Point me to these studies, please.
Regardless of where the temp sensors are placed on the RPV, if the steel of the RPV became hot enough to melt through at any point on the RPV, you wouldn’t be seeing any temp readings in the sub-100C range. The melting point of steel is 1400C+, the thermal conductivity of steel is pretty good, which means that the sensors up top would have shown a significant upwards departure if the core were melting through the bottom.
This is the sort of stuff that really annoys us engineers. People don’t think about what/how the whole system would be acting if these apocalyptic events came to pass. As a result of this thread, I went back and looked at the temp readings on the various reactors and it looks like they achieved cold shutdown. Do they have problems? Heck yes. They have thousands of tons of contaminated cooling water to dispose of, for starters. The place is still a collection of large-scale wrecks. They still have seismic hazards from an apparent increase in quake activity over the long-term in their area.
But this constant “the world is going to end!” stuff spouted by non-engineers since the beginning.... is just so tedious. Even IF (and I don’t expect it to happen by a long shot) there were a core melt-through event, the planet will be just fine. Consider how much worse events the planet has survived before this. There’s nothing man-made that can compare to something like a super-volcano blowing up - not even if you dug a hole and dumped every nuke weapon into it could you duplicate what will happen when the Yellowstone Caldera blows it’s top.
The Russians blew up a 50 MEGA-ton bomb during the era of above-ground nuke testing. And we’re still here. 50 MT is a big firecracker. Really big. Lots of fallout. We’re still here.
Consider for a moment how the sensor data showed itself during the Columbia space shuttle disaster for an example of what I speak. First they noticed some hydraulic actuator temps going high - abnormally high for that point in the mission. Then they noticed yet more temp sensors go high. Then they noticed other temp sensors go “low, off-scale” - probably as a result of the destruction of the sensors. Then temps in the wheel wells went ape. Then... nothing.
It started as one little punch-through in the leading edge of a wing... but the impending doom was seen in cascade of sensor information. The shuttle didn’t just go from a shuttle to a collection of melted-down bits in the blink of an eye. The telemetry told the tale of the disaster’s progress.
If a melt-through actually were to happen at Fukushima, you’d see similar results in the telemetry. And we’re just not. I don’t understand how anyone could make the claim that we’re going to see an event like that happen and yet we’re not going to see confirmation on more than one sensor....