NPL-98-0431, Application for Amends to Licenses DPR-24 & DPR-27,modifying TS to Provide Specific Numerical Setting for Rt,Rcp Trip & AFW Initiation on Loss of Power to 4 Kv Buses.Rev 1 to Calculation 9334281-01 Re RCP Internal Voltage Decay,Encl

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Application for Amends to Licenses DPR-24 & DPR-27,modifying TS to Provide Specific Numerical Setting for Rt,Rcp Trip & AFW Initiation on Loss of Power to 4 Kv Buses.Rev 1 to Calculation 9334281-01 Re RCP Internal Voltage Decay,Encl
ML20248C656
Person / Time
Site: Point Beach  NextEra Energy icon.png
Issue date: 05/28/1998
From: Kaminskas V
WISCONSIN ELECTRIC POWER CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20248C660 List:
References
NPL-98-0431, NPL-98-431, NUDOCS 9806020217
Download: ML20248C656 (10)
v • d • e


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Wisconsin Electnc POWER COMPANY Point Beach Nuclear Plant (920) 755-2321 6610 Nuclear Rd.. Two Rivers. WI 54241 NPL 98-0431 May 28,1998 Document Control Desk U.S. NUCLEAR REGULATORY COMMISSION Mail Station Pl-137 Washington, D. C. 20555 Ladies / Gentlemen:

DOCKETS 50-266 AND 50-301 TECHNICAL SPECIFICATIONS CIIANGE REOUEST 203 UNDERVOLTAGE ON 4 KV BUSES POINT BEACH NUCLEAR PLANTS. UNITS 1 AND 2 In accordance with the requirements of 10 CFR 50.4 and 50.90, Wisconsin Electric Power Company (WE) (Licensee) hereby requests amendments to Facility Operating Licenses DPR-24 and DPR-27 for Point Beach Nuclear Plant, Units 1 and 2 respectively, to incorporate changes to the plant Technical Specifications. The proposed revisions will modify Technical Specifications to provide a specific numerical setting for reactor trip, reactor coolant pump trip, and Auxiliary Feedwater (AFW) initiation on a loss of power to the 4 KV buses.

Existing Technical Specifications which define the setting limit for these Reactor Protection and Engineered Safety Feature functions are not specific. That is, the Technical Specifications define the limit based on an unspecified " normal" voltage vice a specific numerical setting. This leads to potential concerns as the normal 4 KV bus voltage may vary dependent on system load and configurations including offsite grid voltages. Therefore, this change proposes a specific voltage setting limh for these functions to eliminate a potential source of confusion.

Bases changes for the affected sections are being .made consistent with the proposed Technical Specifications and to eliminate inconsistencies as a result of previous amendments.

It has been determined that the proposed amendments do not involve a significant hazards consideration, authorize a significant change in the types or total amounts of any effluent release, or result in any significant increase in individual or cumulative occupational exposure.

Therefore, the proposed amendments meet the requirements of 10 CFR 51.22(c)(9) and an f environmental impact statement or negative declaration and environmental impact appraisal need t not be prepared.

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NPL 98-0431

May 28,1998

. Page 2.

The description of changes safety evaluation, no significant hazards consideration, and edited (Technical Specifications are provided as attachments to this letter. In addition, the uncertainty -

analysis which demonstrates the acceptability of the proposed Technical Specification setting liniit in preserving the applicable event analysis assumptions is also attached.

Please feel free to contact us if you have any questions.

Sincerely,

[5{fitnCb Vito Kaminskas Manager,

. Regulatory Services & Licensing

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' Attachments cc: NRC Regional' Administrator -

NRC Resident Inspector Public Service Commission of Wisconsin ,

Subscribed'and sworn before me on-lthis2 T' day of (Victv 1998, bu%d )

ogPybli St{e,o[ Wisconsin -

My commission expires 9 20.9g, s

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l- NPL 98-0431 l _ Attachment 1 -

j Page1 DESCRIPTION AND BASIS FOR CHANGES TECHNICAL SPECIFICATION CHANGE REOUEST 203 UNDERVOLTAGE ON 4 KV BUSES' POINT BEACH NUCLEAR PLANTS. UNITS 1 'AND 2

- Introduction .

Wisconsin Electric Power Company (Licensee) has applied for an amendment to Facility Operating Licenses DPR-24 and DPR-27 for Point Beach Nuclear Plant, Units 1 and 2. This

~ amendment proposes to revise the Technical Specifications to incorporate the appropriate specific setting limit for the Auxiliary Feedwater Initiation and Reactor Trip on 4KV bus

' undervoltage. The reactor coolant pump breaker trip setpoint is also revised. The presently defined ' setting limit for these functions, "2 75% of Normal Voltage," may lead to confusion as

" Normal" is not presently dermed and could change due to changing system operating conditions including offsite grid voltages.

Unde voltage Reactor Trip Protection Function A primary function of the 4 KV undervoltage relay is to initiate a signal to the Reactor Protection System to trip the reactor upon a loss of the RCP supply voltage and subsequent loss of coolant flow. The following change is proposed to Specification 15.2.3," Limiting Safety System Settings, Protective Instrumentation," to provide a specific limit.

(6) Undervoltage - 2 75 p:::ent of ec: :! vcha;;: 3120 volts Basis for chance:

The existing limit is non-specific and is subject to interpretation. Normal bus voltage on the

'4160 V buses may vary dependent on system operating conditions and offsite grid voltages, and is normally maintained at a voltage greater than the nominal 4 KV rating. The voltage setpoint and associated time delay for the 4 KV undervoltage relays is based on assumptions in the complete loss of flow safety analysis and operational esncerns. This specific setting eliminates potential' confusion.

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NPL 98-0431 Attachment 1 Page 2 -

Reactor Coolant Pump Motor Breaker -

A loss of power to the 4 KV buses supplying the reactor coolant pumps also trips the reactor coolant pump supply breaker. Loss of a single reactor coolant pump when operating at greater than 50% reactor power initiates a trip. The following change is proposed to Specification 15.2.3 to provide a specific limit:

-(8) Reactor coolant pump motor breaker open (a) Low frequency setpoint 2 55.0 HZ (b) Low voltage setpoint 2 75 pe=ent nc==! vc!: ;;e 3120 volts Basis for chance:

The undervoltage protection function trips the reactor coolant pump supply breaker and trips the reactor. A reactor trip occurs when reactor power is > 50% power upon the loss of a single reactor coolant pump. This ensures that the power to flow ratio is quickly reduced to less than 1 which insures the minimum DNB ratio increases at low flow because the maximum enthalpy rise does not increase above the maximum enthalpy rise which occurs during full power operation and full flow conditions.

Auxiliary Feedwater Initiation Loss of power to the 4 KV buses will also result in a loss of Main Feedwater flow to the steam generators due to the loss of power to the Main Feedwater pumps and result in a reactor trip.

Initiation of AFW flow upon loss of main feedwater flow ensures cooling is supplied to the steam generators for the removal of decay heat from the reactor. The following change is proposed to Specification Table 15.3.5-1, " Engineered Safety Features Initiation Instrument Setting Limits," Item 8 to provide a specific setting limit:

NO. FUNCTIONAL UNIT CHANNEL SETTING LIMIT 8 Undervoltage on 4 KV Buses Auxiliary Feedwater 2-7Fi cf ac==! 3120 volts Initiauon vehage

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. NPL 98-0431

-' Attachment 11 Page 3

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' Basis for channei

A loss of power to the 4KV buses ' supplying the main feed pumps will result in a loss of main feedwater. Initiation of AFW flow in this event, ensures that the steam generators can be.used to remove sensible and decay heat from the reactor core, thus ensuring a safe shutdown condition is -

maintained.- This specific setting limit ensures the required functions are performed.

Bases Changes l One Bases change is included with this request for amendments. The bases change is made to properly reflect reactor operating restrictions with less than two reactor coolant pumps operating.

This change is made to reflect changes to Technical Specification 15.3.1.A.1 approved by .

Amendments 178 and 182 for Point Beach Nuclear Plant Units I and 2, respectively. These -

amendments were approved on September 3,1997. As this basis change reflects previously approved amendments, no further evaluation is required.

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NPL 98-0431 JAttachment 2' ,

Page1-SAFETY EVALUATIONS TECHNICAL SPECIFICATION CHANGE REOUEST 203 UNDERVOLTAGE ON 4 KV BUSES

. POINT BEACH NUCLEAR PLANTS. UNITS 1. AND 2 Introduction Wisconsin Electric Power Company (Licensee) has applied for an amendment to Facility Operating Licenses DPR-24 and DPR-27 for Point Beach Nuclear Plant, Units 1 and 2. .This amendment proposes to revise the Technical Specifications to incorporate the appropriate specific setting limit for the Auxiliary Feedwater Initiation and Reactor Trip on 4KV bus

. undervoltage or Reactor Coolant Pump Trip. The presently defined setting limit , "2 75% of Normal Voltage" for these functions may lead to confusion as " Normal" is not presently defined and could change due to changing system operating conditions including offsite grid voltages.

Normal system operating voltages generally exceed the nominal 4 KV rating.

.. Undervoltage trips and actuations, in general, provide protection for events that may be initiated by a loss of AC power to the plant or particular buses. These events, as detailed in Chapter 14, Safety Analyses, of the PBNP Final Safety Analysis Report (FSAR) include:

FSAR Section 14.1.8, Loss of Reactor Coolant Flow FSAR Section 14.1.10, Loss of Normal Feedwater FSAR Section 14.1.11, Loss of All AC Power to the Auxiliaries Undervoltage 4 KV Buses Reactor Trip The primary function of the 4 KV undervoltage relays is to initiate a signal to the Reactor -

Protection System to trip the reactor on the loss of the RCP supply voltage from buses A01 and l A02 which results in a loss of reactor coolant flow. Loss of power to both reactor coolant pumps j sensed by coincident 1 out of 2 undervoltage circuits will result in a reactor trip when operating j r at greater than approximately 10% power. Loss of power to one reactor coolant pump when operating at greater than 50% power will result in a reactor trip.

For the loss of reactor coolant flow' analyses, reactor trip on a low flow signal is assumed to occur for a loss' of a single reactor coolant pump when greater than 50% power and for loss of

flow due an underfrequency on the supply buses. For a loss of flow event, the worst case is a loss of flow due to underfrequency.

NPL 98-0431-Attachment 2'

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LThe voltage setpoint and associated time delay for the 4 KV undervoltage relays is based on l . assumptions in the complete loss of flow safety analysis and operational concerns. Calculations were completed to quantify the actual numerical value for the setting limit of the protection i function that will be used in place "2 75% of normal voltage" as is currently used in the Technical Specifications. The calculations conservatively take into account voltage decay on the

. buses and instrument uncertainties.

The undervoltage protection provides reactor core protection against DNB as a result of a loss of voltage to both RCPs. Time delays are incorporated in the undervoltage trip to prevent spurious reactor trips from momentary electrical power transients. For undervoltage, the delay is set so that the time required for a signal to reach the reactor trip breakers resulting in rod drop will not exceed 1.5 seconds as provided in FSAR Table 14-3," Trip Points And Time Delays To Trip Assumed In Accident Analyses." Calculations are provided which demonstrate that the proposed Technical Sp.cification setting limit of 2 3120 Volts preserves the analysis assumptions.

Undervoltage Reactor Coolant Pump Trip Undervoltage is sensed down stream of the Reactor Coolant Pump Breakers. Tripping of a single reactor coolant pump will result in a reactor trip when operating at greater than 50% power.

Tripping of the reactor coolant pump breaker occurs following the sensing of undervoltage on 2 out of 2 relays for the respective bus. This ensures that power is rapidly reda::ed such that the power to flow ratio remains less than unity, ensuring DNB margin is acceptable.

Auxiliary Feedwater Initiation Undervoltage on the buses (A01 & A02) sensed by coincident 1 of 2 relays for the A01 and A02

buses supplying the Main Feedwater pumps will result in the tripping of the Main Feedwater Pumps and the starting and initiation of flow to the Steam Generators from the associated turbine-driven Auxiliary Feedwater (AFW) pump. For the Loss of Normal Feedwater and Loss of AC Power to the Station Auxiliaries events, auxiliary Feedwater initiation also occurs upon sensing lo -lo steam generator level Evaluation The proposed change provides a more precise setting limit for the 4 KV undervoltage functions for reactor trip, reactor coolant pump. trip and auxiliary feedwater initiation. ' Although the use of the word " Normal"in the current specification had provided adequate guidance in establishing L the setting limit for this protection function, the possibility for confusion was created by not providing an actual numerical value. The proposed numerical value to be used within the 4 KV C

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. NPL 98-0431:

' ' Attachment 2

- Page 3' undervoltage setting limit, as determined and verified by recent calculations, will provide the necessary trip protection for an undervoltage condition on the 4 KV buses. Therefore, the change to the 4 KV undervoltage setting limit will establish the appropriate Technical Specifications jJ reference for this protection function and in doing so eliminate the potential for plant staff confusion in this area. ,

I' The time sequence or delay for each of the elements as discussed above was taken into consideration when determining the actual 4 KV Buses undervoltage protection function setting -

limit of 3120 V. To ensure the proper value was selected, a calculation was performed which

-' examined the amount to time that would elapse for each segment of an undervoltage related incident. Based on this elapsed time, an undervoltage protection setting limit was established.

Consequently, the justification for changing "75% of Normal" as written in the current Technical l- ' Specification to the numerical value of 3120 volts is based on a calculation examining the total time from the onset of an undervoltage incident to when the reactor control rods are actually

~ dropped. This included the emf decay time to the undervoltage trip set point, the time for the reactor trip logic, the trip breaker cycle delay and the control rod release time.

The proposed setting limits insure that a Reactor Trip occurs as analyzed for loss of reactor coolant flow events and that AFW flow is initiated to remove decay heat following a loss of power to the main feedwater pumps.

Conclusion The proposed change provides the appropriate setting limit for the Point Beach Nuclear Plant Technical Specifications for the 4 KV undervoltage protection function. Therefore, continued safe operation of PBNP is assured by this proposed Technical Specification change.

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NPL 98-0431 Attachment 3 L Page 1

NO SIGNIFIC^NT HAZARDS C( * 'JERATION
TECHNICAL SPECIFICATION Ct - .NGE REOUEST 203
UNDERVOLTAGE ON 4 KV BUSES POINT BEACH NUCLEAR PLANTS. UNITS 1 AND 2 In accordance with the requirements'of 10 CFR 50.91(a), Wisconsin Electric Power Company (Licensee) has evaluated the proposed changes against the standards of 10 CFR 50.92 and has

~ determined that the operation of Point Beach Nuclear Plant, Units 1 and 2 in accordance with the i proposed amendments does not present a significant hazards consideration. The analysis of the requirements of 10 CFR 50.92 and the basis for this conclusicn:

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t. Operation of the Point Beach Nuclear Plant in accordance with the proposed amendments will not create a significant increase in the probability or consequences of an accident previously evaluated.'

The probabilities of accidents previously evaluated are based on the probability ofinitiating events for these accidents. Initiating events for accidents potentially affected by the proposed amendments previously evaluated for Point Beach include losses of reactor coolant flow, loss of extemal electrical load, loss of normal feedwater, and loss of all AC power to the auxiliaries.

This license amendment request proposes to clarify the setting limit for the undervoltage reactor trip, auxiliary fedwater initiation and reactor coolant pump trip by providing an actual numerical value in place of the word " Normal" thereby eliminating any confusion as to

, the actual value used in the setting limit for this protection function.

This proposed change does not cause an increase in the probabilities of any accidents previously evaluated because the change will not cause an increase in the probability of any initiating events for accidents previously evaluated. In parti _cular, the proposed change more clearly defines the actual setting limit for the 4 KV undervoltage protection function taking into account the effects of voltage decay and response times. This is a protection function for mitigation of these events. Appropriate delay times are implemented in this function to -

ensure momentary voltage transients do not initiate these events while ensuring appropriate protection for these loss of power events. Therefore, there is no significant increase in the

. probability or consequences of any event previously analyzed.

I The consequences of the accidents previously evaluated in the PBNP FSAR are determined by the results of analyses that are based on initial conditions of the plant, the type of accident, 1 transient response of the plant, and the operation and failure of equipment and systems. The

changes proposed in this license amendment request provide appropriate limiting conditions for the' setting limits for the Point Beach Nuclear Plant Technical Specifications for the 4 KV

l NPL 98-0431 Attachment 3 Page 2 undervoltage protection function. Thus the analyses of the events remain valid and demonstrate that there are no radiological consequences from these events.

Therefore, this proposed license amendment does not affect the consequences of any accident previously evaluated in the Point Beach Nuclear Plant FSAR, because the factors that are used to determine the consequences of accidents are not being changed.

2. Operation of the Point Beach Nuclear Plant in accordance with the proposed amendments will not create the possibility of a new or different kind of accident from any accident previously evaluated.

New or different kinds of accidents can only be created by new or different accident initiators or sequences. New and different types of accidents (different from those that were originally analyzed for Point Beach) have been evaluated and incorporated into the licensing basis for Point Beach Nuclear Plant. Examples of different accidents that have been incorporated into the Point Beach Licensing basis include anticipated transients without scram and station blackout.

The change proposed by the amendments to provide specific undervoltage setting limits does not create any new or different accident initiators or sequences because the change to the 4 KV undervoltage protection function will not cause failures of equipment or accident  ;

sequences different than the accidents previously evaluated. Therefore, the proposed {

Technical Specification change does not create the possibility of an accident of a different type than any previously evaluated in the Point Beach FSAR.

3. Operation of the Point Beach Nuclear Plant in accordance with the proposed amendments not create a significant reduction in a margin of safety.

The margins of safety for Point Beach are based on the design and operation of the reactor and containment and the safety systems that provide their protection.

The change proposed by this license amendment request provides the appropriate settmg )

limit for the 4 KV undervoltage protection function. This ensures that the safety systems that protect the reactor and containment will operate as required. The design and operation of the ,

reactor and containment are not affected by these proposed changes. Therefore, the margins  !

of safety for Point Beach are not being reduced because the design and operation of the I reactor and containment are not being changed.

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