ENS 50495
ENS Event | |
|---|---|
19:55 Sep 23, 2014 | |
| Title | Part 21 Report - Electromatic Relief Valve Excessive Wear |
| Event Description | The following report was received via e-mail:
This is a non-emergency notification from Oyster Creek Nuclear Generating Station (OCNGS) required under 10 CFR Part 21 concerning the design of Electromatic Relief Valve (EMRV) actuators. On June 20, 2014, during as-found bench (stroke) testing of the EMRV actuators removed from the plant during refueling outage 1R24 (October 2012), two of five EMRV actuators failed to operate. Subsequent inspection of these actuators found unexpected wear of the posts (grooves approximately 1/2 inch from the top), springs (thinned and broken at the top), and guides (grooves inside), with one spring having a piece axially wedged between the post and the guide. The root cause of this failure was determined to be the inadequate design of the EMRV actuators in that when placed in an environment where the actuator is subject to the vibration associated with plant operation, the allowed installation tolerances between posts and guides can create a condition where the springs can jam the actuator plunger assembly by wedging between the guides and the posts. If the EMRV actuators are set up in a condition where the posts are not optimally aligned, preferential wear of the post is observed due to interaction of the post, spring, and guide. Additionally, the vendor guidance for refurbishment of the EMRV actuator does not provide the necessary acceptance criteria for alignment of the posts to guides to ensure that the springs, posts, and guides do not interact in a way that causes preferential wear of the post allowing the jamming mechanism to exist. By OCNGS process, the EMRV actuators are refurbished with new springs, posts, guides, and microswitches every 24 months during refueling outages due to the known wear of these parts. The actuator inspection/refurbishment frequency of 24 months exceeds the manufacturer's (i.e., Dresser Industries) recommended frequency of 36 months (per Vendor Manual VM-OC-0030, Installation and Maintenance Manual for Electromatic Relief Valves, Revision 1,Section VII, Ref. 4.5). In addition, in 2008, the station implemented the manufacturer's recommended material changes intended to minimize part wear, and prevent potential actuator failures. Identification of Facility and Component: Oyster Creek Nuclear Generating Station / Electromatic Relief Valve Actuator, Dresser Valve Type 6 inches Model 1525-VX Identification of Component Manufacturer and/or Supplier: Dresser Industries. Nature of Defect: Inadequate design of the EMRV actuators in that when placed in an environment where the actuator is subject to the vibration associated with plant operation, the allowed installation tolerances between posts and guides can create a condition where the springs can jam the actuator plunger assembly by wedging between the guides and the posts. Safety Significance (e.g., substantial hazard that is or could be created): Identified condition is a Substantial Safety Hazard since it could cause EMRV to be inoperable, which could result in a loss of safety function. Date of Discovery of Initial Condition (taken from the IR): 06/20/14 Date of Discovery of the Substantial Safety Hazard (date of approval of the technical evaluation): 09/22/14 Recommended Actions: Change the design to mitigate the cause of the actuator parts (i.e., springs, guides and posts) interacting which results in unexpected wear due to vibration induced fretting. Number and Locations of All Defective Components: Two EMRVs located in the Drywell on the Main Steam piping. Any Advice Related to the Defect: Consider actuator design change if vibration conditions at the valve location results in unexpected wear of the EMRV actuators. Perform actuator as-found stroke testing before removal for refurbishment to determine in situ operability of the component. With current design, ensure posts are aligned such that preferential wear does not occur. Spring should be optimally centered on the guide and the post and guide should be equidistant around the full circumference of the bushing. Contacts (Name, Title, Location, Phone Number, etc.): Sylvain L. Schwartz, Senior Staff Engineer, Oyster Creek Nuclear Generating Station, Phone: (609) 971-4558, Email: sylvain.schwartz@exeloncorp.com The licensee notified the NRC Resident Inspector. Plants with similar Dresser EMRVs: Nine Mile Point, Quad Cities, and Dresden. |
| Where | |
|---|---|
| Oyster Creek New Jersey (NRC Region 1) | |
| Reporting | |
| 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
| LER: | 05000219/LER-2014-002 |
| Time - Person (Reporting Time:+44.67 h1.861 days <br />0.266 weeks <br />0.0612 months <br />) | |
| Opened: | Jeremy Sharkey 16:35 Sep 25, 2014 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Sep 25, 2014 |
| 50495 - NRC Website
Loading map... {"minzoom":false,"maxzoom":false,"mappingservice":"leaflet","width":"350px","height":"250px","centre":false,"title":"","label":"","icon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"zoom":6,"defzoom":14,"layers":["OpenStreetMap"],"image layers":[],"overlays":[],"resizable":false,"fullscreen":false,"scrollwheelzoom":true,"cluster":false,"clustermaxzoom":20,"clusterzoomonclick":true,"clustermaxradius":80,"clusterspiderfy":true,"geojson":"","clicktarget":"","imageLayers":[],"locations":[{"text":"\u003Cb\u003E\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003E\u003Ca class=\"mw-selflink selflink\"\u003EENS 50495\u003C/a\u003E - \u003Ca href=\"/Oyster_Creek\" title=\"Oyster Creek\"\u003EOyster Creek\u003C/a\u003E\n\u003C/p\u003E\u003C/div\u003E\u003C/b\u003E\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003EPart 21 Report - Electromatic Relief Valve Excessive Wear\n\u003C/p\u003E\u003C/div\u003E","title":"ENS 50495 - Oyster Creek\n","link":"","lat":39.81436111111111,"lon":-74.20560833333333,"icon":""}],"imageoverlays":null} | |
Oyster Creek with 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
WEEKMONTHYEARENS 504952014-09-23T19:55:00023 September 2014 19:55:00
[Table view]10 CFR 21.21(d)(3)(i), Failure to Comply or Defect Part 21 Report - Electromatic Relief Valve Excessive Wear 2014-09-23T19:55:00 | |