ML19343A645

Responds to El Conner Request Re Summary of Findings on Unit 1 Reactor Coolant Pump Studs Per IE Notice 80-27.Insp of Four Pumps Reveals That 27 of 64 Studs Have Indications of Corrosion or Flaws Due to Pump Venting Techniques

ML19343A645
Person / Time
Site:	Calvert Cliffs
Issue date:	11/13/1980
From:	Ash R BALTIMORE GAS & ELECTRIC CO.
To:	Clark R Office of Nuclear Reactor Regulation
References
IEIN-80-27, NUDOCS 8011190358
Download: ML19343A645 (3)

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S ALTIMORE GAS AND - - .," . y ELECTRIC . ..,,

4 CHARLES CENTER . P.O. BOX 1475 . SALT lMORE. MARYLAND 21203

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, fs.:C3 Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Co= mission

'3ashington, D. C. 20555 Attn: Mr. Robert A. Clark, Chief Operating Peactors Branch #3 Division of Licensing Cubject: Calvert Cliffs Nuclear Power Plant Unit No. 1, Docket ?!o. 50-317 Reactor Coolant Pumn Studs

Reference:

IE Infor=ation ?!otice 80-27 dated 6/11/80 Gentlemen:

As requested by your Mr. E. L. Conner, Jr. , the following is a summary of our investiention and findings to date concerning the Unit ?!o.1 reactor coolant pu=p studs and the corrective measures we are planning.

~his effort was originally undertaken pursuant to the referenced Information Notice.

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All four Unit One Reactor Coolant Pumps vere inspected by BG!sE and Southwest Research Institute visual inspectors. The results vere that 27 of 6h Peactor Coolant Pump Studs did have indications of corrosion or unacceptable flavs. All of the affected studs were located on either #113 or #12A Reactor Coolant Pumps. The area of the studs exhibiting corrosion is the surface exposed closest to the pump case extending up as high as three and one-quarter (3-1/h"i inches. Some studs show corrosion extending into the pump case thread area.

ASME Code Section XI 197h Edition with Addenda through Summer 1975 Articic I'4B-3000, " Standards for Examination Evaluations", Paragraph I'43-3515,

" Standards for Examination Category B-G-1, Pressure-Retaining Bolting 2 in.

and Lsrger in Diameter" details the standard allevable indications for surface examinations. "his states that nonaxial indications shall not exceed 0.25 inches in length and axial indications shall not exceed 1.00 inches in length.

"'his criteria is subject to deviation beyond these limitations providing the evaluation of flaw indications can show accentability, or the flaw is removed and initial desien criteria acceptability of all changed conditions in accordante with the auplicable Codes is demonstrated. Anpendix A to Section XI, " Evaluation of Plav Indications", is not aeplicable to the evaluation of flaws found in the reacter coolant pumn studs.

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'. Fr. R. A. Clark Page 2  ?'ovember 13, 1980 t

lyron Jackson was requested to perforn an analysis in order that an

! accentance' criteria for the reactor coolant pump studs may be develened.

Prel'ninsry calculations have shovn that a minimum stud diameter of h.375 ine'hes is acceptable to meet the strength require =ent of the original stress snalysis report. tor the reactor coolant pu=Ds. Stu<ia W -eeting the minimum l die eter of h.375 inches are:

1 P"? #113 F C') #1?A Stud Dfaneter Stud Diameter 12 3 797 3 L.282 6 3.835 5 h.326 i 8 h.030 8 L.360 9 h.167 1 h.372 10 h.190 12 4.372 7 h.195 11 h.293 5 h.36C

' As a.n added conservatism, ve have identified all studs not having a mini?.um diameter of h.500 inches:

2CP'fl13 BCP #12A S +.u d Diameter Stud Diameter 15 h.hc9 h h.396 3 h.h10 10 h.L10

, 9 h.hl2 13 h.hl2 11 L.h31 6 h.h39 All remaining studs eith indicatiens were exanineu to deter .ine

• he secassibility of the indic stions for re:-oval and proper ITDE followinc flav removsl if neceptable flav removal vas possible. Sese additional studs with indications are:

PCP #113 FCP #12A Stud Diameter Stud Diameter, lh L.507 7 L 530 13 h.512 2 h.Sh3 2 h.525 16 Ha :mer ' arks

'a'e have determined that the stud corrosion troble: vas caused by pump venting techniques, FCP seal pressure line failures and the presence

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of other metal objects which encouraged localized deterioration. = proved pump venting techniques, increased inspection frequencies, improved house-keeuing techniques, and seal line modifications are expected to eliminate the stad deterioration problem. Due to the fact that no evidence of leak-age from between the pumo cover and-uuper face of the purp case was' found, we have eliminated gasket leakare as a cause of the subject deterioration.

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Mr. R. A. Clark Fage 3 nove=ber 13, 1980 Our current intention is to replace all 27 of the affected l ctuds (listed above) during this outage. Should difficulties.arise in i replacing any of the studs , further analysis vill, of course, be conducted to determine acceptable alternatives to stud replacement.

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Sincerely, R. F. Ash Chief Nuclear Engineer RFA/smn cc: J. A.-Biddison, Esquire G. F. Trowbridge, Esquire- ,

Messrs. E. L. Conner, Jr.

R. E. Architzel I

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