ML20076L574

Forwards Bounding Analytical Assessment of NUREG-0630 Models on LOCA & Operating Kw/Ft Limits, in Response to

ML20076L574
Person / Time
Site:	Three Mile Island
Issue date:	07/14/1983
From:	Hukill H GENERAL PUBLIC UTILITIES CORP.
To:	Novak T Office of Nuclear Reactor Regulation
Shared Package
ML20076L576	List: ML20076L574 ML20076L580
References
RTR-NUREG-0630, RTR-NUREG-630 5211-83-194, NUDOCS 8307190235
Download: ML20076L574 (2)

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GPU Nuclear Corporation Ng g{ Post Office Box 480 Route 441 South Middletown, Pennsylvania 17057-0191 717 944-7621 TELEX 84 2386 Writer's Direct D!al Number:

July 14, 1983 5211-83-194 Office of Nuclear Reactor Regulation Attn: T. I. Novak, Assistance Director Divisior. of Licensing U. S. Nuclear Regulatory Commission Washington, D.C. 20555

Dear Sir:

Three Mile Island Nuclear Station, Unit 1-(TMI-1)

Operating License No. DPR-50 Docket No. 50-289 NUREG 0630 Cladding Swell and Rupture Models for LOCA Analysis -

In response to your letter of July 13, 1982 and as discussed in our letter of ~

April 4, 1983 (5211-83-097), enclosed please find.the " Bounding Analytical Assessment of NUREG 0630 on LOCA and Operating kw/ft Limits" for TMI-1.

The B&W Owners Group has been evaluating the impact of NUREG 0630 models on LOCA kw[ft Limits. The attached report summarizes the results of-these analyses. This assessment is generic to all B&W 177 Fuel Assembly lowered-loop plants and employs offsetting margins derived from a compensating model ,

as allowed in your July 13, 1982 request.

An ECCS bounding analysis was performed using the basis methodology describ'ed in BAW 10104, Rev. 3 for a 8.55 ft. double ended cold leg rupture. The LOCA limit for the 2ft core elevation was calculated corisidoring the models in NUREG 0630 in a bounding fashion. Analyses were perfbrmed with and without the use of FLECSET as a compensating model for the prediction of reflooding heat transfer. The FLECSET model was derived from recent FLECHT-SEASCT heat ,

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transfer data.

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emo pga. The evaluations demonstrated that a 0.5 kw/ft reduction in LOCA kw/ft limits oo at the 2, 4' and 6 f t. elevations was required to predict acceptably. '

$$ conservative peak clad temperature responses when the model of NOREG-0639 o were used in a bounding fashion in the Large Break LOCA Evaluation model.

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'$8 The FLECSET code, for the prediction of reflooding heat transfer was _ also y

ts used, as a compensating model. The increased heat transfer at the lower core elevations predicted by FLECSET results in sufficient reduction of peak clad

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$$ temperature to compensate for 0.5 kw/ft linear heat rate at the 2 an'd 4,tt.^

011 core elevations. The effect was not applied to the non-critical 6 foot f elevation as described in the enclosure. - /

GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation Y

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l Mr. T.,H. Novak 5211-83-194 This assessment of the' impacts'on LOCA kw/ft limits of SUREG 0630 bounding models and the FLECSET compensating model fulfills'the Staff request (July

. 1982) for supplemental ECCS calculations to evaluate NUREG 0630 models.

Based on these results, and especially the ability of the FLECSET model to offset the NUREG 0630 0.5 kw/ft penalty at the controlling 2-foot elevation,

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we:believe that additional studies are not warranted. Full justification for the use of FLECSET, based on benchmarks to experimental data and comparative sensitivity studies, will be provided in August 1983 to supplement the bases for the results presented in the attached report.

Implementation of the NUREG 0630 models, without utilizing the FLECSET margin offset results in more restrictive core operating limits above 80%

FP and only during the first 31 EFPD of Cycle 5. Although the ECCS evalua-tion results .using the NUREG 0630 data do not constitute a safety concern, and in the event that the FLECSET of fset has not been allowed by the NRC Staff before TMI-l restart, GPUN will administratively implement revised operating ~1imits that account for these penalties prior to exceeding 80%

full power during the first'31 EFPD of Cycle 5 operation.

These penalties are not considered a singificant concern for TMI-l during Cycle 5. Current plans for TM1-1 restart include lengthy hold times at lower power levels before escalation above 80% power. It is estimated that the core will accumulate 30 to 40 EFPD at the lover powers. As described in the attached report (Table 4-2), the kw/ft penalty at the 2-foot level is significantly reduced after 1000 mwd /mtu (approximately 31 EFPD for the TMI-l core) since the fuel condition that cause the major portion of the penalty only occur at beginning-of-life. Therefore, it is likely that the large impact at the 2-foot level will not affect actual TMI-1 operating condition.

S cerely, H D. Hukill s

Director, TMI-l HDH:LWH:vj f Enclosure cc: J. F. Stolz Dr. T. E.'Murley, Regional Administrator Region-I i

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