ML20127B711

Application for Amends to Licenses DPR-77 & DPR-79,revising TS Surveillance Requirements & Bases to Incorporate Alternate S/G Tube Plugging Criteria

ML20127B711
Person / Time
Site:	Sequoyah
Issue date:	01/08/1993
From:	Fenech R TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20127B714	List: ML20127B711 ML20127B717
References
NUDOCS 9301130073
Download: ML20127B711 (6)

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Teresen Vaney AuWyy Pm.! OKce Ba 2000. Soddy-Omsy. Termssee 37W2000 Robert A. Fenech vee Wewont. Sewyan Nucter r, ant January 8, 1993 TVA-SQN-TS-92-10 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

In tho Matter of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 SEQUOYAH NUCLEAR PLANT (SQN) - TECHNICAL SPECIFICATION (TS) CHANGE 92-10 W* TUBE PLUGGING CRITERIA FOR STEAM GENERATORE -(S/G)

Reference:

TVA letter to NRC dated November 18,1992, "Sequoyah Nuclear Plant (SQN) - Westinghouse Commerci.a1 Atomic Power (WCAP)

No. 13532, Revision 1, 'Sequoyah Utits 1 and 2, W* Tube Plugging Criteria for SG Tubesheet Pegion of WEXTEX Expansions'"

In accordance with 10 CFR 50.90, we are enclosing a requested smendment to Licenses DPR-77 and DPR-79 to change the TSs of SQN Units 1 and 2.

The proposed change revises TS surveillance- requirements and lases to incorporate alternate S/G tube plugging criteria. This criteria is referred to as the W* criteria and was developed for SQN Units 1 and 2 on plant specific conditions. The W* criteria takes into account the reinforcing effect that the tubesheet has on the external surface of the S/G tube in the Westinghouse Explosive Tube Expansion (WEXTEX) region.

The approach taken to develop W* criteria is to use the general methodology of the staff approved L* criteria for hardroll expansions and adapt the methods for WEXTEX expansions. The W* criteria provide alternate tube plugging requirements for S/G tubes having indications in the WEXTEX region. The W* criteria reduce the need to repair or plug S/G tubes and are based on maintaining structural and leakage integrity of tubes that are returned to service with indications in the WEXTEX region.

The proposed TS change is identified in Enclosure 1. The justification for the proposed TS change is provided in Enclosure 2. A proposed determination of no significant hazards consideration performed pursuant to 10 CFR 50.92 is provided in Enclosure 3. The WCAP analysis supporting this TS change was previously provided in the reference letter.

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4 U.S.' Nuclear Regulatory Commission Page-2; January 8, 1993 NRC issuance of the proposed change is requested as soon as possible.

Approval before the upcoming Unit 1 refueling outage istdesired to-preclude additional plugging'of S/G tubes duringLthe outage-(currently scheduled to begin April 2, 1993, and end June 5, 1993). A 30-day period is requested to implement-the TS change _upon NRC approval. TVA will keep-NRC project management informed of any schedule changes through routine projact review meetings.

Please direct questions concerning this issue to D. V. Goodin at (615) 843-7734.

Sincerely.

Ms Robert A. Fenech-

. Sworn to aqd subsc . bed before me this F// day- of -

/>/2t 1993

4. , /0 Notary Public My Commission Expires Enclosures cc (Enclosures):

Mr. D. E. LaBarge, Project Manager U.S. Nuclear Regulatory Commission One White Flint,.. North 11555-Rockv111e-Pike-Rockville,' Maryland 20852-2739 Mr. Michael H. Mobley, Director (w/o Enclosures) .

Division of Radiological-Health 3rd Floor.

L & C Annex-i' 401 Church Street?

Nashville, Tennessee 37243-1532.

NRC Resident ~ Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road

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Soddy Daisy, Tennessee 37379-3624 L

L Mr. B. A. Wilson, Project Chief i U.S. Nuclear Regulatory Commission l Region II l 101 Marietta Street, NW, Suite 2900 L Atlanta, Georgia 30323-0199 i.

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Il ENCLOSURE 1-

PROPOSED TECHNICAL-SPECIFICATION.' CHANGE

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SEQUOYAH NUCLEAR PLANT UNITS 1..AND'2- ,

DOCKET NOS. 50-327 AND'50-328 (TVA-SQN-TS-92-10).

LIST OF AFFECTED PAGES UNIT 1 s

3/4 4 3/4 4 3/4-4-9 3/4 4-10 B 3/4 4 UNIT 2 3/4-4-11 3/4 4 >

'3/4'4-13.

3/4 4-14 B 3/4-4-3;

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9 JESERI_A

4. A11'nonplugged tubes with previously identified _ degradations within the tubesheet shall be bobbin-coil inspected through the full length of the tubesheet region. All W* tubes shall be rotating pancake coil (RPC) inspected the full W* distance. W* tubes may.be excluded from 4.4.5.2.b.1, provided the degradation is contained.within or below the W* distance. -

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d. All steam generators in which W* tubes are located shall be inspected at each subsequent refueling outage, m

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6. Elugging Limit (except in the tubesheet region of W* tubes) means the imperfection depth at or beyond which the tube shall_ be removed f rom service and is equal to 40% of the nominal tube wall thickness.

Within the tubesheet and below the W* distance, any degradation is:

acceptable. Within the W* distance, the following limits shall apply:

a. A minimum length'as defined in 4.4.5.4.a.11 shall be demonstrated to be nondegraded by RPC inspection.

b. i ial cracks must have the upper crack tip below the Bottom of the WEXTEX Transition (BWT) and top of tubesheet plus eddy current uncertainty.

c. Bands of parallel, axial oriented cracks shall be limited to

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five cracks. If the cracks are inclined relative to the tube axis (30' or less), the-total circumferential oriented inclination summed over all cracks shall be less than 92at the-beginning of cycle. Similarly, the circumferential extent of closely spaced axial cracks must be less.than 92* at beginning of cycle _between the " null points"non the RPC amplitude.

d. Circumferential cracking identified within the W* distance must be located below the BWT and at least 0.1 inch below the top of-the tubesheet. The extent of circumferential cracking must be less than a 92* arc.

e. The total calculated steam-line break leakage shall be less_than 1.0 gpm for any steam generator. If the calculated leakage exceeds the allowable lunit, an appropriate number of tubes with degradation shall be removed from service to satisfy the allowable leakage limit.

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-1HSERI_D

10. Ho.Liom_oL_the_REXTEX Tranaitlan (BWT)-is the highest point of'.

contact between the tube and tubesheet below the top-of-tubesheet as determined by eddy current testing.

11. W* Dialancs is the distance into the tubesheet below the BWT that precludes tube pullout. The W* distance:-requires,5.1 inches ot.

nondegraded tubing for Zone B and 4.2 inches of nondegraded tubing for Zone A. The following must be added to the nondegraded_ distance _

to obtain the W* distance and.the RPC inspection extent:

a. Axial lengths of cracks detected.

b. Crack end effects (1.0 times crack length for Zone B and 1.2 times crack length for Zone A).

c. NDE measurement uncertainty.

12. W* Tuhn is a tube with degradation, within the W* distance' equal to or greater than 40%,'and degraded within the limits specified in 4.4.5.4.a.6. In addition, a W* tube is a tube with any degradation below the WA distance.

111SERLE

a. Following each in-service inspection of. steam generator tubes, the number of tubes plugged-in each steam generator _and the'results of the inspection of W* tubes shal1~be reported to the Commission within 15 days following restart (Mode 2) of the unit.

JESERLE Extensive European operating experience with axial primary water stress corrosion cracking-(PWSCC) cracks _left in. service has demonstrated:

negligible normal operating leakage from PWSCC cracks-_even under free span conditions in the roll; transitions. PWSCC cracks in WEXTEX_.

expansions in' the tubesheet. region would be' further leakage 1.imited by'.

both'the tight tube-to-tubesheet crevice.and the_ limited crack opening _

permitted by the-tubesheeteconstraint. Consequently,4 negligible normal operating leakage.is expected from cracks within.the tubesheet region'ofi WEXTEX~ expansions.

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1RSELLD For tubes to which the W*. criteria is applied, indications of degradationj in excess'of 40% throughwall can remain in service without:a loss of functionality or structural and leakage integrity.- Tubes to'which W* is applied can experience throughwall. degradation up to the 1imits defined

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in the NRC staff approved version of WCAP-13532-without increasing the probability of a tube rupture or large leakage event. It is. intended that the W* criteria and resulting inspections be applied to the tube sheet sections of the steam generator that are susceptible to PWSCC. <The guidance of Regulatory Guide 1.121-is used to assess the-limits of acceptable tube degradation within W*. A potential exists for W* tubes to allow primary-to-secondary leakage-during a postulated steam-line-break. Information is provided in WCAP-13532 that is used to define steam generator W* Zones A and B and to calculate the expected leakage at steam-liae break conditions for W* tubes. The calculated leak rate shall _

be limited to less than-1.0 gpm in any one steam generator in order to maintain'offsite doses to within 10% of the 10 CFR 100 limits during a postulated steam-line; break event.

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