ML20217P835

Proposed Tech Specs Clarifying Discussion of Margin Between RPS High Pressure Trip Setpoint & Lift Setting for Pressurizer Code Safety Valves

ML20217P835
Person / Time
Site:	Davis Besse
Issue date:	04/24/1998
From:	CENTERIOR ENERGY
To:
Shared Package
ML20217P829	List: ML20217P825 ML20217P835
References
NUDOCS 9805070107
Download: ML20217P835 (6)

Text

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Docket Number 50-346

, License Number NPF-3 Serial Number 2504 e1 -

SAFETY LIMITS AND LIMITING SAFETY SYSTEM SETTINGS 2.2 IIMITING SAFETY SYSTEM SETTINGS REACTOR PROTECTION SYSTEM SETPOINTS 2.2.1 The Reactor Protection System instrumentation setpoints shall be set consistent with the Allowable Values shown in Table 2.2-1.

l APPLICABILITY: As shown for each channel in Table 3.3-1.

ACTION:

With a Reactor Protection System instrumentation setpoint less conservative than the value shown in the Allowable Values column of Table 2.2-1, declare the channel inoperable and apply the applicable ACTION statement requirement of Specification 3.3.1.1 until the channel is restored to OPERABLE status with its trip setpoint adjusted consistent with the Allowable Value.

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Docket Number 50-346 Ucense, Number NPF-3 Serial Number 2504 0;;;~""'

2.2 LIMITING SAFETY SYSTEM SETTINGS 11tlS PAEE PROVIDED BASES 1

! 2.2.1 REACTOR PROTECTION SYSTEM INSTRUMENTATION SETPOINTS The reactor protection system instrumentation Allowable Values specified in Table 2.2-1 have been selected to ensure that the reactor core and reactor coolant system are prevented from exceeding their safety limits.

The shutdown bypass provides for bypassing certain functions of the reactor protection system in order to permit control rod drive tests, zero power PHYSICS TESTS and certain startup and shutdown procedures. The purpose of the shutdown bypass high pressure trip is to prevent normal operation with shutdown bypass activated. This high pressure setpoint is lower than the normal low pressure setpoint so that the reactor must be tripped before the bypass is initiated. The high flux setpoint of $5.0% prevents any significant reactor power from being produced. Sufficient natural circulation would be ,

l available pumps to operating.

were remove 5.0% of RATED THERMAL POWER if none of the reactor coolant l Manual Reactor Trio 1

The manual reactor trip is a redundant channel to the automatic reactor I capability.system instrumentation channels and provides manual reactor trip protection 1

Hioh Flux A high flux trip at high power level (neutron flux) provides reactor core protection against reactivity excursions which are too rapid to be protected by temperature and pressure protective circuitry.

l During normal station operation, reactor trip is initiated when the reactor power level reaches the Allowable Value s 105.1% of rated power. Due to transient overshoot, heat balance, and instrument errors, the maximum actual l power at which a trip would be actuated could be 112%, which was used in the safety analysis.

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l DAVIS-BESSE, UNIT 1 8 2-4 Amendment No. 4&r-W218 l

i Docket Number 50-346 License Number NPF-3 i ' Serial Number 2504 Cf"""' .

THIS PAGE PROVIDED LIMITING SAFETY SYSTEM SETTINGS .

BASES

. t , i : ,4 . l RC Hiah Temperature The RC high temperature trip s618'F prevents the reactor outlet temperature from exceeding the design limits and acts as a backup trip for all power excursion transients. {

j Flux -- AFlux/ Flow The power level Allowable Value produced by the reactor coolant system flow is based on a flux-to-flow ratio which has been established to accommodate flow l !

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decreasing transients from high power where protection is not provided by the  !

high flux / number of reactor coolant pumps on trips.

The power level Allowable Value produced by the power-to-flow ratio provides l both high pwer level and low flow protection in the event the reactor power level increases or the reactor coolant flow rate decreases. The power level setpoint produced by the power-to-flow ratio provides overpower DNB protection for all modes of pump operation. For every flow rate there is a maximum permissible power level, and for every power level there is a minimum permissible low flow rate.

For safety calculations the instrumentation errors for the power level were used. Full flow rate is defined as the flow calculated by the heat balance at 100%; power. At the time of the calibration the RCS flow will be greater than or equal to the value in Table 3.2-2. j l

DAVIS-BESSE, UNIT 1 B 2-5 Amendment No. Mr33,45,51,80,123,189, 218

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Ihocket Number 50-346 y . Lic'ense Number NPF-3 -

Serial Number 2504 Attachment {

Page 6 -

LIMITING SAFETY SYSTEM SETTINGS BASES The AXIAL POWER IMBALANCE boundaries are established in order to prevent reactor l thermal limits from being exceeded. These thermal limits are either power peaking kW/ft limits or DNBR limits. The AXIAL POWER IMBALANCE reduces the power level trip produced by a flux-to-flow ratio such that the boundaries of the figure in the CORE OPERATING LIMITS ,

REPORT are produced. 1 j

RC Pressure - Low. High, and Pressure Temperature ~

l i The high and low trips are provided to limit the pressure range in which reactor operation is '

l permitted.

During a slow reactivity insertion startup accident from low power or a slow reactivity insertion from high power, the RC high pressure setpoint is reached before the high flux setpoint. 'Ihe Allowable Value for RC high pressure,2355 psig, has been established to maintain the system pressure below the safety limit,2750 psig, for any design transient. The RC high pressure trip is backed up by the pressurizer code safety valves for RCS over pressure protection. The RC high pressure trip is, therefore, set lower than the set pressure for these valves,21Q9.c 2525 psig (nomina 11 even when accounting for the RPS RC oressure instrument string uncertaintv. The RC high pressure trip also backs uMne high flux trip.

The RC low pressure,1900.0 psig, and RC pressure-temperature (16.00 Tom - 7957.5) psig, Allowable Values have been established to maintain the DNB ratio greater than or equal to the minimum allowable DNB ratio for those design accidents that result in a pressure reduction. It .

also prevents reactor operation at pressures below the valid range of DNB correlation limits, protecting against DNB. l Hich Flux / Number of Reactor Coolant Pumos On In conjunction with the flux - Aflux/ flow trip the high flux / number of reactor coolant pumps on trip prevents the minimum core DNBR from decreasing below the minimum allowible DNB ratio by tripping the reactor due to the loss of reactor coolant pump (s). The pump monitors also restrict the power level for the number of pumps in operation.

DAVIS-BESSE, UNIT I B 2-6 Amendment No. 33,45,60,61,149, 189,218,