Our experiment (like the XENON experiments) used liquid xenon. The boiling point is roughly -110 °C, so it requires cooling to stay liquid. If that cooling had failed, the xenon would have started to boil and turn to gas. Gaseous xenon takes up something like 300x more volume than liquid.
So we had a few things to deal with this. We had some pretty giant UPSes to provide backup power. Imagine a shipping container filled with lead acid batteries. That was enough to keep the cooling running for about a day. During that time, we would start recovering the xenon. That would involve running compressors to stuff it back into bottles before power ran out. We also had a limited ability to cryopump the xenon out. Cryopumping involves cooling a gas cylinder (usually with liquid nitrogen) so the gas condenses inside. But that was always limited by the amount of LN we had on hand, which wasn't much.
But suppose we couldn't get all the xenon back into the cylinders before power ran out, or if our compressors failed. First, our detector would have failed. It was made of thin copper to reduce radioactivity. The xenon would have mixed with the HFE (Novec) fluid we were using for coiling. After that, as the xenon continued to boil, it would have burst some burst disks built into the system. And those were connected to the balloon.
The "balloon" was some plastic material, about 10x10x20 meters that we had stashed in an alcove off to the side of our experiment. It would have hopefully contained the xenon.
Since we never had to use it, I'm not completely sure what the process would have been. We would have shipped it off to some industrial gas facility, and they have the equipment to distill it out. And then we'd probably have to spend more time purifying it ourselves.
I doubt such a thing has ever been used. Most experiments, even underground ones, weren't dealing with the constraints we were. The mine we were in wasn't dedicated to science, and a dedicated facility would have had better support. For example, we couldn't run generators to deal with a power failure because there were limits to how much diesel equipment could be running underground with only natural ventilation, and the ventilation fans didn't have backups. Likewise, a dedicated facility would have had a better supply of liquid nitrogen. We only had one portable dewar, rather than a large tank.
Our experiment (like the XENON experiments) used liquid xenon. The boiling point is roughly -110 °C, so it requires cooling to stay liquid. If that cooling had failed, the xenon would have started to boil and turn to gas. Gaseous xenon takes up something like 300x more volume than liquid.
So we had a few things to deal with this. We had some pretty giant UPSes to provide backup power. Imagine a shipping container filled with lead acid batteries. That was enough to keep the cooling running for about a day. During that time, we would start recovering the xenon. That would involve running compressors to stuff it back into bottles before power ran out. We also had a limited ability to cryopump the xenon out. Cryopumping involves cooling a gas cylinder (usually with liquid nitrogen) so the gas condenses inside. But that was always limited by the amount of LN we had on hand, which wasn't much.
But suppose we couldn't get all the xenon back into the cylinders before power ran out, or if our compressors failed. First, our detector would have failed. It was made of thin copper to reduce radioactivity. The xenon would have mixed with the HFE (Novec) fluid we were using for coiling. After that, as the xenon continued to boil, it would have burst some burst disks built into the system. And those were connected to the balloon.
The "balloon" was some plastic material, about 10x10x20 meters that we had stashed in an alcove off to the side of our experiment. It would have hopefully contained the xenon.
Since we never had to use it, I'm not completely sure what the process would have been. We would have shipped it off to some industrial gas facility, and they have the equipment to distill it out. And then we'd probably have to spend more time purifying it ourselves.
I doubt such a thing has ever been used. Most experiments, even underground ones, weren't dealing with the constraints we were. The mine we were in wasn't dedicated to science, and a dedicated facility would have had better support. For example, we couldn't run generators to deal with a power failure because there were limits to how much diesel equipment could be running underground with only natural ventilation, and the ventilation fans didn't have backups. Likewise, a dedicated facility would have had a better supply of liquid nitrogen. We only had one portable dewar, rather than a large tank.