ML13317A021
| ML13317A021 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/01/1992 |
| From: | Southern California Edison Co |
| To: | |
| Shared Package | |
| ML13309A332 | List: |
| References | |
| NUDOCS 9210090103 | |
| Download: ML13317A021 (6) | |
Text
Enclosure 1 S 0 NGS - 1 EVALUATION OF THE REFUELING WATER STORAGE TANK (RWST) FOR BUCKLING Purpose The purpose of this calculation is to check the tank shell of the Refueling Water Storage Tank (RWST) with reduced thickness for buckling using the methodology given in the Seismic Qualification Utility Group (SQUG) "General Implementation Plan" for addressing Unresolved Safety Issues (USI) A-46 and A-40.
Conclusion The RWST maximum compressive stress of 7.26 ksi in the tank shell is less than the allowable compressive stress of 9.14 ksi.
References
- 1. Seismic Qualification Utility Group (SQUG),"Generic Implementation Plan (GIP) for Seismic Verification of Nuclear Plant Equipment,"
Revision 2, February 1992, Section 7.
- 2. Calculation number DC-3679,"RWST Evaluation," March 29, 1992.
- 3. Impell report number 01-0310-1392,"San Onofre Nuclear Generating Station, Unit 1, Evaluation of the Refueling Water Storage Tank for Long Term Service," March 1986.
Calculation All terms in the following calculations are defined according to Reference 1 nomenclature.
Step 1:
Input Data Tank Shell Material: A-283 Gr C R =
204 in.
H' =
445 in.
tMin = 0.25 in.
t
=
0.299 in.
9210090103 921001 PDR ADOCK 05000206 P
2 tb
=0.313 in.
0 =
30,000 psi he =
12.75 in.
Es = 29.5x106 psi V5 = 578 ft/sec.
(Reference 3)
Fluid:
Y
= 0.03611 lbf/in
(=62.4 lbf/ft')
H =
445 in.
hf
- 0. in.
Bolts:
N =
32 bolts Size =
1 5/8 in.
hb =
32.75 in.
Eb =
29.5x10 6 psi Loading:
0.67g Modified Housner Ground Spectrum at 4% damping.
Tank is located on a concrete foundation at grade.
Step 2:
Calculate following ratios and values H/R
=
445/204
=
2.18 t,/r =
.299/204 = 0.00147 t av
=[88*0.299 + 357*0.2501/445 = 0.26 in.
tef
=
[0.26 + 0.25]/2 = 0.255 in.
tef/R = 0.255/204
0.00125 W
R2 H yf
= n(204)2 (445) (0.03611)
= 2.1x10 6 lb The above parameters, values and ratios are within the applicable ranges of Table 7.1 in the GIP. Therefore, the procedure is applicable to the SONGS 1 RWST.
3 Step 3:
Determine the fluid-structure modal frequency Using Table 7-3 of the GIP with:
R= 204 in.
tef/R 0.00125 H/R =
2.18 Ff = 7.13 Hz Step 4:
Determine the spectral acceleration Using the.67g horizontal ground spectrum at 4% damping:
For 0.8 Ff = 0.8*7.13 = 5.70 Hz or 0.175 sec.
Saf = 1.031g For 1.2 Ff = 1.2*7.13 = 8.56 Hz or 0.117 sec.
Saf = 0.886g Since VS is less than 3,500 ft/sec soil-structure interaction (SSI) effects on the frequency must be considered. From the SSI analysis performed in Impell Report No. 01-0310-1392, Reference 3, the spectral acceleration is 0.824g which is less than the above calculated acceleration. Therefore, Saf = 1.03g will be conservatively used for the seismic demand.
Step 5:
(Not applicable to buckling check)
Step 6:
The overturning moment has been rigorously calculated in Reference 2.
Steps 7 and 8:
(Not applicable to buckling check)
4 Step 9:
Tank shell stress The tank shell stress (a) is given by, PU e 1.32 Z 0.031 0 = (
)
+
t 2 1.43 a h2 + (4 a h2)0 333 NRt R t5
- where, Z = 1/ [1 + 0.177 a tb (tb/t ) 2 sRt Pu (bolt load)= 27.7 kips (Reference 2) a (width of the chair top plate parallel to the RWST shell)
= 4.5 in.
The above value of a is very conservative since the chair top plate extends along the shell circumference without interruption.
h (height of chair) = 12.75 in.
e (eccentricity of anchor bolt with respect to shell outside surface) = 2.25 in.
It follows that a = 22.6 ksi < ay (GY = 30 ksi)
Steps 10 and 11:
(Not applicable to buckling check)
Step 12:
Fluid pressure for elephant-foot buckling From Figure 7-7, in the GIP, the following value of Pe' is obtained by entering Saf = 1.03g, and H/R = 2.18:
Pel
= 3.7 Fluid pressure at the base (Pe) is given by,
5 Pe Pe Yf R = (3.7)(0.03611)(204)
= 27.3 psi Step 13:
Elephant-foot buckling stress capacity factor From Figure 7-8, in the GIP, the following value of the elephant-foot buckling stress capacity factor (a e) is obtained by entering Pe = 27.3, and ts/R = 0.00147:
ope
= 12.7 ksi Step 14:
Fluid pressure for diamond-shape buckling From Figure 7-9, in the GIP, the following value of Pd' is obtained by entering Saf = 1.03g, and H/R = 2.18:
Pd'
= 2.7 Fluid pressure at the base (Pd) is given by, Pd d
'Yf R = (2.7)(0.03611)(204)
= 19.9 psi Step 15:
Diamond-shape buckling stress capacity factor From Figure 7-10, in the GIP, the following value of the diamond-shape buckling stress capacity factor (ad) is obtained by entering Pd = 19.9, and t,/R = 0.0017:
ape
= 17.5 ksi Step 16:
Allowable buckling stress (a,)
The allowable buckling stress (ac) is taken as 72% of the lower value of ope or apd.
Therefore, c= (0.72)(12.7)
= 9.14 ksi
6 Step 17:
Overturning moment capacity The overturning capacity of the RWST was checked by postulating a weak link ductile failure mode, with the weak link in the form of tank shell bending.
The bending stress in the shell was calculated in Step 9:
a = 22.6 ksi
< a (GY = 30 ksi)
Other checks in this step are to verify anchorage, which was evaluated per Reference 2.
Steps 18 through 22:
(Not applicable to buckling check) 0 I