ML20129D414

Foam Transport in La Salle Svc Water Tunnel

ML20129D414
Person / Time
Site:	LaSalle
Issue date:	09/23/1996
From:	FAUSKE & ASSOCIATES, INC.
To:
Shared Package
ML20129D379	List: ML20129D373 ML20129D408 ML20129D414
References
FAI-96-86, NUDOCS 9609300072
Download: ML20129D414 (25)

Text

' SEM BY: 8-23-96 ; 15:51 ; FAI - NO. SHORE-2502 ;# 2 l

i i

FM/96-86 FOAM TRANSPORTIN THE LASATIE SERVICE WATER TUNNEL Submitted To:

Commonwealth Edison Company Prepami By:

Fauske & Anociates, Inc.

16WO70 West 83rd Street Burr Rkige, Illinois 60521 September,1996 9609300072 960923 PDR ADOCK 05000373 p PDR l-WATM,aG.RFr

~ SENT SY: 9-23-96 ; 15:51 ; FAI - NO. SliORE-+2502  ;# 3

1.0 INTRODUCTION

, in May and June of 1996 a polyurethane foam mixture was iq}ected into the LaSalle i

service water tunnel. This tunnel is the supply for the emergency service water system (ESWS) i

, as well as the Non-Essential Service Water System (N-ESWS). SnWntly, foam pieces were observed to begin plugging some of the strainers for the nonessential service water system, l l

! which take suction from the top of the turmel. Investigations into the cause of this showed a j substantini amount of foam material in the N-ESWS. Once this was determined, there were i expdf Al investigations performed at the Iowa Institute for IIydraulic Research (IIHR) to examine the response of polyurethane foam pieces to anticipated flow conditions in the service 1 water tunnel both during normal and emergency situations.

l i

j This report analyzes the experimental infan==*ian as well as the flow distribution in the IIHR experiments in relationship to the LaSalle service water tunnel. In particular, the behavior l

observed in the Iowa experiments is characterized to determine whether the behavior overstates

the likelihood that such foam particulate couki enter into the ESWS. 'Ihis analysis provides the technical foundation for the application of the ITHR exid..catal data to the Probabilistic Risit l

Assessment (PRA), i.e. possible increase in core damage frequency that could have been caused by the presence of this material in the service water tunnel.

2.0 ANALYSIS The lasue with the foam response in the 12Salle service water tunnel is the duration over which the material was neutrally buoyant. As the material is introduced into the tunnel, it is negatively buoyant with a density of approximately 1.04 gm/cm3 . After the caring process the 3

expanded material has a density typically in the range of 0.9 - 0.95 gm/cm , with some small sampics observed to be about 0.98 gm/cm3 . This curing piW.c.s appearn to be complete within i 1

approximately ten minutes and, during this time, the material is essentially neutrally buoyant as the experiments have illustrated that samples rise and sinit multipic times dunng the curing interval. Only small particles exhibit this behavior. Once these become attached to a significant piece they arc then either positively buoyant with a specific gravity in the range of 0.98 to 0.8 1:WAfWAA.RFr

SENT SY: S-23-96 ; 15:52 ; FAI - NO. SHORE-2502  ;# 4 2

or negatively buoyant and remain on the bottom. Once the curing process is completed, the material is either floating on the upper surface or negatively buoyant if the curing process was water starved. I It is helpful to develop a perspective of the effective rise velocities for those pieces which are positively buoyant and compare these to the calculated flow distribution within the Iowa Institute of Hydraulic Research (IIHR) r.ar.riments, as well as the flow distribution in the service water tunnel. 'Ihc rise velocity for a piece of foam can be naarmaed by comparing the buoyant forces with the turbulent dag forces as given by ,

g (p, - pp) V, - Co A y *

(1)

In this expression, g is the acceleration of gravity, p, is the water density, pp is the foam  ;

density, V pis the volume of the foam particle and Ap is the effective cross-sectional area of f the rising piece. As a conservatism, let us assume that this foam mass has a disk-like

{

configuration such that the volume of the foam can be expressed by i V, - Ap L p (2) where Lpis the effective thicinnr**. Using this, the rise velocity is given then by e iM Ug=' Eh 1-PF C (3) n g Pwt where Cp is the drag coefficient for the rising disk. As illustrated in Figure 1, which is taken from Vennard (1954), the drag coefficient for a disk aligned perpendicular to the velocity is essentially unity. This is true for Reynolds numbers of about 1000 or greater and for the applications of interest here the Reynolds munbers are 30,000 - 40,000. Thus, the rise velocity calculation reduces to:

cm 7

PF U a- 2gL, 1

(4) i Ew o It@AhE86.RFr

~

SENT SY: 8-23-96 ; 15:53 ; FAI - NO. SHORE-+2502  ;# 5 3

Using this relationship and assuming a four inch (0.1 m) effective thickness of the example foam

particle, with a specific gravity of 0.95, the rise velocity is approximately 1 tt/sec (0.3 m/sec).

l As illustrated by the above equation, this rise velocity only changes as the square root of the effective length and the effective buoyancy. For cxample, if we were to consider the specific j gravity to be 0.98, the rise velocity would be 0.67 ft/sec (0.2 m/sec).

' i

l l These rise velocities can be comparul with the transverse velocities in the flow for both l s  !

i i

the IIHR experiments and the LaSalle service water amnel. These systems were evaluated I

assuming a two-dimensional flow field (parantial flow solution) to determine the relevance (and

! the level of conservatism) in the IIHR expenments in relation to the LaSalle tunnel behavior i

l (Epstein,1996). These two4imensional calculations were performed by assuming that the incoming flow is through a slit configuration. In reality, the system is threMimensional which j would result in the flows having somewhat higher velocities along the central core which is approximately a straight line between the haming location and the discharge port. However, these two41mensional analyses are sulTacient to illustrate the fundarpental relationship of the HHR experiments to the LaSalle service water tunnel configuration.

The results of the two dimensional flow application to the IIHR tests for a dimersionless incoming flow of unity and an exit flow of unity is illustrated in Figure 2. These values can be multiplied by a sp~ified inlet flow, which would be 3 ft/sec in the Iowa test (approximately 1 m/sec). This approximates the flow velocity distribution in the experiments. In particular, the results shown in Figure 2 are for no transverse flow and only flow coming in through the suction port (designated A in the experiments) and out through the discharge port (designated C in the experiments). 1 As illustrated in Figure 2, the dimensionless velocity vectors have magnitudes typically in the range of .4 to .6 which means that for an assumed incoming velocity of 3 IVsec the transverne velocity is about 1.2 to 1.8 ft/sec (0.4 to 0.6 m/nec). These velocities are cos,.r ble to but greater than the rise velocities for typical foam piocca used in the experiments. As a result, buoyant material released from the floor could be effectively transported in a lateral direction toward the discharge port.

wmm.arr

- - . - - - - -- _~. - - - - - . - _ _ __.

j ' SENT SY: 9-23-86 ; 15:54 ; FAI - NO. SHORE-2502  ;# 6 j 4 With the combination of rise velocity calculation and the approximate transverse velocity created in the IIHR experiments, we can calculate the zone where foam particles release from

] the floor would have a stmng possibility of being swept into the discharge piping. In particular, using the vector addition illustrated in Figure 3 we can calculate the distance away from the

discharge pipe where particles would not rise su.fficient fast to avoid being swept into the i l

discharge flow. Taking the rise velocity to be 1 ft/sec as calculated previously in the transverse velocity to be about 1.2 ft/sec (which correspends to a dimensionless velocity vector of 0.4), the angle 6 in Figure 3 becomes approximately 40*. In the IIHR test, the top of the discharge pipe is 4 ft above the bottom of the hydraulic tank. Consequently, the region of influence to fimi in

] Figure 3 would be approximately 5 ft. As a note of caution, the velocity vectors shown in

. Figure 2 indicate that the transverse velocity could be greater than 1.2 in some regions and it is also possible that the rise velocity is less than 1 ft/sec. Either of these would extend the region of influence. However, the simple vector addition shown in Figure 3 enables one to identify those locations where foam particles sownerged to the floor would not rise su&iantly

, rapidly to escape the discharge flow. ' Ibis region of influence is in agreement with that deduced by the experimenters.

Similar two dimensional calculations are shown in Figure 4 for the I mMalle service water tunnel. In the case addressed, flow comes in thmugh one location and is exhausted through another location that is ahnost directly acmss the channal. Here again, the calculations were '

performed in a two-dhnensional manner and ieyse,a.,t the flow in and out of slit openings as dimensionless values that are multiplied by the incoming velocity. As illustrated in the calculation, the dimensionless flow velocities are less in the central configuration and in fact less than the rise vclocity that would be anticipated for significant size pieces. Therefore, the region of influence would he ===Her than that ohnerved in the HHR tests. Hence, from this '

configuration we conclude that these experiments are a conservative representation of the foam behavior agirwam in the LaSalle service water nmnel.

Another calculation was performed to parametrically investigate the influence of an 4

adjacent intake port. In these calculations, the incoming flow was specified for the two ports and was parametrically varied from 0.8 - 0.2 for the distribution between the favored and more 1:WAh9H6.RFT

, SENTSY: 9-23-96 ; 15:55 : FAI - NO. SHORE-2502  ;# 7 5

l removed location to a situation in which the flow is evenly distributed, i.e. 0.5 and 0.5. 'Ihose parametric calculations are illustrated in Figures 5, 6 and 7 respectively. As expected, these show that the result of some flow coming through an adjacent port is to further reduce the flows in the central region of the tunnel near the discharge port. In particular, the transverse velocities are now in the range of one-half of the risc velocity. Therefore, even those pieces with marginal buoyancy (0.98) rise to the surface before they could he transported acmss half of the chanel w dth, 1 i

l L

1 l As discussed previously, some of the foam material was found on the floor of the service j tunnel and was thus negatively buoyant. It is interesting to perform calculations on the extent of lift that would be created by the induced service water hm=1 flows to assess the extent of negative buoyancy that would be nece=ary to impose these lift forces. Using the information in Figure 4, there is a dimensionless velocity of 0.22, as a reasonable average in the central l region which corresponds to an upward lift pressure

' 2 AP = p, U '

2 (5) r l s 3

of 3.5 x 10 psi (24 Pa). We can use this to determine the extent of negative buoyancy required to impose the lift using the expression AP = F - Ap Ly g (6)

A or solving for the density difference AP Ap = It5 0)

Using an effective thickness for the foam of 4 in. (0.1 m) we determine that a specific l

l gravity of 1.024 is sufficient to oppose the lift configuration annuming a perfect lift geometry.

l t

I i:PAf\E86.RFr

' S N SY: 2-23-86 ; 15:56 ; FAI - NO. SHORE-2502  ;# 8 f 3.0 CONCIESIONS From the analyses carried out with respect to rise velocities for foam pieces, the two-l dimensional velochy distribution in the IIHR test, the velocity distributions in the laSalle service water tunnel and the lift calculations for pieces that could be lying on the floor of the service hmnel, the following conclusions can be drawn.

1. The rise velocities for foam pieces that are of sufficient size to plug the suction j ports or the strainer inhke for the emergency service water system have rise velocities of approximately I n/sec and would rise to the top of the service water tunnel in about 10 secs.

2. The IIHR ng: ..a were performed in a way that is a conservative

, representation of the Imhlie service water hmnel f}oW distrhItion. More specifically, the potential for ingesting foam particulate in the discharge port is greater in the IIHR er;- .: .eri* than would be the case for the LaSalle service

water tunnat. Therefore, information taken directly from the Iowa experiments f and used in the PRA analyses overstates the hkelihood that material could be

! ingested into the emergency service water system.

! 1 l

! 3. The observations from the Iowa tests are readily understandable in terms of the j transverse and rise velocities and the possible path that a foam particle would

).

follow if it was submerged to the floor of the test apparatus and released in the flow stream. These analyses tend to show that there would be a region of j inflem of approximately 5 ft. around the discharge port. This is in agreement with the observations from the Iowa test.

5

'4. Given the substantial rise velochy and the two-dimensional velocity vectors in the Iowa test, those particles which rise to the top of the apparatus will remain there.

This was also observed in the experiments.

e IMAMH6.It Fr

' SENT EY: 9-23-96 ; 15:56 FAI - NO. SHORE-2502  ;# 9 4

5. The assessment of the potential flow for the LaSalle service water tunnel indicates that the velocity vectors from the entry of the water into the service water umnel and out through the discharge port are considerably less than those observed in the Iowa tent. Thus, the Iowa expi . ids conservatively represent the transverse flow in the Ish11e system. As a result, there is an even smaller region of influence for foam particulate in the l2Salle service water system than was

, observed in the Iowa test. Furthermore, with the reduced velocities, there is a i 4 ,

greater potential for particles which rise to the top of the service water tunnel and i remain there. I l

! 6. Parametric analyses for varying incoming velocities through parallel inlet ports l t  ;

i show that the participation of an adjacent inlet post further reduces the velocities in the service water tunnel even if only 20% of the incoming flow is eQ

through the adjacent port.

1

7. Analyses of the lift forces on negatively buoyant pieces must be less than j approximately 1.02 before lift forces would move the configuration off the floor of the service water tunnel given a perfect lift configuration.

l In anmmary, the analyses of the LaSalle service water hmnel and the HHR test show that the examinations which have been performed overstate the likelihood of foam particles being drawn into the discharge port. Thus, the analyses that have been performed with respect to the likelihood of initiating a core damage event are a conservative representation (overstatement) of l the likelihood of such an event could being initiated.

l I

i InFAnpMERFr

SENTSY: 8-23-96 ; 15:57 i FAI - NO. SHORE-c2502  ;#10

.s.

4.0 REFERENCES

Epstein,1996 memo to R. E. Henry on the Two-dimensional Pater *ial Flow Solution.

Vennard, J. K.,1954 Elementary Fluid Mechanics. Third Edition, John Wiley & Sons, New York.

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~ SENT ,BY: 9-23-86 ; 15'58 : FAI - NO. SHORE-2502  ;#12

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• SENTSY: 8-23-96 ; 15:53 ; FAI - NO. SHORE *2502  ;#13 11 4

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, SENT ,BY: 9-23 96 3 15:59 ; FAI - NO. SHORE-+2502  ;#14

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SENT.BY: 3-23-96 ; 16:00 : FAI - NO. SHORE *2502  ;#15

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, 0.0462, 0.0514 ,0.0580,0.0674 ,0.0790 .0.0930 ,,0.1103 ,0.t322 ,0.1609 ,0.19tra 0.2421

,0.0768 ,0.0784,0.0634,0.0912 ,0.1018 .0.1160 ,p.13S5 .p.1835 .,,g.2062 Q.2778 g4173 j i

,0.1127 ,0.1133 ,0.1153 ,0.1196 ,0.1272 J.1395 J.1586 J.1809 ,,Q,2390 ,,2J350 9J,$11 l 01052 ,0.i609 ,0.1548,,01509 J.lst7 j.15a5 J.1729 J. lees cL2424 pata owse9 1.0000 I t 0.2599 pc.2332 ,,0.2022 J.telt J.1702 J.1682 J.1745 J.1998 J.2164 A.2576 /0.3134 M.5637,,.b.34t2 ,,.D.2474 J.2007 J.1767 J.1656 0.1636 0.1888 A.1797 ,,0.1954 s 0.2112 n It000 4A961 J.asel _n2565.,.D.1968 J.1563 J.1505 .,0.1434 ,,0.1419 ,0.14 43 ,0.1457 ,0,1530 0.8395 Q3105 _0.213e J.lsse ,.,0.1411 J.1295 J.tle4 , 0.1845 , 0.1132 , 0.1134 0.1141 N

, 0.2138 0.1829 ,0.1493 ,,0.1254 .0.1096 .0.0994 ,0,0930 ,0.0091 ,0.0870, 0.0860, 0.0856

, 0.1143 , 0.8082 ,0,0902 .O.0003 ,0.0004 ,0 4745 ,0.0703, 0.0674, 0.0658, 0.0645, 0.0640

, 0 0701 . 0.0683, 0.0849, 0.0608. 0.0572 ,0.0541 , 0.0517 , 0.0499, 0.0487, 0.0478, 0.0474 0

j ,04S3 0;0449d.04)83 0._0420 ogs03,0.03,07 d.0E4,0.0j64,0 0356 0.035,1,, 0,,,0340 Figu2e 5 Plan vicw showing the two-dimensional distribution for the LaSalle service water tunnel with 80% flow in one port and 20% flow in an adjacent port. ,

_ - - . . . . - . _ - - = - . . .. ___ _ _

~

SEM SY: 9-23-96 ; 16:01 ; FAI - NO. SHORE *2502  ;#16 14 OJ037, 0.0037J.0037,0._0036, ojo36 040J5,0.0035 0.0_0343 0033 0 0.0034, 0.0033 1

] , 0.0053, 0.0053, 0.0053, 0.0052,, 0.0051, 0.0050, 0.0049, 0 0048, o 0047, 0.0047, 0.0047

, 0.0078, 0.0077, 0.0076, 0.0074, 0.0073, 0.0078, 0.0069. 0.006 7, 0.006s, 0.00e% 0.0065

, 0.0114 , 0.08t3 , 0 0111, 0 OLO9, 0.0104,, 0.0100, 0 0097. 0.0094, 0.0092, 0.0090, 0.0089

, 0.0172, 0.0t?0, 0.0164, 0.0137, 0.0149, 0.0142 , 0.0135, 0.0130, 0.0126 , 0.0123 , 0.0121

, 0.0269, 0.0262, 0.0248, 0.0231 ,, 0.021i , 0 4199 , 0.0187 , 0.0177 , 0.0170 , 0.0165 , 0.0162

, 0.04 45, 0.0422 , 0.038 2, 0.03 41, 0.0305, 0.0270. 0.0254, 0.0237, 0.022d , 0.0217 , 0.0212 0.0000

, 0.0839,0.07 33 ,,0.0602,0.0500, 0.04 26, 0.037 4. 0.0336, 0.0380, CA291, 0.0279. 0.0272

/0,2416 ,0.1332 .0.0917 , 0.0699, 0.0580, 0.0486, 0.0130, 0.0392, 0.0366, 0.0319, 0.0340 o,qogo Q)4 47 ,,Q.1963 ,0J200 ,0.08e7,0.0108, o.oS96, 0.0526, 0.0470, 0.0445, 0.0434, 0.04t2 0 3735 0.1906 ,0.1306 ,0.0994 0.0009. 0.0498, 0.0613 , 0.055 0 0.0523, 0.0500, 0.0486

, 0.1743 ,0a497 ,0.1217 ,0.1006 , 0.0860, 0.0758, 0.0883, 0.0631, 0 0595, 0.0571, 0.0558

, 0.1273 , 0.l204 , 0.1066 , 0.0972 , 0.0972, 0.0793, 0.0733, 0.0609, 0.0657, 0.0636, 0.0624

, 0.1066 , 0.1039 , 0.0986, 0.0924, 0.0883, 0.Onli , 0.n766, 0.0735, 0.0711 , 0.0694, 0.D684

, 0.0947, 0.0935, 0.0911 , 0.0es0, o.0048, 0.0888 , 0.0792, 0.0772, 0.0757, 0.0746, 0.0740

, 0.0005, 0.0861, 0.0852, 0.0841, 0.0830, 0.0019 , 0.00L0 , 0.0003, 0.0798, 0.0791, 0.0792

, 0.0799, 0.0799, 0.0802, 0.0006, 0.0011 , 0A056 , 0.0825, 0.0832 , 0.0830 , 0.0643, 0.06 4 7

, 0.0734 , 0.0740, 0.0752, 0.0770, 0.0791, 0.08:5 , 0.0839, 0.0863, 0.08e3, 0. Dees , 0.0009

, 0.0665, 0.0675, 0.0696, 0.o730, 0.0770, 0.0613 , 0.0656, 0.0900, 0.09su , 0.o968, 0.0987

, 0.0583, 0.0599, 0.0834, 0.0645, 0.0246, 0.0014 , 0 0883, 0.0951, 0.1012 , 0.1061 , 0.1094

, 0.0480, 0.0506, 0.0560, 0.0635, 0.0723 , 0.0520, 0.0921 , 0.1022 0.1117 , 0.8897 , 0.1258

, 0.0352, 0.0394, 0.0478,0.0585,0.070s,0.on40,0,0979,0.1125 ,0.1270 ,0.1402 ,0.1499 0.0392 , 0.0275, 0.0407.,0.0555 , 0.0713 ,0.0862 ,0.1066 ,0.17/0 ,0.1195 g o.1727 go.1924

, 0.0047, 0.0223 ,,0.04o0,,0.0578 ,0.0761 ,0.0959 ,0.1181 ,0.1957 ,0.1801 0.2242 0.2746

, 0.0271, 0.0362 ,0.0513 ,0.0682 .0.0665.0.8071 .0.1322 ,0.185 4 ,0.2136 ,0.29ts ,0.4 400 N

, 0.05e7, 0.0639,o.0739,o.0esa ,0. tors .o.8703 .,p.1445 _p.17e9 q.2n3 4:3:5 _ q 4,27 0.1025 ,0.1032 ,0.2057 ,0.1108 0.i192 p.131s J.tS07 J.179: J.224s n.30ss J.468: 1.0000

,0.1777 ,0.1621 0.1452 0.1358 ,0.1336 ,,0.1378 0.1479 J.1656 J.1922 J.2339 jo.2877 A 4252 A.2496.A.194J J.1536 J.1392 ,0.1344 ,0.1363 0.1439 ,0.1561,0.1720 ,0.1874 a.sooo 9,5215 _S.2925 .p.1960 J.1528 0. late ,0.12t8 .0.t183 ,o.ites ,o.1227 ,0.1278 , o.1334 N0.4es) 4 23e5 .p.1658 .,0.1310 0.ss24 .o.10 22 .0.0970,0.oe 50,0.os4 s , o.095s , 0.096e

, 0.1662 ,0,1427 ,0.1172 .0.0993 .0.0877 .0.0003 .0.0 M.9,0.0734 , 0.0722, 0.0718 , 0.0717

, 0.0900, 0.0853 ,0.0777 ,0.0704 ,0.0645 ,0.0602, 0.0572, 0.0552, 0.0540, 0.0534, 0.0531

, 0.0554, 0.0543. 0.0517 ,,0.0488, 0 0480, 0.0437, 0.0420, 0.0407, 0.0399, 0 0303, 0.0390 J

g J364, o 0359dO349,0.0337 0 0323 0;03 3 d.0_303 L O.0298,0,0,29L 0.02a10;02_B5 Figure 6 Phn view showing the two-dimensional distributicn for the LaSalle service water tunnel with 60% flow in one port aml 40% flow in an adjacent port. -

1

. g p. 9-23-96 ; 16:02 ; FAI - NO. SHORE-+2502 31 ' I i

0 a ,J018,,0,00,,46,,,_0.00_46,010th 0.,0043 04044,g0.0043 o.0,013 3 0go43 0 00g, 0.0042 i

k , 0.0066, 0.0066, 0A065, 0.0065, 0.0063, 04062, 0.0061, 0.0060, 0.0059, 0.0

, 0.0007, 0.0090, 0.0095,, 0.0093, 0.0091, 0.0065, 0.0086, 0.0084, 0.0083, 0.0008, 0.0001

, 0.0143 , 0.0141 , 0.0138 , 0 0131 , 0.0130 , 0.0125 , 0.0121 , 0.0117 , 0.0111 , 0.0132 , 0.0111

, 0.0215 , 0.0212 , 0.020 5, 0.0195 , 0.0186 , 0.0177 , 0.0169 , 0.0162 , 0.015 7 , 0.0153 , 0.0151 i

l , 0.0335, 0.0327, OJ0309, 0.0288, 0.0267, 0.0248, 0.0233, 0.0221, 0.0212, 0.0205, 0.0201 l

, 0.0556, 0.0527, 0.0177, 0.0425 , 0 4351 , 0.0314, 0.0387 . 0.0296, 0.0280,0.0000 0.0270, 0.0264

, 0.1047 , 0.0915 ,0.0751 ,,0.0623 , 0.0532 , 0.0466, 0.0419 , 0.0386, 0.0363, 0.0348, 0.0339 l

/0.301B J.1663 .0.1115 .0.0873,0.0710 ,0.0606, 0.0536, 0.0189, 0.0456, 0.0435, 0.0423 O.5000 0.4 509 0,.2353 ,0.1510 .0.llon ,0.00s4,0K45,0.0656,0.0595, 0.0554,, 0.0513 .

0 0528

.4472 0.2303 ,0.1633 , 0.1242 . 0 8011 0.0963, 0.0761, 0.0697, 0.0651, 0.0621 , 0 0605

, 0.2183 ,0.1875 ,0.1521 ,0,1260 . 0.10',4 , 0.0943, 0.0851 , 0.0785, 0.0739, 0.0710 , 0.0693

, 0.1598 , 0.1511

, 0.1361 , 0.1216 , 0.1069 , 0.0990, 0.0914 , 0.0057, 0.0516 , 0.0789, 0.0774

, P.1342 , 0.1307 , 0.1239 ,0.1158 , 0.1000 , 0.1032 , 0.0957, 0.0913 , 0.0684 , 0.0659, 0.0846

, 0.1107 , 0.4101 , 0.114 0 , 0.1806 , 0.8062 , 0.1021 , 0.0966, 0.0057, 0.0935, 0.0920, 0.0

, 0.1100 , 0.1093 , 0.1079 , 0.1061 , 0.1011 , 0.1022 , 0.1006 , 0.0993, 0.0903, 0.0976, 0.09

, 0.1024 , 0.1023 , 0.1022 , 0.1026 , 0.1020 , 0.1020 , 0.1022 , 0.1024 , 0.1027 , 0.1030 , 0.10

, 0.0955, 0 0956, 0.0967, 0.0981, 0.0997, 0.1017 , 0.1037 , 0.1054 ,0.1074 , 0. tops , 0.10

, 0.0982, 0.0091, 0.0910 , 0.0037 , 0.0972, 0.1012 , 0.1053 , 0.1093 , 0.!!28 , 0.115e , 0

, 0.0799, 0.0812 , 0.0543, 0.0056, 0.0943, 0.1006 , 0.1073 , 0.1990 , 0.1201 , 0.1251 , 0.12

, 0.0697, 0.0718 , 0.0763, 0.0628, 0.0910 , DJ002 , 0.1102 , 0.1203 ,0.1301 , 0.1351, 01

, 0.0571, 0.0602, 0.0668, 0.0761 , 0.0874, 0.1002 .0.1843 , 0.1291 , 0.1443 , 0.1582 , 0.

0.0111, 0.0461,0.0561,0 0693,0.0843,0.1080 .0.lles ,0.1410 ,0.1647 0.2104 ,0.1894

, 0.0223, 0.0320,0.0474,0.0647.0.0832 ,0J035 ,0.1270 ,0.1555 o s .1917 0.2381 0.2914

, 0.0055, 0.0260,0.0481,0.0659,0,0062.0.8083 ,,,0.1340 ,,,0.1694 9520J.2f95 Q.3000

, 0.0319 , 0.0422 ,0.0564,0.0759.O.0943 .0.1150 .,,0,1407 .S.1764 ,,,g.2318 JJ311 g32

,0.0712 ,0.0755,0.0s35,0 0937,,0.8060 A1213 #1918 J.1712 ,.g.2369 ,tk?958 0:1582 1.0000  !

,0.1367 ,0.1271 ,0.1180 ,,0.1148 ,0.Il89 ,,0.1238 ,,0.1359 J.151$ J.1622 A.2224 jo.274s

/0.3160 A.2041 J.IS34 .,0.1300 ,,0.8213 .,0.uB6 .0.1233 ,0.1318 ,0.H46 ,0.1604 .0.1754 0.5000

.3L52 43 Q,2999 .A1859 p.1312 ,,0.1149 .0.1077 ,0.1060 ,0.1070 ,0.8121, 0.8873 , 0.1221

.4007,,,0.3025 ,,,0.8420 .0.1132 ,,0.0982 .0.0902 . Q.0961,0.0053 ,0 08:,J, 0.0578 , 0.0003

)

l

, 0.1423 ,0.1225 ,0.1012 .0.0083 ,0.0767 ,0.0700 , 0,0674, 0.0656, 0.0848, 0.0817, 0.0640

, 0.0778, 0.0739 , 0.0675 , 0.0614 , 0.0565, 0.0530 , 0.0507, 0.0491, 0.0483, 0.0478, 0.0476 .

, 0 0984. 0.0973, 0.0451 , 0.0427, 0.0404, 0.0386, 0 0372, 0.0861 , 0.0355, 0.0251, 0 0318 s 0 0318, 0,0214 dA_306 0g963 0.0295 0.0 j .,, 2,76,, 0.0_268,0,0262,0 0258, 0.025, 5, 0.025,3 i Figme 7 Phn view showing the two-dimensional distribution for the LaSalle service water tunnel with 50% flow in one port and

.... 50% flow in an adjacent port.

..e gy.

i TENERA '

September 23,1996 q SFM96-029/SFM96A Dr, Pctros Antonopolous Comed j s

! LaSalle County Station 2601 N. 21st Road Marsellies,1L 61341-9757 j

Dear Petros:

This letter contains the summary ofmy assessment of the strainer issue related to the scalant hdection event. It reflects my myiew of the strainct related sections of Comed's "Probabilistic Risk Assessment Report of the Impact of Foam Sealant Injection in the LaSalle County Nuc Station Servico Water Tunnel."

I have provided information here which I believe supports the statement that the PRA evaluation j

conservatively represents the potential impact of the foam upon the com damage frequency. T potential forriskimpact was small.

The resolution to the strainer issue can be capsulized as follows:

CSCS-ESW Strainer Failure Made Resolution Strainer blockage due to ineffective backwash. ESW surveillance and flow tests indicated i no degradation offlow. The density of I material in the tunnel that could be ingested and impact the strainers would have been highest during this time. Since degradation of flowdid not occur, and no unusual amount of backwash operation occurred, it appears that the strainers were not being unduly stressed with blockage, and the backwash operation was effective. (Note: if excessive backwash fico,uency had been observed, the suryciliance would have been terminated and the plant would have been shut down. This is because this would have invalidated the then-current assumption that the material floated; that assumption coupled with the surveillance test was used as a basis for continued operation.)

One Market Spoor Tour, SuHe 1850. San Francisco, Colsornia 94105-1018. (415) 536-4744, FAX: (

30'd S00*oN OP:11 96.EE d3S 9T2P-9ES-STP:GI *r s'*DNI UB3N31

1 l ,  !

l 1 ar. AweeAnsonsporene ra-H Lesemscasme.asden l psy,2, Strainer backwash lines plugged. See above.

The Comed report indicates a ammfl increase in core damage frequency as a result of the assumption that scalant could impact the strainer operation. ~lhe C=W report concludes that the failure rate is near zero; however, for the purposes ofits +%ns an additional failure rate of 0.001 (i.e., one chance out of one thousand) for strainer failure as a result of blockage. Th low failure rate is based upon interpretations ofthe University oflows studies, which indicato a nominal 10% chance of material becoming entrained during the curing process and therefore being available for ingestion by the ESW suction nozzle. From the Comed report, only 10 the material removed from the tunnel by divers was assumed to be avaliable to plug str this amount (~2.75 gallons) was concluded to be too small to plug the strainers to the poin where the strainer operation would be impacted.

Additional support for concluding that the safety signi6cance of the sealant injection was small prior to cleanup activities commencing can be added by noting that operation of the non-cssen service water pumps acts to " dilute" the concentration of the active materiallin the service water tunnel. Thus, a calculation can be parformed to determine how many tunnei turnovers must occur before the amount of active material left in the tunnel is too low to create the blockage in the strainer tubes required to inhibit design flow (blockage = 90% by volume in th tubes to inhibit design flow). In other words, we can estimate the amount of time the N-ESW pumps must have c,A in order to remove a suHicient amount of active material from the service water tunnel to ,,.m ! 90% blockage of the strainer tubes.

The " dilution" of the concentration of active material in the service water tunnei balance problem involving the computation of the change in mass as a result of the volume of water / foam mixture being swept out of the tunnel by the N ESW pumps. As the ccs%s. tion decreases with time, the amount being swept out is also decreasing. This pattern is repres by an exponential decay equation.

I 9

" Active material" is defined as material which is small in size and near neutrally buoyant. *This i material acts like a tracer (see the IIHR report). From observations and the IIHR report, most

material in the amnel was actually larger and positively buoyant; the tests ladicate that this material would not be pulled down to the B5W suction.

i srussez9wwsruo6A ,

20'd S00*cN OP:IT 96.23 d3S 9T2P-9ES-STP:GI *r S3NI UW3N31 {

Dr. rwrer.~  ;:'u Case #4,sa hMrCeansp 2 eden g ,,,

The following equation is used for the calculation:

l m(t) == em eiM'l Eqn. I where m(t) = concentration of active material in tunnel as a funcdon of time m -initialconcentration V = volume ofservice water tunnel I

Q = volumetric How rate

! t = time Assume the following:

1.- Flow rate is based upon a nominal now of 10,000 gpm through a single non-essential se water pump (ref. - conversation w/ Steve Brown, 8/22/96). Four pumps wem in operation at the time of the event, and therefore a total nominal flow rate of40,000 gpm is M (Note - the flow rate is conservative, in that design flow is 15,000 gpm per pump, with optimal flow in 12,000 to 14,000 spm perpump range).

j I 2. No additional dilution occurs due to ESW operation, i.e., the ESW pumps do not re

! additional foam from the tunnel. ,

Calculation l l l A. Volume, V, ofservice water inanel == 180' x 13' x 7' = 16,380 A3 B. Volumetric flow rate, Q, = 10,000 gpm/ pump x (.002228 (A3/secygpm) x 4 pumps = 89.1 R%ec r

Result #1 l

i At this flow rate, one tunnel turnover occurs approximately every 184 seconds, or about every 3 minutes: 16,380 ft3 / 89.1 A%ec = 183.7 seconds Conclusion The " dilution" of the service water tunnel occurs rapidly due to the high volumetric flow l rate provided by the N-ESW pumps. Foam scalant " particles" that are positively or neutrally buoyant would be swept out quickly by this How.

l

• sne@029.WP/sFM96A PO*d S00*cN TP:TI 96.23 d3S 912P-9ES-SIP:0I r s'*3NI UB3N3.L

. _- ... _ - . - .. ._ _-_ _ --._. . . - - . . - - . =~- - _ . . _ .

l

. i Dr. M .' ' ^;_^ *._

CaseEd, LaSalle CommeJWesise 1 Aqre 4.

C. Next, calculate the amount of material mquimi to fill the strainer tubes to 90% by volume Strainer tubesa are 2.75" la diameter,34" long. TL.J% the volume ofone tube is Vr = ar l = 3.14159 x (2.75/2)2 x 34 = 201.95 in' = .117 ft2 90% by volume = .9 x .117 = .105 ft3 mass of material to 611 this volume = .105 ft' x 59.31 lbs/ft8 = 6.25 lbs (per tube)

D. Total number of tubes (using information supplied by Comed):

Sirmiar E=W ofTi>W f

Unit 1:

i DG 1 cooling water 13 DO 2 cooling water 10 DG 3 cooling water 10 RHR-WS 1 40 RHR-WS 2 40 subtotal iI3 Unit 2:

DO 2 cooling water 10 DO 3 cooling water 10 RHR-WS 1 40 RHR-WS 2 40 subtotal 100 TOTAL 213 Insufficient material to clog all strainers to 90% by volume would exist once the total!

below (213 tubes) x (6.25 lbs/ tube), or 1,331.25 lbs. In other words,1,331.25 lbs of foam are required in the tunnel to clog all tubes to the point where their operation is significa degraded, b.uso g2 i

At any given time,1,331.25 pounds of scalant must have been in the tunnel and in a form susceptible to being pulled into the ESW pumps in order to possibly plug all ESW I

SFM5029.WPtsFMD6A S0*d S00'0N IP:II 96.EE d3S 912P-9ES-SIP:0I 'r s'*3NI 883N31

l l

CamdW,LaSa#e desse Anden i Argei strainers. If the amount ofmaterial was below this amount, the strainem could not be

{ plugged to 90% volume.

i Exanple Calculationt

] As a test of the assumptions in the Comed PRA evaluation, sample calculations were performe j

to determine the susceptibility of the strainers to blockage given the dilution effect.

J he following additional assumptions were employed:

l 1. Service water tunnel is well-mixed so that offluent concentration of active m thmughout. (Note: thus, this assumes all smalant is at least neutrally or slightly positively l buoyant, and that none adheres to the floor surface.)

i

11. Initial concentration ofmaterialis based upon a mass of30 cubic feet offoam. This is based upon discussions with Steve Brown (Comed, LaSalle; 8/1996 and 8/23/96), and represents an

{ upper bound for the amount of material removed fiern the tunnel by divers. De amount i removed loosely filled five 55-gallon drums (275 gallons total, as used in the Comed PRA t

evaluation). The amount of material actually in the tunnel at any given time cannot be estimatad i

with wi.iiity, since the foam was irdected over different time periods and dilution was or could i

have been occurring throughout the time ofconcern. Tests gh.wd on material from two of the drums at the IIHR facility indicate that much of the material was mlatively largo (>10" 3

positively buoyant; test results show that this material would not be pulled down to the ESW i

suction. Thus, the actual amount of active material that had the potential to be pulled down into the ESW suction is believed to be much less than the 30 cubic feet used in Therefore, using 30 cubic feet as a starting point is conservative.

m. The initial concentration of active materialincludes any material that would have been dislodged from the floor after initially adhering to the floor. In other words, no additional

material is added to the mix from that stuck to the floor. This is supported by the divers' observations and experience regarding the difficulty in removing the adhsred material from the

! floor.

i j

iv. Using data supplied in the IIHR report, the density of the foam is nominally chosen to be 3

{

0.95 gm/cm (which is 59.31 lbs/ft2, using the conversion factor of 62.428 to convert to lbs/ft'

{ from sm/cm')

i i

v. For the baseline calculation it is assumed that flow through the ESW related strainers is

equally distributed among all 9 strainers, so that there is an equal likelihood of any speci i

strainer receiving foam material. In actuality, the observed accumulation ofmaterial was biased i

i sFM4029 WWsFM96A i

1 4

I 90* d S00* cN Etr: T T 96.EE d3S 9T2P-9ES-Sip:0I

• 3* S'

• 3NI tRl3N31

a Dr. Pstnw An': :;:

Casust, LaSsNe Commt.hadism Aqye 6.

towards the Unit 2 side of the tunnel (the northern side of the tunnel), where the injectio occurred. Therefore, a senaltivity analysis is included here usingjust Unit 2 strainers.

v1. For the baselino calculation which rollows, all 275 gallons (30 cubic feet) are assum available for ingestion by the ESW suction (as W_ to the 2.75 gallons used in the Comed PRA evaluation baseline). This assumption represents the situation covered b analysis included in the Comed report, in which the failum probability of the strainers is increased by a factor of10.

Calculation 3

I. Initial mass offoam, m ,- (.95 gm/cm x 62.428 (lbsJA'y(gm/cm 8

)) x 30 ft' = 1,779.2 lbs.

The total number ofstrainer tubes that could be filled to 90% by volume is themfom:

1,779.2 lbs/6.25 lbs/ tube = 285 tubos Thirty cubic feet of foam is thus enough mass to clog all strainers to 90% by volume.

II. Concentration offoam in tunnel = 1,779.2 lbs/16,380 ft2 = .11 lbs/A)

The first second ofpump operation removes (89.12 A' x .11 lbs/A8) ofmaterial, which is about 9.8 lbs. Every subsequent second removes less, as the concentration in the tunnel is raiM (diluted).

With these assumptions and calculations, a total of(1,779.2 - 1,331.25), or 447.95 pou foam must be removed through the non-essential service water pump system to drop of foam remaining in the tunnel to below the required amount for blockage.

III. We can now solve Eqn. I for t, the amount of time rcquired to reduce the mass in the t to 1,331.25 lbs by setting m(t) to 1,331.25.

1,331.25 = 1,779.2 exp [(-89.12 A5/secy(16,380 A2) x t]

Solving for1:

.748 = exp ( .0054t)

In (.748) = .0054t t = In(.748y( .0054) = ( .29005y( .0054) = 53.31 W = < 1 minute sFM96-029.WP/SPM96A 20'd S00'ON EP:11 96,EE d3S 912P-9ES-SIP:0I 'r S'*3NI UB3N31

Dr. neur: :::L CemeEd, Lasella Connqy.nnefow l hre7.

{

l This result means that the concentration c fmaterial in the service water tunnel; lasufficient to plug all strainer tubes to 9C % by volume after less than I minute of operat l i

! four N-ESW pumps at the nominal flow rtte assumed. The time window ofvulnerability strainer plugging is only 1 minute (less than 1/3 of a tunnel tumover). Thus, it is extrem unlikely that the strainers would have plugged during any emergency operation required of ESW system.

SenshMtyAnabels The above calculation is repeated assuming that only the Unit 2 strainers neceive mate that all foam flows through the Unit 2 strainers. Thus, the number of tubes susceptible to plugging drops to 100 (see Step D above), and the volume required for 90% plugging of thj 100 tubes dmps to 625 lbs.

i Substituting 625 lbs. for 1,331.25 lbs. In the calculations, we get: i i

625 = 1,779.2 exp [(-89.12/16,380) x t]

Solving for t:

.351 - exp ( .0054 t) i 1

i t-In(.351)/ .0054 l t = -1.047 / .0054 = 193.9 seconds, or appmximately 3.23 minutes.

t Even in this situation, the time period is very short, and the potential for a transient event occurring during this particular time period is insignificantly small. Thus, it appears that there was very little potential for strainer plugging and loss of ESW operation.

suit #3

'Ihe amount of time required for N-ESW pump operation to dilute the concentration of material in the tunnel to below the point ofstrainer vulnerability is loss than 3.5 minutes even in the extreme case of(l) only Unit 2 strainers must be plugged and (2) all 30 cubic feet of foam could be ingested by the ESW pumps. If either of these conditions is relaxed l

(for example, if entralament is limited to 10%, u used in the Comed report), the time window ofvulacrability decreases dramatically. A significantly higher amount of foam (much greater than the 30 cubic feet assumed for the calculations) would have been

! required in the service water tunnel before the time window of vulnerability became

{ signincant (e.g., a window greater than 10 minutes would have required over 500 cubic feet of foam naalant) l Ammo 29.wr/srwu l

80*d S00*DN EP:II 96.EE d3S 9T2P-9ES-SIP:GI *r S'*DNI UB3N31

l TENE,R,R INC.,S.F. ID:415-536-4716 SEP 23'96 14:56 No.007 P.02 l

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Csongd,Lafe#e Cong Amisa

! )

! Conclusion

' A strainer failure rate close to zero seems appropriate for use in any calculation which is performed to estimate the potential increase in core damage probability as a result of i ycsse of foam sealant in the service water tunnel. The use of a failure rate of 0.001, as j in the Comed PRA evaluation, appears to be conservative a rate closer to zero would bc j more reasonable; a rate of 0.01 (a factor of 10 higher - which would cormspond to the i

4 I

example calculation performed above) is even more conservative given the conservative nature of the assumptions employed (e.g., inkially high -x+=-.a;on of foam; all foam

! available to be pulled in by ESW pumps).

l l AdditionalIssues

1. Reliability of bidw.rai system - the material condition of the backwash equipment was

' reviewed by Comed, and the condition of the equipment is satisfactory.

i

2. Backwash activity - no unusual amount of backwash activity occurring during the l surveillance operation was noted, providing a data point indicating that material was not being l

drawn into the strainers. (Normal surveillance does not continuously monitor strainer i

i performance - only one data point is taken in the initial surveillance, and it did not indi

problem. When the flow tests were performed later, when the pwece of the foam was the strainen were monitored - once again, no problem was indicated.)

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3. Manual backwash onpability - credit can be taken for manual backwash as a backup since (1)

It can be demonstrated that the procedures are well understood, and (2) the staffis tmined os l '

l them. Based upon conversations with Comed staff (8/23/96), manual backwash can be l

accomplished in less than I hour (in fact, it can be performed in appt=Imdaly 10 minutes).

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addition, operation of ESW is not impeded during this procedure. Afere, in the event of failure of the automatic system it would be possible for manual action to be s'-=%I in a short i

j period of time. Due to the slow pace at which accumulation of material within the s would oocur (extrapolating from the calculations presented above), h is concluded that adequa l time exists for manual operation well in advance of any significant impact on flow through the I

i ESW system.  !

l Overall Conclusions l I believe that the possibility of strainer tube plugging was very small during the time periodl conccrn. In addition, although I haven not estimated a value, I believe that the likelihood of l j

i transient event requiring ESW operation combined with the subsequent degradation of ESW l

]

operation as a result of sealant material in the strainers was an extremely small pro '

1 I sme6429,wersno6A j

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TENERA INCo,S.F. ID:415-536-4716 SEP 23'96 14:57 No.007 P.03 l

g. -

Dr. ?wrer Antonepeleen nage 9.

ConsM,LaSelle ConnyStetten base this conclusion on the results of the Iowa studies, the observations made by the plant staff during subsequent survcillance activities, and the calculations provided here.

The strainer-related conclusions reached by the Comed PRA report appear to be reasonable and i conservative. 'lhe changes in core damage pmbability (CDP) estimated in the PRA report aro l consistent with the conclusions I draw from the calculations performod above. 'Ihe PRA basis using " input probabilities x 10" (Table 1 of that report) calculates a change in CDP of only 1.7E-5, which isjust above the guideline for "potentially risk significant"(Table 2 of the report).

Given the conservatisms in the calculation, the high degree of dilution, and the fact that no significant strainer blockage was or has been observed, I believe the actual change in CDP was much smaller (i.e., near zero), and existed for only a very short time, i

Sinceral Was B Id Senior Consultant TENERA. Inc.

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