ML18139A062

Forwards Containment Spray Mods Drawdown Test Description in Response to NRC 800208 Request.Test Will Provide Assurance That Caustic Addition Can Be Maintained in Order to Achieve Required Iodine Removal

ML18139A062
Person / Time
Site:	Surry
Issue date:	03/20/1980
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Harold Denton, Eisenhut D Office of Nuclear Reactor Regulation
References
187, NUDOCS 8003250351
Download: ML18139A062 (11)

Text

e VIRGINIA ELECTRIC AND POWER COMPANY RrcHMOND,VIROINIA 23261 March 20, 1980 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation Attn:

Mr. Darrel G. Eisenhut Acting Director, Division of Operating Reactors U.S. Nuclear Regulatory Commission Washington, D.C.

20555

Dear Mr. Denton:

Serial No. 187 PO/HEC:smv Docket Nos:

50-280 50-281 License Nos:

DPR-32 DPR-37 CONTAINMENT SPRAY MODIFICATIONS DRAWDOWN TEST SURRY POWER STATION UNITS 1 AND 2 The attached report entitled "Refueling Water Storage Tank/Chemical Addition Tank - Drawdown Test" is provided for your review and comment.

This report was requested by your staff in our meeting of February 8, 1980 for the dis-cussion of modifications to the Surry containment spray system.

Additional information on containment spray pH curves and post accident sump history will be transmitted the week of April 7, 1980.

Drawdown testing for Unit 2 as described in this report is tentatively sche-duled for March 26, 1980.

We believe that this test will provide assurance that caustic addition can be maintained in order to achieve the required iodine removal.

HEC/smv:4Jl Attachment cc:

Mr. James P. O'Reilly, Director Office of Inspection and Enforcement Region II Very truly yours,

/

C C. M. Stallings Vice President - Power Supply and Production Operations

1.0 GENERAL REFUELING WATER STORAGE TANK/

CHEMICAL ADDITION TANK DRAWDOWN TEST 1.1 Scope of Pretest Report The Pretest Report describes:

(1) the rationale of the RWST-CAT drawdown testing, (2) the drawdown test limitations, (3) the test scenario and how the test will be performed, and (4) how the test results will be interpreted.

1.2 Chemical Addition Method and Preliminary Results Among various possible chemical addition methods, the direct suc-tion of the caustic solution by the containment spray pumps was retained as a simple and reliable means to achieve the proper

• spray pH and sump pH.

Preliminary analyses showed that under all design basis accident scenarios, the spray and sump pH can be maintained between specified maximum and minimum limits.

1.3 Scope of RWST-CAT Drawdown Test The drawdown test is designed (1) to determine the actual head losses in the piping system to. be used_ in the final pH analyses and (2) to demonstrate that the -drawdown, analytically calculated, is in reasonable agreement with the measured drawdown during the test.

2.0 RATIONALE OF THE RWST-CAT DRAWDOWN TESTING 2.1 Head Losses in the Piping System The CAT drawdown is in essence a function of two independent parameters, namely, the RWST drawdown and head losses in the piping system.

While the RWST drawdown does not pose any concern regarding the analytical calculations, depending only on the number of pumps in operation which are well defined under each scenario, the head losses depend on the ability of the analyst to estimate correctly the numerical values of these losses.

These head losses when used in the preliminary pH analyses show that a large margin of uncertainty would still allow the system to main-tain pH within acceptable limits.

For the final pH analyses, however, measured head losses obtained during the drawdown test will be used.

2.2 Capability of an Analytical Approach to Calculate the Spray pH For any specific caustic concentration given in the CAT, the spray pH is a function of the ratio between the flow rate ex-tracted from CAT and the flow rate extracted from RWST by the same containment spray pump.

Since the variation of <;he flow

e rate from the CAT determines the CAT drawdown, the CAT drawdown and the spray pH are interrelated and, therefore, if the CAT draw-down can be calculated with sufficient accuracy under any possible scenario (number of pumps in operation), the spray pH can also be calculated.

The flow rate from the CAT, which ultimately dictates the CAT drawdown, is not constant in time since it depends on the RWST drawdown and, strictly from a hydraulic standpoint, the flow from CAT is under unsteady-flow conditions.

However, the RWST draw-down takes place slowly, the CAT piping system is short, *and the velocity* variation takes place gradually; therefore, no appreci-

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state flow conditions for a weak unsteady flow phenomenon.

Nevertheless, since the method used in calculations uses a simpli-fied set of equations, the best approach to check the sensitivity and accuracy of the calculation is to perform a test under speci-fied test conditions as well as calculations under the same con-ditions and compare the results.

3.0 TEST LIMITATIONS The RWST-CAT drawdown test at Surry 2 is subject to certain limitations.

3.1 The actual fluid in CAT will be a caustic solution, approximately 16 percent weight NaOH concentration.

Disposal of such a fluid is controlled by environmental regulations.

Holding the mixture of caustic solution from CAT with boric acid solution from RWST in a separate tank or pond for treatment before disposing the mixture is impractical considering the volume of such a temporary reservoir.

For the test, therefore, water will be used in the CAT.

Since water and caustic solutions have different physical properties, certain considerations are pertinent.

3.1.1 Water and caustic solution have different viscosities.

A caustic solution of 16 percent concentration is approxi-mately three times more viscous than water.

This viscosity difference affects the piping head losses.

These viscosity differences generally affect the friction losses but have only a slight effect on local losses (i.e, losses in tees, elbows, etc.).

The local losses, therefore, are not usually calculated as being functions of viscosity.

Since the CAT piping system is short and the bulk of the head losses are due to local losses, the differences due to viscosity can be considered negligible.

3.1.2 Water and caustic solution have different specific weights; the specific gravity of the caustic solution of 16 percent concentration is approximately +/-1.17 depending on tempera-ture.

The specific weight 0£ the fluid is an important

parameter and a 17 percent variation is significant.

How-ever, the test is designed to prove in general the capa-bility of an analytical approach in predicting drawdowns.

In this case the only precaution is to select.proRerly the test value of initial elevations in the RWST and the CAT in order to keep the CAT drawdown, under testing conditions, close to the actual drawdown due to a fluid heavier than water (i.e., CAT Level will be slightly higher to compen-sate for differences in specific gravity).

If the analy-tical approach proves to be acceptable under testing conditions using water, there will be no discrepancy in predicting actual drawdown due to caustic solutions.

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380,000 gal. Under the actual scenarios where chemical addition is required, the RWST is full at the beginning of the scenario and empties during the event.

Any test simulating an actual scenario would require a temporary storage equal to the RWST volume plus the CAT volume.

Such a sto.rage is not available.

The only possible tempo-rary holding reservoir is the reactor cavity with a storage of approximately 200,000 gal.

Since the test is not designed to simulate any of the actual scenarios in particular, using a test scenario which will remove 200,000 gal. from-the RWST will not affect either the general intention of the test or its results.

3.1~4. The actual scenarios require the operation of a minimum of three pumps and a maximum six pumps for a duration varying between 80 miri. and 50 min. respectively.

Since the test RWST

• drawdown has to be limited to a total volume of 200,000 gal., the total number of pumps used in the test will be limited in order to keep a test duration close to the actual caustic addition time duration.

4.0 TEST DESCRIPTION 4.1 General Parameters 4.1.l Fluids used in the test RWST - actual boric acid solution CAT - water 4.1.2 Pumps used during the test One CS pump (Train "A")

One LHSI pump 4.1.3 Flow rates during the test CS pump - Q(cS) = 2,000 gpm (in actual scenarios Q(cs) is between 1,800 gpm and 2,200 gpm tHSI pump - Q(LH) = 3,000 -

3~500 gpm

e 4.1.4 Pumping Sequence Both the CS pump and LHSI pump will be in ope~ation for approximately 13 min.

Only one CS pump wi;n be. in opera-tion for the remainder of the test.

(Under actual condi-tions, one or two CS pumps are initially operated together with another two or four pumps, and later,* these other

. pumps are shut down or transferred to the recirculation mode.)

NOTE:

Parameters to be monitored in the test are.shown in

.Attachment 4.

4.2 Test Description 4.2.1 RWST initially filled to elevation ZRWST = 55 ft-6 in 4.2.2 CAT initially filled to elevation ZCAT = 57 ft-6 in 4.2.3 With the CAT line isolated, operate the CS pump for approxi-mately 5 min. to fill the CS piping and to adjust the flow rate to approximately 2,000 gpm.

4.2.4 With the CAT line isolated, operate the CS pump and the LHSI pump and carefully monitor the RWST elevation.

When ZRWST = 51 ft-0 in, open MOV~202-B (see Attachment No. 1).

4.2.5 When.ZRWST = 42 ft-1 in, shut down _the LHSipump and iso-late its suction line; continue to operate the CS pump *

.. - -4.. 2. 6. When the reactor cavity is full or when RWST !eve~- reaches 30 ft, shut.down the CS pump and isolate its discharge line.

• 4.3 Calculated RWST -

CAT Drawdown for the Test Scenario Attachment No. 2 shows the CAT drawdown expected during the test if the RWST drawdown shown on Attachment No. 3 and all the other test inputs are maintained as specified in the test scenario.

Since deviations of the actual test conditions from the specified test conditions are inherent, the CAT drawdown shown in Attachment No. 2 is intended to show the general shape of the flow variation from the CAT during the test (similar to the shape calculated for actual scenarios), the order of magnitude of the flow rates (flow rates of the same order of magnitude with the flow rates under actual scenarios), and the approximate drawdown time duration (close to the duration of actual scenarios).

4.4 Determination of Head Loss Coefficients Attachment Nos. 2 and 3 show that, during the test, the flow rates and piezometric heads will vary gradually.

The CAT drawdown is not expected to exceed 5 in/min.

The RWST drawdown will not ex-ceed 8 in/min. with two pumps in operation and 3 in/min. with one pump operating.

The flow rate from the CAT will not exceed a

variation of 0.5 gpm/min.

Because of these moderate changes, the data collected during testing will allow an accurate determination of the head loss coefficients.

These coefficients will be used later in the final pH analyses.

5.0 INTERPRETATION OF TEST RESULTS 5.1 General Upon completion of the test, the test results will be analyzed in the field to ensure validity.

Following this, the curves estab-lished by the data obtained from the test will be compared with calculated curve_s to determine differences in calculated and actual test results.

5.2 Calculated Drawdown vs Measured Drawdown The data collected during the drawdown test will furnish the fol-lowing information:

5.2.1 RWST drawdown:

This is a curve showing the actual variation of the fluid elevation in the RWST vs time and it depends on (1) the actual flow rates of the CS pump and LHSI pump during the test, which may vary with time, and (2) the actual ini-tial elevation in the RWST.

5.2.2 CAT drawdown:

This is a curve showing the actual variation of the_ fluid elevation in the CAT vs time starting from an initial elevation in the CAT.

5.2.3 CAT flow rate vs time history:

This is a curve showing the transient flow from CAT.

NOTE:

Analyzing the nature of the above three curves, it is apparent that the CAT drawdown and the CAT flow rate vs time history are dependent on the RWST drawdown while the RWST drawdown is an independent curve.

Since the RWST drawdown is an independent factor (de-pending on testing conditions only), it can be used as a

testing condition input in calculating two

curves, the CAT drawdown and the CAT flow rate vs time history.

If the calculated curves and the corresponding curves determined based on test measurements are in a reason-able agreement (discrepancies which can be tolerated in the final pH analysis) the analytical method can be con-sidered sufficiently accurate to predict drawdowns for actual scenarios similar to the_ test scenario.

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e Page 1 of 1 Parameters Monitored in the Test Specific weight (or specific gravity) of the fluid in the RWST Tempra ture of the fluid in the RWST Specific weight (or specific gravity) of the fluid in the CAT

• Temperature of the fluid in the CAT Relative variation* of fluid elevation in* the RWST (continuous recording)

Absolute variation of fluid elevation in the RWST (discrete fluid eleva-tion measurements using a transparent tubing)

Relative variation of fluid elevation in the CAT (continuous recording)

Absolute variation of fluid elevation in the CAT (discrete fluid eleva-tion measurements using a transparent tubing)

Pressure variation at the CS pump suction (junction point between CS piping and CAT piping) - continuous recording.

Piezometric head variation at the CS pump suction (discrete piezometric head measurements using a transparent tubing)

Pressure drop across the restrictive orifice in the CAT line (continuous recording)

CS pump* flow rate variation (continuous recording)

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