ML20059G301

Forwards Response to NRC 900327 Request for Addl Info Re BAW-10174, Mark-BW Reload LOCA Analysis for Catawba & Mcguire

ML20059G301
Person / Time
Site:	Mcguire, Catawba, McGuire
Issue date:	09/04/1990
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-75138, TAC-75139, TAC-75140, TAC-75141, NUDOCS 9009120240
Download: ML20059G301 (7)

Text

..

.. ;. Il I Duke hwr Compary llAt B ktn  ;

.P0 Box 33193 57ce hesident

.. Charlotte. N C 28242 Nuclear hvduction (704)373-4531 t

DUKEPOWER September 4, 1990 ,

t U. S. Nuclear Regulatory Commission ATTN: Document Control Desk  ?

Washington, D.C. 20555

Subject:

McGuire Nuclear Station Docket Numbers 50-369 and -370 1 Catawba Nuclear Station 4 Docket Numbers 50-413 and -414 i Response to Request for Additional Information Regarding BAW-10174 (TACS 75138/75139/75140/75141)  :

By letter dated March 27, 1990, the NRC staff requested information on Topical Report BAW-10174, " Hark-BW Reload LOCA Analysis for Catawba and McGuire." These questions have been answered by letters dated June 7. July .

25, and August 8, 1990. A revision to one of the computer. codes used in .

BAW-10174, after the Topical Report was released, has had a small effect on the LOCA Applications Topical Report results. Therefore, this supplemental '

Response '30 is provided. The response to Question 13 in the July 25, 1990 submittal refers to this information.

If there are any questions, call Scott Gewehr at (704) 373-7581. '

Very truly yours,

.f rt M, / . eMW .

Ha1 B. Tucker SAG /224/lcs Attachments 0'?103 9009120240 900904 ,

PDR ADOCK 05000369 P PDC 1 noot a '

' ' Lt

' i U. S. Nuclear Regultt:ry Cormicsion [

September 4,1990 Page 2 [

xc: Mr. S. D. Ebneter,- Region'al Administrator  !

11. S. Nuclear Regulatory Commission-Region II, 101.Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 .

Mr. Darl S. Hood, Project _ Manager ,

Office of Nuclear Reactor Regulation ,

U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Dr. Kahtan Jabbour, Projects Manager Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Wash *ngton, D.C. 20555 Mr. L. L. Losh ,

3315 Old Forest Road P.O. Box 10935 Lynchburg, Virginia 24506-0935 .

-l Mr. W. T. Orders l NRC Resident Inspector  :

Catawba Nuclear Station >

Mr. P. K. VanLoorn l NRC Resident Inspector ,

McGuire Nuclear Station >

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, 30. There was no question number 30 in the NRC question set on the:

' Duke Reload IDCA Analysis, BAW 10174, Revision O. The following material documents the PCT impact on the LOCA Limits results, reported in section 8 of BAW-10174, due to previously identified . BEACH ' code errors, a chenge in grid design that, impacts _the BEACH input characterization of the grids', and the I

reduction of the metal-water reaction threshold temperature from 1500 F to 1000 F.

4, Response: BWFC. described BEACH, Version 10.0, code errors at

~ length in the response to question 5 of the NRC question set. ,

on the BEACH topical report, BAW-10166, Revision 1. In brief, l the errors-influenced the capability of the code to properly calculate gap heat transfer. Cladding temperatures in the vicinity of rupture were particularly affected. The errors' were corrected in BEACH, Version 11.0, and that code version was validated. against experimental data in response to- ,

question 5. The code updates were made l subsequent to the release of the. Duke Relcad LOCA Analysis. The results i o

presented in Section 8 of- the' Reload Analysis would, therefore, change, although not significantly, with l implementation of the corrections. The results of reflood clad temperature evaluations of the LOCA Limits cases using I the corrected code, BEACH, Version 11.0, are documented in ,

this response.

• In addition to the computer code error corrections noted l above, the current results include the effects of updated grid parameter inputs. Since submittal of the Reload LOCA Analysis report, grid changes, influencing the characterization of flow blockage at grid locations, have been implemented. As a result of this change, grid blockage has been reduced from 55 i

percent to 49 percent for the current evaluation.

Benchmark re-evaluations, using Version 11.0, snow that the code corrections result in reduced cladding temperatures and PCTs, while the grid parameter changes tend to increase clad temperatures. Lower grid blockage reduces droplet breakup and. '

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i steam cooling via interphase heat transfer.- Grid convective t e

effects associated with lower blockage also reduce' heat t

transfer.

The results of the updated loCA Limits calculations are tabulated in Table 30-1. They are compared directly to the results reported in . BAW 10174. It is concluded ' that, in general, the revised evaluation results_in an extended time-to-rupture and lower cladding temperatures. Both the rupture delay and cooler temperatures are a result of corrections in  !

the gap conductance model . implementation. The revised i benchmark' evaluations, included in the response, to BEACH question 5, indicate similar results.' I t

The 6.3-foot LOCA Limits case does not lend itself to a j generalized conclusion.

The location of the PCT in the  ;

revised evaluation changed from node 12 to node 14. This  ;

change is primarily due to the corrected gap model. After .i rupture occurs, the gas modeled within the gap ; is now  :

realistically replaced with steam at the rupture location.  !

Steam, having a lower thermal conductivity than the gap gas, causes a rapid decrease in the ruptured clad temperature.- f This phenomena can also be seen in~ the benchmark re-evaluation. (

Cooler steam and lower cladding temperatures at' 'f the rupture location will cause the adjacent clad temperature j to be cooler as well. The PCT location is consequently transferred downstream to the next grid s p r.n 'a n d the PCT  !

occurs at node 14 (in the revised case). Thus, ti:e results of  ;

the re-evaluation of the 6.3-foot LOCA Limits case are  :

decidedly more realistic than those reported in BAW-10174. i A change _in metal-water reaction threshold temperature, from [

1500 F to 1000 F, was implemented after completing the re-j evaluation of the LOCA limits cases whose results are given in Table 30-1. The change in metal-water reaction methodo1'ogy

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should not significantly alter the PCTs presented in Table 30 -  ;

1, since the reaction is not a dominant energy contributor i l l 2 i

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below 1500.F. This was confinned by a review of the 4.6-foot L6CA limits case, the elevation exhibiting the most severe

. local and whole' core metal-water reaction percentages as well as the highest PCT, using a 1000 F metal-water reaction threshold temperature. The 4.6-foot review case was. performed ,

in response to question 13 of this question set regarding the effect of the threshold temperature on clad oxidation. The PCT results of the 1000 F threshold temperature . case are compared to the 1500 F case, from Table 30-1, 17, Table 30-2.

As expected, the PCTs differ by only 2 F. Figure 30-1 shows the clad temperature responses for ~ the 1000 F threshold ,

temperature case.- In comparing Figure 30-1 with Figure 8-9 of ,

BAW-10174, it is observed that the code,. input, and t

methodology updates do not impact previously established cladding temperature trends. Thus, the results of the LOCA .,

limits cases presented in Table 30-1 remain valid for the-change in metal-water reaction nethodology.

In conclusion, the revised LOCA limits calculations presented in Table 30-1 indicate that linplementing the code corrections-L associated with BEACH, Version 11.0 and updating the grid i i input parameters does not significantly change the cladding temperature behavior given in BAW-10174. 'The maximum change in PCT is shown to be 31 F. The comparison in Table 30-2 using the most limiting, 4.G-foot, case shows that the updated metal-water reaction method has virtually no PCT impact; thus, the results in Table 30-1 are not perturbed. The PCT results shown in Table 30-1 and the response: to . question 13 all- I demonstrate that substantial margins to 10CFR50.46 criteria continue to exist subsequent to the revisions. ,

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.i e! e, Table 30 1- '

Case *

• 98 Peak ~

. 4.6s Peak 6.3' Peak 8.08 Peak- 9.7e Peek l- Para iter a 'i r

Rupture flee, s 89.3 (81.8) 84.0 (74.4)' 75.3 (67.6) - 74.8 ( 73.8 ) . 93.2 (84.4)

Ripture Node 8 (8) 8 (8) - 11 (11)'- 14 (14) l1 15 (15)

PCT Time, a 282 (268) 240 (220) 338 (218) 227 (207)' 220 (346) >

.f PCT Wode 11 (11) 11 (11) 14 (12) 12 (12) 14 (14)

PCT,

• F 1826 (18,16) 1943 (1 % 3) > 1897 (1873) :1899 (1930)

.. 1793 (1823) i Values in parentheses were generated with SEACH, Version 10,' for Table 81 of 8AW 10174 Revision 0.

1500 f metat water reaction cut off. ,

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e lebte 30 2 Case -' 4.6' Peak 4.6' Peak 1500 F Cut Off 1000 F Cut Oif ,

earameter ! $

Rupture Time, a _,%,n 83.2 Rupture Node b 8 PCT fine, a 240 1%

PCT Node 11 11 PCT,

• F 1943 -1945 Values h table were generated with BEACH, Version 1.1 5

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. 1 FIGURE 30-1. LOCA LIMITS STUDY - 4.6-FOOT CASE CLAD IaMPERATURES.

1000 F METAL-WATER REACTION THRESHOLD TEMPERATURE W

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