ML20086G304

Provides Addl Info to Clarify Util Intended Actions Re Crack Growth Monitoring for N4D Feedwater Nozzle Safe End Welds.Crack Growth Data for Inconel 182 Sample from Crack Arrest Verification Sys Will Be Obtained Every 30 Days

ML20086G304
Person / Time
Site:	Brunswick
Issue date:	11/27/1991
From:	Vaughn G CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NLS-91-307, TAC-M79381, NUDOCS 9112050033
Download: ML20086G304 (2)

Text

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O O CML Carolina Power & Light Company P O Boa 1b51 e Ra6eigh, N C 27602 110\/ 0 7 1991 SrRIAt: NLS 91307 G E VAUGHN v u e,.....ni w.., s.,,o. o.e.n,,,.ni United States Nuclear Re0ulatory Commission AT T ENTION: Document Control Desk Washington, DC 20555 BRUNSWICK STEAM LLLCIRIC PLANL UNil NO.1 DOCKET NO. 50-32b/LICLNSE NO. DPR.71 If f DWATFR NQZZLE N4D SAIE LND UT INDICATION (NRC TAC NOT/9381)

Gentlemen:

The purpose of this letter is to provido additionalinfortnation to clarify Carolina Power & Light Company's (CP&L) intended actions concerning crack growth monitoring for the N4D feedwater nottle safe end attachmei t welds at the Brunswick Steam flectric Plant, Unit No.l. [3y letter dated September 10,1991 (Senal NLS 91-232), CP&L provided a written response to the NRR Project Manager's request of August 8,1991 to Hentify the Company's intended actions based on the use of data obtained from the crack arrest verification system (CAVS) to monitor crack growth rate conditions in the reactor coolant system. Carolina Power & li0ht Company had informed the NRC of its intention to use CAVS data for this purpose at a meeting attended by CP&L and NRC representatives on May 23,1991. At this meetin0, the Company also stated that if excessive crack Drowth rates were postulated for the N4D norile indication based on the CAVS data, additional actions would be initiated, including unit shutdown, if deemed appropriate. A summary of that meeting was issued by the Staff by letter dated May 31,1991.

In a telephone conversation on November 8,1991, the NRR Project Manager requested that CP&L provide additionalinformation clanlying the Company's intended actions based on the CAVS monitoring. Accordin0l y, the followin0 nformation i is provided in order to clarify CP&L's intended actions concernino crack growth monitorino for the Brunswick Unit No.1 N4D norile safe end welds:

1. Crack growth data for the loconel 182 sample from the Crack Arrest Verification System (CAVS) will be obtained;

a. At least every 30 days, and

b. Within 7 days of startup following a reactor shutdown or scram.

2. The data will be reviewed and compared to the maximum projected crack growth rate of 2.4S E b inches per hour, which was previously analyzed.

a. If the average crack growth rate observed during any thitty day period contin misty exceeds the projected crack growth rate of 2.4b E b inches per hour, the CAVS data (vill be obtaincd at least every seven days until the I thirty day average crack growth rate returns to less than the 2.45 E 5 rate for two consecutive 7 day periods.

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Document Control Desk NLS 91232 / Page 2

b. If the average crack growth rate observed during any forty five day period continuously exceeds 2.45 E 5 inches per hour, an engincenny evaluation will be performed to project the time at which the feedwater nozzle flaw would be expected to exceed the ASME Section XI allowable flaw sire.

Plans will be implemented to shut down Unit 1 prior to the projected site exceeding 0.4792 inches, which correspends to 80 percent of the ASME Section XI allowable flaw sire.

c. In the event that the CAVS monitoring reveals a crack growth rate above 2.45 E 5 on repeated occasions, without a continuous period exceeding 45 days, then an engineering analysis will be conducted when the number of cumulativo days of high growth ratt, exceeds 45 days.

d. If the average crack growth rate observed during any thirty day period exceeds 3.0 E 5 inches per hour, an evaluation will be performed to determine the cause of thin high crack growth rate, and reduce it to a level below 2.45 E 5 inches per hour. If the average crack growth rate observed through any 45 day period continuously exceeds 3.0 E 5 inches per hour, plans will be implemented to shut down Unit 1 within 15 days.

3. The NRC will be notified if plans are made for Unit 1 shutdown. During the unit shutdown, an ultrasonic examination of the flaw will be made to determine if changes have occurred since the rrsvious ultrasonic examination. The results of the examination .. hall be submitte j to the NRC.

4. F'uture plans for inspection, evaluathin, and/or repair as necessary during the next scheduled refueling outage remain as presented at the May 23,1991 meeting between CP&L and the NRC.

Brunswick Unit 1 will reach its mid-cycle during mid December,1991. Therefore, CP&L requests NRC approval for continued operation of Drunswick Unit 1 until the next Unit 1 refueling outage, currently scheduled to begin on September 12,1992. Carolina Power & Light Company hereby requests N4C approval of this request by December 12,1991, in order to avoid an unnecessary shutdown of Brunswick Unit 1.

Plt.ase refer any questions regarding this submittal to Mr. W. R. Murray at (919) 61G 4061.

Yours very truly,

. . . /-- l l khh6$ay

- G. E. Vaughn JCPTjcp (commit 2.wpf) cc: Mr. S. D. Etnoter Mr. N. B. L e Mr. R. L. Prevatte

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