ML20248M117

Safety Evaluation of TR XN-NF-82-20 (P),Rev 1,suppl 6, Exem/Pwr Large LOCA ECCS TOODEE2 Updates. Rept Acceptable

ML20248M117
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Issue date:	06/05/1998
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NUDOCS 9806150022
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SAFETY EVALUATION BY THE OFFICE OF NUCI FAR REACTOR REGUI TION RFI ATING TO SIEMENS POWER CORPORATION TOPICAL REPORT XN-NF-82-20(P)

REVISION 1. SUPPLFMENT 6 i

EXEM/PWR LARGE BREAK LOCA ECCS TOODFF9 UPDATES (TAC NO. M97519) 1 BACKGROUND la December 1996, Siemens Power Corporation (SPC) submitted Topical Report XN-NF-82-20(P), Revision 1, Supplement 6, "EXEM/PWR Large Break LOCA ECCS TOODEE2 l Updates,"(Ref.1) which provided response to the staff's rejection of the Supplement 5 of the base topical report (Ref. 2). SPC also provided additional information by letter dated August 6, l 1997, in response to staff requests for additional information (Ref. 3). The staff requested additional information based on its review of the subject topical report and on information  !

uncovered as part of an inspection conducted at the SPC facilities during March 1997. '

Topical Report XN-NF-82-20(P), Revision 1, Supplement 5, was supposed to provide a l description of and supporting technical information for all changes made to the TOODEE2 hot i

rod heat up computer code made since the code's approval in 1986. The staff found that SPC had to seek a new solution to correct the unphysical behavior of the TOODEE2 reflood heat transfer coefficient or provide additional information to support the use of the model.

Topical Report XN-NF-82-20(P), Revision 1, Supplement 6, was the SPC response documenting the updates related to a change in the implementation of the Fuel Cooling Test l Facility (FCTF) reflood heat transfer correlation in the TOODEE2 hot rod heat up code and a l l correction to the Z-Equivalent model. The staff requested additional information as a result of l its review of the subject topical report and an inspection conducted at the SPC facilities in

. March 1998. That inspection included within its scope the FCTF heat transfer research program. SPC responded to the RAls by letters dated August 6,1997, (Ref. 3) and September 23,1997, (Ref. 4).

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The staff's Safety Evaluation Report of the above referenced materials follows.

2 EVALUATION l 2.1 FCTF Assessment The staff noted in its SER published in regard to Topical Report XN-NF-82-20(P), Revision 1, Supplement 5, that insufficient support had been provided to demonstrate compliance with the requirements of 10 CFR Part 50, Appendix K. The requirement of 10 CFR Part 50, Appendix

~ K.il.4 is that "To the extent practicable, predictions of the evaluation model, or portions thereof, shall be compared with applicable experimentalinformation." In response to the staff's concem, SPC has performed assessment of the FCTF heat transfer correlation against the cylindrical core test facility (CCTF) data. SPC reviewed and identified 17 CCTF tests as having appropnate conditions for FCTF heat transfer correlation assessment. In performing the assessment, SPC has shown that the peak cladding temperature (PCT) predicted by the FCTF correlation exceeded that measured in the tests.in all 17 cases. Thus, the FCTF correlation produces a conservative result. The use of data obtained independently of those used to ,

develop the FCTF heat transfer correlation for assessment of the correlation assures the ENCLOSURE 9806150022 990605 PDR TOPRPENVEg

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a 2-

. applicability of the correlation.

l The staff concludes that adequate assessment of the FCTF heat transfer correlation has been l

L performed to demonstrate its applicability to analysis of the Large Break Loss-of-Coolant Accident (LBLOCA).

2.2 FCTF Reflood Rata l ' The 1986 FCTF heat transfer correlation has been limited to a reflooding rate of l L

1.77 inches /second since reflooding data were not obtained at highU reflood rates. In addition, an anomalous behavior was noticed for reflooding rates in the range of 1.5 to I

-1.74 inches /second. In this region heat transfer was predicted to decrease as the reflooding  !

rate increased. The decreasing heat transfer is not supported by the FCTF data nor by data )

from the FLECHT program for which heat transfer continuously increases as reflood rate increases.

As a result, SPC has chosen to limit the FCTF heat transfer correlation by imposing a linearly increasing heat transfer rate for reflooding rates from 1.0 to 1.74 inches /second, and then a constant heat transfer rate beyond that point.

The staff finds the limitations placed on the FCTF heat transfer correlation as a function of reflood rate to be conservative and acceptable.

2.3 FCTF Ouench Time The quench time correlation relates quench time with the flooding rate, peak linear heat generation rate, peak initial fuel rod temperature, initial core inlet subcooling, system pressure, and elevation. The FCTF quench time correlation has been modified to now use a peak linear heat generation rate consistent with hot rod parameters, thus increasing Q. from the adjusted value (1.14 times core average) to hot rod conditions (up to 2.5 times core average). This will result in an increase in the calculated quench time.

. SPC proposed, in Supplement 5 of the Topical Report, use of the adjusted Q. since it was believed to be more realistic in representing core average quench front behavior in a large -

PWR. Mixing parameters such as a quench time based on average core parameters with the heat transfer coefficient calculation using hot rod data is inconsistent with the derivation of the heat transfer coefficient. Using a quench time correlation based on the hot rod peak linear heat generation rate is conservative and gives results comparable to the 1986 model.

The' staff finds that the change in the FCTF quench time correlation further provides i conservatism in the calculation of PCT and is acceptable.  ;

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3.0 CONCLUSION

S Siemens Power Corporation has demonstrated that the FCTF heat transfer correlation, reflood

, rate, and quench time correlation result in conservative prediction of peak cladding temperature following a Large Break LOCA. Use of the modifications made to the 1986 correlation as applied in the EXEM-PWR Large Break LOCA ECCS model and TOODEE2 code are i

acceptable. Through comparisons with data obtained outside of the FCTF test program SPC i has shown that the heat transfer correlation is applicable to a wider data base.

The staff approves the use of the 1996 FCTF heat transfer correlation as requested by XN-NF-82-20(P), Revision 1, Supplement 6.

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4.0 REFERENCES

1. XN-NF-82-20(P), Revision 1, Supplement 6,"EXEM-PWR Large Break LOCA ECCS TOODEE2 Updates," December 1996, Siemens Power Corporation.

2. XN-NF-82-20(P), Revision 1, Supplement 5,"EXEM-PWR Large Break LOCA ECCS  !

TOODEE2 Updates," June 1996, Siemens Power Corporation. I 3.. Letter August 6,1997, " Request for Additional Information (RAI) Related to the Topical Report, "EXEM-PWR Large Break LOCA ECCS Model Updates," XN-NF-82-10(P), ,

Revision 1, Supplement 6," Siemens Power Corporation.

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' 4. Letter September 23,1997, " Request for Additional Information (RAl) Related to the  !

Topical Report, "EXEM-PWR Large Break LOCA ECCS Model Updates,"

XN-NF-82-10(P), Revision 1, Supplement 6," Siemens Power Corporation.

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l l Mr. Jerry S. Holm If our criteria or regulations change so that our conclusions as to the acceptability of the report are invalidated, Siemens and/or the applicants referencing the topical report will be expected to revise and resubmit their respective documentation, or submit justification for the continued applicability of the topical report without revision of their respective documentation.

Sincerely, -

" Original Signed By" i Thomas H. Essig, Acting Chief Generic Issues and Environmental Projects Branch .

Division of Reactor Program Management l Office of Nuclear Reactor Regulation '

Enclosure:

XN-NF-82-20(P), Revision 1, j Supplement 6, Evaluation i DISTRIBUTION:  !

. Central f/c:-- . 'h PGEB r/f PDR SRXB r/f i CHolahan '

RCaruso TCollins RLandry EWang DOCUMENT NAME:G:ULB\EXEMPWR.SE6 OFC DRPM;PGEB DRPM:PGE,S AC:PGEB NAME MNngham:ayw k hskbf k hTEssig DATE (, /[/98 6 / 3 /98 G /6 /98 OFFICIAL RECORD COPY

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