Usually the problem is the tip that got slightly loose and the signal is now intermittent or null. IIRC, when we detected the wrong wire we had to put it in a box and the guy in charge of the lab equipment would fix it later.
I’m not looking forward to thermal vacuum testing for my robots… because I don’t think there’s a big enough chamber in Australia… option one is (assuming funding) building a thermal vacuum chamber that can get down to GEO level vacuum with all the fun a large volume vacuum system entails… option two is shipping the entire thing to a friendly country with larger chambers (ESA in EU or NASA in the USA) but then there’s the space technology export paperwork … and I don’t know which would be worse.
The grad students and postdocs are sacrificed... for science!
Leaks in liquid metal fast reactors are much more obnoxious but still manageable. Sodium catching on fire when it hits air frequently isn't as bad as it sounds (a "pool fire" isn't particularly hot or dangerous but a "spray fire" can be) but it is important to catch sodium leaks quickly without false alarms and many development projects had trouble with that.
I always enjoy the handwaving by nuclear enthusiasts. These are some of the most difficult engineering systems routinely built and operated by mankind, where a coolant loss accident doesn't just destroy the reactor but can turn the facility into a multi-billion dollar cleanup effort in minutes.
What was most shocking about the fire at Monju wasn't that it happened but that they tried to cover it up. Neither that nor the incident where they dropped the refueling machine into the reactor vessel were dangerous to people off site but the latter sure convinced everyone they didn't know what they were doing.
Contrast that to Superphenix where the fuel transfer drum failed and they struggled with a steam turbine system that was procured under corrupt contracts but overall had a good operational record. Or the three pre-1970s cases where there was significant fuel damage in the US but they found that a core melt in a LFMBR isn't as bad as it sounds because the iodine (most dangerous radioactive element in the fission products) reacts with the sodium and the NaI dissolves in the sodium so it doesn't go anywhere. Or EBR-II and the FFTF which performed flawlessly, or the highly successful fast reactors in Russia.
For both systems there have been catastrophic accidents that were national tragedies, from which we learned a lot. "The rules of aviation are written in blood," and that is also true for reactors. Past failures like the one you linked don't mean that reactors are unsafe; if anything, because we had that failure to learn from, reactors are now much safer. If we had a volatile technology like nuclear reactors and none of them had ever had any accidents, then I would be very hesitant to have one in my home town since it could very well be the first to ever blow up.
I think the reason they have seen a lot of success where nuclear reactors haven't is simply up to the fact that they are both cheaper to build and that the public can very directly see where the benefit to them comes from, whereas nuclear power is abstract and indistinguishable from coal to the average person.
The consequences of aeroplane disaster are localised in space (to the immediate vicinity of the vehicle and whatever it crashes into) and time (once the crash has happened, it is more or less over).
Nuclear disasters can have global effects, and can last for decades.
I'm cautiously pro-nuclear in theory, but am awestruck by the incredible forces unleashed and the extreme impact they can have when mishandled. It's far more potent than anything merely mechanical.
But anyway, leaks of radioactive materials are inherently much easier to detect than other kinds of leaks because they are radioactive. Every major hospital in the developed world has a radiation safety department or equivalent performing regular leak and contamination testing in association with scintigraphy and brachytherapy, but this has not prevented the widespread use of radionuclides in medicine.
The notion of "contaminat[ing] everything they touch" is also a misconception that the radiation protection community has tried to combat for decades: radiation is only a meaningful hazard insofar as it reaches levels comparable to the natural background radiation produced by 40K, 14C, and other sources pervasive in the natural environment. There is therefore a level of dilution beyond which radioactive contamination ceases to be of meaningful concern, just as is true with all other toxic substances.
Source: as a medical physicist in training, I work with a radiation safety department at a major US hospital.
The things we humans put up with to try and understand the universe!
2 evaporator coil leaks in my 5 year old house already, another one currently suspected.
It seems they already make a product for that - vacuum grease. It can get sucked into even a fairly large crack, and plug it up, as long as the depth of the crack is much longer than the width, then atmospheric pressure won't provide enough force to send it deeper into the crack.
And the grease itself is designed not to evaporate into the vacuum.
Whats wrong with using that?
Stuff like paint will tend to be very permeable- if it relies on a solvent drying out, then obviously its permeable enough to let the solvent through. Even if it does dry to a very solid state, there will be a very very long tail of evaporation of volatiles inside the substance.
> It seems they already make a product for that - vacuum grease.
Vacuum grease isn't perfect- it's not recommended for the high end of high vacuum or for UHV. Or for single digits of kelvin.
Another big factor is that if you're doing science, you probably want to go out of your way to eliminate contamination like that. Guessing about the possible chemical interactions of a secret proprietary substance under extremely low temperature and pressure is not a fun way to get your doctorate.
In cryogenic environments this is less of an issue because things are more sticky, but in a room temperature apparatus targeting ultra high vacuum this is troublesome or impossible.
Hydrogen is EXTREMELY small, the temps the poster is talking about are very very low, and XHV/UHV is extremely low pressure vacuum.
Like 'single molecules we don't want rattling around is a problem', 'more vacuum than outer space vacuum', and 'oxygen long ago turned into a solid' temperatures.
But like similar last-ditch repairs (think automobile muffler tape or radiator sealant), they only occasionally last. Usually the best thing to do is to go actually fix the problem.
The above advice assumes you're trying to maintain high vacuum (10^-5 torr or lower pressure). At low vacuum (10^-3 torr and above), that trickery can work wonders.
If you have a big aluminum chamber under ultra low pressure, guess what you're concentrating in there? Hydrogen and helium from the atmosphere that's seeping through your metal. Crazy stuff that's (sadly) not fixed by slapping PTFE paste or vacuum grease onto it.
https://www.tedpella.com/vacuum_html/High_Vacuum_Leak_Sealan...
The whizz sound leak checkers make is good fun.
If they have a PCB oscillator, the gas will seep its way in there and cause a clock failure.
Even worse, some leaks would only show up when the system got cooled down to liquid Helium temperature. When that happened you were out of luck as you can't cool the system down to 4K before spraying it with Helium, so you had to just guess where the leak might be and replace all seals in that area until you found the right one. Going even deeper in temperature would eventually turn the He4 suprafluid, which means that it loses all internal friction. In that state it would squeeze through even the tiniest molecular cracks, so again if that happened you just had to redo all the seals and hope they would hold.