ML20039C134

Forwards Supplemental Emergency Core Cooling Analysis in Response to Confirmatory Issue 5 of Cessar SER

ML20039C134
Person / Time
Site:	05000470
Issue date:	12/21/1981
From:	Scherer A ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:	Tedesco R Office of Nuclear Reactor Regulation
References
RTR-NUREG-0630, RTR-NUREG-630 LD-81-096, LD-81-96, NUDOCS 8112280467
Download: ML20039C134 (8)

Text

1 C-E Power Systems Tel. 203/688-1911 Combustion Engineenng. Inc. Teler 99297 1000 Prospect Hill Road Windsor, Connecticut 06095 POWER E SYSTEMS V7d Docket No.: STN-50-Z40F December 21, 1981 LD-81-096 q

// W Mr. Robert L. Tedesco B

Assistance Director for Licensing Ob Division of Licensing DEC 2419OI5NC U. S. Nuclear Regulatory Commission d e ',t_ , . ..L'l f """ ".'- .. /C Washington, D. C. 20555  % r A

Subject:

Supplemental Analysis for NUREG-0630 /QrTE$

%_ s

Dear Mr. Tedesco:

This is in response to Confirmatory Issue number 5 of the CESSAR SER which requires a supplemental emergency core cooling analysis. A draft copy of our response was transmitted informally to your Mr. Chris Grimes on November 30, 1981.

We have received his coments and have incorporated them in the enclosed formal response.

If we can be of any additional assistance, please feel free to contact either myself or Mr. G. A. Davis of my staff at (203)688-1911, Extension 2803.

Very truly yours, COMBUSTION ENGIt'ERING, INL.

1&

Director Nuclear Licensing AES:ctk Enclosure cc: C. Grimes ,

hCO3 s Ifl

!wn8vausa PDR

Introduction and Simnary A supplemental analysis utilizing the three material models of NUREG-0630 (Reference 1) has been perfonned. This supplemental analysis also utilized the heat transfer portion of C-E's alternate ECCS Evaluation Model which is described in Reference 2. The combination of the NUREG-0630 material

models- and the alternate heat transfer model provides results which are l 1es's limiting than the results in the System 80 CESSAR FSAR which were  ;

j obtained using C-E's NRC approved ECCS. evaluation model (Refemnce 3).

i For this analysis, the peak clad temperature decreased by 17 F and the f

peak local oxidation decreased by 5.5%, from the corresponding values

, reported in Section 6.3.3 of the FSAR. Similar results were.provided to i the NRC, in References 4 and 5, for other Combustion Engineering designed PWRs . As in these previous analyses, this analysis illustrates the over-all conservatism of the C-E flow blockage representation in its NRC jL approved ECCS Evaluation Model. (Reference 3).

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Method of Analysis-

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The analysis used the three material models of NUREG-0630 (Reference 1). '

Specifically, the models predict cladding rupture temperature, cladding

- burst strain, and fuel assembly flow blockage. In addition, the analysis utilized the heat transfer portion of the alternate ECCS Model (Reference

2) for the calculation of steam heat transfer coefficients for locations

at and above the blockage plane. All other portions of the calculation used C-E's NRC approved ECCS evaluation model (Reference 3).

~

Figures 3, 8, and 16 in Reference 1 present the NRC recommended rupture i temperature, rupture strain, and reduction in fuel assembly flow area, l~ respectively. This analysis assumed a heating ramp rate of 0 C/sec and utilized the appropriate values from Figure 3 of Reference 1 for rupture temperature along with the maximum rupture strain of 90% combined with the maximum assembly flow blockage of 71%. This approach is a conservative use of the NUREG-0630 models in that it minimizes steam cooling heat trans-Il fer coefficients in the hot subchannel above the blocked region ~. Although this methodology introduces additional, unnecessary conservatism'into the analysis, it was done to provide a simplified approach to implementing 4 NUREG-0630 models, and to provide consistency with previous-analyses (References 4 and 5) which were performed in a similar manner.

Since clad rupture occured during reflood the blowdown hydraulic transient ~

is insensitive to flow blockage modeling. Furthermore, calculation of reflood rates is based on core average behavior and is not affected by l

local blockage. Therefore, the blowdown and reflood hydraulics calculated l for the FSAR analysis remain applicable and were used in this study. The hot rod clad temperature and oxidation values were recalculated using the NUREG-0630 clad material models and the alternate steam cooling heat transfer models. Other input assumptions remain the same as described in Section 6.3.3 of the FSAR. The calculation described above was performed for the 1.0DEG/PD* break, which is the limiting 1arge break. identified by the FSAR evaluation model licensing analysis. This large break is still

'imiting even With the new models. The small breaks will not come close to acceptance limits and therefore are not limiting.

• DEG/PD - Double-Ended Guillotine / Pump Discharge

Results Table 1 sumarizes the significant input parameters and results of this supplemental analysis. The rupture strain is 90%, which corresponds to a flow blockage of 71%. These are the maximum values predicted by the NUREG-0630 models. As mentioned earlier, rupture is predicted during reflood. The rupture temperature of 1510*F is based on the O C/sec heating ramp rate curve. Use of a more representative heating ramp rate would calculate rupture at a higher temperature and would result in a lower rupture strain and flow blockage than the maximum values used here.

As concluded previously in References 4 and 5, the combination of the improved heat transfer of C-E's alternate model with higher strain and flow blockage actually results in a decrease in both calculated peak clad temperature and peak local clad oxidation. For this analysis, the peak clad temperature decreased by 17 F and the peak local clad oxidation

decreased by 5.5% from the corresponding results of the FSAR analysis presented in Section 6.3.3 and presented graphically in Figures 1 and 2.

The results of this study demonstrate that the ECCS analysis results f presented in the System 80 CESSAR FSAR comply with the acceptance criteria of 10CFR50.46 at an asstaned peak linear heat rate of 14.0 kw/ft.

I

References

1. D. A. Powers and R. O. Meyer, " Cladding Swelling and Rupture Models for LOCA Antlysis", NRC Report NUREG-0630, April 1980.

2. Enclosure 1-P of Letter LD-78-069, from A. E. Scherer, C-E, to Dr. Denwood F. Ross, NRC, September 18, 1978.

3. Calculative Methods for the C-E Large Break LOCA Evaluation Model",

CENPD-132, August 1974 (Proprietary).

~

" Updated Calculative Methods fcr the C-E Large Break LOCA Evaluation Model", CENPD-132, Supplement 1, August 1974 (Proprietary).

" Calculative Methods for the C-E Large Break LOCA Evaluation Model",

CENPD-132, Supplement 2, July 1974. (Proprietary).

4. Response to NRC Question 231.34 San Onofre Nuclear Generating System Units 2 & 3, Final Safety Analysis Report, Amendnent #24.

5. Letter from R. E. Uhrig (FP&L) to D. G. Eisenhut, (USNRC),

Subject:

Requests for Additional Infonnation, Nisnber L-81-384, September 3,1981.

1

TABLE I I. Input Parameters and Results of the ECCS Supplemental Analysis PARAETER SUPPLEENTAL ANALYSIS Rupture Strain Model NUREG-0630 Modals (1)

Steam Cooling Heat Transfer Model C-E's Alternate Model (2)

Model for Remainder " Calculation Method for the C-E of Calculation Large Break Evaluation Model".

Allowable Peak Linear Heat Generation Rate (kw/ft) 14.0 Rupture Strain (%) 90.0 Flow Blockage (%) 71.0 Hoop Stress at Rupture (KPSI) 5.25 Clad Temperature at Rupture ( F) 1510 Rupture Time During Reflood II. Comparison of Supplemental and FSAR Analysis Results SUPPLEMENTAL FSAR PARAMETER ANALYSIS ANALYSIS Peak Clad Temperature

( F) 2152 2169 Location Below Blockage Below Blockage Peak Local Clad 0xidation (%) 7.65 13.14 Location Below Blockage At Blockage

FIGURE 1 CLAD TEMPERATURE AT HOT SPOT 2200- i i i i i i

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