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This report documents our preliminary eval … This report documents our preliminary evaluation that in the event of a main steam line break accident (MSLB) with a coincident failure of a main feedwater regulating valve (MFRV) to close, the internal pressure of the containment structure may briefly exceed the FSAR design pressure of 60 psig. The MSLB with MFRV failure to close has not been previously evaluated for PBNP at the presently licensed thermal power. However, an analysis of this accident under up-rated licensed power conditions has been completed. Based on an evaluation of the information provided in that analysis, the plant may be in an unanalyzed condition. Our evaluation of this condition indicates that the integrity of the containment structure would not be challenged by this postulated event, and; therefore, the safety significance of this condition is low. We are conservatively providing this event report as a follow-on to our June 7, 2001, 10 CFR 50.72 notification.</br></br>A revised calculation for the MSLB with MFRV failure to close has been performed with the results indicating a peak containment pressure of 59.8 psig. This calculation included changes to the initial conditions for initial containment pressure and end of cycle shutdown margin which will be administratively controlled until suitable Tech Spec changes have been implemented.e Tech Spec changes have been implemented. +
This report documents our preliminary eval … This report documents our preliminary evaluation that in the event of a main steam line break accident (MSLB) with a coincident failure of a main feedwater regulating valve (MFRV) to close, the internal pressure of the containment structure may briefly exceed the FSAR design pressure of 60 psig. The MSLB with MFRV failure to close has not been previously evaluated for PBNP at the presently licensed thermal power. However, an analysis of this accident under up-rated licensed power conditions has been completed. Based on an evaluation of the information provided in that analysis, the plant may be in an unanalyzed condition. Our evaluation of this condition indicates that the integrity of the containment structure would not be challenged by this postulated event, and; therefore, the safety significance of this condition is low. We are conservatively providing this event report as a follow-on to our June 7, 2001, 10 CFR 50.72 notification.</br></br>A revised calculation for the MSLB with MFRV failure to close has been performed with the results indicating a peak containment pressure of 59.8 psig. This calculation included changes to the initial conditions for initial containment pressure and end of cycle shutdown margin which will be administratively controlled until suitable Tech Spec changes have been implemented.e Tech Spec changes have been implemented. +
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