ML20072U248

Supplemental Application for Amends to Licenses NPF-37 & NPF-66,revising TS for Consistency W/Draft GL, Voltage- Based Repair Criteria for Repair of Westinghouse SG Tubes Affected by Outside Diameter Stress Corrosion Cracking

ML20072U248
Person / Time
Site:	Byron
Issue date:	09/07/1994
From:	Bauer J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20072U252	List: ML20072U248 ML20072U256
References
NUDOCS 9409160183
Download: ML20072U248 (17)

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Comm::nw3rith Edison 1400 Opus Place l

1 O Downers Grove, Illinois 60515 l

l September 7,1994 .

Document Control Desk ,

U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Mr. William T. Russell, Director

Subject:

SupplementalInformation Regarding Application for Amendment to Facility Operating License:

Byron Station Units 1 and 2

! (NPF-37/66; NRC Docket Nos. 50-454/455)

" Steam Generator Interim Plugging Criteria"

References:

1. Draft Generic Letter, " Voltage-Based Repair Criteria for the Repair of Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracking," August 12,1994.  !

l 2. Letter from J. A. Bauer to W. T. Russell transmitting Byron l Station's request for a license amendment to implement an Interim i

Plugging Criteria, dated August 1,1994.

Dear Mr. Russell:

In Reference 2, Byron Station committed to provide resolution of any discrepancies or differences found between the draft Generic Letter (Reference 1) and the proposed interim plugging criteria (IPC) license amendment (Reference 2). A comparison with the draft Generic Letter (GL) has been conducted. The majority of the requirements identified in the draft GL have been met in the Byron submittal, however, some differences were noted. The differences and their dispositions are delineated in Attachment 1.

l In summary, Byron Station will meet the requirements of the draft GL for the upcoming i Refueling Outage (B1R06) and subsequent Operating Cycle (Cycle 7) with the exceptions noted in Attachment 1 (Items 7,11,12, and 13). Revisions to the affected Technical Specification pages/ inserts have been made to ensure consistency with the Model Technical Specifications in the draft GL, and to incorporate items 8,18, and 21 from Attachment 1. These changes are included in Attachment 2.

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I W. T. Russeil September 7,1994 It is worthy to note that a number of issues addressed in the GL have not been fully resolved within the nuclear industry or NRC Staff at this time. Byron Station will meet the draft GL requirements (except as noted in Attachment 1) for B1R06, however, anticipates requesting future changes in accordance with the final approved Generic Letter.

During the NRC's review of the subject submittal, a format error was discovered on an affected Technical Specification page. The numbering for the new reporting criteria was inconsistent with that previously established in the Technical Specifications. The corrected insert F to Attachment E of Reference 2 is included in Attachment 2 to this letter.

The No Significant Hazards Consideration (Attachment F to Reference 2) has been revised to address the unscheduled mid-cycle steam generator inspection acceptance criteria as specified in the draft GL. The revised document is included in Attachment 2 to this letter.

l This supplemental request for a Technical Specification Amendment has been reviewed and approved by Onsite and Offsite review in accordance with Byron procedures.

Pursuant to 10CFR50.91(b)(1) a copy of this request has been forwarded to the designated State of Illinois Official.

To the best of my knowledge and belief, the statements contained in this document are true and correct. In some respects these statements are not based on my

personal knowledge, but on information furnished by other Comed employees, contractor employees, and/or consultants. Such information has been reviewed in accordance with company practice, and I believe it to be reliable.

Please address any comments or questions regarding this matter te inis office.

l Respectfully, f nef k omN

( Joseph A. Bauer Nuclear Licensing Administrator Attachments cc: G. F. Dick, Byron Project Manager - NRR H. Peterson, Senior Resident Inspector - Byron i

J. B. Martin, Regional Administrator - Region Ill Office of Nuclear Facility Safety - IDNS F "^"""""^"^^""""'%

l OFFICIAL SEAL 1; 4l MARYELLEN D LONG 3

. . NOT AftY PUBLIC. S1 ATE OF ILLINO68 l

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ATTACHMENT 1 COMPARISON BETWEEN DRAFT GENERIC LETTER AND BYRON IPC SUBMITTAL i

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Differences Between Draft Generic Letter and Original Byron IPC Submittal

1. Draf t GL Summary of Draft GL Requirements Summary of Byron Submittal Disposition Section(s) 1 1.b.2, 1.b.3, Tubes with dents > 5.0 volts and Tubes with dents > 5.0 volts and Byron will meet this requirement. Affected 3.b.2, 3.b.4, with large mixed residuals are with large mixed residuals are tubes with RPC flaw indications will be and 3.b.5 excluded from IPC requirements, required to be inspected by RPC repaired.

should be RPC inspected, and any indications should result in tube repair 2 1.b.4 Repair criteria do not apply to flow Not specifically addressed. Byron will meet this requirement. IPC distribution baffle plate intersections. criteria will not be applied to baffle plate intersections since Byron does not consider the flow distribution baffle to be a tube support plate.

3 2. Burst probability criteria limit is Burst probability criteria limit is Byron will meet this requirement for B1R06 1.0 x 10 2 2.5 x 10 by applying a burst probability limit of 1.0 x 10 .

4 2.a.1 and Certain leak / burst data exclusions Database is consistent with the EPRI Byron will meet this requirement for B1R06 2.b.3(2) should not be taken and the VC database for 3/4" tubing and is by performing the leak / burst calculation Summer data point should have a identical to the database used in using both the EPRI database and the MSLB leakrate of 2476 I/hr, pending support of the Braidwood submittal database consistent with the draft GL.

NRC review. Leakage results based on the most conservative calculation will be used to determine that the leakage limit is met for BIR06.

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S 2.b.2(2) Growth rates are to be taken from the Submittal method requires growth Byron will meet this requirement for B1R06.

most limiting of the last 2 inspections rates to be taken from the previous This is the first inspection to employ IPC if both employed IPC guidelines or operating cycle. Negative growth guidelines, therefore, submittal methodology from the current inspection if it is the rnes are not specifically addressed. is consistent with the draft GL requirement.

first to employ IPC guidelines. Negative growth rates will be treated as Negative growth rates should be (' zero growth rates in assumed growth included as zero growth rates in the distribution.

assumed growth distribution.

6 2.b.4 Calculate Offsite and Control Room The MSLB leakrate limit is Byron will ensure the Offsite Dose meets Doses every cycle based on calculated established based on current iodine 10CFR100 requirements by establishing an MSLB leakrate and reduce iodine limits limits and 10CFR100 requirements. EOC MSLB leakrate limit based on existing to meet 10CFR100 requirements Control Room doses are not iodine limits that is consistent with specifically addressed. 10CFR100 requirements. Byron is reviewing the existing Control Room dose analyses to determine if dose due to a MSLB is bounded by another analysis. If Control Room Dose is mere limiting, EOC MSLB leakrate limit will be based on Control Room Dose.

7 3. Inspection Criteria should be Byron /Braidwood inspection Byron has already ordered new calibration consistent with the VC Summer guidelines were included with the standards consistent with the Catawba and Appendix A guidelines. Byron submittal. These guidelines EPRI IPC guidelines. Therefore, Byron will are consistent with the Catawba use the inspection guidelines as submitted WCAP-13854 Appendix A for BIR06.

guidelines, the EPRI APC guidelines, and the Braidwood IPC SER.

8 3.a.1 and inspection scope is to be 100% of hot Scope requires 100% of hot leg Byron will meet this requirement. During Model TS leg tubes and a 20% random sample tube support plate intersections and B1R06, Byron is performing 100% full 4.4.5.2.d of cold leg tubes. all CL intersections down to the length inspection to accommodate lowest intersection with ODSCC. inspections using dual guide tubes. The revised Technical Specification page markup to incorporate the draft GL requirement is included in Attachment 2.

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9 3.b.1 All indications greater than the 1.0 Submittal specifically identifies Byron will meet this require ~ ment for BIR06.

volt limit subject to RPC inspection indications between 1.0 and 2.7 All bobbin coil indications greater than 1.0 volts as subject to RPC. Guidelines volt will be subject to RPC inspection.

identify all indications greater than 1.0 voit subject to RPC.

10 3.b.2 and Tubes with copper deposits at Copper is not found in the Does not apply to Byron.

3.b.3 intersections should be RPC inspected secondary at Byron.

and any indications detected should result in tube repair 11 3.c.2 Bobbin coil calibration is to be setup Bobbin coil calibration is to 4-20% Byron will defer implementation of this on 4-100% through-wall (TW) holes. TW holes consistent with the requirement pending resolution of industry Catawba Appendix A guidelines. comments. Converting to 4-100% TW The Byron calibration standards are holes would result in a loss of comparison normalized to a laboratory standard. basis to the industry and, specifically, to other Comed plants.

12 3.c.3 New probe variability to be within +/- Not specifically addressed. Byron will defer implementation of this 10%. requirement pending resolution of industry comments.

13 3.c.4 All tubes inspected since the last if the probe wear exceeds the 15% Byron will implement the method described successful probe wear check shall be wear limit by x%, then indications in the Byron submittal and inspection reinspected with a new probe. measured since the last successful guidelines included with the submittal probe wear check that are within pending resolution of industry comments.

x% of the repair limit must be reinspected with a new orobe.

14 3.c.6 Quantitative noise criteria is to be Not specifically addressed. Byron will employ quantitative noise criteria employed in the inspection guidelines. during BIR06.

15 3.c.8 Smaller diameter probes are Application of IPC is limited to tubes Byron will meet this requirement. Only acceptable if demonstrated to be inspected with a 0.610" diameter larger probes will be used until the smaller statistically equivaient to larger probes probe (larger probes only). diameter probes have been demonstrated for detection and response equivalent to the larger probes.

capabilities.

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16 4.a Six intersections of tubes should be Exact number of tubes and Byron will meet this requirement. For pulled every other outage or intersections are not specified for BIR06, Byron is currently planning to participate in an industry tube pull BIR06. Tubes selected will be remove 3 tubes each with 3 support plate database. based on indication size and intersections and a flow distribution baffle.

voltage. A Comed tube pull Tube selection will be consistent with the program is being developed. industry tube pull program. Byron plans to .

participate in the industry tube pull program.

17 5.c Tubes with known leaks must be Not specifically addressed. Byron will meet this requirement. All known repaired prior to returning SGs to leaking tubes will be repaired.

service.

18 6.a and Model Reporting required prior to startup for Report required prior to startup for Byron will meet this requirement.

TS 4.4.5.5.d the following: the following: The revised Technical Specification page

1. Previous cycle MSLB leak rate 1. An indication of greater than markup to incorporate the draft GL exceeds the si*e leak limit. 4.54 volts is found, or requirement is included in Attachment 2.

2. Any unusualinspection results are 2. The projected EOC MSLB leakage found. limit is exceeded.

3. Projected EOC burst probability is greater than the limit.

19 6.b(a) The results of metallurgical Tube pull results to be submitted Byron will use best efforts to meet the 90 examinations of tubes removed are to following restart. Specific time day requirement. Depending on extent of be reported within 90 days following period is not addressed. results expected to be submitted,90 days restart. may not allow sufficient time to obtain results and generate the report.

20 6.b(b) and Report required 90 days after startup Report required 90 days after Byron will provide sufficient information for Model TS to include detailed information on completion of inspection which tube integrity evaluation 90 days after 4.4.5.5.d growth rates, voltage distributions, includes applicable tubes, location startup. Note that all the requested leak / burst evaluations, and NDE and extent of degradation, and information may not be available within the uncertainty distributions. projected EOC MSLB leakage. 90 day period.

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21 Model TS Voltage acceptance criteria for an Submittal does not address alternate Byron willincorporate the revised ,

4.4.5.4.a.10 unplanned inspection may be greater acceptance criteria for an unplanned requirement for BIR06. The revised than 1.0 volt based on equation inspection. Technical Specification page markup to supplied in the draft GL. incorporate the draft GL requirement is included in Attachment 2.

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i ATTACHMENT 2 I

i REVISIONS TO ORIGINAL BYRON IPC SUBMITTAL 4 l 4

i j - Revised Attachment A, Detailed Descrlption l - Revised Attachment E, Technical Specification I, Markups (both " Redline" and " Clean" formats) l - Revised Attachment F, No Significant Hazards Review i

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l ATTACHMENT A  !

DESCRIPTION AND SAFETY ANALYSIS OF PROPOSED CHANGES TO APPENDIX A TECHNICAL SPECIFICATIONS OF FACILITY OPERATING LICENSES NPF-37 AND NPF-66 l

DESCRIPTION OF THE PROPOSED CHANGE Commonwealth Edison Company (Comed) proposes to amend the following l Technical Specification: j Specification 3/4.4.5 REACTOR COOLANT SYSTEM - STEAM GENERATORS l

i This proposed license amendment request will modify Specification 3/4.4.5 to )

allow an eddy current bobbin coil probe voltage-based steam generator (SG) tube l support plate (TSP) interim plugging criteria (IPC) to be applied for Byron Unit 1 l beginning with Cycle 7. i Technical Specification Bases Section 3/4.4.5, STEAM GENERATORS, will also be  !

modified to reflect these changes. l DESCRIPTION OF THE CURRENT REQUIREMENT Specification 3/4.4.5 The Technical Specification Surveillance Requirements (TSSRs) associated with Specification 3.4.5 currently require that any SG tube with an imperfection depth at or exceeding the plugging or repeir limit of 40% of the nominal wall thickness be '

removed from service by plugging or repaired by sleeving in the affected area. I A-1

i BASES OF THE CURRENT REQUIREMENT l Specification 3/4.4.5 The TSSRs for inspection of the SG tubes ensure that the structural integrity of this portion of the RCS will be maintained. The program for inservice inspection of SG tubes is based on a modification of Regulatory Guide (RG) 1.83, " Inservice inspection of PWR Steam Generator Tubes," Revision 1, July 1975. Inservice inspection of SG tubing is essential in order to maintain surveillance of the condition of the tubes in the event that there is evidence of mechanical damage or progressive degradation due to design, manufacturing errors, or inservice conditions that lead to corrosion. Inservice inspection of SG tubing also provides a i means of characterizing the nature and cause of any tube degradation so that corrective measures can be taken.

1 NEED FOR REVISION OF THE REQUIREMENT

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i At both Byron and Braidwood, Unit 1 has four Westinghouse Model D-4 SGs and i Unit 2 has four Westinghouse Model D-5 SGs. The significant differences between l the SG models are in the tube material and tube support materials and design. The  !

D-4s have 0.75" thick carbon steel tube support plates with drilled hole tube supports. The D-5s have 1.125" thick stainless steel support plates with I Quatrefoil tube supports. The D-4 SG tubes are mill annealed Inconel 600 which were hard rolled into the tubesheet during initial assembly. Subsequently, the D-4 tubes were shot peened in the tubesheet area and stress relieved in the U-bend area. The D-5 tubes are heat treated Inconel 600 which were hydraulically  ;

expanded into the tube sheet during initial assembly. Over the past several l

, refueling outages, the number of SG tubr;s plugged per outage has been increasing.

) At each site, Unit 1 has had more defcetive tubes than Unit 2 primarily due to the design differences between the D 4 and D-5 SGs as mentioned above.

i In the most recent Byron UnM 1 Refueling Outage (B1R05), conducted in the spring of 1993, a SG tube inservlce inspection was performed in accordance with the

] current TSSR 4.4.5.0. The results of this inspection identified a total of 1105 bobbin coilindications at the tube support plate locations. Using a rotating pancake coil to confirm these indications, 556 indications were flawed due to ODSCC at the TSPs in 530 SG tubes. The 530 tubes were removed from service by plugging. This increased the overall plugging total for Byron Unit 1 to 847 tubes or 4.6% of the tubes. Of the 847 tubes plugged to date, 671 were plugged due to ODSCC at the tube support plate locations.

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i For the upcoming Byron Unit 1 Refueling Outage (B1R06), predictions on the number of pluggable indications using the current TSSR 4.4.5 acceptance criteria 4 are approximately 1950 tubes. With the approval to use the Interim Plugging i

Criteria proposed, the predicted number of tubes requiring removal from service by

) plugging or repair by sleeving would be reduced to 600. l l

i DESCRIPTION OF THE REQUESTED REVISION l l

The changes proposed in the amendment are contained in six inserts to the l surveillance requirements for the Byron Technical Specifications and Bases. The j inserts are applicable to Unit 1 but not Unit 2. The inserts reflect the option to allow tubes to remain in service using a voltage-based IPC for ODSCC indications in the tube support plate region. Using IPC also results in changes to the sample i selection, inspection criteria, and reporting requirements. A nt.w term, " Tube l Support Plate interim Plugging Criteria Limit", is defined to identify the acceptance criteria to be used during the SG inservice inspections to allow a tube to remain in l service. Clarifications are made to existing definitions to reference IPC, as appropriate.

Soecification 4.4.5.2. Steam Generator Tube Samole Selection and Inspection Changes to this section of the surveillance requirements will require that all tubes remaining in servMe due to application of IPC shall be included as part of the tubes to be inspecteJ os an addition to the sample selection made in accordance with existing criteria. Also, the surveillance requirements will specify how IPC will be implemented.

Insert "A" adds a section to Specification 4.4.5.2.b, requiring all tubes in which the tube support plate IPC plugging limit is applied be inspected in each scheduled {

refueling outage. Insert "A" reads as follows:

"For Unit 1, tubes left in service as a result of application of the tube support plate plugging criteria shall be inspected by bobbin coil probe during ,

all future outages." l l

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s insert "B" adds section 4.4.5.2.d to describe the inspections associated with the

implementation of IPC. Insert "B" reads as follows

"For Unit 1, implementation of the tube support plate interim plugging criteria limit requires a 100% bobbin coil probe inspection for all hot leg tube support plate intersections and all cold leg intersections down to the lowest cold leg tube support plate with outer diameter stress corrosion cracking )

(ODSCC) indications. The determination of tube support plate intersections having.ODSCC indications shall be based on the performance of at least a ,

i 20% random sampling of tubes inspected over their full length." l l

Soecification 4.4.5.4. Acceptance Criteria l l

Insert "C" adds to the definition of " Plugging or Repir Limit", Specification 4.4.5.4.a.6, to ide%iy that this definition does not apply for Unit 1 in the region of the tube subject to the TSP IPC limit, i.e. the TSP intersections, and that Specification 4.4.5.4.a.11 describes the repair limit for use within the TSP intersection of the tube. Insert "C" reads as follows:

"For Unit 1, this definition does not apply to tube support plate intersections

. for which the voltage-based plugging criteria are being applied. Refer to 4.4.5.4.a.11 for the repair limit applicable to these intersections;"

l Insert "E" adds Specification 4.4.5.4.a.11 to define the TSP IPC limit. Insert "E" reads as follows:

"11) The Tube Sucoort Plate Interim Pluooino Criteria limit is used fr r the disposition of a steam generator tube for continued servics that is

experiencing outer diameter sVess corrosion cracking confined within the thickness of the tube support plates. At tube support plate intersections, the repair limit is based on maintaining steam generator tube serviceability as described below

i a) Degradation attributed to outside diameter stress corrosion cracking within the bounds of the tube support plate with bobbin voltage less than or equal to 1.0 volt will be allowed to remain in service.

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b) Degradation attributed to outside diameter stress corrosion cracking l within the bounds of the tube support plate with bobbin voltage greater than 1.0 volt will be repaired or plugged except as noted in 4.4.5.4.a.11)c) below.

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l l 1 c) Indications of potential degradation attributed to outside diameter stress ' corrosion cracking within the bounds of the tube support plate with a tobbin voltage greater than 1.0 volt but less than or equal to ,

2.7 volt! may remain in s.arvice if a rotating pancake coil inspection j does not detect degradation. Indications of outside diameter stress 1 corrosion cracking degradation with bobbin voltage greater than 2.7 wits will be plugged or repaired. l

'I d) Certain intersections as identified in WCAP-14046,'Section 4.7, will i be excluded from application.of the voltage-based repair criteria as it is determined that these intersections may collapse or deform j following a postulated LOCA+SSE event.  :

e) If, as a result of leakage due to a mechanism other than ODSCC at the tube support plate intersection, or some other cause, an . ,

unscheduled mid-cycle inspection is performed, the following repair .

criteria apply instead of 4.4.5.4.11)c). If bobbin voltage is within expected limits, the indication can remain in service. The expected bobbin voltage limits are determined from the following equation:

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V = measured voltage Vooc . = voltage at BOC At = time period of operation to unscheduled outage CL = cycle length (full operating cycle length where operating cycle is the time between two scheduled steam generator inspections)

Va = 4.5 volts l

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Soecification 4.4.5.5. Reoc rs i insert "F" adds reporting requirement 4.4.5.5.d to identify the reports, including content and time period, to be submitted to the Commission associated with the implementation of IPC. Insert "F" reads as follows:

"d. For Unit 1, implementation of the voltage-based repair criteria to tube suppon plate intersections, reports to the Staff shall be made as follows:

1) Notify the Staff prior to returning the steam generators to l service should any of the following conditions arise:

a) If estimated leakage based on the actual measured end-of-cycle voltage distribution would have exceeded the l leak limit (for postulated main steam line break utilizing l licensing basis assumptions) during the previous operation cycle.

b) If circumferential crack-like indications are detected at the tube support plate intersections.

l c) If indications are identified that extend beyond the  ;

confines of the tube support plate.

d) If the calculated conditional burst probability exceeds 1 x 10 2, notify the NRC and provide an assessment of the safety significance of the occurrence. .

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2) The final results of the inspection and the tube integrity l evaluation shall be reported to the Staff pursuant to Specification 6.9.2 within 90 days following restart."

Bases 3/4.4.5. Steam Generators Insert "G" adds a discussion to the Bases section of Technical Specifications to l

! refer to the dispositioning of tubes in accordance with IPC. Also, a discussion of l

adjustment of the operating period to meet projected MSLB leakage limitations is included. Insert "G" reads as follows:

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For Unit 1, tubes experiencing outer diameter stress corrosion cracking within the thickness of the tube support plates will be dispositioned  !

in accordance with Specification 4.4.5.4.a.11. The operating period may be i adjusted to less than the full operating cycle to meet the 12.8 gpm projected ,

leakage limit. The maximum site allowable primary-to-secondary leakage ,

limit,12.8 gpm, includes the accident leakage from a faulted steam generator and the operational leakage of the three remaining intact steam generators equal to the Specification 3.4.6.2.c leakage limit."

The specific changes to these Technical Specifications and associated bases are included in Attachment E.

BASES FOR THE REVISED REQUIREMENT Byron is requesting this revision based on the following considerations:

The August 1994 issuance of a draft Generic Letter, " Voltage-Based Repair <

Criteria For the Repair of Westinghouse Steam Generator Tubes Affected By Outside Diameter Stress Corrosion Cracking,",for comment. ,

The May 1994 approval of the Braidwood request of a 1.0 volt Interim Plugging Criteria for 3/4" diameter SG tubing.

l The approval of similar requests for IPC for other plants with 3/4" and 7/8" diameter SG tubing. j The NRC's ongoing review of Electric Power Research Institute (EPRI) Draft Report TR-100407, "PWR Steam Generator Tube Repair Limits - Technical Support Document for Outside Diameter Stress Corrosion Cracking at Tube Support Plates," Revision 1, August 1993, and EPRI Draft Report NP-6864-'

L, "PWR Steam Generator Tube Repair Limits: Technical Suoport Document for Expansion Zone PWSCC in Roll Transitions - Rev. 2," h8 vision 2, August 1993.

An understanding of the NRC and industry desire to improve the basis for steam generator tube repair.

The completion of a satisfactory review assuring the structural integrity of Byron SG tubing during the next cycle operation.

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To support this request for amendment, Byron will remove tubes, as appropriate, from Unit 1 SGs for laboratory examination, leak, and burst testing. For scheduling

, and planning purposes, three tubes are expected to be removed during B1R06. It is the intent that each tube removed willinclude three support plate intersections

~ plus the flow distribution baffle intersection. The tubes will be selected for removal based on the size and distribution of indications which they contain. The results of the Braidwood Unit 1 tube pulls will be incorporated into the Byron i evaluation upon completion of Braidwood tube pull analyses.

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1 Analysis required by the IPC methodology will be completed to demonstrate leak )

and burst capabilities using B1R06 inspection results and Cycle 6 growth rates.

The bases of the IPC approach includes, in part:

Determination of a beginning of cycle (BOC) voltage distribution for Cycle 7 l with application of a POD of 0.6 in accordance with draft NUREG-1477. l Prediction of an end of cycle (EOC) voltage distribution by applying Cycle 6

{ growth rates to the BOC distribution through Monte Carlo simulations.

Application of a log-logistic probability of leakage (POL) function.

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Application of the EPRI leak rate versus voltage correlation (conditional leak rate model).

Calculation of the EOC leak rate and comparison with the site allowable leak rate for off-site dose consideration.

Calculation of the EOC tube burst probability and comparison with the allowable burst probability per NUREG-0800.

l i IMPACT OF THE PROPOSED CHANGE With the implementation of this proposed license amendment request, the Byron Unit 1 SGs will continue to satisfy the requirements of Regulatory Guide 1.121.

There will be no significant reduction in the margin of safety to protect the health and safety of the public. Based on current projections, approximately 1950 tubes with ODSCC would require repair under current repair criteria during B1R06.

2 implementation of a 1.0 volt IPC at Byron Unit 1 will save approximately 1350 i

tubec from repair. This represents a savings of approximately $5.2M in plugging and sleeving repair costs alone. In addition, IPC implementation saves a minimum of 24 days in critical path outage time and eliminates the associated replacement power costs. RCS loop asymmetries and the loss of rated thermal power due to excessive plugging and sleeving are minimized through IPC application and RCS flow and available heat transfer area are maximized.

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H. SCHEDULE REQUIREMENTS Comed requests that this proposed license amendment request be approved to permit IPC application during B1R06. Approval of this proposed license amendment request is required in order to declare the Byron Unit 1 SGs operable prior to entering Mode 4, Hot Shutdown. Based on the current outage schedule, Byron Unit 1 is predicted to be ready to enter Mode 4 on Wednesday, October 26, 1994. It is worthy to note that the steam generator manways are scheduled for reinstallation on Saturday, October 15,1994. In order to minimize potential rework and scheduling impact, Comed respectfully requests that this amendment be approved on or before October 15,1994.

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