ENS 42021
ENS Event | |
|---|---|
05:00 Sep 23, 2005 | |
| Title | Material Defect Report |
| Event Description | The licensee provided the following information via facsimile:
Pursuant to 10 CFR Part 21, this letter notifies the NRC of the existence of a possible defect in Bussmann KWN-R fuses. The defect is a poor solder connection of the fuse link assembly to the rejection ferrule. The defect applies potentially to all KWN-R fuses. An evaluation was performed and determined that this defect can create a substantial safety hazard or contribute to circumstances that would exceed safety limits as defined in the technical specifications of a license issued pursuant to 10CFR50. Safety-related circuits that include fuses with this defect may not be able to perform their safety-related function as required during a design basis event. Therefore, this potential defect is reportable per 10 CFR Part 21. DESCRIPTION OF ANOMALY: The customer reports that the fuse lost electrical continuity while in service. The customer cut the fuse open and found the fuse element intact and a lack of electrical continuity across the soldered connection of the element to the rejection ferrule of the fuse. According to the customer, the fuse had been in service since 3/31/05 carrying 2 - 3 amperes, and there were no overcurrent events which caused the fuse to open. DISPOSITION - COMMENTS - RECOMMENDATIONS: The customer returned the fuse to Wyle for failure analysis. Wyle forwarded the fuse to the manufacturer for evaluation. The manufacturer found a poor solder connection on the rejection cap. Apparently the cap did not get hot enough to reflow solder during the manufacturing process. The manufacturer stated the issue could be isolated to this particular fuse due to placing it in an incorrect bin, but the issue may extend to other fuses due to a process problem. Based on the evaluation, a potential defect exists in other KWN-R fuses. As a screening test to ensure a good soldered connection, the manufacturer recommends performing a Current Carrying Capacity Test for 30 minutes at 110% of rated current after warm up at 100% of rated current. This anomaly impacts qualification of KWN-R fuses. Only KWN-R fuses that pass the 110% Current Carrying Capacity Test are qualified.
The manufacturer provided the following information via fax: This letter provides an update to the referenced letter that Wyle submitted to the NRC on the above subject [on 09/27/05] The KWN-R fuses affected are limited to [less than or equal to] 30 amps. KTN-R fuses [less than or equal to] 30 amps are added to the referenced Part 21 notification since these fuses are manufactured using the same process as the KWN-R fuses. Thus far, poor solder joints have been found in 3, 6, and 10 amp KWN-R fuses. In addition to the date codes previously mentioned (L05, M37, M17), poor solder joints have also been found in date codes L11, L19, M07, M20, M40. Poor solder joints have also been found in 3, 4, 5, and 15 amp KTN-R fuses of the 1987-1991, vintage (no date code on fuses). When performing the 110% Current-Carrying Capacity Test, the fuses should be warmed up at 100% until their temperature and the voltage drop across them are stable before applying 110% current to avoid blowing the fuses. A mechanical drop test has been added to the KWN-R and KTN-R manufacturing process. This drop test should be added to the screening process. The drop test consists of: 1. Measure and record the fuse resistance. 2. Drop the fuse though a 3 foot pipe onto a laminated workbench onto the non-rejection end of the fuse. 3. Measure the fuse resistance after the drop. 4. Acceptance Criteria: Fuse resistance should be the same resistance after the drop (+/- 10%) and within the manufacturer's specified range. Notified R1DO (Perry), R2DO (Payne), R3DO (Lipa), R4DO (Spitzberg), and NRR (Tabatabai) |
| Where | |
|---|---|
| Bussmann Huntsville, Alabama (NRC Region 1) | |
| Organization: | Wyle Laboratories |
| Reporting | |
| 10 CFR 21.21 | |
| Time - Person (Reporting Time:+108.65 h4.527 days <br />0.647 weeks <br />0.149 months <br />) | |
| Opened: | Bruce Bateman 17:39 Sep 27, 2005 |
| NRC Officer: | Bill Gott |
| Last Updated: | Jan 25, 2006 |
| 42021 - NRC Website | |
Bussmann with 10 CFR 21.21, Notification of failure to comply or existence of a defect and its evaluation | |
WEEKMONTHYEARENS 420212005-09-23T05:00:00023 September 2005 05:00:00
[Table view]10 CFR 21.21, Notification of failure to comply or existence of a defect and its evaluation Material Defect Report 2005-09-23T05:00:00 | |