ML19308B980
| ML19308B980 | |
| Person / Time | |
|---|---|
| Site: | Crane, Davis Besse  |
| Issue date: | 02/15/1979 |
| From: | Cartin L BABCOCK & WILCOX CO. |
| To: | Luken R BABCOCK & WILCOX CO. |
| References | |
| TASK-TF, TASK-TMR NUDOCS 8001170721 | |
| Download: ML19308B980 (3) | |
Text
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..THE BABCOCK & WILCOX COMPANY POWEP. GENEP.ATION GROUP R. C. Luken. Nuclear Serrice
[a4 e
L. R. Cartin. Plant Integration (2335)
Cust.
File No.
or Ref.
Davis Besse 1 86-2972-00 Sunj.
Date Resoonse to TEC Letter T3W-505 Februarv 15. 1979 ln..i..............................,.
Re:
C. D. Domeck to A. E. Luzar, "DB-1 Dual Level Setpoints on Steam Genera-tors for Auxiliary Feedwater," T3W-505, dated January 2, 1979.
Please find a 10 CFR 50.59 evaluation of the dual level setpoint design change as requested in Question 5 of the above Reference.
Q.A.
The information presented is consistent with past B&W analyses and the conclusions drawn are applie-able to DB-1.
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%-M 72-Oo DUAL LEVEL SE*?CINT COCRCL OF THE STEAM GENERATORS FOR DM ;S-5 ESSE PCWER STATION UNIT 1 I
Tho " auto-essential," SG 1evel control has been modified to include afdual.
2setpoint. Following automatic cetuation of auxiliary feedwater by the Steam and Feedwater Rupture Control System (SFRCS), SG 1evel will be controlled to 35. inches;on the startup range indicators if no ESTAS actuation.(low RCS pressure or high RB pressure) of the High Pressure Injection '(HPI) System occurs'. For accident conditions whersiboth auxiliary feedwater and EFI are automatically actuated (indicative of loss of coolant accident conditions),
the auto-essential level control will regulate water addition to the SG's to achieve and maintain all20"~1ev'el (96" indicated) on the startup range in-strumentation. The'~use of a dual setpoint'is a change to SG 1evel. controls' (as.d'escribed 'in the Davis-Besse, Unit l'FSAR; and the safety evaluation pro-vided below is the"10 CFR 50.59 review of this change. The information pro-I*2 in vided, herein, is an extension of documentation supplied by letters December of 1978. These previous submittals were in. support of interia maa-isures, utilizing operator action, to control SG 1evels.
Incorporation of the dual setpoints into the auto-essential" level control on the SG's automate the operator actions which have been used in the interim pending completion of pernanent design changes.
Design changes to provide the dual level setpoint control, in lieu of a single setpoint when auxiliary feedwater is required, have been ' ade to maintain ade-m 3
quate. decay h'est removal and indicated pressurizer leve1 during anticipated 7
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events and to maintain consistency with the small break LOCA analysis (BAk*-
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10075A), which is applicable.for SG 1evAls as low as 120 inches.-
Test data and supplemental B&W analysis provided the design basis for the 35 inch (indicated) level which will be utilized for all anticipated events re-quiring auxiliary f eedwater at the DS Power Station Unit 1.
The natural cir-culation test (TP 800.04) demonstrated that the 35 inch (indicated) SG 1evel will provide adequate loop circulation for decay heat re= oval (see Note 1 for additional information). 3&L' analyses further show that pressurizer level is maintained on scale for reactor trips due to or followed by a loss of main j
feedwater or a loss of offsite power.
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The high, SG 1evel setpcin: (96 inches indicated) anticipa:ed usage is during design basis even:s only where both auniliary f eedwater and EPI are required.
The acciden: analysis presented in the DB-175AR for these events (LOCA's, SL3, etc.) re=ain valid with no decrease in =argin relative to established acceptance criteria.
In summary, the incorporation of the dual level se: point control for the steas generators is a1 desirable design change which will lead to improved Plant performance. This design change does not involve an anreviewed safety question because:
1.
The probability of occurance or the consequence of an accident or mal-function of equipment important to safety preeiously' evalus:ed in the FSAR has not been increased.
2.
The possibility of an accident or malfunction of a differe=: type tha:
is not bounded by a previous analysis in :he FSAR has not been created.
3.
The =argin of safety as defined in the basis for any Technical Specifi-cation has not been decreased.
Notes:
- 1., TECo letter to R. W. Reid, Chief Operating, Reactor Branch No. 4, Division of Operating Reactors, Serial No. 471, dated December 11, 1978.
2.
TECo letter to R. W. Reid, Chief Opera:ing Raactor 3 ranch No. 4, Division of Operating Reactors, Serial No. 475, dated December'22, 1978.
3.
SG 1evel is but one factor tha: contributes to =aintaining pres-surizer level on scale during anticipated events. Auxiliary feedvater addi: ion rates and secondary strea= pressure con:rol are also important. The dual level se: point con:rol p;rvides an integrated system to coordina:e steam generator level and aux-iliary feedwater addition races. Measure :o provide proper equip-ment operation which effect secondary pressure have been taken.
However, equip =ent calfunctions cannot be prevented with absolute certain:y. ;If pressure;1evel indi:stion is. lost (for any reason)
.during anticipated events,' this occurance is considered an opera-tional inconvenience and'not a safety problem. 'The operator can
' rely,on RC system pressure to assure that a level of water in the.
pressurizer is maintained.,
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