ML20082D883

Suppression Pool Local-to-Bulk Temp Difference,Shoreham Nuclear Power Station - Unit 1

ML20082D883
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Site:	Shoreham File:Long Island Lighting Company icon.png
Issue date:	08/30/1983
From:	STONE & WEBSTER ENGINEERING CORP.
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ML20082D881	List: ML20082D878 ML20082D883
References
NUDOCS 8311230115
Download: ML20082D883 (27)

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T SUPPRESSION POOL LOCAL-TO-BULK TEMPERATURE DIFFERENCE SHOREHAM NUCLEAR POWER STATION - UNIT 1 4-LONG ISLAND LIGHTING COMPANY

,_ AUGUST 1983 i

i Stone & Webster Engineering Corporation Boston, Massachusetts 02107 8311230115 831117 PDR ADOCK 05000322 A PDR

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SECTION 1

. INTRODUCTION NRC has established acceptance criteria for BWR suppression pool temperature limits in order to resolve the . issue of vibratory loads on containment

-structure as a result of extended steam blowdown into the suppression pool.

^

. The limits are discussed in NUREG-0783 (Reference 1) which si,ecifies a 10*F

- local-to-bulk pool . temperature difference. This ' local-to-bulk pool

' temperature difference is applied to Shoreham as . specified in the pro-prietary. supplement Appendix-I, to SNPS Design Assessment Report (DAR),

Revision 5, December 16,1981' (SNRC-645)- (Reference 2) .

The report presented here concludes that the assumption is conservative based on analysis of LaSalle's inplant test data (Reference 3), and the results of the subscale ~ pool testing performed at MIT (Reference 4).

Application of LaSalle inplant SRV blowdown test data to Shoreham has been justified..in Reference 4 and approved by the Commission in Supplement I to Shoreham's Safety Evaluation Report.

~

The following three ~ sections discuss the methodology used e justify the local-to-bulk pool' temperature difference. In Section 3, the MIT subscale model is examined for consistency with the inplant tests. In Section 4, the results from the MIT subscale test are analyzed to justify the accept-ability of the Shoreham local-to-bulk temperature difference in meeting the

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criteria as specified by NRC.

B9-11600.02-162-D- 1-1 t

SECTION 2 SRV ACTUATIONS 2.1 LASALLE LOCAL-TO-BULK TEMPERATURE DIFFERENCE LaSa11e's inplant SRV test program was performed in accordance with a test procedore reviewed by the NRC (Reference 3). The. test program consisted of different types of SRV actuations from which only the data obtained from the extended valve blowdown have been analyzed here for determination of local-to-bulk pool temperature difference. The extended valve blowdown test was performed five times to assure consistency and allow assessment of repeatability. Five sets of data were obtained from these tests and the results are presented in Section 2.3 LaSalle nuclear power station has a BWR Mark II type containment and uses T-quenchers in the suppression pool. During the test, tape readings were taken from 48 temperature sensors of which 34 were directly located in the suppression pool (Figures 3 and 4) . These sensors have an accuracy of

+

_0.5 F and a response time of 5 milliseconds (Reference 3).

2.2 LOCAL POOL TEMPERATURE

. NUREG-0783, Section 4.3 (Reference 1) states that, based on the data from

! Monticello SRV tests, "It is apparent that the temperature which controls the condensation process (that is, the " local" temperature) is best characterized by that which would occur at a point directly above and below the quencher arms (perhaps one or two arm diameters distant), with the former providing a more conservative measure of this parameter."

i BD1-1160002-797 2-1

LaSa11e's quencher configuration is shown in Section A-A of Figure 1. The "outside" quencher "C" (Figure 2) was used for the extended SRV actuation test without using the RHR for suppression pool cooling.

The " local" ' temperature readings were taken from sensor TT-33 which was locat ed directly above and about 2.3 arm diameters away from the quencher arms . Figure 5 is a typical plot obtained from sensor TT-33 for one of the inplant extended blowdown tests. In all five tests the valve is full open after 10.1 seconds. The first few seconds of ana points can be discarded as erroneous due to system stabilization and SRV line air clearance. As can be seen from Figure 5, some temperature spikes were observed . during the blowdown. This is due to high sensitivity of the temperature sensors a response time of 5 milliseconds, and consequently, their detection of small addy currents caused by not fully condensed steam bubbles. The " local temperatures" on Figures 6 thrcugh 10 were produced from the best estimate line drawn through the recorded temperature profiles (similar to Figure 5) and ignoring the first few seconds of the data immediately after the valve opens.

2.3 BULK TEMPERATURE The bulk temperature was calculated on the basis of mass and energy released from the reactor through the SRV, assuming that the suppression pool acts as a uniform heat. sink. This calculation is in accordance with the NUREG-0783, Section 5.4 (Reference 1) and the bulk temperature is shown on Figures 6 through 10.

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2.4 LOCAL-TO-BULK TEMPERATURE DIFFERENCE The local-to-bulk temperature difference was calculated based on Figures 6 through 10. For each test, the maximum temperature difference between the local and calculated bulk temperature curves was determined for the entire blowdown . period. The maximum AT's for the five tests were found to be:

8, 8, 7, 7, and 10 F, corresponding to Figures 6 through 10, respectively.

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SECTION 3 MIT SUBSCALE MODEL TESTS

3.1 BACKGROUND

Stone & Webster Engineering Corporation (SWEC) sponsored a study at MIT (Reference 4) to betcar understand the physical processes underlying pool mixing and circulation and to help extrapolate inplant temperature measure-ments from LaSalle to Shoreham. The study addressed the temperature distribution induced within a suppression pool by a steam discharge. The problem was first examined theoretically to identify the dominant zones and to estimate circulation and cixing occurring within each zone. The circulation and mixing estimates were based on earlier subscale tests performed at MIT using hot water in place of steam. This analysis was then used to justify a 1/17 Froude scale model employing an actual steam source.

3.1.1 Focus of Study The focus of the study was on the rises in the local temperature aear, but not within, the condensing steam plume. A total of 16 tests were performed in accordance with two primary objectives: (1) to test the general feasibility of subscale tests and (2) to study the influence, on pool temperature distribution, cf several parameters that distinguish Shoreham and LaSalle pool geometriec and quencher orientations.

BDI-1160002-797a 3-1

3.1.2 Modeling Local and Bulk Temperatures Theoretically,. in order to properly model local and bulk temperatures, the following scaling ' requirements were recognized: geometric similarity, kinematic (time) similarity, and dynamic similarity. The MIT study concluded that the most important dynamic factors were quencher momentum and buoyancy; hence, dynamic similarity could be obtained by using similar values of discharge densimetric Froude number (which expressed the ratio of momentum flux to buoyant force) in model and prototype. Therefore, the MIT model was scaled according to correct geometric, kinstmatic, and Froude similarity. Other dynamic parameters and properties which could not be scaled precisely included Reynolds number, Mach number, surface heat loss parameter, and certain flow details (e.g., the number of uancher s pe.rts and the detailed array of downcomers and support columns within the pool).. For the most part, these parameters and properties were judged to be insignificant or conservatively represented in the molel. However, as part of the first objective (to test general feasibility of subscale tests), a number of initial tests explored experimental repeatability and sensitivity to geometric details.

3.1.3 Conclusions i

Conclusions regarding the first objective are:

1. Subscale model test results were highly repeatable.

I BD1-1160002-797a 3-2

2. Results showed little sensitivity to the number of quencher ports (in the range N=9 to 35) suggesting that the sensitivity tests performed with N=35 were representative of the prototype.

3. Results were slighly sensitive to the nature of flow resistance offered by downcomers and support columns. Consequently, sensitivity tests were performed using a representative number and size of such obstacles in the far field. However, because the tests were not performed to model any particular quencher, obstacles were not included in the near field (the approximately 45-degree sectors of the pool on either side of the quencher).

3.2 COMPARISON OF MIT SUBSCALE TEST AND LASALLE INPLANT TEST RESULTS Conclusions regarding the second objective are:

3.2.1 Model Basin and Thermistor Probe Readings The schematics of the MIT model basin and thermistor probe locations are shown on Figure 11. Microcomputer scans of.the thermistor probe readings l from the experiment that was set up to represent the "outside" quencher "C" (see Figure 1) at LaSalle are shown on Figures 12 and 13 (Reference 4).

Temperature readings under Columns A, through H on Figure 12 correspond to respective horizontal probe locations shown on Figure 11 at two different i times. Within each column, up to five temperatures were recorded at various vertical elevations, with the top reading representing the elevation closest to the surface and the bottom reading representing the l

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BD1-1160002-797a 3-3 L

elevation closest to the bottom as shown in Figure 11. The circled axial probe readings of Figure 12 have been plotted on Figure 13 for the steam flow duration. The time constant of the thermistor probes was 1 second and the accuracy of the thermistor readings was estimated to be +0.1 #C. The experiments appeared highly repeatable,'with temperature ranges varying, at most, by about 0.5 C between repeated experiments.

It should be noced that the primary purpose of the MIT experiments was not to compute a local-to-bulk temperature rise for each experiment. The differences in pool geometry and quencher orientation were explored by comparing a range of temperatures with the assumption that variation in bulk-to-local temperature difference would be directly proportional to variation in the temperature range.

3.2.2 Data Comparisons The MIT subscale data, Figure 13, have been superimposed on the LaSalle inplant data, Figures 6 through 10, for comparison. It should be noted i that the prototype time scale was used along with temperature conversions from degrees . Celsius to degrees Fahrenheit. Only the data obtained from the thermistor probe A4 (the bottom probe in column A; see Figure 11) have been shown to compare with the similar LaSalle sensor TT-33.

A bulk temperature for MIT model basin was calculated based on thermal

- energy balance for the duration of the steam blowdown and is shown on Figures 6 through 10.

BD1-1160002-797a 3-4 4 -

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As can be seen from Figures 6 through 10, the trends predicted by MIT subscale model for LaSalle configuration are consistent with the data obtained from the LaSalle inp?. ant test. Even though MIT subscale model did not attempt to preserve the same geometric relationship between the orobe and quencher as any of the LaSa11e's plant-specific temperature sensor locations, the consistency between the trends shown by the two sets of data for local ' temperatures is very good. The generally smaller difference between local and bulk temperatures observed in the subscale model is due in part to the absence of flow obstacles in the near field of the model.

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SECTION 4 APPLICATION OF MIT SENSITIVITY STUDIES TO DETERMINE SHOREHAM LOCAL-TO-BULK TEMPERATURE DIFFERENCE 4.1 UNIT SIMILARITES AND DIFFERENCES While Shoreham and LaSalle units are similar (both GE Mark II BWRs), the pool geometries (especially operating water depths) and quencher orienta-

'tions - are different. These differences are illustrated on Figure 1. The second objective of the subscale tests performed at MIT (see Section 3.1) was to explore the sensitivity of pool temperature distribution to the variables- of water depth and quencher location and orientation corresponding to the two plants.

4.2 CONCLUSION

S Conclusions relating to the second objective are: "The LaSalle County suppression pool is characterized by a greater initial water depth and a i different quencher location . and orientation than - Shoreham. Experiments show that the spatial range of induced temperatures decreases with larger water depth but increases with the LaSalle quencher location and orienta-tion. Experiments corresponding to a LaSalle "inside" quencher (located

-near the reactor pedestal; see Figure 1) showed a spatial range of temperatures approximately twice that of the Shoreham quencher.

Experiments corresponding to a LaSalle "outside" quencher (located near the reactor containment wall; see Figure 1) showed a spatial range of temperatures approximately 15 to 30 percent above that for the Shoreham quencher."

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Thus, it is apparent from the MIT. model tests that Shoreham's bulk and

-local temperatures follow each other much more closely (i.e., show less deviatica about the mean) than they do in LaSa11e's. In other words, Shorcham's local-to-bulk temperature difference is at least 15 to 30 percent _ smaller than LaSa11e's.

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SECTION 5 CONCLUSIONS The data obtained from LaSalle's inplanc extended SRV tests were evaluated and maximum local-to-bulk temperature differences of 8, 8, 7, 7, and 10 F were obtained for the five tests performed.

Subscale tests were conducted at MIT for sensitivity studies for LaSalle and Shoreham plant-specific pool geometries and quencher location and orientations. Experiments showed spatial temperature ranges are at least 15 percent smaller for Shoreham than the LaSalle configuration.

In order to evaluate a conservative local-to-bulk temperature difference for Shoreham, the highest of the maximum ATs obtained from LaSalle inplant tests, or 10 F, is assumed. Based on MIT subscale tests, Shoreham's suppression pool local-to-bulk temperature difference is at least

! 15 percent lower or conservatively 8.5 F.

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l Therefore, it is concluded that the preliminary local-to-bulk temperature difference of 10 F reported in " proprietary supplement" Appendix I, to i

j Shoreham Design Analysis Report (DAR), (Referance 2) can be justified as a very conservative valua.

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REERENCES

1. Suppression Pool Temperature Limits for BWR Containments, U.S. Nuclear Regulatory Commission, NUREG-0783, November 1981.

2. Shoreham Design Assessment Report (DAR), Appendix I, Revision 5, December 16, 1981 (SNRC-645).

3. LaSalle Inplant SRV Test Procedure and Data Set.

4. Adams, E. E. and Baker, R. Subscale Steam Tests of Vapor Suppression Pool Mixing and Circulation with Application to the Shoreham Nuclear Power Station. Technical Report of the R. M. Parson's Laboratory for Water Resources and Hydrodynamics, Report No. 273, Massachusetts Institute of Technology, December 1981.

B9-11600.02-162/H 5-2 L-

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FIG. 5 EXTENDED BLOW DOWN CECO RUN NO070X TT=33 i SHOREHAM NUCLEAR POWER STATION -UNIT I LOCAL BULK TEMPEHATURE DIFFERENCE i

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l TIM E - MI N UTES l FIGURE 6 COMPARISON OF MIT AND LASALLE LOCAL-TO-BULK TEMPERATURE DIFFERENCE , TEST No.1 SHOREHAM NUCLEAR POWER STATION-UNITI LOCAL BULK TEMPERATURE DIFFERENCE ,

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0 1 2 3 4 5 6 7 8 9 10 ll 12 13 I4 15 16 TIM E - MINUTES FIGURE 7 COMPARISON OF MIT AND LASALLE LOCAL-TO-BULK TEMPERATURE DIFFERENCE, TEST No. 2 SHOREHAM NUCLEAR POWER STATION-UNIT 1 LOCAL BULK TEMPERATURE DIFFERENCE

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FIGURE 8 COMPARISON OF MIT AND LASALLE LOCAL-TO-BULK TEMPERATURE DIFFERENCE, TEST No.3 SHOREHAM NUCLEAR POWER STATION-UNIT I LOCAL BULK TEMPERATURE DIFFERENCE

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FIGURE 10 COMPARISON OF MIT AND LASALLE LOCAL-TO-BULK TEMPERATURE DIFFERENCE, TEST No. 5 SHOREHAM NUCLEAR POWER STATION UNIT l LOCAL BULX TEMPERATURE DIFFERENCE i

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SECTION A LOCATIONS USED FOR H s 1.0 FOOT SECTION 8 LOCATIONS USED FOR H:1.53 FEET TREE C' USED ONLY FOR 6 : O' TESTS ,

FIGURE 11 THERMISTOR PROBE LOCATIONS SHOREHAM NUCLEAR POWER STATION-UNIT 1 LOCAL BULK TEMPERATURE DIFFERENCE

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31.66 j 40.31 FIGURE 12 SPATIALTEMPERATURE DISTRIBUTION SHOREHAM NUCLEAR POWER STATION-UNIT l LOCAL isuLK TEMPERATURE DIFFERENCE I

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PROTOTYPE TIME IN SECONDS ,

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-20 30 60 90 12 0 15 0 180 210 STEAM FLOW MODEL TIME IN SECONDS STEAM FLOW STARTED STOPPED AT 266 SEC FIGURE 13 TEMPORAL TEMPERATURE DISTRIBUTION RESULTS FOR EXPERIMENT 16 SHOREHAM NUCLEAR POWER STATION-UNITI LOCAL BULK TEMPERATURE DIFFERENCE

._ ___. _ _ _ _ _