ML20101B571

Application for Amends to Licenses DPR-24 & DPR-27, Consisting of TS Bases Change to Eliminate Dropped Rod Turbine Runback & Rod Withdrawal Stop

ML20101B571
Person / Time
Site:	Point Beach
Issue date:	05/29/1992
From:	Link B WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20101B574	List: ML20101B571 ML20101B581
References
CON-NRC-92-056, CON-NRC-92-56 VPNPD-92-199, NUDOCS 9206040200
Download: ML20101B571 (2)

Text

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. Wisconsin Electnc POWER COMPANY 231

• Mcngart Po Ba 2046 Nwo>ee # 53201 (414)221-2345 VPNPD 199 NRC 056 May 29, 1992 U.S. NUCLEAR REGULATORY COMMISSION Document Control Desk Mail Station P1-137 Washington, D.C. 20555 Gentlemen:

DOCKETS 50-266 AND 50-301 TECHNICAL SPECIFICATION BASES CHANGE ELIMINATION OF DROPPED ROD TURBINE RUNBACK AND ROD WITHDRAWAL STOP POINT BEACH NUCLEAR PLANT UNITS 1 AND 2 During 1991. Point Beach Nuclear Plant Unit 1 experienced five turbine runbacks generated by the NIS dropped rod runback feature.

These runbacks were generated by spurious signals from the NIS detectors. They were not the result of actual dropped rods. In LER 91-012-01 dated N::e rmber 27, 1991, for Point Beach Nuclear Plant Unit 1, we stated our intent to implement analysis methodology tnat will allow removal of the dropped rod turbine runback feature. Elimination of this function would prevent inadvertent actuations of the turbine runback circuits which puts the plants through unnecessary transients.

The NIS turbine runbach and dropped rod runback generated by the rod bottom bistables were intended to serve as protection for a dropped Rod Control Cluster Assembly (RCCA), reducing reactor power to ensure Departura from Nucleate Boiling (DNB) limits are not exceeded. Analysis shows that the protective actions provided by the NIS turbine runback, rod bottom bistables, and rod withdrawal block are not necessary to prevent DNB limits _from being excetied.

The analysis is based on the calculation methodo]ogy described in WCAP-11394-P-A, " Methodology for the Analysis of the Dropped Rod Event," January 1990. WCAP-11394-P was accepted for use in an NRC Staff Safety Evaluation Report dated October 23, 1988.

We have evaluated the elimination of the turbine runback and rod withdrawal block as protective actions in the event of a dropped RCCA in accordance with the standards in 10 CFR 50.59, and have determined that removal of these features does not involve an unreviewed safety question for the operation of Point Bea'ch Nuclear Plant Units 1 and 2. With the NIS and rod bottom bistable turbine >

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Document Control Desk May 29, 1992

' Page 2 runbacks and rod withdrawal stop features removed, plant response to a dropped RCCA will be slightly different than_with these features in place. Instead of a turbine runback along with the resultant decrease in reactor power, RCCAs will begin to step out in an attempt to maintain power as determined by turbine steam demand. This may result in an RCS pressure and temperature decrease. Depending on the moderator temperature coefficient, the reactor will reach new steady-state conditions, trip on low pressurizer pressure, or runback due to Overtemperature Delta-T.

Analysis shows, regardless of the normal reactor response, DNB does not occur and the consequences of a dropped RCCA do not increase.

Taerefore, we are eliminating the dropped rod turbine runback generated by the NIS and rod bottom bistables as well as the rod withdrawal block. We performed modifications to remove these features during the present Unit i refueling outage and will modify Unit 2 during its fall 1992 refueling outage.

The only direct reference to the dropped rod protection features in the Point Beach Nuclear Dlant Techniccl Specifications is in the bases for Section 15.3.5, " Instrumentation System." The bases presently states, " Testing of the NIS power range channel requires bypassing the dropped rod protection from the NIS, for the channel being tested. However, the Rod Position System still'provides the dropped rod protection." We have deleted this statement from the bases since it will no longer be true with the removal of the dropped rod turbine runback features. A revised Technical Specification page with this change indicated is attached. Please include this change in your copy of the Point Beach Nuclear Plant Technical Specifications.

There are no Limiting Conditions of Operation definett in the Technical Specifications for the dropped rod turbine runback feature. Technical Specification Table 15.4.1-1, " Minimum Frequencies for Checks, Calibrations, and Test of Instrument Channels," Iten 9, requires a monthly test of analog rod position.

Our procedures for accomplishin; this monthly test include a test of the dropped rod turbine runback feature of the rod bottom bistables. Although this portion of the test will no longer be applicable with this feature removed, monthly testing of analog rod position will continue.

If you have any questions concerning this change, please contact us.

Sincerely,

[p

• Bob Link Vice President Nuclear Power Copy to NRC Resident Inspector NRC Regional Administrator, Region III

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