ENS 55282: Difference between revisions
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| NRC officer = Kerby Scales | | NRC officer = Kerby Scales | ||
| event date = 05/28/2021 00:00 EDT | | event date = 05/28/2021 00:00 EDT | ||
| last update date = | | last update date = 09/23/2021 | ||
| title = Part 21 Report - Vacuum Breakers Failure to Close | | title = Part 21 Report - Vacuum Breakers Failure to Close | ||
| event text = The following is a summary of the report provided by Framatome Inc.: | | event text = The following is a summary of the report provided by Framatome Inc.: | ||
| Line 32: | Line 32: | ||
Office (434-832-3347) | Office (434-832-3347) | ||
Mobile (434-841-0306) | Mobile (434-841-0306) | ||
| URL = https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2021/ | * * * UPDATE FROM GAYLE ELLIOT TO HOWIE CROUCH AT 1538 EDT ON 9/23/21 * * * | ||
The following information was received from Framatome via email: | |||
The preliminary evaluation determined a modification of the breakers was required to increase the torsion spring force acting on the close latch. Framatome worked with Siemens to develop an interim and long-term solution. The interim solution utilized a revised spring retaining bracket that could be deployed near-term. The original long-term solution was a new torsion spring design which applied approximately 40 percent more torsional force on the trip latch. | |||
Following a reoccurrence of the failure-to-close issue, Framatome and Siemens identified the root cause of the trip latch bounce and [determined] the associated corrective actions. The solution developed will mitigate all main failure to close causes (low power to the closing mechanism, insufficient time for the trip latch to drop, and improper trip latch to jackshaft interaction) for the 5kV replacement circuit breakers. The solution consists of the following: | |||
1) Circuit breakers comply with the following revised design performance parameters: | |||
a. Jackshaft rotational speed (C speed #2) | |||
b. Jackshaft overtravel | |||
c. Jackshaft overtravel duration | |||
2) Circuit breakers have the new torsion spring installed | |||
3) Circuit breakers meet the revised bump stop gap | |||
By increasing the bump stop gap, the jackshaft is now able to rotate further before it hits the bump stop. This reduces the amount of force transferred to the bump stop and in turn the operating mechanism. This reduction significantly reduces the amount of latch bounce for this breaker design. | |||
St. Lucie was first notified of this 10CFR21 reportable defect on May 28, 2021 by Framatome Inc. via telephone and email. | |||
Notified R2DO (Miller) and Part 21 group via email. | |||
| URL = https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2021/20210924en.html#en55282 | |||
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{{ENS-Nav}} | {{ENS-Nav}} | ||
Latest revision as of 06:30, 24 September 2021
| Where | |
|---|---|
| Framatome Inc. Lynchburg, Virginia (NRC Region 1) | |
| Organization: | Framatome Anp |
| Reporting | |
| 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
| Time - Person (Reporting Time:+12.6 h0.525 days <br />0.075 weeks <br />0.0173 months <br />) | |
| Opened: | Gayle Eliott 16:36 May 28, 2021 |
| NRC Officer: | Kerby Scales |
| Last Updated: | Sep 23, 2021 |
| 55282 - NRC Website
| |