Years ago I asked some technically-adept SF fans I know how you would design a "forever" emergency light. The limitation on those which use phosphors to transmute other radiation into visible light is that the phosphors eventually degrade. (Part of the reason the Pioneer and Voyager probes are losing power is the degradation of the heat engines. The PU-238 heat source used in their radio-thermal generators has a half-life of 88 years.)
Part of the problem with making a forever light is that very few radioactive materials glow on their own, so they need phosphors. Most of those currently used - even with phosphors - have short half-lives (for example, the half life of radium-226 is around 1,600 years; tritium is around a piddling 12 years). So you need a durable, probably non-crystalline phosphor efficient for the type of radiation the source gives off. It can be done. There is actually a lot of reference material out there for self-luminous signs. However, those are only rated in years and not millennia. Something lasting thousands of years would likely require quite a bit of materials research, if only to make sure nothing dangerous is likely to escape.
As for working while red hot, for really hot operating conditions you probably want ceramics. Adolph Coors, besides making beer, have long had a business of making laboratory-grade ceramics. Back in the late-Fifties to early-Sixties they were involved in a project to produce a half-gigawatt, air-cooled fission reactor. They developed pneumatically-operated, ceramic actuators designed to operated while white hot. The government reactor project was cancelled before completion, but today the descendants of those actuators are still used in some steel mills.
Which gives me the mental image of fluidic circuits in ceramic media operating somewhere very hot.
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Part of the problem with making a forever light is that very few radioactive materials glow on their own, so they need phosphors. Most of those currently used - even with phosphors - have short half-lives (for example, the half life of radium-226 is around 1,600 years; tritium is around a piddling 12 years). So you need a durable, probably non-crystalline phosphor efficient for the type of radiation the source gives off. It can be done. There is actually a lot of reference material out there for self-luminous signs. However, those are only rated in years and not millennia. Something lasting thousands of years would likely require quite a bit of materials research, if only to make sure nothing dangerous is likely to escape.
As for working while red hot, for really hot operating conditions you probably want ceramics. Adolph Coors, besides making beer, have long had a business of making laboratory-grade ceramics. Back in the late-Fifties to early-Sixties they were involved in a project to produce a half-gigawatt, air-cooled fission reactor. They developed pneumatically-operated, ceramic actuators designed to operated while white hot. The government reactor project was cancelled before completion, but today the descendants of those actuators are still used in some steel mills.
Which gives me the mental image of fluidic circuits in ceramic media operating somewhere very hot.