ML20207A732

Submits Record of 990429 Telcon with Union Electric Personnel Re Electrosleeve Amend Application for Callaway Plant,Unit 1.Info Provided by Ue Included in Attachments 1 & 2.List of Personnel That Participated in Telcon Encl

ML20207A732
Person / Time
Site:	Callaway
Issue date:	05/20/1999
From:	Mel Gray NRC (Affiliation Not Assigned)
To:	NRC (Affiliation Not Assigned)
Shared Package
ML20207A737	List: ML20207A732 ML20207A740
References
TAC-MA3954, NUDOCS 9905270237
Download: ML20207A732 (4)

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[ -4 UNITED STATES j j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20056-0001

.....p8 May 20,1999 MEMORANDUM TO: Docket File FROM: Mel Gray, Project Manager, Section 2 Project Directorate IV & Decommissioning d Division of Licensing Project Management Office of Nuclear Reactor Regulation

SUBJECT:

RECORD OF TELECON WITH UNION ELECTRIC PERSONNEL

- REGARDING ELECTROSLEEVE AMENDMENT APPLICATION FOR CALLAWAY PLANT, UNIT 1 (TAC NO. MA3954)

REFERENCE:

License Amendment Application, UE Letter ULNRC-03910, dated October 27,1998 The NRC staff is reviewing an amendment application submitted by Union Electric Company (UE) that requests approval to install the electrosteeve repair in Callaway Plant, Unit 1 steam generator tubes (Reference). The electrosleeve repair method has been developed by Framatome Technologies, Incorporated. On April 29,1999, NRC staff and UE personnel discussed risk information provided by UE The information provided by UE is included in Attachments 1 and 2. Personnel that participated in the telecon are listed in Attachment 3.

In Attachment 2, UE concluded that the additional conservatisms listed would decrease the calculated core damage frequency for induced steam generator tube ruptures to the low 10E4 range. The staff indicated that while the conservatisms listed seemed reasonable, there were

, non-conservatisms that may not have been considered. An example discussed was the turbine driven auxiliary feedwater pump failure to run probability. The probability used by UE was on the order of 10Ed and considered low by the staff. In nuclear plant individual performance assessments (IPEs), this probability ranges over several orders of magnitude. The staff also

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indicated that they were not sure all appropriate cutsets had been included in calculating the core damage frequency for "high dry" severe accident scenarios (high primary to secondary differential pressure and dry secondary side steam generator). The staff stated that a more l in-depth staff review of the Callaway IPE would be required to provide a basis for NRC approval of the electrosleeve amendment without a flaw length limitation.

/(M UE personnel brought item #5 in Attachment 2 to the staff's attention. With the conservatisms presented, the UE calculated core damage frequency leading to steam generator tube rupture I (SGTR) would be 1.70Ed/ year. UE indicated that only those core damage scenarios that fail electrosleeves (i.e, those severe accident scenarios that result in temperatures between 1100*F and 1400*F), should be considered in calculating the increase in risk. Using the MAAP i code, UE indicated that for dominant sequences, tube temperatures remain below 1100F.

Consequently, UE concluded the conditional probability of core damage and SGTR due to electrosleeve installation would be essentially zero. The staff indicated that to quantify the increase in core damage frequency followed by SGTR due to electrosleeve installation, the time ran 2 C J ' 4 :1 9905270237 990520 f ADOCK 05000483 PDR P PDR [

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4 temperature history of the severe accident needs to be considered, not temperature alone.

Additionally, considering differences in MAAP code and RELAP code results for other plants, this approach may not be bounding. Agreement was not reached on this issue.

. in conclusion, UE indicated that they did not consider the staff's evaluation of risk for the

- electrosleeve amendment to provide sufficient basis for proposing additional limitations on the electrosleeve amendment request. Altematively, the staff indicated the risk information provided by UE would require significant additional staff review before UE's conclusions regarding high-dry core damage frequency and SGTR probability due to electrosleeve installation could be accepted as the basis for approval of the electrosleeve amendment

, request.-

Docket No. 50-483 l Attachments: 1. Fax from UE on April 20,1999, Draft of " Evaluation of Risk induced Steam Generator Tube Rupture," March 1999

2. Fax from UE on April 27,1999, " Issues Related to Qualification of Delta-LERF Due to Installation of Electrosleeves"

3. List of Telecon Participants DISTRIBUTION: original ' signed by M. Gray j Docket File l PUBLIC i PlV-2 Reading RBarrett SRichards

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MGray BBateman TSullivan - 1 EPeyton SLong-GParry OGC' ACRS DGraves. Region IV 2 l OFFICE PDIV-2/PM , PDIV-2/LA SPSB i PDIV-2/SC ,,

lNAME NU EP dab RBh SDembe M hDATE d / /99 6/11/99 [/f199 T66/9 OFFICIAL RECORD COPY l DOCUMENT NAME: MEM3954.WPD .  !

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,y temperature history of the severe accident needs to be considered, not temperature alone.

Additionally, considering differences in MAAP code and RELAP code results for other plants, this approach may not be bounding. Agreement ws: not reached on this issue.

In conclusion, UE indicated that they did not consider the staffs evaluation of risk for the electrosleeve amendment to provide sufficient basis for proposing additional limitations on the electrosleeve amendment request. Altematively, the staff indicated the risk information provided by UE would require significant additional staff review before UE's conclusions ,

regarding high-dry core damage frequency and SGTR probability due to electrosleeve '

installation could be accepted as the basis for approval of the electrosleeve amendment request.

Docket No. 50-483 Attachments: 1. Fax from UE on April 20,1999, Draft of " Evaluation of Risk Induced Steam l Generator Tube Rupture," March 1999

2. Fax from UE on April 27,1999, " Issues Related to Qualification of Delta-LERF Due to Installation of Electrosleeves"

3. List of Telecon Participants l

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's Fax from Union Electric Company on April 20,1999 Draft of" Evaluation of Risk induced Steam Generator Tube Rupture,"

dated March 1999 i

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i ATTACHMENT 1