ML19329A627

Forwards Reanalysis of Locked Rotor Accident.Concurs in Continued Use of BAW-2 Correlation

ML19329A627
Person / Time
Site:	Oconee
Issue date:	04/23/1974
From:	Stello V US ATOMIC ENERGY COMMISSION (AEC)
To:	Moore V US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8001070642
Download: ML19329A627 (5)

Text

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@R E 3 1974 Docket Nos. 50-269 and 50-270 V. A. Moore, Assistant Director for Light Water Reactors Group 2. L LOCKEDROTORANALYSIS(TAR-878)

Plant Name:

Oconee, Units 1 & 2 Docket Nos.:

50-269 & 50-270 Licensing Stage:

Post-OL Responsible Branch LWR 2-3 and Project Manager:

I. Peltier rSTechnical Review Branch Involved:

Core Perfonnance Branch Y*

Requested Completion Date:

May 1, 1974 Description of Review:

Reanalysis of Locked Rotor Accident The Core Performance Branch was requested to detennine if the locked rotor accident analysis for Oconee 1/2 as described in the FSAR is still acceptable under the Tech Spec trip settings for the flux / flow ratio i

proposed by the licensee. The evaluation is intended to be equally i

applicable to Oconee 3. Arkansas 1, and Three Mile Island 1.

Rancho Seco i

was evaluated individually due to slight differences in input parameters.

Our evaluation is provided in the enclosure. The responsible engineer for this task was M. McCoy.

Original Signed by Victor Stello Victor Stello, Jr., Assistant Director for Reactor Safety Directorate of Licensing

Enclosure:

Evaluation Distribution:

cc:

5. Hanauer Docket files A. Giambusso CPB Reading J. Hendrie L Reading A. Schwencer V. Stello D. Ross E. Leins W. Mcdonald S. Varga

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P. Morian I. Peltier M. WSy omer >

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Form AEC-31,(Rev.9-53) AECM 0240 ee

.43--as-sises-a 44s-ets 8001070 [ N

6 LOCKED ROTOR ANALYSIS FOR OC014EE 1/2

SUMMARY

OF EVALUATION As the result of an increase in the delay time of the flux / flow trip in the Reactor Protection System for certain Babcock & Wilcox plants, it was considered necessary to evaluate the effect of the change on DNBR B&W has performed analyses to show that the increased determinations.

Tech Spec trip settings are conservative for the loss-of-flow transient.

The Core Performance Branch has reanalyzed the locked rotor accident using the computer code COBPA-IIIC.

The Oconee 1/2 plant was used as the basic model for the analysis.

The original analysis of the locked rotor accident presented in the FSAR was based on a flux / flow trip delay tiiha of 0.65 seconds and The Core Performance used the W-3 correlation for the determination of DNBR.

Branch has analyzed the accident using both the W-3 and BAW-2 correlations and including the effects of densification. The relevant input parameters are listed below.

Power Level, %

102 Densified Length, in.

141.5 Coolant inlet temp., F 555.5 1.5 cosine Axial flux shape 1.78 Enthalpy rise factor, Fg 8

Spike penalty, %

Geometry and transient parameters As given in FSAR Thermal Diffusion Coefficient (TDC) 0.011 6

~

The reanalysis of the locked rotor analysis for the proposed flux / flow delay time of.1.4 seconds used the same parameters with the exception of revised power decay '?ta supplied by the licensee and considered applicable The core flow and pressure transient for the revised Tech Spec change.

are essentially unchanged.

The analysis for Rancho Seco was essentially the same except for increased design values for coolant flow rate, coolant inlet temperature and average heat flux. The power decay data supplied for Oconee was considered applicable for Rancho Seco.

The results of the reanalysis are summarized in the following i

table:

A MINIMUM DNB RATIO Rancho Seco_

Oconee 1/2 Delay Time W-3 BAW-2 FSAR Delay Time W-3 BAW-2 FSAR (sec)

(sec) 1.0 0.65 1.305 1.655 1.15 0.75 1.075 1.50 1.031 1.262 1.40 1.257 1.537 The eifect of the delay time change on Oconee 1/2 is illustrated in the enclosed Figure 1, using the W-3 correlation for determination of DNB.

The DNBR transient for Rancho Seco with an assumed delay time of 1.5 seconds is also presented.

r l

CONCLUSIONS We find that the locked rotor accident analysis as presented in the Oconee 1/2 FSAR still acceptable under the proposed Tech Spec change in flux / flow trip delay time.

This conclusion is also reached for the other B&W plants. considered in this evaluation.

It should be noted that there is a considerable difference, sometimes as much as 25%, in the results obtained with the two DNB correlations, with BAW-2 giving higher values. We are in the process of reviewing this aspect generically.

However, the B&W correlation is valid over a much smaller range of variables, and as such may be a " tighter" correlation.

I At any rate we concur in the continued use of thg BAW-2 correlation for the time being.

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