ML20154F507
| ML20154F507 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 10/06/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20154F506 | List: |
| References | |
| NUDOCS 9810090249 | |
| Download: ML20154F507 (4) | |
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UNITED STATES g
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20666-0001
.....,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR PEGULATION RELATED TO ANIENDMENT NO.104 TO FACILITY OPERATING LICENSE NO. NPF-37.
AMENDMENT NO. 104 TO FACILITY OPERATING LICENSE NO. NPF-66.
AMENDMENT NO.
96 TO FACILITY OPERATING LICENSE NO. NPF-72.
AND AMENDMENT NO. 96 TO FACILITY OPERATING LICENSE NO, NPF-77 COMMONWEALTH EDISON COMPANY BYRON STATION. UNIT NOS.1 AND 2 BRAIDWOOD STATION. UNIT NOS.1 AND 2 DOCKET NOS. STN 50-454. STN 50-455. STN 50-456 AND STN 50-457
1.0 INTRODUCTION
By letter dated December 30,1997, Commonwealth Edison Company (Comed, or the licensee) proposed changes to the current Technical Specifications (TS) and the proposed improved Technical Specifications (ITS) for the Byron Station, Unit Nos.1 and 2, and Braidwood Station, Unit Nos.1 and 2. The proposed changes would revise TS 3.7.1.3 (ITS 3.7.6), " Condensate Storage Tank," and its cssociated bases to raise the minimum required condensate sturage tank (CST) level. The licensee also proposed to revise the auxiliary feedwater (AFW) pump suction pressure-low trip setpoint in TS Table 3.3-4, "Eng:neered Safety Features Actuation System Instrumentation Trip Setpoints"(ITS Table 3.3.2-1, " Engineered Safety Features Actuation System Instrumentation"). The AFW pump low-pressure trip automatically transfers the AFW pumps' suction from the CST to the ess;ential service water (SX) system. The proposed change is intended to ensure that the design basis requirements for the AFW system are accurately reflected in the TSs. The Byron and Braidwood units are currently operating with conservative administrative limits for minimum CST level.
The licensee proposed to increase the minimum required CST level from 40 percent to 75 percent for Byron, Units 1 and 2, from 40 percent to 80 percent for Braidwood, Unit 1, and from 40 percent to 66 percent for Braidwood, Unit 2. After a modification is installed on the AFW suction pressure instrumentation, a minimum required level of 60 percent will be required for Byron, Units 1 and 2, and a level of 57 percent will be required for Braidwood, Unit 2. The minimum required level of 57 percent will also apply to Braidwood, Unit 1, after the instrumentation modification is complete following additional modifications to increase the Unit 1 CST height.
Additionally, the licensee proposed to change the AFW pump low-pressure trip setpoint from 1.22 inches of Mercury vacuum (1.22" Hg) to 218.1 pounds per square inch absolute (psia) and change the ellowt.ble value from 2" Hg to 217.4 psia. The current 1.22" Hg and 2" Hg values are equivalent to 14.1 psia and 13.7 psia, respectively. Thus, the proposed change results in 9810090249 981006 DR ADOCK 05000454 PDR
i 2-1 increases in the trip setpoint and corresponding allowable value There is no pu per limit for the setpoint since the safety-related source of AFW is the SX system and an eartier than required transferis within the desi n basis.
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2.0 DACKGKOUNQ The AFW synem suppfb cooling w4er to the steam generators upon loss of main feedwater supply The AFW system amploys a motor driven (MD) pump and a diesel driven (DD) pump.
Norma!iy, both the MDAFW pump and the ODAFW pump take suction from the CST. Wher
..e cu i is usvaiiae, both g ups taka suction from the GX system. Gwitchover from the CST to
% GX ayttern h ehmigned to oce.ur au omatically on low pieenre in the AFW pump suction line t
m,qhd t Oh m ado riad of (M AFW 7yMem in 10M p hecn,ec ekobnal opepeidy couccms i nolveng the postulated failure of the nonmtkiy r2Ned G8 f piping m lho turNna buMng during a seismic event. The postulated f; Hrc m m non cism;c pipine codd poWhty msnit in #mo spheric pressum in the AFW pump 4.mn:na L5 the pmO:, s op@t of I.R' Hg (14.1 psia) for tho automatic switchover, a Vme
- ha om dwh piping muld rm3 in not reaching thu switchover setpoint because the dmo.phic prawa CMJ pO.) waa hbho-ihan ihn trip satpo;nt. As a result of this tof o W oGo,O.M
,, ad:WstrW.se!y indrawd ihn midmom CGT lcveis (for each unit) to c
wt :11 mn and rf prrc ad at Pr ; Nnod Tim a6opun udministrativo I;mit at
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y ami,N wi Wt P.
m L.h ch'nyd to,0 penwnt afts tha phpical height of the tank was r
nis M TM VW pmnp wSchover hip setpoint we aba raind from 14.1 to 18.1 psia and the N pm ;are a:vn Mpuin!we @,vd from & ! o M.1 psia. A low pressore AFW pump trip, desia ed to praW'. fbe no ups fnwn iow of vfian, was likewise raised from 12.5 psia to 16.5
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'0 M4dAHON
- M op n; d iho Wi Jh tha comrut 16 manum watu fovol of 40 percent s intended (TS l
%t. b m.-Q b an< ura tat soment waty (Nd,000 gal!ons) is available to maintain the reactor l
vu%t plam (RGiU wi hni sisodhy condiens for at Ioast 9 homs with steam discharge to the A..w %.. c, m m n m ! - @ h h ! w. d o a g e p,y m r
we en/.im Wmmpdu.oda odgo calcoution to determine the minimum m,9,y giume of e b 4 e *,:;T to m ;ot the deign and licensing basis requirements l
f 2dn 5 4 galkw anilai;i, le e LWb Thia calco!mion accounted for design issues including instrmnal uncedainty,.ep%noni stuain genemtons at Byron, Unit 1, and Braidwood, Unit 1, and Omc affecting thu s suma of umbM water n tb CS f The calcuhtion also involved drendning the : mount er waict,Muired to minimize the potential for an inadvertent switchover I
of the AFW pump sue: ion TWn the CS f to the SX system. The automatic switchoveris designed to occur under emwgency enditions if the CGT becomes unavailable (e.g., due a scismic event or a tomado).
E After the opomaildy concern from 1994 was addressed, a modification was designed to the AFW section p. essure instrumentation to fdtcr the pressure spike signal that occurs during the startup of a MDAFW pump. Thh modifierdion win help reduce the potential for an inadvertent switchover of the AFW supply from the CGT to the SX system. Therefore, the proposed TS minimum level i
also deemases from the original administrative limit after the modification is installed.
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3-The proposed minimum CST level reflects a conservative value that bounds the TS basis requirements for the CST. The new analysis considered the licensing basis requirements for the AFW system along with the physical characteristics of the CSTs and associated piping. For examp%, the suction pressure transient and fluid vortexing in the CSTs following AFW pump actuation were taken into consideration and conservatively modeled in the analysis. In addition, conservative levolinstrumentation uncertainties were calculated, and finally, a reconstitution of the AFW requirements for cooldown and the impact of replacement steam generators were calculated. The proposed changes are intended to ensure that all of the design considerations have been addressed.
The proposed minimum CST level reflects a conservative value that bounds the TS basis requirements for the CST. The level also ensures that sufficient water is available in the CST to i
minimize the potential for an inadvertent switchover to the SX system under emergency conditions, unless that switchover in required due to the unavailability of the CSTs. The revised levels also ensure that all accident analysis assumptions are met.
Based on the conservatisms in the licensee's analysis and the fact that the proposed changes in the required minimum volume are conseustive in nature (i.e., higher than the existing minimum required level) the staff concludes that the proposed changes to TS 3.7.1.3 (ITS 3.7.6) are acceptable. The licensee's proposed Bases for these TSs have also been reviewed by the staff, and the staff concluded that they adequately reflect the design requirements for the CST inventory.
The proposed changes to TS Table 3.3-4 (ITS Table 3.3.2-1) are intended to reflect the current design values for the AFW suction transfer trip setpoint and the design basis of the AFW system.
These proposed changes are also conservative in nature since they provide added assurance that the switchover to the SX system will occur in accordance with the design basis. Based on the conservative nature of the proposed changes v.hich increase the switchover setpoint, the staff concludes that these changes are also acceptable.
4.0
SUMMARY
Based on its review, the staff concludes that the proposed changes are necessary in order for the 7S requirements to be consistent with the design basis of the AFW system including General Design Criterion (GDC) 2, " Design Basis for Pmtection Against Natural Phenomena," and GDC 34, " Residual Heat Removal." The staff has further concluded that the changes are more conservative than the existing TS requirements and are consistent with the accident analysis of those events that assume a minimum volume of waterin the CST. The proposed changes also provide added assurance that the aummatic suction switchover will function as designed upon loss of the CST while minimizing the potential forinadvertent switchover. The staff has, therefore, concluded that the proposed changes are cceptable.
5.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Illinois State official was notified of the proposed issuance of the amendments. The State official had no comments.
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6.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (63 FR 9596). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
7.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: W. LeFave C.Saadu 4
Date:
October 6, 1998 i
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