ML20095D370
| ML20095D370 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 08/17/1984 |
| From: | Woolever E DUQUESNE LIGHT CO. |
| To: | Knighton G Office of Nuclear Reactor Regulation |
| References | |
| 2NRC-4-126, NUDOCS 8408230314 | |
| Download: ML20095D370 (6) | |
Text
,:
e-
$VL
'Af (412 737 51 (412)923-1960 Nuclear Construction Division Telecon (412) 787-2629 Robinson Plaza, Building 2. Suit. 210 Pittsburgtt, PA 15205 -
August 17, 1984 United States Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Mr. George W. Knighton, Chie f Licensing Branch 3 Office of Nuclear Reactor Regulation
SUBJECT:
Beaver Valley Power Station - Unit No. 2 Do cke t No. 50-412 Response to Draf t SER Open Item No.173 Gentlemen:
This letter forwards the attached recponse to the NRC Geotechnical Engineering Section's Draft SER Open Item No. 173.
DUQUESNE LIGHT COMPANY By EL/J. Woolever JD0/wjs Vice President Attachment Ms. M. Ley, Project Manager (w/a) ec:
Mr. E. A. Licitra, Project Manager (w/a)
Mr. G. Walton, NRC Resident Inspector (w/a)
COMMONWEALTH OF PENNSYLVANIA )
)
SS:
COUNTY OF ALLEGHENY
)
On this /78 day of
,, A
/f9/, before me, a Notary Public in and for said Commor(wealth and Coun'ty', personally appeared y
E. J. Woolever, who being duly sworn, deposed and said that (1) he is Vice o
Pres ident of Duquesne Light, (2) he is duly authorized to execute and file a:s:
the foregoing Submittal on behalf of said Company, and (3) the statements Oc set fo rth in the Submittal are true and correct to the best of his mA g<
knowledge.
g{
n' / d ll\\ D tu
' Notary Public ELVA G. LESONDAK, NOTARY PUBLIC ROBINSON TOWNSHIP, ALLEGHENY COUNTY MY COMMISSION EXPIRES OCTOBER 20,1986
~
k Draf t SER Open Item No.173 (Sections 2.5.4.3.1, 2.5.4.3.4, 2.5.5.1, 2.5.5.2, 2.5.5.3, and 2.5.5.4) - Stability Analyses:
l Section 2.5.4.3.1:
The staff requires that the applicant must also consider the loading combination of OBE and standard project flood in all stability - analy-ses, as ' recommended in SRP 2.4.4.
We expect to report our evaluation of this matter in the final SER.
Section 2.5.4=3.4:
4 The applicant has de termined that the undensified area immediately north of the intake structure might liquefy unde r the SSE causing unanticipated stability problems.
Therefore, the applicant has performed a static slope stability analysis for the dredged slopes (shown in FSAR Fig. 2.5.4-32) on the west and east sides _ of the intake structue, assuming that the liquefied soil north of the intake structure had' weight but no shear s treng th.
The results of the static slope stability analysis for both nonnal groundwater and 25-year flood conditions indicate that the dredged slopes are stable if the uppe r 10 feet of soil north of the intake structure lique fies.
The applicant has also performed a dynamic slope stability analysis s
for the abova side slopes,- in res ponse to an OL review que s tion.
Before docketing this analysis, the applicant must ensure that loading combinations include the OBE and Standard Project Flood and SSE and 25 year flood.
c Section 2.5.5.1:
r In res ponse to the OL review que s tion 241.18, the applicant has considered additional failure surfaces through the silty clay layer as shown in FSAR Fig. 2.5.4-57.
This figure also-shows ' the soil properties of various layers used in the analysis..The ground water
~ table is taken at el-705 corresponding to the standard project flood.
~
The minimum safety factor of 1.29 was obtained in this dynamic slope s tability analysis.
The applicant will docket the results of this analysis in the forthcoming amendment of the FSAR.. We will report our evaluation in the Final SER.
Section 2.5.5.2:
The stability analysis of the side slopes east and west of the intake channel in front of the intake structure has been discussed in Fection 2.5.4 ~.3.4 above. The staf f will review the dynamic stability analysis of these slopes when furnished ' by the applicant with the forthcoming amendment of the FSAR.
Section 2.5.5.3:
The applicant analyzed the static and dynamic slope stability of the riverward slope north of the EOS for the combined loading of SSE and the. normal water level at el 665 ft.
The safety factors in the s tat ic and dynamic cases we re 1.6 and 1.2, res pe ct ively.
The SRP, Sect ion 2.4.4, recommend s that analyses be made fo r two combined
r 9
. i loading conditions, namely, SSE + 25 year flood (el 690 f t), and OBE
+ standard project flood (el 705 f t).
The applicant has stated that groundwater levels' in the clay layer of the. riverward slope would not change substantially during the relatively short duration of the 25-year flood.
Therefore, the applicant has assumed that - it is accept-able to cons ider failure surfaces through the clay layer with the groundwater level corresponding to the normal river water level at el 665 ft. rather than 690 ft.
Because of the presence of cohesionless soil layers with greater permeability than that of clay layer in the rive rward slope, the staff requires that the applicant perform s tability analyses for the two loading conditions desc ribed ab ove.
We will report the results of our evaluation of this matter in the final SER.
Section 2.5.5.4:
Based on a review of the applicant's design criteria and the results of his analyses, the staff has concluded that the slopes at the site are generally stable for the loading conditions considered by the applicant.
Hc. weve r, the applicant must reevaluate the stability of each of these slopes for two loading conditions, namely, (1) SSE +
25 year flood and (2) OBE + standard project flood, as recommended by SRP Se ct ion 2.4.4.
The applicant must also docket the stability analyses of all slopes where revised seismic coef ficients have been used.
Response
The stability analyses of slopes near the river resulted in adequate f actors of safety.
The analyses of the rive rward slope supporting the service water system (SWS) pipelines, the dredged intake channel slopes,
and the emergency outfall structure (EOS) riverward slope are described below.
Riverward Slope Supporting the SWS Pipelines:
FSAR Fig. 2.5.4-57 presents the results of the stability analysis of the riverward slope suppo rt ing the 30-inch SWS lines.
The analysis was performed assuming that the safe shutdown earthquake (SSE) load-ing condition and the standard pr aject flood occur simultaneously.
l This combination is the most cons erva tive loading condition which could be analyzed.
Since the results provide a satisfactory factor of safety, it was decided that analyses of the slope under the le s s severe loading conditions of the operating basis earthquake (OBE) +
standard project ' flood and the SSE + 25 year flood are unnecessary.
l Dredged Intake Channel Slopes:
FSAR Fig. 2.5.4-37 presents the results of the stability analysis of the dredged intake ch annel slopes.
A combination of normal water level and the SSE dynamic loading was analyzed. The top of the slope l
is at elevation 675 f t which is 10 feet above the normal water level (el. 665 f t.).
Raising the water level to the level of the 25 year flood or s tandard project flood will not significantly change the I
..- u,
~ results of the previous ' analysis, since the sicpe is almos t tot ally submerged under normal water conditions.
- As ' discussed in FS AR Section 2.5.4.8.1, it has been determined - from the results of _ the ~ stability analysis that part of the slope has f actors - of safety less than the minimum acceptable of 1.1 and is potentially unstable under dynarmic. loading conditions.
A liquefac--
tion - failure of the slope was postulated and the volume and final.
' configuration of the soil that may flow toward the intake structure was found to be insufficient to block the intake channel even under extreme low water conditions.
It was determined that analyses of the
. slope ~ for the SSE + 25 year flood and the OBE + s tandard project flood conditions will yield results similar to those under normal water conditions, and, therefore, the worst case of the slope failing has1 already been investigated and reported in FSAR Section 2.5.4.8.1.
EOS Riverward Slope:
Fig.173-1 presents : the results of the stability analysis of-the EOS riverward slope.
This section corresponds to Fig. 6-5 of the SWEC report entitled, " Stability of Slopes at the Emergency Outfall Struc-ture," June 1983. The OBE + standard project flood condition was not previously analyzed.
Since the cohesionless material _ above the clay layer will be partially saturated - during the standard project flood,
the stability of the uppe r slope may be af fect ed.
Therefore, an additional' analysis _ was ' performed for the OBE + s tandard project flood condition, as shown on Fig. - 17 3-1, resulting in a minimum factor of safety of 1.3, which is satisfactory.
The stability-of failure surfaces passing through the clay layer will not change by raising the water. level from normal water conditions to the '25 year flood level.
.As stated in the 1983 SWEC report, the y
short-lived flood conditions will not reduce the strength properties
_of the ' clay nor will it af fect the sand 'and gravel above the clay layer.
A failure surface below the clay layer 'through the sand and
~ gravel was analyzed for the SSE + 25 year flood condition and the factor of safety res'ulting from this analysis was also found to be
~
+
. satisfactory.
e i.
?
c l
l
[
E
I
'\\-
t f
c y4/
e i
wlV
/
O to*
4Y' O
4 4 r
780 "
O 4U s'
r['g>
(q[
c
, U~
e 4
gggRGENCY
- 4 g
OOTFALL g
~
- <4 STRUCTURE e
j T40 9/
/
ty"ol%.TO.: -
0 iii Yi h
&* Y. a SG ~
o g
~.
%%@9*** At OR * '~,6. *.*;l'9 fa,*'.*i,*
?~' ?
us CooDD gh
'o 0.j?gs; 'L '~~ *QQ.Q,;gg.gij
.o.;;;i,.;;e.:z.' *':.C.*':'o.,
o I* a o'
o f9. Q g 6
.goQo C A,$?o.,
o.o Oo P:0 Oo0.k ;[ g x.t30ocnof g (yg.eoyoW e o9 o
a 77 h.yh.., :. 4 FS
- s
,660 b
^
c
_km. __::E_
m Z
620 LEGEND
(,,,,,,,,j FILL: COMPACTED GRANULAR O
4 SCALE h f.o.'.'*J FILL: UNCONTROLLED hf] SAND, SILTY SAND, SANDY GRAVEL, GRAVELLY SAND NOTES l
(:;
5l SILTY CLAY
- 1. DATUM IS MEAN SEA j
2 PSEUDO-STATIC FOR 7 BEDROCK
- 3. DYNAMIC FACTORS 01 l
CONDITIONS UNLESS i
REF. " STABILITY OF SLOPES AT EMERGENCY. OUTFALL STRUCTURE," SWEC, JUNE 1983, FIG,6-5 2
e
' ' ENGINEERING SOIL PROPERTIES "a'ya[
CT soit unit cowEsioN W E,1 G,H T C-it/f f8 UNIT
,s DEHEE3 136 36 0
120 so o
PSEUDO-STATIC FORCES 1:3 3o o
0.[25 g 12 5 o
1900 (SEE NOTE 2) its o
25m MO.083g f25 C
SM 125 o
1500 125 o
1950 125 C
2co h
125 o
650 O
tas o
ios NORTH 4 TANDARD PROJECT FLOOD SEL.705' L;., 3... -i-_[;@ hQ 4 25-YEAR FLOOD EL.690' ec 700 L....
shis,y3 M9je OH/O RIVER E
1
~~~~
~ ~ ~ ~ ~ ~ ' ~
~~~
'h.
NORMAL WATER LEVEL i
_.'_'J
"~
tt EL. 665' 3
F S
- 1. 3 I
660
~
pog cy#d.fpOy wow %B g Wo%gT g%%
e CofgpO.;b!goi@OkkkkdikNhjgl[khlp!fllt
((
b"SS 4
h 80 TI t
JFEET Also Avanahle On Aperture Card CARD fEVEL.
SAFETY ARE DUE TO SSE LOADING FIGURE 173-1 OTHER"!ISE NOTED.
DYNAMIC CASE BE AVER VALLEY POWER STATION-UNIT 2 STONE E. WEBSTER ENGINEERING CORPORATION N
I 84 0 8 23 0 314 - bl