Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
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 ***
