ML20155B968
| ML20155B968 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 10/23/1998 |
| From: | DUQUESNE LIGHT CO. |
| To: | |
| Shared Package | |
| ML20155B965 | List: |
| References | |
| NUDOCS 9811020022 | |
| Download: ML20155B968 (9) | |
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ATI'ACHMENT A-260 e
4 Unit No.1 Technical Specification Bases Panes 1
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9811020022 981023 PDR ADOCK 05000334; P PDR t
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ATTACHMENT TO LICENSE AMENDMENT NO.
FACILITY OPERATING LICENSE NO. DPR-66 DOCKET NO. 50-334 Replace the following pages of Appendix A, Technical Specification Bases, with the enclosed page as indicated. The revised page contain vertical lines indicating the areas of change.
Remove Insert B 2-3 B 2-3
DPR-66 2.2 LIMITING SAFETY SYSTEM SETTINGS I
BASES l
2.2.1 REACTOR TRIP SET POINTS The Reactor Trip Setpoint Limits specified in Table 2.2-1 are the values at which the Reactor Trips are set for each parameter. The Trip Values have been selected to ensure that the reactor core and reactor coolant system are prevented from exceeding their safety
! limits. Operation with a Trip Setpoint less conservative than its Setpoint Limit but within its specified Allowable Value is acceptable on the basis that each Allowabl a value is equal to or less than the
- drift allowance assumed to occur for each trip used in the accident l analyses. j I
I For the Overtemperature AT, and Overpower AT trips, Table 2.2-1 specifies several time constants (I's) in terms of equalities, such as t=x seconds. These time constants represent nominal values and are periodically adjusted to within their specified calibration accuracy. With the time constants within the specified accuracy the
, accident analysis produces acceptable results.
l Manual Reactor Trio l The Manual Reactor Trip is a redundant channel to the automatic l protective instrumentation channels arm provides manual reactor trip j capability.
Power Rance. Neutron Flux l The Power Range, Neutron Flux channel high setpoint provides reactor l
l core protection against reactivity excursions which are too rapid to be protected by temperature and pressure protective circuitry. The l low set point provides redundant protection in the power range for a l l power excursion beginning from low power. The trip associated with i the low setpoint may be manually bypassed when P-10 is active (two of l the four power range channels indicate a power level of above l approximately 9 per cent of RATED THERMAL POWER) and is automatically l
reinstated when P-10 becomes inactive (three of the four channels indicate a power level below approximately 9 percent of RATED THERMAL POWER).
Power Rance. Neutron Flux. Hiah Rates
! The Power Range Positive Rate trip provides protection against rapid
! flux increases which are characteristic of rod ejection events from l any power level. Specifically, this trip complements the Power Range l Neutron Flux High and Low trips to ensure that the criteria are met
- for rod ejection from partial power.
BEAVER VALLEY - UNIT 1 B 2-3 Amendment No.
1 ATTACHMENT A-133 Unit No. 2 Technical Snecification Bases Paees l
1 ATTACHMENT 'r' LI. CENSE AMENDMENT NO.
FACILITY OP h m s LICENSE NO. NPF-73 DOCKET NO. 50-412 Replace the following pages of Appendix A, Technical Specification Bases, with the enclosed pages as indicated. The revised pages contain vertical lines indicating the areas of change.
Remove Insert B 2-3 B 2-3 B 2-4 B 2-4 B 2-5 B 2-5 B 2-6 B 2-6 B 2-7 B 2-7 B 2-8 B 2-8 l
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NPF-73 LIMITING SAFETY SYSTEM SETTINGS BASES 2.2.1 REACTOR TRIP SYSTEM INSTRUMENTATION SETPOINTS. continued acceptable since an allowance has been made in the safety analysis to accommodate this error. An optional provision has been included for determining the OPERABILITY of a channel when its trip setpoint is found to exceed the Allowable Value. The methodology of 1h'.s option utilizes the "as measured" deviation from the specified calibration point for rack and sensor components in conjunction with a statistical combination of the other uncertainties in calibrating the instrumentation. In Equation 2.2-1, Z + R + S $ TA, the interactive effects of the errors in the rack and the sensor, and the "as measured" values of the errors are considered. Z, as specified in Table 2.2-1, in percent span, is the statistical summation of errors assumed in the analysis excluding those associated with the sensor and rack drift and the accuracy of their nearurement. TA or Total Allowance is the difference, in percent span, between the trip setpoint and the value used in the analysis for reactor trip. R or Rack Error is the "as measured" deviation, in percent span, for the affected channel from the specified trip setpoint. S cr Sensor Drift is either the "as measured" deviation of the sensor from its calibration point or the value specified in Table 2.2-1, in percent span, from the analysis assumptions. Use of Equation 2.2-1 allows i for a sensor drift factor, an increased rack drift factor, and provides a threshold value for REPORTABLE EVENTS.
The methodology to derive the trip setpoints is based upon combining all of the uncertainties in the channels. Inherent to the determination of the trip setpoints are the magnitudes of these channel uncertainties. Sensors and other instrumentation utilized in these channels are expected to be capable of operating within the allowances of these uncertainty magnitudes. Rack drift in excess of the Allowable Value exhibits the behavior that the rack has not met its allowance. Being that there is a small statistical chance that this will happen, an infrequent excessive drift is expected. Rack or sensor drift, in excess of the allowance that is more than occasional, may be indicative of more serious problems and should warrant further investigation.
For the overtemperature AT, Overpower AT, and Low Pressurizer Pressure trips, Table 2.2-1 specifies several time constants (t's) in terms of equalities, such as t=x seconds. These time constants represent nominal values and are periodically adjusted to within their specified calibration accuracy. With the time constants within the specified accuracy the accident analysis produces acceptable results. For time lags in the Tavg and Delta T circuits, these values are set as close to "zero" as practical to provide minimum filter action.
BEAVER VALLEY - UNIT 2 B 2-3 Amendment No.
NPF-73 LIMITING SAFETY SYSTEM SETTINGS
. BASES Manual Reactor Trio The Manual Reactor Trip is a redundant channel to the automatic protective instrumentation channels and provides manual reactor trip capability.
Power Ranae. Neutron Flux The Power Range, Neutron Flux channel high setpoint provides reactor core protection against reactivity excursions which are too rapid to be protected by temperature and pressure protective circuitry. The low setpoint provides redundant protection in the power range.for a power excursion beginning from low power. The trip ansociated with the low setpoint may be manually bypassed when P-10 is active (two of the four power range channels indicate a power level of above approximately 10 percent of RATED THERMAL POWER) and is automatically reinstated when P-10 becomes inactive (three of the four channels '
indicate a power level below approximately 10 percent of RATED THERMAL POWER).
Power Rance. Neutron Flux. Hiah Rates The Power Range Positive Rate trip provides protection against rapid flux increases which are characteristic of rod ejection events from any power level. Specifically, this trip complements the Pcwer Range Neutron Flux High and Low trips to ensure that the criteria are met for rod ejection from partial power.
The Power Range Negative Rate trip provides protection to ensure that the minimum DNBR is maintained above the design DNBR limit for control rod drop accidents. At high power a multiple rod drop accident could cause local flux peaking which, when in conjunction with nuclear power being maintained equivalent to turbine power by
! action of the automatic rod control system, could cause an unconservative local DNBR to exist. The Power Range Negative Rate trip will prevent this from occurring by tripping the reacto?!. No
- credit is taken for operation of the Power Range Negative RY:e trip for those control rod drop accidents for which DNBRs will be greater than the design DNBR limit.
Intermediate and Source Rance. Nuclear Flux The Intermediate and Source Range, Nuclear Flux trips provide reactor core protection during reactor startup to mitigate the consequencen of an uncontrolled rod cluster control assembly bank withdrawal from a subcritical condition. These trips provide redundant protection to i the low setpoint trip of the Power Range, Neutron Flux channels. The l
BEAVER VALLEY - UNIT 2 B 2-4 Amendment No.
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NPF-73 l LIMITING SAFETY SYSTEM SETTINGS ;
a BASES 1
Source Range Channels will initiate a reactor trip at about 100 l counts per second unless manually blocked when P-6 becomes active.
The intermediate range channels will initiate a reactor trip at a j current level proportional to approximately 25 percent of RATED THERMAL POWER unless manually blocked when P-10 becomes active.
Although no explicit credit was taken for operation of the Source Range Channels in the accident analyses, operability requirements in the Technical Specifications will ensure that the Source Range Channels are available to mitigate the consequences of an inadvertent control bank withdrawal in MODES 3, 4 and 5.
Overtemperature AT I j The Overtemperature AT trip provides core protection to prevent DNB 4
for all combinations of pressure, power, coolant temperature, and axial power distribution, provided that the transient is slow with !
respect to piping transit, thermowell, and RTD response time delays from the core to the temperature detectors (about 4 seconds), and pressure is within the range between the High and Low pressure
? reactor trips. This setpoint includes corrections for changes in j density and heat capacity of water with temperature and dynamic i compensation for transport, thermowell, and RTD response time delays i from the core to RTD output indication. With normal axial power distribution, this reactor trip limit is always below the core safety limit as shown on Figure 2.1-1. If axial peaks are greater than
- design, as indicated by the difference between top and bottom power i range nuclear detectors, the reactor trip is automatically reduced i according to the notation in Table 2.2-1.
1 overoower AT The overpower AT reactor trip provides assurance of fuel integrity, e.g., no me'. ting, under all possible overpower conditions, limits the
! required range for overtemperature AT protection, and provides a t- backup- to the High Neutron Flux Trip. The setpoint includes corrections for changes in density and heat capacity of water with l temperature, and dynamic compensation for transport, thermowell, and RTD response time delays from the core to RTD output indication. The overpower AT trip provides protection to mitigate the consequences 4
of various size steam line breaks as reported in WCAP-9226, " Reactor
{ Core Response to Excessive Secondary Steam Release."
i BEAVER VALLEY - UNIT 2 B 2-5 Amendment No.
NPF-73 LIMITING SAFETY SYSTEM SETTINGS BASES Pressurizer Pressure The Pressurizer High and Low Pressure trips are provided to limit the pressure range in which reactor operation is permitted. The High Pressure trip is backed up by the pressurizer code safety valves for RCS overpressure protection, and is therefore set lower than the set pressure for these valves (2485 psig). The Low Pressure trip protects against low pressure which could lead to DNB by tripping the reactor in the event of a loss of reactor coolant pressure.
On decreasing power the Low Pressure trip is automatically blocked by P-7 (a power level of approximately 10% of RATED THERMAL POWER or turbine impulse chamber pressure at approximately 10% of full power equivalent); and on increasing power, automatically reinstated by P-7.
Pressurizer Water Level The Pressurizer High Water Level trip ensures protection against 3 Reactor Coolant System overpressurization by limiting the water level to a volume sufficient to retain a steam bubble and prevent water relief through the pressurizer safety valves. On decreasing power, the pressurizer high water level trip is automatically blocked by P-7 (a power level of approximately 10 percent of RATED THERMAL POWER or a turbine impulse chamber pressure at approximately 10 percent of full power equivalent); and on increasing power, automatically reinstated by P-7. No credit was taken for operation of this trip in the accident analyses; horover, its functional capability at the specified trip setting is required by this specification to enhance the overall reliability of the Reactor Protection System. I Loss of Flow The Loss of Flow trips provide core protection to prevent DNB in the event of a loss of one or more reactor coolant pumps. I 1
Above 10 percent of RATED THERMAL POWER, an automatic reactor trip will occur if the flow in any two loops drop below 90 percer.t of nominal full loop flow. Above 30 percent (P-8) of RATED THERMAL POWER, automatic reactor trip will occur if the flow in any single loop drops below 90 percent of nominal full loop flow.
Steam Generator Water Level The Steam Generator Water Level Low-Low trip provides core protection l by preventing operation with the steam generator water level below I the minimum volume required for adequate heat removal capacity. The ;
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BEAVER VALLEY - UNIT 2 B 2-6 Amendment No.
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1 NPF-73 LIMITING SAFETY SYSTEM SETTINGS J BASES specified setpoint provides allowance that here will be sufficient water inventory in the steam generators at the time of trip to allow for starting delays of the auxiliary feedwater system.
Undervoltaae and Underfreauency - Reactor Coolant Pumn Busses The Undervoltage and Underfrequency Reactor Coolant Pump bus trips provide reactor core protection against DNB as a result of loss of voltage or underfrequency to more than one reactor coolant pump. The specified setpoints 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 I reactor trips from momentary electrical power transients. For I undervoltage, the delay is set so that the time required for a signal to reach the reactor trip breakers following the simultaneous trip of two or more reactor coolant pump bus circuit breakers shall not exceed 1.2 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 shall not exceed 0.6 seconds.
On decreasing power, the Undervoltage and Underfrequency Reactor Coolant Pump bus trips are automatically blocked by P-7 (a power level of approximately 10 percent of RATED THERMAL POWER with a i turbine impulse chamber pressure at approximately 10 percent of full power equivalent); and on increasing power, reinstated automatically by P-7.
Turbine Trio A Turbine Trip causes a direct reactor trip when operating above P-9.
Each of the turbine trips provide turbine protection and reduce the severity of the ensuing transient. No credit was taken in the accident analyses for operation of these trips. Their functional capability at the specified trip settings is required to enhance the overall reliability of the Reactor Protection System.
Safety Iniection Inout from ESF If a reactor trip has not already been generated by the reactor protective instrumentation, the ESF automatic actuation logic channels will initiate a reactor trip upon any signal which initiates a safety injection. This trip is provided to protect the core in the event of a LOCA. The ESF instrumentation channels which initiate a safety injection signal are shown in TABLE 3.3-3.
BEAVER VALLEY - UNIT 2 B 2-7 Amendment No.
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' l NPF-73 l LIMITING SAFETY SYSTEM SETTINGS BASES Reactor Coolant Pumn Breaker Position Trio The Reactor Coolant Pump Breaker Position Trips are anticipatory trips which provide reactor core protection against DNB resulting from the opening of two or more pump breakers above P-7. These trips are blocked below P-7. The open/close position trips assure a reactor trip signal is generated before the low flow trip setpoint is reached. No credit was taken in the accident analyses for operation of these trips.
Their functional capability at the open/close position settings is required to enhance the overall reliability of the Reactor Protection System.
Reactor Trio System Interlocks !
The Reactor Trip System interlocks perform the following functions: l P-6 Above the setpoint P-6 allows the manual block of the i Source Range reactor trip and de-energizing of the high j voltage to the detectors. Below the setpoint source range level trips are automatically reactivitated and !
high voltage restored.
P-7 Above the setpoint P-7 automatically enables reactor trips on low flow or coolant pump breaker open in more than one primary coolant loop, reactor coolant pump bus )
undervolte.ge and underfrequency, pressurizer low pressure i and prest;urizer high level. Below the setpoint the above !
listed trips are automatically blocked. l P-8 Above the setpoint P-8 automatically enables reactor trip on low flow in one or more primary coolant loops. Below the setpoint P-8 automatically blocks the above listed trip.
P-9 Above the setpoint P-9 automatically enables a reactor trip on turbine trip. Below the setpoint P-9 automatically blocks a reactor trip on turbine trip.
P-10 Above the setpoint P-10 allows the manual block of the Intermediate Range reactor trip and the low setpoint !
Power Range reactor trip; and automatically blocks the Source Range reactor trip and de-energizes the Source l Range high voltage power. Below the setpoint the Intermediate Range reactor trip is automatically reactivated. Provides input to P-7.
P-13 Provides input to P-7.
BEAVER VALLEY - UNIT 2 B 2-8 Amendment No.
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