Junk Plant Browns Ferry SRVs: Where Has Science And Engineering Gone In These Plants

These guys have repeatedly put different exotic coating on these valve over the past decade. Platinum was just the latest coating that emediately failed upon first use. So now they experimented on the failed platinum coating by doing some kind of new surface preparation. So now the original platinum failed, then the platinum and new surface preparation emediately failed in a worst way (platinum anti-corrosion coatings flaking off). It happens all the time with the new coating failing worst than the last coating or fix. 

In my old days, you never did any experimentations in a commercial nuclear plant. You would comprehensively test the coating, material and component in a laboratory under the same or worst condition (environment)the material was going into the plant. And there would be hell to pay by the NRC if any surprises showed up in plant after the stringent laboratory testing.              

Licensee Event Report 50-296/2018-004-00 

10 CFR 50.73
The enclosed Licensee Event Report provides details of the inoperability of three Main Steam Relief Valves for longer than allowed by plant Technical Specifications. The Tennessee Valley Authority is submitting this report in accordance with Title 10 of the Code of Federal Regulations 50.73(a)(2)(i)(B), as any operation or condition which was prohibited by the plant's Technical Specifications

On May 17, 2018, the Tennessee Valley Authority was presented with as-found testing results indicating that three of the thirteen Main Steam Relief Valves (MSRVs) from Browns Ferry Nuclear Plant, Unit 3, were outside the +/- 3 percent setpoint band required for their operability. Troubleshooting determined that the three MSRV discs failed by corrosion bonding to their valve seats. The valve discs were previously platinum coated to prevent this, and this was the first Unit 3 MSRV service interval to implement an improved surface treatment to prevent coating delamination.
These three MS RVs were found to have been inoperable for an indeterminate period of time between March 26, 2016, and February 17, 2018, which is longer than permitted by Technical Specifications (TS). The affected valves remained capable of maintaining reactor pressure within American Society of Mechanical Engineers code limits. Additionally, the valves' ability to open under remote-manual operation, activation through the Automatic Depressurization System, or MSRV Automatic Actuation Logics were not affected. The valves remained capable of performing their required safety function.
The valves failed to open within their TS required limits due to the valve discs corrosion bonding to their seats, as a result of their platinum anti-corrosion coatings flaking off. The immediate corrective action was to replace all thirteen of the Unit 3 MSRV pilot valves with refurbished valves during the Unit 3 Refueling Outage 18. The corrective action was to ensure pilot discs are prepared for platinum coating in accordance with the revised procedure which requires nitrogen pressure testing to verify valve seal functionality prior to coating.
NRC