ML20141A270

Forwards RAI on Section 12, Clime Noding Study, of WCAP-14407, Wgothic Application Rept. Portions of Rept Requested to Be Withheld from Public Disclosure Does Not Contain Info for Which Exemption Sought

ML20141A270
Person / Time
Site:	05200003
Issue date:	05/14/1997
From:	Diane Jackson NRC (Affiliation Not Assigned)
To:	Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9706200196
Download: ML20141A270 (7)

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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20666-0001

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%* . . . ,o! May 14, 1997 Mr. Nicholas J. Liparulo, Manager Nuclear Safety and Regulatory Activities Nuclear and Advanced Technology Division -

Westinghouse Electric Corporation  ;

P.O. Box 355 Pittsburgh, PA 15230 I I

SUBJECT:

REQUESTS FOR ADDITIONAL INFORMATION (RAIs) ON SECTION 12 " CLIME N0 DING STUDY," 0F WCAP-14407, "WG0THIC APPLICATION REPORT" I

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Dear Mr. Liparulo:

The Nuclear Regulatory Commission's (NRC) Containment Systems and Severe Accident Branch (SCSB) staff reviewed Section 12, " Clime Noding Study," of WCAP-14407, "WG0THIC Application Report," which was submitted by Westinghouse Electric Corporation (the applicant) on March 14, 1997, and determined that it needs additional information in order to complete its review of the AP600 passive containment cooling system and MG0THIC computer code. Enclosed are questions identified as RAlf 480.1022 to 480.1041. It is expected that WCAP-14407 will be updated to reflect the questions and comments enclosed in l this letter.

You have requested that portions of the information submitted in the June 1992 application for design certification be exempt from mandatory public disclo-sure. While the staff has not completed its review of your request in i 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 l

not contain those portions of the information for which exemption is sought.

i 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  ;

i withheld from public disclosure in accordance with 10 CFR 2.790, this letter  !

will be placed in the Nuclear Regulatory Commission Public Document Room. I u

1 NBC FRE CENTEB COPY r00009 o@1 '

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9706200196 970514 PDR ADOCK 05200003 A PM ,

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Mr. Nicholas J. Liparulo May 14, 1997 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 j Docket No.52-003 l

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Enclosure:

As stated cc w/ enclosure:

See next page  ;

DISTRIBUTION:

• Enclosure to be held for 30 days

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DOCUMENT NAME: A:W14407 4

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! Mr. Nicholas J. Liparulo Docket No.52-003 Westinghouse Electric Corporation AP600 cc: Mr. B. A. McIntyre Ms. Cindy L. Haag Advanced Plant Safety & Licensing Advanced Plant Safety & Licensing

Westinghouse Electric Corporation Westinghouse Electric Corporation l Energy Systems Business Unit Energy Systems Business Unit P.O. Box 355 Box 355 Pittsburgh, PA 15230 Pittsburgh, PA 15230 i Mr. M. D. Beaumont Mr. S. M. Modro i

Nuclear and Advanced Technology Division Nuclear Systems Analysis Technologies

! Westinghouse Electric Corporation Lockheed Idaho Technologies Company One Montrose Metro Post Office Box 1625 11921 Rockville Pike Idaho Falls, ID 83415 Suite 350 Rockville, MD 20852 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 i Suite 300 l Washington, DC 20006-3706 Mr. Robert H. Buchholz l GE Nuclear Energy l 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 Floor I Pittsburgh, PA 15219 Mr. Charles Thompson, Nuclear Engineer AP600 Certification Mr. Frank A. Ross NE-50 U.S. Department of Energy, NE-42 19901 Germantown Road l Office of LWR Safety and Technology Germantown, MD 20874 l 19901 Germantown Road

. Germantown, MD 20874 i

Mr. Ed Rodwell, Manager PWR Design Certification Electric Power Research Institute 3412 Hillview Avenue Palo Alto, CA 94303

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AP600 - REQUEST FOR ADDITIONAL INFORMATION ON WCAP-14407, SECTION 12, " Clime Noding Study" On Page 12-1 of WCAP-14407, the applicant states: "A detailed description of the GOTHIC Code and the modifications implemented in the amended code as MGOTHIC is presented in Section 3.2 of this report." That section currently describes MGOTHIC Version 4.0. However, in the letter of transmittal (Ref:

NSD-NRC-97-5010, dated March 14, 1997), the applicant states that the sensi-tivity calculations performed in Chapter 12 were done using WGOTHIC Ver-sion 4.1, which corrects an error in the clime model calculation, as well as a j

significant number of additional changes to the AP600 model description.

480.1022 The applicant needs to expand the one sentence discussion of the technical differences between MGOTHIC Versions 4.0 and 4.1 pre-sented in the cover letter and incorporate this discussion in the body of WCAP-14407, specifically the over-prediction of heat i

removal from a cline which experiences dryout. Describe the.

changes to the "ccvel" subroutine and its impact on the annulus

! inertia lengths.

480.1023 The applicant needs to provide an evaluation of the differences between MG0THIC Versions 1.2 and 4.1 on the previous calculations presented in the "WGOTHIC Code Description and Validation"

report, WCAP-14382. This evaluation should present a technical justification why these existing calculations remain valid, and

' consider the "ccvel" subroutine and the changes to the annulus inertia lengths. Those calculations deemed most likely to be l

impacted by the change from Version 1.2 to Version 4.1 should be rerun (at a minimum, Tests 214.lA, 214.1B, 216.1B, 219.1A, 219.lB, 219.1C, and 222.4B) and provide comparison plots of  ;

pressure, passive containment cooling system (PCS) air and film temperature, heat flux, and heat removal rate. l

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The following questions refer to the Clime Noding Sensitivity Study discussed in Section 12.2.1 and the results presented in Section 12.3.1.

480.1024 a) Why was an arbitrary selection process used to define the downcomer-to-riser volume ratio?

b) Why is the sensitivity model much shorter than the AP600?

c) The applicant needs to compare (in tabular form) the Reynolds, Prandtl, and Grashof numbers for the coolant flow through the downcomer and annulus in the Section 12.1 sensi-tivity study model to the Section 12.2 AP600 containment model.

480.1025 a) The applicant needs to justify the use of the selected film flow rate for two of the three sensitivity studies. This value is 20 times greater than the value selected which results in dryout in the simulated riser section.

Enclosure

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b) The applicant needs to compare the Gama,( r - lbm/ft-sec),

and the Reynolds number for the film flows used in the Sec-

tion 12.1 sensitivity study model to the Section 12.2 AP600 j containment model.

480.1026 In Figure 12-3, the applicant needs to identify the climes and 4

resistances which represent the thick steel plate. ' Also, identify the climes and resistances which represent the acrylic

! plate.

480.1027 a) What does the thick steel plate represent in the AP600? If i'

it is the AP600 containment shell, why is it much thinner and why not include the inorganic zinc paint? If it is the baffle, why was the baffle modeled much thicker than the actual baffle dimension for the AP6007 b) What does the acrylic plate represent in the AP6007 If it is.  !

the baffle, does the acrylic plate provide a satisfactory representation of the heat transfer to the downcomer?

c) What is the impact of the acrylic baffle on the sensitivity results?

t I d) Compare the Biot number for the thick steel plate and the f

acrylic cover to either the AP600 containment shell or baffle plate, which ever is correct.

480.1028 The applicant needs to justify the selection of a sub-atmospheric

pressure boundary condition. Also, identify the node noted on i Page 12-6 as the fixed pressure boundary

Figure 12-3 shows an

exit and an entrance node, Nodes IP and 2P, which are

! unconnected.

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480.1029 On Page 12-5 of WCAP-14407, the applicant states that the riser

and downcomer stacks were divided into nodes of equal size. What values were given for the volumes, flow areas, frictional lengths t

and boundary conditions for the exit and entrance nodes (Nodes IP and 2P of Figure 12-3)?

480.1030 Why does the drain require the addition of a dumy clime? Could not a simple volume (Volume 18) be added to facilitate draining of the annulus runoff, instead of a dumy clime which has dumy heat transfer connections to the containment and from the downcomer? As the AP600 Evaluation Model uses an " evaporation limited flow," why was it necessary to add this dumy clime to the AP600 Evaluation Model?

480.1031 The applicant needs to justify the use of a constant temperature heat source for the Clime Sensitivity Model. In the MG0THIC evaluation model, the temperature of a dry clime would be much I

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hotter than a wet clime. This model forces the surface tempera-ture to remain the same, artificially minimizing the impact of temperature dependent differences on evaporation and radiation heat transfer rates.

480.1032 The applicant needs to confirm the accuracy of the information presented in Figures 12-18 and 12-19. Have these two figures been erroneously exchanged during the document preparation pro-cass?

480.1033 The applicant needs to provide plots showing the annulus and downcomer pressure, density, and flow velocity profiles for the three clime models at 2000 seconds.

480.1034 On Page 12-8, the applicant states that figures provided show that the MG0THIC results were close to steady-state at the end of the 2000-second transient period. Since 2000 seconds are required for the annulus air flow calculations +o approach steady-state, an initialization procedure must be used by West-inghouse to set the MG0THIC downcomer and annulus air flow veloc-l ities to their steady-state values in lieu of preceding the start of the blowdown calculations with a 2000 second " null-transient."

! The applicant needs to describe this procedure and provide a technical justification for its use.

The following questions refer to the AP600 Containment Clime Noding Sensitivity Study discussed in Section 12.2.2 and the results presented in Section 12.3.2.

l 480.1035 The applicant needs to incorporate the changes to the MGOTHIC Evaluation Model, as described on Pages 12-6 and 12-7, into the Evaluation Model description provided in Section 4 of WCAP-14407.

l 480.1036 The applicant needs to provide an evaluation of the differences l between MG0THIC Versions 4.0 and 4.1 on the previous calculations l

presented in the current "MG0THIC Application to AP600" report, WCAP-14407. This evaluation should present a technical justifi-cation why these existing calculations remain valid. Those calculations deemed most likely to be impacted by the change from version 4.0 to 4.1 (including the modeling changes related to bolow operating deck region loss factors, heat structures, l renodalization, and modified mass and energy releases) should be rerun and comparison plots of pressure, PCS air and film tempera-l ture, heat flux, and heat removal rate should ba presented.

480.1037 a) The applicant needs to provide a more detailed discussion of

' the AP600 models used for the case with an increase in the number of climes in a stack (the axial sensitivity study) and

' the case with an increase in the number of stacks (the azi-muthal sensitivity study).

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l b) As in all MG0THIC analyses previously submitted for staff review, do these cases also include a "one-to-one" correspon-dence of a GOTHIC PCS annulus fluid node to clime pair (the wet and dry regions) to containment dome (above operating deck region) fluid node? If not, and considering the with-drawal of Section 13 from WCAP-14407 on noding studies in support of the evaluation model, how does Westinghouse con-clude that the dome above operating deck region)'

nodalization is appro(priate, provides a converged solution, and does not contains numerical instabilities?

c) Particularly for the azimuthal study provided, with fixed fluid boundary nodes it does not appear to the staff that i

there would be any differences (temperatures, heat fluxes, i etc.) between the set of wet or set of dry climes associated '

with the same set of boundary nodes. Please provide an explanation.

! 480.1038 Figures 12-28 through 12-36 all terminate at about 43,200 seconds (12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />). Please extend these figures to span 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Do any of the wet stack climes experience drycut in this time period? If so, plean indicate the time of dryout on the fig- l ures. Is this the dryout behavior expected for the AP600 loss-l of-coolant-accident (LOCA)?

( 480.1039 Are the changes (both to WG0THIC 4.1 and to the AP600 model) expected to impact the main steam line break (MSLB) cases?

l 480.1040 The applicant needs to provide comparative plots of heat flux and l film temperatures versus clime location for a representative wet ,

l stack and the heat flux and shell surface temperature versus clime location for a representative dry stack for the " base case clime" and " increased number of climes case" AP600 models prior l to blowdown, at 30 seconds, at 1500 seconds, and at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

l 480.1041 The applicant needs to provide the annulus and downcomer pres- '

sure, air temperature, density, and flow velocity profiles for the " base case clime" and " increased number of climes case" AP600 models prior to blowdown, at 30 seconds, at 1500 seconds and at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. How does Westinghouse confirm that these profiles represent stable and converged flow solutions?

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