View source for NSD-NRC-97-5216, Forwards Response to RAI Re AP600 PCS Scaling Analysis. Responses Are Consistent W/Info Contained in Rev 2 to WCAP-14845, Scaling Analysis for Containment Pressure During Design Basis Accidents

{{Adams
| number = ML20148P997
| issue date = 06/27/1997
| title = Forwards Response to RAI Re AP600 PCS Scaling Analysis. Responses Are Consistent W/Info Contained in Rev 2 to WCAP-14845, Scaling Analysis for Containment Pressure During Design Basis Accidents
| author name = Mcintyre B
| author affiliation = WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
| addressee name = Quay T
| addressee affiliation = NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
| docket = 05200003
| license number = 
| contact person = 
| document report number = NSD-NRC-97-5216, NUDOCS 9707030192
| document type = CORRESPONDENCE-LETTERS, INCOMING CORRESPONDENCE
| page count = 81
}}

=Text=
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l t sbu gh Pennsylvania 15230-0355 t       Omtl0D NSD-NRC-97-5216 DCP/NRC0941 Docket No.: STN-52-003 June 27,1997 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555
         ' ATTENTION: T. R. QUA'Y ;
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==SUBJECT:==
AP600 RESPONSE TO REQUESTS FOR ADDITIONAL INFORMATION
                                                                                       ,                            /
Reference; (1) Westinghouse letter DCP/NRC/0933, dated 6/24'97

==Dear Mr. Quay:==

Enclosed are the Westinghouse responses to NRC requests for additional information related to the AP600 PCS scaling analysis. The RAI responses are consistent with the information contained in WCAP-14845, Rev. 2, " Scaling Analysis for Containment Pressure During Design Basis Accidents", June 1997 sent to you via Reference 1. Specifically, responses are provided for l   l y
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i olTS              RAI           olTS             RAI             olTS            RAI 5390            480.967         5415          480.992            5440          480.1017 l        5391            480.968         5416           480.993           5441          480.1018 5392            480.969         5417          480.994            5442          480.1019 5393            480.970         5418          480.995            5413          480.1020 5394            480.971         5419          480.996            5444          480.1021 l
5395            480.972         5420          480.997            5445          480.1022 5396            480.973         5421          480.998            5446          480.1023 5397            480.974         5422          480.999            5447          480.1024 5398            480.975         5423          480.1000           5448          480.1025         j 5399            480.976         5424          480.1001           5449          480.1026 l
5400            480.977         5425          480.1002           5450          480.1027 5401            480.978         5426          480.1003           5451          480.1028 5402            480.979         5427          480.1004           5452          480.1029 5403            480.980         5428          480.1005           5453          480.1030 5404            480.981         5429          480.1006           5454          480.1031
,        5405            480.982         5430          480.1007           5455          480.1032 1
5406            480.983         5431          480.1008           5456          480.1033         I 5407            480.984         5432          480.1009           5457          480.1034 5408            480.985         5433          480.1010           5458          480.1035 5409            480.986         5434          480.1011           5459          480.1038         l 5410            480.087         5435          480.1012           5252          480.1017 5411            480.988         5436          480.1013           5253          480.1018 5412            480.989         5437          480.1014           5254          480.1019 5413            480.990         5438          480.1015           5255          480.1020   l 5414            480.991         5439          480.1016           5256          480.1021   l These responses close, from the Westinghouse perspective, these items. The NRC should ruiew these responses and inform Westinghouse of the status to be designated in the "NRC               !
Status" column of the OITS.
Typographical errors and inconsistencies identified by the NRC in the previous revision of l WCAP-14845 were corrected in the text of WCAP-14845 Rev. 2, except for i .       (page 7-9) change + to = did not get implemented, and
! .       (page 7-14) It was intended to change um. p., to xm .,in Equation 108, but the "evap" subscript did not get deleted.
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Two typographical errors are noted .in WCAP-14845, Rev. 2:
e      page 10-24, second paragraph, the reference to Table 10-2 should be to Table 10-3
    .      page 11-6, two references to Table 10-10 should be to Table 10-3.
Please contact Bruce Rarig on (412) 374-4358 if you have any questions concerning this transmittal.
l   Brian A. McIntyre, Manager Advanced Plant Safety and Licensing i
Enclosure cc:    D. Jackson, NRC (w/ Enclosure)
N. J. Liparulo, Westinghouse (w/o Enclosure) l

NRC REQUEST FOR ADDIT'ONAL INFORMATION
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OITS 5390 RAI 480.967 (General) Many of the numbered equations, e.g. (1), contain multiple formulas and it is difficult to tell when one formula ends and another begins, insert semicolons or some other separator so it is clear where the separation between formulas is intended.

===Response===
The equations were revised in Reference 480.967-1 to include additional space, both horizontal and vertical, to clearly separate equations.
Reference 480.967-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
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i NRC REQUEST FOR ADDITIONAL INFORMATION l
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:                                                                                                             1 OITS 5391 RAI 480.968 (Page xv) Table E 1 has no n groups listed for Liquid Film Energy Transport, while Table 2-1 has two n groups listed. A second n group is missing in Table E-1 for Radiation Heat Transfer. Also, what is the basis for the 14 percent of condensation energy carried away by the film on the inside and 8         )
percent on the outside?                                                                                  1
  . Response:
Table E-1 was deleted ad Table 2-1 was revised in Reference 480.968-1 to specify the pi group ratios that define the Liquid Film Energy Transport. A note was added to clearly define the source and values for the pi groups. The 14% and 8% values are defined by the ratios in this note.
A note was added to Table 2-1 that radiation accounts for approximately 1/2 of the sensible heat transfer to and from the shell and heat sinks.                                                           ;
References 480.968-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment          l Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
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t NRC REQUEST FOR ADDITIONAL INFORMATION
!     OITS 5392 RAI 480.969 (Page xl) Two poids in Table P 1 should be clarified. The need was apparently identified for a 1/8 scale test and also for testing to determine the effect of hydrogen on heat transfer. Was the need for the 1/8 scale test satisfied by the large scale test (LST)? If so, it would help to state this. Also, this is the only mention of hydrogen effects, it would help to state how this concern was addressed.
Respense The needs originally identified for the LST were satisfied by the test.
A need for hydrogen was originally identified and was part of the LST test matrix. However, the data needed for design basis accidents, that are the subject of the containment evaluation model, do not include hydrogen (see PIRT, Reference 480.969-1, Section 4.4.2E). Consequently, Table P-1 of Reference 480.969-2 was revised by deleting the reference to hydrogen.
References                                                                                                        l 480.969-1 M. Loftus, D. Spencer, J. Woodcock, " Accident Specification and Phenomena Evaluation for AP600 Passive Containment Cooling System", WCAP-14812, Rev.1, Westinghouse Electric Corpora-tion.
480.969 2 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment                   l Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.                   '
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NRC REQUEST FOR ADDITIONAL INFORMATIOil
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l R..e OITS 5393 RAI 480.970 (Page xviii) The differences between the results of the scaling model and 'he evaluation model will
!   need to be explained in more detail than what is provided here.

===Response===
l   The discrepancy between the scaling model and the evaluation model presented in Reference 480.970-1 resulted from a comparison of nominal scaling model predictions to biased evaluation model predictions. Revised results presented in Reference 480.970-2 show both the trend and magnitude of predictions are similar when applied to the same case.
References l
480.970-1 D. Spencer, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. O, Westinghouse Electric Corporation.
480.970-2 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure D iring Design Basis Accidents", WCAP 14845, Rev. 2 Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5394 RAI 480.971 (Page xxxiv) The wording in the first paragraph needs to be changed to have the same meaning as in the body of the report on Page 10-20. The transient n group x,., clearly does not equal zero as stated here, (See wording in Section 10, Page 10-20.)

===Response===
The executive summary was extensively revised in Reference 480.9711 and this text was deleted.
Referenec 480.971-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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j   NRC REQUEST FOR ADDITIONAL INFORMATION iini HE I
OITS 5395 RAI 480.972 (Page xlii) The last paragraph in Element 2 refers to the distributed parameter WGOTHIC calculations.
If these calculations are no longer a part of the submittA '.his reference should be deleted.

===Response===
i The paragraph was deleted in Reference 480.972-1.                                                     ,
;   Reference 480.972-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-1 $845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION ss Em
                                                                                               #1     E OITS 5396 RAI 480.973 (Page xlii) Where are the sensitivity calculations referred to in Element 3 documented? Give a reference.

===Response===
The sensitivities are documented in Reference 480.973-1, Section 5. This reference was added to the text.
Reference 480.973-1 A. Forgie, J. Narula, R. Ofstun, D. Paulsen, S. Slabaugh, M. Sredzienski, D. Spencer, J.
Woodcock, "WGOTHIC Application to AP600", WCAP-14407, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION g: ==
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OITS 5397 RAI 480 974 (Page 1-3) The third bullet rnakes reference to "LASL." Should this reference be to Sandia?

===Response===
The text was corrected in Reference 480.974-1 to identify Sandia as the reviewer.
Reference 480.974 1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation. l l
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l   NRC REQUEST FOR ADDITIONAL INFORMATION e
R+.. ::a: i OITS 5398 RAI 480.975 (Pages 2-2 and 2-3) The table given here is very useful in locating where each phenomena is addressed. However, some of the n groups coutrJ not be found in Section 8, where n groups are evaluated. These are: n,,,,, n,.,,,, n,c3 and n,y. Also, listing " parameter" under n group does not give any information on where the phenomenon is addressed it would help to show which n group the parameter is in.

===Response===
The pi groups, n,,,, n,,,,,, n,y, and n,,,, were replaced in Table 21 of Reference 480.975 1 with defined pl groups. See the response to RAI 480.968.
The left column of Table 2-1 includes an extra subdivision that shows which phenomena the "parame-ters" are in. For example, Mixing and Stratification is one of several parameters in Condensation Mass Transfer.
Reference i
480.975-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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Rw      MI OITS 5399 l
RAl 480.976 (Page 2-3) No n group is listed for baffle conduction in Table 2-1. Why are n,,,, and      x,.,,  listed in Table 8 4 not appropriate for addressing this phenomenon?

===Response===
;   The baffle pi groups, n,,3, and x,.,w, listed in Table 8-4 represent sensible t) eat transfer to and from the baffle. Since the importance of baffle conduction must be similar to the importance of the fluxes in and out, the two groups were added to Table 2-1 of Reference 480.976-1.
Reference 480.976-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5400 RAI 480.977 (Pages 3-1 and 3 2) Values given for the volumes and surface areas of steel and steel-jacketed heat sinks are different from those given in (Phenomena identification and Ranking Table) PIRT (WCAP-14812) Table 31. Please explain.

===Response===
The heat sink surface areas and volumes listed in the PIRT, Table 3-1 (Reference 480.9771), are correct. The values used for scaling reduced the values in the PIRT for the following:
  .       All heat sinks were eliminated in dead-ended compartments, since steam access is not dependable.
* All upward facing concrete heat sinks were eliminated, since the concrete floors in all rooms may blanket with noncondensables, and/or thick water films that prevent heat transfer.
* All upward facing, horizontal steel heat sinks more than 2 ft wide were eliminated, since they may develop liquid films too thick to drain rapidly and permit efficient heat transfer.
The net effect of these reductions is to reduce the PIRT areas and volumes to the values presented in Table 3-1. This discussion was added to the text in Section 3.1 of Reference 480.977-2.
References 480.977-1 M. Loftus, D. Spencer, J. Woodcock, " Accident Specification and Phenomena Evaluation for AP600 Passive Containment Cooling System", WCAP-14812, Rev.1, Westinghouse Electric Corpora-tion.
480.977-2 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure Dunng Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION M
OITS 5401 RAI 480.978 (Page 3-3) Why is the third plateau in mass flow rate beyond 80,000 seconds not shown in Figure 3-1 as it is in PIRT (WCAP-14812) Figure 3-77 Is the correct flow rate beyond 80,000 seconds shown in the PIRT Figure?

===Response===
Reference 480.978-1 presents a revised Figure 3-1 that shows the external water flow rate to 7 days.
The figures in the PIRT (Reference 480.978-2) and the Scaling Analysis (Reference 480.978-1) are consistent.                                                                                         .
References 480.978-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2. Westinghouse Electric Corporation.
480.978 2 M. Loftus, D. Spencer, J. Woodcock, " Accident Specification and Phenomena Evaluation for AP600 Passive Containment Cooling System", WCAP-14812, Rev.1, Westinghouse Electric Corpora-tion.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5402 RAI 480.979 (Page 310) Please explain the decrease in pool surface area which occurs between 2,500 and 5,000 seconds shown in Figure 3-8.

===Response===
The pool surface area decreases at approximate y 2000 ft of pool volume as the rising surface encounters the bottom of the reactor vessel. The reactor vessel has a large cross section that reduces the pool area. Thereafter, the area only increases as additional compartments flood.
l 480.979-1 3 Westinghouse                                     ,

NRC REQUEST FOR ADDITIONAL INFORMATION                                                                      l 1
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1 OITS 5403 RAI 480.980 1
(Page 4-7, Section 4.3.2) What is the basis for the belief that the correlation for the air-steam diffusion coefficient produces values which are 10 percent high? Why is this acceptable?
Response:                                                                                                   l The Heat and Mass Transfer report, Reference 480.980-1, Section 2.6, shows a comparison of the air-steam diffusion coefficient with test data in the range of temperatures for AP600 containment analysis.
The comparison shows the correlation is 10% too high. The Heat and Mass Transfer report reference was added to the Scaling Analysis, Reference 480.980-2.
The 10% difference is acceptable because the correlation is used consistently for all data comparisons and AP600 predictions, and is biased in the evaluation model to bound the test data as shown in Reference 480.980-2, Section 4.5.
l References 480.980-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment             l Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation 480.980-2 F. Delose, D. Spencer, R. P. Ofstun, " Experimental Basis for the AP600 Containment               ,
Vessel Heat and Mass Transfer Correlations", WCAP 14326, Rev.1, Westinghouse Electric Corpora-tion.
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NRC REQUEST FOR ADDITIONAL INFORMATION ME EE OITS 5404 RAI 480.981 (Page 6-1, Section 6) The wording of the last sentence in this section could be modified to better convey the thought. It appears that you have adopted and adhered to a sign convention and this assures that the direction of heat flow is unambiguous and determined by the sign of the solution.
The paragraph was reworded to clarify the sign convention in Reference 480.981 1.
References 480.981-1 D. Spences, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment      1 Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION m
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OITS 5405 RAI 480.982 l
(Page 6-7) The statement that u m, can be defined which corresponds to the system with the specific internal energies of water and air at the same temperature and pressure needs further explanation.
The discussion of the reference temperature was expanded in Section 6.2, Reference 480.982-1.
Reference 480.982-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis ' Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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l    NRC REQUEST FOR ADDITIONAL INFORMATION i
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OITS 5406 RAI 480.983 (Page 6-7) It would be helpful to the reader to state that Equation (56) in the form:
dm ,,/dt = mg. - S m,,,,3 is used to obtain Equation (67).

===Response===
The discussion of the development of the energy equation was expanded in Section 6.2, Reference .
480.983-1, to include the use of Equation (56).
Reference 480.983-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5407 RAI 480.984 (Page 6-9) In Equation (69), the work term has been left out of the final equation, although a x group for the term is included. When the equation is used in Chapter 9, as Equations (191) and (197), this same term is also missing. Please explain.

===Response===
-   The work term for displacement of air by water was inadvertently left out of Equation (69). This term was included in Equation (69) of Reference 480.984-1.
The work term for displacement of air by water was inadvertently left out of Equations (191) and (197). ,
This term was included in Equations (191) and (197) of Reference 480.9841.                              I Reference 480.984-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
W westinghouse                                    ,

NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5408 RAI 480.985 (Page 616) In Table 6-3, it would be helpful to add the time period for each phase to the headings.

===Response===
The transient time was added to each time period in Reference 480.985-1, Table 6-3.
Reference 480.985 1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5409 RAI 480.986 (Page 618) According to the nomenclature section, p, in Equation (84) is the containment ambient density. How is this number calculated from the reference values given in Table 6-3? What phase of the DECLG LOCA (double ended cold leg guillotine loss-of-coolant-accident) is used to get the values in Table 6-47 How is the value determined for LST?

===Response===
The ambient density, p., in Equation (84) is equal to the total density, p, in Table 6-3.
The AP600 values in Table 6-4 are independent of the phase, with the exception of the ratio p/p, that varies only a few percent for the different time phases.
The LST values in Table 6-4 are independent of the test conditions, with the exception of the ratio pgp, that varies only a few percent for the different tests.
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NRC REQUEST FOR ADDITIONAL INFORMATION
!      OITS 5410 l      RAI 480.987 (Page 618) The criterion for stable stratification, based on the volumetric Froude number, does not include the diameter of the large volume within which the jet is released. This means that the criterion applies equally to a volume whose diameter is only slightly larger than the jet diameter, do, and to an infinitely large diameter volume. There must be some assumption in Peterson's approach which limits
;    ' the size of the applicable volume relative to the jet. Clearly, a jet located in an infinitely large volume l      does not affect the stratification of the entire volume. Please explain the limitations on the application
!      of Peterson's approach as the volume size increases.
I

===Response===
The stratification data referenced by Peterson were developed for large, shallow pools. For such a geometry, the pool width, W, is greater than the depth, H, and both are much greater than the jet l      diameter, do. Application of Peterson's results to AP600, with H/W = 1.0, approximately, is expected to overestimate the jet Reynolds number required to break up stable stratification. Consequently, following a large LOCA or MSLB, stratification may not appear until later (at lower break flow rate) than predicted. Use of Peterson's criteria for stable stratification is considered to be conservative for AP600                   1 analysis.
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NRC REQUEST FOR ADDITIONAL INFORMATION
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s' OITS 5411 RAI 480.988 (Page 6 22) Fr at the stability limit presented in Table 6-4 is stated to be calculated using Equation (89),
Fr = (1 + d/(4 V2 a H))'
Fr, = (1 + 11.1/(4 V2 0.05109))*
Fr, = 1.85 which doesn't agree with the number in the table. Please explain.

===Response===
The values of "Fr, at Stability Limit" were all corrected and presented in Reference 480.988-1.
Reference 480.988-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION l                                                                                                   is     .5
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OITS 5412                                                                                               ;
!     RAI 480.989                                                                                             l l
(Page 7-7, Section 7.1.1) A formula for the shell conductance is given just before Equation (96) which  i includes the coating on both sides. Later, on the bottom of Page 7-11, a formula for the conductance is l given without the coatings. Which formula was actually used?                                            I l

===Response===
The formula with coatings was used to define the value of h,no. The statement at the bottom of p 711 was corrected in Reference 480.989-1.                                                                   l l
Reference 480.989-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Acridents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION
                                                                                                    .: - - m 1-     g OITS 5413 RAI 480.990 (Page 7-13, Table 7-2) What is the reason for choosing the design pressure (60 psia) as "P" total for the long term phase? Would this not tend to overestimate the heat transfer to the heat sinks?

===Response===
it was desired to include the design pressure in the scaling analysis to avoid the concern that only nominal conditions, with their much lower pressures and transfer rates, might somehow produce less       1 severe results. The heat transfer to the heat sinks and shell are allincreased at higher pressure conditions, but the relative magnitude of each process is not believed to change significantly, i
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NRC REQUEST FOR ADDITIONAL INFORMATION mit iE!!
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i OITS 5414 RAI 480.991 (Page 713, Table 7-3) Why does the table not include the long term p5ase? Why is the pool surface area different for the blowdown and refill phases even though the pool volume is the same? Why is the   j surface area during refill different in Tables 7 2 and 7-37 Figure 3-8 shows a pool surface area of 2,000 fta compared to the 1,933 fta shown in this table. Which is correct?
I Response                                                                                                !
l The incomplete results in Table 7-3 and inconsistencies between Table 7-2, Table 7-3, and Figure 3-8 in Reference 480.991-1 were corrected in Reference 480.991-2, Section 7.2.2.
References 480.991 1 D. R. Spencer, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents" WCAP-14845, Rev. O, Westinghouse Electric Corporation.
l 480.991 2 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment         l Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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h NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5415 RAI 480.992 (Page 7-15) How was the film determined to be less than approximately 0.005 inches thick, as stated in the first paragraph. The arguments regarding the importance of the liquid illm are based on this assumption. How would the assumption of a thicker film affect the calculated heat transfer through the shell?

===Response===
Please see the response to RAI 480.1027 for a discussion of the basis for a 0.005 inch thick film.
The minimum Nusselt number produces a heat transfer coefficient value of approximately 600 B/hr-ft2, F, whereas a 0.005 in. film has an h of 900 Brnr ft'-F. When combined with the shell/ coating conduc-tance of 217 B/hr-fta -F and typical inside and outside mass transfer coefficients of 100 B/hr ft2 -F the difference between 900 and 600 B/hr-ft' F for the film coefficient changes the overall heat transfer coefficient from 37.3 to 35.8, a 4% difference. This difference is not significant for a scaling analysis.
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NRC REQUEST FOR ADDITIONAL INFORMATION m: E=:
OITS 5416 RAI 480.993 (Page 7-16) How was the 165 F area-weighted average film temperature cited in the first paragraph calculated?                                                                                            l

===Response===
The area weighted average film temperature was calculated using values from the spreadsheet that calculates numerical values for the scaling analysis. The film temperature for each of the steel, concrete, and Jacketed concrete surfaces was multiplied by the respective surface area and divided by the total surface area.                                                                             .
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NRC REQUEST FOR ADDITIONAL INFORMATION y .._
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OITS 5417 RAI 480.994 (Page 7-21, Section 7.5.5) In Section 3 (Page 3-1) and Section 4.7, steel heat sink thickness is given as 0.4 inches, while 0.5 inches is used here. Which is correct?
l

===Response===
!        The average steel heat sink thickness is 0.4 inches. The value 0.5 quoted in Section 7.5.5 was revised to 0.4 in Reference 480.994-1.
Reference 480.994-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment                     l Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.                     i l
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NRC REQUEST FOR ADDITIONAL INFORMATiON 1,,,    ;
i OITS 5418 RAI 480.995 (Page 7 21, Section 7.5.5) Using 25 B/hr-ft-F for the conductivity of carbon steel and the average steel thickness of 0.5 inches, indicates that an h of 48 B/hr ft'-F was used to get a Biot number of 0.08.
Apparently this is h,.. However, according to the values in Table 8-2, p., has an average value of about 0.4, indicating that h,,, is approximately 0.4 x 216.58 = 86.6 B/hr ft'-F. How was the value of 48 for h,, determined?

===Response===
The value of h,, ranges from 66 to 97 for the four time phases. Thus, k = 25 B/hr-ft-F and 6 = 0.4 in.
gives a maximum Biot number hS/k = 0.13. The text of Section 7.5.5, Reference 480.995-1 was revised accordingly.
Reference 480.995-1 D. Spencer, W. Brown, M. Roldt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
480.995-1
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OITS 5419 i   RAI 480.996 I
(Page 7-21, Section 7.5.5) Please explain in greater detail how the solution of Equation (118), given by Equation (126), was determined. In particular, what value was used for the containment atmosphere temperature and how was T,,, determined or related to Tn,7

===Response===
l   The text in Reference 480.996-1 was revised to note that since the heat sink Biot number is low, the heat sink is modeled as a lurr. ped mass, so T., = Tn ,. The containment atmosphere is modeled by the containment gas temperatures and times presented in Table 6-3. The solution given in Equation (126) assumes the gas temperature history is a linear function of time from one Table 6-3 temperature to the next.
Reference i
I 480.996 1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment               j Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.               ,
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I                                                                                                    .n OITS 5420 RAI 480.997 (Page 7-21, Section 7.5.6) It is stated that the containment boundary condition was modeled as a step function over each time phase. What constant value was used for each phase?

===Response===
The text in Reference 480.997-1 was revised to define the containment gas temperature history as the containrnent gas temperature values presented in Table 6-3.
Reference 480.997-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Ana!ysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION
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OITS 5421 '
RAI 480.998 (Page 7 22, Section 7.5.6) Were integrations performed to obtain the time averaged value of h,7 Please explain which equation (s) were integrated or how the average values were determined. Since the peak containment gas temperature is used for T , what is an estimate of the error in the overprediction of heat flux during the non-peak pressure phases? Where was Equation (128) used outside of containment? What temperature was used for T. outside of containment?

===Response===
Integrations were not performed. The value of h, calculated for each time phase was multiplied by the phase Alime, the products summed, and the sum divided by the total time. The result was the time-weighted heat transfer coefficient.
The contai.oment gas temperature (from Table 6-3) for g.ch time phase was used as T . This approximation resulted in a step change in the boundary temperature at the beginning of each time phase, and overestimated the heat fluxes. The magnitude of the overestimation is probably greder than a factor of 2 for the concrete heat sinks and chimney. Since the pi values for the concrete heat sinks and chimney are less than -0.12 in Table 8-4, the fact that heat flux is overpredicted by a factor of two or more means hte concrete is even less significant than indicated by the pl values.
Outside of containtnent, Equation 128 was used on the chimney concrete. The chimney gas tempera-ture was used for T..
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5422 RAI 480.999 l_
(Page 7-22, Section 7.b.7) It is stated that the modeling of two structures in parallel and taking the larger of the two is conservative for the steel-jacketed heat structures. This neglects the thermal resistance of the gap between the steel and the concrete, a factor considered in present evaluation models. Provide an estimate of the effect of the gap on your thermal model for the steel-jacketed heat sinks.
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===Response===
The effect of a gas filled gap between the steel Jacket and concrete can be estimated by considering the gap conductance in relationship to the concrete conductance. A 0.005 inch air gap has a conductance of 36 B/hr-ft'-F. It takes only 0.28 inches of concrete to equal this conductance. In terms of conductance, the structure with a 0.005 in, gas gap looks like a structure with no gap, but with 0.28 inches more of thermal penetration into the concrete. The extra 0.28 in. of concrete requires additional         l time to saturate, that can be estimated from the structure time constant,0.6S'pegk = 132 sec. Thus,              !
after a delay on the order of 132 sec. the structure with the gas gap will be conducting heat into the concrete at approximately the same rate as a heat sink with no gap.
!    Thus, a conceptual model of the heat sink with a gap will behave much like the heat sink with no gap initially, until the steel Jacket is saturated (approximately 1 minute). Conduction into the concrete with the gas gap then occurs at a rate similar to that in the solid heat sink after a time delay of just over 2 l    minutes. The effect on pi groups is expected to be minor during blowdown and refill, since the steel jacket dominates then. During the peak pressure phase the energy transfer is reduced. During the long term time phase the effect is small because the 132 see time delay is only a small part of the total time.
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NRC REQUEST FOR ADDITIONAL INFORMATION m    a:=  l E     g OITS 5423 RAI 480.1000 (Page 7-25) is Equation (134) based on treating the shell as a lumped mass? Please define the term T,n, (not in the nomenclature). Is T,n, assumed to be equal to T,n?
Response                                                                                                   l T,n is the shell average temperature, that represents the total heat stored in the shell. The surface temperatures were revised in Reference 480.10001 to be consistent with Figure 7-3 nomenclature.           i The shell is treated as a thermally thick structure as defined by Wulff (Reference 480.1000-2) and         l solved using Wulff's solution presented in Equations 152 to 155.                                          j l
References                                                                                                l 480.1000 1 D Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment           !
Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
480.1000-2 W. Wulff, " Integral Methods for Simulating Transient Conduction in Nuclear Reactor Components", Nuclear Engineering and Design 151 (1994) 113-129.
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NRC REQUEST FOR ADDITIONAL INFORMATION I
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!   OlTS 5424 RAI 480.1001 (Page 7-25, last paragraph) What calculation of the " temperature of the evaporating film independently of the subcooled or dry regions" is referred to here? Please describe the calculation.
l l   Response l   The text preceding equation 135 in Reference 480.1001-1 was revised for clarity, i
Reference 480.1001 1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION l
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      . (Page 7-25) Please explain the meaning of Equation (135). The numerator is the energy flow rate needed to heat the external film flow from T,, to T,,... One would expect the denominator to be the heat i
flux from the interior containment gas volume needed to heat the film flow over the area A,c. Based on the nomenclature section, the heat transfer coefficient h,,,,, is between the subcooled shell interior and
      ' the external film, but the temperature difference is between the film and the subcooled shell external surface, with the sign indicating that the film is expected to be at a higher temperature than the subcooled shell exterior surface. Please explain or correct the equation.

===Response===
The text preceding equation 135 in Reference 480.1002-1 was revised for clarity. The incorrect temperature difference in the denominator was also corrected.
Reference 480.1002-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION
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OITS 5426 RAI 480.1003 (Page 7-29, last paragraph of Section 7.6.3) The reader can not tell what the relative magnitudes of time coristants are from the equations in (140). It would be helpful to give the values to support the l          argument. Also, is the external heat transfer from the shell, rather than to the shell?

===Response===
The ratio of time constants for the inside and outside of the subcooled shell is equal to the ratio of the l                                                                                                                               )
heat transfer coefficients, or T ,/t,, = h . /h.. ,,. The ratio of the heat transfer coefficients is equal to the ratio of the norrnalized conductances presented in Table 8-2, so the ratio of time constants is t,,/T,,
           = x,.,/n, , = 0.58/3.88 = 0.15.
External heat transfer is from the shell to the subcooled liquid outside the shell.
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OITS 5427 RAI 480.1004                                                                                                         l (Page 7-30, Section 7.6.5) Which equation from Wulff is used to get the 22-second penetration time?
If this is your Equation (151), this should be noted. What is the difference between this 22-second penetration time and the 18.4 seconds on page 7-317 l
l      Response l
l      Equation (151) of Reference 480.10041 was used to calculate the thermal penetration time for the                     ,
j      shell. The value is 18.8 sec. and the text was revised to quote the correct value in two places and                  )
Equation (151) was referenced.
Reference 480.1004 1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment                      i l      Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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i NRC REQUEST FOR ADDITIONAL INFORMATION l                                                                                                    w     ..=
OITS 5428 RAI 480.1005 (Page 7-30, Section 7.6.5) Please explain how you apply the adiabatic boundary condition at the outer shell surface during blowdown when you are using the thermally thick structure model. The last sentence of the first paragraph of Section 7.6.5 implies that this is being done if the thermally thick structure is used for the entire blowdown period, please provide an estimate of the non-conservatism htroduced by this approximation.

===Response===
The text in Section 7.6.5 was revised in Reference 480.1005-1 to state that the shell is modeled with dry external heat transfer (not adiabatic) until the water appears below the second weir.
Reference 480.1005-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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i NRC REQUEST FOR ADDITIONAL INFORMATION pm   .wr itti  it l
l   OITS 5429 l   RAI 480.1006 l
(Page 7-31) In Equation (152), it seems that (in Wulff's notation) g, and g2 are taken as 1/2 when they should be 1/3.

===Response===
Equation (152) was corrected in Reference 480.1006-1. The values of gamma cancel out in the development of Equations 154 and 155, that are used to calculate pi values,'so this error does not affect any pi values.
Reference 480.1006-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.         i l
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I NRC REQUEST FOR ADDITIONAL INFORMATION i
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i OITS 5430 RAI 480.1007 (Page 7-32, Section 7.6.5) Equation (153) is incorrect. The equation dDdt = C, C,T given in the line below Equation (153) is correct with C, and C, as defined in (155).                                               l 1
T(to) = T is o an initial condition for this ordinary differential equation, not a boundary condition. Please l
       ' correct.
Response                                                                                                          ;
Equation (153) was corrected in Reference 480.1007-1 and the initial condition was defined.                       l
       ' Reference                                                                                                         i I
480.1007 1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, V/estinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5431 RAI 480.1008 (Page 7-33, second paragraph) The wetted area below the second weir is given as 44662 ft'.
Actually, this is the total area below the second weir (52662 8000 = 44662). The 90 percent wetted area fraction has not been applied below the second weir. The maximum wetted area is also then incorrect. Is the shell area below the operating deck included in the total area? If so, please provide justification.

===Response===
The maximum wetted area below the second *. sir was corrected in Reference 480.1008-1 to be 0.9 x 44662 = 40196 ft'. The calculations were revised consistent with this change. The shell heat transfer to the PCS is limited to the above-deck region.
Reference 480.1008-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION                                                                      l i
OITS 5432                                                                                                   l RAI 480.1009                                                                                                l (Page 7-33, second and third paragraphs) Why is 60 lbm/sec used for the flow rate in the second paragraph and 40 lbm/sec in the third paragraph?
60 lbm/sec is applied by the PCS, whereas the stability model (Reference 480.1009-1, Figure 711)            l shows that at 90% coverage, at the time of peak pressure, less than 20 lbm/sec runs off the shell. The difference is the 40 lbm/sec that evaporates. The flow that evaporates carries away most of the heat, but the full applied flow is important for subcooled heat capacity.
i Reference 480.1009-1 A. Forgie, J. Narula, R. Ofstun, D. Paulsen, S. Slabaugh, M. Sredzienski, D. Spencer, J.
Woodcock, "WGOTHIC Application to AP600', WCAP-14407, Westinghouse Electric Corporation.                    )
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5433 RAI 480.1010 (Page 7-35, Section 7.7, second paragraph) What is the magnitude of the Biot number for the baffle,           ,
and what h is used in the Biot number for this two-sided heat structure? Radiation heat transfer on the outside of the baffle is using the downcomer temperature as the sink temperature, is it assumed that the shield building and downcomer temperatures are equal?

===Response===
The highest baffle Biot number for time phases after refill is:
h6/k = 11 B/hr-ft -F 0.125 in/(26 B/hr-ft-F 12 in/ft) = 0.0044 This Biot number was calculated using the maximum h on the baffle inside. The result of the calculation was added to the Reference 480.1010-1, Section 7.7 discussion.
l It is assumed the shield building to downcomer heat transfer coefficient is very high, so any energy deposited in the shield building inner surface is transferred to the downcomer air with negligible temperature difference. The intent is to maximize the energy transfer to the downcomer air, and simultaneously, to maximize the negative buoyancy of the downcomer air.
Reference 480.1010-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corpor:: tion.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5434 RAI 480.1011 (Page 7-36) Following Equation (158), it is stated that the downcomer operates in opposed mixed convection; however, Equation (158) lists a forced convection heat transfer coefficient for the baffle to the downcomer. Please explain.

===Response===
The text following Equation 158 was revised in Reference 480.1011-1 to stat'e that both the riser and downcomer operate predominantly in forced convection, consistent with the results shown in Figure 4-1.
Reference 480.1011-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
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l NRC REQUEST FOR ADDITIONAL INFORMATION                                                                 i i
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OITS 5435 RAI 480.1012 (Page 7-37) Equation (164) appears to be missing the term "+ hm ,,,3," in the numerator of the expres-sion for "b." Please correct or explain.

===Response===
Equation (164) was truncated in printing. It was corrected in Reference 480.1012-1, Reference 480.1012-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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l NRC REQUEST FOR ADDITIONAL INFORMATION I
OITS 5436 RAI 480.1013 I    (Page 7-38, Section 7.7.4) In an earlier section, the notation "i" was used to represent average temperature, in Equation (166), it appears that this notation is now used to represent a/b. Also, is "T" in Equation (166) the same as T,in Equation (165)? Please clarify in the text.
l l    Response The character i in Equation (166) confuses the discussion and was deleted in Reference 480.1013-1.
Minor changes were made to the text to clarify the discussion.
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Reference 480.1013-1 D. Spencer, W. Brown, M. Roldt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION l     OITS 5437 RAI 480.1014 (Page 7-38, Section 7.8) It would seem that the air in the downcomer could be heated by convection from the baffle and, in turn, heat the shield building wall by convection. Justify your conjectare that dry forced convection heat transfer is to the downcomer from the shield building wall.

===Response===
The downcomer air can transfer heat to the shield if the temperature difference is in the right direction.
With heat transfer from the baffle to the shield, or from the downcomer to the shield the resulting downcomer air temperature will be less than calculated in the scaling analysis. For the scaling analysis it was assumed the radiation to the shield was deposited directly in the downcomer, which maximizes the downcomer temperature. Since the energy transfer rates are low enough that energy transfer rates are small, the effect on momentum is the important concern, so that concern was maximized.
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!                                                                                                   I     g OITS 5438 RAI 480.1015 (Pages 7-38 and 7-39) The description of the analysis in Section 7.9 must be improved. First, the terms need to be clearly defined; What is T , the chimney concrete average temperature? Later in Section 7.9.4 it is stated that the chimney is treated as a thermally thick structure; so this lumped equation would not apply for the concrete? What is the difference between T and T,..,, and T ,,7 Equation (167) indicates parallel mass transfer and convection plus series conduction across a film I between two chimney temperatures T, and T .,,,7 The n groups in Section 7.9.3, indicate energy transfer between several different temperatures, including T,,, (which needs to be clearly defined). This carries over to Equation (172) where it is unclear as to what the temperature difference T,, T,,
represents. Please explain and include a discussion of what variables are calculated and how they are used in the scaling analysis.                                                                             ,

===Response===
Equations (167) and (168) were revised in Reference 480.1015-1 to correct errors. Additional text and definitions were added for clarity.
Summarizing the changes, four temperatures are defined and used:
  .        T is the chimney gas temperature. The riser subscript, ri, in Equation (172) was corrected to ch for chimney gas.
  .        T,is the average chimney concrete temperature, used to calculate the rate of change of the chimney stored energy,
  .        T,,,is the chimney surface temperature that interacts with the average temperature, T , by Wulff's equations for thermally thick structures, Equations (127), (128), and (129),
  .        T,, is the chimney liquid film surface temperature. This is the temperature that interacts with the chimney gas. Conduction through the film carries energy into the concrete from the gas.
Reference 480.1015-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION MEMEs y    :u OITS 5439
:   RAI 480.1016 (Page 81) In Table 8-1 state which heat structures are included for each phase; e.g. do they include above the operating deck plus circulating compartments? How does this compare to what is used in the WGOTHIC model?

===Response===
Section 3 of Reference 480.1016-1 was revised to define the basis for the heat sink volume and surface areas used for the LOCA and MSLB. The text in Section 8.1 was revised to refer the reader to Section 3.
Reference 480.1016-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845 Rev. 2, Westinghouse Electric Corporation.
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OITS 5440 RAI 480.1017 i
(Page 8-2, Table 8-2) The anomalous value obtained for n,, for the long term phase is indicative of a problem in the approach used to combine conductances between different locations into a single conductance. The basic message is that conductances are only meaningful when combined in either series or parallel between the same locations. Other conductances calculated in the same manner as ne ,y include x,,, and n,.... Provide values for all n groups (which were calculated using the above approach) leaving out the term with the temperature difference so that any additional anomalies can be identified.

===Response===
The detailed conductance calculations are presented in Westinghouse prcprietary calculation note CN-CRA-96120 that was reviewed by the NRC.
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l l    OITS 5441 RAl 480.1018 l
l    (Page S-2, Table 8-2) Please provide a more detailed explanation of why the pool conductance is            l I    extremely low during refill compared to the other phases. The numerator of the pool conductance            !
l    n group, x,, is evaluated using Equation (105). The only parameters which could cause such a low
,    value appear to be either DP,,or Dr/r. For either DP,, or Dr/r to have a low value, the partial pressure   i l    (or the density) of steam in the bulk containment would have to be very close to the value at the pool     !
surface. What assumption is made which gives a low value when there is no break source?                    l l ,

===Response===
l With no break source providing a saturated source of liquid, the pool surface is near thermal and pressure equilibrium with the atmosphere. Only the relatively slow rate of change of the gas tempera-      l ture and pressure during the refill phase continue to cause some heat and mass transfer. However, the rate is much reduced as noted.
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I NRC REQUEST FOR ADDITIONAL INFORMATION
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    ,                                                                                               ?     g CITS 5442 RAI 480.1019 (Page 8-3, Section 8.2) The statement regarding external conductance on the evaporating shell at the time of peak containment pressure seems to refer to the values of conductances during the long term phase. This is confusi.1g since there is also a peak pressure phase. Please clarify the discussion.

===Response===
The text was revised in Reference 480.1019-1 to replace the confusing reference to the time of peak containment pressure with the long term phase.
Reference 480.1019 1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5443 RAI 480.1020 in the tables presented in Section n it is stated that a shaded entry indicates a value greater than 10 percent. Please verify the values. For example, no,, in Table 8 3 and x,,,t,, in Table 8.5, under "Long Term" are -0.02.

===Response===
The shadings were deleted in Reference 480.1020-1.
Reference 480.1020-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION 7, ""a OITS 5444 RAI 480.1021 4
(Page 9-6) The first paragraph indicates that a simultaneous solution was obtained for eight named variables. Presumably the eight governing equations are the 3 mass conservation equations (173), the three energy conservation equations (175), the momentum equation (176) and the buoyancy equation (179). However, n groups are given in Table 9-1 only for the momentum equation (with a time constant from one of the mass conservation equations), indicating that perhaps a more simplified procedure was used. Please explain in more detail why only one equation is needed to scal,e the PCS air flow. Also, due to the coupling of the buoyancy pressure drop to the heat tcansfer, one would expect an iterative solution to be necessary. Was iteration required in the approach used?
Response                                                                                                I
-                                                                                                              1 An iterative solution was required. The buoyant air flow rate results from equating the buoyant forces  l and drag forces in the air flow path. The buoyancy results from the density-elevation distribution through the air flow path and is affected by heat and mass transfer between the air flow path and the baffle, dry shell, evaporating shell, and chimney. The mass and energy fluxes are not strongly coupled to the air flow rate, so the iteration was simple and converged rapidly.
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NFiC REQUEST FOR ADDITIONAL INFORMATION
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OITS 5445 RAI 480.1022 (Page 9-9, Table 9-1) Please explain why the buoyancy and friction x group values are not equal for the peak pressure and long term phases. According to the statement in the second paragraph of Section 9.3.1, the reference mass flow rate comes from the reference buoyancy term and the reference buoyancy is the steady-state solution of the momentum equation. This statement implies that the x group values should be the same.
l Response                                                                                                        !
The coupled, iterative solution for the PCS air flow was solved as described in the response to RAI 480.1021, using dimensional equations. The solution increased the PCS air flow by the evaporated (or             l condensed) steam and used the net (air plus steam) flow to calculate the density and resistance pressure drna in each of the downcomer, riser, and chimney flow paths. The dimensionless resistance              l pi group, in contrast, is defined only in terms of the air flow rata (not including the steam flow rates), so gives a low value of scaled resistance when the steam flow rates are significant. Steam flow rates are significant during the peak pressure and long term time phases, h0nce the resistance pi values less than 1.0 for these time phases.
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OITS 5446                                                                                                     1 RAI 480.1023                                                                                                   1
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(Page 10-7, Section 10.1.2) The text describing Figure 10-2 refers to LST data while the figure refers         l to the STC Flat Plate Test. Which is correct?                                                                 )
i Respoine                                                                                                      I l
The text in Reference 480.1023-1 was revised to state the Westinghouse flat plato data are used in Figure 10-2, not LST data.
i                                                                                                                         i l           Reference 480.1023 1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION m=ussm OITS 5447 RAI 480.1024 (Page 1011, middle paragraph) The Reynolds number at the time of peak containment pressure, 163,000 from Table 9-1, is for the long term phase rather than the peak pressure phase. Please clarify the discussion so that there is no ambiguity as to what number was intended to be used.

===Response===
The text was changed in Reference 480.10241 to clarify the time phase reference to Table 9-1.
Reference 480.1024-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
480.1024-1 T westingh0use                                     .
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NRC REQUEST FOR ADDITIONAL INFORMATION iEE UiE OITS 5448 RAI 480.1025 (Page 10-12, Section 10.1.6) Several terms in Eqt:4 tic n (196) have not been defined, or as is the case for o, are defined in the nomenclature differently thra n used here. Either here or in the nomenclature all terms should be unambiguously defined.

===Response===
All terms in Equations (196) were defined in Nomenclature in Reference 480.1025-1.
Reference 1
480.1025-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment            l Pressure During Design easis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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OITS 5449 RAI 480.1026 (Page 10-13, Table 10-7) The film Reynolds number for the AP600 upper sidewall given in Table 10-3 is more than a factor of 2 greater than the highest value for either the L ST or the water distribution test.
An even higher value of 4,000 is givsn as the upper range for AP600 in Figure 10-3. Ju;iD' your statement that the range of AP600 operation is adequately covered by the test data.

===Response===
The Chun and Seban (Reference 480.1026-1) and Kutateladze, et.,al. (Reference 480.1026-2) tes' . ;ta     .
show as the water Reynolds number increases above 4000 the Nusselt number also increases. Since the Nusselt number increases with Reynolds number, the film heat transfer coefficient also increases.
Consequently, higher Reynolds numbers are not a concem. See also the response to RAI 480.1027.
References 480.1026-1 K. R. Chun and R. A. Seban, " Heat Transfer to Evaporating Liquid Films," Joumal o/ Hoat Transfer, November 1971.
480.1026-2 S. S. Kutateladze, l.1. Gogonin, N. l. Grigor'eva, A. R. Dorokhov, " Determination of Heat Transfer Coefficient with Film Condensation of Stationary Vapor on a Vertical Surface", Thermal Engineering, 27 (4),1980.
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OITS 5450 RAI 480.1027 (Page 1013, Section 10.1.7) How does the film thickness in the Wisconsin and Chun and Seban data compare to the 0.005-inch thick liquid film assumed in the scaling model?                                     l

===Response===
Most experimenters do not attempt to measure the thickness of the wavy laminar or turbulent films that occur over the range of Reynolds numbers characteristic of AP600 films. It is easier and more useful to measure, or infer from other measurements, the film heat transfer coefficient. The film heat transfer      ;
coefficient was determined by Chun and Seban (Reference 480.1027-1), and by Westinghouse with the             l Wisconsin data (Reference 480.1027-2). Since the characteristic length used for film analysis is the property (v"/g)"', knowing the actual, time varying film thickness is unnecessary. However, given a heat transfer coefficient, an " effective" film thickness can easily be calculated from the simple relation-ship 6 = k/h. For water and a typical h of 900 B/hr-ft'-F,6 = 0.005 in.                                       j The heat transfer coefficients on the outside of AP600 can be ranged by considering the maximum value of T at the spring line, assuming 60 lbm/sec and 90% coverage, T = 0.163 lbm/ft-sec, Re =               l 2600, so h is approximately 700 B/hr ft2-F. At the bottom of the side wall, assuming the maximum              l evaporation rate of 40 lbm/sec,20 lbm/sec runs off, so r = 0.054 lbm/ft sec, Re = 867, and h is               i approximately 944 B/hr-ft2-F. Thus, on the outside of AP600 h ranges fror.) 700 to 944 with an average of 822 B/hr ft2-F. The corresponding " effective film thickness" is 0.0055 h.
Inside the AP600 containment shell the film flow will range from 0 at the t.'p to approximately 40            i Ibm /sec at the bottom, since the net condensation is approximately equa'. to the net evaporatior             l Consequently, the heat transfer coefficient inside will have a higher average value than on the om         e, with a thinner effertive film thickness.
The Chun and Seban data cover a Reynolds number range of 300 to 20,000. The Wisconsin data extend the range down to 30. Consequently, the data cover the expected range of AP600 Reynolds numbers and Nusselt numbers (and also " effective film thicknesses" if one cares to calculats them).
  , The above calculations also support the use of an effective film thickness of 0.005 in.
Kutateladze (Reference 480.1027-3) presents Nusselt number measurements for refrigerant-12 (Prandtl number approximately 4) over a Reynolds number range of 10 to 2000 that show similar trend but higher minimum Nusselt number than the Chun and Seban data.
Mudawar (References 480.1027-4 and 480.1027-5) measured the thickness of wavy-laminar propylene glycol / water mixtures and of turbulent water films. Their measured film thicknesses could be compared to the Nusselt smooth laminar film thickness, or to the effective fitn thickness.
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NRC REQUEST FOR ADDITIONAL INFORMATION
     .e-    m E       g References 480.1027 1 K. R. Chun and R. A. Seban, " Heat Transfer to Evaporating Liquid Films," Joumal of Heat Transfer, November 1971.
480.1027-2 WCAP-13307, " Condensation in the Presence of a Noncondensable Gas Experimental Investigation," Westinghouse Electric Corporation.
  . 480.1027-3 S. S. Kutateladze, I. l. Gogonin, N. l. Grigor'eva, A. R. Dorokhov, " Determination of Heat Transfer Coefficient with Film Condensation of Stationary Vapor on a Vertical Surface', Thermal Engineering
     , 27 (4),1980.
480.1027-4 1. Mudawar and R. A. Houpt, " Measurement of Mass and Moment'im Transport in Wavy-Laminar Falling Liquid Films", intemational Joumal of Heat and Mass Transfer,101. 36, No.17, pp 4151 4162,1993.
480.1027-5 J. A. Shmerler and I. Mudawar, " Local Evaporative Heat Transfer Coefficients in Turbulent Free-Falling Liquid Films", Intemational Journal of Heat and Mass Transfer, Vol. 31, No. 4, pp 731-742, 1988.
no.1027-2                                                                           W westinghouse l
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l NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5451                                                                                                      l RAI 480.1028 (Page 1016) In Figure 10-4, clarify the location labeled "above." is this all heat sinks above the operating deck? Also, please explain the very rapid heat absorption in the core makeup tank (CMT) room and add a curve showing heat rejection to the annulus.

===Response===
-   In Figure 10-4 the location labelled "Above" includes all the above-deck heat sinks, except the shell.
The CMT room contains more than half of allinternal heat sinks. During blowdown the rapid pressur-ization of the steam generator compartment forces steam directly into the adjacent compartments, including the CMT roum. The resulting steam-rich mixture lasts 27 seconds and produces heat transfer rates significantly greater than calculated in the well-mixed scaling analysis, hence the apparent time constant on the order of 20 seconds.
The purpose of Figure 10-4 is to show energy removal rates from the containment atmosphere corresponding to different regions. The energy rejection to the riser does not represent energy removal        ,
from the containment gas, so is not shown. However, according to the pl groups, by 1500 sec. the               j energy out of the shell is equal to the energy into the shell.
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480.1028-1 W Westinghouse                                       ,
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NRC REQUEST FOR ADDITIONAL INFORMATION
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OITS 5452 RAl 480.1029 (Page 1017, Section 10.2.1.1) In order to obtain the information for comparison of the n groups inside containment, it was necessary to calculate the state outside the vessel as noted on the bottom of Page 10-17. The scaling of evaporative cooling on the outside of containment is also a high ranked phenomena to which the LST scaling should be applicable, with the buoyancy pressure drop replaced by the forced flow pressure drop. Include an evaluation of the mass and energy n values for the LST air flow path outside containment.

===Response===
The last three rows of Table 10-3 represent the normalized values of sensible heat transfer from the shell to the riser, n ,,no, heat transfer from the shell to the subcooled water, x,,,,, and evaporation heat transfer from the film to the riser, n,.,,... These three pi groups are the significant energy transfer groups outside. containment.
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OITS 5453 RAI 480.1030 (Page 1018, Section 10.2.1.2) The transient validation of the dP/dT equation is useful to the extent that it shows that the gas compressibility for air is being treated correctly in the scaling equations. The validation against LST steady-state test data in Section 10.2.1.1 shows that the scaling handles the inside containment shell heat transfer in a reasonabla way. Ideally, the scaling equations should be integrated and compared to transient scaled test data to validate the entire model. In the case of AP600, such transient test data do not exist. In lieu of this, the staff has prev.iously suggested that Westinghouse integrate the scaling equations for AP600 (as was done in WCAP-14190) to show that reasonable results are obtained. Given that the scaling equations predict a negative rate of pressure change for refill and beyond, as shown in Section 10.0, one need not integrate the scaling equations to conclude that the results will not compare well to WGOTHIC predictions. Westinghouse cites conservatisms in the WGOTHIC model (for example, use of Uchida and biases in shell heat and mass transfer models) as the suspected cause for the differences between the scaling model results and computer code best estimate predictions. Nevertheless, such significant differences raise concems regarding the value of the scaling study as an indicator of the magnitude and importance of individual processes, in particular, have any of the phenomena been modeled non-conservatively in the scaling analysis?
The rate of pressure change scaling result is counterintuitive. From the x values in Table 10-5, the rate of pressure change at the start of the peak pressure phase is barely increasing, even when heat transfer to the shell is ignored. Neglecting the shell, the total n value on the right side of the equation l is 1.03 1.02 = 0.01. When the shell is ignored, the AP-600 is similar to an existing plant (with no         I containment wall heat sink). Intuitively, based upon present plant containment analyses and testing, one would not expect the pressure to increase only during the relatively short blowdown period, and         l I
remain essentially constant immediately thereafter, especially when the containment wall heat sink is ignored. For the present generation of large dry containments, analyses show that the pressure turns I
around only when the sprays are activated. It is difficult to accept that the structural heat sinks alone, with the entire shell ignored, are sufficient to essentially stop the pressure increase.
Westinghouse should convincingly demonstrate that the scaling analysis does not model the heat sinks in a non conservative fashion.

===Response===
The results presented in Section 10 of Reference 480.1030-1 were revised and are presented in a new Section 8.6 c' Reference 480.1030-2. The revised results compare predictions of the scaling model and a comptrable WGOTHIC case, Case 6 of Reference 480.1030-3, Chapter 5. The comparisons show the two models predict similar trends, and similar rates of pressure change.
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References 480.1030-1 D. R. Spencer, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents" WCAP-14845, Rev. O, Westinghouse Electric Corporation.                                   l l
480.1030-2 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment    i Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
l 480.1030-3 A. Forgie, J. Narula, R. Ofstun, D. Paulsen, S. Slabaugh, M. Sredzienski, D. Spencer, J.
Woodcock, "WGOTHIC Application to AP600", WCAP-14407, Westinghouse Electric Corporation.
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l OITS 5454 RAI 480.1031                                                                                                l l
l (Page 10-21) What is the difference between the x values given in Table 10-10 for AP600 and those           l given in Table 10-47 Following the convention established in the earlier sections, the last 6 rows of x     l values in Table 10-10 would generally be negative. To what value does the footnote in Table 10-10           l apply?

===Response===
The pi values presented in Table 1010 of Reference 480.1031-1 were calculated according to the          .
same definitions as those in Table 10-4. The difference is that the values in Table 10-10 are for a steady state, and at a different containment pressure than the values in Table 10-4.
The last 6 rows of pi values all represent energy transfer out, or negative values following the convention. However, for simplicity, they are presented without the negative sign in Reference              j 480.1031-2, Table 10-3.                                                                                     ,
l The footnotes in Table 10-3, Reference 480.1031-2, were revised.                                            l Reference 480.1031-1 D. R. Spencer," Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. O, Westinghouse Electric Corporation.
480.1031 2 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5455 RAI 480.1032 (Page 11 1) Please provide a definition of distortion. This is essential in order to clarify how the evaluations in the third column of Table 11-1 were developed.

===Response===
A definition for distortion was added to the beginning of Section 11 in Reference 480.1032-1. The third column of Table 11-1 was deleted and distortion was instead discussed for each difference in the text.
Reference 480.1032 1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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OITS 5456 RAI 480.1033 (Page 11-2) One potential distortion not addressed is the non-prototypical scaled thickness of the shell.
l        This item should also be addressed.

===Response===
l The shell thickness was added as a difference and evaluated in Section 11.1 of Reference 480.1033-1 References                                                                                                       l l
480.1031-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5457 RAI 480.1034 (Page 11-4) The LST feature " External Water Flow too High" is evaluated from the viewpoint that a range covering AP600, from no flow to very high flow was tested. The aspect that is not addressed is the larger amount of heat removed by the subcooled liquid in LST. This difference should also be l
addressed.
l Response                                                                    .
The discussion of " External Water Flow too High" in Reference 480.10341 was revised to include the following points:
* The energy and pressure scaling pi groups for the subcooled shell presented in Reference           j 480.10341, Tables 8-4,8-5, and 10-3 all show subcooled heat transfer effects are second-order phenomena. Consequently any distortions in the test are not significant to the system         i response.
1
    .       The results cf scaling test 213.1C presented in Table 10-3 show the measured value of x,,,. is     i less than the calculated value for AP600. Consequently, the concern over the " larger amount        l of heat removed by the subcooled liquid in LST" is not valid.                                       I 1
Note that in Reference 480.1034-1, the text reference to Figure 10-10 should be to Figure 10-3.
Reference 480.1034:1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
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OITS 5458                                                                                                  )
l RAI 480.1035 l                                                                                                               \
!    (Page 11-5) Under " External water flow oscillations," it is stated that the data were evaluated using     i both the maximum and minimum flow rates. The evaluation does not appear to be in this scaling              ;
report. A reference to the eva'uation needs to be included.
    'A reference to the WGOTHIC Application report, (Reference 480.1035-1) Appendix 7.A was added to the discussion of flow oscillations in Reference 480.1035 2 Reference 480.1035-1 A. Forgie, J. Narula, R. Ofstun, D. Paulsen, S. Slabaugh, M. Sredzienski, D. Spencer, J.
Woodcock, "WGOTHIC Application to AP600', WCAP 14407, Westinghouse Electric Corporation.
480.1035 2 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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t OITS 5459 RAI 480.1036 (Page 121) The bullet under item 1 refers to a non-existent Table 8-6. Please correct the reference.
Also, considerable quantitative information has been developed which should be used for closure with the PIRT. The cursory statement in item 2 should be expanded to discuss x values for the high and l   medium ranked PIRT phenomena.

===Response===
The conclusions were extensively revised in f3eference 480.1036-1, Section 12.
The it#crence to Table 8-6 was corrected.                                                            ,
The PIRT-scaling closure is covered in the PIRT (Reference 480.1036 2).
References 480.1036 1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
480.1036-2 M. Loftus, D. Spencer, J. Woodcock, " Accident Specification and Phenomena Evaluation for AP600 Passive Containment Cooling System", WCAP-14812, Rev.1, Westinghouse Electric Corporation.
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(     3 Westinghouse                                                                                         .
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OITS 5252 RAI 480.1017 The report must be organized in a scrutable manner and the pertinent information must be clearly and unambiguously presented. In each section the premise on which the analysis is based needs to be stated and followed through in a logical manner to the conclusion. In its present form, the report is disjointed and lacks focus. Westinghouse should clearly state: (1) the purpose of each section, and (2) how the material supports the conclusions of the work. The key item is the pressure rate of change equation. Westinghouse must provide this equation in its final form, together with the x groups, in a single location.
1 Response                                                                                                             i The revised scaling report, Reference 480.1017-1, is separated into three major parts: Part 1 -                      l Executive Summary, Part 11 - PIRT Confirmation, and Part ill - Separate Effects and Integral Test                    i Scaling, in addition, each major section starts with a paragraph that explains the goal of the work in               l the section.
The system-level pressure rate of change used for scaling the LST is presented in Section 10.2 with each pl group clearly defined.
Reference 480.1017-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation,                      i l
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OITS 5253 RAI 480.1018 There are three related, and critical, items which must be addressed in order to establish that the               ]
Westinghouse approach is applicable at the scale of the AP600.                                                     I
: 1.      The Westinghouse scaling approach does not address the issue that tt 9 heat flux in the large             i scale tett (LST) facility is too high and that the rate of pressure drop is too high by a factor of       ]
eight whea compared to the AP600. The issue is that Westinghouse did not divide through by l             the coefficient on the dP/dt term (e.g., Equation (7) on Page xvii of WCAP 14845) in the j             pressure rate of change equation. The key variable of concern, in simple terms, is hAN, where             ,
h is the heat transfer coefficient, A is the surface area for brat transfer and V is the contain.         1
;             ment volume. The governing equations show that this heat flux (O = hA) to volume ratio is the             )
key quantity that must be preserved, similar to the " power-to-volume" ratio that is used to scale        i primary system experimental facilities. With the 1/8 linear scaling of the LST, (hAN)tst = 8 (hAN)%. Thus this key top level scaling criteria is not met. This needs to be addressed as a              i l
major distortion of the LST, and the scaling analysis needs to be revised to include this item in         l the correct manner.
l The distortion caused by the difference in hAN (or QN) between the AP600 and the LST is                    I operative in the steady-state and the transient mode. The scaling approach can either divide              l l             through by this term, which appears on the left side of the pressure rate of change equation, or          )
the scaling approach can define a dimensionless time and incorporate the term into the rate of            j l
l             change. This is what is done in the Westinghouse analysis. The scaling is then such that                  j l             dimensionless time proceeds eight times faster in the LST than in the AP600, or looked at it in           i another way, the heat removal rate per unit volume is eight times higher. it cannot be argued             I that the LST is steady-state and therefore that time is irrelevant. Even in the steady-state the          )
mixing, diffusion and condensation processes inside the containment volume and at the shell                l surface are rate dependent. Data from larger scale facilities is likely to be needed to address            I this distortion.                                                                                           l
: 2.      Scaling of mixing (circulation) and thermal stratification must be addressed. Data from international test programs, to supplement the LST data, will likely be needed to establish the           i
,             applicability of the evaluation model at the AP600 scale. Data from HDR, Grenoble, and l             Japanese tests were identified as potentially being applicable to address this concern.
: 3.      The distribution of noncondensibles is a function of scale. Westinghouse must establish the scaling for the distribution of noncondensibles as they affect condensation heat transfer. Data from HDR, Grenoble, and Japanese tests were also identified as potentially being applicable to address this concem.
,                                                                                                       480.1018-1 l        T Westinghouse

NRC REQUEST FOR ADDITIONAL. INFORMATION

===Response===
: 1. The Westinghouse LST scaling presented in Reference 480.10181, Section 10.2 develops pi groups, each of which represents the ratio of a specific, normalized transport process in the LST to the same process in AP600. The pi groups show the power-to volume ratio in the LST divided by the power-to-volume ratio in AP600 is important, as is the power-to-area ratio in the LST divided by the power-to-area ratio in AP600. The magnitude of this ratio was evaluated and the deviation from perfect scaling are discussed.
2,3. Westinghouse recognizes that the evaluation model can not predict the thermal, velocity, and air / steam density fields observed in the LST. Neither is the evaluation model expected to correctly predict the thermal, velocity, and air / steam density fields within AP600 containment.
Furthermore, because of non-prototypic features of the LST, the fields observed in the LST are not believed to represent fields in AP600. Westinghouse does not believe it useful to attempt to substantiate WGOTHIC evaluation model predictions of thermal, velocity, ard concentration fields inside containment, using either the LST or Intemational tests.
Rather, Westinghouse is pursuing a bounding approach to predict the transport rates that depend on field properties inside containment. In the bounding approach, the transport rates are calculated using models that are biased so as to maximize containment pressure. Rather than attempting to justify the fields predicted by the evaluation model, the LST intemal field data are considered with results from both smaller scale and larger scale (international tests) to develop methods for bounding the effects of circulation and stratification in addition, sensitivi-ties are performed to a range of postulated circulation patterns and a limiting scenario for containment pressure calculations is defined in Reference 480.1018-1.
The pressure rate of change equation shows the pressure in AP600 results from the difference between the heat and mass inputs and the heat and mass outflows. A conservatively predicted pressure occurs if the following are satisfied:
           .         The gas volume is minimized,
           .         The heat and mass flow rates in are upper bounded, and
           .         The heat and mass flow rates out are lower bounded.
The Westinghouse evaluation model does these three, thus the model predicts conservatively high pressure. At every time step throughout the transient these are satisfied.
Reference 480.1018-1     D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP 14845, Rev. 2, Westinghouse Electric Corporation.
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                                                                                                    $i     3 OITS 5254 RAI 480.1019 Westinghouse has included drops dispersed into the containment atmosphere during blowdown as a heat sink or heat source in the scaling equations. In the study, the drops are assumed to remain in the atmosphere for all of the double ended cold leg guillotine loss of-coolant-accident (DECLG LOCA) phases. This is non physical. The surface area used for the drops is an arbitrary number. While Westinghouse has argued that the scaling analysis shows that the drops do not have a significant effect, it is recommended that the drops not be included. A thermodynamic equilibrium model is suggested as being more appropriate, as a simpler and acceptable approach. At a minimum, a better discussion of why drops were considered and what conclusions can be drawn from their consideration needs to be provided at the beginning of the section.

===Response===
The discussion of drops presented in Section 7.1, Reference 480.1019-1 notes that the drop analysis concludes that equilibrium between the drops and the containment atmosphere h the expected result, and h modeled as such during all time phases. The result shows drops have only a minor effect on containment pressurization.
l The discussion of the break liquid and pool in Section 7.2, Reference 480.1019-1, notes that equilibrium     l between the liquid and containment atmosphere is the expected result for blowdown, and is modeled as such during blowdown. After blowdown, a rate-limited maximum evaporation rate is calculated. The calculations show the pool has only a minor effect on containment pressurization, both during and after blowdown.
Reference 480.1019-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5255 RAI 480.1020 Section 11, on the identification and evaluation of distortions, needs to be supplemented with informa-tion which indicates how the distortions are handled when using the LST data to validate the evaluation model. This may include pointers to the PIRT (WCAP 14812) and application (WCAP-14407) reports, as appropriate.
  . Response Section 11 was revised extensively in Reference 480.1020-1 to better address distortions and how they are handled in the evaluation model validation.                                                         .
Reference 480.1020-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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NRC REQUEST FOR ADDITIONAL INFORMATION OITS 5256 RAI 480.1021 The " Conclusions" section of the report, Section 12, must directly and concisely state how Westing-     !
house uses the results of the scaling work. In particular,
: 1.       Explain what use is made of the LST data for the WGOTHIC computer program validation and how does the scaling study support this usage;
: 2.       Explain how the scaling study used to support the PIRT evaluation
* and
: 3.       Explain how the scaling study used to support the use of the various models and correlations in WGOTHIC at the scale of AP600.

===Response===
The use of the scaling study to support the use of the LST data for the WGOTHIC computer program validation, the WGOTHIC models and correlations, and the PIRT evaluation are discussed in the conclusion, Reference 480.1021-1, Section 12.                                                            <
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,     Reference 480.1021-1 D. Spencer, W. Brown, M. Roidt, J. Woodcock, " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents", WCAP-14845, Rev. 2, Westinghouse Electric Corporation.
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