ML18030A046

Final Deficiency Rept Re States Co Sliding Link Terminal Blocks.Sliding Link Terminal Blocks & Bolt Will Be Subjected to Cycling Test,Completely Loosening & Retightening to Establish Acceptability for Use.Action Completed by 810731

ML18030A046
Person / Time
Site:	Susquehanna
Issue date:	05/08/1981
From:	Curtis N PENNSYLVANIA POWER & LIGHT CO.
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, PLA-766, NUDOCS 8105120301
Download: ML18030A046 (7)

Text

REGULA. Y INFORMATION DISTRIBUTIO SYSTEM (RIDS)

ACCESSION NBR: 8105120301 DOC DATE: 81/0'5/08 NOTARIZED: NO DOCKET ¹ FACIL:50-3S7 Susquehanna Steam

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Electric Stationi Unit li Pennsylva 05000387 50"3d8 Susquehanna Steam Electric Stationi Unit 2g Pennsylva 0 XFUW88 AUTH'AI4IE AUTHOR AFFILIATION CURTIS i N ~ ii ~ Pennsylvania Power 8 Light Co.

RFC IP ~ NAME. RECIP IENI AFFILIATION GRIERiB.H. Region ii Phil adelphiai Office of the Director'UBJECT:

Final deficiency rept'e users Co sliding link terminal States blocks'liding link terminal olocks 8 bolt will be suoJ ected to cycling testicompletely loosening 8 retightening to establish acceptaoility for Action completed by 810731, DISTRIBUTION CODE: B019S COPIES RECEIVED:LTR J, ENCL ~ SIZE' h TITLE'.- Construction Deficiency Repor t (10CFRSO.SSE)

NOTES:Send Send I8,E 3 I8E 3 conies f SAR copies FSAR 8

8 all all amends'50003'87 amends 050003'88 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME L. T l' E NC L lD CODE/NAME LTTR KNCI.

ACTION: A/D LI CENSNG 04 1 1 LIC BR ¹2 BC 05 1 1 RUSHBROOKtM ~ Ob 1 1 STARK<R ~ 07 1 1 INTERNAL ASLBP/ J ~ HA'RD 1 1 D/DIR HUM FAC 15 1' E,DO 8 STAFF 19 1 1 EQUIP QUAL BR11 1 1 HYD/GEO BR 22 1 1. I8E 09 1 l.

IE/EES 1 1 l IC QUAL BR 12 1 1 HPA 2v 1 1 NHC PDR 02 1 1

' REV 13 GELD 21 1 1 P 1 1 QA BR 14 1 1 EG FILE 01 1 STANDRDS DEV 21 EXTERNAL: ACHS lb 16 16 LPDR 03 1 1 NSIC 05 1 1 TOTAL NU41BER OF COP IES REQUIRED: LTTR 37 ENCL 37

TWO NORTH NINTH STREET, ALLENTOWH, PA. 18101 PIIONEr (215) 770-5151 NORMAN W. CURTIS Vice President.Engfneerinp 5 Construction-Nuclear 770.5381

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May 8, 1981

, <Qi(pg;,

Mr..Boyce H. Grier Tlr5e pR, 981 ~

Director, Region I C cREett tr COAIAII33~~7CraTr U. S. Nuclear Regulatory Commission 631 Park Avenue.

King of Prussia, PA 19406 SUSQUEHANNA STEAM ELECTRIC .STATION FiNAL REPORT OF A DEFICIENCY RELATiNG TO STATES SLIDING LINK TERMINAL BLOCKS ERs'00450/100508, FILES 840-4/900-10 9LA-76'6

References:

PLA-611 (1/10/81)

PLA-499 (6/23/81)

Dear Mr. Grierl This letter serves to provide the Commission with a final report of .a deficiency relating to defective States Company sliding link terminal blocks. This deficiency was originally reported in PLA-499 'and the information contained herein is submitted as a final report pursuant to the provisions 'of 10 CFR 50.55(e) .

The attachment to this letter contains a description of the design and operation of the terminal block, the deficiency, its cause,'teps taken to determine significance, an analysis of .safety implications and the corrective action taken and planned,.

We trust the Commission will find the information forwarded by this letter to be satisfactory.

Very truly yours, l-.*, Qo/7

';K) >~~

N. W..Curtis Vice President-Engineering & Construction-Nuclear FLW:sab Attachments LIGHT COAlPAHY

.81 05 yg pffft'EHHSYLVANIAPOWER IL g

C Mr.'Boyce H. Grier 2 May 8, 1981 cc: M". Victor Stello (15)

Director-Office of Znspection 6 Enforcement U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. G. McDonald, Director (1)

Office of Management Xnformation a Program Control U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. Gary Rhoads U. S. Nuclear Regul'atory Commission P.O. Box 52 Shickshinny, PA 18655

Va Attachment to PLA-766 SUBJECT Defective States Company sliding link terminal blocks, Type NT.

DESCRIPTION'OF DESIGN AND OPERATION

+e States sliding link terminal block has a terminal post and slotted bar.

fastened on either side of-a non-conductive block. The slotted bars are physically and electrically isolated from each. other. The connection between the two bars on the terminal block is made by a "U" shaped sliding link and spacer located between the two bars. The top of the "U" link has a hole through which the locking bolt passes. The bottom of the link, has a threaded hole to accept, an 8-32 bolt. When the bolt is/ tightened, it binds together the "U" link,, spacer, and slotted bars to make an electrical 'connection.

DESCRIPTION OF'EFECT The defect occurs in the form of a crack between the threaded hole and the side of the "U" link. When the bolt is tightened the crack widens and a poor or intermittent electrical. connection can result. from. lack of adequate torque on the binding bolt and "U" clip..

CAUSE OF THE CRACK L

Southwestern Laboratories, Inc. investigation into the failure of the U-Clips resulted in a report, "The Failure Analysis and Embrittlement Test on Brass U-Clips", dated November 2, 1979. In their "Discussion of Results", they attribute the failure of the U-Clips to embrittlement. The cause of this embrittlement may be attributed to either: 1) a cleaning process where ammonical cleaners were used or 2) plating in Watts type baths where hydro-chloric acid could act as tne embrittling or stress corrosion agent. They also reported that the more-recently manufactured U-clip embrittement was probably due to the use of harder than specified brass stock..

STEPS TAKEN TO DETERMINE SIGNIFICANCE' NRC IE Information Notice 80-08 was issued on Harch. 7, 1980, describing the subject defect in the- States sliding link terminal block. After receiving this notice, sampling procedure: E-1'57 was developed and implemented to determine if the described defect was characteristic of the States terminal blocks installed at Susquehanna Steam Electric'tation. The results bf the sampling program .were as follows:

(02 Links,.found to be acceptable 72 Links found to have minor defects '6 Links found to have major defects 500 - Total number of links inspected (Refer to Enclosure 1 of this attachment for definition of old style, new style, minor and major defects.)

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Attachment to PLA-766 Based on these findings, PPGL directed that Bechtel Engineering determine the effect a DBE would have on 'a cracked States terminal block. A seismic and hydrodynamic test was performed on 24 major defective and 24 minor defective States terminal blocks collected during the E-157 sampling program and 24 new style and 24 old style uncracked States terminal- blocks. Four major defective terminal blocks failed to hold the required 18 2 Kn-ebs'f torque, bet he..' torque of 13, 5, 1 and 0 in lbs, respectively. The terminal block torqued to . in-lb failed to continue to carry current duz'ing the seismic and hydro-dynamic test.

Previous to the seismic test, Sandia Laboratories under contract with the; NRC.-subjected known defective terminal blocks torqued ae. 16 in-,lbs to a LOCA'"environment.

The results showed that the. terminal block did not loosen appreciatively during the test. Multi-Amp Corporation, 'of which the States Company is a subsidiary, previously aware of the cracking condition, had Southwestern Labs perform a mettallurgical analysis of the cracking problem., Southwestern's findings are outlined. in "Cause "of Crack" section of this report.

The significance of all the investigative tests are that cracked States blocks

'were found in equipment at Susquehanna SES 'and', cracked block can lead to an open or intermittent. circuit.. In addition,, it., was. found. that cracked. States terminal blocks were located in safety related circuits., No circuit failures have resulted to date as a. result of defective States terminal blocks.

r w..

ANALYSIS OF SAFETY IMPLICATIONS The States sliding link terminal block that failed during the seismic and hydrodynamic test was., removed from a Class 1E system. Based on the findings of the E-157 inspection program, it is known 'that cracked sliding link terminal The potential exists that. there blocks are installed in equipment at Susquehanna.

may be additional defective sliding link terminal blocks in operation similar to the terminal block which failed the seismic test. 'ased on these findings, NPE has determined that the. cracking of the "U" link on the States sliding link terminal block is a reportable- item per 10CFR 50.55(e).

CORRECTIVE ACTION The reasons for justifying the proposed and in progress corrective. action plan are listed below:

1. Sandia Laboratories subjected known defective States sliding link terminal blocks to a LOCA environment. The sliding li.nks were torqued to 16 in-lbs and did not loosen appreciatively during the LOCA simulation environment.

2. Wyle Laboratories performed a seismic and hydrodynamic test on major and minor defective and non-cracked "old" and "new" style terminal

,blocks., Those terminal blocks which torqued to 18 in-lbs continued to function throughout the'test.

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Attachment to PLA-766

3. Southwestern Laboratories in the conclusion of their report stated that.

"two or three loosening cycles should eliminate all the clips. that were embrittled in the cleaning or plating operation".

Based on the above conclusions, NPE determined that the States sliding link terminal block "U" link and bolt must be subjected to a cycling test, completely loosening and re-tightening the bolt four (4) times to a specified torque of 18 + 2 in-lbs in order to establish'heir acceptability for use. All States terminal blocks installed in Class lE and turbine and generator primary and backup trip circuits on Unit Sl and Common will be cycled in accordance with the ISG developed Technical Procedure 1.31 "Sta es Block Link-Toraue Test". The pass-fail criteria used in TP 1.31 is that a cracked "U" link is considered defective if the binding bolt can not be torqued to 18 +

in-lbs. Should the "U" link fail to tighten during the cycling the terminal blocks and 2

circuit will be documented and the defective block will be replaced with a "new style" States terminal block. The procedure will locate and eliminate the States terminal blocks that failed to torque to 18 + 2 in-lbs. The blocks that can be torqued to 18 + 2 in-lbs will be considered acceptable even though a crack may exist in the link.

The cycling procedure will not be repeated on a terminal block after the block has been completeIy cycled in accordance with TP 1.31. No specific torque valve will be recuired after the terminal block has successfully passed the cycling procedure.

Quality Control 's monitoring the activities described in TP 1.31 under the guidelines of QA procedure AD-00-054. NPE will review the results of TP 1.31 to determine procedu.",e 'should be. expanded,'o include States terminal blocks in'NON&lass if the Bechtel's corrective action plan includes Unit h2 equipment and is identical lE'quipment.

to that discussed above. Appendix D to Bechtel's rield Procedure E-8 has been issued to describe the program for Unit 2.

SCHEDULE The Corrective Action Plan outlined above for Unit 1 and Common is scheduled for completion by July 31, 1981. Corrective action for Unit 52 will be. performed on a per system basis as systems are turned over to PPGL.

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Attachment to PLA-766 Enclosure 1 NOTE

'I A linear indication is a s'urface deformation in which the length is more than three times the width.

A  :. nded indication is a surface deformation either circular or elliptical with the length less than three times the width.

a) in either face of che flat surface surrounding the threaded hole:

1) A 'linear indication greater than 1/32" long.

2) A rounded indication greater than 1/16" in diameter.

3) Four or more indications in a line separated by 1/32" or less, edge to edge.

b) in other portions of the link, including the upset portion and the threaded surface:

1) A linear indication greater than 1/16'~ long.

2) A rounded, indication greater than 1/8" in diameter..

3) Four or more indications in a line separated by 1/16" or less, edge to edge.

Mi or Defectives r e.

Any relevant'ndications more than 50% and less than 100% of the size discussed in the Major Defectives shall be considered a minor defect.

Old and New St le U-Cli s A sliding link is considered a "new style" if the thickness of the neck of its U-Clip is 3/64". if the thickness is 1/16" it is considered an "old style".

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