ML20003F433
| ML20003F433 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 04/15/1981 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8104210243 | |
| Download: ML20003F433 (11) | |
Text
.
t SOUTH CAROLINA ELECTRIC a gas COMPANY D
7 me orrice som n.
4 COLUMe:A. SouTN CAmouMA 292I8 va m.,u,,,... o. coco,.
April 15, 1981
/q./
gg% [
.j T. C. NicHoLs, J n.
Y*%oD j)
Nueu.a on..no s s l. -
hY
\\
+
/
sd Mr. Harold R. Denton, Director 36 Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Subject:
Virgil C. Summer Nuclear Station Docket No. 50/395 FSAR Changes - Seismic and Systems Interactions
Dear Mr. Denton:
South Carolina Electric and Gas Company, acting for itself and as agent for South Carolina Public Service Authority, herewith forwards forty-five (45) copies of miscellaneous (langes to the FSAR. These changes incorporate information presented during the ACRS Committee meetings in the areas of systems interaction and effects of reservoir induced seismicity. These changes will be incorporated in the next FSAR Amendment (No. 26).
Very truly yot:rs,
. C. Nichols, h
RBW:TCN:pj p
Enclosure cc:
V. C. Summer G. H. Fischer T. C. Nichols, Jr.
C. A. Price D. A. Nauman W. A. Williams, Jr.
R. B. Clary A. R. Koon A. A. Smith H. N. Cyrus J. B. Knotts, Jr.
J. L. Skolds
.B.
A. Bursey O. S. Bradham M. A. Barnisin R. Faas ISEG NPCF/WhittAer File PRS 81r.421opC h
4 Valves with direaded stems and backsetto era not postulated as potential missile sources because of the unlikelihood of coincident failure of both die threaded stem and the backseat. Valve bonnets are not postu-lated as potential missile sources when the allowable stress for Lonnet retaining ring material is less than 20 percent of die material yield strength.
Bolted valve bonnets are not postulated as missiles since the safety factor for the bolting is greater than 4.
Valves outside the reactor building were reviewed and none were postulated as missiles.
24 (The main feedwater check valve bonnets were previously postulated as
~
missiles. These valves were replaced, because of feedwater water hammer concerns, with those of another design which meet the criteria described above).
z}o NSerT k 6
CA J
1 j
i
/"
C i
16 3.5-2 AMENDMENT BE A4Ay aumeN, 1981
I Insert A s
Non-seismically supported piping and components were considered as a source of gravity missiles.
E e
e hiimum mmm eii im
a.
Components are located within separate cubicles.
O b.
Adequate spatial separation between redundant ccaponents and electrie circuits.-
c.
Installation of physical barriers, such as concrete block, con-I crete or steel walls.
4.
Equipment Design O
Structures or components. an, by virtue of design, withstand ' impact of postulated missiles without loss of function.
5.
Strategic Orientation a
Equipment or co=ponents are so orien'ted that postulated mis'sile"
~
paths are directed away frem equipment and, components requiring protection.
6.
. Distance Equipment is located out of range of postulated missiles.
Safety-related instrument and control components and instrument impulse lines outside the reactor buildit.g, which are required for safe plant shutdown, are not in the paths of postulated missiles.
z (,,
-> Xeseer B Safety-related systems and components outside the reactor building that
/,
are required for safe plant shutdown under all plant conditions are listed in Table 3.5-2.
f-3.5-4 I
s j) e J 2. 6 my, s9 e
Insert B A seismic induced physical interactions program ensured that safety-related systems and components required for safe plant shutdown would not be prevented from performing their intended safety functions as a result of physical interactions with non-safety related structures, systems and components. This p'rogram consisted of seismically supporting such items as non-safety cable trays, HVAC ducts and electric cabinets in areas containing safety-related components required for safe plant shutdown.
Plant walkdowns were then carried out to identify for future evaluation other possible missile sources such as non-safety piping, tanks, pumps, motors and light fixtures, which, if their supports failed, could impact on safety-related systems and components required for safe plant shutdown. Additional supports were provided where required.
L e
V
Within the reactor building there are no gravity missiles which could constitute a threat to safety class equipment or systems. Cratings, 14 handrails and stair treads inside the reactor building are fastened in l
place by velds, pins or clamps. Overhead light fixtures, located above l
safety related equipment, are installed by means of hangers capable of withstanding seismic forces.
tQ T NSEgr C ailu of s ismica ly and no -seismi -ally sup rted piping has been a
yzed nd is escribed 'n Sect' n 3.6.
e non- (ismicall,y support d pipin insid the rea or buil ng is r' derate e ergy pip
- and i po ulat to crac only, discus d in Se ion 3.6
.1.4.
is is i 4
[
confo ance wi the cr'teria de cribed
- Branch echnic. Positi MEB /
1 3
, Para h B.2.
Io grav' y missi s are p tulat to r t f failure o non-seasmically suppor, o piping j
3.5.1.2.2 Missile Protection Methods The design basis is that postulated missiles generated within the reac-tor building in coincidence with a loss of coolant accident, do not loss of function of any redundant engiacered safety feature.
cause Protection of safety-related equipment and redundant components of vital systems from postulated missiles is accomplished by one, or more, of the methods described in Section 3.5.1.1.2.
1 Thicknesses of barriers, including walls, slabs and specially designed barri.ers, which protect safety class equipment or systems satisfy the criteria discussed in Section 3.5.3.
Thus, scabbing or the generation of secondary missiles from the non-impacted face of such a barrier is 5
Precluded. Concrete fragments ejected from the impacted face (spalling ef fect), if any, will have energies too low for consideration as mis-siles due to the small weight and velocity of such fragments. Fragments and the initial missile constitute no threat as gravity missiles to safety class equipment or r ' stems as secondary missiles during the drop 14 following impact.
zG 3.5-8 AMENDMENT H
._7
.,9 NV IVS/
i Insert C Non-seismically supported piping and components were censidered as a source of gravity missiles.
k l
4 5
b 1
e d
Safety-related-instrument and control components and instrument impulse lines inside the reactor building, which are required for safe plant shutdown, are not in the paths of postulated missiles.
Im ENSE AT ^9 2b
' Safety-related structures, systems and components inside the reactor
}
building which are required for safe shutdown of the plant under all operating conditions are listed in Table 3.5-4.
3.5.1.3 Turbine Missiles
)
Turbine missiles are discussed in Reference [3 ].
i l
s l
l l
26 3.5-8a AMENDMENT f4
- , ' 'O MA),' /15) t I
Insert D A seismic induced physical interactions progran en;ared ths.t safety-related systems and ccmponents required for safe plaa; shu cvwn would noc be prevented from performing their intended safety functions as a result of physical interactions with non-safety related structures, systems and components. This p'rogram consisted of seismically supporting such items as non-safety cable trays, HVAC ducts and electric cabinets in areas containing safety-related components required for safe plant shutdown. Plant walkdowns were then carried out to identify for future evaluation other possible missile sources such as non-safety piping, tanks, pumps, motors and light _ fixtures,.which, if their_ supports failed, could impact on safety-related systets and components required for safe plant shutdown. Additional supports were provided where required.
I e
+
d
d 3.7.1.5 Effect of Reservoir Induced Seismicity x
Based on the Supplemental Seis=ologic Investigation Report, Virgil C. Summer Nuclear Station, Unit 1, Docket No. 50/395, by South Carolina Electric & Gas Company, December,1980, the maximum possible seismic event that might be induced by Monticello Reservoir is of local magnitude M =4.0.
For an average t
stress drop of 25 bars, and source distance of 2.0 Km, the Brune model and random vibration theory give a ZPA value of 0.14g which is less chan the SSE value. Thus, there is no effect on structural or equipment design.
However, the NRC staff took the position that M =4.5 is the maximum possible t
j reservoir induced event, while the ACRS consultants took a more conservative position of M =5.0.
For an average stress drop of 25 bars and source distance t
of 2.0 Km, the Brune model and random vibrarien theory give a ZPA value of 0.22g for the M =4.5 event. For an averagc stress drop of 25 bars and source distance t
l of 3.0 Km, the Brune model and random vibration theory give a ZPA value of 0.2g for the M =5.0 event. For an average stress drop of 25 bars and source distance L
of 4.0 Km, the Brune model and random vibration theory give a ZPA value of.22g for a M =5.5 event. Even though 0.22g is higher than the site SSE value, the t
built-in conservatism of design can be used to justify the adequacy of plant design.
The structural damping of plant design is 2% for the SSE while Regulatory Guide 1.61 allows 7%.
Comparison of the 2% SSE spectrum and 7% near field mean plus one standard deviation spectrum anchored at 0.22g is shown in Figure 1, Appendix X of the Supplemental Seismologic Investigation Report.
This comparison indicates that the SSE spectrum is exceeded only in the frequency region higher than approximately 9 Hertz. Among all of the Seismic Category I structures, only the Interior Concrete Structure of the Reactor Building has a dominant frequency higher than 9 Hertz.
The built-in conservatism of the artificial time history method can be used to justify the adequacy of the Interior Concrete Structure and equipment design.
Amendment 26 May, 1981
,. Thirty-six (36) components of time histories with typical spectra as shown in Figures 2 to 5. Appendix X of the Supplemental Seismologic Investigation Report, were used as input to the structural seismic model. The comparison of the SSE floor response spectra and the mean value floor response spectra of the 36 time histories are shown in Figures 6 to 35, Appendix X of the Supplemental Seismologic Investigation Report. As shown in the comparison, the SSE floor response spectra exceed the near field mean value floor response spectra by a large margin in the majority of the frequency regions except between 20 and 30 Hertz. In this region, the SSE floor response spectra are exceeded by a small amount. An evaluation of the Residual Hect Removal System and the Emergency Feedwater System indicates that the typical margins of the current hardware design are more than sufficient to cover the slight exceedance of the SSE floor response spectra.
i Amendment 26 May, 1981