text in the original report draft erroneously tried to explain the difference. A review of the work uncovered t'le error in the piping response factors and the cal-culations were changed. Unfortunately the text in the report was not properly changed. The response factors for piping on page 5-59 are low and should be the same as those for valves on page 5-60.
The descriptions on page 5-60 of how the valve response factor differs from the piping response factor should be deleted as there is no di f ference.
You raised another question regarding the deletion cf SRY loading from the generic derivation of piping and pipe support fragilities. The SRV loading was purposely left out of the generic derivation to examine the more conservative case.
If the majority of the loading is seismic, the resulting capacity factor is lower than -if the majority of the loading is from other sources. For instance:
=
c
'n
'SRV F
3 "SSE B505280544 841015 PDR FDIA SHOLLYB4-624 PDR
s
-Dr. John Reed I
J. R. Benjamin and Associates, Inc.
July ll, 1983 Page two C
where F
strength factor rela.tive to the SSE
=
s failure stress.
o
=
c stress from normal pressure and dead weight load e
=
n eSRV stress from SRV load
=
stress from SSE load e
=
-Assuming the sum of ( cSSE + C
'SRV) is at or near code allowable,
+
n the case where OSSE is a greater portion of code allowable results in the lowest valve of F. Likewise for supports, we derive the capacity s
factor for supports which carry only seismic loading as they are the governir.g cases.
A third question was raised regarding variability in testing due to use of spectral test methods. The attached pages from NUREG-CR1706 describe the problem and attempt to estimate the uncertainty.
I hope this explanation will clear up these issues. If you have any further questions please don't hesitate to call. I will be away for several weeks, but both Ravi Ravindra and Greg Hardy should be available to answer any further questions.
Very truly yours, STRUCTURAL MEC NICS ASSOCIATES, INC.
Robert D. Campbell Project Manager RDC:mw cc:
H. Hansell, P.E.Co.
4.4.5 Variability Due to the Use of Spectral Testing Meth~ ds o
In Chapter 3 the use of spectral testing methods versus a power spectral density approach was discussed. Smallwood in Reference 23, stated that it is important that a spectroni not be considered as a suffi.
cient specification. His study of a large variety of synthesis methods concluded that a different method may produce significantly different results. SWRI, in Referenc~e 22, performed an independent evaluation of
-test methods and concluded that with current spectrum methods, insuff-cient excitation of equipment modes might occur. Neither reference attenpted to quantify the magnitude of the variability that might be experienced.
The problem stems from the fact that a synthesized time-history contains peaks and valleys in acceleration or force and that if a signif-icant valley in the time-history input corresponds to a predominant fre-quency of the equipment being tested, the response may be significantly less than the rathematically anticipated and required response.
A much better approach, as reconenended in Reference 23, is to synthesize a time-history that corresponds to a power spectral density which envelopes the RRS rather than make the direct step from the RRS to the synthesized time-history. This approach tends to smooth out the 4
input time-history, resulting in less chance for an equipment mode to coincide with a significant valley. Most testing laboratories' do not, however, have this capability.
3 i
l Quantification of the variability that might result from use of spectral methods could be acenmplished by analytical studies that com-pared responses to synthesized time-histories keyed to power spectral densities as opposed to those synthesized directly to match the RRS.
1 4-38
.-+
,..-----.-.-,,,n-a, we.,
,,r,,
,,,-,n
,,.,_,,.,--,___-.s.,-__-
.The variability due to the use of spectral test methods is expected to be smaller than that. due to instrument and' control error and acceleration time-history variation and is considered to be prin61pa11y a
}
sodelfing uncertainty in that most of the variability could be eliminated' t
by using more sophisticated test equipment. Without conducting a study to quantify the variability, we would ett.imate 'the t 25 range of response to be within i 25% equating to a S of.11 of which g ~ 0.05 and Sg ~ 0.10 g
W 4
e
.y.
- 20. Smith, P. D., S. Bumpus and O. R. Maslenikov. "LLL/ DOR Seismic Conservatism Program, Part VI Response to Three Input Cenponents",
UCID-17959 (draf t report), Lawrence Livennore Laboratory, L,1vermore.
California, April,1979.
21.
l USEC Regulatory Guide 1.60, " Design Response Spectra for Seismic Design of Nuclear Power Plants".
l
- 22. Kana, D. D., and R. W. LeBlanc, "An Evaluation of Seisaric Qualification Tests for Nuclear Power Plants Equipment" (draft) prepared for the USEC by SWRI, Contract No. AT (49-24)-0372.
23.
" Seminar on Understanding Digital Control and Analysis in Vibration Test Systems", sponsored by Goddard Space Flight Center.. Jet Propulsion Laboratory and The Shock and Vibration Information Center, held at Goddard Space Flight Center on 17-18 June, 1975 and at the JPL on 22-23 July, 1975.
e 445
6 69
'T
.,o.
7 1 9,s a J g.-
I
.ke de~
P -5/V'
/V Cdo As4L P-2/9 E.
I 26o.u.sp& P-23 B
Z bcak
&s/. V._. _.--
Li. --
R 5/ 6 -.. -.-.-._ -...._
.._... /9.. L s e.
R-239'..
E C/>// 'a L 2 / G P A ://.'s r fron ;.R D1ar.& ~-....
For yn r ;~fo r na ho ~. Ereciua it M y.
k e
0
.~
66
.r
.M.4 M
NM.
N
.*=.6*.i
--..*..e
.eeeah. gee.___
p-
&G_--
M.
A.'e.M.M.
.. M.-
N
@MeD-
__. am e.
re-4
.y.
_