B11568, Forwards Results of Core Barrel Insp Performed During Cycle 7 Refueling outage.Through-wall Cracks at Thermal Shield Support Lugs 4 & 5 Not Propagated

Forwards Results of Core Barrel Insp Performed During Cycle 7 Refueling outage.Through-wall Cracks at Thermal Shield Support Lugs 4 & 5 Not Propagated

ML20126F169
Person / Time
Site:	Millstone
Issue date:	06/11/1985
From:	Opeka J, Sears C NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	Butcher E Office of Nuclear Reactor Regulation
References
B11568, TAC-56814, NUDOCS 8506170381
Download: ML20126F169 (4)

Text

P-General Offices

• Selden Street. Derhn, Connecticut I ' ' "" P.O. BOX 270 k k J "g" . .'j,,[","""

aos . , me.a w HARTFORD, CONNECTICUT 06141-0270 (203) 665-5000 June 11,1985 Docket No. 50-336 Bil568 Director of Nuclear Reactor Regulation Attn Mr. E. 3. Butcher, Acting Chief Operating Reactors Branch #3 U.S. Nuclear Regulatory Commission Washington, D.C. 20555

References:

(1) W. G. Couns!! letter to 3. R. Miller, dated December 12, 1983.

(2) 3. R. Miller letter to W. G. Counsit, dated May 8,1984.

(3) W. G. Counsil letter to 3. R. Miller, dated February 15,1985.

Gentlemen Millstone Nuclear Power Station, Unit No. 2 Core Barrel Inspection In Reference (1) Northeast Nuclear Energy Company (NNECO) provided a report in connection with the thermal shield removal and plant recovery program. In Section 9.5 of that report NNECO committed to evaluate performing inspections of the core barrel to verify that the through-wall cracks at thermal shleid support lugs 4 and 5 have not propagated.

In Reference (2) the Staff provided its review of the Millstone Unit No. 2 thermal shield recovery program. The Staff's principal recommendation was that the core barrel be inspected during the next refueling outage.

In Reference (3) NNECO provided a summary of the core barrel inspection to be performed at Millstone Unit No. 2 during the Cycle 7 refueling outage. NNECO committed to provide the NRC the inspection results and conclusions on or about June 1,1985. Accordingly, the attachment provides the examination results of the Millstone Unit No. 2 core barrel. The results verify that through-wall cracks at thermal shleid support lugs 4 and 5 have not propagated.

o f

8506170301 850611 ll; DR p ADOCK 05000336 I' PDR {

l

l .y We trust you will find this information satisf actory.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY 4,%.SAw.

3. F. Opeka' Senior Vice President By: C. F. Sears Vice President r

i

k. ._ ._____________. . _ _ _ _ . . _ _ . _ _ _ _ _ _

x-

$Y Docket No. 50-336 Attachment Millstone Nuclear Power Station, Unit No. 2 Core Barrel Inspection June 1985

,?

Millstone Unit No. 2 Core 13nrrel Inspection Report ITackground This report summarizes the visual examination performed on the Millstone Unit No. 2 core barrel during the 1985 Cycle 7 refueling outage. Eddy current examination was used ta classify visual indications as surface irregularities or flaws.

Visual examination of the reactor vessel core barrel was performed in the area of the thermal shield support lug locations #4 and #5. These lugs were removed during the 1983 Cycle 6 refueling outage when cracks were found at these locations. The examination performed was to determine if, during the last operating cycle, any further degradation had developed. The examinations performed consisted of a visual examination of the lug areas, followed by eddy current examination to detect areas of possible new flaws.

Results The visual examination of the lug #4 area identified 4 visual indications including the previously identified flaw that was arrested by drilling crack arrestor holes during the last outage. The other suspect indications were scanned using a surface riding eddy current technique and determined to be nonrelevant surface imperfections.

The visual examination of the lug #5 area identified 9 visual indications. Five of the indications were identified visually as tooling marks. Three of the indications were scanned using eddy current examination and determined to be nonrelevant. One indication is part of the original cracking identified in 1983 and showed no change.

Visual examination Information was videotaped for future reference and to document examination results. Examination personnel and tooling were supplied by NPD of 13abcock & Wilcox (B&W),1.ynchburg, Virginia. All personnel reviewing data and recording results were quallfled level 11 technicians in accordance with NNECO and !)&W administrative procedures.

Summary The visual and eddy current examinations revealed no evidence of flaw propagation or new flaws on the Millstone Unit No. 2 core barrel.