Safety Relief Valves SRVs melted In Fukushima

updated 12/18

Main Steam Safety Relief Valves Buna-N thread seals

I was coached the regs says the drywell environmental design temp is 340 degrees.

I think the original SRV manufacture had the actuator design seals high temp consideration right. It speaks to how unthoughtful we have become with the design of safety equipment and replacement parts. The first swipe in designs stated the replacement seal was required to be asbestos. Who even cares what temperatures the drywell got with the severely temperature resistant asbestos.

I have written a lot up on VY SRV actuator problems in the final years of the plant. Got a 2.206 on it. Just do a goggle search on popperville, Vermont Yankee, Safety Relief Valves and buna-n or some combination. 

***This reminds me of the Buno-n material they put in the Vermont Yankee's SRV actuators. Basically only qualified to 140 degrees when they needed 400 degrees in it. Mysteriously put in type II valves when it should have been type 1 valves. VY did this intentionally and the NRC allowed them to get away with it.

Collectively and systemically I feel the industry and the NRC has been undermining safety environmental qualification across the board for many years now.   

Safety Relief Valves melted In Fukushima. 

Delay in cooling Fukushima reactor possibly due to melted rubber, says Tepco

Kyodo

• Dec 17, 2015

The injection of water to cool one of the reactors that suffered meltdowns at the Fukushima No. 1 nuclear complex in 2011 was delayed because the rubber parts in valves used to reduce reactor pressure had possibly melted, the plant operator said Thursday. 

According to Tokyo Electric Power Co., the component that may have melted is part of a device used to open the so-called safety relief valve when steam building up inside the reactor pressure vessel needs to be released in an emergency. 

Tepco had been unable to explain why workers faced difficulty opening the safety relief valves of the No. 2 reactor, but the company now says “one of the reasons” may have been because the component melted and was not able to function properly. 

The temperature limit for the component was about 170 degrees Celsius, but Tepco found it was able to withstand that level of temperature for only several hours. 

The nuclear crisis began on March 11, 2011, when earthquake-triggered tidal waves hit the plant, flooding electrical equipment and leading to the loss of reactor cooling systems. 

The system that had kept cooling the No. 2 reactor ceased on March 14. Workers sought to inject water by using fire trucks, but could not do so because the pressure inside the reactor was too high. 

Tepco thus sought to open the eight safety relief valves by using battery power, but the operation did not go smoothly. After several attempts the valves were finally opened, enabling water to be poured inside the reactor. 

For a safety relief valve to open, it needs to be supplied with nitrogen gas through another valve, to which the rubber component in question is attached. But nitrogen gas might have leaked when the component melted, Tepco said.