ML19340A138

Notifies That Proposed Tech Specs Are Conservative Re Setpoints Based on Denisification Penalty Miscalculations. Forwards Revision 2 to BAW-1425, Cycle 2 Reload Rept

ML19340A138
Person / Time
Site:	Oconee
Issue date:	06/15/1976
From:	Parker W DUKE POWER CO.
To:	Schwencer A Office of Nuclear Reactor Regulation
Shared Package
ML19340A139	List: ML19340A138 ML19340A141
References
NUDOCS 8001100604
Download: ML19340A138 (3)

Text

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'Mr. Benard C. Rusche,-Director t -

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g-Nuclear Reactor Regulation 10 ph Washington, D. C.

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/7 Attention: Mr. A. Schwencer, Chief

\\A Operating Reactors Branch No.1 Re: Oconee Unit 2-

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-Docket No. 50-270

Dear Mr. Rusche:

In letters dated February 25, 1976 and May_7, 1976, revisions to the Oconee Nuclear Station Technical Specifications were requested to support-the opera--

tion of Oconee 2, Cycle 2.

Subsequent to those submittals, an error has-been identified in the Oconee 2, Cycle 2 DNBR densification penalty calculations.

This error has:resulted from the use of inconsistent heat flux (flux shape) and enthalpy rise calculations in evaluating the DNBR densification penalty.

The revised calculations indicate that the change (reduction) in DNBR margin.

due to densification effects should be 5.93 percent and the change (reduction) in power peaking margin should be 3.47 percent instead 'of the previously reported values of 1.88 percent and 1.06 percent, respectively.

In the analysis incorporating the revised DNBR densification penalty, the Removal of penalty' for an assumed open internals vent -valve was deleted.

.the penalty for an open vent valve was' addressed by the Commission's letter dated January 30, 1976 and proposed Technical specifications submitted

. pursuant thereto'on June 11, 1976.

The pressure-temperature limit curve based.upon the internals. vent valves

? remaining closed and' incorporating'the revised densification penalty is approximately 30F less restrictive (maximum allowable temperature will be -

Since' 30F higher'at a given pressure) than the previously submitted curve.

1the variable low: pressure trip setpoint is based upon the four-pump pressure-

-temperature _ limit curve,'the'previously proposed variable low pressure trip setpoint also continues to "oa. conservative.

,j The flux / flow trip setpoint is based'upon-a two-pump.coastdown analysis.

When the revised densification penalty is incorporated and the penalty for

'an assumed open vent valve-is removed, a flux / flow trup setpoint of 1.08 Nbi j -

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Mr. tenard C.' Rusch 3! -

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-; June;15, 1976~

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1.2' percent error to account

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d can.be justified. This setpoint also-inclu es a flow instrument-string.

]-l, for the precision of. various components in.the RPS 2, Cycle.2.-

The previously proposed flux / flow trip setpoint is 1.07 for Oconce-

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ed for Oconee 2, Cycle 2 are-1

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i Therefore,'the specifications previously proposconservative with ified based :upon.

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.the. incorporation of the. revised densi

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' penalty. for-an assumed ' open internals vent valve.

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f ed during Surveillance: of.the Oconee 2 internals. vent valves will' be per orml Specificati

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this refueling outage in accordaa.?e with the Technica in our June 11, 1976 submittal.

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"Oconee 2, Cycle 2 Reload Report,"

Revision 2 to. Babcock and Wilcox BAW-1425,- l tical method and results.

is attached to reflect the above changes in:ana y Very truly yours, a

Wil11aml 0. ' Parker,- J t

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