ML20044D038

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Proposed TS 3.7-1 Reducing Maximum Allowable Linear Power level-high Trip Setpoints Associated W/Inoperable Steam Line Safety Valves
ML20044D038
Person / Time
Site: Arkansas Nuclear Entergy icon.png
Issue date: 05/07/1993
From:
ENTERGY OPERATIONS, INC.
To:
Shared Package
ML20044D037 List:
References
NUDOCS 9305170100
Download: ML20044D038 (11)
v • d • e


Text

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l PROPOSED TECHNICAL SPECIFICATION CHANGES  :

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i 9305170100 930507 PDR- ADOCK 05000368 P PDR

3/4.7 PLANT SYSTEMS 3/4.7.1 TURBINE CYCLE "

SAFETY VALVES LIMITING CONDITION FOR OPERATION 3.7.1.1 All main steam line code safety valves shall be OPERABLE with lift settings as specified in Table 3.7-5.

APPLICABILITY: MODES 1, 2 and 3*.

ACTION:

a.

With both reactor coolant loops and associated steam generators in operation and with one or more main steam line code safety valves inoperable, operation in MODES 1, 2, and 3 may proceed provided, that within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, either the inoperable valve is restored to OPERABLE status or the Linear Power Level-High trip setpoint is reduced per Table 3.7-1; otherwise, be in at Isast HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. -

b. With one reactor coolant loop and associated steam generator in operation and with one or more main steam line code safety valves associated with the operating steam generator inoperable, operation in MODES 1, 2 and 3 may proceed provided:
1. That at least 2 main steam line code safety valves on the non-operating steam generator are OPERABLE, and
2. That within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, either the inoperable valve is restored to OPERABLE status or the Linear Power Level-High trip setpoint is reduced per Table 3.7-2; otherwise be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

SURVEILLANCE REOUIREMENTS 4.7.1.1 No additional Surveillance Requirements other than those required by Specification 4.0.5.

code safety valves may be gagged and two (one on each header) may be reset for '

the duration of the test to allow the required pressure for the test to be attained. The Reactor Trip Breakers shall be open for the duration of the test.

ARKANSAS - UNIT 2 3/4 7-1 Amendment No. E), 134 i

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gj TABLE 3.7-1 3 -

( MAXIMUM ALLOWABLE LINEAR POWER LEVEL-HIGH TRIP SETPOINT WITil INOPERABLE STEAM LINE SAFETY VALVES DURING OPERATION WITH BOTH STEAM GENERATORS N

Maximum Allowable Linear Maximum Number of Inoperable Safety Power Level-High Trip Setpoint Valves on Anv Oreratine Steam Generator (Percent of RATED THERMAL POWER) i 1 91.0 2 67.7 3 45.0 M>

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3/4.7 PLANT SYSTEMS BASES 3/4.7.1 TURBINE CYCLE 3/4.7.1.1 SAFETY CYCLES The OPERABILITY of the main steam line code safety valves ensures that the secondary system pressure will be limited to within 110% of its design pressure of 1100 psia during the most severe anticipated system operational transient. The maximum relieving capacity is associated with a turbine trip from 100% RATED THERMAL POWER coincident with an assumed loss of condenser heat sink (i.e., no steam bypass to the condenser).

The specified valve lif t settings and relieving capacities are in accordance with the requirements of Section III of the ASME Boiler and Pressure Code, 1971 Edition. The "as-found" requirements are conservative with respect to Section XI of the ASME Boiler and Pressure Vessel Code, 1986 Edition, and Addenda through 1987. The total relieving capacity for all MSSVs is 14,804,000 lb/hr. The ANO-2-fu11 power (100%) steam flow plus 2% for conservatism is 12,950,000 lb/hr.

Therefore, the total relieving capacity of the MSSVs is 114.32% of the 102% power steam flow through each main steam header. A minimum of 2 OPERABLE safety valves per steam generator ensures that sufficient relieving capacity is available for removing decay heat.

STARTUP and/or POWER OPERATION is allowable with safety valves inoperable within the limitations of the ACTION requirements on the basis of the reduction in secondary system steam flow and THERMAL POWER required by the reduced reactor trip settings of the Power Level-High channels. The reactor trip setpoint reductions are derived on the following bases:

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SP = ' x (114.32%)

where:

SP = reduced reactor trip setpoint in percent of RATED THERMAL POWER

~ ARKANSAS . UNIT 2 B 3/4 7-1 Amendment No. 110

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PLANT SYSTEMS BASES f

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114.32% = Total maximum safety valve relieving capacity of 102% power ,

steam flow  !

X = Total relieving capacity of all safety valves per steam }

line in Ibs/ hour  !

Y =

Total Maximum relieving capacity of the inoperable safety I valve (s) in Ibs/ hour. In each case, the valves with the ,

, greatest relieving capacity were assumed inoperable, j 3/4.7.1.2 EMERGENCY FEEDWATER SYSTEM The OPERABILITY of the emergency feedwater system ensures that the I Reactor Coolant System can be cooled down to less than 350"F from normal operating conditions in the event of a total loss of off-site power.  ;

Each emergency feedwater pump is capable of delivering a total feedwater flow of 485 gpm at a pressure of 1100 psig to the entrance of i the steam generators. This capacity is sufficient to ensure that adequate -

feedwater flow is available to remove decay heat and reduce the Reactor '

Coolant System temperature to less than 350'F when the shutdown cooling .

system may be placed into operation.  !

3/4.7.1.3 CONDENSATE STORAGE TANK i

The OPERABILITY of the condensate storage tank with the minimum water ,

volume ensures that sufficient water is available to maintain the RCS at,  !

110T STANDBY conditions for one hour with steam discharge to atmosphere I with concurrent with total loss of off-site power. The contained water j volume Ifmit includes an allowance for water not usable because of tank i discharge line location or other physical characteristics. I l

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ARKANSAS - UNIT 2 B 3/4 7-2 .

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= ENTERGY ARKANSAS NU N AR ONE CALCUIATION COVER SHEET Calc. No.: @E-occ3-o/

fk-7,4r vnit 2 Category O Ca}c.

Title:

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Pcg:s Revised and/or Added:

Purpose of Revisions  %!4'. / TS$X 4' #E a e r

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Check if Additional Revisions:

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Purpose:

The purpose of this calculation is to determine the i allowed reactor power levels for varying numbers of inoperable main steam safety valves. These power levels will be used as basis for a change to Technical Specification 3.7.1.1 to ensure i the peak design secondary system pressure limit of 110% of 1100 psia is not exceeded (an ASME code requirement). This  !

calculation is being performed since Technical Specification  !

3.7.1.1 does not, at this time, adequately restrict power ,

levels with inoperable MSSVs (Ref. 1).

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References:

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1) CR-2-92-0492, 12/04/92.
2) Calculation No. 90-E-0096-12, Rev. O, Reload Analysis For Cycle 10, 11/6/92.
3) ANO-2 Technical Specifications.
4) ANO-2 Safety Analysis Report, Amendment No. 10, Section No.  !

10.3.2.1.

Discussion of Problem:

In the event of a loss of load transient, such as a Loss of Condenser Vacuum (LOCV), the steam generated by the RCS must be relieved to prevent overpressurization of the secondary side. To accomplish this there are five (5) secondary system safety relief valves on each main steam header, outside containment, upstream of the Main Steam Isolation Valves (MSIVs). The MSSV design includes staggered setpoints such that only the number of valves needed will lift. The purpose of the MSSVs is to limit secondary system pressure to lower than 110% of the nominal design pressure of 1210 psia (design pressure is 1100 psia, Ref. 4) when passing 100% of. design steam flow. If one or more of the MSSVs is inoperable then  !

reactor power may need to be adjusted to prevent the steam produced from the RCS from exceeding the degraded steam relief capacity. If the RCS were to produce more steam than the secondary side could relieve, overpressurization of the secondary side upon load rejection could result.

During a load rejection transient the turbine stop valves close and essentially " bottle up" the steam line (SDBCS is assumed to not be in operation to relieve the steam flow). [

Secondary pressure would then rise to the point at which flow >

$ wo,,y CALCULATION NUMBER ,

~ operatims 93-E-0003-01 ARKANSAS 01/15/9: wc 0 @A> NUCLEAR PAGE I REY. DATE BY 1 4 CHK'D ONE NUMBER 0F

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from the relief valve equaled the steam production rate.

I Therefore, to prevent overpressurization of the secondary side  !

with inoperable MSSVs, reactor power must be reduced to ensure  :

that the RCS does not produce more steam than can be relieved i by the secondary side. j i

Assumptions:

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1) The Steam Dump Bypass Control System (SDBCS) is assumed to .

not be in operation.

2) The two steam lines do not communicate or equalize in  !'

pressure. This is the same as assuming that one or both MSIVs  ;

are closed (worst case configuration).

3) The full power steam flow will be increased 2% for conservatism.

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4) The total steam flow from the secondary side relief valves l is equal to the sum of the rated flows of the individual valves. This is very conservative since the flow from a relief ,

valve exceeds rated at inlet pressures above accumulation. t

5) Instrument uncertainty will not be included in the reactor  !

power levels developed in this calculation. I

6) Steam production / flow from each steam generator is assumed to be 50% of the full power steam flow. This ignores any small differences in steam production rates due to tube plugging and  ;

sleeving.

7) The MSSVs will be assumed to be inoperable in order _from the valve with the highest rated flow to the valve with the lowest rated flow. '
8) An implicit assumption in this calculation methodology is that main feedwater temperature is assumed.to be constant for  !

all power levels. This means that the steam production rate i

per unit energy produced is assumed to be constant at all power i levels (constant secondary delta-enthalpy). This is i conservative since main feedwater temperature drops with

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reduced power levels which decreases the amount of steam i produced per unit energy due to the increase in feedwater j enthalpy. i

@ s,% CALCULATION NUMBER .

operanons 93-E-0003-01 ARKANSAS 0 01/15/93 h Tuc- NUCLEAR PAGE REV. DATE- BY CHK'D ONE NUMBER 2 OF

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Analysis:

The full power (100%) steam flow for ANO-2 is 12.7E06  !

lb/hr (Ref. 2). This will be increased 2% for conservatism  ;

(assumption No. 3):

1.02*12.7E06 = 12.95E06 lb/hr l The rated flows for the 10 Main Steam Safety Valves (MSSVs) (Ref. 2) are tabulated below Valve Tag Number Rated Flow (lb/hr) 2PSV-1002/1052 1.438E06 2PSV-1003/1004/1053/1054 1.473E06 ,

2PSV-1005/1006/1055/1056 1.509E06  !

For conservatism the total rated flow on one side of the steam line will be taken to be the total rated flow for a steam line  !

or:  !

1.438 + 2(1.473) + 2(1.509) = 7.402E06 lb/hr ,

This maximum relief rate of 7.402E06 lb/hr is:

i 7.402/(12.95/2) = 114.32% .j of the 102% power steam flow through each main steam header.  :

If 1 MSSV is inoperable (assumed to have the highest rated

  • flow) the new relief capacity is:

114.32%*(7.402 - 1.509)/7.402 = 91.0%

With 2 MSSVs inoperable: i 114.32%*(7.402 - (2(1.509))/7.402 = 67.7%  ;

With 3 MSSVs inoperable:

114.32%*(7.402 - (2(1.509) + 1.473))/7.402 = 45.0% l t

Operation with less than 2 operable MSSVs is not allowed per reference 3.

i dS ento,yy CALCULATION NUMBER  :

operations  ;

93-E-0003-01 <

ARKANSAS O 01/15/92 @ @C NUCLEAR PAGE  !

REV. DATE BY 3 CHK'D ONE NUMBER OF ___ i 4

conclusion:

The allowed reactor power levels based on the number of inoperable MSSVs on one steam line are tabulated below:

l Number of Allowed Reactor l Inoperable MSSVs Power Level (%) l l

0 100  ;

1 91.0 2 67.7 i 3 45.0 i l

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i Oentergy CALCULATION NUMBER operauons 93-E-0003-01 AltKANSAS O 01/15/9: @v Tat NUCLEAll PAGE I ItEV. DATE 4 4 BY CIIK'D ONE NUMBElt cr 1

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