ML20203J889
| ML20203J889 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/24/1986 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20203J881 | List: |
| References | |
| NUDOCS 8608060064 | |
| Download: ML20203J889 (11) | |
Text
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PLANT SYSTEMS AUXILIARY FEEDWATER SYSTEM LIMITING CONDITION FOR OPERATION
- 3. 7.1. 2 At least three independent steam generator auxiliary feedwater pumps and associated flow paths shal1 be OPERABLE with:
- a. Two motor-driven auxiliary feedwater pumps, each capable of being powered from separate shutdown boards, and
- b. One steam turbine-driven auxiliary feedwater pump capable of being i powered from an OPERABLE steam supply system.
APPLICABILITY: MODES 1, 2 and 3.
ACTION:
- a. With one auxiliary feedwater pump inoperable, restore the required au),iliary feedwater pumps to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least HOT STANDYBY 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 HOT SHUIDOWN within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
- b. With two auxiliary feedw6ter pumps inoperable, be in at least HOT STANDBY within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in HOT SHUTDOWN within the following 6 C hours,
- c. With three auxiliary feedwater pumps inoperable, immediately initiate corrective action to restore at least one auxiliary feedwater pump to OPERABLE status as soon as possible.
SURVEILLANCE REQUIREMENTS 4.7.1.2 In addition to the requirements of Specification 4.0.5 each auxiliary feedwater pump shall be demonstrated OPERABLE by :
- a. Verifying that:
rse ffsqutRico N/am#
- l. each motor-driven pump develops %-di f f erential pressure *4--
$5greater G C Os<?E thcc" M cr M eq=!
'%N tah*b?a%
13"7 xs.) ;d _og" recirculation flow. (629'^'""' W i
- 2. thesteam-turbi.iedrivenpumpdevelops,/differentialpressure af greater the er equ2! to '!S2 pid on recirculation flow J when the secondary steam supply pressure is greater than 842 psig. The provisions of Specification 4.0.4 are not applicable for entry into MODE 3. ( /arQu,.tuo W ~,-%
Ot GPMwst%. }"2&%.ex i s t.uc in o stu M i e-oc#
ess<-st.
, , f% WT* / d Stres c rr M s, ) u n i, n- - 'm' mim 6 0 w "
SEQUOYAH - UNIT 1 3/4 7-5 M, h . . i. L . ?2 8608060064 860724 PDR P ADOCK 05000327 PDR __ _ __ -
PLANT SYSTEMS s
BASES V = maximum number of inoperable safety valves per steam line
-U =
maximum number of inoperable safety valves per operating steam line.
109 =
Power Range Neutron Flux-High Trip Setpoint for 4 loop operation.
76 = Maximum percent of RATED THERMAL POWER permissible by P-8 Setpoint for 3 loop operation.
X = Total relieving capacity of all safety valves per steam line in Ibs/ hour, 4.75 x 106 lbs/ hour at 1170 psig.
Y = Maximum relieving capacity of any one safety valve in lbs/ hour, 950,000 lbs/ hour at 1170 psig.
3/4.7.1.2 AUXILIARY FEEDWATER SYSTEM The OPERABILITY of the auxiliary feedwater system ensures that the 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.
The steam driven :=i'iary fcciater pu=p i: capabic of d;1ivering 300 gpr (tet:1 faciatcr f?:w) and ;;cn of the electric driven auxiliary feedwater pumps arc c:pabic cf delivering MO gpa (total feedwater-f%r)-to the entrance g5e of the steam generatorsq:t :te: generate. pressures less thar 1100 psia. At
% 1133 p;ic the-epen :te:: generater cafety va!vc(:) are capab? Of relieving at least 11% of nominal stc;; fi;w. A total faiSatar flow of 440 gpa at prc :ure: !cc: th:n 1133 p;i: i: cuf'icient ic en:urc that adequate feedweter TWs3 flow is available to remove decay heat and reduce the Reactor Coolant System temperature to less than 350*F where the Residual Heat Removal System may be placed into operation.
i 3/4.7.1.3 CONDENSATE STORAGE TANK The OPERABILITY of the condensate storage tank with the minimum water volume ensures that sufficient water is available to maintain the RCS at HOT STANDBY conditions for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> with steam discharge to the atmosphere concurrent with total loss of off-site power. The contained water volume limit includes an allowance for water not usuable because of tank discharge line location or other physical characteristics.
SEQUOYAH - UNIT 1 B 3/4 7-2
INSERT A This feedwater will- be delivered at a flow rate adequate to ensure sufficient coolant inventory in the steam generators to remove heat in all design conditions while steam generator safety valves are relieving.
6 0
9 UNIT 2 PROPOSED CHANGES l
-- - - - . _ __ _ v--
PLANT SYSTEMS '
AUXILIARY FEE 0 WATER SYSTEM LIMITING CONDITION FOR OPERATION 3.7.1.2 pumps and associated flow paths shall be OPERABLE with:A a.
Two motor-driven auxiliary feedwater pumps, each capable of be powered from separate shutdown boards, and b.
One from anturbine-driven OPERABLE steamauxiliary feedwater pump capable of being powe supply system.
APPLICABILITY: MODES 1, 2 and 3.
ACTION:
a.
With one auxiliary feedwater pump inoperable, restore the required auxiliary within feedwater the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. pumps to OPERABLE status w -
b.
With two auxiliary feedwater pumps inoperable, be in at least HOT C STANDBY 6 hours, within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in HOT SHUTDOWN within the followin c.
With three auxiliary feedwater pumps inoperable, immediately initiate to OPERABLE status as soon as possible. corrective action to re SURVEILLANCE REQUIREMENTS 4.7.1.2 feedwater pump shall be demonstrated OPERABLE by:In addition
, a. Verifying that:
\
gg,p s,u, %
- 1. V
! each
- ther. ermotor-driven cau pump develops e differential pressure cf gr;ater o,o=e u.cn A n
- ! te 1397 cid-on recirculation
/4 #5Nr #evshtwa4 5.)pa.cseu<efpaie acnen Pme is flow.(42G'MEo e mo-u s
- 2. tosrno en oev u c M ui-s
-vre< /CC9 u ut4 ea M i m .=.h the steam-turbine driven pump developsv'e-differential pressure cf greater thar er cqual to 1103 psid-on recirculation flow when the secondary steam supply pressure is greater than 842 psig entryprovisions The into MODEof3.( Specification 4.0.4 are not applicable for I B(Q""'^ ~~~h gge mas ,s c. ,srvo w A M"m ut..r e e e+a A v54 44~ "' A r
< m sr m r'** S -)
k,I s
SEQUOYAH - UNIT 2 A;.c..J._.a 2 3/4 7-5
- ft3;g;
PLANT SYSTEMS BASES SAFETY VALUES (Continued) 109 = Power Range Neutron Flux-High Trip Setpoint for 4 loop operation 76 = Maximum percent of RATED THERMAL POWER permissible by P-8 Setpoint for 3 loop ope. ration.
X = Total relieving capacity of all6 safety valves per steam line in 1bs/ hour, 4.75 x 10 lbs/hr at 1170 psig
=
Y Maximum relieving gapacity of any one safety valve in 1bs/ hour, 9.5 x 10 lbs/hr at 1170 psig.
3/4.7.1.2 AUXILIARY FEEDWATER SYSTEM The OPERABILITY of the auxiliary feedwater system ensures that the 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.
The steam driven auxiliary facdwater pump is capable of delivering 000 gpa (tota! fee &:ter '!:w) and :::h Of the electric driven auxiliary feedwater pumps 0r: ::;'ubic Of delivering tt0 gp; (total feedwater ficw) to the entrance
[
m.
of the steam generators. fat :t:= generator pressures less than 1133 psis. At 1133 pri: the Open :te= generater :sfety valvc(:) are capable of relieving at-100:t 11% n= ins! :t = ficw. A total feedw;ter flow of 440 gpa at pressures .
10 : than 1133 p:f: i: cuf#fci:nt t: =:ur that ad quat: f::dw;te- fl availabletoremovedecayheatandreducetheReactorCoolantSystN#owis temperature to less than 350 F where the Residual Heat Removal System may be placed into operation.
3/4.7.1.3 CONDENSATE STORAGE TANK The OPERABILITY of the condensate storage tank with the minimum water volume ensures that sufficient water is available to maintain the RCS at HOT STANOBY conditions for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> with steam discharge to the atmosphere concurrent with total loss of off-site power. The contained water volume limit includes an allowance for water not usable because of tank discharge line location or other physical characteristics.
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 of 10 CFR Part 100 limits in the event of a steam line rupture. This dose also includes the effects of a coincident 1.0 GPM primary to secondary tube leak in the steam generator of the affected steam line. These values are consistent with the assumptions used in the accident analyses. h SEQUOYAH - UNIT 2 8 3/4 7-2
INSERT 3 This feedwater will be delivered at a flow rate adequate to ensure suf ficient coolant inventory in the steam generators to remove heat in all design conditions while steam generator safety valves are relieving.
ENCLOSURE 2 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 DOCKET NOS. 50-327, -328 (TVA SQN TS 71)
Justification to delete specific differential pressure values required by SR 4.7.1.2.a.1 and SR 4.7.1.2.a.2 that proved operability of the motor-driven and steam-driven auxiliary feedwater pumps. These values are also being deleted from the bases. They will be placed in the appropriate plant instructions. .
Description of Channes This change will delete specific differential pressure values required by SR 4.7.1.2.a.1 and SR 4.7.1.2.a.2 to prove operability of the motor-driven auxiliary feedwater (AFW) pumps and the steam turbine-driven pumps. The SR will now refer to applicable plant instructions for characteristic differential pressure values for each pump. Specific values are also being
-deleted from the bases.
Reason for Change During the cycle 2 refueling outages for each unit, PCV-3-122 and PCV-3-132 for the motor-driven AFW pumps were replaced by cavitating venturis (CVs).
The CVs require that the motor-driven AFW pumps develop a higher differential pressure to maintain proper flow to the steam generators. Present technical specifications require that a differential pressure greater than 1397 psid be developed on recirculating flow. This value is not high enough to verify system performance with the new CVs installed.
Justification for Change i
The motor-driven AFW pump requires a flow limiting device to maintain constant pressure in order to preclude pump runout. This function was previously accomplished using hydraulically controlled pressure control valves (PCVs).
SQN had experienced repeated maintenance problems with the electrohydraulle operators which reduced the reliability of the valves in question.
Approximately 18 potential reportable occurrence reports had been written i since 1980 along with numerous maintenance requests (MRs). The PCVs were determined to be a high priority reliability problem with the AFW system.
During the cycle 2 refueling outages for each unit, CVs were installed to replace the PCVs. The new CVs perform the safety functions under the same normal and accident conditions that were previously performed by the PCVs and also increase the overall reliability of the AFW system by reducing the number of moving parts.
l l
The design of the venturi calls for water to be forced through an opening more restrictive than with the previous pCVs. The increased system resistance requires a greater total developed head to ensure an adequate flow rate, thus producing a higher differential pressure across the pump. To ensure adequate AFW flow rate, the minimum required differential pressure for each pump will be a function of the specific pump characteristic and associated system resistance. The surveillance requirement currently specifies a single differential pressure value for all motor-driven pumps for the acceptable AFW flow. This technical specification change will require the higher pump differential pressure due to the new CVs and also give some flexibility for changes in system resistance.
The new pump dif ferential pressure values and minimum head required to ensure pump operability were calculated by the TVA Division of Nuclear Engineering (DNE). DNE also calculated a value for maximum allowable head degradation at recirculation flow. The increase in system resistance reduces the allowable pump degradation and raises the minimum acceptable pump head necessary to satisfy operability requirements.
The minimum acceptable head at a recirculation flow (quarterly test conditions) was determined using the pump head based on vendor's test curves.
An allowance for instrument error and the difference between actual head and required head was made. The required head was calculated by two different methods to arrive at a value to ensure a pump flow rate of 465 gpm at a steam generator pressure of 1100 psia. Method one used the original calculations corrected for the values for the venturi differential pressure losses based on the results of the post modification test (pMT). Method two used the system resistance measured by the pMT. Method one yielded the more conservative results. The new differential pressure values were calculated based on changes in mass flow rates, specific volumes, viscosities, friction factors, and pipe diameters. Theso values are more restrictive than current specification criteria.
It is expected that over the plant's lifetime, due to changes in the fluid characteristics of the AFW system and possible system realignments, these differential pressure requirements will require further change. Removal of specific values from technical specifications for this differential pressure measurement and placement in applicable plant instructions will allow use of the process described in 10 CFR 50.59 (USQD) for an engineering evaluation and safety analysis without causing the unnecessary burden to NRC and TVA of a change to technical specifications.
present technical specifications for the steam turbine-driven AFW pumps require a differential pressure greater than 1183 psid be developed on recirculation flow when secondary steam supply pressure is greater than 842 psig to prove pump operability. Although no modification has presently been made to change system resistance and dif ferential pressure requirements, the possibility for changes to occur in the future does exist for reasons stated above. Removal of specific values in the technical cpecification and referral to plant instructions will prevent unnecessary future technical specification changes for the steam turbino-driven pumps.
ENCLOSURE 3 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 DOCKET NOS. 50-327, -328 (TVA SQN TS 71)
Determination of no significant hazards considerations to delete specific dif ferential pressure values required by SR 4.7.1.2.a.1 and SR 4.7.1.2.a.2 that proved operability of the motor-driven and steam-driven auxiliary feedwater pumps. These values are also being deleted from the bases. They will be placed in the appropriate plant instructions.
Significant Hazards Considerations
- 1. Is the probability of an occurrence or the consequences of an accident previously evaluated in the safety analysis report significantly increased?
No. The AFW system is a safety system that supplies, in the event of a loss of main feedwater supply, sufficient feedwater to the steam generators to remove primary system stored and residual core energy. The new CVs perform all the pCVs safety functions under the same normal and accident conditions. The higher differential pressure required due to the installation of the CVs does not prevent the motor-driven pumps from delivering sufficient feedwater to the steam generators. No changes are being made to the steam turbine-driven pumps. Pump operability will remain the same.
By removing specific values from technical specifications and placing them in the plant-controlled instructions, changes to plant design can be evaluated by these instructions and Unreviewed Safety Question (USQ) criteria of 10 CPR 50.59. This change does not affect the probability or i
consequences of any accident previously evaluated since changes to the system and procedures would require satisfactory compliance with 10 CFR 50.59.
Failure to meet this criterion would constitute a USQ which requires Commission notification before change.
- 2. Is the possibility for an accident of a new or different type than evaluated previously in the safety analysis report created?
No. The reason for this technical specification change is the installation of the CVs. A safety evaluation has been completed to analyze operation of the AFW system after this modification. The increase in differential pressure is due to the inherent characteristics required to perform the same pump duties. The differential pressure for the steam turbine-driven pumps is not being changed. Any future changes to the procedures or system design will require satisfactory compliance with 10 CFR 50.59 or prior NRC approval for a USQ. The possibility for a new or different type of accident is not created.
- 3. Is the margin of safety significantly reduced?
No. The new CVs perform the same duties as did the PCVs. The increase in differential pressure requirements does not change the performance of the motor-driven AFW pumps. The differential pressure for the steam turbine-driven pumps is not being changed. Technical Specification flow requirements are verified by meeting these differential pressure requirements. Any changes in plant design must be subject to the criterion of 10 CFR 50.59 (USQ) before their implementation.
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