United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9612170255






                                   107 Selden Street, Berlin, CT 06037

Northeast

Utilities System                   Northeast Utilities Service Company

                                   P.O. Box 270

                                   Hartford, CT 06141-0270

                                   (860) 665-5000



                                                       December 13, 1996

                                                       Docket No. 50-245

                                                                  50-336

                                                                  50-423

                                                                  B16030



US Nuclear Regulatory Commission

Attention: Document Control Desk

Washington, D.C. 20555



          Millstone Nuclear Power Station Unit Nos. 1, 2 and 3

            10 CFR 21 Report Concerning Cracked Fuse Ferrule

                       Defects (NRC Event # 31371)



In conformance with 10CFR21, Northeast Nuclear Energy Company (NNECO)

provides notification of a Substantial Safety Hazard (SSH) at the

Millstone Nuclear Power Station.  NNECO's commitments associated with

this letter are provided in Attachment 1.



The NRC Operations Center was notified by facsimile on November 22, 1996,

(see Attachment 2) that during testing of electrical fuses initiated by

NNECO, the ferrules separated from the fuse cartridges.  Testing was

initiated to assist NNECO in evaluating longitudinal cracks found in the

fuse ferrules.



The following information applicable to this SSH is provided, as outlined

by 10CFR21.21 (d)(4)(i) through (viii)



(i)  Name and Address of Individual Informing the Commission



     Jay K. Thayer

     Recovery Officer - Engineering and Support Services

     Northeast Nuclear Energy Company

     Millstone Nuclear Station

     P.O. Box 128

     Waterford, CT 06385



OS3422 REV. 8-95





U.S. Nuclear Regulatory Commission

B16030\Page 2



(ii) Basic Component(s) Affected



     a)   The basic components which contain defects are electrical fuses

          where the ferrule separated from the fuse cartridge during

          short circuit testing.



          Gould-Shawmut Model No.            Bussmann Model No.

          A6Y2 Type 11, 10KA IR (1_/)        FRN12,    200KA IR

          A6Y5, 200KA IR*_/                  FRN-R25,  200KA IR

          TRM25, 10KA IR                     FRN-R30,  200KA IR

          A4J10, 200KA IR (2 fuses)          FRN-R35,  200KA IR

                                             FRS-R60,  200KA IR

          (*)_/ designates a QA Fuse.

          (1)_/ also identified as Type 2 or 2B in the manufacturer's 

literature.



     b)   In order to determine the extent of the issue involving these

          fuses, personnel first identified those fuses at our facility

          which showed signs of cracking in the ferrules.  These were

          identified as both QA and non-QA fuses at our facilities, and

          are designated as such below (*_/ designates a QA Fuse). 

          However, these fuses could be dedicated for QA use through

          procedural guidelines and thus each fuse with a crack had to be

          considered in our original sample.  Additionally, these fuses

          may be designated as QA components at other utilities.  The

          following is a list of fuses found to be cracked and

          subsequently tested.  Those that did not meet the test

          requirements were designated in section (ii)(a) above.



     Gould-Shawmut Model No.



     A2Y10     A2Y40*_/           A6Y3 Type II (1_/) TRM10     A2K100R

     A2Y15     A2Y60*_/           ATM3               TRM25     A2K150R*_/

     A2Y20     A6Y2*_/            ATM10              A4J3*_/   TRS4R

     A2Y25*_/  A6Y3*_/            GFN-3              A4J10     TRS80R

     A2Y30     A6Y5*_/            TRM7               OT15      TRS125R

     A2Y35     A6Y2 Type II (1_/) TRM8               A2K60R*_/ TRS61/4



     Bussmann Model No.



     FRN-8/10 FRN-R-30(2_/)        FRS-1        FRS 3-1/2   FRS-R-60(2_/)

     FRN-12   FRN-R-35             FRS 1-1/4    FRS-30(2_/) ECS 1-1/4

     FRN-R-25



     CEFCON Model No.



     CRS 1-1/4

     CRS-50 (2_/)



     (1)_/     Also identified as Type 2 or 2B in the manufacturer's

               literature.



     (2)_/     Were not tested for clearing time current test.  (Only one

               fuse available to test.)







U.S. Nuclear Regulatory Commission

B16030\Page 3



(iii)  Manufacturer Supplying Components



     Gould Electronics Incorporated

     374 Merrimac Street

     Newburyport, MA 01 950-1998

     Telephone: (508) 462-3131



     Cooper Industries

     Bussmann Division

     P.O. Box 14460

     St. Louis, MO 63178-4460

     Telephone: (314) 394-2877



     GEC Alsthom, Inc.

     4-T Skyline Drive

     Hawthorne, NY 10532

     Telephone: (201) 869-7777

     (note: Formally CEFCON and NU no longer buys these fuses)



(iv) Nature of the Defect



     On September 11, 1996, Millstone Unit 3 identified stocked safety-

     related fuses (Shawmut Amptrap Cat No.  A2Y10) that were issued from

     the storeroom for installation, had cracked (split) ferrules in the

     longitudinal direction.  Further investigation revealed numerous

     fuses, both safety and non-safety related, with this defect.  The

     fuses were not manufactured as safety-related but were either bought

     commercial grade and dedicated as safety-related by Northeast

     Utilities, or purchased safety-related from a qualified vendor that

     dedicates them.  Due to the nature of the cracks and the number of

     fuses found susceptible, functional and metallurgical evaluations

     were initiated.



     Gould Electronics Inc. and Cooper Industries (Bussmann Division)

     provided information indicating that this defect has been present

     within the fuse industry for a number of years and that fuses

     manufactured with brass ferrule material are susceptible to this

     defect.  This condition is a result of stress corrosion cracking

     (SCC) that occurs as a result of the brass ferrule material

     relieving internal stresses built up during the forming and crimping

     process, with a corrosive chemical contaminant acting as the

     catalyst.  The corrosive chemical contaminant could be credited to,

     but not limited to, solder-flux, a manufacturing surface-prep

     residue, cleaners, or other airborne contaminants.





U.S. Nuclear Regulatory Commission

B16030\Page 4





     Gould Electronics changed the ferrule material for their fuses from

     brass to copper by 1994.  Cooper Industries indicated that they

     changed the ferrule material in the fuses from brass (70% copper -

     30% zinc) to bronze (90% copper - 10% zinc) by 1985.  The new

     materials are more malleable than brass, so it is not as susceptible

     to stress corrosion cracking.



     After initiating our own independent testing of the fuses in section

     (ii)(b), our analysis found that this defect does not degrade the

     electrical continuity or the interrupting ability of the fuse.  The

     testing and acceptance requirements were taken from UL

     Specifications for fuses.  Testing completed on the fuses included:



     1) Resistance Measurements

     2) Current Carrying Capacity

     3) Clearing Time - Current Test (200% and 500% for time delay fuses)

     4) Interrupting Ability Test (Short Circuit)



     Each of the fuses tested, passed the above functional tests except

     for the interrupting ability test.  Original interrupting ability

     test put the required UL design interrupting current rating (IR)

     through the fuse.  All of the fuses interrupted the electrical

     current, however the fuses in section (ii)(a) of this report had

     ferrules physically separate from the fuse cartridge.  A second set

     of tests was performed on each of the fuses that had their ferrules

     come off, however at a lower amperage, which still encompassed our

     design criteria.  Test results were similar to the first test with

     ferrules again separating.  Consequently, the cracks could result in

     a loss of safety-related equipment due to the ferrule coming off of

     the fuse, which could then short out or damage other safety-related

     electrical distribution components.



(v)  Date on Which Defect Was Identified



     On September 11, 1996, an Adverse Condition Report (ACR) was issued

     by Millstone Unit 3 which identified safety-related fuses (Shawmut

     Amptrap Cat. No. A2Y10) that were issued from the storeroom with

     cracks (splits) in the ferrules.  During a separate routine

     surveillance of the ACR process, the Oversight organization

     identified that the investigation associated with this particular

     ACR did not adequately identify all fuses and the possible plant

     effects.  A second ACR was issued on September 25, 1996 addressing

     this concern.  Personnel assigned to address the more global issue

     drafted an action plan which included the initiation of a

     Substantial Safety Hazard evaluation and the corrective actions

     defined in section (vii) of this report.





U.S. Nuclear Regulatory Commission

B16030\Page 5



(vi) Number and Locations of Components



     This problem has been found in a wide variety of fuses (see section

     (ii) of this report).  Attachment 3 to this report contains a

     listing of affected fuses and their known location for Millstone

     Units 1 and 2.  None of the affected fuses were found in Millstone

     Unit 3.  A listing of safety-related distribution fuses and their

     known locations will be prepared as part of our planned corrective

     actions (see section (vii)(b) of this report).



(vii) Corrective Actions



     (a)  Completed



          1.   The Procurement and Warehouse groups completed inspecting

               fuses in the warehouse for cracked ferrules and then

               segregated Gould-Shawmut and Bussmann cartridge fuses on

               November 22, 1996.



          2.   A metallurgical analysis was completed on October 15, 1996

               by our Component Engineering Services.  The failure mode

               was a result of intergranular fracture caused by local

               residual stresses which were created by the forming and

               crimping process of the ferrule.  The cracks propagated

               from relieving forces due to the residual tensile stresses

               in the ferrule in the presence of a probable corrosive

               environment.  This analysis concurred with industry data.



          3.   Design Engineering and Procurement Engineering determined

               the need for independent functional testing of these

               fuses.  The results from the testing indicated that the

               fuses met their intended function of maintaining

               electrical continuity and interrupting the current during

               an overload and electrical fault.  However, during the

               interrupting ability test some fuses had ferrules

               physically separate from the fuse cartridges.  Testing was

               completed on November 14, 1996.



          4.   Procurement Engineering added two items on December 4,

               1996, to the RMSL (Restricted Material Suppliers List) to

               ensure that fuses being ordered were not manufactured

               using brass ferrules.  Suppliers will be required to

               provide the following documents:



               a)   Certificate of Conformance stating that the fuses

                    were manufactured after 1994 for Gould-Shawmut.





U.S. Nuclear Regulatory Commission

B16030\Page 6



               b)   Certificate of Conformance stating that the fuses

                    were manufactured after 1985 for Bussmann.



          5.   Procurement Engineering provided initial notification to

               both Gould Electronics Inc.  and Cooper Industries

               (Bussmann Division), concerning this issue on October 1 &

               2, 1996, respectively.  Both manufacturers indicated that

               this defect has been present within the fuse industry for

               many years and that fuses manufactured with brass ferrule

               material are susceptible to this defect.  Corrective

               actions were taken by both manufacturers to address this

               issue, by changing the design to a bronze or pure copper

               material.



          6.   Operability Determinations were completed by the Millstone

               Unit's during the week of December 9, 1996.  Each

               evaluation concluded the fuses are operable.



     (b)  Planned



          1.   Millstone Design Engineering Departments will prepare a

               listing of safety-related distribution fuses which are

               affected by this issue, along with their locations, by May

               31, 1997.



          2.   Millstone Design Engineering Departments are developing a

               process to check and replace the cracked fuses delineated

               in section (ii)(a) of this report.  This process will be

               developed by January 31, 1997.



          3.   Procurement Engineering will issue Purchase orders by

               January 31, 1997 to order replacement fuses for the

               warehouse stock.



          4.   The Units were notified on October 2, 1996, to address

               field storage locations which may have these fuses.  Fuses

               were requested to be sent back to the warehouse for

               inspection.  Damaged fuses will be pulled from these field

               storage locations by January 31, 1997.  Seabrook and

               Connecticut Yankee were also provided notification



(viii)    Other Advice For Purchasers or Licensees



          Although the Manufacturers changed to a bronze/copper material

          for ferrules, the older type fuses are still being received

          from fuse suppliers, and may be held in stock or installed by

          other licensees.





U.S. Nuclear Regulatory Commission

B16030\Page 7



     It should be noted that the fuse clips used during the testing were

     an open ended type to assist the test lab in determination whether

     the ferrule had moved during the test.  This should be a factor that

     should be considered when evaluating specific applications since

     this may vary from the particular design installation at each unit.



Should you have any questions regarding this submittal, please contact

Mr.  James M. Peschel at (860) 437-5840.



                              Very truly yours,



                              NORTHEAST NUCLEAR ENERGY COMPANY



                              Jay K. Thayer

                              Recovery Officer

                              Engineering and Support Services



cc:  H. J. Miller, Region 1 Administrator

     W. D. Travers, Dr., Director Special Projects

     A.C. Cerne, Senior Resident Inspector, Millstone Unit No. 3

     V. L. Rooney, NRC Project Manager, Millstone Unit No. 3





                                                  Docket No. 50-245

                                                             50-336

                                                             50-423

                                                             B16030



                              Attachment 1



            Millstone Nuclear Power Station Nos. 1, 2, and 3



                                                            December 1996





U.S. Nuclear Regulatory Commission

B16030\Attachment 1\Page 1



                                Enclosure

                     List of Regulatory Commitments



The following table identifies those actions committed to by NNECO in

this document.  Any other actions discussed in the submittal represent

intended or planned actions by NNECO.  They are described to the NRC for

the NRC's information and are not regulatory commitments.  Please notify

the Manager - Nuclear Licensing at the Millstone Nuclear Power Station

Unit No.  3 of any questions regarding this document or

any associated regulatory commitments.



               Commitment                              Committed Date or

                                                             Outage



B16030-1  A listing of safety related distribution        May 31, 1997

          fuses affected by this issue, and their

          locations, will be prepared.



B16030-2  A plan to check and replace cracked fuses    January 31, 1997

          as delineated in Section (ii)(b) will be

          developed for each Millstone Unit.



B16030-3  Issue Purchase Orders for replacement        January 31, 1997

          fuses



B16030-4  A verification of field storage locations    January 31, 1997

          will be completed to determine if fuses

          have been returned to the warehouse.





                                                  Docket No. 50-245

                                                             50-336

                                                             50-423

                                                             B16030



                              Attachment 2



             Millstone Nuclear Power Station Nos. 1, 2 and 3



                                                            December 1996





                    Northeast Nuclear Energy Company

                    SUBSTANTIAL SAFETY HAZARD REPORT

                            November 22, 1996



In accordance with 10 CFR 21.21(d)(3)(i), Northeast Nuclear Energy

Company (NNECO) is providing notification to the NRC via this facsimile

and concurrent telephone conversation, regarding a potential Significant

Safety Hazard (SSH) identified at Millstone Station.



o    Fifteen different fuse types from three different manufactures

     (Gould-Shawmut, Bussmann, and CEFCO) were found to have axial

     cracks.  The cracks occurred as a result of the brass ferrule

     relieving internal stress.



o    During communications with manufacturers, it was determined that

     these defects have been present within the fuse industry for many

     years and that fuses manufactured with brass are susceptible to this

     defect.



o    NNECO determined that functional testing should be performed on a

     sample of the fuses.  The results from the testing indicated that

     the fuses met their intended function of interrupting the current,

     however ten out of forty six fuses had ferrules physically blow off

     the end.  The following is a list of those fuses that the ferrule(s)

     came off the end.



          Gould-Shawmut                      Bussmann



          A6Y2 Type II, 10KA IR              FRN 12, 200KA IR

          A6Y5, 200KA IR                     FRN-R25, 200KA IR

          TRM25, 10KA IR                     FRN-R30,200KA IR

          A4J10, 200KA IR (2)                FRN-R35, 200KA IR

                                             FRS-R60, 200KA IR



Conclusion



The cracks could result in a loss of safety-related equipment due to the

ferrule coming off of the fuse, which could then short out or damage

other safety-related electrical distribution.  This could be a SSH

concern that should be reported through 10CFR21, with notification to

other utilities due to the generic nature of the basic component.



If you have any questions regarding this information, please contact Mr. 

James M. Peschel at (860) 437-5840.  In accordance with 10CFR

21.21(d)(3)(ii), a written report will be provided within 30 days.





                                                       Docket No. 50-245

                                                                  50-336

                                                                  50-423

                                                                  B16030



                              Attachment 3



             Millstone Nuclear Power Station Nos. 1, 2 and 3



                                                            December 1996





U.S. Nuclear Regulatory Commission

B16030\Attachment 3\Unit 1


Table "Millstone Unit 1 Locations of Fuse Types Where Cracked Ferrules Separated During Testing"

Fuse Location (Panel) Fuse Manufacturer Model Amps System
CD4B-1H Gould A4J 10 Liquid Radwaste
CD4B-1H Gould A4J 10 Liquid Radwaste
E3-3D Gould A4J 10 LPCI
E3-3D Gould A4J 10 LPCI
E3-4D Gould A4J 10 Core Spray
E3-4E Gould A4J 10 Core Spray
F-E3-2B Gould A4J 10 LPCI
M7-26B DISC SW Bussmann FRS-R 60 Well Water Pump
M7-26B DISC SW Bussmann FRS-R 60 Well Water Pump
M7-26B DISC SW Bussmann FRS-R 60 Well Water Pump





U.S. Nuclear Regulatory Commission

B16030\Attachment 3\Unit 2



                Millstone Unit 2 Locations of Fuse Types

             Where Cracked Ferrules Separated During Testing



                       (See Attached Fuse Listing)



Table "MP2 FUSE LIST"

Fuse Listing 

Fuse 1

Fuse 2

Fuse 3

Fuse 4

Fuse 5

Fuse 6

Fuse 7

Fuse 8

Fuse 9

Fuse 10

Fuse 11

Fuse 12

Fuse 13

Fuse 14

Fuse 15

Fuse 16

Fuse 17

Fuse 18

Fuse 19

Fuse 20

Fuse 21

Fuse 22

Fuse 23

Fuse 24

Fuse 25

Fuse 26

Fuse 27

Fuse 28

Fuse 29

Fuse 30

Fuse 31

Fuse 32

Fuse 33

Fuse 34

Fuse 35

Fuse 36

Fuse 37

Fuse 38

Fuse 39

Fuse 40

Fuse 41

Fuse 42

Fuse 43

Fuse 44

Fuse 45

Fuse 46

Fuse 47

Fuse 48

Fuse 49

Fuse 50

Fuse 51

Fuse 52

Fuse 53


U. S. Nuclear Regulatory Commission
B16030\Attachment 3\Unit 3



                Millstone Unit 3 Locations of Fuse Types

             Where Cracked Ferrules Separated During Testing



     Fuse Location      Fuse

        (Panel)     Manufacturer   Model     Amps      System



None of the fuses        N/A       N/A       N/A         N/A

noted in Section

 (ii)(a) whose

  ferrules had

 separated, are

  known to be

 installed on

Millstone Unit 3.




*** END OF DOCUMENT ***


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