ML20198C296
| ML20198C296 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 12/30/1997 |
| From: | Graesser K COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20198C303 | List: |
| References | |
| BYRON-97-0315, BYRON-97-315, NUDOCS 9801070243 | |
| Download: ML20198C296 (9) | |
Text
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4 AHDfHi tfl% Call}) l ttiv Ni ( '1 pfHl1J n) e' ily ton 6tswraung st aisur 41%o Nonh Gonnan Liiun h 10,ad upon il 6 010$> >i tetsis n 4.,44 December 30,1997 1.TR: IlYRON 97 0315 111,1!: 2.01.0301 U. S. Nucleat Regulatory Commission NITN: Document Control Desk Washington, DC 20555
Subject:
App'acation for Amendment to Appendix A, Technical Specifications, to Facility OperatingiJernses llyron Station Units 1 and 2 1:acility Operatmg1.icenses NPIL37 and NPIL66 NRC Docket Nos. 50 454 and 50-455 liraidwocxl Station Units 1 and 2 Facility Operating IJcenses NPli.72 and NPIG77 NRC Docket Nos. 50-436 and 50 457
" Condensate Storage Tank (CST) level" Pursuant to 10 CFR 50.90, Commonwealth IMson (Comlki) proposes to amend Appendix A, Technical Sp-cifrations, of Facility Operating licenses NPF 37, NPIL66, NPI'-72, and NPl<-77. Comlid proposes to revise Technical Specification 3.7.1.3, Condensate Storage Tank," and its associated llases for Ilyton and liraidwood to raise the minimum allow able CST level. The proposed (hange ensures that a sufficient volume ofwater is available to meet the design basis requirements for the auxiliary feedwater (AI) system supply. Comed also proposes to revise the AF system transfer to essential service water (SX) trip setpoint and allowable value in Table 3 3 4, functional unit 6 g, to ensure that the design basis requirements for the AF system are accurately re Accted in the Technical Specifications.
Iloth Ilyron and llrtidwocxl Stations are currently cperating with conrervative administrative limits for minimum CST level. These administrative limits provide sufficient operating margin to ensure that the current design basis requirements for the AF system are met.
In October 1997, the NRC issued a Notice of Violation (NOV), as documented in Ilyron inspection Report 97-015, for failure to take timely corrective action in not submitting a license amendment request to re0cct the changes made to the minimum CST levelin 1994. In response to that NOV, Ilyron made a commitment to the NRC to submit a license amendment request to revise the minimum CST level in TS 3.7.1.3 and change the AF suctir n CST to SX trip setpoint in TS Table 3.3-4. This submittal reDects completion of that commitment.
I This proposed amendment request is subdivided as follows:
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I 9001070243 971230 h
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Deceniber.30,1997 Page1 U.S. Nuclear Regulatory Commission
- 1.
- Attac'hment A gives a description and safety analysis of the proposed changes in this amendment.
- 2. 1 includes the marked up Technical Specification pages for both the current il,ron and liraidwood Technical Specifications (CTS) and the liyron and liraidwood Improved Technical Specifications (ITS) with requested changes indicated 3.
Attachment C describes Comisd's evaluation performed in accordance with to CI R 50 92(c),
which coafirms that no significant hazards consideration is involved 4.
Attachment D provides the linvironmental Assessment.
This proposed amendment has been reviewed and approved by Comlid Onsite and Offsite lleview in accordance with Coml?d procedures.
Comikt is notif>ing the State ofIllinois of this application for amendment by transmitting a copy of this letter and its attachments to the designated state official 4
I affirm that the content of this transmittalis true and correct to the best of my knowledge,information and behef Please address any comments or questions regardmg this matter to this office.
Sincerely, N
li 1. Graesser Site Vice President liyton Nuclear Power Station b
Subsenbed and sworn to before me, a Notary Public, this day of Do-
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Notary PutWE55 tete odlinnene Notary Pflic
' y comm...ong,,,se 5 7 3 K1f./l.1, Attachments cc:
A.11 lleach - llegional Adminic.rator,11111 G. Dick - Pro}ect.\\lanager, NRR llyron Station Senior Resident Inspector C. Phillips liraidwood Station Senior Resident inspector Office of Nuclear I;acihty Safety -IDNS csr_uivt.txx l
A'lTACIIMENT A DESCRIPTION AND SAFETY ANALYSIS FOR Ti!E PROPOSED CIIANGES A.
SUMMARY
OF PROPOSED CilANGES Pursuant to 13 CF!; 50.90, Commonweahh Edison (Comed) proposes to amend Appendix A, Technical Speci6 cations (TS), of Facility Operating Licenses NPF-37, NPF-66, NPF 72, and NPF.
- 77. Note that in the text of this submittal, the current T(chnical Speci6 cation (CTS) changes will be noted Grst, and the corresponding proposed improved Technical Speci6 cation (ITS) changes will be noted in (
). Comed proposes to revise liyron and liraidwood TS section 3.7.1.3 (3.7.6),
" Condensate Storage Tank" and the associated liases to increase the minimum condensate storage tank (CST) water level to ensure that the design basis requirements for the auxiliary feedwater (AF) system are met.
Comed proposes to increase the minimum value from 40% to 75% for llyron Units 1 and 2, from 40% to 80% for liraidwood Unit 1, and from 40% to 66% for liraidwood Unit 2. After a medi6 cation is installed on the AF suction pressure instrumentation, a minimum water level of 60%
will be required for Ilyron Units 1 and 2 and a level of 57% will be required for liraidwood Unit 2.
The 57% requirement will appiy to liraidwood Unit 1 after the AF instrumentation modification is complete, along with a modi 6 cation to increase the CST height. Additionally, Comed proposes to revise the AU pump suction pressure low trip setpoint and the allowable velue in Table 3.3 4 (3.3.2 1), functional unit 6.g (6.f.) to reRect the design basis requirements of the AF system.
The proposed TS changes are described in detail in Section E of this attachment. Alark:d up pages are provided in Attachments 111 and 11-2 for Ilyron and liraidwood, terpectively, in Reference 1, Comed submitted an application for conversion to the improved Standard Technical Speci6 cations. Corresponding changea are also provided en the proposed ITS pages ir..
Attachments ll-la and ll 2a for Ilyron and liraidwood, respectively.
H.
DESCRIPTION OF TIIE CURRENT REQUIREMENTS TS 3.7.1.3 (3.7.6) requires that the CST have a contained water level of at least 40% in Stodes 1,2, and 3. Table 3.3-4 (3.3.2-1), functional unit 6.g. (6.f.) lists the AF pump suction pressure-low (transfer to SX) trip setpoint and allowable value. The trip setpoint value is 1.2Y' Iig vacuum, which corresponds ao 14.1 psia. The allowable value is 2" Iig vacuum, which corresponds to 13.7 psia.
C.
HASES FOR Tile CURRENT REQUIREMENTS The operability of the CST with the minimum water level of 40% ensures that suf6cient water (200,000 gallons) is available to maintain the reactor coolant system (RCS) at hot standby conditions
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for nine hours with steam discharge to the atmosphere concurrent with totalloss-of-offsite power.
C3T.lEvL IXW l
Anschment A - Safety Analyus
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'the contained water volume limit includes an allowance for water not usable because of tank discharge lire location or other physical characteristics.
Substction 10.1.9.1 3f the UI SAR identifies the design basis of the AF system. The function of the AF system is to provide adequate cooling water to the steam generators in the event of a loss-of-offsite power coupled with v:fious other accidents discussed in section 15.2.7 of the UFSAR. The AF system is designed to provide enough feedwater to cool the unit down safelj to the temperature at which the residual heat removal t.ystem can be used. 'the total amount of ferdwater required to replace steam vented to the atmos},here and to compensate for shrinkage during cooldown is 200,000 gallons for four steam generators. 'lhe original design analysis that supports the 200,000-gallon requirement is documented in Reference 2.
Although the p eferred source of water to the suction of the AF system comes from the Safet)
Category 11 CSTs, the UFSAR clearly indicates that the AF system is supplied with water from the Safety Category 1 SX system under emergency conditions. Switchover from the CST to the SX water supply is accomplished automatiolly on a low pressure in the suction line to the AF pump coupled with an autostart of the AF system.
D.
NEED FOR REVISION Ol'TIIE REQUIREMENT Comed is submitting this amendment reque>t to ensure that the TS requirement for minimum CST level re0ccts the current design basis requirements and the design of replactment steam generaters fot llyron Unit I and liraidwood Unit 1.
In 1994, Comi'd identified an operabihty concern involving the postulated failure of Safety Category 11 CST piping in the turbine building during a seismic event. This postulated failure of the non-seismic piping could eventually result in atmospheric pressure (14.7 psia) in the AF suction line.
This would minimize the potential for an automatic switchover of the AF water supply from the CST te SX water, since the previous trip setpoint value was 14.1 psia or 1.22" vacuum. In response to the operability concern, the minimum administrative CST levels were increased to 75% at llyron and 80% at liraidwood. The minimum administrative CST level for linddwood Unit 2 was later changed to 66% after the physical CST height was raised. Additionally, the AF pump trip setpoint was raised from 12.5 psia to 16.5 psia; the AF suction CST :o SX s vitchover setpoint was raised from 14.1 psia to 18.1 psia, and the AF low suction pressure alarm setpoint was raised from 16.1 psia to 20.1 psia. Each of these three serpoints was raised by four psia to maintain the same relative difference between the setpoints. These actions ensured thwt the automatic switchover of the AF water supply would occur when required.
Comed believed that these changes were conservative with respect to the current TS values, and llyron and liraidwood continue to operate with the revised setpoints and CST levels. Ilowever,in October 1997, the NRC issued a Notice cf Violation (NOV), as documented in llyron inspection Report 97-015, for failure to take timely corrective action in not submitting a license amendment request to re0cct the changes made in 1994. In response to that NOV,Ilyron made a commitment to the NRC to submit a license amendment request to revise the minimum CST level in TS 3.7.1.3
{ 3.7.6} and change the AF suction CST to SX trip setpoint in TS Table 3.34 (3.3.2-1). This submittal reDects completion of that commitment.
I CST.lEYl doc 2
Attsclunent A safety Analy,a l
_--_-._-____....__.__-____m_
In Reference 8, Comed performed a design calculation to determine the minimum required volume of water in the CST to meet the design and licensing basis requirements. His comprehensive calculation accounted for design issues including instrument uncertainty, replacement steam generators at Byron Unit 1 and Braidwood Unit 1, and factors affecting the volume of useable water in the CST. The calculation also invoked determining the amount of water required to minimize the potential for an inadvertent switchover from AF supply from the CST to SX. An inadvertent switchover occurs when the SX is used when the CST is still avadable. The CST contains demineralized water; the SX system normally contains river water. Introducing river water could lead to degradation in the eccondary systems. Therefore, sufficient water is currently maintained in the CSTs to meet the TS bases requirement in addition to minimizing the potential for a switchover of the AF water supply from the CST to SX, unless required. The switchover from the CST to SX would still occur under emergency conditions if the CST were unavailable (e.g., seismic event, tornado).
After the operability concern from December 1994 was addressed, a modification was designed to the AF suction pressure instrumentation to fdter the pressure spike signal that occurs during the startup of a motor-driven AF pump. This modification will help reduce the potential for an inadvertent switchover of the AF water supply from the CST to SX. Therefore, the TS minimum level also decreases from the original administrative limit after the modification is installed.
E. DESCRIPTION OF Tile PROPOSED CIIANGES Comed proposes to change TS 3.7.1.3 {3.7.6} and associated Bases. Comed proposes to revise this minimum value for CST operability from 40% to 75% at Byron Units 1 and 2, from 40% to 80% at Braidwood Unit 1, and from 40% to 66% at Braidwood Unit 2. The proposed minimum value is 60% at Byron and 57% at Braidwood Unit 2 following scheduled modifications on each unit for the AF suction pressure circurry. For Braidwood Unit 1, the minimum level wdl be 66".
following the moditkation to raise the CST, and then will be reduced to 57% after the AF l
instrumentation modification. The values are clarified by footnotes that explain which value is in effect. The minimum values are tied to fuel cycles that correspond to the modification schedules.
In addition, Comed proposes to change the Bases for TS 3.7.1.3 (B3.7.6} to state that the.
minimum water level in the CST meets the current licensing basis and ensures that an inadvertent switchover of the AF water si.pply from the CST to the SX system does not occur. The switchover would still occur under emergency conditions, as required,if the CST were unavailable. The proposed Bases delineate the requirements for CST inventory along with a discussion of the assumptions that were used to determine the minimum requirements.
Finally, Comed proposes to change TS Table 3.3-4 {3.3.2-1}, functional unit 6.g. {6.f.) to reflect the current design AF suction transfer trip setpoint and allowable value. The trip serpoint value in TS Table 3.3 4 will be revised from 1.22" 1Ig vacuum (14.1 psia) to > 18.1 psia; the allowable value in Table 3.3-4 {3.3.2-1) will be revised from 2" 1Ig vacuum (13.7 psia) to 2_17.4 psia.
CST.tlvt doc 3
Attahment A. kfety Analym
si F. SAFE'IY ANAISSIS Of Tile PROPOSED CIIANGES (I re ccts a conservative value that bounds the TS basis The proposed TS minimum &
o requirements for the h i x1 also ensures that sufficient water is available in the CST to minimize the potential tor an madvertent switchover to SX under emergency conditions, unless that
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switchover is required due to the unavailability of the CSTs. The revised requirement ensures that all accident analysis assumptions are met.
Per Reference 2, the amount of water required to maintain a unit in hot standby (> 3505, hiode 3) for nine hours following a reactor trip with a coincident loss-of-offsite power is 179,427 gallons.
This value was calculated by Westinghouse assuming a total RCS ve' me associated with the original steam gene. tors (SGs).
'the original SGs are being replaced at llyron Unit 1 and liraidwood Unit 1. The replacement SGs have a larger primary side volume, and operate at a le her secondary side pressure, saturation g
temperature, and stored energy mass. Consequently, the AF volume required to meet the design basis for Unit 1 is larger than that required for the original SGs. Comed has conservatively determined that a maximum 2692 additional gallons (Reference 7) of water is required for AF supply due the replacement SGs. Therefore, the total amount of useable water required to maintain a unit in hot standby conditions for nine hours with a totalloss-of-offsite-power is 182,119 gallons.
Note that the amount of water reported here does not consider the physical configuration of the CST or r.ssociated piping. The proposed changes to CST !evel bound this calculation.
UFSAR Subsection 10.4.9.1," Auxiliary Feedwater System Design liasis," desenbes an additional requirement for feedwater supply ta the AF system. Speci6cally, the function of the AF system is to provide adequate cooling water to the SGs in the event of a loss-of-offsite power coupled with various occurrences as 6scussed in Subsection 15.2.7 (Loss of Normal Feedwater Flow). With eithe: AF oump supplying the four SGs, enough feedwater is provided to cool the unit down safely to the temperature at which the residual heat removal system can be used. The to al amount of feedwater required to replace steam vented to :he atmosphere and to compensate for shrinkage during cooldown is 200,000 gallons for four SGs.
'lhe UFSAR further indicates that the SX system is the emergency source of water to the AF system. 'the requirement of 200,000 gallons of available water is currently reflected in the design basis analyses for the SX system and ultimate heat sink. Comed has veriRed that, with the replacement steam generators,200,000 gallons of useable water is suf6cient to meet this requirement. Reference 6 includes the analysis that supports the 200,000. gallon requirement. The proposed changes to CST level do not affect the capability of the SX system to supply the required volume of water to the AF system.
Maintaining 200,000 uxable gallons of water in the CST,in addition to maintaining suf6cient static head levelin the CST, provides high confidence that switchover of the AF supp'y to SX will not occur, except under emergency circumstances where the CST is unavailable (e.g., seismic event or tomado). 'lherefore, the analysis that was performed to determine the minimum acceptable CST level considered both the requirement to maintain 200,000 gallons of useable water in the CST and the requirement to maintain suf6cient static head m the CST to minirnize the potential for an inadvertent switchover.
CST IIvlJXE 4
Attachment A safety Analyu,
Minimiring the potential for inadvertent switchovers ensures the long-term availability and rehability of the steam generators. This is because the 5X system water introduces impurities that can eventually degrade the SGs. 'the usual source of SX system water is the river watei,which has relatively high concentrations of dissolved minerals and sediment compared to the CST water, which is demineralized. The SX system provides the safety.related source of water under emergency conditions; the CSTs are nonoafety related.
The analysis to determine the revised TS minimem CST tank level considered the hcensing basis requirements for the AF system alongwith the physical characteristics of the CSTs and associated piping. For example, the suction pressure transient and Duid vortexing in the CSTs following AF pump actuation was conservatively modeled in References 3 and 4, respectively. In addition, conservative CST levelinstrument uncertainties were calculated in Reference 5. Finally, a reconstitution of the AF system requirements for cooldown and the impact of the replacement SGs was calculated in lleferences 6 and 7, respectively. Collectively, all of the supporting calculations and documents in References 2 through 7 provided input into the minimurn CST level determination,which is documented in Reference 8. The proposed changes ensure all of the design considerations have been eddressed. All of the calculations that support the proposed TS minimum CST levels were prepared and/or reviewed and approved per the Comed Quality Assurance Standards.
The values for TS Table 3.3-4 (3.3.2-1}, Functional 1.' nit 6.g. {6.f.} are revised to reRect the current derign AF suction transfer trip setpoint values. The proposed changes to Table 3.3 4 [3.3.2.l}
ensure that the TS accurately reDect the design basis of the AF system. As doumented in Reference 9, the current AF suction transfer switchover setpoint of 18.1 psia has been conservatively determined to meet the design basis for the AF system. The setpoint of 18.1 psia and the TS allowable value of 17.4 psia were calculated assuming the postuhted failure of the CST and/or associated piping, thereby potentially exposing the AF suedon to atmospheric pressure (14.7 psia). Note that Comed is converting the measuremer.ts from inches of mercury to absolute pressure (psia). Both values are provided above for comparison; however, the calculation is perfomied using psia. Additionally, the original table did not clearly indicate that the v: dues were minimum values. The "?" symbol has been added for clarity. The reused values ensure that switchover from the CST to SX water supply will occur under emergency conditions when the CST water supply becomes unavailable (e.g., due to a seismic event or a tornado). Appropriate instrument uncertainties are considered in the revised values. The current design basis for the SX system ensures tha* suf6cient water is avadable to supply the AF system under emergency conditions.
ComRd plans to install a modi 6 cation to the AF suction pressure instrumentation to filter the pressure spike signal that occurs during the startup of an AF pump. The modification will help reduce the potential of an inadvertent switchover from the CST to SX that would result when the pressure spike momentarily falls below the switchover setpoint. lly fdtering the signal temporacily, the switchover would occur only when required. Before the modification is installed, a CST levd of 75% at Byron Units 1 and 2,80% at Braidwood Unit 1, and 66% at Braidwood Unit 2 ensures that the switchover serpoint will not be reached. After tha moditication, only a 60% level will be required at Byron and 57% levelwill be required for Braidwood Unit 2. Braidwood Unit I will require two modi 6 cations. First, the CST will be raised ten feet. This decreases the level requirement to 66% (Ihe Braidwood Uni; 2 CST has already been raised). After that, the AF instmmentation will be taodined, decreasing the level requirement to 57%. These values were cst _lEYLrXX Awhmnt A. safny Anahs l