ML033350032
| ML033350032 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/26/2003 |
| From: | NRC/NRR/DLPM |
| To: | |
| References | |
| TAC MC1358 | |
| Download: ML033350032 (4) | |
Text
LIMITING SAFETY SYSTEM SETTINGS RACre ff I&Iry 20, 2003
.C.
.0.
Steam Generator Water Level - Low The Steam Generator Water Level-Low Trip provides core protection by preventing operation with the steam generator water-level below the minimum volume required for adequate heat removal capacity and assures that the design pressure of the reactor coolant system will not be exceeded.
Local Power Density-High The Local Power Density-,High trip, functioning from AXIAL SHAPE INDEX monitoring, is provided to ensure that the peak local power density in the fueliwhich corresponds to fuel centerline melting will not occur as a conse-quence of axial powermaldistributions. A reactor trip is initiated whenever the AXIAL SHAPE INDEX exceeds the allowable limits of Figure 2.2-2. The AXIAL SHAPE INDEX is calculated from the upper and lower ex-core neutron detector channels. The calculated setpoints are generated as a function of THERMAL POWER level. The trip is automatically bypassed below 15 percent power as sensed by the power range nuclear instrument Level I bistable.
The maximum AZIMUTHAL POWER TILT and maximum CEA misalignment permitted for continuous operation are assumed in generation of the setpoints. In addition, CEA group sequencing in accordance with the Specifications 3.1.3.5 and 3.1.3.6 is assumed.
Finally, the maximum insertion of CEA banks which can occur during any anticipated operational occurrence prior to a Power Level-High trip is assumed.
Thermal Margin/Low Pressure I
The Thermal Margin/Low Pressure trip when the DNBR is below the 95/95 limit for is provided to prevent the NB correlation.
operation MILLSTONE -
0901 UNIT 2 B 2-6 Amendment Corrected by No. te, da,
,12 2X0 l etter dated 1 1/26/2003.
p
.., TSCR.2-4-02 October 18, 2002 BASES 3/4.7.1.2 AUXILIARY FEEDWATER PUMPS The OPERAB'ILITY of the auxiliary feedwater.pumps ensures that the' Reactor Coolant System can be cooled down to less than 3001 from normal operating conditions in the event of a total loss of off-site power.
The FSAR..Chapter 14 Loss of NormalFeedwater (LONF) analysis.evaluates the event occurring with and without offs ite. power a'ailAble., and,a sigle active 'fail'ure. This.analysis has determined that one motor driven AF. pump is'not sufficient to meet the acceptance criteria. Therefore, two AFW pumps (two.-mo~tor-driven AF: ppumps,.. or..oe' motor-driven. AFW pumpand the steam-driven AFW pump) are required' to meet the acceptance criteria for this moderate frequency event.
To meet the requirement of two AFW pumps available for mitigation., all three. pumps must be. OPERABLE. to accommodate the fai.lre.of one-pump... This i s consistent withthe limiting'conditionfor operation and action:statements of Technical' Specification 3.7..1.2.
conservative fSAR Chapter 0-aBestEstimate Analysis of the LONF event was performed todemonstrate that one' motor-dri:ven A pump isadequate to remove dec'ay heat? prevent steam g'enerator dryout, maintain Reactor Coolant System (RCS) subcooling, and prevent pressurizer level from exceeding acceptable limits.
From, this best estimate analysis of the LONF event,. an evaluati'on.was performed to demonstrate that a, single motor-driven AFW pump has.suffi'.cient capacity to. reduce'the RCS.temperature to,300*F (in. addition to decay heat.removal) where the Shutdown Cooling System may be placed into operation for continued cooldown.
As a result of these evaluations, one motor-driven AFW pump (or the steam-driven AFW pump which has twice the capacity of a motor-driven AFW pump) can meet the requirements to remove decay heat, prevent steam generator dryout, maintain RCS subcooling, prevent the pressurizer from exceeding acceptable limits, and reduce RCS temperature to 300'F.
The' Technical Specification Surveillance Requirements provided to ensure OPERABILITY of each component ensures that at a minimum, the assumptions used in the accident analysis are met and that subsystem OPERABILITY is maintained.
The purpose of the auxiliary feedwater pumps differential pressure tests on recirculation, Surveillance Requirements 4.7.1.2.a.2.a and 4.7.1.2.a.2.b, is to ensure that the pumps have not degraded to a point where the accident analysis would be adversely impacted.
The surveillance requirement acceptance criteria for the motor driven auxiliary feedwater pumps was developed assuming a 5% degraded pump from the actual pump curves.
The surveillance 'requirement acceptance criteria for the turbine driven auxiliary feedwater pump-was developed from high flow test data extrapolated to minimum recirculation flow, and can be adjusted to account for the affect on pump performance' of variations in pump speed.
Flow and pressure measurement instrument inaccuracies have not been accounted for in the design basis hydraulic analysis for the motor driven auxiliary feedwater pumps.
Flow, pressure,-and speed measurement instrument inaccuracies have not been accounted for in the design Wasis hy#draulic analysis for the turbine driven auxiliary feedwater pump.
Corrections for flow, pressure, and speed (turbine driven pump only) measurement instrument inaccuracies will be applied to test data taken when verifying pump MILLSTONE - UNIT 2 B 3/4 7-2 Amendment No. f, #J, 01, gym 0899 Crete s1 Corrected bv letter dated 11/26/2003-
PLANI YSILMS TSCR 2-4-02 October 18., 2002 BASES 3/4.7.1.2 AUXILIARY FEEDWATER PUMPS (Continued) performance. in the flow ranges credited.in the accident analyses No.
.corrections for flDw, pressure, and speed (turbine driven. pump'. only) measurement instrument inaccuracies will be applied to minimum' recirculation flow type test data since this portion of the curve is not credited: inthe accident analyses....Corrections. for flow,,cpressure,. and speed (turbine driven pump only) measurement. instrument in"accuracies are not reflected n
the Technical Specification acceptance criteria.
The Auxiliary feed Water (AFW) system is-OPERABLE when the AFW pumps and flow p aths required 'to provide AFW to the steam enerators reOPERABLE. -
Technical Specification 3.7.1.2 requires three AFW pumps to be OPERABLE and provides ACTIONS to address inoperable AFW pumps.
The AFW flow path requirements are separated into AFW pump suction flow'path requi-rements,:AFW-pump discharge flow. path to the common di scharge header requirements,.and.:.
common dischargeheader'to the steam generators flow path requirements.
T',. There are two. AFW pump suction flow-paths from.t he Condens-ate Stotage Tank 'to'the 'AFW pumps'.
One flow path to the turbine driven AFW pump, 'and' one flow path to both motor driven AFW pumps.
There are 'three..AFW pump:
discharge flow paths to the common discharge header, one flow-path from each of the three AFW pumps.
There are two AFW discharge flQw paths from the common discharge header to the steam generators, one flow path to'each steam generator. With 2-FW-44 open (normal position), the discharge from any AFW pump will be 'supplied to both steam"generators through the associated AEW regulating valves.
2-FW-44 should remain open when the AFW system is.
required to be OPERABLE (MODES 1, 2, and 3).
Closing 2-FW-44 places the plant in.
a configuration not considered as an initial condition in the Chapter 14.
accident analyses.
Therefore, if 2-FW-44 is closed while the plant is operating in MODES 1, 2, or 3, two AFW pumps should be considered, inoperable and the appropriate action requirement of Technical Specification 3.7.1.2 entered to limit.plant operation in this configuration.
A flow path may be considered inoperable as the result of closin a manual valve, failure of an. automatic valve to respond correctly to an actuation signal, or failure of the piping.
In the case. of an inoperable automatic AFW regulating valve (2-FW-43A or B), flow path OPERABILITY!can be restored by use of a dedicated operator stationed at the associated bypass valve (2-F-56A or B) as directed by OP 2322..
Failure of the common discharge header piping will cause both discharge flow paths to the steam generators to be inoperable.
An inoperable suction flow path to' the turbine driven AFW pump will result in one inoperable AFW pump.
An inoperable suction flow path to the motor driven AFW pumps will result in two inoperable AFW pumps.
The ACTION requirements of Technical Specification 3.7.1.2 are applicable based on the.
number of inoperable AFW pumps.
An inoperable pump discharge flow path from an AFW pump to the common
'discharge header will cause the associated AFW pump to be inoperable. The ACTION requirements of Technical Specification 3.7.1.2 for one AFW pump are applicable for each affected pump discharge flow path.
MILLSTONE'-
UNIT 2 B 34 7-2a Amendment No.
0899 Corrected by letter dated 11/26/20C
PLANT SYSTEMS TSCR 2-4-02
-Octobet:'18, 2002
- BASES, 3/4.7.1.2 AUXILIARY FEEDWATER PUMPS (Continued)
AFW must be capable of lingdeiveVe'd to both steam generators for design basis accident mitigation.
Certain design basis events, such as. a main. steam line' break or'steam generator tube rupture, require that the
.affected steam generator be -so1ated, 'nd the RCS-decay heat removalsafety frunction be satjisfie d'.by ',feedig *nd steamng.' the unaffected steam generator.,.
If a failure in an'.AFW discharge flow path froi the.oni,'
discharge header to a steamgeneratr prevents delivery 'of'AFW to.a steam generator, then the. design basis events may notbe ffectively mitigated..
In this s.it.uation-,
the',ACTION requirements. of Technical :Specification 3,0.3 are appl icable and an' immediate plant shutdown is-appropriate.
.Two.inoperable AFW. System discharge flow paths from the common discharge header. to both steam' generators will esitlt. in a complete'l osso'f the ability to supply AFW.flow"tothe steam.geerators.
In'this sitat4.on, all-a ree AFW.pumps are inoperable and the'ACTION requirements of Technical Specification,.3.7.1'.2:-arte app'li~cable; Immed i ate, correctiv
'action.is,.,
required:. Howevr, a' plant' shntdow'is not:appropriateunti a discharge flow -path from the -common dis:charge' header to one steam. generator is restored..
During quarterly surveillance testing of the turbine driven AFW pump, valve :2-CN-27A is closed' and valve 2-CN-28 is opened to prevent-overheating the water being circulated..'. In this configuration, the suction of. the turbine driven AFW pump is -aligned
'to, the Cond nsate Storage Tank via the motor driven AW pump suction flow path, and the pump minimum flow is directed to the Condensate Storage Tank by the turbine driven AFW pump suction path upstream of 2-CN-27A in the reverse direction.
During this surveillance, the suction path to the motor driven AFW pump suction path remains OPERABLE, and the turbine driven AFW suction path is inoperable. In this situation, the ACTION requirements of Technical Specific-ation 3.7.1.2 for one AFW pump are applicable.
3/4.7.1.3 CONDENSATE STORAGE TANK The OPERABILITY of the condensateistorage tank with.the minimum water volume ensures that sufficient water is available for coldown of the Reactor Coolant System to less than 3007F in the event of a total loss of off-site power.
The minimum water volume is sufficinit to maintain the.RCS at HOT STANDBY conditions for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> with steam discharge to atmosphere.'
The contained water volume limit includes an
- allowance for.water not usable due to discharge nozzle pipe elevation above tank bottom, plus an allowance for vortex formation.
3/4.7.1.4 ACTIVITY The limitations on.secondary system specific activity ensure that the resultant off-site radiation dose will be limited to a small fraction Corrected by letter dated 11/26/2003.
MILLSTONE - UNIT 2 B 3/4 7-2b Amendment No. #P, #D, 91, 0789 I. Zli.