ML20147B304
| ML20147B304 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 01/05/1988 |
| From: | Papanic G YANKEE ATOMIC ELECTRIC CO. |
| To: | Fairtile M Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20147B307 | List: |
| References | |
| FYR-88-05, FYR-88-5, NUDOCS 8801150196 | |
| Download: ML20147B304 (14) | |
Text
Telaphone t617) 872-8100 TWX 710-380-7619 YANKEE ATOMIC ELECTRIC COMPANY n
M y
1671 Worcester Road, Framingham, Massachusetts 01701 w
January 5, 1988 FYR 88-05 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Attention:
Mr. Morton Fairtile, Project Manager Project Directorate I-3 Division of Reactor Projects I-II
References:
(a) License No. DPR-3 (Docket No. 50-29)
(b) Amendment No. 21 to Facility Operating License No. DPR-3, (December 4, 1975)
Subject:
LOCA Reflood Heat Transfer Models
Dear Sir:
Yankee Atomic Electric Company (YAEC) has revised its currently approved Yankee Nuclear Power Station ECCS evaluation model Reference (b) in the area of reflood heat transfer. The model changes are a result of the considerable amount of new data which have become available. The new model consists of a revised steam cooling model and a revised FLECHT correlation (FLECHT/SEASET).
The proposed models will be used for calculating heat transfer coefficients used during tne reflood phase of LOCA analysis. Attachment A demonstrates that the proposed models are conservative with respect to FLECHT/SEASET data and meet the Appendix K steam cooling criterion. A more detailed discussion of the new models is provided in Attachments B and C.
We plan to use these new models for generating LOCA limits to support Core 20 operation (January 1989). The analysis is scheduled to begin April 1, 1988.
Your review and approval of this submittal to met. that schedule would be appreciated.
We are prepared to meet with your staff to discuas any of the technical aspects of the new models to help expedite the review.
Very truly yours, Yankee Atomic Electric Company 8801150196 880105
[
PDR ADOCK 050 09 George Papanic, Jr.
P Senior Project Engineer Licensing GP:kem k
Attachments g {
4 1
4 ATTACHMENT A r
Summary of Justification for A Revised.
Reflood Heat Transfer Model for Yankee Nuclear Power Station LOCA Analysis 1
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SUl9tARY OF JUSTIFICATION FOR A 1
REVISED REFLOOD HEAT TRANSFER MODEL FOR YANKEE NUCLEAR POWER STATION LOCA ANALYSIS BACKGROUND 100FR, Part 50, Appendix K states that:
"For reflood rates of one inch per second or higher, reflood heat transfer coefficients shall be based on applicable data for unblocked cores including FLECHT results ("PWR FLECHT (Full I4ngth Emergency Cooling Heat Transfer) Final Report " Westinghouse Report WCAP-7665 April 1971). The use of a correlation derived from FLECHT data shall be demonstrated to be conservative for the transient to which it is applied; presently available FLECHT heat transfer correltations ("I'WR Full Length Emergency Cooling Heat Transfer (FLECHT) Group I Test Report,"
Westinghouse Report WCAP-7544 September 1970; "PWR FLECHT Final Report Supplement," Westinghouse Report WCAP-7931, October 1972) are not acceptable. New correlations or modifications to the FLECHT correlations are acceptable only after they are demonstrated to be conservative, by comparison with FLECHT data, for a range of parameters consistent with the transient to which they are aptiled.
During refill and during reflood, van reflood rates are less than one inch per second, heat transfer calculations shall be based on the assumption that coo)ing is only by steam, and shall take into account any flow blockage calculated to occur as a result of cladding swelling or rupture as such blockage might affect both local steam flow and heat transfer."
The currently approved ECCS evaluation model for the Yankee Nuclear Power Station (YNPS) conforms to these requirements. For reflood rates greater than one inch per second, conformance was accomplished by modification of the FLECHT beat transfer coefficient correlation given in WCAP-7931.(2)
The modification was made by developing a set of multipliers ( ) which are applied to the Westinghouse FLECHT heat transfer correlation, WCAP-7931, to make the correlation a best estimate of the experimental data at the reflood rates and pressures of interest. The multipliers are defined such that the
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time integrals of heat transfer coefficients for experimental and predicted values are equal over nine separate time periods. The FLECHT correlation is normally divided into three time periods. For the purpose of defining the multipliers, the three time periods were further divided to give nine time periods. The multipliers were also defined at five axial elevations to give a total of 45 multipliers. The currently approved set of multipliers is referred to as the ENC-2 FLECHT multipliers. The Westinghouse FLECHT correlation, with the ENC-2 multipliers, is referred to as the FLECHT/ ENC-2 correlation. The correlation is based upon the assumption that the heat transfer coefficient at a particular elevation is dependent upon the integrated energy distribution up to that elevation. This assumption makes the correlation applicable for core geometry and axial power distributions which ciffer f rom the FLECHT tests. Thus, each elevation in the specific fuel rod case may be related to an equivalent TLECHT elevation which yields the same integrated energy up to that elevation. The heat transfer coefficients, thus calculated, were further reduced by multiplying by 0.8 because the YNPS fuel rod diameter is smaller than that for which the correlation was developed.
For reflood rates less than one inch per second, conformance was accomplished through the use of a steam cooling model which is invoked when cladding rupture is calculated to have occured. The steam cooling model is used at and above the rupture plane and the FLECHT/ ENC-2 correlation is used 1>elow the rupture plane. The steam cooling model is based on the Dittus-Boelter correlation and an equivalent steam flow. The equivalent stean flow is defined such that the Dittus-Boelter heat transfer coefficient calculated immediately below the blockage plane equals the value calculated by the FLECHT/ ENC-2 correlation. At and above the blockage plane, the heat transfer coefficient is calculated using the Dittus-Boelter equation with the predetermined equivalent steam flow. Also, above the blockage plane, the steam flow used in the fluid energy equation is equal to the product of the l
inlet flow, the carry-over rate fraction, and an empirical coefficient. The empirical coefficient is defined to assure conservatism.
In addition, the cladding swelling and rupture is assumed to divert part of the flow from the rod. To account for the postulated flow diversion, the steam flow for both the fluid energy equation and the Dittus-Boelter equation is reduced by a fraction which varies with distance from the rupture location. - - -.
De FLECHT/ ENC-2 heat transfer correlation was based on FLECHT beater rod with a diameter greater than that of the YNPS fuel rod. Since no reflood heat transfer experimental data were available for fuel rod diameters typical of the YNPS fuel, the FLECHT/ ENC-2 heat transfer coefficients were reduced by multiplying by a factor of 0.8.
The steam cooling model was developed when the understanding of reflood heat transfer was incomplete. Specificelly, heat transfer at low flooding rates and the effects of clad swelling and rupture on the heat transfer were not clearly understood. The FLECHT-SEASET } Test Program was initiated to improve understanding in these areas, thus enabling the development of improved analytical models of PWR behavior durlog reflood.
In addition, the FLECHT-SEASET Test Program provided information about reflood effects on fuel designs' typical of the YNPS fuel. Data from the FLECHT-SEASET Test Program have become available in recent years, thereby providing a basis for improved models within Appendix K.
PROPOSED STEAM COOLING MODEL Since the development of the currently licensed steam cooling model, a substantial data base pertinent to these issues has been developed through the FLECHT-SEASET Test Program. These data indicate that (1) no discontinuity in heat transfer as a function of flooding rate occurs at one inch per second as stipulated by Appendix K, and (2) the core heat transfer is not degraded under blockage situations expected for a PWR LOCA. However, the requirements of Appendix K remain in effect. A new steam cooling model is developed which takes advantage of the new experimental findings and yet meets the intent of Appendix K.
The features of the new steam cooling model are discussed below:
1.
Dominant heat transfer is derived using the FLECHT correlation.
This is a reasonable assumption in light of the FLECHT-SEASET data base.
These data indicate that core heat transfer is not degraded under blockage conditions expected for a PWR, Hence, the FLECHT correlation asy be used to calculate the heat transfer coefficient both above and below the blockage plane..
2.
Steam temperature is assumed to be the saturation temperature.
In the current licensing methodology, when the FLECHT correlation is used, the sink temperature is assumed to be the saturation temperature.
This approach is consistent with the derivation of the FLECHT correlation and has resulted in conservative prediction of the behavior of a fuel rod during reflood; 3.
Clad swelling and rupture is assumed to have the following two-fold effect on local heat transfers a.
Degradation of heat transfer due to flow diversion as postulated by Appendix K, and b.
Heat transfer enhancement due to single-phase turbulence, as observed in the FLECHT-SEASET tests.
The existing Yankee Atomic Electric Company (YAEC) flow diversics model is used in calculating the local steam flow. This model conservatively satisfies the Appendix K criteria.
To model the single phase turbulence, a heat transfer enhancement factor has been developed from the experimental data. Details of this model are discussed in Reference 6, provided as Attachment B of this document.
The steam cooling model change is identical to that proposed for application to Maine Yankee (NY) in Reference 7.
Discussions in Attachment B pertaining to the YAEC FLECHT/ ENC-2 correlation benchmarking and MY plant-specific demonstration of model performance are replaced by the two sections which follow.
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PROPOSED FLECHT CORRELATION MODEL The FLECHT-SEASET test series simulated fuel diameters which are representative of the YNPS fual. The extensive data base that has been generated covers the range of reflood rates and pressures encountered in the YNPS reactor. Because of the availability of such a data base, it is proposed to revise the YAEC FLECHT/ ENC-2 correlation for YNPS by defining a new set of __
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multipliers for the Westinghouse FLECHT correlation given in WCAP-7931. The new set of multipliers will replace the ENC-2 FLECHT multipliers and the additional multiplier of 0.8 that is currently applied because the YNPS. fuel diameter is smaller than that for which the correlation was developed.
he details of the new YAEC FLECHT correlation (FLECHT/SEASET) are contained in Reference 8, provided as Attachment C of this document. The correlation consists of a new set of multipliers which are applied as a function of equivalent FLECHT elevation to the Westinghouse FLECHT correlation (WCAP-7931). B is makes the correlation a best estimate of the FLECHT-SEASET experimental data at the reflood rates and pressures of interest for the analysis of YNPS. Thus, the conformance of the YAEC FLZCHT/SEASET correlation to Appendix K requirements, for reflood rates greater than one inch per second, is assured.
JUSTIFICATION OF PROPOSED MODELS The new steam cooling model and the new YAEC FLECHT/SEASET correlation were developed by Intermountain Technologies, Incorporated (ITI) and were directly incorporated into the YAEC version of the T00DEE2 code.
i Sensitivity studies performed for characteristic YNPS analysis statepoints l
with cosine and top skew axial power shape profiles show that use of the new models result in lower Peak Cladding Temperatures (PCTs) than were computed with the old steam cooling model and the YAEC FLECHT/ ENC-2 correlation, his is shown in Figures 1 and 2.
These figures also show that the new steam l
cooling model results in conservative PCTs with respect to the new YAEC FLECHT/SEASE7. correlation as required by Appendix K.
Additionally, eight FLECHT-SEASET tests in the appropriate range of amperimental conditions were simulated using the T00DEE2 code, and the results were compared to the data. The purpose of the simulations was to demonstrate the adequacy of the new YAEC FLECHT/SEASET correlation. The results of the comparison are shown in Figures 3.1 through 3.8 of Attachment C.
The TOODEE2 computed results are conservative with respect to the test data for the conditions expected in the YNPS reactor. l
Since the FLECHT-SEASET test series lacks experimental data with skewed power profiles, two FLECHT low flooding rate skewed tests ('} were simulated using the T00DEE2 code. Ite tests that were simulated were in the range of parameters expected for reflood in YMPS. The results are shown in Figures 3 and 4.
The T00DEE2 computed results are conservative with respect to the test data.
The model development, implementation, and hochmarking results have been reviewed in detail at YAEC. Several of the ITI calculations were repeated here to further develop an in-house understanding of the new models and to assess the impact of modeling techniques on the simulation of FLECRT and FLECHT-SEASET testn. These calculations employed input decks which were derived independently at YAEC. The sources of minor differences in the YAEC and ITI results were identified, and modeling differences were resolved.
Through this effort, YAEC has desinstrated full working kr.awledge af the new models and their implementation into the T00DEE2 code, jiUPMARY AND CONCLUSION It is proposed that the current steam cooling model be replaced by the new steam cooling model. It is also proposed that the new YAEC FLECET/SEASET l
correlation, based on the FLECHT-SEASEI multipliers be appihd for the analysis of YNPS. The new models rely on experimental data, and satisfy the requirements of Appendix I to 10CFR, Part 50.
REFERENCES 1.
Code of Federal Regulations. Title 10. Part 50.43, Appendix K. Licensing of Production and Utilization Facilities, ECCS Evaluation Models."
2.
F. F. Cadek, et al., PWR FLECHT Final Report Supplement, WCAP-7931, October 1972.
3.
Exxon Nuclear Company WREM-Based Generic PWR ECCS Evaluation Ibdel, Supplement 1: Further Definitions and Justifications to Reflood Heat Transfer Models, XN-75-41 (Supplement 1), dated August 14, 1975.
l 4.
F. W. Dittus, L. M. K. Boelter, University of California Publication, Eng., Volume 2 Page 443, 1930.
5.
M. J. Lof tus, et al., PWR FLECHT-SEASET Unblocked Bundle, Forced and Gravity Reflood Task Data Report Volume 2 Appendix C.
MRC/EPRI/ Westinghouse Report No. 7, September 1981.
6.
R. T. Jensen, Revision to Yankee Atomic Electric Company Steam Cooling Model for Reflood Rates Less Than One Inch Per Second, prepared for Yankee Atomic Electric Company, April 1987.
7.
Letter, G. D. Whittier (MYAPC) to V. Nerses (USNRC), "Maine Yankee LOCA Analysis," MN-87-59, dated May 21, 1987.
8.
R. T. Jensen, Revision to ths Yankee Atomic Electric Company Reflood Heat Transfer Correlation, prepared for Yankee Atomic Electric Company, November 1987.
9.
E. R. Rosal, et al., FLECHT Low Flooding Rate Skewed Test Series Data Report, WCAP-9108 May 1977.
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FIGURE 1 REFLOOD HEAT TRANSFER MODEL COMPARISONS.
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F!GURE 2 REFLOOD HEAT TRANSFER MODEL COMPARISONS.
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ATTACHMENT B i
t Revision to YAEC Steam Cooling Model for Reflood Rates Less than 1 IN/SEC i
R. T. Jensen Intermountain Technologies, Inc.
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I REVISION TO YAEC STEAM COOLING M) DEL POR Reft 00D RATES LESS THAN 1 IN/SEC April 1987 Prepared for YANTIE ATOMIC ELECTRIC COMPANY 1671 Woroester Framingham, Mass 01701 Prepared by R. T. J ense n INTER!OUNTAIN TECHNCLCGIES, IN C.
1400 Benton - P. O. Box 1604 Idaho Falls, Idaho 83403-1604 y p d L M o d A_4 0 A
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l NOTIS Ybis report was prepared by the organisation(s) named below as an account of work sponsored ty the Yankee Attaio Electric Company (TAEC).
Neither YAEC, embers of YAEC, the organization (s) named below, ror ag person acting on behalf of ag of them (a) makes ag warranty, express or implied, with respect to the use of ag information, apparatus, method, or process disclosed in this report or that such use may not infringe privately owned rights; or (b) assmes ag liabilities with respect to the use of, or for damages resulting from the use of, ag idornation, apparatus, method or process disclosed in this report.
Prepared by DIERWUNYAIN TECHN3. CURS, DC.
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00N 3NTS Saetion lagg 51)tuRY AND CONG.USIONS 1
1 HTRODUCTION 2
2 DISCUSSION OF FLECHT-SEASET BLOCKED BUNDLE TEST RESULTS 3
3 YAEC HODEL DESCRIPTION 8
4 REFERDCES 14 APPENDIX A PLECHT 00RRIL ATION BDICHMARKING 15 I
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1 SJHMARY AND CCNCLUSIONS The Yankee Atomic Electric Company (YAEC) steam cooling model for core heat transfer wita mflooding rates less than 1 in/see has been revised.
The object!.ves met by the new steam cooling model are to:
~
1.
Remove the excessive conservatism present in the existing YAEC steam cooling model.
2.
Utilize information f ree EECHT-SEASET in developing and justifying the new model.
3 Satisfy the intent of Appendix K by conservatively computing the eff ect of the blockage upon the channel flow and heat transfer.
4.
Aos:ure that the model is always conservative compared with the EU'HT correlation.
4 review of the results of the FLECHT-SEASET test results for biccked and unblocked be.tles has shown Jat, even for blockages with flow bypass, the net effect of blockage upon the core heat transfer is beneficial. Ite heat transfer enhancement observed in EECHT-SEASET was due to the combined effects of droplet brt Jp and single-phase steam turbulence.
The Appendix K requirenent that heat transf er be asstaned to be only due to steam cooling precluded a ccounting f or the effect of droplet breakup but allows the inclusion of a steam turbulence model.
The revised model thus assumed steam flow with the (bminant heat transfer to be as calculated using the YAEC version of the PLEGT heat transfer coefficient correl ation.
The detrimental effect of flow bypass in the blockage region and the heat transfer enhancement effect of steam turbulence were conservatively model ed.
In addition, since the YAEC EECHT correlation serves as the basis for the heat transfer coefficient, the correlation was benchmarked against six test runs from two of EECHT test series which were not included in the data base used in developing thw correlation.
This benchmarking showed the YAEC EECHT heat transfer correlation to be conservative in the range of intcrest for Haine Yankee.
Sensitivity studies performed for Maine Yankee with oosine and top skwed power profiles have shown that the e-* of revised steam cooling model results in lower peak cladding temperatures (PCT) than ware computed with the old steam cooling model.
The computed PCTs were, however, higher than those computed asstning no steam oooling requirement (EECHT correlation).
1
i Section 1 INTRODUCTION Since the faukee Atomic Electric Company (YAEC) steam coling model(I) for reflood heat transfer at reflooding rates of less than 1 incu/sec was developed in 1975, a considerable amount of new low reflooding rate data have become av ail abl e.
These data include test assemblies with and without flow blockage.
The data from PLECHT-SEASET(2,3,0 have shown that:
(1) no discontinuity in heat transfer occurs at a flooding rate of 1 in/sec as postulated in 10CFR50 Appendix K, and (2) that the core heat transfer is not degraded under blockage situations expected for a NR LOCA.
The requirements of 10C7E50 Appendtv K are, bowever, still in effect, and it is necessary for the revised steam cooling model to meet the intent of Appendix K.
A revised steam cooling model has thus been developed whidi assumes that cooling is by steam only and which accounts for the effect of blockage upon both the heat transfer and steam flow. 'Ibe new model has been defined to remove most of the excessive conservatism in the existing model but such that the calculated heat transfer cannot exceed that which would be calculated if the stean cooling requirement were not imposed,
- i. e, that calculated using the YAEC yersion of the EECHT correlation.
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The justification of the new model consisted of using a formulation consistent with the data trends and models f rom the EECHT-SEASET 163-rod blocked bundle In addition, the YAEC version of the EECHT wrrelation was tenchmarked te st s.
against data from the EECHT Low Flooding Rate Co:ine(5) tests and the FLECHT f
Low Flooding Rate Skewed testa (6),
Seccion 2 of this report discusses the results of and the applicable aralytical models developed in the EECHT-SEASET blocked bundle tests.
The new YAEC stean cooling model and typical results obteined with the new model are presented in Section 3
'Ibe EEQiT oorrelation benchmarking results are presented in Appendix A.
Section 2 DISCUSSION OF EECHT-SEASET BLOCKED BUNILE TEST RESULTS The EECHT-SEASET blocked bundle tests consisted of tests in a 21-rod bundle and r 163-rod bundle.
The 21-rod bundle tests were used to determine effects of,various flow blockage configurations on reflooding behavior and to screen ficN blockage configurations for 163-rod flow blockap tests. The 163-rod tundle provided the means to determine the effect of blockage upon heat transfer with the worst case blockage configuration in a bundle large ',nough to allow flow bypass around the blocked region.
The oveall result was a bleckage heat transfer benefit relative to no blockage.
Thi relative benefit due to blockage can be se e n i n Figur e s 2-1 and 2-2.
Figure 2-1 shows the ratio of beat transfer coefficient with blockage to that withcut blockage as a function of time and elevation for configurations with and without flow bypass.
The maximum temperature rise difference or the i
temperature rise observed in an unblocked bundle minus the correspnding temperature rire in a blocked bundle is shown in Figure 2-2 as a function of flooding rate and elevation.
Two important conclusions can be reached based j
l upon these data.
The first is that even with flow bypass, the effect cf blockage l
l upon heat transfer is beneficial.
The second conclusion is that for flooding rates of less than 15 in/sec, as the flooding rate decreases, the relative benefit due to blockage generally incre.ases.
This is important because the maximum benefit occurs at the flow rates for which Appendix K requires a penalty i
to be taken.
l showed the An11ytical studies performed using the COBRA-TF computer program heat transfer enhancement to result from two effects.
These were (1) breakup of the liquid droplets due to acceleration and increased impact in the blockap zone, and (2) increased turbulence of the ste.am phase due to boundary layer separation and reattachment as the flow accelerates in the blockaga region.
A model for the beat transfer enhancement due to the steam phase turbulence was developeo in EECHT-SEASET(3,4)
Sinoe the steam phase phenomena are allowahle within the Appendix K requirements, that model will be described here.
The
- model expresses the local Nusselt number in terms of the free stream (unblocksd)
Nusselt number and the maximus Nusselt nunber which occurs at the point of 3
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14tximta Teeprattre Rise Difference Between Blocked and Unblocked Bundles as a Function of Flooding Rate ard Elevation (Frca Reference 4).
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i boundary layer reattachment.
The ratio of the maximum-to-free stream Nusselt nebers is given as 0.2Re l0 N
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-b 0.07 97 ReDo where the expression in the numerator was obtained f rca abrupt expansion experiments performed with air by Zemarick and Dougall(I) and the denominator is a correlation for fully developed flew from the EECHT-SEASET 161-nxi tundle steam oooling test.
The undisturbed diameter is D, and the boundary layer O
separation point diameter, D,,p, is assmed to be t!.e diameter at the blockage pl ane. For blockage without flow bypass, the mass flew is constant and Eq. 2.1 can be approximated by g-3 = 2.5 (D /D,p)2/3 (2.2) 0 Comparison of R. 2.2 to data frm several experiments, including the RECHT-SEASET 21-4 od bundle steam cooling testa (2) showed goor' agreement if the conatant 2.5 were changed to 1.88, thus i
""3 = 1.88 (D N (2 3) l O sep The Nusselt number returns to its fully developed valm as the reattached tomdary layer develops and the free stream turtatlence decay u.
The decay was found to be exponential and independent of Reynolds number.
The expomntial relationsMp l
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Section 3 YAEC HODEL DESCRIPTION The objectives in developing the new YAEC steam cooling model are as follows:
1.
Remove the excessive conservatism present in the existing YAEC steam oooling aodel.
2.
Utilize information from RECHT-SEASET in developing and justifying the new model.
3.
satisfy the intent of Appendix K by conservatively computing the 7ffect of the blockage upon the channel flow and beat transf er.
4.
Assure that the model is always conservative compared with the EECHT oorrelation.
The modeling assumptions used to develop a new steam cooling model which meets the above objectives are:
1.
The coolant flow in saturated steam with a constant temperature of Tg g.
2.
The dominant $; eat transf er is as calculated using the EECHT i
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3 Flew bypass in the blockage region will be computed using the existing YAEC f1w diversion model, l
I l
4.
The change in beat transf er due to flow bypass will te calculated.
5 Heat t.'ar.sfer enbac.:ement due to single-phase turbulence will be conadrya,1vely calculated.
6.
Heat tr ansf er enhancement due to drop) et treakup will be reglected.
Equation 2.1 san be used to compute both the effect of flw bypass upon the beat transf er and the single-phase beat transfer enhancemeat. 'Ibe IAEC ficw diversion model provides the ratio of the local mass velocity, 0, to the f ree stream mass I
volscity, Go, as a function of blockage fraction and distence from the blcckasc pl ane.
If Eq. 2.1 is written in terms of mass velocity I
e l
l 8
3 Nu,
0.E ( GD,
/y)
( 3.1 )
g-- = 0.0797(0 D # }D.67p o
0OP or D*12)2/3 Nu" O 2/3 (3.2)
(D g-CONS (g-)
o O
O where the constant, (X)NS, will be defined to assure conservatim. Be diameter, s
e unblocked channel D,,p, is the diameter at the blockage plane, and D 0
diameter.
Rus, for diameters as defined by Eq. 2.7 D**f. (1 - BLK)
(3.3)
DO where BLK is the blockage fraction.
Substituting Eq. 3.3 ir.to Eq. 3 2 gives CONS (O,)2/3,, _ 3tg)U3 (3,4 )
.53 :
4 g
N%
0 Equation 3.4 is used to solve for the Husselt number at the blockage plane. To obtain the beat transfer coefficient f ree the Nussolt number, a further dia:eter oorrection is needed.
From the definition of Nusselt number (Nu = bD/K l
__fB
.b!N..D88P./K Nu Nu b DA n
y n or k
_"fE (1. - BLK)-1/
EM (3 5)
O The her.t l
where b,, is the beat transfer coefficient at the blockage plane.
transfer coefficient for an equivalent unblocked coolant char nal, g, is obtained from the YAEC FLECHT correlation.
G 9
For the 'inblocked nodes in the channel, Eqs. 2.5 and 2.6 are solved f or the Nussel t number.
The diameters for all nodes except the blockage plane are asstased to equal the diameter of the unblocked channel.
The heat transfer ratio is, thus, aquel to the Nusselt number ratio for all nodes except the blockage plane.
In addition, thc beat transfer coerficient computed in the steam cooling
.cedel is limited *,c be less than er equa*. to that computed using the RECHT oceral ation.
Computed heat transfer coefficient rec *.os for blockage of 20, 30 and 60% are shown in Figure 3-1.
The heat tran:ter returns to the free stream or inblocked value af ter 1.6?5 feet for blockages of 20 and 60% and af ter 1.675 feet fer 30%
bl ockage.
The potential effect of the new mouel upon the PCT in the Haine Yarjee a eacto* in show n in."igures 3-2 ar.d 3-3 for power shapes that peak at core uibpla ae and 855 core heighc, respe ct;~ ely.
The new nodel can be seen to result in lower PCIs than +Sa predous : Lam cooling t.cGa, but is derinitely conservative with respect to the EECHT correlation.
I I
l l
l l
l l
l
{
\\
10
i i
O i
e
,,r f/
/
1
/
\\
/
I I
i s/
/
I I
I 1
I I
I o
i I
~
i E
I i
I z
i W
l i
U l
E I
I bR l
I Ud i
I x
i E
I I
l l
I l
I 1
no* -I l
s I
g I
I I
i i
i I
i I,I 20% BLOCKAGE a
in 30% BLOCKAGE l
d i
I l
1 60% BLOCKAGE I
I I
%[
f d
i i
i i
l
- 0. 0
- 0. 4
- 0. B
- 1. 2
- 1. 6
- 2. O DISTANCE ABOVE BLOCKAGE (FT)
FIGURE 3-1.
HEAT TRANSFER COEFFICIENT RATIO ABOVE THE BLOCKAGE l
l 11
I i
i i
I OLD STEAM COOLING MODEL
- NEW STEAM COOLING MODEL k
NO STEM 4 COOLING N
e c
x
^
4 E
N Ei
/
\\
i
=
\\
\\
\\
\\
i
\\
8 i
i i
i I
5 6
7 8
9 10 11 ELEVATION (FT)
FIGURE 3-2.
STEAM COOLING MODEL COMPARISONS, COSINE WITH 60% BLOCKAGE 12
e 8
3 g
g N
b w
$s
/
E"
/
N s
y i
\\
8 OLD STEAM COOLING NEW STEAM COOLING NO STEAM COOLING 8
3 I
- 9. 5 10.5 11.5 ELEVATION (FT)
FIGURE 3-3.
STEAM COOLING MODEL COMPARISONS, TOP SKEWED WITH 60% BLOCKAGE i
1 13
Section 4 REFERDiCES 1.
Exxon Nuclear comoany WREM-Based Generic PVR ECCS Evaluation Mod el.
Leclement 1: Furthrr Definitions and Justifications to Reflood Heat Transfer Models, IN-75-41, August 14, 1975.
2.
N. Lee et al., PWR FLECHT-SEASET Unblocked Bundle. Forced and Gravity Reflood
_ Task Data Evaluation and Analysis Reoort, N RC/E PRI/We stingh ouse-10,
February 1982.
3 L. E. Hochreiter et al., Analysis of FLECHT-SEASET 161-Rod Blocked Bundle Data Using COB R A-TF, NRC/EPRI/Westingbouse-15, April 1985 4.
L. E. Ho&reiter, FLEClfr-SEASET Prorram Final Reoort, NRC/EPRI/Westingbouse-16, November 1985.
5.
E. R. Rosal et al, FLECHT Lo # Flooding Rate Cosine Test Series Data Reoort, WCAP-8651, December 1975 6.
E. R. Rosal et al., FLECHT Low Flooding Rate Skewed Test Series Data ReDort, WCAP-9108, May 1977 7.
P. P. Zemane ck and R. S. Dougall, "Local Heat Transf er Downstream of an Abrupt Circular Channel Expansion," J ournal of Heat Transfer, Fbtruary 1970, pp. 53-6 0.
~.
Appendix A EECHT CORRE ATION BENCHMARKING At the Deoenber 15, 1986 meeting between YAEC and the NRC staff, the NRC stated that additional benchmarking of the YAEC version of the EECHT oorrelation is expe cte d.
The YAEC RECHT oorrelation I) was developed before aus Icw flooding rate data and data with skewed profiles became available.
The available data have been reviewed, and data frce the EECHT low flooding rate cosine (5) and skewed ( } tssts have been selected for this benchmarking.
Table A-1 presents typical reflood parameters for the Maine Yankee reactor and for the EECHT tests chosen for use in the benchmarking.
The six te st s w hich were selected are felt to provide an adequate indication of the correlation performance in the range of parameters expected for reflood in Maine Yankee.
The YAEC version of the T00DEE2 code was used to model the beater temperature response of the simulated fuel rods in the FLECHT tests.
Some minor code modifications were required to eliminate the metal water reaction and gap conductivity calculations in 700DEE2.
1he results of the ben & marking analyses wee evaluated by comparing the calculated l
peak cladding temperatures as a function of elevation to the test results l
presented in Refrences 5 and 6.
These results are shcwn in Figures A-1 through A-6.
l l
The T00DEE2 results can be seen to be clearly :onservative with respect to the test data.
This is especially true for the tests with top skewed profiles.
i l
l l
l l
15
\\
Table A-1 YAEC FLECHT (X)RRIL ATION BDiCHMARKING MATRIX Test /Plas Flood Rate T
keasse Q,,,
M da init aub MLim Yankee 2.0-0.8 1500.
- 30. - 40.
0.64
- 148, 14331 1.55 (100 see) 1204.
32.
0.7 103 Sewed Prdne 1.0 (Omard) 14647 1.0 1610.
21.
0.47 142.
Sewed Prdile 16110 0.8 1617.
20.
0.7 132.
Sewed Prdile 5917 30 ( 4.6 see) 16'X).
40.
0.95 141.
(bsim Pr&ile 0.77 (Omard) 4831 1.5 1600.
40.
0 95 142.
Cbsine Prdile 4641 1.0 1601.
20.
0 95 139 Oosine Prene 16
1 I
i i
i Og og O
$a O
w?
e*
f^
O O
g eO f
e g h-i S
x" O
0 0
S 8
e S
o 8
e e
CALCULATED VS MEASURED 1
o l
g i
l l
I I
l 0
2 4
8 8
10 12 ELEVATION (FT)
FIGURE A-1.
TOODEE FLECHT COMPARISON, FLECHT SKEWED TEST 14331 l
17
8 i
i i
i i
g g
8 _
'8 U
O Y
O
- 8 e
gi_
me 6
h 8
8 e
3 O
Z e
a g
O e
O f
e o
t CALCULATED VS MEASURED l
e O
E I
I I
I I
O 2
4 6
8 10 12 ELEVATION (F)
FIGURE A-2.
TOODEE FLECHT COMPARISON, FLECHT SKEWED TEST 14647 l
18
I I
i i
i 8
10 8
N G
O
&o8 8
8 I w-e W
e x
0 Ogg 8
O i
e e
e e
e O
O l
CALCULATED.VS HEASURED l
8 0
C e
I i
i 1
0 2
4 6
8 10 12 ELEVATION (FT)
FIGURE A-3.
TOODEE FLECHT COMPARISON l
FLECHT SKEWED TEST 18110 l
(
19
e i
i I
i i
O O
O O
O O
O O
no 8
e e
e 0o se O
D
'0 x
O o
8 O
~
CALCULATED VS HEASURED O
e 8
i I
I i
i m
0 2
4 6
8 10 12 ELEVATION (FT)
FIGURE A-4.
TOODEE FLECHT COMPARISON, FLECHT COSINE TEST 5917
'r a
I D
1 1
N e O O
O O
O 8
O
^6 O
W?o
$S W-O X
O I
g 8
D
=
O O
CALCULATED VS MEASURED 8*
I I
q r
O g
6 8
10 12 ELEVATION (PT)
FIGURE A-5.
TOODEE FLECHT COMPARISON, FLECHT COSINE TEST 4831 21
-+4.
M m.m.
I i
i i
i i
8 s
8e 8e o
8 e
8 N
Q O
OO O
C"8 8
t 1
w to h~
O O
N
- '\\
l 0
8
~
e g
O l
8 l
oq O
cal.CULATE0 VS HEASUREO o
I I
I I
I l
0 2
4 8
8 10 12 ELEVATION (FT)
FIGURE A-8.
TOODEE FLECHT COMPARISON, FLECHT COSINE TEST 4641 1
22
ATTACHMENT C Revision to the YAEC Reflood Heat Transfer Correlation R. T. Jensen Intermountain Technologies, Inc.