ML20082J860
| ML20082J860 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 11/30/1983 |
| From: | PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | |
| Shared Package | |
| ML20082J815 | List: |
| References | |
| NUDOCS 8312020335 | |
| Download: ML20082J860 (40) | |
Text
__ _
LIMERICK GENERATING STATION UNITS 1 E 2 DESIGN ASSESSMENT REPORT REVISION 6 PAGE CHANGES The attached pages, tables, and figures are considered part of a controlled copy of the Limerick Generating Station DAR. This material should be incorporated into the DAR by following the instructions below.
i After the revised pages have been inserted, place the page that i follows these instructions in the front of Volume 1.
REMOVE INSERT VOLUME 1 Table 1.3-2 (pgs 1,2,3,7,11)
~
Table 1.3-2 (pgs 1,2,3,7,11)
Table 1.4-1 (pgs 1 thru 3) Table 1.4-1 (pgs 1 thru 4)
Page 4-111 Page 4-111 Pages 4.2-15 s -16 Pages 4.2-15 & -16 Tables 4.2-2 thru -4 Tables 4.2-2 thru -4 Figures 4.2-17 thru -23 Figures 4.2-17 thru -23 Table 5.7-1 (pgs 1 s 2) Table 5.7-1 (pgs 1 & 2)
Page 480.71-1 Page 480.71-1
)
1 l VOLUME 2 l
Appendix J l
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l O
8312O20335 831130 PDR ADOCK 05000352 A PDR
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O THIS DAR SET HAS BEEN UPDATED TO INCLUDE R VISIONS THROUGH b DATED /( 8 3 .
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COMPARISOh I L9aQ_9t_Eher9 sed 99 -
I. LOCA R. slated Hydrodynamic Loads A. Submerged Boundary Loads During Vent Clearinq B. Poolswell Loads
- 1. Poolswell Analyti-cal Model s a. Air-Bubble
) Pressure
- b. Poolswell Elevation 51t f 5": Im?o P R ~ ~.^0
- c. Poolswell l Velocity Q v, ,
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LGS DAB TABLE 1.3-2 (Page 1 of 11)
OF LGS LICENSING DASIS WITH NBC ACCEPTANCE CRITcBIA Criteria LGS HEC _AgggptAngg_griteria _fo3 Igg _ Positiom l24 psi overpressure added NUREG-0487 Acceptable
,o Icen1 hydrostatic t Supplement 1 prassure below vent exit l(c211s and basemat) -
Ainnar attenuation to
! pool surface.
Also Available On Aperttre Card
.Cnic31cted by the pool- NUREG-0487 Acceptable
!stell analytical model (PSAM) used in calcula-Ition of submerged boun-
'dcry leads.
300 PSAM with polytropic NUREG-0808 Acceptable. Used J expanent of 1.2 to a mar- NURIG-0487, I icun stell height which Supplement 1 i So the greater of 1.5 x vant submergence or the alovntion corresponding Go tha drywell floor uplift AP=2.5 psid.
Velocity history vs. NUREG-0808 Acceptable. Used J pool clevation predic- NURIG-0487. PSAn A tcd by the PSAM used to calculates velocity j c: puto impact loading without 1.1 multi- J sn enall structures and plier. Bowever, l Braq cn gratings between poolswell velocity A Snitici pool surface and multiplied by 1.1 J anxinua pool elevation when used in force i 2nd steady-state draq code. j bett:an vent exit and aaxiona pool elevation.
Annlytical velocity vnriation is used up to taximum velocity.
Rev. 6, 11/83 8312020335 -O( ,
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L9Bd_9E_fhfD95909B
- d. Poolswell Acceleration
- e. Wetwell Air Compression s
/
- f. Drywell ,
Pressure
- 2. Loads on Submerged
- Boundaries .
t j
j l
i
! 3. Impact Loads i a. Small
- Structures i
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l LGS DAB DLE 1.3-2 (Continued) (Page 2 of 11)
Criteria LGS
" _AGG D1ARER_MI1teria _ Source Positiom icuo velocity applies hercafteruptomariana aols w311. PSAM predic-ed volocities multiplied r a f actor of 1.1.
=calarction predicted NUREG-0487 Acceptable r the PSAM. Pool colcrction is used in ha calculation of acalerttion loads on aboorged components 2 ring poolsw ell.
etwall air compression NUREG-0487 Acceptable. Maximum i s calculated by PSAM Supplement 1 poolswell elevatiom i ansistent with maximum calculated in i aolswall elevation accordance with i L1culcted in B.1.b NURIG-0487, J bove. Supplesemt 1. A eth ds of NEDM-10320 NUREG-0487 Acceptable ad NEDO-20533 Appendix
. Us:d in PSAM to cal-Alato poolswell loads.
txioun bubble pressure NUE4G-0487 Acceptable cadicted by the PSAM id:d uniformly to local rdrcstctic pressure alcw v nt exit (walls ud bascaat) - linear
- tenuntion to pool surf ace. 'Also Available an
) plied to walls up to max- Aperture Card ca poolswell elevation.
35 x Pressure-Velocity NUREG-0608 Acceptable l pers lation for pipes id I-brams based on MNP icpulse data and hP" J (T nt pOcl assumption. "
U trinblo pulse duration. '. A J ! J -- --
in \ -
ku.s C /k 3 )
Bev. 6, 11/83 i 8312020335-0 2_
T a\ -
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j b. Large
. Structures
- c. Grating i
i l
i 4. Wetvell Air
) Compression l
j a. Wall Loads 1
i i .
- o. Diaphraqa j
'}
cv Upward Loads i
?
l S. Asynaetric LOCA i Pool i
t l C. Steam Condensation and i Chuqqing Loads
- 1. Downconer Lateral
- Loads I
- a. Single-Vent o Loads (24 in.)
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1 LGS DAB bE 1.3-2 (Continued) (Page 3 of 11)
Criteria LGS
_AEG2RtaDG2_SIiteria _ Source Position e - Plant unique load NUREG-0487 Not Applicable re applicable. No laroc structures 1 swell drag vs. grating area EUREG-OuG8 Acceptable i
[ relation and pool velocity elevation. Pool velocity PSAM. Poolswell i
ln q thenultiplied by dynamic l
d factor.
ect application of NUREG-0487 Acceptable I
iPSAM calculated ssure due to vetvell
.pression.
psid for diaphragm NUEEG-0808 Acceptanle.. Calculated dings only. diaphrags upilft AP
= 10. 6 psid (Figs. 4.2-3, 4. 2-4) .
Design diaphragm uplift AP = 20 psid.
20 percent of max- NUREG-0808 Acceptacle j u bubble pressure i tically applied to of the submerged ndary.
Also Available On Aperture Card
~
nic load to end of NUBEG-0808 Acceptanle
. Half sine wave a duration of 3 to 4*
and corresponding num amplitudes of 0
f ()
o 10 Kluf.
f ni rj
- ) E f ] [7
% CARD
~
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Bev. 6, 11/83 ,
8312020335-o 3
(_----- - - - , - - _ _ - - _ . _ _ _ - _ _ _ _ - - - _ _ - - - - _ _ _ - - - _ _ _ - - _ - _ _ _ _ _ _ _ _ - _ _ _ - - _ - _ _ - - _ - _ - - _ _ _- _ _ - _ _ _ _ - - - _ - - _ _ _ _ - -
I i
I L944_9E_Eh9D959D9D C. T-Quencher Tie Down Loads
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LGS DAR LBLE 1.3-2 (Continued) (Page 7 of 11)
Criteria 1GS IRG_AGGRR1ARgg__ Criteria _ Source _
Position
- b. DLWL shall be ,
equal to the dif-ferences between I the plant downconer I oxit olevation and !
the quencher center I line elevation (a)
- 3. Frequency Range NURcG-0802 Acceptable (DAB Section 4.1.4.1)
For the single valve and
.asycaetric load cases, the tiaevise compression cf the design pressure cignatures shall be in-crcnsed to provide an overall dominant fre-quency range that ex-tends up to 11 Hz.
I. Vertical Pressure NUREG-0802 Acceptable Dictribution The maxiana pressure caplitudes shall ne cpplied uniformly to the containment and pedestal valls up to ca oleration 2.5 feet chove the quencher Also Available On centerline followed Aperture Card by linear attenuation to zero at pool curf ace.
'ha T-quencher load speci- NUREG-0802 Acceptable ficctica described in SSES
>AR Section 4.1.2, as inter- A prat;d in Sections 2.2.3 l ind 2.3.3 of NUREG-0802, A L1y ba applied for evaluation df quencher and quencher 1,hni- [ D f3
- ; psi.'" 1 j
p l\ b
' "o cc- '
pABERTURE Lu CARD Rev. 6, 11/63 88' o o33s W
e 1
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Lgad gr_EhsD999D9D
- 8. Seismic Slosh Load V. Confirmatory In-plant Tests of SRV Discharge
~A. SRY Load Specification B. Pool Temperature Specification (Thermal Mixing) l l
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LGS DAR
- BLE 1.3-2 (Continued) (Page 11 of 11)
Criteria LGS la.G_Accep.Luca_ criteria Source _ Position 12th dology for establish- WUREG-0487 load is negligible aq.locds resultihg from when compared to design basis loads i isaic slosh to be tvaluated on a plant unique (Section 4.2. 3. 7) stris.
En tho event that an applicant NUREG-0802, Acceptable. No sannot demonstrate, to the staff's Appendix A in-plant test is saticfcction, equivalence in any required. DAR af the areas cited in acceptance Section 4.1.1.1
- ritoria A.1.1 through A.1.1 of denomstrates the NUREG-0802, Appendix A, in-plant acceptability of using benfircatory testing may be employed the SSIS SRV load Lo anconstrate the applicability specification for LGS.
bf tho acceptance criteria' for individual plants. Such testing, Lf proposed, should conform to the
' uidelines set down id NUREG-0 763.
q Acceptable. Tae LGS hh2 acceptanility of the safety NUREG-0763 pool thermal miximq 3cliof valve in-plant confirmatory analysis will be
{cstprogramsnallbebasedon acnforcance with the guidelines confirmed by in-plant bpecified in Sections 6, 7, and testing and analysis.
b of NUREG-0763. If the ~
bpplicant/ licensee elects not bo perf orm the SRV in-plant tests, justification should be provided i j Bollocing the guidelines specified i A
pn Ssction 4 of NUREG-0763.
w --
V F LLl 5
&DO g g Also Availabic on Of Aperture Card 4
n LLI O k O--
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Rev. 6, 11/83 ,
8 312 0 26 3 53. -Og
LGS DAR
() CONTAINMENT DESIGN PARAMETERS TABLE 1.4-1 (Page 1 of 4)
Suppression Drywell Chamber DRYWELL AND SUPPRESSION CHAMBER Internal design pressure, psig 55 55 External to internal design 5 5 differential pressure, psid Drywell deck design differential 30 20 pressure, psid downward upward Design temperature, 0F 340 220 Drywell net free volume, at 243,580(a) suppression pool low water level, including downcomers, ft*
Suppression chamber free volume including pedestal interior, ft8
() Low water level 159,540ca) l High water level 147,670(3) l Suppression pool water volume ,
including pedestal interior, ft*
Low water level 122,120(a) l High water level 134,600(8) l Suppression pool net surface area, fta l Outside pedestal 4974 l Inside pedestal 293 l Supression pool depth, ft Low level 22' Normal level 23' High level 24'-3" O
Rev. 6, 11/83
LGS DAR O TABLE 1.4-1 (Cont'd) (Page 2 of 4)
Suppression Drywell Chamber VENT SYSTEM Number of downcomers 87(*) l Nominal downcomer diameter, ft 2 ,
Downcomer area (each), fta 2.95 l Downcomer submergence, ft Low water level 10' Normal water level 11' High water level 12'-3" Downcomer loss coefficient (including exit loss) 2.18(3) l
/~'s SAFETY. RELIEF VALVES
\J .
Number
~
14 Spring Set Pressutes, Mass Flow Rates:
Mass Flow (Ibm /hr) at 103% of Spring Valve Set Pressure (psic) Set Pressure A 1150 917,000 B 1150 917,000 C 1150 917,000 D 1140 909,000 E* 1140 909,000 F 1150 917,000 G 1150 917,000 H* 1130 901,500
() J 1130 901,500 Rev. 6, 11/83 l
-_ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ l
l LGS DAR O TABLE 1.4-1 (Cont'd) (Page 3 of 4)
Mass Flow (lbm/hr) at 103% of Spring Valve Set Pressure (psic) Set Pressure K* 1140 909,000 L 1130 901,500 M* 1140 909,000 N 1130 901,500 S* 1140 909,000
- ADS Valves SAFETY RFLIEF VALVE DISCHARGE LINES Nominal Diameter 12" Length, Number of Bends, and Air Volume for each SRV Pipe:
Length (*) Volume (2)
Valve Bends (ft) (fta)
A ,
9 142.2 94.3 B 7 115.1 74.2 C 7 115.3 75.4 D 9 142.2 94.8 E 9 133.6 89.1 F 11 134.0 88.3 G 11 134.6 88.5 H 11 138.1 91.2 J 7 116.1 76.0 K 12 131.6 86.2 L 10 131.6 86.5 l O M 13 134.9 88.2 Rev. 6, 11/83
LGS DAR O TABLE 1.4-1 (Cont'd) (Page 4 of 4)
Length (1) Volume (a)
Valve Bends (ft) (ft3)
N 10 142.2 93.8 S 12 140.0 93.2
(*) Line lengths are measured from the valve to the quencher inlet.
(a) Air volume is calculated up to pool normal water level.
(a) These values vary slightly from those actually used in the analysis. The difference in analysis results is negligible.
(*) Four of 97 downcomers are capped (Appendix J).
O
~
O Rev. 6, 11/83 l
LGS DAR O CHAPTER 4 TABLES Number Title 4.1-1 These tables are proprietary and are through located in the proprietary supplement to this DAR .
4.1-41 4.2-1 Short-Term LOCA Loads Associated with Poolswell 4.2-2 Short-Term Drywell Pressures During Poolswell 4.2-3 LGS Plant-Unique Poolswell Code Input Data 4.2-4 Deleted l 4.2-5 LOCA Water det Loads 4.2-6 Deleted 4.2-7 Poolswell Air Bubble Loads 4.2-8 Poolsecil Water Friction Drag Loads 4.2-9 Deleted 4.2-10 Maximum Load on Submerged Structures 4.2-11 Component LOCA Load Chart for LGS 4.2-12 Wetwell Piping LOCA Loading Situations O
4-111 Rev. 6, 11/83
._ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ )
LGS DAR O the structural loading conditions in the containment because they are the basis for other containment hydrodynamic phenomena. The response must be determined for a range of parameters such as break size, reactor pressure, and containment initial conditions.
4.2.4.1 Desian Basis Accident (DBA) Transients The DBA LOCA for LGS is conservatively estimated to be a 3.538 fta break of the recirculation line. This transient results in the maximum drywell pressure and therefore governs the LOCA hydrodynamic loads. The LGS-unique assumptions and input for the analysis are given in FSAR Section 6.2.1. Drywell and wetwell pressure and temperature reponses are shown in Figures 4.2-11 and 4.2-12. This description of the transient does not include the effect of reactor subcooling.
t 4.2.4.2 Intermediate Break Accident (IBA) Transients The worst-case intermediate break for LGS is a 0.1 fta break of a liquid line. The drywell and wetwell pressure and temperature O responses are shown in Figures 4.2-13.and 4.2-14.
description of the transient does not include the effect of reactor subcooling This 4.2.4.3 Small Break Accident (SBA) Transients Plant-unique SBA data for LGS is not available. The wetwell and drywell pressure and temperature transients for a typical Mark II containment are used to estimate the LGS containment response'to these accidents. These curves are-shown in Figure 4.2-15 (extracted from Reference 4.2-6).
4.2.5 LOCA LOADING HISTORIES FOR LGS CONTAINMENT COMPONENTS The various components directly affected by LOCA loads are shown schematically in Figure 4.2-16. These components may in turn load other components as they respond to the LOCA loads. For example, lateral loads on the downcomer vents produce minor reaction loads in the drywell floor from which the downcomers are supported. The reaction load in the drywell floor is an indirect load resulti.ng from the LOCA and is defined by the appropriate structural model of the downcomer/drywell floor system. Only the O direct loading situations are described in detail here.
Table 4.2-11 is a LOCA load chart for LGS. This chart shows 4.2-15 Rev. 6, 11/83
4 LGS DAR O TABLE 4.2-2 SHORT-TERM DRYWELL PRESSURE DURING POOLSWELL Time (sec) Pressure (psia) 0.0000(1) 36.11 l 0.0600 36.29 0.1000 36.82 0.1*,00 37.08
- 0. 500 37.57 0.2000 38.04 0.2400 38.49 0.2800 38.91 0.3200 39.30 0.3600 39.67 0.4000 40.01 0.5000 40.75 0.6000 40.75 0.7000 41.39 O.8000 42.07 1
0.9000 42.30 1.0000 43.56 1.1000 44.603 1.2000 45.36 1.3000 46.08 1.4000 46.75 I
(1) Represents the beginning of the poolswell phase, which starts 0.7107 seconds after the break, i
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Rev. 6, 11/83
LGS DAR O TABLE 4.2-3 LGS PLANT UNIQUE POOLSWELL CODE INPUT DATA Downcomer area (each) 2.95 ft2 Suppression pool free surface area 4973.89 fta (outside pedestal)
Maximum downcomer submergence 12.25 ft Downcomer loss coefficient 1.11 l (without exit loss)
Number of downcomers 87 Initial wetwell pressure 15.45 psia Wetwell free air volume 149,425 ft3 Vent clearing time 0.7107 sec Slug velocity in downcomer O at vent clearing 3.096 ft/sec Initial drywell temperature 1350F Initial drywell relative humidity 0.20 Downcomer friction coefficient, f 0.0115 (nominal)
Bubble initialization parameter (nominal) 50 0
Rev. 6, 11/83
- - - - - - - - - - - - - - - _ _ . . - - _ J
4 i
LGS DAR .
TABLE 4.2-4 i
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Rev. 6, 11/83 i
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j WETWELL/DRYWELL P&T DURING POOLSWELL
- WETWELL/DRYWELL "
P&T WETWELL/DRYWELL P&T DURING LOCA ***
DURING LOCA **
~.
POOLSWELL AIR
{ BUBBLE
- s -
MIXED FLOW 8 C.O. * * *
- STEAM FLOW l CHUGGING "
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$ O C BREAK CLEAR POOLSWELL HT. COMPLETE COMPLETE
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- WETWELIJDRYWELL 35 P&T DURING LOCA **"
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DOWNCOMER WATER JET l LOAD
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. LGS DAR TABLE 5.7-1 (Page 1 of 2)
LOAD COMBINATIONS AND ACCEPTANCE CRITERIA FOR ASME CLASS 1, 2 AND 3 NSSS PIPING, EQUIPMENT, AND SUPPORTS i
DESIGN EVALUATIONC3) SERVICE LOAD COMBINATION BASIS BASIS LEVEL N + SRV Upset Upset (B)
(ALL)
N + OBE Upset Upset (B)
N + OBE + SRV Emergency Upset (B)
(ALL)
N + SSE 4 SRV Faulted Faulted (D)(1)
(ALL)
, N + SBA + SRV Emergency Emergency (C)(1)
N + SBA + SRV Emergency Emergency (C)(*)
'O
'^"
N + SBA/IBA + OB'E + fiRV Faulted Faulted (D)(1) l (AUS)
! (ADS)
N + LOCAca) + SSE Faulted Faulted (D)(*)
i i LOAD DEFINITION LEGEND N - Normal loads (e.g., weight, pressure, temperature, etc)
OBE -
Operating basis earthquake loads SSE - Safe shutdown earthquake loads SRV - Safety / relief valve discharge induced loads from two 1 adjacent valves (one valve actuated when adjacent valve is cycling)
O Rev. 6, 11/83
L .
, LGS DAR TABLE 5.7-1 (cont'd) (Page 2 of 2)
SRV -
Loads induced by actuation of all 14 safety / relief F ALL valves that activate within milliseconds of each other (e.g., turbine trip operational transient)
SRV -
Loads induced by the actuation of all 5 safety / relief ADS valves associated with automatic depressurization system that actuate within milliseconds of each other
, during the postulated small or intermediate size pipe rupture.
LOCA -
Loss-of-coolant accident associated with the postulated pipe rupture of large pipes (e.g., main steam, feedwater, recirculation piping)
LOCA: -
Poolswell drag / fallback loads on piping and l components located between the main vent discharge 4
outlet and the suppression pool water upper surface LOCA, -
Poolswell impact loads on piping and components located above the suppression pool water upper i surface I) LOCA 3 -
Oscillating pressure induced loads on submerged piping and components during condensation oscillations LOCA. -
Building motion induced loads from chugging LOCAs -
Building motion induced loads from main vent air clearing l LOCA. -
Vertical and horizontal loads on main vent piping LOCA 7 -
Annulus pressurization loads SBA -
Abnormal transients associated with a small break accident IBA -
Abnormal transients associated with an intermediate l
break accident.
1 l
(1) All ASME Class 1, 2 and 3 piping that are required to function
- for safe shutdown under the postulated events are designed to meet the requirements described in NEDO-21985 (Sept. 1978).
(a) The most limiting case of load combinations among LOCA:
through LOCA 7.
(8) Evaluation basis in accordance with NRC requirements.
{
Rev. 6, 11/83 J
1 . .
LGS DAR DUESTION 480.71
. Concerns regarding the capability of the vacuum breaker to l perform its function during the pool swell and chugging phases of LOCA have been raised. Provide the design changes, if any, that have been implemented to resolve this concern.
RESPONSE j The four downcomers on which the wetwell-to-drywell vacuum breakers are mounted have been capped, thereby eliminating the adverse effects of the chugging phenomenon on the vacuum breakers. c The vacuum breaker has been redesigned so that it will successfully perform its given task during and after poolswell.
The adequacy of the redesign has been demonstrated by analysis and test.
The redesign and requalification program that considers the effects of the poolswell and chugging events was initiated and
( funded by three utilities. l
)
DAR Appendix J has been added to provide details of the wetwell-to-drywell vacuum breaker and downcomer capping adequacy assessments, i
i t
lO 480.71-1 Rev. 6, 11/83 l, -. . .
LGS DAR O APPENDIX J WETWELL-TO-DRYWELL VACUUM BREAKER AND DOWNCOMER CAPPING ADEQUACY ASSESSMENT TABLE OF CONTENTS J.1 Introduction J.2 Design Assessment J.2.1 Vacuum Breaker Cycling during Poolswell J.2.2 Vacuum Breaker Cycling during Chugging J.2.2.1 Downcomer Capping Design Assessment J.2.2.1.1 Downcomer Modifications J.2.2.1.2 Containment Evaluation J.2.3 References O
J-i Rev. 6, 11/83
i j
j LGS DAR
>O APPENDIX J l
! FIGURES !
Number Title J.2-1 Locations of Capped Downcomers with Vacuum Breakers l j J.2-2 Details of Capped Downcomer i I ,
i iO l
l I
O J-il Rev. 6, 11/83
LGS DAR O APPENDIX J J.1 INTRODUCTION
- In April 1981, the ACRS e] pressed concern regarding the psiential 1 pool bypass from a stuck-open wetwell-to-drywell vacuum breaker.
! This concern stems from the fact that following the onset of a LOCA about 20 seconds into the transient, the chugging phenomenon takes place. This rapid steam condensation will cause repeated and strong dynamic under and overpressure conditions in the downcomer. As a result of this pressure variation, the vacuum j breaker attached to the downcomer may open.
Because chugging is a repetitive phenomenon, the vacuum breaker may be called on to function in a cyclic manner during these intermittent steam condensation events. These potential opening j and closing impact loads could exceed the original design basis of the vacuum breakers. Failure of a vacuum breaker to close
] during this time could result in steam bypass of the suppression pool and subsequent pressurization of the wetwell air space, thms jeopardizing the integrity of the containment.
4 0 .
In July 1981, the NRC staff was informed that the' Mark II owners who have vacuum breakers attached to the downcomer were conducting a joint qualification test program to demonstrate the operability of the vacuum breaker under this intermittent steam condensation loading. The Mark II owners also identified the potential adverse effect of poolswell on the performance of
, vacuum breakers'. Because the wetwell air space will pressurize
- during the poolswell event, the resulting differential pressure '
I will cause the vacuum breaker to cycle open and then cycle closed when the pool falls back to the normal water level. The l
potential opening and closing impact load could exceed the original design basis of the vacuum breakers.
J.2 DESIGN ASSESSMENT 5
J.2.I VACUUM BREAKER CYCLING DURING POOLSWELL To qualify the Limerick yacuum breakers to withstand the dynamic effects of poolswell, design modifications to the vacuum breakers have been implemented based on results from the Anderson Greenwood Company (AGCo) vacuum breaker test program. The O modifications and test program results have been transmitted to the NRC (References J.2-1 and J.2-2).
J-1 Rev. 6, 11/83
LGS DAR J 2.2 VACUUM BREAKER CYCLING DURING CHUGGING O
To qualify the Limerick vacuum breakers to withstand the dynamic effects of chugging, the four downcomers on which the wetwell-to-dryvell vacuum breakers are mounted have been capped. Capping the downcomers will eliminate the dynamic under and overpressures caused by the sudden steam condensation at the downcomer exit and eliminate the vacuum breaker cyclic actuation due to chugging phenomena. The locations of these capped downcomers are shown in Figure J.2-1.
J.2.2.1 Downcomer Capping Design Assessment J.2.2.1.1 Downcomer Modifications Figure J.2-2 shows a configuration of a nodified downcomer with vacuum breaker (typical of four). The modifications include installation of a cap, a 3-inch drain line, and a 1-inch weir at the dryvell entrance of the downcomer.
The capping design incorporates a 3-inch Schedule 160 drain line.
Water motion in the 3-inch drain line has been modeled.. As a result of this work, the drain has been extended 9 ft 7-3/4 inches above the downcomer exit plane. This extended length will prevent water from fountaining into the downcomer during the rapid drywell depressurization caused by the gross chugging at the downcomer exits. In addition, to prevent water from exiting the drain line during the chugging /CO phase of a LOCA, the drain line is extended 4 feet below the downcomer exit plane. Therefore, potential chugging /CO dynamic loading phenomena at the drain exit are precluded.
The addition of a 1-inch weir at the drywell entrance of each capped downcomer is designed to limit the maximum ECCS flow into these downcomers during the recirculation mode after a LOCA. The 3-inch drain line is capable of passing this limited flow of ECCS water while preventing the downcomers from being filled to the vacuum breaker elevation.
J.2.2.1.2 Containment Evaluation Capping 4 out of 87 downcomers requires an evaluation to determine its effect on the containment design basis LOCA loading conditions and safety margins. To resolve this concern, l
Rev. 6, 11/83 J-2
I .
LGS DAR O Bechtel's computer program COPDA was used to evaluate the drywell conditions based on 83 and 87 downcomers, respectively. The results indicate that there is no significant change in either drywell pressure and temperature or steam blowdown rate through the downcomers for the capped and uncapped situations.
Based on this analysis, capping 4 out of 87 downcomers will have no adverse effects on the Limerick containment safety margins resulting from design basis LOCA loads, as defined in DAR Section 4.2, including poolswell loads, containment functional pressure, submerged structure loads, boundary loads, and asymmetric effects.
J.
2.3 REFERENCES
J.2-1 Letter, D.M. O'Connor (Mark II Owners Group) to Dr. R.W.
Houston (Assistant Director, Division of Systems Integration, NRC), "AGCo Vacuum Breaker Test Program,"
June 17, 1983.
J.2-2 Letter, J.S. Kemper (Philadelphia Electric Co.) to A. Schwencer (NRC), "AGCo Wetwell/Drywell Vacuum Breaker O- Test Program," July 6, 1983.
O J-3 Rev. 6, 11/83
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