ML19319B455
| ML19319B455 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 07/01/1977 |
| From: | Roe L TOLEDO EDISON CO. |
| To: | Stole J Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8001220862 | |
| Download: ML19319B455 (5) | |
Text
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1,. e s NRC DISTR'IBUTION pcR PA-50 DOCKET MATERIAL FROM:
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Mr. John F. 5*tolz Toledo Edison 07-01-77 Toledo, Ohio 43652 df 'Of'M Lowell E. Roe NoToRIZ E D PROP INPUT PoRM NUMBER oP COPIES RECEIVEo
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%.lGIN AL NCLAS$1 PIED CCoPY ENCLoSU RE Consists of Table 1 " Input Parameters EsCDPTioN Ref John F. Stolz ltr. dated 03-237 For Tafy Computer Chde C Table 2 " Comparison Of
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o TOLEDO EDISON LOWELL E. ROE vice pees.eeni s.ca.i. o 44193 259-5242 Docket:
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'JH Regulatory Docket file JS;,
3" 7 977 Serial No.:
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JUL 51977,.
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s Director of Nuclear Reactor Regulation
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's Attn:
Mr. John F. Stolz, Chief N
5 Light Water Reactor Branch No. 1 Division of Project Management United States Nuclear Regulatory Commission Washington D. C.
20555
Dear Mr. Stolz:
With reference to your letter of March 23, 1977 (J. F. Stolz to L. E. Roe),
concerning fission gas release (FGR), it is estimated that a local exposure (burnup) of 20,000 MWD /MTU will not occur prior to a core average exposure of approximately 410 EFPD, and that no fuel rod in a Davis-Besse Unit 1 core will reach a burnup greater than 22,000 MWD /NTU during the first cycle of operation. First cycle operation is expected to be completed in spring of 1979.
The attached Table 2 presents the results of comparative analysis performed with the TAFY computer code both with the B&W FGR release model and with the modified (NRC) gas release model. The input parameters and TAFY NRC restrictions used in the comparison can be found in Table 1.
The input data used for both FGR models chosen was identical for both cases.
Therefore, all differences in the calculational results can be attributed soley to the fission gas release model utilized (NRC versus B&W).
The TAFY code without the NRC FGR equation is the code which has been used for LOCA and safety analyses on Davis-Besse Unit 1 fuel. Use of the NRC FGR equation in TAFY would eventually impact LOCA analysis (after the first first fuel cycle) as the highest pin pressures would now occur at earlier burnups than previously calculated. Since initial inside and outside cladding surface oxide layers would be thinner at a lower burnup, the zircaloy-water (metal-water) reaction would be larger than that previously calculated. The increased energy generation in the cladding would raise the peak cladding temperatures and would probably result in exceeding the LOCA limits of 10 CFR 50.46.
Recualification of THE TOLEDO EDISON COMPANY EDISCN PLAZA 300 MADISON AVENUE TOLEDO. CHIO 43652
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LOCA limits would probably be necessary, ultimately resulting in the issuance of revised Technical Specifications. However, prior to the first refueling it is anticipated that the NRC will have reviewed and approved the B&W TACO model which will predict acceptable temperatures at higher burnups.
A survey of the non-LOCA related safety analysis accidents was performed and it was concluded that the NRC FGR model would not affect the results.
The average fuel temperatures used in the transient cladding temperature calculations is not changed by the new NRC FGR model. Further, the higher pin pressures at end of life would not result in cladding rupture during these transients. Hence, the non-LOCA safety analysis accidents are not impacted by the NRC FGR model.
The TAFY analysis with the NRC FGR model will predict a pin pressure slightly in excess of nominal system pressure at a burnup of 38,000 MWD /MTU. For the present cycle no fuel rod in the core (Core I) will achieve a burnup of this magnitude. The implications of operations with j
an internal fuel rod pressure greater than the nominal coolant system pressure will be addressed, if such operation is predicted, in reload licensing applications.
Yours very truly, Enclosures sf d/3 f
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TABLE 1 PIN PRESSURE ANALYSIS UNIT
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DAVIS-BtSSE C';IT 1 INPUT PARAMETERS FOR TAFT COMPUTER CODE TUEL INITIAL 1EAN dei;SITY - % TD
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' 96 0 INITIAL ~ 1EAN DIA!ETER - IN 0.3675
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INITIAL LTL DC;SITY - % TD 94.5
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FINAL DENSITY - % TD 96.5 DISH RADIUS - IN 0.1475 DISH FACTOR 0.01848 INITIAL STACK LC'GTE - IN 143.5 CLAD CLAD ID - IN d,377 CLAD OD - IN 0.430 CLAD LE;GTH - IN 153.125 INITLtL PLENDI VOLC4E - I'i O'.7862 INITIAL BACKFULL PRESSURE - PSIA 480.0
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TABLE 2 DAVIS-BESSE UNIT 1 COMPARISON OF PIN PRESSURE TAFY BSW FGR MODEL TAFY NRC FCR MODEL PEAK ROD BURNUP PIN PRESSURE PIN PRESSURE-(MWD /MTU)
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(psia) 20,000 1625 1625 22,000 1639.
1641 25,000 1689 1710 27,000 1708 1740 30,000 1784 1855 32,000 1831 1935 35,000 1905 2098 37,000 1953
~2210 38,000 1980 2265 6
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