RC-93-0039, Application for Amend to License NPF-12,modifying Insp Requirements in TS 3/4.4.5, SGs & LCO for 3/4.4.6.2, Operational Leakage to Avoid Unnecessary Plugging of SG Tubes W/O Compromising Safety

Application for Amend to License NPF-12,modifying Insp Requirements in TS 3/4.4.5, SGs & LCO for 3/4.4.6.2, Operational Leakage to Avoid Unnecessary Plugging of SG Tubes W/O Compromising Safety

ML20128H967
Person / Time
Site:	Summer
Issue date:	02/12/1993
From:	Skolds J SOUTH CAROLINA ELECTRIC & GAS CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20128H971	List: ML20128H978 RC-93-0039, Application for Amend to License NPF-12,modifying Insp Requirements in TS 3/4.4.5, SGs & LCO for 3/4.4.6.2, Operational Leakage to Avoid Unnecessary Plugging of SG Tubes W/O Compromising Safety
References
RC-93-0039, RC-93-39, TSP-920001-1, NUDOCS 9302170256
Download: ML20128H967 (3)

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sogi caro lna metrie a o:. comp:ny gn 2 nuciear opmnons engngsc mes sceae-ma w February 12, 1993 Refer to: RC-93-0039 Document Control Desk U. S. Nuclear Regulatory Comission Washington, DC 20555 Gentlemen:

Subject:

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS)

DOCKET NO. 50/395 OPERATING LICENSL NO. NPF-12 TECHNICAL SPECIFICATIONS CHANGE REQUEST INTERIM PLUGGING CRITERIA (TSP 920001-1)

In accordance with 10CFR50.90, South Carolina Electric & Gas Company (SCE&G) is submitting an amendment request to License NPF-12 to change the Technical Specifications (TS) for VCSNS. This request seeks to modify the inspection requirements of Technical Specification 3/4.4.5, " Steam Generators," and the Limiting Condition for Operation for 3/4.4.6.2, ' Operational Leakage," such that unnecessary plugging of steam generator tubes is-avoided without compromising safety.

During the 1994 (RF8) outage at the V. C. Summer Nuclear Station, the original Model D3 steam generators will be replaced with Delta.75 feed ring type steam generators. It is desirable that the plant operate at 100% power ,

i until the replacement outage. In order to maximize plant performance by ensuring that steam generator tube plugging level remains below the licensed plugging limit, an interim plugging criteria (IPC) has been developed for single cycle implementation to address the tube integrity issues raised by the presence of outer diameter stress corrosion cracking (ODSCC) at the tube support plate elevations of the Vs C. Summer steam generators. The criteria will be applied during Cycle 8 using the steam generator eddy current results-obtained during the 1993 (RF7) outage. V. C.. Summer eddy current inspection data has been utilized along with tube pull results and burst test information from other plants to establish an interim, voltage based steam generator tube plugging criteria. The V. C. Summer IPC has as its basis correlations between eddy current bobbin probe signal amplitude and tube burst strength and leakage characteristics. The plugging criteria remains commensurate with RG 1.121 and RG 1.83 criteria, and, hence, meets General Design Criteria 14, 15, 31, and 32. It is shown that, during normal

. operating ar.d accident conditions, tube burst margins are consistent with or exceed all applicable criteria of Regulatory Guide 1.121 " Bases for Plugging-Degraded PWR Tubes."' Also, General Design Criteria 2 and 4 are met'as'it is-expected that the V. C. Summer steam generators car. continue to perform their intended safety function upon implementation of the IPC.

From a tube leakage perspective, the potential for adverse radiological consequences due.to primary to secondary leakage during postulated accident-condition loadings is addressed. Per the V. C. Summer FSAR, the most limiting accident with regard to the potential for off-site dose consequences at.V. C. Summer is a postulated locked rotor event. However, upon i.

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Document Control Desk i TSP 920001 1 Page 2 of 3 implementation of the IPC, little or no leakage above normal operating leakage would be expected at the peak differential pressurt:s experienced during this transient (assumed to be a maximum of 1500 to 1600 psi as compared to 1332 psi at normal operation), since it is postulated that a loss of structural ligaments between cracks is required for a significant increase in steam line break (SLB) leak rate.

The next most limiting transient would be a postulated SLB event. The potential for excessive leakage during a postulated SLB is minimized by verifying that the expected distribution of crack indications at end of cycle (E0C)wouldresultinalevelofleakagelessthan1gpm,suchthatthe radiological consequences are less than a small fraction of the 10CFR100 guidelines. For other accidents in which there is a secondary side steam release, there is justification for mixing and iodine partitioning in the steam generators--depending on the elevation of the degradation relative to the change in steam generator water level during the plant transient. These factors significantly reduce the release of iodine to the environment.

Additionally, the potential for secondary to primary in-leakage during a postulated LOCA + SSE event has been addressed; any in-leakage is expected to be less than any measured operational leakage at the time of the event (and much less than 150 gpd). Furthermore, based on operating plant data,

, implementation of the IPC would not result in significant potential for primary to secondary leakage at normal operating conditions.

The bobbin coil voltage signal amplitude is used as a plugging criteria to effect the disposition of steam generator tubes that are experiencing 00 SCC within the thickness of a tube support plate. A summary of the V. C. Summer Interim Tube Plugging Criteria is described below:

1. A tube can remain in service if the flaw indication signal amplitude is less than or equal to 1.0 volt, regardless of the depth of wall penetration.

2. For flaw indications in excess of 1.0 volt but less than 2.2 volts, the tube can remain in service provided an Rotating Pancake Coil (RPC) inspection of the indication does not detect ODSCC or any other degradation mode exceeding the technical specification repair limits.

3. Crack indications above 2.2 volts will be repaired by plugging and do not require RPC confirmation.

4. Based upon an end of cycle voltage distribution for crack-like indications, additional tubes may be removed from service utilizing a conservative estimation of potential primary to secondary leakage in the event of a steam line break such that the leak rate will be limited to 1.0 gpm (maximum) in the faulted loop. Normal operating condition leakage will be limited to a maximum of 150 gpd in any steam generator and a total of 450 gpd for all three steam generators.

The above criteria is established using applicable NRC guidelines and represents conservative limits which bound the structural integrity requirements of the potentially degraded tube bundle during normal operation and postulated accident conditions. The basis supp3rting application of the proposed IPC is furnished in WCAP-13522.

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-The request is contained-in t'he following attachments:

Attachment 1- The-Technical _. Specification pages as proposed by;this-amendment: request.

Attachment 2 Description of Amendment Request and Safety Evaluation.-

Attachment _3 Description of Amendment Request and No Significant Hazards Determination..

VCSNS his made every reasonable effort to include justification for.the recent industry. issues surrounding alternate plugging criteria. _.

Unfortunately, these-issues have impacted the-schedule of this submittal.-

However, phone' calls, meeting and presentations by VCSNS and the industry.

have been held with the NRC to both familiarize the staff with approaches used in this-submittal as well as to ensure that NRC concerns are-addressed.

Due to this involvement by the NRC, SCE&G is requesting that the review.of this submittal be expedited t.o allow a approval determination to be made by March 22, 1993.

These changes-have been reviewed and approved by the Plant Safety Review Committee and the Nuclear _ Safety Review Committee.

I declare that the statements and matters set forth herein are true and -

correct to the best of my knowledge, information, and belief.

Should you have any questions concerning this issue, please call Mr. David C.

Haileat.(803)345-4322 at your convenience.

Very truly yours.-

M John . Skolds-DCH:smd Attachments c: 0. W. Dixon h R. R. Mahan R. J. White S. D. Ebneter G. F. Wunder-General Managers NRC-Resident. Inspector

.J. B. Knotts Jr.

H. G. Shealy RTS (TSP 920001-1)-

File (813.20) i NUCLEAR EXCELLENCE - A SlM4ER TRADITION!

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