ML19210A474
| ML19210A474 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/15/1977 |
| From: | Herbein J METROPOLITAN EDISON CO. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| GQL-0925, GQL-925, NUDOCS 7910300510 | |
| Download: ML19210A474 (5) | |
Text
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Roi5ert W. Reid Metropolitan Edison Co.
7/15/77 Reading, PA o47: RacgivEo J. G. Herbein 7/21/77 TrE R 2 NOTO RIZE D PROP INPUT PORM NUMSER CP COPtES RECEIVED RIGINAL
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3-y-}9 IM Results of the current GPUSC analysis of the NRC proposed burnup dependent fission gas release model show that the
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internal pin pressure of the peak burnup rod (cycle 3) will not exceed system pressure at expected end-of-life exposure.
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GQL 0925
- 7. ~E 'l{ d.' C hdOI b Director of IIuclear Reactor Regulation Atta:
Mr. R. W. Reid, Chief Operating Reactors Branch :To. k U. S. :Iuclear Regulatory Co=nission Washington, D. C.
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Dear Sir:
Three Mile Island Nuclear Station, Unit 1 (TMI-1)
Docket No. 50-289 Operating License No. DPR - 50 Our letter to you of March h, 1977, presented interim results of our inde-pendent analysis of the NRC proposed burnup dependent fission gas release model. The analysis was undertaken by GPU Service Corporation (GPUSC), on behalf of Metropolitan Edison Co., in order to evaluate the B&W response to the new model as well as to provide us with a clearer understanding of the potential effects of the new model on fuel performance and future licensing efforts.
The preliminary results, reported in our March h, 1977 letter, indicated that the peak rod internal pressure vould exceed system pressure at approx-imately 32,000 MID/ CM, prior to expected end-cf-life for the fuel in Cycle 3 cf Three Mile Island Nuclear Station, Unit 1.
"'he analysis was performed using an in-house version of the GAPCON-THERMAL-2 fuel performance code which was modified to incorporate both the B&W (TAFY) and the NRC fission gas re-lease models. Fin pressures calculated using the NRC enhancement model showed an increasing difference for burnups above 20,000 :GD/ CM between the TAFY and GAPCON results. These discrepancies were suspected to be due in large part to inaccuracies in certain GAPCON models and also to uncertainties in the input used for the GPUSC analysis.
1491 059 772020310
- Director of Nuclear Reactor Regulation July 15, 1977 Attn:
Mr. R. W. Reid, Chief GQL 0925 Further investigation, following our thrch 4,1977, letter, revealed that GAPCON was generating significantly higher amounts of fission gas than TAFY or other fuel performance codes considered generally reliable. The source of this discrepancy was traced to the algorithm in the program which evaluates the fission gas production.
This algorithm, which is unique among the fuel performance programs with which we are familiar, is thought to be in error since its gas production is significantly dif-ferent from the other programs.
GAPCON gas production was th.'efore ad-justed to match that of TAFY. Also, discussions with B&W provided more accurate input infor=ation, particularly in regard to the power level and history assumed for the peak rod.
Results of the current GPUSC analysis show that the internal pin pressure of the peak burnup rod for TMI-1, Cycle 3 vill not exceed system pressure (2185 psi) at expected end-of-life exposure (% 34,000 WD/MTM). This con-clusion is in accord with the B&W reported results.
Because there is some question as to the appropriateness of incorporating the models of one code into another without more general modeling adjust-ments, the GAPCON code was also run for the TMI-1 peak rod using the orig-inal GAPCON gas release model with the proposed NRC burnup enhance =ent.
Since the GAPCON gas release already has a slight burnup dependence, the model was adjusted in accordance with NRC recon =endations (i.e., the orig-inal burnup variable is limited to 20,000 WD/EM). Results confirmed that the peak rod internal pressure remains belov system pressure at end-of-life and, in fact, gave pressures consistently lower than those reported by B&W.
Comparisons of the pin pressures calculated by the TAFY and GAPCON codes, both with and without the proposed NRC model, indicate that the differences among the results are within the variation lLnits expected ancng state-of-the-art fuel performance codes. The largest effect of increased pressures using the NRC enhance =ent is given by the GAPCON code with the TAFY gas release =odel.
As in the preliminary GPUSC results, this version of GAPCON gave pressures whose differences from corresponding TAFY pressures increased with burnup. GAPCON results using the original GAPCON gas release model showed pressure increases due to the NRC =cdel that were much more consistent with the TAFY values. Predicted pressures at end-of-life for the TMI-1 peak rod with and without the proposed NRC model are shown in Attachment 1.
As can be 1491 060
, Director of Nuclear Reactor Regulation July 15, 1977 Attn:
Mr. R. W. Reid, Chief GQL 0925 seen all of the results show end-of-life pressures below TMI-l system pres-sure and therefore preclude the necessity of discussing the consequences of operation with tensile stresses in the cladding.
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J. G. Herbein Vice President JGH:JMC: Jag
Attachment:
Predicted End-Of-Life Pressures 1491 061
Attachment ?Tc. 1 PREDICTED ETD-CF-LIFE
- PRESSURES, PSI
'lithout IGC Model
'4ith !GC Model TAFY (3&'4 Results) lh57 1702 GAPC0ti v TAFY Release Model 1288 2000 GAPCOT v GAPCCII Release Model 1135 1h52
- EOL =aximum expected rod average burnup = N3h,000 'GD/?ct 1491 062