ML20210M704
| ML20210M704 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 06/27/1997 |
| From: | Diane Jackson NRC (Affiliation Not Assigned) |
| To: | Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| References | |
| NUDOCS 9708220144 | |
| Download: ML20210M704 (8) | |
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NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. 30666 4 001
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Dane 27, 1997 Mr. Nicholas J. Liparulo, Manager Nuclear Safety and Regulatory Activities i
Nuclear and Advanced Technology Division Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, PA 15230
SUBJECT:
REQUESTS FOR ADDITIONAL INFORMATION (RAls) ON THE DESCRIPTION OF THE METHOD TO ACCOUNT FOR CIRCUMFERENTIAL (2-DIMENSIONAL) CONDUCTION THROUGH THE STEEL CONTAINMENT SHELL FOR CONTAINMENT PRESSURE ANALYSES
Dear Mr. Liparulo:
The Nuclear Regulatory Commission (NRC) staff reviewed the new information provided by Westinghouse in letter NSD-NRC-97-5152, "AP600 Design Changes to Address Post 72-Hour Actions," dated May 23, 1997, Attachment 2 - Description of method to account for circumferential (2-dimensional) conduction through the steel containment shell for containment pressure analyses. The staff has determined that it need-additional information in order to continue its review of the Westinghos,a AP600 passive containment cooling system and MGOTHIC computer code.
Enclosed are questions identified as RAI# 480.1051 to 480.1077.
5 You have requested that portions of the information submitted in the June 1992, application for design certification be exempt from mandatory public disclosure.
While the staff has-not completed its review of your request in accordance with the requirements of 10 CFR 2.790, that portion of the submit-ted information is being withheld from public disclosure pending the staff's final determination. The staff concludes that these questions and comments do not contain those portions of the information for which exemption is sought.
However, the staff will withhold this letter from public disclosure-for 30 calendar days from the date of this letter to allow Westinghouse the opportunity to verify the staff's conclusions.
If, after that time, you do not' request that all or portions of the information in the enclosures be withheld from public disclosure in accordance with 10 CFR 2.790, this letter will be placed in the NRC Public Document Room.
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. m2 9708220144 970627 PDR ADOCK 05200003 A
Mr. f'4cholas J. Liparulo June 27,1997 Please update the open item tracking system with these RAls referenced under draft safety analysis report Chapter-21.
If you have any questions regarding this matter, you may contact me at (301) 415-8548.
Sincerely, original signed by:
Diane T. Jackson, Project Manager Standardization Project Directorate Division of Reactor Program Management Office of Nuclear Reactor Regulation Docket No.52-003
Enclosure:
As stated cc w/ encl:
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WDean, 0-5 E23 JMoore, 0-15 B18 CBerlinger, 0-8 H7 EThrom, 0-8 H7 GHolahan, 0-8 E2 DOCUMENT NAME: A:2DMODEL.RAI To retelve a copy of tNo aloeuenent,Indcate in the boa: "C" = Copy without ettechment/enctoeure
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NAME=
DTJackson:sg %)f\\ TRQuay471 M DATE 06/M/97
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0FFICIAL RECORD COPY
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Mr. Nicholas J. Liparulo Docket No.52-003 Westinghouse Electric Corporation AP600 l
cc: Mr. B. A. McIntyre Ms. Cindy L. Haag Advanced Plant Safety & Licensing Advanced Plant Safety & Licensing Westinghouse Electric Corporation Westinghouse Electric Corporation Energy Systems Business Unit Energy Systems Business Unit P.O. Box 355 Box 355 Pittsburgh, PA 15230 Pittsburgh, PA 15230 Mr. S. M. Modro Nuclear Systems Analysis Technologies Lockheed Idaho Technologies Company Post Office Box 1625 Idaho Falls, ID 83415 Enclosure to be distributed to the following addressees after the result of the proprietary evaluation is received from Westinghouse:
Mr. Ronald Simard, Director Ms. Lynn Connor Advanced Reactor Programs DOC-Search Associates Nuclear Energy Institute Post Office Box 34 1776 Eye Street, N.W.
Cabin John, MD 20818 Suite 300 Washington, DC 20006-3706 Mr. Robert H. Buchholz GE Nuclear Energy Mr. James E. Quinn, Projects Manager 175 Curtner Avenue, MC-781 LMR and SBWR Programs San Jose, CA 95125 GE Nuclear Energy 175 Curtner Avenue, M/C 165 Mr. Sterling Franks San Jose, CA 95125 U.S. Department of Energy NE-50 Barton Z. Cowan, Esq.
19901 Germantown Road Eckert Seamans Cherin & Mellott Germantown, MD 20874 600 Grant Street 42nd Flcor Pittsburgh, PA 15219 Mr. Charles Thompson, Nuclear Engineer AP500 Certification Mr. Frank A. Ross NE-50 U.S. Department of Energy, NE-42 19901 Germantown Road Office of LWR Safety and. Technology Germantown, MD 20874 19901 Germantown Road Germantown, MD 20874 Mr. Ed Rodwell, Manager PWR Design Certification Electric Power Research Institute 3412 Hillview Avenue Palo Alto, CA 94303 o
m REQUESTS FOR ADDITIONAL INFORMATION Chapter 21:- Containment and Severe Accident Branch (SCSB)
L
References:
j
-1.
- " Description of Method to Account for Circumferential (2-Dimensional)
Conduction Through the Steel Containment Shell for Containment Pressure Analyses," Attachment 2 of NSD-NRC-97-5152, May 23,1997.
- 2.'-
WCAP-14407, "WGOTHIC Application to AP600," A. Forgie, et al., September 1996.
-Pa. 1:
Section 1:
Introduction 480.1051-The Water Distribution Test (WDT) and the Large Scale Test (LST) are referenced to support the conclusion that an alternating pat-tern of wet and dry vertical stripes will form, with known coverage values for different applied flow rates and heat fluxes. The WDT, which had a prototypical water distribution system, was performed
-only at cold conditions. The heated LST had a non-prototypical water distribution-system (J-tubes) instead of notched weirs, and had only one data point with a wetted coverage area in the range of interest for this evaluation.- The vertical sections of both of these test facilities were much-shorter than the AP600. Given these limitations, justify the statements made in the second para-graph quoted below:
"As evidenced by _ test-data. the flow distribution weirs develop alternating wetted and dry, vertical stripes of-containment surface areas. These' stripes become clearly segregated as the. applied water flow rate is reduced. Heat removal from the wetted area is greater than...".
Pa. 1:
Section 2:
Effect of Circumferential f 2-D) Conduction....
480.1052-Describe, or provide a reference to.the description of the relevant AP600 water distribution tests that show "the outside surface of the containment shell will be partially wetted when the applied water flowrate is reduced below the high initial flowrate." -Pro-vide a table which summarizes the observed striping characteristics as a function of applied flow rate and axial height for the cold 1
WDT tests. This table must provide the range of parameters tested for each " striping test," e.g.,- test ID, flow rate, film tempera-ture, observed coverage fraction, number of wet and dry stripes,-
widths of the stripes at the springline, and stripe widths at the bottom of test section.
480.1053-Provide " striping"Linformation for the heated-LST tests (Ref. 2).
This table must provide the range of parameters tested for each
" striping test," e.g., test ID, flow rate, heat flux, film tempera-ture, observed coverage fraction, number-of wet and dry stripes, Enclosure
y 2
widths of the stripes at the springline (for any tests where this observation may have been made), and stripe widths at the bottom of test section.
Pa. 2:
Section 2.1: Geometry of the Wet and Dry Vertical Strices 480.1054 Justify the assumption that stripes-are always centered under a weir notch. What is the impact of plate misalignments and welding imperfections? What is the impact of the baffle plate standoffs, if any? The second weir'is at the 50 foot radius, and the springline is at 65 foot radius. Water leaving the second weir-must travel about 45 feet to reach:the springline. Does the WDT data records indicate whether stripes were always centered under each weir notch in all tests?
480.1055 Justify the assumption-that the stripe width is uniform over the entire PCS shell. What effects would a non-uniform heat-flux through the shell (due to off-center break location, or jet im-pingement) have on the placement of PCS wet / dry stripes.
Show that the assumption of uniform stripe width is valid even when evapora-tion causes the flow to drop below the minimum stable flow. How are the dome regions above the second weir handled?
Pa. 2:
Section 2.2:
Inside and-Outside Heat' Transfer Boundary Conditions 480.1056-Describe the differences between the:model used.'or the 1-dimensional steady-state calculations of the PCS and the MGOTHIC Evaluation Model. Why was the WGOTHIC Evaluation Model (described in Chapter 4 of Ref. 2) not used? Are the mass and heat transfer correlations biased as in the evaluation model-or are the nominal valuer used?
480.1057 List the assumptions used to derive the inside and outside boundary.
conditions for the 1-D and 2-D heat conduction models.
Provide details of the polynomial fits and values for the heat transfer coefficients and boundary conditions used at the design containment pressure and at half of the design containment pressure.
480.1058 Explain why the 1-dimensional steady state heat transfer rates calculated at all containment pressure /temperatura conditions are higher than the corresponding heat transfer rates calculated by WGOTHIC, when both calculations' use the same heat and mass transfer methodology?
'480.1059 Provide a schematic drawing of the 1-dimensional model with all boundary and symmetry conditions specified. Show the mesh spacing selected. State whether the baffle was included in the model.
List the values used for all input parameters in the 1-dimensional steady-state conduction. study.
Identify any differences in these parameter _s from the MGOTHIC Evaluation Model (Chapter 4 of Refer-ence 2).
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3 1
480.1060= Provide. figures which show the-results of the 1-dimensional calcu-lations for the shell surface temperatures (inside and outside) and for the heat fluxes calculated over the range of containment pres-sures.
Paae 3: Conduction (ANSYS) Model Description 480.1061 Provide a schematic drawing of the 2-dimentional model with all boundary and symmetry conditions specified.
Show the mesh spacing selected.- State whether the baffle was included in the model.
List the values used for input parameters in the 2-dimensional conduction study, including the containment and annulus boundary conditions actually used for-the 2-D-ANSYS-simulation and the steady-state 1-dimensional, radial temperature profile used as the initial condition for the 2-dimensional study.
Identify.any dif-ferences in these parameters from the WG0THIC Evaluation Model (Chapter 4 of Reference 2).
480.1062 The 'ANSYS conduction model description does not mention the. special coating which.is applied inside and outside the PCS shell. The coating has a relatively low thermal conductivity and its omission may cause the 2-D analyses to be non-conservative.
Confirm that
= coatings were omitted in the 2-D conduction analyses. Compare the Figure 2 results to a calculation which includes these coatings.
Pa. 3: Section 2.4: Conduction (ANSYS) Model Results 480.1063 Explain the assumptions used to determine the evaporation rate from the 2-dimensional film as compared to the-1-dimensional prediction.
480.1064 Figures 3 and 4 indicate-the y-direction as being perpendicular to the shell surface. Consequently, the figure captions of Figures 5 and 6 quote the wrong directions. :They should read x-direction instead of y-direction.-- Therefore, on. Figures 5 and~ 6:
Correct the direction in figure captions
- - Add the thermal-flux results from 1-D computations
. Indicate clearly the boundaries between wet and dry surfaces Label'the axes correctly.
Explain the meaning (convention) of the minus values
~Pa. 4: Section 2.5:
Insiahts from the PCS Larae Scale Testina
- 480.1065. - Provide the experimentally measured evidence (i.e., thermocouple values and pressure-sensors) which support-the conclusion that an equal amount of heat was removed in test cases 212.1C and 213.1C.
Present a sample calculation which uses this sensor data.
480.1066-Provide the experimentally measured evidence (i.e., thermocouple-values) which-support the conclusion that elevated wet surface temperatures and enhanced water evaporation occurs at wetted loca-tions adjacent to dry stripes.
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4 Pa. 4: Section 3.0: Acolication to AP600 Containment Evaluation Model 480.1067 Provide a numerical example of' the calculation of the evaporation limited flow rate and the correction factors for 2-dimensional conduction. As Stetion 2.5 qualitatively describes the observed differences between test run RC048C of test matrix 212.1 and test run RC050C of test matrix 213.1, use these LST tests as the basis for this numerical example. After applying the film coverage methodology, compare the calculated results to the experimental data available.
Are the equivalent setted surface areas in the WG0THIC model larger than those that could be supported by the WDT data?
Pa. 5: Section 3.1: Calculatino Fraction of PCS Water That Does Not Evano-I. Alt 480.1068 Explain why assumption (1) is appropriate for the derivation pre-sented. The liquid flow is applied to an initially hot surface.
Quantities derived from cold tests must be confirmed for hot sur-face film flow behavior.
480.1069 Justify the inherent assumption of equation (3) that the evapora-tion rate is proportional to the flow rate.
Should not the evapo-ration rate be a function of the wetted surface area?
480.1070 Provide an explanation of the calculation procedure for the evapo-ration rate, @6, and for the flow rate per unit width, i s.
m Paae 8: Section 3.2:
Evanoration limited Flow Calculation 480.1071 What is the calculational procedure for the dome region above the second weir?
480.1072 How is the evaporation heat flux determined? Which and how many time values are ' selected times." Explain.
Pace 9:
480.1073 Clarify what is meant by the following sentence:
"...; thereby assuring that WG0THIC predicts limited evaporation of PCS water."
480.1074 Explain the convergence procedure used for the evaporation mass flux iteration. Specify the convergence criterion used for this procedure. What is meant by " consistent and slightly higher than the values assumed for input under Step 1 (Step 1 values come from WG0THIC)?
Specify how many interactions are commonly needed for convergence.
5 Paae 9:
Section 3.2:
Inclusion of 2-Dimensional Conduction Effects 480.1075 Westinghouse states that the film evaporation rate is also a func-tion of the stripe width.
Furthermore, it was stated before that the wetted stripe width resulted frcn experimental observations.
Provide further explanation of the sentence : 'Thus, the calcula-tion of-the width of the film stripe is accomplished by iteration."
480.1076 The sentence above Equation (16) is difficult to comprehend and should be rephrased such that both W an Wo are uniquely defined.
Define these terms clearly using words.
Is Equation (16) displayed in Figure 2 or derived from this figure by curve-fitting? How many calculated values were available for performing the curve fit? Is there a sensitivity to shell surface temperature, annulus air temperature, or film subcooling which is not included as parameters in the Equation (16) fit?
480.1077 The Westinghouse procedure adds wetted area to adjust for 2-D conduction effects. This additional wetted surface area removes more heat by evaporation. However, an equivalent dry area is removed, reducing radiation heat loss and convection from the dry surface. As evaporation is a significantly more dominant effect than radiation / dry surface conduction, the heat loss reduction from dry area reduction will not be consistent with the heat loss gain from wet area enlargement. Although the heat transfer rate may be maintained, the mechanisms driving the heat transfer are changed.
Faulty results may be obtained from non-physical adjustment proce-dures.
For example, Figure 2 suggests that decreasing wetted stripe widths (coverage area) will cause the normalized evaporation rates to go to infinity. Therefore, this curve could be used to
" optimize" the heat transfer by adjusting the coverage area.
WGOTHIC analysis may show that this is the preferential cooling mode for the PCS.
Please explain how Westinghouse will prevent this from occurring.
Indicate any technically meaningful limit line for this figure.
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