NSD-NRC-97-5338, Documents Resolution of PCS PIRT & Scaling Issues Discussed During 970916 Meeting Between NRC & Westinghouse.Responses to Issues Reviewed & Agreed at Meeting,Encl

Documents Resolution of PCS PIRT & Scaling Issues Discussed During 970916 Meeting Between NRC & Westinghouse.Responses to Issues Reviewed & Agreed at Meeting,Encl

ML20217B594
Person / Time
Site:	05200003
Issue date:	09/22/1997
From:	Mcintyre B WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:	Quay T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NSD-NRC-97-5338, NUDOCS 9709300080
Download: ML20217B594 (26)

Text

_ _ _

94

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Westinghouse Energy Systems

-Ba 355 Electric Corporation Pinsburgh Pennsylvania 15230-0355 DCP/NRC1047 NSD-NRC-97-5338 Docket No.: 52 003 September 22,1997 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: T.R. QUAY

SUBJECT:

AP600 PCS PIRT/ SCALING CLOSURE MEETING

SUMMARY

l-

Dear Mr. Quay:

This letter documents the resolution of PCS PIRT and Scaling issues discussed during the.

NRC/ Westinghouse meeting in Rockville on September 16,1997. Enclosed are the responses to the PCS PIRT and Scaling issues that were reviewed and agreed to at the meeting. We will prepare a schedule for providing the information identified in our responses following the Septembec 29-30 ACRS Meeting

- Please contact Bruce Rarig on (412) 374-4358 if you have any questions concerning this submittal.

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Brian A. McIntyre, Manager 1

Advanced Plant Safety and Licensing jml-Enclosure cc:

D. C. Scaletti, NRC (w/ Enclosure)

N, J. Liparuto, Westinghouse (w/o Enclosure)

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4 ENCLOSURE TO WESTINGIIOUSE LETTER DCP/NRC1047 l

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PCS PIRT/ SCALING CLOSURE MEETING

SUMMARY

- WCAP 14326 Rev l." Experimental Basis for the AP600 Containment He and Mass Transfer Correlations" 1.

RAI 480.358: What is the potential significance of the " dense screens"?

Response: NSD NRC-96-4850 October 17, 1996: "It is assumed that the dense screens were installed to breakup the velocity profile at the entrance of the heated channel. In this way, both the temperature and velocity profiles would desclop simultaneously."

The response is not consistent with Eckert/Diaguila paper. The reference paper states: "To assure that the air entered the tube proper with a constant velocity, dense screens were installed at the top and bottom of the tube."

i Neither is addressed in Rev.I.

RESPONSE

The text in WCAP-14326, Rev. I will be revised to correctly state the purpose of the screens.

2.

In section 4.4.4 Open Literature Tests, it is stated that: " Uncertainties in the Hugot(II) Eckert and Diaguita(6), Siegel and Norris(19), Gilliland and Sherwood(23), and Chun and Seban(7) tests are discussed in the open literature references."

The staff finds no discussions of the uncertainty in the data in any of the referenced papers (except minimally in the Gilliland and Sherwood paper) reviewed (staff has not reviewed the Hugot work). Papers assess correlations fits to a scatter of data without addressing the significance of the scatter in the data.

RESPONSE

WCAP-14326 will be revised to state that information on uncertainties is limited to what is provided in the reference papers.

3.

Section 2.2.1 is based on a three foot wide well? Is this a mistake? If not, then show a plant (SSAR) 3 disgram. Ifit is really 4.5 feet, how can any conclusion be drawn concerning the competing effects?

RESPONSE

The three foot wide well shown in Figure 2.14 is a tristake, the figure and associated text will be corrected to 4.5 ft. The competing effects in the annulus are based on a 6 ft height to the bottom of the bafile (for free convection) and a 2 ft hycraulic diameter for the riser annulus above the bottom of the baffle. Thus the effect of the error is limited to the figure and does not affect the calculations.

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e 4.

References for analyses are to WCAP-14407 for WGOTillC code. (e g., page 3 23) Were analyses done with V 4.0 (4.1) or 1.x7 Were analyses re-done? Should they be re-done? Are the "ccvel" cl.anges significant?

j

RESPONSE

WGOTHIC version 1.2 was used for the analyses presented in WCAP 14326, Rev.1.

The analyses wcre not re-done using WGOTHIC version 4.1. The analyses need not be redane since the junction inertia length input values were adjusted in the WGOTHIC version 1.2 calculations to yield cell centered velocities equal to the average of the incoming and exiting junction velocities for each lumped parameter volume in the channel. Consequently, the change in subroutine ccvel(from WGOTHIC version 1.2 to version 4.1) was effectively implemented by the input for these calculations.

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5.

Figure 3.6 2 (pg. 3-47) X axis not labeled (Reynolds Number).

Was correctly labeled in Rev 0.

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RESPONSE

WCAP 14326, Rev. I will be revised to add the x axis label,"Reynolds Number".

6.

Page 3 63. LST 222.4 (not stated if part a or part b). Reference is the original LST data report, kne 1994.

Test values revised in April 1997 update. If wrong data used, how can any conclusion be drawn concerning the model selection (amount of conservatism)?

RESPONSE

Data for LST 222.3 A and B and for LST 222.4 A and B are included in Figure 3.9 5. Note at each elevation there are two tests (222.3-RC064 and 222.4 RC066) and for each test there are two data points (A and B).

WCAP 14326 will be revised to update the reference to the April 1997 LST data report.

The heat transfer, mass transfer, or liquid film data used in WCAP 14326, were consistent with internal errata issued in 1994. The April 1997 revision to WCAP 14135 were redundant relative to the data used in WCAP-14326.

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Consider error bars on Figure 3.9-4. Consider Section 4.5 method to bound data, llow can an assessment qf the amount of conservatism be made? May be conservative but not bounding, cannot " quantify."

RESPONSE

The text discussing the condensation data in WCAP 14326, Section 4.5 will be revised to state that the correlation is conservative rnther than bounding.

4 i

8.

The values presented in Section 4.5 relating to the application of the condensation test data are not consistent with the information provided in letter NTD NRC 9570, dated September 28,1995. Also on page 4 17, third line from bottom, word " evaporating" should be " condensing."

RESPONSE

WCAP 14326, Rev. I supersedes NTD NRC-9570.

WCAP 14326 will be revised to change the word " evaporating" to " condensing".

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WCAP-14845 Rev 2. " Scaling Analysis for AP600 Containment Pressure During Design Basis Accidents" Page E 5:

The data table, w hich supports statement on validation of equation, is no longer part of the report.

Was Table 10-8. Section 10.2.1.1.

RESPONSE

The second bullet on pg. E-5 refers to the mean deviation ofless than 0.01 and the standard deviation of l

0.i3 which were provided in Table 10-8 of WCAP 14845, Rev. 0. This table was deleted from the revised j

scaling report because the information in the table was not needed to support the results of the top-down system level scaling described in Part til of the revised report. The second bullet on page E 5 is an accurate statement that is supported by a Westinghouse calculation note. Descriptive text and the information from Table 10-8 (from WCAP 14845, Rev. 0) will be added as a new appendix.

Reference to this new appendix will be added to the second bullet on page E-5.

l Page E-8:

The'is no Figure 11 1. Is it 10-57

RESPONSE

Figure 11 1 should be Figure 10-5. The Scaling Analysis document will be revised to change the references to Figure 11 1 on pages E-8 and 12 3 to Figure 10 5.

j Page E-8:

Last paragraph. Where and what is the support, code version (1.x,4.x), models (LP,DP, errors),

etc.? In what section (sections) can this material be found?

RESPONSE

WCAP 14845 will be revised to define the Evaluation Model by reference to WCAP 14407, Rev 1, Section 4.

Page P-2:

Thought GOTHIC was selected but needed additional model for the clime. WGOTHIC was result ofeffort.

RESPONSE

The sentence in question will be revised to state that GOTHIC was selected as the best available tool. The third paragraph under " Element I" will also be revised.

Page P-4:

LST ref. is.old June 1994 report. April 1997 revisit..ndicates potential for bad analyses if based on original.'

RESPONSE

The test data used in the Scaling Analysis are all consistent with the April 1997 issue of WCAP-14135

- Rev.1.

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. Page P-6:

Distributed parameter model? Role and status, is there a summary or which sections describe use of this model?

RESPONSE

The reference to the distributed parameter model will be removed from WCAP 14845, page P-6.

l-Page I 5:

Ref. to Ref. 47 Should be Ref. 5. Section 9 of 4 is not to be reviewed.

RESPONSE

l Yes, Reference 4 should be Reference 5. WCAP 14845 will be revised to refer to Reference 5.

I l

l Page 2-l ?

What is the mixing and stratification report? Section 9 of WCAP 144077

RESPONSE

Yes. WCAP-14845 will be revised to change " mixing and stratification report" to Reference 5, Section 9.

Page 8 3:

There is no shading visible on Table 8 3, or any other table (8-4 and 8 5), to indicate > 10%.

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RESPONSE

WCAP 14845 will be revised to correct the discrepancy. The shading will be added to the tables, Page 10-5:

2%, is it non conservative?

RESPONSE

WCAP 14845 will be revised to note that the Colbum correlation used for AP600 predicts 2% higher heat transfer coefficients than does Dittus Boelter, or Seider-Tate. The Colburn correlation differs little, but is 2% less conservative than the attematives.

Page 11-6:

There is no Table 10-10. Table 10 37

RESPONSE

Yes, WCAP 14845 will be resised to change Table 1010 (2 places) to Table 10-3.

Westinghouse has prepared AP600 Response to Requests for Additional Information as an enclosure to letter NSD-i NRC-97.$216 of June 27,1997. The majority of the responses appear to be acceptable. However, comments and I

clarifications apply to the following RAls:

1.

(RAI 480.975) Pi-groups pi.gJ and pi,r, r have not been replaced in Table 2 1 as stated in the response p

e Please clarify w here numencal values for these pi-groups can be found.

RESPONSE

The subscript "p.gj" should be p,qJ, which indicates a pressure pi group, p, for sensible (radiation plu*

convection) heat transfer, q, from heat sink j. J is an index that represents the heat sinks listed in Table 7 1, Values of n,qj are presented for each time phase in Table 8 5. WCAP 14845 will be revised to correct j

p this subscript error in Table 2 1.

1 WCAP 14845 will be revised to replace the group n,r, t y n,rj and n,q,ssx to be consistent with Note I b

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e to Table 2-1, 2.

(RAI 480.995) In the previous revision of the scaling report, the Biot number had been calculated to be 0.08. Now it has been recalculated as 0.13. According to Kreith, Principles of Heat Transfer",3rd ed., p.

140, a criterion for treating a heat structure as a lumped mass is that the Biot number be less than 0.1.

Since Kreith's criteria is no longer satisfied, what is the justification for lumping the steel? What is the estimated magnitude of the error introduced by this approximation?

RESPONSE

Kreith's Biot criteria Bi < 0.I, is based on a temperature error ofless than 5%. It is estimated that Bi < 0.13 would give a temperature error ofless than 10%. Such an error is considered acceptable for a scaling analysis in view of the simplicity of the lumped parameter assumption.

Westinghouse will review the use of Biot number and the discussion provided in the Heat & Mass Transfer Report, the PIRT, and the Application Report. Text will be updated as needed for consistency and clarification.

3.

(RAI 480.1002) There still appears to be a problem with the nomenclature in equation 135 and in the equation on the second line of page 7 30. Why is it necessary to change the temperature subscripts in going between these two equations? Also, the subscript " sex"(not in the nomenclature section or in Figure 7 3)is not defined.

RESPONSE

WCAP 14845 will be revised to replace the undefined subscripts se and scx with the defined subscripts ss and ssx. That will correct the inconsistency in ;.ation 135 and the equation on the second line.

4.

(RAI 480.1011) The stated revision to the text does not appear to have been made.

RESPONSE

WCAP 14845 will be revised to state that the riser and downcomer both operate m forced convection, consistent with Figure 4 l.

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5.

(RAI 480.1017) He RAI was directed toward determining whether any of the remaining pi-group values c.ontained an anomaly similar to that for pi,br. The NRC review did not check the value of every pi.

c group. Please provide an evaluation of the anomaly effect for pi,dsx and pi,e3x.

ie e

RESPONSE

Although the pi value may appear anomalous, the temperature and heat transfer rate calculations ar:

correct. The individual heat transfer cocmcients and the corresponding temperature differences for the bame inside, the dry shell outside, and the evaporating shell outside are presented in Table 1. De values show the convection and radiation heat transfer coemcients range from 1.5 to 2.7, a reasonable range.

When multiplied by the corresponding AT the heat transfer rate is also reasonable. However, when the small negative riser-to-bame temperature difference is used to normalize the bame heat transfer rate the anomaly appears. The anomaly only appears in the bame equation since the evaporating and dry shell ATs are all relatisely large values.

The selection of a different normalizin; temperature difference would change the apparent anomaly for the l

bame, but would not change the resulting temperatures and heat fluxes. Or, as stated in RAI 480.1017, expressing the energy equation in terms of the riser-bame and shell bame temperature differences instead of only the riser-bame temperature difference would also eliminate the anomaly.

Table 1 - Temperature Differences and IIcat Transfer Coemelents for the Shell and Bame l

Evaporating Shell Dry Shell Bame Evaporation Energy h.esx = 126.6 h,ri-bf =0 m

m Transfer aTxf ri = 41.62 AT ' Sf 0.04 r

Convection Heat h,e3x = 2.73 h,d3x = 2.67 h

or =2.47 e

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Transfer AT ri = 41.62 AT sx ri = 113.21 AT -bf =-0.04 xf d

ri Radiation Heat h,esx= 1.50 h,dsx = 1,78 h,shx bf = 1.60 r

r r

Transfer AT -bt= 41.58 ATxt.bf = 113.17 ATshx bf = 41.59 xf Liquid Film lleat h g-840 x

Transfer ATxf bf-6.49 Westinghouse will remove this discussion from the Scaling Report, and replace with a statement that the pl value is unimportant, with the engineering basis for this conclusion, and why the anomalous behavior occurs at this location only.

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6. -

(RAI 480.1026) Why does increasine. heat transfer coefficient with increasing Reynolds Number imply that there is no concern?

RESPONSE

Our understanding of the concerns expressed in the RAI are that the test data range does not cover the AP600 range, and that the heat transfer coefficient may misbehave at higher Reynolds numbers. He Chun and Seban data cover Reynolds numbers up to 20.000, or approximately 5 times higner than the highest AP600 Reynolds num%r, so it is clear the data cover the AP600 range. The test data show the Nusselt number and heat transfer coefficient continue to increase uniformly as the Reynolds number increases, and that the correlation models the data. Consequently it is highly unlikely that the minimum heat transfer coctficient value has been missed.

7.

(RAI 480.1027) In addition to the information in the RAI, the following is needed to complete the review.

Please compare the physical film thickness (as predicted by the Nusselt equation) to the Chun and Seban effective film thickness over the range of Reynolds Numbers expected for AP600 (both inside and outside the PCS, above and below the second weir). For each Reynolds number, compare the heat transfer coefficient for the water film using the Nusselt model to the Chun and Seban model, ne wording in the first paragraph of Section 7.4 has been improved to distinguish the effective film thickness from the physical film thickness. Unfortunately, in the second paragrroh, the effective film thickness is used to get the heat capacity of the film, whereas the physical thickness should be used. The difference in the ratio calculated is not significant, but it confuses the issue, in the sense that it encourages the reader to thing of the effective thickness as a physical distance.

RESPONSE

The Nusselt equation models the smooth laminar film flow that exists for Olm Reynolds numbers less than

30. Consequently it is not appropriate to apply the Nus3elt correlation to wavy laminar and turbulent film flows. The result of misapplying the Nusselt smooth laminar film correlation to higher Reynolds numbers is to predict a thicker film with lower heat transfer coefficient than given by the Chun and Seban correlation.

Since the heat capacity of the liquid film depends on the mass ofliquid, a measure of the average film thickness is needed to estimate the volume and resulting mass. The effective thickness, determined from the film heat transfer coefficient correlation, is a reasonable measure of the average thickness. In light of the small value of the estimated heat capacity, and the transient energy storage, a more rigorous measure of the average film thickness is not required.

Westinghouse will add Kutataladze data to Figure 10-3 of the Scaling Report to provide further basis for the nominal Chun and Seban correlation, in addition, further justification in the text will be provided. This willinclude a discussion of the distinction between physical and effective film thickness. Westinghouse will also perform a sensitivity calculation varying film thickness to confirm the Low ranking of this phenomenon.

8.

(RAI 480.1031) In Table 10-3 the new footnote reveals that for LST, measured air / steam concentrations were used since LST is not homogeneous.. How wer : air steam concentrations for AP-600 determined for use m calculating the pi group values?

RESPONSE

The AP600 air / steam concentrations were determined from the Scaling Model, that assumes the total mass of gas is well mixed. Westinghouse will add a reference to Appendix 9.C of the WGOTHIC neimm u 8

e Application Report and also include a summary of the hand calculation results related to stratification gradient.

9.

(RAI 480.1032) ne de6nition of distortion provided appears to be appropriate for phenomena which are quantined by pi-groups. However, some phenomena, such as mixing and strati 6 cation are not represented by pi-groups. A broadct definition of distortion appears to be needed to cover phenomenon not quantified by pi-groups.

RESPONSE

Westinghouse has used conventions and dennitions from the literature as guidance for the containment pressure scaling analysis. The literature typically dennes distortion in terms of pi groups, so there is no known convention for defining distortion for groups that appear as parameters in pi groups, rather than as pigroups.

10.

(RAI 480.1035) Reference to the WGOTHIC Application Report, Appendix 7.A, which you state was added could not be found. De reference citation should appear in the section titled " External Water Flow Time Variations" on page 117.

RESPONSE

WCAP 14845 will be revised to include a reference to WCAP 14407, Rev.1. Section 7.6.3, that includes the maximum and minimum Sim now rate values, and the uses for the values. (Since RAI 480.1035 was written WCAP 14407 was revised.)

II.

(RAI 480.1036) De conclusions still appear to be somewhat disjoint from the main body of the report.

For example, the discussion in item I would seem to be supported more by the Applications Report than this Scaling Report,

RESPONSE

The discussion in Conclusion item I identines the high and medium ranked phenomena that were con 0rmed by the scaling analysis. The conclusions also provide information from WCAP 14326 and WCAP-14407 that tells how the phenomena are conservatively modeled. Westinghouse will add summary statements for ecch of the referenced sections.

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WCAP-14812 Rev 1," Accident Specification and Phenomena Evaluation for AP600 Passive Containment Cooling System" Tne following comments consider Westinghouse response to discussion items that were raised concerning WCAP-14811, Rev,0, the earlier version of the PIRT report, and how these are addressed in WCAP 14812, Rev.1, I.

Time phases in Table 4 1 are not consistent with the scaling repon, WCAP 14845, Rev. 2 (Table 6-3).

RESPONSE

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The time phase ditTerence results from the selection of different times for the peak pressure in the PIRT and in the scaling analysis. The time for the P!RT peak pressure was defined from the SSAR LOCA transient. The time for the scaling analysis peak pressure was selected for a fictitious transient that produced a peak pressure equal to the design pressure. He latter case produced an upper limit for the scaling analysis.

2.

Here still seems to be inconsistencies in the ranking of phenomena between the PIRT and scaling reports.

For example, break source item I E droplet / liquid flashing is rated low for all accident phases but still appears in the list of medium and high ranked phenomena in Table 2 1 of the scaling report.

RESPONSE

The PIRT is the source document for ranking. The scaling analysis WCAP-14845, Table 2 1 will be revised to delete items from the column labeled " phenomenon" that are ranked Low for all phases of LOCA and MSLB. The items to be deleted are: IE) droplet / liquid flashing,3A) Liquid Film Energy Transport, SF) Break Pool Compartment Filling (flooding level),7A) Convection from Containment, and

78) Radiation from Containment.

3.

In Appendix A, Westinghouse has now at least identified the experts by name, but still hasn't identified opinions and positions with an expert, so that the reader cannot tell who held w hat opinion. Also, source documents, such as written materials trom the experts, are not included. He value of the expert judgments is reduced considerably by the lack ofinformation in this area.

RESPONSE

Westinghouse has considered the comments of the NRC, the ACRS, and the experts on source identification and believes the PIRT embodies the best balance. Source documents related to the expert review are available for NRC review at Westinghouse.

4.

Pg. 2 3: The following sentence is unclear:

Such active systems *ih current PWRs lead to somewhat different thennal hydraulic conditions in AP600, so that AP600 specific verification was needed.

Suggest rephrasing the sentence with something like:

The absence of such active systems lead to somewhat..

RESPONSE

The text in WCAP 14812 will be revised to clarify the sentence.

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4 5.

Pg. 2.10-4: Scaling has been used to confirm the PIRT ranking (Ref. 2 Section 11) and to specify the applicaule data from the PCS Large Scale Test (Ref. 2, Section 111) for separate effects correlation validation and WGOTHIC code validation.

The same test data may have been used for both:

a) deriving bounding correlations and b) for WGOTHIC code validation.

Multiple uses of the same data source may lead to circular arguments. Please discuss the procedures Westinghouse used to maintained the integrity of the validation studies.

RESPONSE

The same test can be used for both without introducing circular logic. For example, correlations for the mass transfer rate and for water coverage were determined from the LST data and validated without use of the code. The models were built into, or input to the code, and it was verified that the code gave the same mass transfer rate and coverage predictions. This is not circular. The code was then used to predict pressure in the LST and compared to measurements. Since the individual models and the pressure calculations use independent data, the logic is not circular.

l 6.

Pg. 2-4: Westinghouse states that the integral LST facility included a representation of the AP600 in*ernals.

Although the LST intemals did not represent inter-compartment flow paths, data from LST have been considered in addressing stratification since the LST test matrix addressed a range ofimposed boundary conditions. Does this limit the LST data applicability to stratification only?

RESPONSE

No, it limits the LST to use as separate effects test data and as integral effects that do not include similarity of internal circulation.

7.

Pg. 2-9: Section 2.2.7 LST, States:

Long term heat and mass transfer test data for a geometrically similar model of the AP600 containment sessel.. determining the relative importance of various parameter that affect heat and mass transfer on both inside/outside containment surfaces.

What does relative importance means? What is the measure?

RESPONSE

The sentence will be revised something like ". for determining the sensitivity of the heat and mass transfer rates inside and outside containment to various parameters."

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8.

Pg. 2 11: In the LST, a diffuser was located under a simulated steam generator compartment below operating deck (LOCA simulated). Steam rose in a plume, and air was entrained in the rising plume resulting in a natural circulation Cow pattern within the simulated containment.

Iloweser, a diffuser under a simulated SG compartment' in LST does not provide anything close to real break simulation (LOCA blowdown). liow can a plume develo9 cr an unconfined SG7 LST lacks a f

second SG-compartment, therefore flows and entrainment are atypical of AP600.

RESPONSE

The paragraph that precedes the subject paragraph states "The LST did not simulate the blowdown phase of the LOCA or MSLB transients." The text in the subject paragraph will be revised to state that the diffuser simulated the break location of a LOCA.

Pg. 2 11 : Section 2.3 : Scaling Analysis 9.

Last paragraph, Westinghouse states :

l In Reference 2, Sect. lit, top-down scaling is used to determine the most impmant system level phenomena during blowdown and long-term phases of a large break LOCA transient and to sl tow how well those phenomena are preserved between LST and the AP600 plant. The results of this analysis are used to l

deter nine to what extent global containment data (pressure) can be used from LST for WGOTHIC code validation. This contradicts the statements in Section 2.2.7 stating the LST did not simulate the blowdown phase.

RESPONSE

Section 2.2.7 of WCAP 14812, Rev.1 (3rd paragraph) will be revised. He sentence, "He LST did not simulate the blowdown phase of the LOCA and MSLB transients." will Se deleted, ne last sentence of the paragraph will be revised to read, "LST tests were performed over a range ofinitial and boundary conditions to assess the impact on heat and mass transfer rates, and to provide a sufficient history of thermodynamic conditions to adequately simulate the quasi-steady long term cooling phase of an AP600 transient."

The last paragraph of WCAP 14845, Rev. 2, Section 10.2.1.3 provides further clarification of the use of LST data during the blowdown phase of the transient.

Pg. 3 5 : Sect. 3.2.1 Inside Containment 10.

He break source definition (For what break? LOCA? MSLB?) is not detailed enough as it only relates to the blowdown phase. He water drops suspended in the steam initially flash a staall fraction of their mass to steam to reach thewal equilibrium within the containment atmosphere.

RESPONSE

Sections 3.2.1,3.2.2, and 3.2.3 are brief, general descriptions of the two major regions (inside and outside) that are separated by the shell. It is not intended to be detailed, but rather, to encompass both LOCA and MSLB transients. The details of the Evaluation Model are presented in WCAP 1407, Rev.1, Section 4.

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o 11.

After flashing, the large surfacc area of these many tiny water drops maintains the atmosphere at or n-ar saturation for up to thousands of seconds. Westinghouse needs to provide references and experimental evidence.

' RESPONSE:

The scenario in question was postulated as an extreme (drops may very well not persist for more than a few 10's of seconds) that is analyzed to determine how significant an effect drops can have, bath drop thermal and momentum effects. The outcome of the analysis is that both effects are ranked low for all time phases.

Therefore, the effects of real drops are no more important than these hypothetical drops.

12.

' All compartments below-deck are provided with top openings to minimize the potential for a dead pocket of noncondensible concentration. Ilowever, this is not applicable for higher up break positions for steel

- jacketed concrete (explanation missing). The break liquid which is not dispersed as drops is assumed to leave the break at the containment saturation pressure.

i

RESPONSE

I Break liquid not dispersed as drops is addressed in Section 4.4.lE (PIRT).

The geometry of the internal heat sinks above the operating deck is also designed to minimize the potential

- for dead pockets of noncondensibles.

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Additional agenda items:

'l a f.:

Lollus, M.: Spencer, D.: Woodcock, J., " Accident Specification and Phenomena Evaluation for AP600 Passive Containment Cooling System," WCAP 14812, Rev.1. June 1997 The following general observations, issues and comments are provided concerning WCAP-14812, Rev. I:

1)

The current PIRT-report is not code-independent but rather merges PIRTs, WGOTillC Evaluation Model aspects and uncertainty issues in one and the same document. This should be reflected in the title of the l

report.

COAIAIEAT i

l THE COAfAIENTIS NOTED AND ACKNOWLEDGED THAT BOTH WGOTHIC, ASPECTS OF THE EVALUATION Af0 DEL AND CERTAIN ELEAILY15 OF UNCERTAIN 7Y ISSUES ARE DISCUSSED'IN THE CURREhTPIRT REPORT. THE PRIAIARY FOCUS OF THE CURREAT PIRT DOCUAIEATIS TO PRESEAT AND DISCUSS THE PIRT. IT IS NOTED THAT WGOTHIC, THE EVALUATION Af0 DEL AND UNCERTAINTY ISSUES ARE DISCUSSED TO THE L\\ TENT THEY SUPPORT DEVELOFAfEhT AND UNDERSTANDING OF THEPIRT. THUS.

THE TITLE OF THE DOCUAfENT IS INDICATIVE OF ITS COATEhT AND NO CH4NGE IN THF TLE OF THE CURRENT PIRT REPORTIS PL4NNED.

2)

The ranking rationale as displayed on pg. 4 20 deviates from P!RT guidelines as ;t list' '<oth energy transfer process and contamment pressure. The chosen wording opens many avenues tur ambiguity and speculation. Ifit is decided to really keep two objective functions, namely " energy transfer process" and

" containment pressure reduction" then the items in the ranking rationale should correctly read " increase in energy transfer" and resultant " containment pressure reduction." This could be also reconciled by eliminating the word " reduction."

COMAIENT:

CONTAINAIENT PRESSURE WAS THE PREFEMED FIGURE OF AfERIT USED FOR THE PIRT. HOWEVER.

CONTAINMENT PRESSURE IS MEANINGFUL ONLY FOR PARAMETER! OEFINED INSIDE THE CONTAINMENT SHELL FOR PARAMETERS CONSIDERED EATERNAL.TO THE LMTAINMENT SHELL, THE ENERGY TRA ASFER PROCESS WAS USED AS THE FK1CRE OF MERIT. THE TEAT WILL BE AMENDED TO CL4RIFY THIS.

P54tA M *l* CLO% A8 14

3)

Although the tsnking rationale encompasses both energy transfer process and containment pressure, the texc. references and arguments for the individual phenomenon in the main body of the report refers to the containment pressure only for the majority of them because this is the only figure of merit for which results have been provided.

CDsntEAT:

CONTAIXstEAT PRESSURE WAS THE PREFERRED FIGURE OF AtERIT USED FOR ME PIRT. HOWEVER, COATAIA AILNT PRESSURE IS AILANINGFUL FOR PARAAIETERS DEFINED INSIDE THE COATAINAIEAT SHELL FOR PAK4AIETERS CONSIDERED EATERNAL 10 THE COATAINAIENT SHELL THE ENERGY TRANSFER PROCESS WAS USED AS THE FIGURE OF AIERIT, 4)

Westinghouse has applied the bounding methodology for High-ranked phenomena, such as for instance for the most important energy transfer processes: condensation and evaporation inside and outside the containment, respectively, rather than as recommended for the Low ranked phenomena.

COAntENT; THE APPROACH TAKEN BY WESTINGHOUSE TRL415 f.0W-K4NKED PHENOAIENA IN A CONSERVATIVE A14NNER NO CH4%GE 10 THIS CONSERVA TIVE TRL4 TAIEhTOF LOW-RANKED PHENOAIENA IS PL4NNED, 5)

The basis for PIRT ranking is not based on experimental evidence (even for High-ranked phenomena) as would be expected. Rather, the majority of PIRT-ranking is based on scaling calculations, done using a special code with a simple model of the containment.

l COAntLv).

I AS DESCRIBED IN HIE DOCUAIENT, THE BASIS FOR THE PIRT IS HISTOR] CAL LYPERIAIENTAL DATA WHERE AVAIL 4BLE, HISTORICAL CALCUL4TIONS, AND LYPERT OPINION. THE DATA. ANALYSES AND LYPERT OPlV10% USED TO DEVELOP THE PIRT ARE DESCRIBED UNDER THE TITLE, " BASIS FOR PIRT RA AKIAG. " GIVEN FOR EACH PHENOAIENA LISTED IN THE PIRT, BRIEF DESCRIPTIONS OF TESTS USED FOR DEVELOPAIENT OF THE PIRT ARE GIVEN IN SECTION U OF THE DOCUAIENT, EXPERT OPINION USED lh DEVELOPAtEAT OF THE PIRT IS GIVEN Lv APPENDLY A OF THE DOCUAfENT. OPTIAIAL USE OF A VAIL 4BLE LYPERIAIENTAL DATA WAS AIADE IN DEVELOPING THE PIRT.

6)

Although the majority of PIRT-rankings is based on the results of scaling considerations and expert review, Westinghouse did not specify criteria for the numerical values for the PI-ratios for which the importance of a phenomenon would be ranked differently although they have essentially the same values for tite P'-ratios.

This leads to a non-uniform rankmg, rationale and resultant confusion.

CostAIENT:

WESTINGHOUSE TO PROVIDE RESPONSE.

m m.m nonu 15

c 7)-

Westinghouse has evaluated the PI-ratios at the beginning of a time phase. Some physical quantities drastically change over the time phas: but this change was not evaluated. Therefore, the numerical PI-ratio evaluated at the beginning of the next time phase, for instance, refill, results in a very much different (higher) value. In some cases, Westinghouse noticed and commented on these discrepancies. Ilowever for the majority of phenomenon the low predicted PI ratios were taken at face value and the phenomenon ranked " Low" for this time phase without any further considerations. This uneven approach leads to a number of ambiguities and concerns.

COstAIENT:

IF A PI-GROUP WAS RA TED EITHER "HIGH" OF "AfEDIUAf" FOR ANY PH4SE OF THE TK4NSIENT, IT WAS TREATED AS 4 "HIGH" OR "AfEDIUAl" FOR THE ENTIRE TRANSIEhT WITH RESPECT ID TREA TAfENTIN THE EVALUATION At0 DEL '

8)

Most subsections in the discussions on phenomena are geared too much toward the LOCA time phase, although MSLB results in the highest computed containment pressure by the AP600 EM. In most descriptions, MSLB is not mentioned at all except for the PIRT-ranking. This may be acceptable for equally ranked phenomena, but for all other cases this may pose the potential for omitting important information. The non-uniform treatment of LOCA and MSLB time phar.es does not seem justified.

CottAIENT:

THE CovTAINstENT RESPONSE 10 A LOCA IS Af0RE COAIPLEX THAN TH4T FOR A POSTULATED AfSLB.

THE APPARENT FOCUS OF AITENTION ON A LOCA IS THE RESULT OF ACCOUNTING FOR THE INCREASED COAIPLLYHY OF THE CONTAINAIEAT RESPONSE TO A LOCA. WHEN AfSLB H45 A UNIQUE ASPECT ITIS DISCUSSED.

9)

Some high-ranked phenomena. such as evaporation of the extemal liquid film, require the success of a medium and low-ranked phenomenon, i.e., PCS riser annulus natural circulation, vapor acceleration, fog ud tiow stability. Based on this PIRT, modelers may mistakenly downgrade the conservatism of models aswated with critical s,ystems.

Cu titfEAT:

RANMNG A PHENOAfENA AS " LOW" INDICATES THAT THE PHENOAIENA HAS A SMALL EFFECT ON PRESSURL IT COULD BE TREA TED WITH RL4LISTIC OR BEST ESTIAL4 TE AIODELS, OR (GNORED IF SUCH TRE4TAIENT WOULD BE CONSERVATIVE SIAf1L4RLY, PHENOAfENA K4NKED AS A "AfEDIUAl" AT ANY TIME DURING THE TR4NSIENT WERE SPECIFICALLY CONSIDERED DURING IN THE EVALUATION Af0 DEL AND WOULD BE IGNORED ONLY IF 10 DO SO WOULD BE CONSERVATIVE (RESULTIN A PRESSURE INCREASE).

THUS. THE CONSERVATISAf ASSOCIATED WITH TRL4TAfEATOF PHENOMENA K4NKED AS"HIGH" WAS NOT CHALLENGED B Y EITHER "AIEDIUAl" OR " LOW" K4hKED PHENOAfENA.

MD W CLLnLRE 16

e r

10)

Westinghouse may not be crediting the expert review efforts, because of the following reasons:

a)

The export review is no substitute for an independent PIRT panel.

I b)

There is not a sinaje pher omenon for which Westinghouse has adopted the experts' different ranking. Rather the expe ts' opinions were dismissed and the results of the scaling PI ratios were adopted (compare comment under point) maintaining Westinghouse's original ranking. Most often the experts ranked the plenomenon highe* but Westinghouse consistently downgraded the rank.

This is acceptable only for phenomena for which an in-depth knowledge and experimental database exists.

l Most often this is not the case in the ranking should tend toward higher than lower importance.

I l.

COAIAIEhT WilERE HIE PIRT RA AMVG DEluOPED B Y WESnNGHOUSE DIFFERED FROAI THA T OF EXPERT REVIEW.

JUSTIFICATION FOR THE DIFFERENCE WAS GIVEN.

THE REVIEW OF DIFFERING OPINIONS AND DEVELOPAIENT OF RATIONALE ACCEPTING OR REJECTING EXPERT REVIEW IS ALSO PART OF THE PIRT PROCESS. ITIS WESTINGHOUSE'S O*lNION THAT THE JUSTIFICATION DESELOPED FOR VARYING FROAI THE EXPERT REVIEW RANKING AND PRESENTED IN REVISION I OF WCAP.1481: 15 TECHNICALLY VALIO.

II; Descriptions ur. der the headline "How Phenomenon is implemented in Evaluation Model" do not actually refer to the implementation but rather to input quantities or general descriptions of the phenomenon / process in or between components / subsystems, in fact, for many phenomena the text is a -

repeat of at least parts of the general introductory description of the phenomenon under consideration.

Under the headline one would expect reference to models, correlations / procedures implemented in -

WGOTHIC.

COAttIENT:

' Tile DESCRIPTIONS ARE GENERALLY SUAIAURY STATEAIEhn HOWEVER, WHERE THE DETAIU AUY BE FOUND ARE INCLUDED BY REFERENCE INCLUSION OF ALL DETAILSIN THIS REPORT WOULD HA DE BEEN REPETITIOUS AND AIADE THE REPORT UNWIELDY AND DIFFICULT TO USL DETAILS OF THE IAIPLEAIENTA TION IN WGOTillC 15 FOUND IN WCA P-14407 HAGEN M*nORRE I7

6 12)

Westinghouse lists a number of" Test Experience" under the headline " Justification for EM Treatment of

- Phenomenon." However, for many phenomena this consists only of a test description or reference of a correlation w hich is not really a justincation, Underjustincation it would be expected to reference results how the containment pressure / energy transfer processes are affected using the cited correlation in comparison with data. This has not been done consistently, rather sensitivity studies and LST result comparisons are references. In hindsight, the test experience cited should well have been referenced as basis for the PIRT ranking (compare comment under point) rather than forjustincation of WGOTHIC AP600 EM.

COAnfENT:

TifE INFORAl4T10N SUGGESTED IN THIS COAIAIENT IS LVCLUDED BY REFERENCE. INCLUSION OF THE l

DETAILS IN THIS REPORT H OULD HA VE BEEN REPETITIOUS AND RESULTED LV AN UNWlELDY REPORT.

1 l

Issues Related to the Ranking of Specific Phenomena and Treatment in EM General comment: The phenomena listed under the components are not systematically handled in terms of time phases in Section 4.1.

Pg. 4-8 Table 4 1 l}

Westinghouse ranks all characteristics (direction, elevation, momentum, density) of(l) Break Source

" Low" during LOCA long-term. Equally, inter compartment flow for (2) Containment volume is ranked

" Low" for LOCA blowdown phase and so on. Given the fact that LST did not consistently cover all these phenomena with respect to AP600 requirements, the ranking seems too low especially when considering the impact of" memory effect" of early heatup in one region of the plant on global natural circulation pattern during the LOCA long term time phase. This concern also encompasses the inter-compartment nows as this determines the region of initial heatup.

COAntENT; THE BASIS FOR THE RANKING OF BRL4K SOURCE PHENOAIENA AS BEING " LOW" DURING THE LONG TERAI LOCA IS BASED ON KNOWING THAT Al459 AAlD ENERGY RELL4SES ARE sal 4LL DURING THIS 11AIE PERIOD, NOT ON TEST DA TA. SIAtlLARLY, FOR INTER-COAIPARTAIENTAL FLOW, THE " LOW" RANKING IS BASED ON SENSITIVITY STUDIES WHICH SHOW THE DETAILS OF THE FLOW PA THS ARE NOTotPORTANT.

DMN %lI dN'M 18

.]

o i

e 2)

The component / subsystem (5) Break pool does not list pool heatup as a phenomena. Is there any special consideration w hy Westinghouse has disregard this potential' source fer energy release during long-term?

COAttiLvT:

DURIVG THE LONG TERAI. THE BRL4K POOL FLOODS UP TO ABOVE THE BEL 4K LOCATION. HL4 T-UP OF THE BRL4 K POOL IS B Y CONDENSA TION OF STL4 Al ON THE SURF tCE OF THE BRL4K POOL SIVCE. LONG TEKti. THE BRL4K POOL IS REL4TilflY QUIESCEhT(LOW FLOW OUT THE BRL4K), THE COADENSAHON PROCESS IS LIAtITED BY THE FOR \\t4 TION OF A WARtf LA YER OF FLUID ON THE TOP OF THE BRL4K POOL THUS. HIE HL411:P OF Tile BREAK POOL 15 LIAllTED.

3)

Under point (7) Steel Shell and energy transport phenomena have been ranked either " Low" or " Medium",

yet the energy removal from the film evaporation (ranked High) is mandatory in order to guarantee the ef0ciency of the passive PCS cooling. Westinghouse is asked to provide information about the ranking rationale applied for energy transport phenomena in the downcomer riser component.

i COAftfEAT:

THE PRIAltRY COOLING AfECH4NISAI FOR THE AP600 COSTAINAIENT IS BY EVAPORAHON OF THE PCS FLO W.

THUS, AS LONG AS WATER IS 4PPLIED TO Tile LtTERNAL SURFACE OF THE PCS SHELL. IT IS EXPEC1ED THAT THEK\\l4L LvERGY T.tANSPORT AIECIL4NISAf5 OTHER TIL4N EVAPOK4T10N WOULD BE RANKEU AS EITHER MEDIUAl OR LOW. OF COURSE, IF THE SHELL WERE INSUL4TED. THEN TilERE WOULD BE NO LAERGY TRANSFEk H0HEVER. THE PURPOSE OF THE KINKING IS To AIAKE JUDGEAIEh75 REGARDING THE lAf?ACT OF UbCERTAINTIES ASSOCIATED WITH INDIVIDUAL ENERGY TRANSPORT PROCESSES, Tilv5. IN K4NKING THE CONDUCTION THROUGH THE STEEL SHELL NOTING 'llAT IT REPRESENTS ONLY ABOUT ll) 0F THE TOTAL RESISTANCE AND THAT SHELL THICKNESS IS WELL CONTROLLED. THE LYPER15 AGREED THA T CONDUCTION THROUGH THE SHELL SHOULD BE K4NKED OF LOWER IAIPORTANCE TIL4N CO VDENS t T10N OR EVAPOK4 T10N.

4)

Under point (8) PCS Cooling Water, subpoint D) Film Striping received only " Low" ranks for all time phases, yet this is the cause for introducing a correction for accounting for 2-D heat conduction effects to increase Olm evaporation. Westinghouse is asked to explain the " Low" ranking for this phenomena even for later phases when film Dow is low.

COAntENT:

THIS SECTION IS "STMPPING." WHICH REFERS ID THE DETACHAfENT OF Tile liqulD FILAI FROAf THE E.tTELVAL SURFACE OF THE SHELL DUE To SHEAR FORCES FROAt THE PCS AIR FLOW AND NOT

" STRIPING. " WHICH REFERS TO Tile FORAl4 T10N OF A L TERVA TING H ET AND DR Y STRIPES OF WA TER AS IT FLONS DOWN THE OUTSIDE OF THE CONTAIAAfENT SHELL THE " STRIPPING" PHENOAfENA IS tPPROPRIATEL Y R4AKED AS BEIAG " LOW "

mcas i etonas 19

1 5)

Under point (10) Baflie, subpoint G) potential leaks through the baffic are ranked " Medium" for LOCA

-+ -

Se phases peak pressure and long-term. Westinghouse is asked to explain this ranking in view of the fact that this poses a potential threat for short circuiting and thereby disabling the natural draft etTect. -

COMMEhT:

THE MAKlhG ACKNOWLEDGES THE POTEATL4L IAIPORTANCE OF BAFFLE LEAKAGL THE IATRODUCTORY TL\\T ALSO NOTES Til4T EXPERIAIENTAL DATA FOR RECTANGULAR CROSS-SECTION CH4NAELS SHOlG BAFFLES HAVING UMITED EFFECT ON HEAT TRANSFER. WHlLE NOT EVALUA1ED AS BEING A DOAllNA TE PHENOMENA. THE MNKlNG OF"AfEDIUAl" ASSURES THE PHENOMENA 15 ADDRESSED IN THE AP600 COATAINAfEAT EVALUA TION MODEL SHORT CIRCUITING HAS BEEN EVALUATED WITH SENSITUITIES AND SHOWN TO BE A MEDIUhl EFFECT.

NOTE ALSO THAT THE EVALUATION AIODEL INCLUDES A FLOW PATH ACROSS THE BAFFLE 1D ACCOUhT FOR THE POTENTIAL FOR LL4KAGE 6)

Under point 13) Downcomer, subpoints A) PCS Natural Circulation and B) Air Flow Stability are ranked

" Medium" and " Low", respectively, yet the efficiency of the PCS system depend very much on sustaining both phenomena, for transport purposes of the evaporation mass and energy from the cooling film, Westinghouse is asked to provide the ranking rationale for both phenomena given their importance for the functionality of the PCS cooling concept.-

. COM\\ LENT:

FOR PCS NATUML CIRCULATION, THE MNKING OF MEDIUM WAS BASED ON Sn! DIES SHOWING THE SENSITilTTYOF THE PCS AIR FLOW TO HYDRAUUC PARAMETERS WASSkl4LL FOR AIR FLOWSTABlUTY, THE MNKlNG OFLOW WAS BASED ONSCAUNG THE ENERGY AND MOMENTUM ASSOCl4TED WITH TliE FLOW PATil. THESTUDYSHOWED TilATENERGY ADDITION 1D THE DOWNCOMER FROM THE BAFFLE WAS SAL 4LL AND THE MOMENTUM OF A BCOYAAT BOUNDARY LAYER WOULD NOT DISRUPT Tile ESTABUSHED NATURAL CIRCUL4 TION FLOW. - THUS THE POTEATIAL FOR INSTABlUTY 10 OCCUR IN THE PCS AIR FLOW PATH IS NEGUGIBLE, AND THE PHENOMENON IS THEREFORE MNKED LOW.

744GM W CLORRE 20

O-

-+

r.

Pg.4 16 i

.. Westinghouse states that increased heat transfer coefficients were observed when the steam jet directly impinges on j

the herizontal plate and that this simulates the steamline break. Westinghouse is asked to provide information why this is the case, given the fact that the realistic break positions for both LOCA and MSLB are still not displayed in the assoc:sted figures.

- COAtstLyr j.

THE SUBJECT FIGURE 3 2 CLEARLY SHOWS DIE PRIAURY SYSTEAf PIPE WHICH GOES FROAl THE STEA AI l

GENERATOR TO THE REAC7OR VESSEL AT THE BOT 10At OF THE STEAM GLVEK4 TOR COMPARTMEhT, AND THE AIAIN STEA AI UNE WHICH LEAVES THE TOP OF THE STL4M GENEK410R AND PASSES THROLGil THE Chit COAf?ARTMEhT BEFORE - IT PENETRATES THE CONTAINMEhT SHELL IF TifE READER IS IATERESTEDIN AIORE DETAIL HE IS REFERRED TO WCAP.I4407, FIGURE 9-36, WlHCHSHOWSIN AIORE DETAIL THE ARRANGEAfENT AND VARJOUS DIRECTIONS AND MOMENTUAf EFFECf5 EVAltJATED IN ESTABUSHING THE UAtlTING LOCA AND AfSLB SCENARIOS THE STATEAIENT REFERS TO OBSERIED BEH4V10R IN EAPERIMENTS THE TEST WAS DESIGNED TO SIMUL 4TE CONDITIONS LYPECTED FROM A STL4 AI UAE BREAK THAT WOULD RESULT IN STL4M IMPINGING DIRECTLY ON THE COATAINMEhT WALL THE SL BJECT TEATIS NOTINTENDED TO IAfPL Y THA T ALL STL4MUNE BRL4KS WOULD RESULTIN A STEAM

- JETIAIPINGING ON THE COATAINMENTSHELL

-Pg.4-17 Westinghouse reports ebservations from the Small Scale PCS Integral Tests concerning i.igher than vessel-averaged heat removal at the top of the dome. However, the phenomenon of non-uniformity in heat transfer is not listed in the PIRTs. Does this mean that this phenomenon has not been observed during LST-tests?

COAIAfEATI IN REVIEWING THE PIRT FORSUT WITH LYPERIS, IT WAS AGREED TilAT AN APPROPRUTE LEVEL OF DETAIL WAS INCLUDED IN THE PIRT. THE ADDITION OF ALL PARAMETERS WHICH INFLUENCE E4CH PHEN 0%IENON WOULD M AKE THE PlRT UNWlELDY AND REDUCE RS USEFULVESS. PAK4 METERS WHICH INFLUENCE IMPORTANT PHENOMENA ARE EVALUATED IN ESTABUSHING THE RELEVANT ELEMENT 5 OF.

THE CONSERVA TIVE EVALUA TION MODEL NON-UNIFORMRY OF HL4 T FLUX 15 ENCOMPASSED BY OTHER PHENOMLVA USTED IN THE PIRT. THE SUPPLEAIENTAL INFOKtHTION REFERENCED IN THE PIRT POIN75 THE RL4 DER TO THE SUPPLEAfESTAL DOCCAIENTA TION WHERE MORE DETAll AIA Y BE FOUND.

l NON-UNIFORMilY OF HEA T FLUX IS ADDRESSED IN THE CIRCUL4 TION AND STRA TIFICATION SUPPORTING ELEAIENTS OF THE EVALUATION MODEL BASED ON INTERNATIONAL TEST DATA THATINCLUDES VAR 10US LtTERNAL BOUADARY CONDITIONS WITH.4ND WITHOUT EXTERNAL WATER (SECTION 9.C.2 OF WCAP.

I4407). THE INFLUENCE OF AXIALL Y VAR YING HL4 TFLUX ON LtTERNAL WA TER COVEK4GE IS INCLUDED

- IN THESECTION 7 WA TER COVER 4GE EVALUA DON.

MN% ON bkM N 21

(

e p. 4. I 7 g

1)

Westinghouse reports Olm behavior during the LST PCS Integral Tests, >ct is urclear w hat the gos erning heat fluxes were at the outside steel shell surface and how they compare with the relevant ones for Ap600.

CutittL VT:

ADolHotAl (HSCt:ASIOV 15 PROVIDID IVSICTIOV 7 0F WCAP 14407, ALSO. TABLE 7 3 C0\\tf<Rl3 HEt tILUYt3 Iko tt PCS L4RGE SCALE TESIS A AD TABLE 710 s.lSTS ESHtf41ED HEAT FlUALS FOR THE j

AP600 Uvol.R VARIOUSc0\\DIHONS 2)

In this context. Westinghouse states that " striped film coverage providej better heat removal than forced quadrant coverage for the same wetted perimeter." is this statement referring to an experimental setup or to a calculational exercise?

CoststEA T:

l THIS IS B 4stD Os CottPARISON OF OBSERVAH0vs FROAIL4RGE SCALE TESTS 207. I. 207.2 AND 207.3 4 th 207 4 45 DESCRIBED 1%SICHON 21.2 A %D SUAIAl4RitED Lv TABLE 2 3 of REPORT PCS T2R-030, "L4RGE \\C4LE TLSTDATA EVALUAH0s "

3)

Westinghouse states that heat atmoval rate appeared to be more affected by ambient air temperature than by liquid Olm temperature. Yet, ambient air temperature was ranked " Low." Westinghouse is a+ed to explain this effect and whether this effect has been observed in all tests.

CotfAIEA T:

THE COVCLUSION REGARDING RELA HVE EFFEC 15 0F AhtBIENT TE AtPEK4TURE AND FilAt TEAIPER 47tRE IS DIRECTL1 DERIVED FROAt LST DATA AS STATED LV THE REFERENCE 38 LST TEST A val 1515 REPORT.

THE K4alNG IS AN IVDICAHON Hiti BOTH EFFECT5 WERE S\\l4LL, AND Hiti AAtBIENT AIR TEttPER4TLRE WAS THE L4RGER OF TWO SAIAll EFFECT5. AhtBIEAT AIR TEAIPER4TURE l'ETERAtIVES HIE tt 0)L4 %CY HE4D HitiCA V BE GEAEK4TED. THIS BEH4VIOR At4Y BE NOTED IV ANY TEST WHERE THE V !kitBLE IS IHE A AtBIENT TE AIPEK4 TURE.

NM% 4%IOIM $$

22

's e

4)

Westinghouse reports that also during the LST. test non unifonn heat Out w as obsened. Why has this phenomenon not be included in the lRTs? This deems especially important for the horizontal, a

high6clocity steam jet injection. Please explain.

CottAtEA T:

/\\ REsIIHIVO IIIE PIRT 10Rtt4T HIHI LtPER15. IT W45 AGREED TH4T AN APPROPR14TE LElu 0F DET4ft W4S l\\ Cit DED IV THE PlRT THE ADDlHON OF All PAK4ttEllRS HJHCIIl\\llt LACE L4CH PHEADstEAUV HDI ID tl4KE T. E P/RT UAH1 ELD) A%D REDUCE 115 t SEFULALS5 PAR 4UETERS WHICH

\\

l% FLUENCE lAIPORTAAT PHEAostEA 4 ARE EV4tC41LD IV ESTABLISHIVG IllE RLLEVAVT ELEAtENTS OF THE C0\\St.RVA tli E El AlUtilov AIODEL NO\\ UNIFORttl1Y OF HL4T flVX15 ENCOUP.45%ED BY 01HER PHENOAIEN4 ilSTED IV THE PIRT. THE SlPPLEAtENTAL lAf0RAl4 HON REFERENCED IV THE PIRT Polvi5 THE READER TO THE SUPrtl AtENT4L DOCUAIEATAHON HHERE AIORE DETAll A14 Y BE FOUAD.

No sCNIFORAllTY OF HEA T I LUX IS ADDRl3 SED IV THE CIRCl L4 Tl0% A A D STK411 FICA TIO V SUPPORTING ELEAfLN15 0F HIE EVALUAHOV AIODEL B4 SED ON IVTERN4110 VAL TEST LI4TA TH4TINCLUDES I ARIOUS L\\TERNAL BOCAD4RY CONDlHOVS HlTH AND H1THOUT EATEKVAL WATER (SECHON 9 C.2 0F IVCAP.

I4407) THE lAFLUENCE OF AA)4LL Y I 4RfIVO HEA T FlCX ON EATERVAL WA TER C0\\ f R4GE IS INCLUDED IV THESICHOV 7 H 41ERColLK4GEEV4LU4110%

5)

Weringhouse states that by raising the steam injection location, heat removal rate increased as the steam concentration near the containment shell increases. 'This is true but this positive effect is offset by the reduction in stcara concentration at lower levels by stratincation. Westinghouse is asked to provide more quantitative results for these observations.

COUttENT:

A DETAILED DISCUSSION ON THE OBSERs'ATIONS ASSOCIATED HITH THIS BEH4010R IS INrlCDEl> IV SECHO V 2. 4, "STL4 slIV 'ECn0% LOCA HON 4 % D FLOW RA TE. " 0F PCS.T2R-0$0. "L4RGraCALE TEST D4TA EV4LUA H0Y "

04sM % %$ INN N 23 o

%9 Li

't General itemarks ne summary presentation of experimental results has largely impros ed and is more focused than before, llowes er, rnost information are of qualitatis e, desenptise nature, rather than quantitative solid esidence. Overall, the list of findings seems still too short. The Ondings should be structured such that the results are directly related to the phenomenon under consideration.

C0\\itti.\\1 Tlli DISCCSSIOV PROVIDED IV Tills RLPOR115.4 StiAtti4Rr. DET41LS of LtPERitiLVTAL RESULis USED 10 SUPPORT DED fl0P\\tLVT OF Tile PIRT ARE IvCivDtD By StrCinC REnnisCf.s 10 APPUC.4BLE REPORTSIV TIIE DISCCSS10 VS.

Pg.4 19 Outside Containment Westinghouse states that "the buoyancy and How resistance in the PCS air now path are important and have a strong effect on the evaporation ra'e." llowever, both buoyancy and How resistance are not listed as phenomenon /p.tremeter in the PIRT. If it is assumed that both phenomena were considered to be covered by

" natural circulation", these phenomena would only be ranked medium, an apparent inconsistency.

CottttLVT:

4 AIEDICAf K4%Kl%0 FOR NATUK4L CIRCUL4T10V IS APPROPRl4TL IT IS IAIPORTA VT BUT IS SECOND ORDER RLL4 Tli E 10 El'4P06L4T10V 66 tilCilIS K4 VKED filGil SENSITiiTTIES 7011/ESE P.lK4 AIETERS IS PROVIDED IN WCAP.I4407.

OkN N %$ NNk N 24