OK, let’s say I’m a mad nuclear physicist with a huge budget and a flair for the dramatic. I take a shine to the ethereal blue glow produced when a charged particle passes through an insulator faster than the speed of light in that medium (for example, a really fast electron going through water faster than the speed of light in water). I get that I’ll need stupid amounts of radioactive materials and distilled water and shielding (leaded glass, I guess), but is that all? How long will the glow last if I’m using relatively normal LEU fuel as the source? How much light can I expect per pound of that fuel?
Note that I’m mad: Getting anything but a cool blue glow out of this is not a priority, but not getting cancer would be nice as well. Something hovering near criticality is a nice bargaining chip if the Big Damn Heroes infiltrate my mountain lair and I need to discourage them from shooting things, but even that is not required.
A quick look through the Wikipedia article on Cerenkov Radiation ( Cherenkov radiation - Wikipedia ) shows that you don’t get generation of X-rays except at certain special wavelengths. You do preferentially generate shorter wavelength rays, but you have to consider that the water’s going to absorb all of the dangerous UV in a pretty short distance (assuming you generate your Cerenkov radiation in water, rather than some more exotic substance). In principle it ought to work pretty safely, although I might be concerned about those odd X-ray wavelengths. The biggest problem, of course, is that it’s a grotesquely wasteful way to generate light, and you’d be better off using the output of your reactor to power a halogen bulb or two. But it does look cool.
Cobalt-60, which is used for sterilization of medical equipment, will produce Čerenkov radiation in water. They usually keep it in a pool of water when not zapping bugs, and I was told that the water keeps you perfectly safe.
I’ve used a Cobalt 60 irradiator. They didn’t keep it in a pool of water, but in a heavy, lead-constructed container. Co60 throws off a LOT of gamma radiation, and is pretty scary stuff. The idea of it being under just water freaks me a bit, because I couldn’t help thinking what would happen if the water suddenly disappeared.
Does water really stop all the gamma radiation? From what you say, it must, but I’d still stay away, myself.
It can’t stop all gammas, of course, since the attenuation follows an exponential. But I doubt you’d really get adequate shielding – Cobalt-60 has two gamma-emission lines at around 1.17 and 1.33 MeV, water has a mass attenuation coefficient (mu/rho) of about 6.31*10[sup]-2[/sup] cm[sup]2[/sup]/g at 1.25 MeV, so, using I = I[sub]0[/sub]exp[-(mu/rho)x(rho)] (with rho being the density ~1 g/cm[sup]3[/sup]), I get for the Half Value Layer thickness (i.e. where the intensity has dropped to 50%):
x = ln(2)/[(mu/rho)rho] ~= 11 cm
With lead, by contrast, you’d only need about 1.04 cm (if my numbers aren’t off. Somebody check please).
As for the OP, if you want a little more colour variation with your nuclear power lighting, may I suggest looking into radioluminescent tritium lighting – comes in any colour, but looses half its brightness in about 12.36 years.