ML20043B051
| ML20043B051 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 05/15/1990 |
| From: | Sieber J DUQUESNE LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9005240123 | |
| Download: ML20043B051 (3) | |
Text
. _. _.
~
e Be v r Vill:y Power St tion s.
shippingport. PA 15077-0004 JOHN D $..lt b&R talb 5916265 vice p....
ni. u c, o.our May 15.,1990 U. S. Nuclear Regulatory Commission Attn:
Document-Control Desk.
Washington, DC 20555
Reference:
Beaver Valley Power Station, Unit No. 2 Docket No. 50-412, License No. NPF-73 Primary Component Support Snubber Elimination Gentlemen:
During various telecons in March, 1990 between members of my staff and the NRC staff to discuss the subject request, the NRC staff requested
- a. review of load case B/G for Beaver Valley Unit 2.
Attached is the additional information-requested.
If there are any questions on this matter, please contact my office.
Very truly yours,
. D. Sieber.
Vice President
(
Nuclear Group t
I cc:
Mr. J. Beall, Sr. kr.sident Inspector Mr. T. T. Martin, HRC Region I Administrator L
Mr. A. W. DeAgazio, Sr. Project Manager i
-f 0005240123 900515 ADOCKOSOOg2 FDR 7
gart e
///
s DUQUESNE LIGHT COMPANY Nuclear Group Beaver Valley Power Station Unit #2 ATTACHMENT Additional Information Regarding Primary Comoonent Sucoort Snubber Elimination The following presents additional information which was verbally-requested by the NRC Staff in
- March, 1990.
fhis information references our previous submittals dated October 27,
- 1988, January 4, 1989, and February 24, 1989 which submitted WCAP-11923, WCAP-12093 and WCAP-12093, Supplement 1, respectively.
The above analyses are based on the revised loading configuration due.to large bore snubber elimination and reflect the current as-built condition of Beaver Valley Unit 2.
Review of Load Combination Case B/G The NRC Staff requested a review of load combination case B/G for Beaver Valley Unit 2.
The following discussion references information provided in Section 5 of WCAP-12093 and WCAP-12093,-
Supplement 1.
Load combination case B/G is a combination of cases B and G where:
Case B:
Normal operating case with stratification (36*F Delta T)
Case G:
Earthquake (SSE) loads superimposed with heatup or cooldown stratification (315'F Delta T)-
The leakage flaw size for case B at critical location-171 is 3.10.
inches.
Twice the leakage flaw size or 6.20 inches is used to determine the J applied value.
Referring-to figure 4 of WCAP
- 12093, Supplement 1,
"J Versus Flaw Size for Case C/G, Node 171" and applying the case B flaw size (6.20 in.); produces a J applied value of approximately 1250 in-lb./in for B/G.
This J Casg hich relates applied value is less than J max of 3000 in-lb/in w
to a
critical flaw size of-approximately B.5 inches.
Therefore, acceptability of Case B/G is demonstrated.
Review of Probability of Case B/G Event The load combination case B/G is equivalent to postulating the discovery of a
leakage flaw during normal' operation conditions, followed by a forced cooldown to Mode 5 (RCS temperature less than.
200*F) and while at a 315'F Delta T stratification condition,-the occurrence of a safe shutdown earthquake.
The probability of the 10-gnario occurringO is estimated to be on the order of above se to 1
X 10-per reactor year.
This is based on the 1
X combination of the following probabilities:
r ATTACHMENT Page 2 Small non-isg/ reactor year a) lable 14CA (comparable to leakage flav)
- 5.83 X 10~
b)
Equipment damage due to earthquake probab!11ty
- 1 X 10~3/ reactor year to 1 X 10~4/ react or year c)
The occurrence of a
315'F Delta T stcatification is on the e
order of 1 to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> during a forced coo)down event.
a x b x c conservatively yields 1.3 x 10'S/ reactor year As shown
- above, the probability of a case B/G event is extremely small and does not represent a reH istic scenario. 1X10~{/ reactor A des gn basis LOCA is estimated to have a
probability of year.
Therefore, the probability of a case B/G event is much less than other events considered in the licensing basis for Beaver Valley Unit 2.
The more realistic cases of B/E and B/FF were performed and demonstrated acceptable in WCAP-12093, Supplement 1.
'r