ML20198Q888

Requests That Proprietary AP600 Response to FSER Open Items, Be Withheld,Per 10CFR2.790

ML20198Q888
Person / Time
Site:	05200003
Issue date:	01/16/1998
From:	Sepp H WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:	Quay T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20070L210	List: ML20198Q888 NSD-NRC-98-5526, Provides Proprietary Westinghouse Responses to NRC FSER Open Items 480.1085F (Oits 6187) & 480.1086F (Oits 6188) Re Wgothic Evaluation Model.Proprietary Responses Withheld,Per 10CFR2.790
References
AW-98-1197, NUDOCS 9801230162
Download: ML20198Q888 (58)

Text

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Westinghouse Energy Systems h 355 Pmstugt Pemsylvama 15230 0355 Electric Corporation; AW 981197 January 16,1998 pocument Control Desk

- U.S. Nuclear Regulatory Commission Washington, DC 2055's ATTENTION:

MR. T. R. QUAY APPLICATION FOR WITilllOLDING PROPRIETARY INFORMATION FROM PUBLIC DISCLOSURE

SUBJECT:

AP600 RESPONSE TO FSER OPEN ITEMS

Dear Mr. Quay:

The application for withholding is submitted by Westinghouse Electric Company, a division of CBS Corporation (" Westinghouse"), pursuant to the provisions of paragraph (b)(1) of Section 2.790 of the Commission's regulations. It contains commercial strategic infcrmation proprietary to Westinghouse and customarily held in confidence.

The proprietary material for which withholding is being requested is identified la the proprietary version of the subject report, in conformance with 10CFR Section 2.790, Aftidavit AW-98-il97 accompanies this application for withholding setting forth the basis on which the identified proprietary information may be withheld from public disclosure.

Accordingly, it is respectfully requested that the subject information which is proprietary to

. Westinghouse be withheld from public disclosure in accordance with 10CFR Section 2.790 of the Commission's regulations.

Correspondence with respect to this application for withholding or the accompanying affidavit should reference AW 98-1197 and should be addressed to the undersigned.

Very truly yours,.

llenry A.

.p,' Manager.

- Regulatory and Licensing Engineering jml l

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Kevin Bohrer -

NRC OWFN MS 12E20 1

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-COMMONWEALTil OF PENNSYLVANIA:

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- Before _me, the undersigned authority, personally appeared lienry A, Sepp, who,- being by me-i duly sworn according to law, deposes and says that he is authorized to execute this Affidavit on behalf.

of Westinghouse Electric Company, a division of CBS Corporation (" Westinghouse"), and that the averments of fact set forth in this Affidavit are true and correct to the best of his knowledge,

. Information, and belief:

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/ Al' Ilenry A. Sepp, Manager Regulatory and Licensing Engineering Sworn to and subscribed -

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AW 981197 (1)

I am Manager, Regulatory and Licensing Engineering, in the Nuclear Services Division, of the

- Westinghouse Electric Company, a division of CBS Corporation (" Westinghouse"), and as such, I have been speci0cally delegated the function of reviewing the proprietary information sought to be withheld from public disclosure in connection with nuclear power plant licensing and rulemaking proceedings, and am authorized to apply for its withholding on behalf of the Westinghouse Energy Systems Business Unit.

(2)

I am making this ABidavit in conformance with the provisions of 10CFR Section 2.790 of the Commission's regulations and in conjunction with the Westinghouse application for withholding accompanying this Affidavit.

(3)

I have personal knowledge of the criteria and procedures utilized by the Westinghouse Energy Systems Business Unit in designating information as a trade secret, privileged or as confidential commercial or financial information.

(4)

Pursuant to the provisions of paragraph (b)(4) of Section 2.790 of the Commission's regulations, the following is furnished for consideration by the Commission in detennining whuher the information sought to be withheld from public disclosure should be withheld.

(i)

The infonnation sought to be withheld from public disclosure is owned and has been held in confidence by Westinghouse.

(ii)

The information is of a type customarily held in confidence by Westinghouse and not customarily disclosed to the public. Westinghouse has a rational basis for determining the types of information customarily held in confidence by it and, in that connection, utilizes a system to determine when and whether to hold certain types of information in confidence. The application of that system and the substance of that system constitutes Westinghouse policy and provides the rational basis required.

Under that system, information is held in confidence if it falls in one or more of several types, the release of which might result in the loss of an existing or potential competitive advantage, as follows:

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,e.

AW-981197 (a)-

The information reveals the distinguishing aspects of a process (or component, structure, tool, method, etc.) where prevention of its use by any of Westinghouse's competitors without license from Westinghouse constitutes a competitive economic advantage over other companies.

(b)

It consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), the application of which data secures a competitive economic advantage, e.g., by optimization or improved marketability.

(c)

Its use by a competitor would reduce his expenditure of resources or improve his competitive position in the design, manufacture, shipment, installation, assurance of quality, or licensing a similar product.

(d)

It reveals cost or price information, production capacities, budget levels, or commercial strategies of Westinghouse, its customers or suppliers.

(c)

It reveals aspects of past, present, or future Westinghouse or customer funded development plans and programs of potential commercial value to Westinghouse.

(f)

It contains patentable ideas, for which patent protection may be desirable.

There are sound policy reasons behind the Westinghouse system which include the following:

(a)

The use of such information by Westinghouse gives Westinghouse a competitive advantage over its competitors. It is, therefore, withheld from disclosure to protect the Westinghouse competitive position.

(b)

It is information which is marketable in many ways. The extent to which such information is available to competitors diminishes the Westinghouse ability to sell products and services involving the ese of the information.

wr

AW 98-1197 (c)

Use by our competitor would put Westinghouse at a competitive disadvantage by reducing his expenditure of resources at our expense.

(d)

Each component of proprietary information pertinent to a particular competitive advantage is potentially as valuable as the total competitive advantage. if competitors acquire components of proprietary information, any one component may be the key to the entire puule, thereby depriving Westinghouse of a competitive advantage.

(e)

Unrestricted disclosure would jeopardize the position of prominence of Westinghouse in the world market, and thereby give a market advantage to the competition of those countries.

(f)

The Westinghouse capacity to invest corporate assets in research and development depends upon the success in obtaining and maintaining a competitive advantage.

(iii)

The infonnation is being transmitted to the Commission in confidence and, under the provisions of 10CFR Section 2.790, it is to be received in confidence by the Commission.

(iv)

The infonnation sought to be protected is not available in public sources or available information has not been previously employed in the same original manner or method to the best of our knowledge and belief.

(v)

Enclosed is Letter DCP/NRCl216 (NSD-NRC-98-5526), January 16,1998, being transmitted by Westinghouse Electric Company @), a division of CBS Corporation

(" Westinghouse"), letter and Application for Withholding Proprietary information from Public Disclosure, Brian A. McIntyre @), to Mr. T. R. Quay, Office of NRR. The proprietary information as submitted for use by Westinghouse Electric Company is in response to questions concerning the AP600 plant and the associated design certification application and is expected to be applicable in other licensee submittals in respcnse to certain NRC requirements for justification of licensing advanced nuclear power plant designs.

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0 AW.981197 4

This information is part of that which will enable Westinghouse to:

(a)

Demonstrate the design and safety of the AP600 Passive Safety Systems.

(b)

Establish applicable verification testing methods.

(c)

Design Advanced Nuclear Power Plants that meet NRC requirements.

(d)'

Establish technical and licensing approaches for the AP600 that will ultimately result in a certified design.

(c)

Assist customers in obtaining NRC approval for future plants.

Further this information has substantial commercial value as follows:

(a)

Westinghouse plans to se:I the use of similar information to its customers for purposes of meeting NRC requirements for advanced plant licenses.

(b)

Westinghouse can sell support and defense of the technology to its customers in the licensing process.

Public disclosure of this proprietary information is likely to cause substantial harm to the competitive position of Westinghouse because it would enhance the ability of competitors to provide similar advanced nuclear power designs and licensing defense services for commercial power reactors without commensurate expenses. Also, public disclosure of the information would enable others to use the information to meet NRC requirements for licensing documentation without purchasing the right to use the information.

i nuig

AW 981197 l

The development of the technology described in part by the information is the result of applying the results of many years of experience in an intensive Westinghouse effort and the expenditure of a considerable sum of money.

In order for competitors of Westinghouse to duplicate this information, similar technical programs would have to be performed and a significant manpower effort, having the requisite talent and experience, would have to be expended for developing analytical methods and receiving NRC approval for those methods.

Further the deponent sayeth not, i

ti%.pt.

, to Westinghouse Letter DCP/NRCl216 January 16,1998 nu-N

NRC FSER OPEN ITEM

- FSER 01 480.1085F (OITS 6187)

The correlations and models used in WGOTHIC for heat and mass transfer are based on local conditions independent of scale. The only test data relevant to the AP600 are from the LST, where local variables were measured and stratification phenomena were shown to exist for some of the tests. Many other experimental f acilities in the world data base have also show stratification.

The AP600 WGOTHIC evaluation model (EM), used for design basis accident analyses, is unable to compute steam concentrations and temperature gradients correctly in its lumped parameter mode. Many of the model features, such as the choice for the main steam line break (MSLB) position and the use of the Chun and Seban correlation with the evaporated flow model tend to minimize heat flux gradients.

Westinghouse,in WCAP 14407,'WGOTHIC Application to AP600," Revision 1, states that the local conditions at the shell wall can be calculated in a conservative manner.

However, Westinghouse has not provided sufficient evidence to demonstrate that WGOTHIC provides a conservative calculation of local conditions at the shell wall.

Westinghouse arguments in the application report address vertical stratification (an extreme stratification was used), but do not address gradients in the horizontal direction (including the boundary layer next to the shell).

To address the latter, one approach would be to show that the containment atmosphere is indeed well mixed, from a theoretical (first principles) standpoint. The staff considers this approach to be very difficult, particularly in light of the non homogeneity seen in the world data base. Another approach would be to demonstrate that the lumped-

. parameter WGOTHIC EM conservatively calculates the effects of the local steam concentration near the condensing surfaces.

The current analysis is unacceptable until the one of the above approaches, or an acceptable attemative, is implemented.

Response

Approach Thermal and concentration gradients in the horizontal direction, including the boundary layer next to the shell, are addressed in the following discussion using results of theoretical, or first principles, calculations. The, wall boundary layer steam concentration profile is examined using turbulent boundary layer models. Entrainment and boundary 480.1085F 1 3 W65tinghouS8 i

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NRC FSER OPEN ITEM layer profile calculations are used to estimate the magnitude of the steam concentration in the walllayer and rising plume as compared to the bulk average steam concentration at a given elevation. Test data, where available, are used to support the conclusions.

Results show that steam concentration gradients within the turbulent boundary layer in the horizontal direction are relatively flat, indicating good mixing within the boundary

-layer. The majority of the gradient near the condensing PCS surface (inside containment) occurs within a relatively thin region of the boundary layer, so that the use of boundary layer heat and mass transfer correlations in WGOTHlO is appropriate.

halzontal gradients in AP600 during the post blowdown LOCA are addressed for the -

base case scenario which assumes that the source mass "ses from the East steam generator compartment as a buoyant plume, having lost its momentum as it passes around the equipment and blockages and through the compartment. The assumption of a buoyant plume,' Her than a forced plume or jet, reduces momentum induced circulation which is alts in conservatively large calculated gradients. (Horizontal gradients for MSLB are discussed and supported with tost data in the response to 480.1086F.).

The potential magnitude of horizontal gradients are examined in three radial regions:

(1) the rising plume; (2) the recirculating stratified region; and (3) the boundary layer.

The three radial regions are depicted in Figure 480.1085F 1. Such a three-region approach is similar to that suggested by Peterson (Reference 1). In the region wise discussions, area fractions are developed and processes which affect horizontal gradients within each region are described. The test bases for the discussions include the LST, as well as smaller scale separate effects natural convection enclosure tests.

The general interaction between the regions via entrainment is then used to summarize how the integral system performs.

Region 1 Horizontal Gradienta Referring again to Figure 480.1085F 1, Region 1 is comprised of the rising plume and its entrained flow; Region 2 is the nearly quiescent, recirculating stratified region; and Region 3 is the falling wall boundary layer and its entrained flow.

In Region 1, the concentration profile within an entraining buoyant plume is characterized by a Gaussian profile at any given elevation, with the steam concontration at the edge of the plume equal to that of the supplying Region 2. Such a profile has been proposed by Blevins (Reference 2) Calculations sinow that the plume centerline -

steam concentration at the exit of the plume in AP600 is near that of the bulk, within 10% (0.04/(1-0.6).= 0.10) (Attachment 1, page 3). At the top, the plume occupies about

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25% of the cross sectional area, based on an axisymmetric round plume with a divergent angle of 7.5 degrees from the exit cf the steam generator compartment, where the plume equivalent diameter is 32 feet based on the exit area of the trapezoidal steam generator con.,.Fment opening (without reduction for blocked area of the steam generator itself), the cor"ainment radius of 65 feet, and plume height of 121 feet.

Region 2 Horizontal Gradients The horizontal gradients in Region 2 can be assessed based on indications from LST temperature data and by examining the postulated condition of a non uniform horizontal gradient.

Both the LST above-deck region and the AP600 have been shown to be nearly well-mixed with entrainment as the causal mechanism using two approaches - solution of the equations for turbulent p.Ofll6s within Region 1 (Attachment 1) and Region 3 (Attachment 3) to qur.cify in region variations, and solution of the integral equatiors for the interface quantiiy of total volumetric entrainment into a region over its height (Attachment 2),

The entrainment calculations show that entrainment ratios (ratio of entrainment to source volumetric flows) are greater for AP600 than for the LST. The LST has been examined for evidence of horizontal gradients outside the wall boundary layer. Time-averaged thermocouple rake data for LST tests in the LOCA configuration at two different steam flows (220.1 at 0.5 lbm/sec; 217.1 at 1.0 lbm/sec) show a near zero horizontal temperature gradient except above the steam plume and over the distance within one inch of the wall (Attachment 3). Since the convective processes operating in the bulk gas region mix temperature differences and gas species at the same rate, the observation that there is no horizontal temperature gradient also shows that there is no horizontal gas concentration gradient, and therefore, no density gradient. The data show that all of the measurable temperature drop in the vessel wall boundary layer occurs between the wall and the thermocouple 1 inch away from the wall. This is consistent with boundary layer calculations which indicate that the majority (60%) of the gradient occurs within the first 0.25 inch of the 7 inch boundary layer at the LST operating dock level.

LST thermocouple rake data at successive, incremental data collection times, shows evidence of buoyancy forces eliminating horizontal gradients. Data from the thermocouple rake was taken every 90 secondf. during the LST matrix tests. The data at some point in time may show that the temperature at a measurement location may deviate less than ten degrees Fahrenheit from the horizontal average. Data at the next 440.1065F-3 e

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time interval indicates that horizontal gradients are not maintained for more than the 90 second data acquisition interval. This is evidence that a perturbation which creates a nonhomogeneous density at a given elevation also creates a local relative density driving force which tends to level out the horizontal density gradient. This is to be expected since, in the nearly quiescent Region 2 away from its boundaries, there are no imposed fyrces which could maintain a density gradient, so that gravity will neutralize any gradients that would form, tending to result in a time averaged flat profile.

Separate effects enclosure test data show that as the Rayleigh number, Ra, (defined 8

between the vertical, heated and cooled walls) increases from 3.Sx10' to 1x10, the circulation mechanism fully transitions to turbulent, and the horizontal gradient becomes primarily concentrated in the thin wall boundary layer (Reference 3 Section 9.C.1.1.2.1, see for example Figure 9.C.15). These tests show that at Ra > 10', the core horizontal gradient is nearly zero in two dimensional enclosures. The same reference summarizes data from three dimensional enclosures which suggests that the transition to turbulence may occur at Ra < 10', due to vortices which affect mixing inside the core of the enclosure by communicating between the front and back walls through the middle of the enclosure. The AP600 Rayleigh number between the plume centerline and the cooled wall is 4.2 x 10" based on a 9'F temperature diffe'ence. Therefore, the AP600 is fully turbulent and would be expected to show little or no horizontal gradient in Region 2.

Falling plumes have been shown to occur with upper horizontal surfaces cooler than the enclosure and to result in an additional mixing mechanism (Reference 3. Figures 9.C.1-15 and 9.C.1 16) which would further homogenize the containment gases. The presence of plumes of cooler gases descending from the underside of the dome, suggested by the large AP600 vertical Grashof number on the order of 2x10", based on a temperature difference of 9 degrees F (Reference 3, Section 9.C.1.3.1), are conservatively ignored.

Separate effects enclosure test data spans up to Ra equal to 10'. Numerical studies by Markatos and Pericleous predict that the heat transfer behavior is constant (Nusselt number linear 1y increases with length) at increasing Ra over many decades up through Ra of 10"(repeated in Reference 3, Figure 9.C.1-6), suggesting that increased heat transfer is primarily a result of thinning of the boundary layer. The implication is that the Nusselt number wries monotonically over that range, and thus no unexpected performance is introduced at higher Ra values.

In a bulk region such as Region 2 in the AP600', while one may not rule out some minor transient horizontal gradients, there are no forces to maintain a horizontal gradient

. outside the relatively small volumes occupied by the plume and falling wall layer. That is, any postulated deviation from horizontal uniformity would tend to be readily flattened 440.1085F 4 Westinghouse

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by buoyant forces.- Therefore, the horizontal gradients in AP600 may be assumed to

l occur solely _within the plume and wall layer.-

g LRegion 3 Horizontal Gradients Region 3 consists of the falling wall boundary layer. Equations for the velocity,

temperature, and air concentration boundary layer profiles are presented in Attachment

3. page 2. The profiles are based on turbulent boundary layer in power laws, ao used -

by Eckert and Jackson.' More recent work in the area of turbulent boundary layer

. profiles has led to the refinement of the boundary layer into 3 or more layers, such as the viscous sublayer, logarithmic law layer, and outer layer, to attempt to increase

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accuracy. Such multi-layer models may indeed increase the accuracy; but results show the in power profile to be reasonable to use for simple calculations.

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- The results of the boundary layer calculation for LOCA post-blowdown atmosphere are i

compared to calculations for the LST in the LOCA configuration, that is, having a diffuser below the steam generator compartment. The LST includes the effects of both temperature and concentration as driving forces for natural convection. Conclusions regarding the thin part of the boundary layer near the wall, over which most of the gradient occurs are consistent with observations of the intomal thermocouple rake data F

from LST.

The normalized steam concentration profile versus normalized distance through the boundary layer is plotted in Figure 480.1085F-2a. The parameter, C, represents local boundary layer' steam concentration, and the subscripted values represent: _s for surfacc, and b for bulk. The normalized value,71, is x/6, where x is distance from the wall and 6 is the boundary layer thickness. From Figure 480.1085 2a, it can be seen

that the average steam concentration in the oun ary ayer s on yl 12.5% lower than the b

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- steam concentration in the bulk.'

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>The maximum boundary layer thickness has been calculated from the Eckert and

~ Jackson style model to be less than 31 inches at the operating dock level in AP600

.(assuming that a turbulent boundary layer exists for the full AP600 containment height).

From_ the calculated profile, it is found that 60% of the change from bulk to wall

. conditions occurs over the first 2% % of the boundary layer, or over less than the first Linch in AP600,- Furthermore, these boundary layer calculations conservatively

overpredict wall layer thickness due to neglecting the effects of suction at the boundary i

f(velocity normal toward the wall due to condon.sation).- From the thickness calculations

'and based on a containment radius of 65 feet, while the boundary layer occupies less A

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l than 9% of the area ct the operating deck elevation, the region of significant j

- concentration'differeoce occupies less than 0.5% of the area.

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Oomochite Region Discussion 1

Referring again to Figure 480.1085F.1, Region 1 is, comprised of the rising plume and i

its entrained flow; Region 2 is the norly quiescent, recirculating stratified region; and

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Region 3 is the falling wall boundsry layer and its entrained flow.

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Region' t occupies about 25% of the cross section at the top, and Region 3 occupies about 9% of the cross section at the bottom, the maximum cross section for each. -

Thus, it is reasonable to neglect interaction between the rising plume and the falling wall -

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layer inl simple first principles calculations.- Since the plume occupies about 25% of the cross sectional area at the top, and even less at lower elevations, as a first approximation the effects of the enclosure walls and dome on plume entrainment over the 121 foot plume height is noglected. Similarly, with the even smaller area occupied by the falling wall layer, the effects of the enclosure are neglected when calculating wall boundary layer entrainment rates.

At a given instant in time, the rising plume of Region 1 is supplied to the above-deck volume from the top of the steam generator cavity. Pbme entrainment calculations (Attachment 2, page 2) show that 5 to 14 times the source flow is entrained from Region 2 over the height of a buoyant plume above the operating deck in AP600. Therefore, the plume average steam concentration would be expected to be near that of the bulk by the time it discharges to the top of Region 2, As discussed previously, entrainment is i

'shown to result in a centerline plume steam concentration at the top that is within 10%

' of the bulk average steam concentration. -

1 The flow' leaving Region 1 spreads _ orizontally and feeds Region 2 at the top. Since

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h higher order mixing mechanisms have been neglected, by continuity, the vertical flow velocity at the top of Region 2 is a low velocity not downward flow with a steam

- concentration reduced by condensation and heat transfer on the dome to a value lower than the steam concentration discharged from Region 1.-

4 In Region 3, condensation develope a liquid film over the full height of the containment -

shell and_a negatively buoyant gas boundary layer that grows with distance down the :

1 shell/ Noting that at quasi steady conditions, the volumetric bondensation rate on the s

/ wall is just.oqual to the source flow rate;Q. wall boundary layer entrainment i calculations (Attachment 2, page 4) show that the volume of steam condensed on the i e J shell is only 1/6 to 1/13 'of the volumetric flow rate of gas entrained into the falling wall t

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NRC FSER OPEN ITEM layer. Such large entrainment rates relative to the condensation rate suggest that the average steam concentration exiting Region 3 would be near the bulk steam concentration of Region 2. These results are consistent with wall boundary layer profile calculations, discussed previously, which show that the average steam concentration through the boundary layer is only 12.5% below the steam concentration in the bulk.

Because global, or large scale, circulation through the operating deck reduces stratification in the above deck region (Reference 3, Section 9.C,1.4.2.4), global circulation through the operating deck is conservatively neglected for this discussion.

By continuity, the flow exiting the bottom of Region 3 spreads out over the operating deck area, rising in Region 2 with a low net upward velocity and with the same steam concentration as the exit flow of Region 3. Because the top of Region 2 is fed by the plume and the bottom of Region 2 is fed by the wall layer, Region 2 will have a higher steam concentration at the top than at the bottom.

in this simplified model, as one moves from the top down in Region 2, entrainment into both the plume and the walllayer on either side of Region 2 steadily reduces the downward flow; similarly the upward flow from the bottom is reduced as one moves upward from the operating deck. There is, therefore, a neutral plane in Region 2 where the vertical velocity goes to zero.

A simplified representation summarizing horizontal gradients through the three regions, consistent with the above discussion, is shown in Figure 480.1085F-2b.

Influence of Horizontal Gradients on Mass Transfer Coefficients Since only free convection is assumed throughout the design basis containment transients, the velocities calculated in the lumped parameter model are not used in calculating mass transfer rates. Therefero justification of the approach taken for mass s

transfer is based on steam concentration gradients.

The horizontal concentration gradients in the post LOCA containment atmosphere are consistent with the lumped parameter noding and associated mass transfer coefficients used in the WGOTHIC Evaluation Model. Horizontal gradients are near zero outside of the volumes occupied by the falling walllayer and the rising plume. The scale of significant concentratiori gradients near the wall are much less than the 2 foot thick -

l calculation cell (node) used in the WGOTHIC Evaluation Model. Thus the wall cell is large enough in the radial direction that cell properties can be used to represent the bulk condition for use with boundary layer heat and' mass transfer correlations (Reference 4).

440.1085F 7

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References

1. Peterson, P.F.,"Sca' ling and Analysis of Mixing in Large Stratified Volumes,"

InternationalJournalof Heat and Mass Transfer, Vol. 37, Suppl.1, pp 97106,1994.

2.

Blevins," Jets, Plumes, Wakes, and Shear Layer," Aeolied Fluid Dynamics Handbook,1984.

- 3. WCAP.14407, Rev.1,"WGOTHIC Application to AP600," July 1997.

4. WCAP 14326, Rev.1," Experimental Basis for the AP600 Containment Vessel Heat and Mass Transfer Correlations," May 1997.

SSAR Revisions:

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NRC FSER OPEN ITEM Containment Steel Shell Op

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Regen 1 Plume Regen 2 Recirculatng Strathed 0,,

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Regon 3 Negatively Buoyant Gas Boundary Layer et Operating Deck f

O, Source plume volumetric flow at exit of steam generator compartment 0,

=

Volumetric plume entrainment from Region 2 0,,

=

Volumetric wall boundary layer entrainment from Regior 2 0, et

=

Volumetric plume flow feeding top of Region 2 0,

=

Volumetric boundary layer flow feeding bottom of Region 2 Ost

=

Figure 480.1065F 1 Interactions Between Containment Regions During Post Blowdown LOCA (Low Momentum) 440.1085F 9 T mainstmuse 1

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Normalized Steam

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Concentration, C Cs L-Average bourdary layer CD Cs concentration = 0.875 03 03 0t 1

Os Os 04 02 0

Normalized Boundary Layer Thickness, q = 6/x Figure 480.108SF-2a Detail of Steam Concentration Dlatribution in Boundary Layer See Fgure 4801065F 2a n

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CL Figure 480.1085F 2b Qualitative Ra' dial Concentration Profile from Plume Centerline to Shell at Mid Elevation 480.1065F 10 gp

ATTACHMENT I =

Turbulent Buoyant Plume' Analytical Model. Species Concentration Ic Nomenclature (See Figure 1) u = velocity in plume C = concentration of air in plume T = temperature in plume u = ambient velocity C = ambient species concentration T. = ambient temperature Co = plume centerline concentration 5

Subsenpts:

= = bulk or ambient

' o = source CL = centerline II.

Major Assumptions

1. _ Plume is turbulent and buoyant (i.e., density inside plume is less than ambient) 2.

Plume is not confined by wall surfaces. It freely develops until it reaches dome 3.

Ambient conditions are quiescent / uniform (i.e., well mixed reservoir)

' 4.

Plume is axisymmetric/round 111.

References I.

Blevins," Jets, Plumes, Wakes,and Shear Layers", Applied Fluid Dynamics Handbook,1984, pp. 247 251 IV.

Solution The analy tical solution to the turbulent, buoyant plume model with the above assumptions is already known, and the results are summarized in Table 9 7 Turbulent Plumes in Constant Density Reservoirs.of Reference 1.

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• 4 0 f*e :ca'ea *e.4,e 9

• Spec AC 1.es4*C r wa tee (48 -9 5014*4 % 54 ) e.ps,*e i t e a g'e 8

39'.e414e'* 838 3 4*e 3tw*e h * *> e.6N*e *4e 'O'e f * '83 5' $ l'4*Ce b9" $N

• e 4 8 9 -

a f

• last et 49*Ce*fra! 08 -t'4:.4 ') 'e10%gif e'e' 4 o * *

• 4 e 41 se SpoC et 43*C4*l*4t y T

e * *t 4 sett to e

• Cea'e'

• e a s 4.e et 't 8.

• Pe*S*e'le ae'OCa s9'*ewaeaf*,4 afe r

8'w*e 4

• 88 84 9 l'89C8 3* $' f,

• 3* '*4 3%*e, a tegag'gegg g giga 4g 49* Ce*fe' J 4*e eesmeege g, ggeg tg,egig g.t 3.*J 4 **g,cgerg ch e **e 13eM 4 eatt 8 apc'3s #*4 0 y 1'M j

j Ass 6ame&Ttt

.,y 7.~.te Strattettstts

• .4** t' me

1. 1.e f34*4) 71.1e

• • • ter.ime vel 4 City. v,;

.g't)

) g g !)

• t'l 24 entti, t.

1 097 s l

1.

s

1. As tal velocity

• 2 l

.g.g,,,.

preftleil8 e..,77.,3 l e

/v,

{

4 e, vet.se !!aw rate. Q l gg g /),

y g g '.' )

t

, /)

)

3.- re,, e, a.... u e.

4 m

,,.6,1,.1 m,,e,,- m. ) )

f e e teuentration 17, a

8 0

.1) f

.?O a

4. Spectes soccentrattan

' O ettth, t.g

'- ipe!Let 44ncentfattan

. I 2

,,,,v,g

,gggF,s pfaftlei%'. It'if,

e e

1. intte tnsent ve loc ity, L IO v, 0 041 e,

'e

9. Devnett e n,.ste r.

l

). o 1-.)i i n 1 !) 2/3

?

2- -

.u.

e V.

Application of Turbulent Buoyant Plume Results to LST/AP600 Applying the plume centerline species concentration analytical solution, we obtain a. expression for plume centerline air concentration. Cct. (Note that C replaces T. and z replaces x from Table 9 7 of Ref.1.)

C, = C., - 11(0, AC,)B-"'z-"

ei w here, B = 90, P - P'"" 3 -= Buoyancy Flux f

P-dC = Omerence in concentretci of air in plume and ambient Q, a Volumetric flow rate of source Applying the above expression to LST Test 213.lB and AP6, at the same total pressure (i.e..

(

1)" psia) and non condensible concentration (i.e.. [

1]"), the air concentration values at the top of containtnent can be obtained:

For LST Test 213.1B:

=

b,s.

- T1.2a4,uMT St,'OYett PLDeE 2

~

ATTACHMENT 1 Q, = th' = <[- [* lbm / sec =[

[., ft' / sec P.o

[

f' Ibm / ft' B = 32.2 x 8 x 0.35 = 90.2 E" ~ E'" = 0.35 where p. = p, + p.o P-AC, = C. 0 = 0.60 AC = C. x 11 x 8 x (90.2T x (13.2f" = 0.16 For AP600: (assuming the same bulk species concentration as LST 213.1)

p. = 29.8 psia, p, = 17.9 psia, p,,, = 11.9 psia T. = 202*F. z = 110 ft C. = p,/p = 0.60, p o = 0.0723 lbm/ft' g,,

Tho 15.4 lbm / sec 3

= 213 ft / sec 3

Psimo 0.0723 lbm / ft

- B = 32.2 x 211 x 0.305 = 2072 P - Psm = 0.305 P-AC = 0.60 x i1 x 213 x (2072)' x (110)'" = OD4 P.- Pen Pressure O.

C.

z B

AC

. Cet p,.

(atm)

(ft /sec)

(ft)

(ft*/sec*)

(note 2)

(note 2) 3 LST 2

0.35

[ f*

0.60 13.2 90.2 0.16 0.44 AP600 2

0.305 213 0.60 110 2072 0.04 0.56

. Notei 1.

Concentration values refer to air concentration

' ' 2.

Concentration values are at top of containment

. vtanumaeoverruw -

3-

ATTACilh!ENT I

==

VI. Conclusions:==

1.

AP600 turbulent buoyant plume should provide better dilution of steam cornpared to LST due to the increased height above the source in AP600, and the z " dependence for naising/entrainment.

2.

The centerline concentration in the plume is close to amb et conditions for both AP600 and LST a' the top of coatainment. Due to turbulent miung, the aserage concentration in the plume should be esen closer to ambient conditions.

CL E

Z

_M_] '

- Turbulent Buoyant Plume r

/

N

/

N

=,

/ !N

[

N

~<

Ouiescent Bulk Region C.

/l N

o

/!N O,

L 0

FIGURE I 6

R SSt L$%7 tt 04 A%T Ptl%et 4

A1TACHMENT 2 Entralmaneet late the Break Please and Wall Laser, f

and the Effect on Mass Transfer Mate i

1.0 Introduction ne purpose of this calculauon is to determine the entrainment rate into the break plume and into the negatnely buoyant walllayer in AP600 containment during a large LOCA. ne entrainment rates are used to calculate the diludon of the plume and buoyant layer to get the steam / air concentrauons at the top (dome) and bottom (deck t

elevahon) of containment. With the steam / air concentrations, the effect on the mass transfer rate in the dome region and at the operating deck level is determined.

2.0 Basis for Calculat6en ne plume and buoyant walllayer entrainment models recommended by Peterson' for mising in large stratified i

solumes are used. It is assumed the bulk Ouid is at a constant density 3.0 Entrainment into a Buoyant Plume ne volumetric How rate entrained is:

Z /3 0) i 8

Q,,, = 0,15 B /3 4

dhere: Z=

100, ft, the height of the plume (steam generator cavity outlet to dome)

B=

g Q,(p,,,,,

p,)/p,,,, the buoyancy Q,=

the break steam volumetric now rate p, a the break steam density (assumed to be the saturation density at the total pressure p,. = density of the ambient gas, the same density as the entrained gas, p,,

it is convenient to denne the plume entrainment ratio:

r, = Q,,,/Q,= 0.15 g"8 (Ap/p)" Z" Q,~8

For entrainment into (Le plume, conservauon of mass th,,, = sh,,,, + th, with th = Qp, gives Q,,,,p. = Q,,p., +

Q,,p, Conservauon of man for each species produces the reladonships Q P,

• Q,,p.., + 4p6. ar.d Q,,,,,p,. = Q,,,p,,, where the s and a subsenpts indicate the parual densiues of the steam and M. With parual density and pressure p,, P/R,T. so mass conservation for each species becomes Q

P,,,,/1. = Q,,,P,,/T,,, + Q,P,,fr and Q,,,P,,fr,,, = Q.P.,,,ft. Since the absolute tempersture does not differ signincantly throughout the system, the species equations can be approximated as Q,,,,,P,. = Q, P,.. +

Q,P,,, and Q,,,,,P,. = Q,,,P,,,,.

Note that the entrained How is several times larger than the source now, so the etfcct of the higher source tempentve is not very signincant. nese latter equauons permit the calculauon of the steam and att concentration at the outlet of the plume.

Conservauon of maas on a molar basis 6. = 6,, + 6. With 6 = puA, p = P/RT, and Q = uA, conservauon of moles can tie written P Q,/RT = P.Q,,,/RT,,, + P,Q/kT,. Sin:e the total pressure, P n the sarne for each, and the absolute temperature T only differs by a small amount, conservat;on of mass on a molar basis can be

'; proumated as Q. = Q,, + Q, With coctervauon of mass in terms of steam parual pressure,' P,

= (Q,,,P,,, + Q,P,,)/Q,,,, and Q,,, = Q,, + Q,,

- the outlet s. tam parust pressure is P,,,, = (Q,,P,,, + Q,P.)/(Q,, + Q,). Wntten in urms of the plume entrainment Iano r,, P,. = (r,P,,, + P,.)/(r, + 1).

I

ATTACHMENT 2 i

where; th a mass flow rate 6=

molar Oow rate p=

molar density Q=

volumetne Dow rate p=

mass denaty R=

gas constant T=

absolute temperature Subscripts:

a=

air sa steam ent =

entrained out =

outlet o=

source Values for densities and break flow rates at different times using the values for post refill and peak pressure are as follows:

h 1200see Mah8 p,,,=

0.13584 0.16325 lbm/ft' p, =

0.10487 0.13373 lbm/ft' P., =

46 60 psia P,,,

=

26.94 40,30 psia

( p,,,,,. p,)/p,,, =

0.2280 0.1808 200 4$

lbm/sec thg, a Qo = rh,,,, jp, =

1907 336.5 ft'/sec D = g QJp, p.)/p..

14.000 1959 ft*/sec8 Q,,, = 0 15 B "' Z" =

8855 4597 ft'/sec r, =

4.64 13.66 P., = ( r,P.,,, + P, J( r, + 1 ) =

30.32 41.64 psia Solung the equations for AP600 at 90 seconds and at the time of peak pressure (1200 sec.) results in the following:

Time sec

.ip/p Q,

Q,.

r, P.,,,,

ft'/sec ft'/see psia

--ummuummumuneunummuuuuuuuraummuummuunuumu 90 0.2280 1,907 8.855 4.6 30.3 1200 l

0.1808 336.5 4.597 14 41.6 i

ATTACHMENT 2 4.0 Entrainsment into a Negatively Buoyant Wall Layer The volumetric Dow rate entrained' is:

0.0979 v Or,"pw 4

(1 + 0.494 Pr

)" Pres M

where:

Z=

121 ft the height of the wall (deck to domel 8

Gr, a g(p,,,, p.)Z'/(p,,,v ), the Grashof number Pra the Prandtl number of the sublayer p/p, the sublayer Linematic viscosity based on the average d bulk and surft.cc values v=

of dynamic viscosity and density p., a the wall penmeter (nD) = 408.4 ft p, =

the total gas density adjacent to the liquid film surface p,.,=

the density of the ambient gas, the same density as the entrained gas.p,,

It is convenient to define the boundary layer entrainment ratio in terms of the entrained and condensed volumetric Cow rates:

r, = Q,dQ,,,,,

For entrainment into the boundary layer, the equations for conservation of mass rh. = rh, rh,w, ar.d on a molar basis 6,, = 6,,

6,,,,, can be developed as was done for the plume. The results are the important relationships for the steam partial pressure at the outlet of the walllayer:

for volumetnc now Q, = Q. - Q,,,,

the outlet steam partial pressure is P,. = (Q.P., - QwP,,,,,)/(Q - Qw),

in terms of th. plume entrainment ratio r,, P,

= (r,P,,,. P.)/(r,.1).

Values for densities and break flow rates at different times using the values for post. refill (90 see) and peak pressure (1200 sec) are as follows:

HJK 120RJes llahs 9,,,

0.13584 0.16325 lbm/ft' p, =

0.19020 0.20229 lbm/ft' pw =

0.10487 0.13373 lbm/ft' P.=

46 60 psia P,.. =

26.94 40.30 psia Pr =

0.81 0.83 1.23:10

l.24 10' lbm/sec ft p=

p=-

0.16302 0.18277 lbm/ft' 8

v = p/p =

7.55x10 '

6.78:10' ft/sec

- (p. 9,,Jp. =

0 4001 0.2391 Gr,= g(p. p,,,)Z'/(p,,,v ) =

~ 4.00a10d 2.97al0" 8

l + 0.494 Pr#' =

1.4293 1.4363 Q,, =.

5098 4004 ft'/sec rh, = ih,,,,, x,,, =

85

,40.5 Ibm /sec Q,,e = th,,/P,, =

810.$

302.8 ft%c r, = Q,JQw =

6.29 13.22

P.,,, = (r,P,e P,,,,,,V(r, l) =

23.34 38.69 psia 3

w jb

ATTACHMENT 2 Summary Tables:

Time.

P.,,,,

P,,,,,,,

v ap/p Gr, Pr Q,.

see psia psia ft'/sec fi'/see mmEmmum

-mummumummum 90 46 26.9 7.55 10' O.4004 4.00x 10

O.81 810.5 d

1200 60 40.3 6.78 10 '

0 2391 2.98 10 O.83 302 8 Time.

Q,.

tw P,,..

6 Vu sec ft'/see psia ft ft' unummmuumummmmmmu

--ummmmuumu 90 5098 6.3 23.34 2.2 63.200 1200 4004 13.221 38.69 2.3 65.500 5.0 Effect of Entrainment on Mass Transfer Rate The condensation heat flux for given total pressure, steam partial pressure, and bulk to-surface temperature difference is determined and used to calculate the influence of the concentration differences..

The bulk to-surface temperature difference is:

29,,3ss 1200 sec Tw =

244.2 267.7 T T,,,,,

=

165.1 232.2 T AT = (Tu T,,,,,) =

79.1 45.5 7

The refill time phase, from 30 to 90 sec., has no source, but does have a wall layer. Refill is represented by its end state that is assumed to hase the same conditicens as calculated at 90 sec, except that without a plume the steam partial pressure and heat flux at the top is the same as the ambient bulk conditions.

The steam partial pressure values at the top, middle, and bottom correspond to the steam partial pressure out of the plume, the bulk steam partial pressure, and the steam partial pressure out of the wall layer.

The aserage heat flux is a simple, unbiased average of the top, middle and bottom values, that is 4 = 4,,/4 +

4.4 + 4.A Time P.

AT P,..,

P,,.

P,,..

4,,3 4.

4.

A$erage 2

i B/sec ft' see psia T

psia psia psia B/sec ft B/sec ft B/sec ft umnu m muunummuummuumumumuumunung muummmuummuummmmmmumumummmumummmeummmuuuuman refill 46 79 26.9 26.9 23.3 1.85 1.85 1.4 1.74 90 46 79 30.3 26.9 23.3 2.25 1.85 1.4 1.84 1200 60 43 41.6 40.3 38.7 1.5 1.4 1.3 1.4 Discuasion The results in the abose table show a 6% reduction on the net heat transfer dunng refill and less than 1% effect on net heat transfer during the 90 to 1200 see time period.

4

AT'l ACithlENT 2 6.0 Boundary Layer Thickness and Volume The thickness of the negatively buoyant walllayer can be calculated from the integral equauons presented by Peterson'.

o

= 0.565(1 +0.494 PrM)uio z

(3) g or,v2'Pr ms The equation can also be integrated over its height, with the simplifying assumption that all properties are constant over the height, Z. This assumption is reasonable since the Prandtl number only changes a few percent over the range of conditions inside containment, and the only other parameters are Ap/(pv') which is estimated to change less than a factor of 2 over height, and when raised to the 1/10 power has only a 79r effect.

Consequently, the product of the integral and the circumference gives a reasonable estimate of the boundary layer volume that can be used with the entrainment rate to estimate transit times, or fill time.

The product of the circumference and the integral of Equation 3 is H

, 0.565(1 +0.494Pr /3)1/30(v /g)1/ 0nD 2

3 og (A p/p)'I'0Prms (4) 2 83 0.565 n (1 +0.494Pr /3) /20(v fg)ilioDH 1.7

( A p/p)ll!'PrMS Evaluating Equation 4 with the values from Section 3 29.,3gs 1200 nec geha I4 =

0.81 0.83 v=

7.55 x 10 '

6.78 t 10 '

ft'/sec j p. p,..)/p. =

0.4001 0.239I I + 0.494 Pr"' =

1.4293 1.4363 V (Equauon 4) =

63436 64553 ft' Summary Table:

Time, see V, ft' Q,.. ft'/sec Booundary Layer Fill Time. sec V/Q,,

90 63436 5098 12.4 1200 64553 4004 16.1 5

ATTACHMENT 2 i

i 7.0 Sublatee Penetration Time Another measure of the response time of the structure temperature to a change in the environment is the subla)er penetration time. Dat is, the time it takes for steam to diffuse through the laminar sublayer, where most of the mass transfer resistance is located. The transient diffusion equation:

l 6' BA' = a'A' (5) 81 = o' a'A i

OL Oy D, t at '

ay *2 with the substitutions:

A = 0.0' y = 6,y' t = tt' where i

e=

molar density I=

time l

y=

distance along the normal to the surface 6=

boundary layer thickness D, =

air steam gas diffusion coef6cient t=

time constant value at a large distance from surface

.

• =

dimensionless variable If the time constant is denned t = 6,8/D,, the coef6cient on the left side of the dimensionless equation = 1, as required. The mass transfer sublayer thickness, 6. is related to the heat transfer sublayer thickness,6. by Nu/Sh = (Pr/Scf. The heat transfer sublayer thickness is 6, = h/k. Other assumed values are; h

1200 anc.

8 h=

2.61 2.51 B/hr.ft F k=

0.0164 0.0173 B/hr ft F D, =

0.537 0.464 ft'/hr Pr =

0.81 0.83 Sc =

0.51 0.51 6, a h/k =

0.0063 0.0069 ft 6, = 6,(Pr/ScP'8 =

0.0073 0.0081 ft t = 6,'/D, =

0.357 0.509-see Consequently, the sublayer penetration time is on the order of I sec or less. This is very rapid in comparison to the structure time constants that are on the order of 100 sec, and the system pressurization time constant that is on the order of 1000 sec, Even the boundary layer Oil time of 16 sec is short compared to both the structure and pressure time constants.

s.o meterene.

.1 P. F Peterson," Scaling and Analysis of Mixiniin large Stratified V0lumes" /nternationa/

/ournal o/ Neal and # ass Trans/er, Vol. 37, Supplement 1. 'pp.97-106,1994.

6

ATTACHMENT 3

?

Turbulent Boundary Layer Analytical Model I.

Purpose:

I Une an analytical model of a turbulent boundary layer to predict boundary layer thickness and temperature / concentration profiles for AP600 containment

{

II.

Key Assumptions l, Surface is senical flat plate Containment shell radius of curvature is large 60 it can be treated locally as a dat plate

2. Turbulent velocity, temperature, concentration beundary layer profile Bis is appropnate since boundary layer is turbulent within a few feet of the top of the containment shell

- i

3. Bulk fluid is quiescent His is true after blowdown period since the break source trarmtions from jet to buoyant plume and bulk containment area is large relative to plume / boundary la)er

4. Condensate film es impermeaLle to non condensible gases Bis is conservative since adsorption by the Olm removes air from containment 4

volume which enhances heat / mass transfer of steam

5. Condensate film is stationary relative tu gas boundary layer i

his is appropriate since condensate film selocity is smaller than gas boundary layer velocity, and conservative because a moving film enhances heat transfer

6. Suction effect at wallis neglected Bis is conservative because suction thins the boundary layer

7. Dermal boundary layer thickness same as concentration boundary layer thickness His is appropriate since Le* - 1.0

8. Saturation conditions esist at film surface

. His is appropnate since steam is condensmg at the film surface Ill.

References Analyus is largely based on:

1.

Eckert and Jackson," Analysis Turbulent Free Convection Boundary Layer on a Flat Plate,"

NACA Report 1015,1951.

2.

Conadini,

• Turbulent Condensation on a Cold Wallin the Presence of a Non Condensible Gas," Proceedings on Nuclear Reactor hermal Hydraulics, Vol. I,1983.

3J Kakac and Yener. Convecuve Heat Transfer,2"' edition, CRC Press,1995.

Analyucal approach is nicely summanred by:

Kays and Crawford, Convective Heat and Mass Transfer,3rd Edition, McGraw Hill.

4 I

RSat'LEW a0 Lev 04ay LAyga j:

F k---=-'7wr----

v

- - - - v

-_.______m.

1 i

ATTACHMENT 3 l

l I

(

IV.

Boundary Layer Profiles i

ne boundary layer profiles, used by Eckert and Jackson, are based on experimental data for

}

turbulent boundary la)ers!

l Boundary Lay er Velocity Profile (ref. 2, eqn. 24) i r

u = U(1-q)* n where n = 5 u = local velocity in boundary layer 6 = boundary layer thickness r a coordinate direction normal to conden sin g surface Boundary Layer Temperature Profile (ref. 2, eqn. 25) r T - T. = (T,,, - T. ) 1-9 7

k where,.

i T = temperature

. ~ Boundary Layer Concentration Profile r

i3 i

0 - C. = (C,,, - C. ) 1-q l

(

/

i

+

where.

C = concentrabon

?oudary Layer nickaess (ref. 3, eqn.10.121b) 6 = Bz" i

where, B,n are constants to be deter mined Manimum Velocity in Boundary Layer (ref,3, eqn.10.12ia) i U= Az"

. w here, A,m are constan u to be det er mined -

?

! R DDL LFT 90L'%DAA1 LAvte -

2

. ATTACHMENT 3 V.

Governing Equations '.

Momentum Equation d j,'u'dr

= 9J,,p(T - T.W ",p dz

where, t a shear stress at condensing surface S = cspansion coefficient p = density g a local gravitational acceleration Energy Equation d j,'u(T - T. )dr ag, dz pC, Cp = specific heat at constani pressure M tet LDft tol%044Y LAis2.

3-

ATTACHMENT 3 Containment shellinside surface r

j, u

Z Bulk Fluid C*ud

""""" T~

9w i...'

C = concentration of air

.Y'

.... C.

T = temperature T,on q, = heat flux U.,

U Turbulent Air Steam Boundary Layer a

Laminar Condensate film FIGURE 1 r

q#

L Control Volume n

w S ',

u Z

FIGURE 2 n..tum.m..,

un.

4

.~ -_- -.

ATTACHMENT 3 Consersation of Mass Equation Not used in this calculation since we are not calculating entrainment solumes/ rates, but rather, temperature /concentsation profiles.

Boundary Conditions

- Thermal and concentration boundary conditions are known for LST tests at surface and in bulk locations.

VI.

Boundary Layer Momentum Equation Development Wall shear stress in momentum equation is modeled using correlation for forced turbulent convection, Eckert and Jackson argue the t. is similar to forced convection in the near surface

- region and can be represented as follows:

- = 0.0225 U6* *

~

t*

pU8

.v.

s

where, y = kinematic viscosity 3%

r y t, = 0.0225pU'g where U is a charactenstic velocity interpreted by Eckert and Jackson as the maximum velocity in boundary layer.

The integral momentum equation then becomes:

d J,'u'dr x

=gfp(T - Tfr - 0.0225U' 1

,U6 dz

~

Applying turbulent velocity and thermal boundary layer profiles, it can be shown that:

f,'udr=6jj U(1-q)* qX dq = 0.05231560' s

and 8

f,'(T. - T) dr = 6j,'(T. - TM1. q ) dq = g(T. - Tu)

X The boundary layer momentum equauon becomes:

dx (0.052315U'6). gp(T. - T.,)8 - - 0.0225U' U6, n natuur notenv utsa E

ATTACHMENT 3 t

Applying Reynolds Analogy for heat / momentum transfer:

h f

= 8-E.

(ref. 2. egn. 5) pC,U 2 where

.5 f, a local fncton factor = 0.0451 ; (ref. 2, eqn. 32)

,U6 l

Ein ratio of turbulent eddy diffusivity of heat to that of momentum h a heat transfer coefficient ftom Colburn Analogy:

Es =,o N (ter. 2, egn. 6) r where Pr = Prandtl number Therefore,

.g

.g

~

h _, 0.045 p.X = 0.0225 1 Pr'M

[

v pC,U.

2

.U6

.U6 Now, since., 4w = A(T. -T,) heat flus can be modeled as q

Asurf

= 0.0225(T. - T,,,f k Pr'M follows:

where A,s a heat transfer surface area

Now, u(T.T )dr = 8 U(I-afa (T -Tsurf)41-a da = 0.03663(T -Tsurf %U 0

'O De boundary layer energy equation becomes:

f(0.03663(T -Tsurf)6Uj=0.0225Pri(T *;Tsurf)U Substituting eapressions for U and 8 into boundary layer momentum and energy equations, differentiating the resultmg equations, solve for esponents m and n by matching exponents. His -

procedure results m m=l/2 and n=7/10 which can also be found in teference 3, page 335,

' E 46dlAT ME 4D48 T LAllt -

6

l I

ATTACHMENT 3 t

Therefore:

1 i

V t

- U = Azy2 i

and 6 = Br'80-Substituting the expressions for U and 6 into bounday layer equations and performing the

' differentiation.'we obtain:

[

0.052315 A')= 0.125gD(T. - T,)- 0.0225 A B% $v*

f f

ard N 'NvN 0.03663AJPrb = 0.0225A B

4

?

Solving for constants A and B. an expression for boundary layer thickness can be obtained:

6 = Br%' = 0365t(Orz) N0(Pr)'N5 1 + 0.494 Pr (ref. 2. eqn. 36)

~

The above equation agrees with that obtained in Peterson's paper. " Scaling and analysis of mixing in large stratified volumes". Int. J. Heat Mass Transfer, vol. 37.1994, equation 18.

From the expression for 6. the s elocity, thermal and concentration boundary layer profiles can be calculated, w here; Gr, = gS(T. - T, )z'(ref. 2. eqn. 29)

V, I

r Vll.

Boundary Layer Thickness Results AP600 Prediction (for thermodynamic properties based on LST test 217.1)

Based on' AIR propenies (ref. Appendix of " Principles of Heat Transfer" 3" Edition. Kreith) and noung S = 1/T.:

3 32.2 {a (230*F-188'F)r' 690' R '(110 ft)'

i

Gr =

= 3.7 s 10

(0;84a10#a E

6 = 0365(l 10ft)[3.7 a10l(0.71 "(l + 0494(0.7)2'8 = 303 in.

l i

n e si ttvt sopose r t.Avta

-7

+

.1

'u"

.,..._.E'cy.v_,..

__y

,.,_..,_,...,.,.7,.,g..-.

,,m,...m_.

...,,.,. ~..,,

s l

ATTACHMENT 3 i

)

l t

Based on ST11AM properties:

i 322(230-l88) 110)'

I Gr =

= 3 4 x 10" (0.87 a 10 )#

4 8 036S(110ft)(3.4 10")*0(1.ll"[: + 0 494(1.1)2is g-liio = 23 9 in.

l I

i For LST Test 217.1:

LOCATION T.

Ts Pr(ast) v iair)

Cs C.

d E

230'F 180'F 0 70 0 64 s 10 0.79 0 67 ft' hec

)

based on AIR properties:

rgi 32.2(230 - 1881 690;(13.2)3 Cr =

= 6.4 x 10'i

(

(0.84 x 10 ),

d i

at Point E in LST:

7 6 = 0365(132ft(6.4 x 10")N'(0.70)T5 1 +0.494(0.70)

= 6.9 in.

i

- Based on STEAM nronerties (Pr = 1.10, y = 0.87 's 10 ft'/sec):

d

. fl1 \\

322(230 -1883 690s(13.2)'

5.9 x 10" Gr

(0.87 A y) 2'j,,,

i at Point B in LST:

j e

a e

o 9

1 f

i

-- n estuwt owsonat wea '

i

-. g e

_.._4,

_../,.

........,s.

_...,_...,,__-r_.

v.,. ;

t i

ATTACHMENT 3

\\

For LST Test 220.l:

LOCATION T.

T Pr(aari v (air i C

C.

E

Co*F IS$'F 0 70 10

10' It%ec 0 87 0 72 Based on AIR properties (since mostly airl:

322(200 -155 660 >(132)'

Gr --

= $.0 a 10u 1

(1.0 s 10)#

at Point E in LST:

8 0365[13.2ft{$.0 x 10")~ 0(0.70f 81 + 0A94(0.70)N

=7.lin.

N

Vill, Concentration Profile Results Concentration pro 61e and integrated average in boundary layer are calculated from turbulent analytical model for LST.

Concentration at surface determined from inside surface temperature data and applying saturated conditions near surface.

DOME y;=

• B

+C

• D

,g o,....

FIGURE 3 LST Measurement Locations n..um seem run 9

I

. ATTACHMENT 3 j

6 LST Test 220.1 P,,,,i = 32 psia, m = 0.5 lbm/see j

I t

+

Locanon Te

T.

Cs C.

{ 8L j

(measured)

(measured)

(Calc)

(measured) j IC"IC)

(*F)

('F)

}

0 77 0 34

() 39 l

Dome 1NO A

180 230 0.77 0 44 04R f

230 D

C 177 230 0 78 0 48

[

i 230 D

E 155 200 0 87 0 72 0 74 j

~ LST Test 217.1 P,,,,j = 43 psia, m = 1.0lbm/sec.

f

{ *L l

Location T

T.

C, C.

(measured)

(measured)

(calc)

(measured)

( p)

( p)

- (calc) 0.73 0 33 0.38 l

Dome 200 A

210 260 0 67 0.33 0.39 B

-207 260 0 69 0 39 i

I C

20$

260 0.70 0.395 D

198 260 0.74 0.40-E 188 240 0 79 0 67 0 69 l

Notes:

1. ' C,,,is calculated from applying Dalton's law of parnal pressures, assuming saturation conditions exist at the condensing surface, and using measured surface temperatures and total pressure from LST tests.

[

2.

Dg, w hich represents the average air concentration in the boundary layer, is calculated form performing an integrated average whin isults in Da = (C, + 7C.)/ 8.

3 3.

Refer to inside wall temperature data (Table 4.81 for LST test 217.1 and Figure 4.116 for LST test 220.1) in " Final Data Report for PCS Large 5: ale Tests, Phase 2 and Phase 3", July 1997, WCAP.

14135, Rev. I for surface temperature data.

Bulk fluid temperatures shown in above tables represent spatially averaged values based upon attached 4.

LST time averaged temperature profiles for LST tests 220.1 and 217.1 at quasi steady ccnditions.

c Boundary Layer Cemeestrodes Pronle Results. LST IL Companson of C, and Ci shows that the differencein concentrauon is small(wis.sn 15%)in the radial thorizontal) direction for LST. This along with temperature profile data indicate that LST is

-i well. mined in the radial direcuon throughout the above deck region.

i The bulk fluid temperature in both honzonta! and vertical directions shows little difference (i.e. a few.

- degrees) between the dome region and region D. There is however about 20 F difference in the butt -

nmtsm omw ay tuna -

10-

~

n

. ~.,

y.o_,..

,.-,-i,__..__.w,_,m,..,m

,e

,.mv..2,

..y.. -,,

+.,---

cw

_. _.__ ~... -.._

t t

ATTACHMENT 3 i

temperature between regions D and E for LST test 217,1 and about 30 F difference for LST test 220.1.

De data indicate some level of strat 6 cation between regions D and E ahich is more pronounced m i

LST test 220.1. Since the LST does not have a now connection from the simulated 50 compartment.

there is no global circulation. As a result, the strat:6 cation below the source elevation is not suTnsing.

3.

Region E temperature / concentration is notably different than the regions abose. Dit indicates an interface or Fradient region exists between the higher temperature. steam nch upper :egion (abose the plane of the break) fed by the buoyant plume, and the lower temperature, air.nch region fed by the wall i

i bound.try layer.

1.

Turbulent boundary layer miting is signi6 cant such that boundary la>er average properties are nearly at bulk conditions. It is espected that this will be the case for AP600.

Boundsey Layer Analytical Model Resulta. Boundary Layer Tidekness 1.

De rnanimum boundary layer thickness calculated from the analytical model for LST turbulent houndary layer - 7 inches. (LST 217.1 and 220.1) 2.

De maximum total boundary layer thickness calcu*ated from the analytical model for AP600 at similar thermodynamic conditions - 31 inches.

3.

De calculated boundary layer thicknesses are conservative because suction effects due to steam condensation at the wall were not included, it is well known that suction reduces boundary layer thickness (refer to Schlicting. Boundev Laver Theorv). Derefore, actual boundary layers should S thinner than calculated.

1 De boundary layer horizontal pro 6lc ts rather " flat"due to miting effeca of turbulence.

Consequently, most of the horisontal boundary layer gradient is contained in the much smaller region near the condensing surface.

h t

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l LST Temperature Profile - Test 220.1 I "I t

RC062,220.I,11.6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />

_ t.<

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l Im l

e 4

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4 I

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t i

l a

l ACRS 12/97 - ABOVE DECK F 18 i

a i

LST Temperature Profile - Test 217.1

,1i RC052,217.1. I1.6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />

- (c A

5 R

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t w a P ohsts ACRS 12/97 - ABOVE DECK F 19

t NRC FSER OPEN ITEM FSER 01 480.1066F (OITS 6188)

The position):$g of the MSLB break location away from its originallocation at the top of the steam generator downward to the vicinity of the operating deck and into the center of the dome carries the following items of non conservatism: (1)the removalof an asymmetric break. (2) a condition for more mixing above the operating deck, (3) the elimination of the stratification issue, (4) the artificial generation of a well mixed condition in the dome region, and (5) the availability of two connections to the below-dock regions as compared to only one with the break in the top location.

The combination of these distortions stands a good chance of providing unrealistic computational results compared to the realistic break location. The MSLB is tne limiting accident for the peak pressure in the AP600 therefore an analysis of the MSL6 with the break location near the top of the sieam generator is required.

Response

The approach taken to bound effects of circulation and stratification for a main steam line break (MSLB) account for the momentum of the break flow that is released in the above deck region. The MSLB modeling approach considers the offsetting conditions of a) the elevation of a break in the main steam line above the operating deck; and b) the momentum available to mitigate the potential for stratification.

To put the stratification question into perspective, for post blowdown (that is, low momentum) LOCA sources from elevated release points, data from facilities in the industry containment test Jatabase show that stratification can exist between regions above and below the source. An MSLB introduces momentum into the above-deck vobme that tanges through the transient from 4 to 3 orders of magnitude greater than the momenturn intro:luced by the post blowdown LOCA at the top of the steam generator compartment (Reference 1, Section 6.5.2).

In the following discussion LST results provide insight into the effects that break source elevation and momeisturn have on distrit ition of steam and thus containment mass transier rates. Based on the MSLB test data, it can be concluded that the momentum introduced by an MSLB above the operating deck would homogenize the above deck steam distribution in AP600. Such homoganization would occur, with releases anywhere between the operating deck and the top of the steam generator, directed horizontally or vertically.

460.1066F 1 3 Westingh0tist

NIC FSER CPEN ITE'1 Margins relative to these effects are included in the MSLB Evaluation Model. These margins include a) neglecting mass transfer enhancement due to forced convection; and b) elimination of floor surfaces for convective heat and mass transfer.

The following provides specific responses to the five points identified in the open item.

The justification for the bounding MSLB Evaluation Modelis summarized in Reference 2 Section 9.4.2. The discussions below consolidate information and provide supplemental LST data.

Summary Responees to Open item Concerns The use of the lumped parameter modelin a manner which results in a homogeneous above deck region and limits steam access below the operating deck is reasonable and bounds realistic containment atmosphere steam and noncondensible vertical distributions based on the supporting information provided below. The following responses are provided for each of the 5 concerns identified in the open item:

Response to Open Item Concem (1) 'the removal of an asymmetric break' Due to the momentum of the AP600 MSLB break source, the entire above-deck region would be nearly homogeneous in the AP600, regardless of an asymmetric break location, as determined by a Fr, et!terion developed for enclosures based on the LST.

Additionally, all above deck surfaces would have a higher mass transfer than that predicted by the use of only free convection in the Evaluation Model. Wall surfaces toward which a break is directed would have a higher forced convection enhancement to mass transfer. Forced convection is neglected by assuming only free convection on internal heat sink surfaces and the intemal surface of the PCS

shell, Response to Open item Concem (2) *a condition for more mixing above the operating deck

• The above-deck region in AP600 would be nearfy homogeneous during a MSLB due to the high source momentum, it is reasonable that the Evaluation Model predicts a homogeneous steam concentration above the operating deck.

Response to Open Item Concem (3) *the elimination of the stratification issue' 440.104eF 2

e iii l

NRC FSER OPEN ITEM m...

In fact, the Evaluation Model conservatively calculates stratification between the above and below deck regions, limiting steam access to the below deck heat sinks which are important for MSLB pressure mitigation, in the lumped parameter model, below deck, steam is only driven by vessel pressurization, not by global circulation, due to the simplifying assumption of momentum dissipation inherent within a lumped parameter volume.

A sensitivity calculation (Rc!srence 2, Section 9.4.3) has been performed to quantify the si act of stratification above and below deck in the Evaluation Model Using the lumped parameter MSLB model with the break boundary condition placed in the CMT North compartment, shows that better access of steam to below d'ck heat sinks produces a reduction of 1.6 palin peak pressure relative to the Evaluation Model.

Response to Open item Concem (4) "the artificial generation of a well mixed condition in the dome region' The above deck region in AP600 would be nearly homogeneous during a MSLB due to the high source momentum, so that it is reasonable for the Evaluation Model to predict a homogeneous steam concentration above the operating deck. The nearly homogeneous condition above the operating deck in the Evaluation Model is not an artificial condition.

Response to Open item Concem (5) *the availability of two connections to the below-deck regions as compared to only one with the break in the top location

• The MSLB circulation differs from that in a LOCA DECLG. In the LOCA DECLG, releases from low in containment rise through the affected steam generator compartment into the above-deck region, and circulate down through openings such as the unaffected steam generator compartment. Such circulation has been called global, or large scale, circulation, in such a LOCA scenario with global circulation, one steam generator compartment has upflow while the other steam generator compartment has downflow.

For the MSLB Evaluation Model, the placement of the break node togethat with lumped parameter momentum formulation eliminates calculated global circulation.

Therefore, all the openings, including those'.into both steam generator compartments, pass flow only due to pressurization of containment and 440.1046F.3

$W J

~

i NRC FSER CPEN ITEM condensation on below deck heat sinks. Therefore, the placement of the break and its effect on the availability of paths for global circulation does not lead to nonconservatism in the Evaluation Model.

I i

Supporting information The MSLB Evaluation Modelis based on an understanding of AP600 behavior derived from test data. Test data includes (a) LST stratification data to assess the influence of momentum induced circulation; and (b) LST data for condensation on the above-deck shell surface. The understanding of the potential for containm6nt atmosphere stratification in the presence of high momentum releases is combined with known lumped parameter biases (Reference 2, Section 9.C.3.3) to establish a conservative model accounting for the potential effects of steam and noncondensible distributions.

Mass transfer is the dominant containment heat removal mechanism for a Design Basis Accident. The primary energy removal process is condensation on intamal containment i

surfaces, which is affected by the distribution of steam and noncondensibles within the containment. Since the local noncondensible concentration is equal to the total vessel pressure minus the local steam concentration, the discussion that follows focuses on steam distnbutions.

AP600 MSLB Boundary Conditions AP600 typical MSLB mass and energy release rate boundary conditions are provided in Reference 2 Section 4.5.2.2. Postulated break locations are discussed in Reference 2 Section 9.4.1. The open item concerns are related to the postulated release location of a MSLB in the pipe as it exits the top of the steam generator (see Reference 2 Figure 9-36).

Volumetric Froude Numberin LST The Froude number is a ratio of momentum to buoyancy effects. The definition of Froude number related to momentum effects with a finite height leads to the " volumetric Froude number," Fr,, which considers the vessel height as a characteristic length and uses the difference in density between the incoming steam and the average, bulk mixture in the above deck region (Reference 1' Section 6.5.1.2). The volumetnc Froude number has been proposed by Peterson for use as a criterion for whether the momentum from a jet will homoge 9 :e a volume, t

I

Cl 1

NRC FSER OPEN ITEM

)

'L Peterson developed an infinite pool stability enterion, above which the Froude number would indicate that the pool could be assumed to be homogeneous. Peterson's stability limit would be overly conservative for appli0ation to an enclosure, in the infinite pool, the buoyant source rises to the upper surface of the pool and travels outward; therefore its momentum and turbulence essentially leave the system, in an enclosure, the high momentum jet impinges on the opposite surface which redirects the flow parallel to the surface. The high momentum and turbulence are therefore retained in the system and can drive circulation below the break. Data from the LST are therefore used to establish a Fr, criterion, which can be applied to enclosures, to indicate the conditions under which a volume can be assumed to be homogeneous.

The LST MSLB data are from tests with an elevated small diam 3ter pipe: test 222.3 (jet 6 feet above the operating deck pointed horizontally) and test 222.4 (jet 6 feet above the operating deck pointed up). Those LST tests show the effect of the momentum of an elevated source of steam, both direction and magnitude.

Volumetric Froude numbers in the LST range down to Fr, = 0.29, as shown on the fieference 2, Figure 91, with AP600 ranges shown on the attached Figure 480.1086F.

1. The ordinate is the " measured local steam pressure ratio

• at a particular elevation divided by the steam pressure ratio calculated assuming a homogeneous mixture. Data from two elevations are presented: the E elevation is at the operating deck level above the grating; and the F elevation is within six inches of the bottom of the vessel. The ordinate is a measure of the degree of homogeneity: the closer the value is to 1.0, the more uniform is the vertical gradient. Values less than 1.0 indicate that there is less steam (and thuS more noncondensible) at that elevation than would exist if the mixture were uniform.

Considering the LST as an enclosure test, a criterion on which to base the assumption of momentum induced homogeneity, when there is an elevated break source, can be determined. The data show that down to the lowest value tested,0.29, the above deck region is essentially homogeneous. (Data showing vertical gradients of temperature and steam from elevation F up to the dome are discussed below.) Therefore, for values of Fr 2 0.29 and an aspect ratio similar to AP600, the above deck region can be v

considJted to be homogen?Ous, it is also evident in looking at MSLB ordinate values (and vertical gradient data discussed below) for the F elevation in Figure 480.1086F 1, that the test vessel is effectively uniform down to the F elevation, well below the operating deck. Therefore, for values of Fr, a 0.29, the data suggest that a significant influence of circulation forced by jet momentum is felt below the operating deck in the LST enclosure. However, such 440.1066F 5

j NRC FSO OPEN ITE.1 i

il forced circulation of steam below the operating dock is not included in the Evaluation uodec as discussed iaior.

j i

LST Vertical and Horizontal Gradient Osta i

Vertical temperature and steam concentration gradients in the LST MSLB tests are shown in Reference 2, Figures 9 29 through 9 34; Data in Figure 9 31, at the lower end of the MSLB LST Froude number range, show that the steam concentration at elevation l

F, below the operating deck at the vessel bottom is consistent wdh a momentum source j

forcing a negatively buoyant jet to penetrate below the deck, as shown qualitatively in l

Reference 2 Figure 9.C.1 11b. Thus, regardless of whether the jet is directed _

j horizontally or vertically, data shovtthat steam is driven by momentum to penetrate below the LST operating dock sufficiently to homogenire the entire test vessel, including the below deck region.

l i

Hortrontal temperature gradients through the LST vessel at 5 elevations above the operating deck are shown in the attached Figures 480.1086F 2 through 480.1086F 5 for the tests 222.3 and 222.4. The two tests both have the source at an elevation 6 feet

. above the operating dock from a small diameter pipe to provide the higher source momentum. Shown for the steady state phase of each test are: the outside wall and inside wall temperatures; temperatures 1 inch away from the wall; and temperatures across the vessel from the thermocouple rake mounted withlo the vessel volume. The dimensions of wall thermocouples and the "one inch wall mounted thermocouple" are shown in Figure 480.1086F 6.

As can be seen from the data figures, the vessel mixture temperature is nearly uniform l

hortzontally between the thermocouples one inch from the walls at each elevation. Such t

uniformity is present regardlese of whether the break is pointed up or toward the wall.

Thus, the momentum introduced in the LST eliminates horizontal gradients outside the relatively thin laminar sublayer at the wall, it has been shown for low momentum (LOCA configuration) conditions that the majority of the hortaontal boundary layer concentrat6on gradient occurs over much less than 1 inch at the operating dock level in the l.ST, without considering the suction effect. (See 1

response to FSER Open item 480.1085F. Those calculations for the LOCA configuration conservatively overestimate the thickness of the boundary layer for MSLB -

configuration since the higher momentum would lead to higher near wall velocities which

- would tend to thin the boundary layer.) The MSLB data confirm that the concentration profiles for the MSLB are of the same order or l'ss than the LOCA configuration, since i

e the radial temperature plots show the gradient occurs over less than 1 inch from the wall surface..

i l

400.1066F 4 -~

Y6 yr-+-,v.-,,-,...,-.i-,

w-.4,-+

5yw.

v--,--

<6..,

r-.,-.,-..r w-

-.m im

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wmio=

e, w

4-.-

r~+e m e

NRC FSER OPEN ITEM n,

t Volumetnc Froude Numberin AP600 The Fr, criterion for enclosures developed from the LST is used to assess the influence of momentum during the AP600 MSLB transisnt. The data show that for Fr, a 0.29, vertical and horizontal gradients above the operating deck would be small due to large momentum induced entrainment and circulation Induced by the momentum impinging on the enclosure walls. The LST volumetric and jet Froude numbers as a function of time for the MSLB are shown in Reference 1 Figure 6 3. The AP600 Froude number is greater than 0.29 for the first 390 seconds of the transient, suggesting that the above-deck region in AP600 can be assumed 'o be homogeneous throughout that time.

From 390 to 570 seconds (the time of peak pressure), the value of Fr, continues to gradually decrease to a value of 0.15, since the source momentum is gradually decreasing. In a quasi steady condition when momentum is introduced into the vessel, the fluid contained in the volume circulates at a rate such that the parasitic losses, friction on the walls in this case, balance the momentum. This process of momentum-driven circulation results in a monotonic reduction in circulation with reduction in momentum, that is, there would not be an abrupt change in the degree of mixing over the range of Fr,.

The time frame for changes in the degree of homogeneity in the above-deck region would be related to the volumetric time constant fnr replacing the air steam mixture with the pure steam source. Assuming the region which would be affected is the upper half of the volume in the above deck region,700,000 cubic feet, and a source flow at 500 seconds of 1225 cubic feet per second, the time constant is 571 seconds. The time constant is much greater than the 180 second duration beyond the test based Fr, criterion. In addition, entrainment into the downward flowing walllayer occurs ti,roughout the transient, providing mixing over the height of the above deck region.

Therefore, the momentum introduced by the MSLB through the time frame of interest can be assumed to be sufficient to prevent a significant amount of stratification from developing. As a result, the AP600 MSLB above-deck region is sufficiently homogeneous to support the use of the lumped parameter model discussed below.

LST data also suggest that significant circulation into the volume below the operating deck (20% of containment frec volume) may occur in AP600, such that enough momentum may be available to homogenize a significant fraction of the entire containment. Since methods are not available to quantify the amount of momentum-driven circulation below the operating dock in AP600 based on smaller scale tests, the Evaluation Model does not take credit for momentum-driven circulation below the l

operating cock, as discussed below.

480.106 # 7 O

l e

9

NRC FSER OPEN ITEM i

The effects of momentum on condensation via forced convection are also discussed below. On the basis of fet Froude numbers in the LST (Reference 1, Figure 6 3), much i

of the jet height may be considered a forced jet and the momentum effects on i

convective transport cannot be neglected relative to buoyancy forces. Thus, it is expected that the condensation ratis would show forced convection enhancements in the LST. Based on arguments presented above, the AP600 would similarly show forced convecf m hancement throughout the MSLB transient.

LST Condensation Rate Data The LST data has been used to derive condensation rates on the internal shell surfree (Reference 3, Section 3.9) A comparison of the data from the MSLB configuration for LST tests 222.3 and 222.4 is given in Reference 3, Figure 3.9 5, represented as the ratio of the ' predicted Sherwood number using free convection correlation" to " measured Sherwood number" as a function of elevation. The data show that tne measured LST Sherwood numoer is significantly higher than predicted by tree convection over nearly all of the vesssi surface. TM forced convection improvement ranges from a factor of 1 to 10 in the LST, with the higher value c:: curring at the elevation of the jet for the horizontal orientation, or at the underside of the dome for the vertical or;entation. The MSLB condensation data are consistent with the expectation of s!gnificant forced convection contribution based on the volumetric Froude numbers.

Although LST data show that significant forced convection enhancement may occur due to the break source momentum, only free convection is c,3di4d in the MSLB Evaluation Modw;.

Bounding Lumped Parameter Evaluation Model Biases are included in the MSLB related to circulation and stratification, including a i

contarvative treatment of mass transfer correlations during the high velocity (momentum) MSLB releases. The following summarizes the r6!sted biases which have been incorporated into the Evaluation Model and then provides supporting information on lumped parameter modeL'ng of the MSLB.

The Evaluation Model assumes only free convection on intamal containment heat sinks, which conservatively neglects the enhancement to mass transfer from forced convection (high velocity) that would occur buring an MSLB.

Test data discussed above provide evidence that the high momentum introduced during a MSLB above dock would homogenize the atmosphere above deck, as well 4ao.ios s a

s I

NRC FSER OPEN ITEM as drive some source steam below deck Lumped parameter biases in: a nearly homogeneous above deck steam concentration; and limitation.a steam access to heat sinks below deck as follows.

The MSLB Evaluation Model calculates a nearly homogeneous steam concentration in the above deck volumes. As discussed in Reference 2, Section 9.4.2, the lumped paramster formulation inherently assumes that momentum is dissipated within a node. Since momentum is dissipated within the volume to which a boundary condition is attached, C ly buoyancy forces are modeled, and there is no driving j

force in the model for L,;ulation below the assumed break node.

The lumped parameter MSLB evaluation model predicts a nearly homogeneous steam distribution above the deck as shown in Reference 1, Figure 9 60. Such a homogentcus condition is consistent with the volumetric Froude number criterion for homogeneity developed from tests; thus the above deck region can be assumed to be homogeneous for containment pressure calculations. From the figure, after an initial 10 second adjustment period, nearly homogeneous above deck steam pressure ratios range over time from 0.5 to a 0.75.

Steam access to heat sinks below deck is limited by suppressing the effects of global circulation, as follows. The above deck steam concentration of 0.5 to 0.75 can be compared to the concentration in below deck compartments, which generally ranges from 0.3 to 0.38, up to the time of peak pressure (Reference 1, Figure 9 60).

The large difference in steam concentration between above and below-deck regions results from the lack of global circulation within the model.

The transient steam concentration in the CMT South volume is noticeably delayed relative to the other below deck compartments. Reference 1, Figure 9 60 show that CMT South (volume 104) initially remains at a lower steam concentration tren l'

the other compartments at that below-deck level. The CMT South steam concentration then begins to rise through the rest of the transient untilits concentration matches that of the other below deck compartments at that level. The relative delay of steam access to the CMT South compartment is due to the more restrictive area of flow paths from above deck (flow path numbers 267 and 268) as compared to the flow areas feeding CMT North, Upper Steam Generator West, and Upper Steam Generator East volumes. Thus, calculated steam concentrations in compartments below deck are consiatent with a lack of global circulation within the t

model.

Internal containment heat sinks are important f6r mitigation of MSLB containment pressure, due to the long time constant for heat removal through the PCS shell. Thus, 480.1086F 9

[ M ghoust

NIC FSER OPEN ITEM e

io, artificially maintair,ing stratification in the lumped parameter model, bety/een the above-deck region and below-deck region (where internal heat sinks are located), results in a conservatively high containment precsure.

References

1. WCAP-146 U. %v. 2," Scaling Analysis for AP600 Containment Pressure During Design Basit. Accidents," June,1997.

2. WCAP 14/,07. Rev.1,"WGOThlC Application to AP600," July 1997.

3.

WCAP 14326, Rev.1,

• Experimental Basis for the AP600 Containment Vessel Heat and Mass Transfer Correlations," May 1997.

SSAR Revisions:-

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N;C FSER OPEN ITEM '

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