ML20024G809

Summary Technical Rept to Us AEC Directorate of Licensing on Secondary Containment Leak Rate Test,Jul 1973.

ML20024G809
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Site:	Monticello
Issue date:	07/31/1973
From:	NORTHERN STATES POWER CO.
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NUDOCS 9104300435
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NORTHERN STATES POWER CmPANY MONTICELLO NUCLFAR CENERATING PLANT s

s SLMiARY TECHNICAL REPORT TO UNITED STATES AT WIC ENERGY COMMISSION DIRECT 0PATE OF LICENSING ON SECONDARY CONTAINMENT LEAK RATE TEST JULY, 1973 l

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"0NTICELLO NUCLEAR GENERATING PLANT

SUMMARY

TECHNICAL REPORT ON SECONDARY CONTAINMENT LEAK RATE TEST

1.0 INTRODUCTION

Technical Specification 4.7.C.1.b for the Monticello Nuclear Generating Plant requires, with regards to the secondary containment capability test, that " Additional tests shall be performed during the first opera-ting cycle under an adequate number of different environmental wind conditions to enable valid extrapolation of the test results." In compliance with this requirement, eight Secondary Containment Capebil-ity Tests were performed during the first operating cycle.

This sux:nnary technical report is submitted in accordance with the requirements of Section 6.7.C of the Technical Specificatioun, which requires that "Each integrated leak rate test of the accondary con-tainment shall be the subject of a summary technical report. This report should include data c,n the wind speed, vind direction, cutside and inside temperatures during the test, concurrent reactor building pressure, and emergency ventilation flow rate. The repurt shall also include analyses and interpretations of these data which demonstrate compliance with the specified leak rate limits."

2. ')

SUMMARY

OF RESULTS Two sets of capability tests were conducted on eight separate occasions wherein the "A" Standby Gas Treatment System (SBC S' train was operated at varying system flow conditions with either the .er or inner rail-way door open. On each occasion, an additional st. of cests was con-ducted using the "B" SBGrS train with the outer railwey door open. A total of 68 separate data sets are reported, each representing one test.

The tests were conducted under varying wind and atmospheric conditions and provide an adequate basis for a valid extrapola'; ion to calm conditions. The analysis will, of course, be updated to take advantage of improved statistics as data is collected from future tests. In all cases, it was found that on extrapolation to calm conditions, a 0.25 inch H2O negative differential press"re could be maintained for a SBCIS flow under 4000 scfm.

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3.0 GENERAL TEST METit0DS The Secondary Containment Capability Tests were accomplished by AUTO INITIATION of a respective SBGTS exhaust train and operator verification

thst the normal reaccor building intaka and exhaust air handling units

! had shut down as well as verification that the reactor building isola-

! tion dampers closed. The tests were conducted with at least one of the double airlock doors on each secess to the secondary containment closed and with one of the reactor building railway doors alternately open.

Af ter building pressures had stabilized, differential pressures were measured botveen inside and outside of the building using an inclined tube water manometer located on the south building wall at 935' grade level eleve. tion.

The SBGTS flowmeter was calibrated upon installation by measurir.g the differentirl pressure across the orifice with an inclined water tube manometer and calibrating against a pitot tube traverse of che piping.

The flow transmitters have been subsequently calibrated and matched l to the initial flow calibration curve. The pitot tube traverse pro-

[ cedures were obtained from the American Society of lleating, Refrigera-tion and Air Coni'tioning Engineers llandbook. Textoook accuracies for the fleu crifice are i \% to 2% of fall scale, and i %% to i 5% for the pitot tube. The accuracy of the flow measurement is believed to be 1 5% or better. The measurements .:t grade level with no correction applied are consistent with the method of testing discussed in the Monticello FSAR (page 5 3.4).

4.0 TEST RESULTS

The test results are summarized in Tables 4.1, 4.2, and 4.3 which list j results for the "A" train with the outer railway door open, the "A" train with the inner railway door open, and the "B" train with the outer railway door open, respectively. Tha vacuum at grade. level is not corrected for stack effect. Tentative conclusions that can be drawn from these tests are that the "A" and "B" SBUIS trains are nearly equal in performance and that in-Icakage is greater through ,

the outer railway door.

5.0 ANALYSIS OF TEST RESITLTS There are four principal parameters which must be accounted for in the secondary centainment leakage test in order to accurately determine the capability of the SBGTS to draw the required vacuum. These are SBGTS flow rate (Q), inside and outside air temperatures (Ti and To, respectively), sind velocity (v) and wind direction. Under calm con-ditions with inside and outside air temperatures equal, the SBGTS flow rate will equal building in-leakage at some differential pressure, 21 Pg.

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Since pressure variations are quite stnall relative to ambient pressure, SBcrS flow rate can be related to d Pg through Bernoulli's equation for incompressible flow. This relation is of the forrn Q = C A Pgb where C is a co'tstant 2 2 or 6 Pg = KQ l where K1= 1/C The flow through buildings without mechanical aids is referred to as

" stack effect." Stack effect is dependent on differences between the inside and outside air temperatures and the height of building openings d ere leakage can occur. n eoretical stack effect is given by:

b d P, = 0.52 IIP, 1 1 To Ti (Eq 9-16, Perry's Chemical Engineer's llandbook, Fourth Edition, p 9-43) is referred to as stack draf t in inches !! 0,11 is the height Where of the stac OP, k, P is ambient pressure, and To 2 and 71 are outside and in- [

side air temperatures, respectively. To apply this equation to building leakage,11 is regarded as a weighted average height of building openings, and the constant term must be reevaluated to account for the relative size of the openings. Since P is nearly constant, etack effect for this analysis is reduced to: ,

d Ps =

K24 1. 1 >

To Ti Infiltration effects as a result of wind pressure were qualitatively evaluated for different vind directions. The data collected during testing show that the capability to pull vacuum is reduced for south.

erly vinds. This signifier that in-leakage is greator for southerly vinds. It is postulated that the principal leakage path into the building is via the railway d> rs located on the south face. In addi-tion, it is recognized that most of the building north face is screened from direct vind impingement by the turbine building. At vind speeds above 0 mph, external velocity pressure can be either negative or posi-tive with respect to its effect on the external building surfaces. On surfaces where vind impinges, the velocity pressure is positive, so total pressure is greater than the static pressure; on surfaces where vind does not impinge but sweeps by, the velocity pressure is negative so total pressure is less than static pressure. W e higher in-leakaga associated with southerly winds results in a higher measured (less negative) differential pressure. Exfiltration through the side valls is not sufficient to offset the in-leakage without an adjustment of 3-

building pressure. If the wind was from the north, three walls could .

have exfiltration and only the largely unexposed north wall would have infiltration. Building internal pressure would have to decrease to allow enough infiltration to offset the stack release and the three vall exfiltration. It is apparent from the test data that wind preo-sure effects lead to lower measured differential pressure as wind vel-ocity increases regardless of direction.

Velocity p64ssure has been determined to be nearly proportional to gv2, where g is the air density at To and v is the wind velocity. This effect on measured differential pressure (AP) is given by:

= 2 where K3 is dependent on wind direction.

o Pw K3gv Thus, measured differential pressure is the sum of the three components discussed above, i.e.

6P = 6Pg + A Ps + b Pw Multiple linear regression was used to find coefficients of the above equation in the following fom:

AP =

KlQ2+K 24 1 *1 ++K3 V To Ti The data from Table 4.1 was split into two sets representing northerly and southerly winds. Data from " Secondary Containment Leak Rate Test, August 1970" van included in the set used to calculate coefficients for northerly winds.

Regression analysis detemines the relative effect of each of the inde-pendent variables on the measured differential pressure. The method and the resulting equation are empirical and apply only to the data set used.

If sufficient data are available, and the model is reasonable, a rather sophisticated prediction capability will evolve. Extrapolations based on regression analysis can be valid for limited ranges outside of the data set if the relative influence is reasonably well hown.

For northerly winds, with the outer railway door open, it was found that: ,

6P =

0.0206xv-62+0.43x10f1 9 4 1 , + 0.0023 v 2 To Ti where: Q =

SBGTS flow (cfm) v = wind speed (ft/sec)

T = temperature (OR) p = density (1b/ft )

_ _ _ _ _ _ _ . _ i

For calm conditions, as defined in the Technical Specifications (v 5; 5 mph), the SBGTS flow rate required to maintain a 0.25 inch H2 O vacuum is approximately 3400 scfm. The average absolute per-cent deviation for predicted versus actual results was 5.5%. The maximum was 12%.

A similar analysis was conducted for southerly winds. However, less data was available and au can be seen on Table 4.1, southerly wind data was generally less stabic and thus statistically more suspect.

Theoretically the first two terms of the above equation should be independent of wind direction and thus equal for both equations.

Since the statistics for northerly wind data are much better, it is tentatively proposed to test results of tests during southerly wind conditions with K3 = 0.0014 and other terms the same until more data is collected. The abeve value of K3 was derived in ttie analysis of sourtherly winds. Figure 5.1 demonstrates the relative ef fect of wind velocity for northerly and southerly winds.

As noted in Section 2.0, slightly higher leakage was seen with the inner railway doors open. Based on the above results, there is suf-ficient margin above 3400 scfm to insure that the 0.25 inch H2O can be maintained under calm conditions even with the inner doors open; however, it should be recognized that the inner doors are normally kept closed.

6.0 CONCLUSION

S Da the basis of the information presented above, it can be concluded that the reactor building demonstrates adequate leak tightness under all environmental wind conditions and that a sufficient base of data has been developed to allow a valid extrapolation to calm conditions. However, model improvements should be anticipated as more data is collected. The above analysis is sufficient?' reli-able to evaluate the acceptability of future test results .'hich will be submitted in six centh reports.

IABLE 4.1 SECONMRY CONTAINMENT CAPABILITY TEST RESULTS Train "A" With Outer Railway Door Open Inside Outside Wind Wind SCTS Flow P Air Temp Air Temp Speed Direction (efn) (in H)0) ( F) ( F) .(eph) 3500 .29 .45 78 81 14-24 SW 3700 .40 .45 78 81 14-24 SW 3920 .42 .47 78 81 14-24 SW 3500 .45 70 -4.7 15 NNW 3300 .435 70 -4.7 13 NNW 3000 40 70 -4.8 13 NNW 3000 .33 72 37.2 8 E 2500 .28 72 37.2 8 E 3500 .36 70 50 12 E 3300 .32 70 50 10 E 3000 .31 70 50 15 E 3500 .30 73 47 10 NNW 33e0 .29 73 47 9 NNW 3000 .27 73 47 9 NNW 3500 .31 74 42 14 S 3300 .29 74 42 16 S 3000 .26 74 42 20 S 3500 34 71 56 13 N 3300 .32 71 56 13 N 3000 .31 71 56 16 N 3500 .37 76 55 2-4 NNW 3300 .35 76 55 18 N 3000 .31 76 55 12 NNW

TABLE 4.2 SECam8RY CQiTAINMENT CAPABILITY TEST RESULTS Train "B" With Nter Railway Door Open Inside Outside Wind Wind SGTS Flow P Air Temp Air Temp Speed Direction j (cfm) (in H90) ( F) ( F) itthl __

l 3500 .37 .44 78 81 8-26 SW 3700 .37 .45 78 81 8-26 SW 3950 .25 .45 78 81 8-32 SW 3500 .46 71 -4.6 15 NNW 3300 .41 70 -4.7 15 NNW 3000 .38 70 -4.7 15 NNW 3000 .32 72 37, 8 E 2500 .28 72 37 7 E 3500 .36 70 50 14 E 3300 .35 70 50 10 E 3000 .32 70 50 14 E 3500 .31 73 48 8 NNW 3300 .29 73 48 8 NNW 3000 .26 73 47 10 NNW 3500 .30 74 42 21 S 3300 . 2 9, 74 42 20 S 3000 .28 74 42 20 S 3500 .34 71 56 15 N 3300 .33 71 56 14 N 3000 .29 71 56 18 N f

3500 .38 76 55 14 NW 3300 .37 76 35 14 NW 3000 .33 76 55 10 NW

TAB LE 4. 3 SCCONDARY CONTAINM121T CAPABILITY TEST RESULTS Train "A" With Inner Rativay Door Open Inside Outside Wind Wind SGTS Plow P Air Temp Air Temp Speed Direction (cfm) (in H2O) ( F) ( F) (meh) 3500 .24 .29 78 81 8-26 SW 3700 .26 .33 78 81 8-26 SW 3940 .39 .49 78 81 8-26 SW 3500 .36 68 -4.9 18 NNW 3300 .34 69 -4.9 15 NNW 3000 .32 69 -4.9 15 NNW 3000 .30 72 37 8 E 2500 .25 72 37 8 E 3500 .32 70 50 6 E 3300 .28 70 50 8 E 3000 .26 70 50 10 E 3500 .29 73 47 8 NNW 3300 .28 73 47 7 NNW 3000 .23 73 47 9 NNW 3500 .26 74 42 18 S 3300 .25 74 42 22 S 3000 .22 74 42 16 S 3500 .30 71 56 22 N 3300 .27 71 56 18 N 3000 .27 71 56 18 N W.

TAB 12 4.3 SECONDAPY CONTAINMDiT CAPABILITY TEST RESULTS Train "A" With Inner Railway Door Open Inside Outside Wind Wind SGTS Flow P Air Temp Air Temp Speed Direction (cfm) (in H?O) ( F) ( F) (mph) 3500 .24 .29 78 81 8-26 SW 3700 .26 .33 78 81 8-26 SW 3940 .39 .49 78 61 8-26 SW 3500 .36 68 -4.9 18 NNW 3300 .34 69 -4.9 15 NNW 3000 .32 69 -4.9 15 NNW s 3000 .30 72 37 8 E 2500 .25 72 37 8 E 3500 .32 70 50 8 E 3300 .28 70 50 8 E 3000 .26 70 50 10 E 3500 .29 73 47 8 NNW 3300 .28 73 47 7 NNW 3000 .23 73 47 9 NNW 3500 .26 74 42 18 S 3300 .25 74 42 22 s 3000 .22 74 42 16 S 3500 .30 71 56 22 N 3300 .27 71 56 IP N 3000 .27 71 56 18 N

FIGURE 5.1 MONTICELLO NUCLEAR GENERATING PIANT REACTOR BUILDING PRES $URE AS A FUNCTION OF WIND SPEF.D FOR CONSTANT SBGTS TLOW RATE o

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