ML20077G090

Responds to NRC 941201 RAI Resulting from Telcon Re Proposed TS Change Request 207,dtd 940729

ML20077G090
Person / Time
Site:	Beaver Valley
Issue date:	12/13/1994
From:	George Thomas DUQUESNE LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9412190173
Download: ML20077G090 (7)

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Beaver Va ley Power Station e Shippingport. PA 15077-0004 (412) 393-5200 -

(412) 643-8069 FAX GEORGE S THOMAS

$@,$,c",',"d'"' Deccaber 13, 1994 Nuclest Power DMaion U. S. Nuclear Regulatory Commission Attn: Document. Control Desk Washington, DC 20555

Subject:

Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 Response to Information Request Dated December 1, 1994 This letter provides the Duquesne Light Company (DLC) response to an NRC request for additional information resulting from.a conference call regarding proposed Technical Specification Change Request No.

207, submitted by letter dated July 29, 1994. During a conference call on- December 1, 1994, members of the NRC staff. requested clarification of information provided in WCAP-14122, " Beaver Valley-Unit. 1 Steam Generator Tube Plugging Criteria for Indications at Tube support Plates," along with a commitment to provide additional steam generator tube inspection data. Attachment A provides each item followed by.our response.

If you have any questions regarding the attached response, please contact Mr. Nelson Tonet,. Manager, Nuclear Safety Department, at (412) 393-5210.

Sincerely N/ wg George S. Thomas  ;

Attachment cc: Mr. L. W. Rossbach, Sr. Resident Inspector Mr. T. T. Martin, NRC Region I Administrator Mr. G. E. Edison, Sr. Project Manager l

1 9412190173 941213 PDR ADOCK 05000334 ,

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,' ATTACHMENT A Beaver Valley Power Station, Unit No. 1 Technical Specification Change Request 1A-207 Interim Plugging Criteria (IPC)

Response to Information Request Dated December 1, 1994 Item 1 All bobbin indications with voltages greater than 1.0 volt should be rotating pancake coil (RPC) inspected regardless of administrative plugging / repair. As written, the technical specification (TS) would not require performing RPC sampling of these indications. Previously approved IPC implementations have required all indications above the voltage threshold to be RPC inspected. Provide a commitment to conduct RPC inspections of indications with voltages greater than 1.0 volt.

Besponse 1 Consistent with the draft Generic Letter, Item 3.b.1, RPC inspections will be performed for all bobbin indications exceeding the RPC inspection threshold of 1.0 volt.

Item 2 Clarify the method for calculating main steamline break (MSLB) leakage considering the following guidance as evaluated against the TS statement regarding using the Electric Power Research Institute's (EPRI's) recommended voltage-leak rate (LR) correlation.

If the p-value test is invalid at the 5% level: zero slope with parametric uncertainty for both leak rate and probability of leakage (POL) functions (i.e., NUREG-1477 doesn't account for parametric uncertainty) - full Monte Carlo.

If the p-value test is valid at the 5% level: full Monte Carlo with parametric uncertainty (similar to methodology used in Braidwood 8/94 and Byron 10/94 safety evaluation reports).

Clarify references to the EPRI leak rate correlation (i.e., a linear regression fit --or-- the EPRI leak rate methodology (pg. 8-7, pg. B-3 of submittal) --or-- EPRI leak rate database with corresponding linear regression fit --or- ...).

Ennnonse 2 The following analysis methods will be used for calculating MSLB leakage:

a) If the p-value test is invalid at the 5% level: A full Monte Carlo analysis with parametric uncertainty included for both the leak rate and POL functions will be applied with a zero slope leak rate correlation. Consistent with EPRI and Westinghouse A-1

'Attcch;cnt A, continu$d Response to Information Request Dated December 1, 1994 Page 2 Response 2 (continued) comments on the draft Generic Letter, it is proposed to use only leak rate data with voltages less than the structural limit (9.6 volts in draft Generic Letter) to define the zero slope leak rate correlation. For an interim plugging criteria repair limit, the structural limit is a much higher voltage than expected for any end of cycle (EOC) value at B( er Valley Unit 1.

b) If the p-value test is valid at th 5% level: A full Monte Carlo analysis with a parametric uncerti.uty similar to that described in the Braidwood-1 8/94 safety e luation report (SER) will be utilized.

c) Application of the EPRI leak rate correlation is meant to imply use of a linear regression fit to the EPRI leak rate database obtained using the EPRI data exclusion criteria as agreed upon by the NRC. The EPRI leak rate database, as described in Beaver Valley Unit 1 WCAP-14122, is the latest data for 7/8 inch diameter tubing.

Item 3 The database actually used to calculate the MSLB leakage and probability of burst should be that delineated in NRC SERs.

Responne 3 The Beaver Valley Unit 1 submittal provided example MSLB leakage and burst probability calculations which utilized the EPRI database and the accompanying EPRI outlier exclusion criteria. The large' margins demonstrated for the projected MSLB leakage and burst probability in the example calculations support the recommendation to utilize the EPRI database for the Beaver Valley Unit 1 IPC. However, if the NRC review of the EPRI outlier exclusion criteria cannot be completed in a time frame that will support approval of the Beaver Valley Unit 1 application by early January 1995, the database utilized to calculate leakage and burst probability will be that delineated in the NRC SERs.

11RM_i Provide a commitment to submit histograms and supporting information following the inspections (i.e., growth rates, voltage. distributions, and non-destructive examination (NDE) uncertainty distributions,

...). Other information (i.e.,

IPC amendments had commitments to supply this 90 days after restart). These distributions are necessary to calculate the MSLB leakage and the probability of burst.

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' Attcchnent A, continu:d Response to Information Request Dated December 1, 1994 Page 3, Egmoonse 4 Reporting of MSLB leak rates, burst probabilities and supporting data will be provided, within 90 days after restart, consistent with the information requested in the draft Generic Letter.

ItD!L_S.

Six tube pulls at support plate intersections occurred in 1991 but only five were examined. If the sixth intersection is archived, provide examination results within 90 days of restart from the tenth refueling outage. It is suggested that six additional intersections be removed prior to restart from the eleventh refueling outage.

Resnonno 5 Additional tube pulls are currently not planned for the tenth refueling outage. (1R10) or the eleventh refueling outage (1R11).

However, an archive tube nupport plate (TSP) intersection sample (Tube R11C48, TSP 2) from the tube pulls performed at the eighth refueling outage is available for metallographic analysis and burst testing. The results of these analyses will be made available to the NRC within 90 days of restart from 1R10.

For future outages, it is expected that the NRC review of the industry tube pull program will be completed and an NRC endorsed industry program will be available. Beaver Valley will apply the requirements of the NRC endorsed industry program at future outages when implementing IPC repair limits.

Item 6 Does the burst probability calculation include parametric uncertainty? Discuss burst criteria of 1.0E-2 versus 2.5E-2. Will the probability of burst calculation be submitted to the NRC prior to restart (similar to Cook IPC)?

Response 6 The burst probability analysis will be performed by Monte Carlo analyses including parametric uncertainty. The draft Generic Letter has identified a burst probability criteria of 1.0E-2 while industry comments on the draft Generic Letter have recommended a higher acceptance level. In support of the industry comment on the draft Generic Letter regarding the acceptance level of burst probability, the Beaver Valley submittal recommends an acceptance level consistent with that in NUREG-0844. As noted in the response to Question 4, the reporting requirements of the draft Generic Letter will be satisfied, which requires reporting of the burst probability prior to restart if the acceptance limit is exceeded. If specifically requested by the NRC, the probability of burst can be provided prior to restart, even if the acceptance criteria is satisfied.

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Attachm2nt A, continued Response to Information Request Dated December 1, 1994 Page 4.

Item 7 Use of smaller / larger diameter probes requires that they can be demonstrated to be equivalent on a statistically significant basis for detection and sizing of outer diameter stress cori)sion cracking t (ODSCC) indications (pg. 2-4 versus pg. A-2). If the probes are not qualified, will tubes be repaired per TS?

Response 7 It is expected that the 0.720 inch diameter probe will be used for inspection of all TSP intersections. If an alternate probe size is found to be required, appropriate performance demonstration test results will be provided.

Item 8 other IPC amendments required all tubes with dents greater than 5.0 I volts to be RPC inspected (pg. 2-4 and pg. B-3). Will indications I found at these dented intersections be repaired per the TS?

ResponUS_R ,

I TSP intersections with dents greater than 5.0 volts will be RPC l inspected and any flaw indications found by the RPC inspection will be repaired.

Item 9

Clarify plans with respect to RPC inspecting dents less than 5.0 volts to ensure primary water stress corrosion cracking (PWSCC) is not occurring. Do the guidelines / training instruct the analysts to look for this? Report to the NRC prior to restart if indications of PWSCC at the TSPs are found? See Byron IPC amendment.

Ennponso 9 1

l Bobbin indications greater than 1.0 volt found at dents less than 5.0 volte will be RPC inspected. The RPC phase angles will be evaluated for inside diameter (ID) or outside diameter (OD) indications. If ID indications are found, the results will be reported to the NRC prior to restart. Eddy current (EC) analysts will be instructed to evaluate the data for ID indications, i

lic3L10.

Clarify how the lowest TSP level on the cold leg side where ODSCC is occurring will be determined. See draft Generic Letter.

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. i Attcchm:nt A, continund Response to Information Request Dated December 1, 1994 Page 5 Enunnnae 10 The planned inspection scope for 1R10 is bobbin coil eddy current examination of all active tubes in each steam generator, tube-end to tube-end. Thus, the lowest cold leg TSP level potentially experiencing ODSCC will be identified.

Item _11 Clarify whether copper has been observed at the TSP intersections (pg. 3-2 of WCAP indicates it is there, pg. A-13 indicates it isn't) and the implications if it exists (i.e., RPC inspection).

Enannnso 11 It would require copper plating on the tube in order to have a significant influence on the bobbin inspection results. The Beaver Valley Unit 1 pulled tubou (WCAP, pg. 3-1) were found to have minute particles of metallic copper in the deposits at the TSP locations.

This type of deposit is typical of that found on most pulled tubes for plants that have operated with copper in the secondary system and has negligible influence on the eddy current response. This is consistent with pg. A-13 which notes that no plated copper was found on the tube OD. It should be noted that the only source of copper in the secondary system was the moisture separator reheater tube bundles (90-10 Cu/Ni) which have been replaced with 439 stainless steel bundles.

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l Clarify intentions with respect to reporting indications of l circumferential cracking and indications outside the TSPs. Compare l pg. 2-4 versus pg. 8-3 regarding reporting ID versus OD l circumferential indications.

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E931ps1159_.11 The reporting of circumferential cracks, if found, will include both l ID and OD indications at TSP intersections although only OD would be  !

potentially expected at dented TSP intersections. The reporting statement on pg. 2-4 is correct while the CD reporting on pg. 8-3 is misplaced.

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. . . # 6*.Attachasnt A,. continued

_ Response to-Information Request Dated Decemberfl,.1994-

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-Jtem 15' Clarify intentions with' respect to repairing all known leaking' tubes prior.to restart.

Ensoonse 11 It is - our . intention to repair all known leaking tubes prior to restart from 1R10 regardless of acceptability per IPC..

Item 16 DELETED Item 17 DELETED

1. tem 18 The RPC standard specified in Appendix A at Beaver- Valley is different from' that used at other IPC . plants. What. is the significance? Does this limit comparisons to other IPC plants?

BesR9nse_13.

The RPC' standard simulated flaw required for comparisons with other plants is the 0.5" long, 100% through. wall electric discharge machining (EDM) . notch. ' This standard notch is.used for the voltage normalization' for IPC applications. The remaining notches are recommended- on. the standard to facilitate normalization and interpretation of RPC data for other types of potential defects than ODSCC at TSPs.

Item 19 DELETED Item 20 DELETED l j- Item 21 DELETED Itcu 21 DELETED Ittta_21 Provido effective full power years (EFPY) for Cycle 10 and Cycle 11. )

l Response 23 b I l

' Projected Burnups: EOC 10 10.82 EFPY EOC 11 11.77 EFPY A-6

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