ML20062L597
| ML20062L597 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/05/1981 |
| From: | Ash R BALTIMORE GAS & ELECTRIC CO. |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| IEIN-80-27, NUDOCS 8102120005 | |
| Download: ML20062L597 (2) | |
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6 B ALTIMORE GAS AND ELECTRIC CHARLES CENTER. P.C. BOX 1475 BALTIMORE, MARYLAND 21?03 ELECTRIC ENGINEERING
?ebruar7 5' 1n61 DEPARTMENT n*fice of Nuclear Reactor Peculation U. S. Nuclear Pemilatory Commission Nashincton, n. C.
20555
~
Attn:
"r.
Pohert A. Clark. Chief Ornrstinc 'aactors Franch 33 Division of Licensing Sub. ject : Calvert Cliffs Nuclear Power Plant Unit No. 2, Oceket No. 50-313 Mc_ tor "ce' ont N.n 9tuds lentlenen:
?tt letter of !iovember 13, 1980, su-r.arized our findings and actions on Unit No.1 Reactor Coolant Putn (RCPI studs pursuant to IE Information Notice 30-27.
Following is a summary of our investigation and findines to date concerning the Unit No. 2 RCP studs snd the corrective measures we are olanning.
Visual examination of all four Unit 2 RCP studs has been concleted.
Of the total of 6h studs, four studs on RCP No. 22-A and eight studs on RCP No. 22-B shoved signs of corrosion. The area of the studs exhibiting corrosion is the surface exnosed closest to the nunn case extending un as hirh as two inches. Some studs shov corrosion extendine into the pumn case thread srea as much as 0.25 inch.
ASME Code Section XI lo7h Edition with Addenda through Summer 1975, Article IWB-3000, " Standards for Examination Evaluations", Paragranh IVB-3515 " Standards for Examination Category 3-G-1, Pressure-Retaining 9oltine Two Inches and Larrer in Diameter", details the standard allovsble indications for surface examinations. This states that nonaxial indications shall not exceed 0.25 inches in length and sxial indications shall not exceed 1.00 irch in length. Based on this criteria, all twelve studs exhibiting corrosion are considered unacceptable by the Code and vill be renlaced with new studs.
In eeneral, the stud corrosion "ound on Unit 2 RCP's vss not as extensive an that "ound on I' nit 1.
As on Unit 1, tha t' nit 2 nu.ns chov no siens of racket "ailure between the numn case and driver mount. The cause of stud corrosion is believel to be a combination of reactor coolant nurn 02120006 Q 81
o a.
Mr. R. A. Clark Page 2 February 5,1981 instrunent line failures. noor centrol of reactor coolant during ventine anerations, and instrument line valva cackinc leakare, all counled with noor houcekeeping around the punp cas? area. Improved rumo ventin? teeh-nioues, increased insnection frequencies, innroved housekeening techniques, and seal line modifications are exnected to eliminate the stud deterioration problem.
The following studs were affected and vill be renlaced during the current outage:
RCP I!o. 22-A RCP "o. 22-3 Stud #
Stud #
h 1
5 2
6 3
7 h
5 G
13 lh Should difficulties arise in replacing any of the studs, further analysis vill, of course, be conducted to determine accentable alternatives to stud renlacement.
Sincerel',
-1 R. F. Ash Chief !uclear Engineer AE0/ san ec:
J. A. Biddison, Esquire G. F. Trowbridge, Esquire Messrs. E. L. Conner, Jr.
R. E. Architzel}