ML20043H549

Proposed Tech Specs Re Reactor Trip Sys Interlocks

ML20043H549
Person / Time
Site:	Mcguire, McGuire
Issue date:	06/14/1990
From:	DUKE POWER CO.
To:
Shared Package
ML20043H545	List: ML20043H544 ML20043H549
References
NUDOCS 9006260095
Download: ML20043H549 (5)

Text

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Attachment Duke Power Company McGuire Nuclear Station Technical Specification Bases With Changes Identified and Additional.Information (FSAR and Bases Pages) l =:

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LIMITING SAFETY SYSTEM SETTINGS <

BASES' li ,

Reactor Trip' System Interlocks-

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The Reactor Trip System _ Interlocks- perform the following functions l:

P On increasing power P-6 allows .

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-3 On .decreasir reactivated and highg power,~ Source Range Level . trips are automa voltage restored s 1 i P-7 .

On increasing power P-7 automatically enable .

undervoltage and underfrequency, 50i... t ;r, pressurizer low pressure and pressurizer high level.

-l listed trips are automatically blocked.~On decreasing power the above

P-8 g g g g 7Gg f ,

On increasing power P-8 automatically enab p .

flow ir, one or more reactor coolant loops # s Reactor trips on. low P-8 automatically blocks the above listed trips.On decreasing power.[the P .10 On increasing power.. P-10 allows the manual block aeof the Inter 1

.theRange Reactor trip-and the Flow Setpoint Po Source Range high voltage power.

mediate Range Reactor'tiip trip are automatically reactivated.and the Low Setpoint Power Range Re Provides input- to P-7. '

P-13 Provides input to P-7.

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' LIMITING SAFETY SYSTEM SETTINGS i >-

BASES' b; .

Steam Generator Water Level T

The Steam Generator Water-Level low-Low trip protects the reactor from

[ , loss of teat ' sink in the event of a sustained steam /feedwater flow mismatch L resulting from loss of. normal feedwater. The specified Setpoint provides allowances'for starting delays of the Auxiliary Feedwater System.'

- 'Undervoltage and Underfrequency - Reactor Coolant Pump Busses i 'The Undervoltage and Underfrequency Reactor Coolant Pump Bus trips

. provide core protection against DNB as a result of complete loss of forced e coolant flow. The specified SetpoirJs assure a Reactor trip signal is

-generated before the Low Flow Trip Setpoint is reached. Time delays are incorporated in the Underfrequency and Undervoltage trips to prevent spurious L_ Reictor trips from momentary electrical power transients. For undervoltage, 5! the delay is set so that the time required for a signal to reach the Reactor E trip breakers following the simultaneous trip of two or more reactor coolant pump bus circuit breakers shall not exceed 1.5 seconds. For underfrequency, the delay is set so that the time required for.a signal to reach the Reactor trip breakers after the Underfrequency Trip Setpoint is-reached s. hall not exceed 0.6 second. On decreasing power the Undervoltage and Underfrequency

'; Reactor Coolant Pump Bus trips are automatically blocked by P-7 (a power level of approximately 10% of RATED THERMAL POWER with a turbine impulse chamber

(_ -pressure at approximately 10% of full power equivalent); and on increasing' gg power, reinstated automatically by P-7.

Turbine Trip gg A Turbine trip initiates a Reactor trip. On decreasing power the Turbine trip is automatically blocked by P-8 (a power level of approximately 48% of

_EP RATED THERMAL POWER with a turbine impulse chamber at approximately 48% of P full power' equivalent); and on increasing power, reinstated automatically;by

P-8.

Safety Injection Input from ESF If a Reactor trip has not already been generated by the Reactor Trip System Instrumentation, the ESF automatic actuation logic channels will initiate a Reactor trip upon any signal which initiates a Safety Injecti n.

The ESF Instrumentation channels which initiate a Safety Injection signa; are

-shown in Table 3.3-3.

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This' trip' protects _ the reactor from loss- of heat sink in the eve t of a sustained steam /feedwater flow mismatch. This trip is actuated on two-out-of-four low-low water level signals occurring in any steam generator.

The logic is shown on Figure 7.2.1-1,_ Sheet 7. A detailed functional description of the process equipment associated with this trip is pro-vided in-Reference 1.

.f. Safety Injection Signal Actuation Trip-

Areactor_trkpoccurswhentheSafetyInjectionSystemisactuated.

The means of actuating the Safety Injection. System are described in Section 7.3. - This trip protects the core against a loss of reactor coolant or steam.

Figure 7.2.1-1, Sheet 8, shows the logic for this trip. A' detailed functiona_1 description of the process equipment associated with this trip function is provided in Reference 1.

g. Manual Trip The manual trip con; ;ts of two switches with one. output onLeach switch.

One switch is _used to actuate the train A trip breaker; the other switch-actuates the train B trip breaker. Operating either manual trip switch removes the voltage from the under voltage trip coil, energizes-the shunt trip coil, .and. trips the reactor.

There'are no interlocks which can block this trip. Figure 7.2.1-1, Sheet 3, shows the manual trip logic,

b. Turbine Trips A direct. reactor trip on turbine trip provides additional-protection against PORV challenges. initiated by a narrow range of events, thet.is, turbine trips not initiated by a reactor trip or a safety injection and occurring at or near full power.

The reactor trip on turbine trip will be generated by either of the following signals, provided reactor power is greater than the P-8 setpoint:

1)' Four-out-of-four turbine stop valves closed.

2) Two-out-of-three turbine auto-stop oil pressure low, wnich indicates loss of turbine control oil.

The trip logic is shown on Figure 7.2.1-1, Sheet 16.

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'7.2.1.1.3- Reactor Protection' System I'nterlocks gM

a. Power. Escalation Permissives - ,.

The. overpower protection provided by the'out-of-core nuclear instrumenta-tion consists of three discrete, but overlapping, ranges. Continuation of

[6 startup operation or power increase requires a permissive signal from the higher range instrumentation channels before the lower range level trips can be. manually blocked by.the operator.

A one-of-two intermediate-range permissive signal (P-6) is required prior to source rsnge level trip blocking. A source-range manual block is pro-vided for each logic train and the blocks must be.in_effect on both trains in' order to proceed in the intermediate range. Source range level trips

" are automatically reactivated and high voltage restored when both inter-mediate range channels are below the permissive (P-6) level. There is a j manual reset switch for administratively reactivating the source range level trip and detector high voltage when between the permissive P-6 and -

q P-10' level, if required. Source range level trip block and high voltage '

cutoff are always maintained when power is above the permissive P-10: level in order to prevent detector damage. i The intermediate-range level trip and power-range (low setpoint) trip can only be blocked af ter satisfactory operation and permissive information i' are obtained from two of-four power-range channels. Individual blocking - .

switches are provided so that the low setpoint power range trip and

' intermediate-range trip can be independently blocked. These trips are automatically reactivated when any. three of the four power range channels are below the oermissive (P-10) level, thus ensuring automatic activation to more restrictive trip protection.

The development of permissives P-6 and P-10 is shown on Figure 7.2.1-1, ,!

Sheet 4. All of the permissives are digital; they are derived from analog j signals in the nuclear power range and intermediate-range channels'. _

See Table 7.2,1-2 for the list of' protective system interlocks. ]

b. Blocks of Reactor Trips at Low Power Interlock P-7 blocks a reactor trip at low power (below approximately 10 percent of full power) from low reactor coolant- flow, reactor coolant pump i under voltage, reactor coolant pump underfrequency, pressurizer low 1

pressure, or, pressurizer high water level. See Figure 7.2.1-1, Sheets 5, .

6 and 16, for permissive applications. The low power signal is derived f rom three-out-of-four power range neutron flux signals below the setpoint- 1 in coincidence with two-out-of-twa turbine impulso chamber pressure signals below the setpoint (low unit load) i The P-8 erlock blocks a reactor trip from a turbine trip or low reactor cooiant f.aw reactor trip when the unit is below approximately 47 percent f of full power. The block action (absence of the P-8 interlock signal) occurs when three-out-of-four neutron flux power range signals are below l the setpoint. Thus, below the P-8 setpoint, the reactor is allowed to 4 l

operate with one inactive loop and trip does not occur until two loops are f indicating low flow. ~

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