ML20105C720
| ML20105C720 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 09/30/1992 |
| From: | Berry K, Ioakem J, Robare D COMMONWEALTH EDISON CO. |
| To: | |
| Shared Package | |
| ML20105C704 | List: |
| References | |
| B13-01503, B13-01503-R03-DRF, B13-1503, B13-1503-R3-DRF, NUDOCS 9209220371 | |
| Download: ML20105C720 (5) | |
Text
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R3 vision 1 September 1992 10 CFR 50,59 EVALUATION FOR CRD HOUSING SUPPORT CLEARANCE LA SALLE COUNTY STATION rrepared by: gd Azw
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K.K. serry l'
Reviewed by:
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H. Ioakam i
Vorified by:
MkA J.II.Fridayh 1
Approved by:
D.J. Robara l
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- wm s SATETY EUALUATICH TOR 10CrR$0.59 REV3EW CRD HOUSING BUPPORT CLEARANCE LA SALLN COUNTY BTATION 1.
fdULIICI This safety evaluation justifies a permanent plant modification of increasing the nominal clearanen between the lower surf ace of the control rod drive (CRD) flange capocrews and the CRD oupport structure (shoot-out steel) from 1 inch to 1.5 inches at ambient temperature.
The purpose of this r.odification is to facilitate under vessel maintenance work, thereby reducing radiation exposure to plant personnel.
This change will not affect the CRD housing, and will not adytreely a,ffect the capability of the support structura to perform its intended function to limit the downward motion of a control red following e postulated CRD housing failure.
II.
DISCUSNlp))
The proposed modificatien will allow increasing the nominal clearance between the lower surface of the CRD flange capocrews and the CRD support structura from 1 inch to 1.5 inchon at ambient temperature.
The implementation of this modification will require a change to UFSAR Section 4.6.1.2.
Specifically, the following assumptions are revised:
1.
The postulated CRD housing force is based on the operating pressure value of 1086 psig in place of the veneel design pressure of 1250 psig currently stated in the UTSAR.
This change is justified since this load condition event to most likely to occur under normal plant operation when the orives are being used and the maximum housing stress condition develops from a stuck rod scram.
Vessel design pressure occurs only during hydrotest before startup when there la no associated drive operation.
The application of the vessel operating pressure, combined with the CRD and blada weights, results in total force of 32,000 lba instead of the 35,000 lbs currently ataced in ti.e UFSAR.
It should be noted that the vessel operating preocure is the licensing basic for the UWR/6 CRD support design which uses the same hardware as LaSalle and has baan accepted by the NRC.. _,.. - _ - -. ~ ~I _ E M L:_r _ ^1__ _ _
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SAFETY EVALUA'810N TOR 10CFR50.59 REVIEW CRD HOUs!KO SUPPORT CLEARANCE LA SAf1E COUNTY STAT 20N 2.
The current UFGAR assumes an impact factor of 3 (with a total force of 105,000 lbe) to account for the 1 inch g p.
Due to the inernamed gap, the impact factor is revised to be 3.75, resulting in a total force of 120,000 lbs.
The capability of the support structure to limit the CRD motien to 6 inches has been evaluated in Reference 1.
It has baen demonstrated that the total deflection of an ejected CRD will be limited to 3.65 inches.
Therefore, even with the increase load caused by the higher clearance, the support structure will perform its intended function, and will limit the motion of an sjucted control rod drive to 6 inches.
Therefore, the proposed modification does not affect the conclusion of UPSAR Section 15.4.8 (spectrum of Rod Ejection Accidents).
Also, this modification does not affect any of the sequance of events and conclusions presented in UFSAR Sections 15.4.1 and 15.4.2 (Red withdrawal Errors), and 15.4.3 (Control Rod Hisoperatica) because these events do not result in CRD Gjection and their cause and/or F.itigation is not affected by the increased clearance.
The proposed modification does not impact any other design requirements sucn as equipment qualificntione, fire protection, seismic design, or reparation criteria.
The proposed modification requires a change to the Bases of the Technical Specifications, Reactivity control systems, Section B3/4.1.3 Control Rods.
UFSAR Sectians 4.6.1.2.3 (Page 4.6-17) and 4.6.2.3.1.2.1 (Page 4.6-19) will be revised to reficct the changes introduced by this modification, III E0.59 SArrTY EVAI,UATION a.
Ie tha probability of occurtfnee or the conaccuenaN of an accident or ralfunction of eeuirment i n ertant to safety previeuelv evaluated in the cafety nnelvoit renert increased?
No.
Tns CRD support structure is intended to mitigate the consequences of a potential Red Ejcetion accident (UTSAR Section 15.4.8).
The CRD support i
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M.E. CJ 'vi U:. ; JH 1 F.5 SAFETY EVALUATION FOR 10CFR50.59 REVIEW CRD BOUSINo EUFFO. T ("ZARANCE LA BALLE COUNTY STATION structure is not considered in the initiation of this event, therefore, the proposed modification does not increase its probability of occurrence.
The CRD support structure
!. 2 considered in the mitigation of a Red E4ction
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accident.
However, the proposed modification will result in a lower total force on the support structure from an ejected rod as discussed in section 21.1.
Therefore, the capability of the eupport structure to perform its intended function is not adversely affected, and the consequences of a postulated Rod Ejection event are not inersamed by the proposed modification.
b.
Is the concibility for an a_g e id e nt or malfunction of a diffaront tvoe then env evalunted oreviousiv in the safety engiveie recort created?
No.
The proposed modification does not result in any change in the design of the CRD system.
The increased clearance between the CRD flange capocrews and support structure will not initiate an-new malfunction of the CRD system, ard it will not prov t'
any of the CRD componente from performing its intended function.
UFSAR Section 15.4.8 states that the Rod Ejertion accident is not applicable to the BWR.
As discussed in item III.a above, the capability of the CRD support structure to perf o.cm its intended f.netien is not adversely affected by the increased clearance, therefore, the UFSAR conclusion remains
- valid, c.
In the marnin of safety an defined in the bania for any technietl gpgelfication reduced?
No.
Technical Specification 3.1.3.8 requires that the CRD support etructure be in place during Operational Conditions 1,
2, and 3.
This requirement is not a f t re c t e d by the proposed modification.
In addition, the proposed modification does not affect the capability of the CRD structure to parform its irat e n d e d function ao described in t5e Bases for Seccion 3/4.1.3 (Re4ctivity Control Syrtems).
However, the Bases do require an information change.
Technical Specification B3/4.1.3 currently stateu tho outward movement of a control rod will be restricted to less than 3 inches in tr.e event of a CRD housing failure.
This will be reworded to read that the housing support vill limit the outward movement of a control rod to 3.65,
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SAFETY EVALUATION FOR 10CPR50.S9 REVitW CRD HOUSING stTPPORT CS.IARANCE LA SAllE COUNTY STATION 1r.chas in the event cf a housing f allure.
The UYEAR transient and accid 6nt analyoce remain bounding.
Therefore, there is no reduction in the margin of safety as defined in the Technical specification Bason.
IV.
CONCtOSION Incroacing the clearance between the CRD housing flange capsarews and the suppor*. structure as described in Section I of this safety Evt.luation deem rot aftcet tha safe operation and shutdown capability of the Lasa114. 1&2.
Based on the above evaluation, this modification does not constitute an unreviewad safety question.
V.
Pf]KEfdLCES 1.
GE document 386HA243 (markedup) contained in DRF B13-01503.
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