ML20246P245

Application for Amends to Licenses DPR-24 & DPR-27, Consisting of Tech Spec Change Request 129 Eliminating Function from Overpower Delta-T (Opdt) Setpoint to Increase Flexibility of Operation at Full Power

ML20246P245
Person / Time
Site:	Point Beach
Issue date:	03/17/1989
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20246P252	List: ML20246P245 ML20246P259
References
CON-NRC-89-035, CON-NRC-89-35 VPNPD-89-166, NUDOCS 8903280167
Download: ML20246P245 (4)

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Wisconsin Electnc POWER COMPANY 231 W. Michigart PO. Box 2046. Mdwoukee, WI S3201 (414)221-2345 VPNPD-8 9 -16 6 NRC- 8 9 -0 3 5 March 17, 1989 Document Control Desk 10 CFR 50.59 U.S. NUCLEAR REGULATORY COMMISSION Mail Station Pl-137 Washington, D.C. 20555 Gentlemen:

DOCKETS 50-266 AND 50-301 TECHNICAL SPECIFICATION CHANGE REQUEST 129 OVERPOWER DELTA-T SETPOINT REVISION POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 In accordance with the requirements of 10 CFR 50.59(c), 50.90, and 50.4, Wisconsin Electric Power Company (Licensee) hereby requests an amendment to Facility Operating Licenses DPR-24 and DPR-27 for Point Beach Nuclear Plant, Units 1 and 2, respectively, to incor-porate a change in the plant Tecnnical Specifications. The pro-posed change provides for the elimination of the f(aI) function from the Overpower Delta-T (OPDT) setpoint to increase the flexi-bility of operation at full power by allowing use of the full flux difference operating envelope.

The flux difference operating envelope proposed in Technical Specification Change Request 127 allows a flux difference at full power of +9 percent. The Technical Specification required delta flux penalty for the OPDT trip setpoint is +9.5 percent at full power. The setpoints of approximately +6.5 percent delta flux for turbine runback and approximately +7.5 percent delta flux for reactor trip are currently used to encure that the Technical Specification setpoint limit is not violated. These actual setpoints account for instrument calibration drift. With these conservative setpoints and the revised flux difference operating envelope, the plant cannot be operated normally with all rods out 4

40 and at full power during the beginning of each fuel cycle without causing a runback or a trip. Elimination of the f( AI) function D9$ (justified below) has been chosen as the preferred solution. It Qg on will allow normal operation at full power with all rods out at any "O time during core life, and it will allow the flux difference operating envelope to be fully utilized. The alternative is to j gf operate the core with rods partially inserted to decrease the

-o power at the top of the core, thereby reducing the positive axial

$$ offset. This alternative is undesirable in a PWR because it Q increases the exposure of the control rods, thus decreasing their om service life, and creates burnup patterns in the fuel which are

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not economically optimum. Further, it unnecessarily limits plant operational maneuverability during power swings and transient recoveries.

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Document Control Desk March 17, 1989 Page-2 The specific Technical Specification change for the removal.of the f(AI) function from the OPDT setpointEis identified with-margin bars on the. attached proposed Technical Specification pages. Please note that the attached page 15.2.3-3 does not

include'those changes presently pending NRC approval under Change Request No. 127' dated August 26, 1988, as amended.

The design bases of the OPDT and the Overtemperature Delta-T setpoints are presented in WCAP-8745-P-A, " Design Bases.for the Thermal Overpower AT and Thermal Overtemperature oT Trip Func-l tions,"~ September 1986. LAn NRC Safety; Evaluation Report dated April 17, 1986 accepted this.WCAP for referencing.- The OPDT setpoint is-intended to. protect against fuel centerline melting in Condition II transients. However, .this WCAP concluded that no f(aI) function is required to preclude fuel centerline melting-during overpower events in 16x16 and 17x17 fuel plants. .The WCAP also concluded that the OPDT trip setpoints (including the f(aI) adjustment) for 14x14 and 15x15 fuel plants were established in a more conservative manner than required to' prevent fuel centerline melting. Therefore, 14x14 and 15x15 plants can be evaluated in.

accordance with the WCAP methodology to justify removal of the f(AI) function on a plant-specific basis.

Analyses were performed for PBNP based on the proposed flux difference operating envelope. Condition II events were analyzed for control bank and boration/ dilution system malfunctions, which are potentially limiting during. overpower events. An overpower limit of 114 percent, based on a nominal Technical Specification value of 108.9 percent, was used for all values of AI.(i.e., no f(aI) penalty was applied). It was confirmed that the resulting overpower conditions did not yield a~ linear power density that would cause fuel centerline melting. 'The f(aI) function can therefore be removed from the OPDT'setpoint calculation with no adverse impacts to safety. Figure'1,(attached) graphically demonstrates the current and proposed OPDT setpoints in their relation to the proposed flux difference operating envelope and the OTDT setpoint.

Significant Hazards Evaluation As required by 10 CFR 59.91(a), we have evaluated this' proposed change in accordance with the standards specified in 10 CFR 50.92 to determine if the proposed change constitutes a significant hazards consideration. A proposed license amendment involves no significant' hazards consideration if operation of the facility in accordance'with the proposed amendment would not (1) involve a significant increase in the probability or consequences of an accident previously evaluated, (2) create the possibility of a new

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' Document Control Desk March'17, 1989 Page 3-or different kind of accident from any accident previously evaluated, or (3) involve a significant reduction in a margin'of safety. Based on the~following evaluation, we have' concluded.that this proposed Technical Specification change will not' constitute a significant hazards consideration.

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As d2scussed above, this change involves a revision to the OPDT setpoint described in' Technical. Specification 15.2.3.lB(5).

'The f(al) function will be removed >from the OPDT setpoint to increase the flexibility of plant operation at full: power as described above. Additionally, we propose'to remove the state-mentsthat the OPDT trip setpoint includes correctionsLfor axial power distribution as found in the basis forithis specification on page 15.2.3-5. . Qhis is necessary since.the setpoint would no longer include that correction, t

1. Probability or Consequences of'Previously-Evaluated Accident Revi sion of the - OPDT setpoint calculation will not'signifi-cantly ' increase the probability or consequences of an accident previously analyzed. The OPDT setpoint helps to ensure that the Core Safety Limits are not violated. These limits are used to determine the acceptability of.the consequences of certain design-basis events and as such have no effect on-the-probability of those events occurring. Analysis of Condition II events for control bank and dilution /boration system mal-functions without the f(AI) penalty included in the OPDT set-point confirmed that the resulting overpower conditions did not yield a linear power' density that would cause' fuel center-line melting. The core Safety Limits.will therefore not be adversely impacted,.and there will be1no significant increase in the consequences of an. accident previously' evaluated. "

2. Possibility of.New or Different Kind of Accident s

This change does not involve'any physical modifications to -)

the Point Beach cores, only a minor change in a setpoint to increase operational flexibility. The proposed change, therefore, cannot create the possibility for a new or differ-ent kind of accident from any. accident previously- evaluated.-

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3. No Significant Reduction in a Margin.of Safety One of the functions of the Core Safety Limits is to' prevent 1 fuel centerline melting. The OPDT setpoint is determined to.

i ensure that the Core Safety Limits fulfill this function. I Although the f(AI) function is being removed from the OPDT.

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Document Control Desk March 17, 1989 Page 4 setpoint, the analysis described above has demonstrated that the Core Safety Limits will not change and will not be exceeded. The OPDT change therefore has no impact on the prevention of fuel centerline melting, and thus does not involve a significant reduction in a margin of safety.

We hereby request that the change described herein be approved and issued by the NRC to coincide with the PBNP Unit 1 Cycle 17 start-up in the spring of 1989, and for the Unit 2 Cycle 16 start-up in l the fall of 1989. Unit 1 is expected to be in a refueling shut-  !

down from about March 31, 1989,.through May 10, 1989. Unit 2 is {

scheduled to begin Cycle 16 on November 17, 1989. While it is not )

necessary to have this change in place at start-up to permit cperation of the units during these cycles, it would be both con- ]

.j venient and desirable to implement these changes at that time. j Please contact us should you have any questions regarding this submittal.

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l Very truly yours, j

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C. W. F'ay i Vice President Nuclear Power l

Attachments Copy to NRC Regional Administrator, Region III NRC Resident Inspector Subscribed and sworn to before me this Qgil day of March, 1989.  !

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'% Y Notary Public, State'hf Wisconsin My Commission expires f-27-9d I

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