ML19341A702

Updated LER 78-001/01T-2:on 780106 B&W Identified Transients Which May Result in Exceeding DNBR on Kw/Ft Safety Limits. Caused by Positive Difference Between Indicated Reactor Power Subtracted from Actual Reactor Power

ML19341A702
Person / Time
Site:	Three Mile Island
Issue date:	01/22/1981
From:	Mitchell D METROPOLITAN EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19341A700	List: ML19341A699 ML19341A702
References
LER-78-001-01T, LER-78-1-1T, NUDOCS 8101270726
Download: ML19341A702 (2)

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Ioi21i Further contact with our NSSS (B&h has identified certain transients which may result in e'xceeding DNBR or IG/f t safety limits, This could  ;

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I,io } l The above conclusion is from analyses performed for the WPPSS-WNP 1/4 FSAR.

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TLL 621 LICENSEE EVE'T REDORT NARRATIVE REPORT TMI-l LER 78-001/01T-2 Event Descriotion and Consecuences Met-Ed has been informed by the NSSS vendor, B&W, that B&W's continuing investigation into the conditions which led to LER 78-01 has identified certain transients where the difference induced by the transients between the reactor power as indicated by the out-of-core instrumentation and the actual reacter power =ay result in exceeding DNBR or kW/ft safety limits.

With regard to the concern, B&W has made a preliminary assessment o' the potential effects of flux errors as large as 15% FP. Indications are that if induced flux errors as large as 15% FP were to occur, the DNBR and kW/ft limits could be maintained if the plant is operated within the bounds of the currently approved plant operating limits. At this time it is felt that there was no signi.~1 cant reduction in the margin of safety during past operation.

Event Cause and Corrective Action Met-Ed is pursuing additional clarification of the pctential problem with B&W to further define the transient errors involved and any corrective action necessary to mitigate their effects. The NRC

' will be kept informed of any new developments in this area.

The basis for the B&W conclusion is from analyses performed for the WPSS-WNP 1/4 FSAR (a 205 FA plant). The investigation has not encompassed any plant specific analysis for the 177 FA plants. The events identified are outside the scope of the TMI-1 Chapter 14 FSAR analyses.