Thank you for your detailed reply Mar R. ^_^
But it is most interesting that an photon can be the cause of ejecting an electron. Because what have nuclei as natural tendency when it comes to having electrons ? I wonder what happens in a strong electric field with the radioactive nuclei who start to loose electrons. Does the natural instability not increase ? I would think so for some reason.
I wouldn't necessarily think it surprising that a photon can eject an electron. When one considers the wave-partical duality principle of classical physics, perhaps it seems 'obvious'.
If one considers a photon as a particle (after all, a photon unquestionably has momentum), why shouldn't it be able to knock an electron out of position in its orbital? Don't forget that the photoelectric effect is for a 'direct' impact, where all the energy of the photon is transferred into the electron (in much teh same way as a 'direct' impact of 2 billiard balls transfers all the kinetic energy of the first into the 2nd, leaving the 1st ball stationary).
Glancing impacts are different, and the equivalent process is Compton scattering. If a high energy photon strikes an electron, then some of the energy of the photon gets transferred to the electron, and the photon emerges with reduced energy at a different angle (think of it as a billiard ball hitting another at a glancing angle - the energy of the first ball is shared amongst both, and the first ball is deflected). As the photoelectric effect becomes less frequent as photon energy goes up (PE effect is most important in the <100 keV range) - in part, because electron binding energies are mostly in teh < 100 keV range - this means Compton scattering becomes more important as photon energy increases.
Nuclei only have a natural tendency to 'collect' electrons because they are small, heavy and positively charged, and electrons are light and negatively charged. Take a postiviely charged subatomic particle, that is more massive than an electron, and it too will hold electron(s) in orbit. An example is an anti-muon, which is a positively charged particle with a mass of about 10% of a proton. It can bind an electron in an orbit, and is virtually indistinguishable for hydrogen, apart from being only 10% of the atomic mass (and the fact that an anti-muon only has a half life of a few microseconds). Even a positron and electron can orbit each other in a 'sort of atom' - but even from the naive perspective of Newtonian mechanics, one can see that this system isn't really comparable because it doesn't have a massive nucleus. The other issue is the prompt positron-electron annihilation reaction.
As it is the electrostatic force holding the electrons in their orbitals, any electrical field can remove the electrons. This is what happens in a spark or electrical arc. The electrical field pulls electrons out of outer orbitals, and attracts them to the anode. The positively charged ion (consisting of nucleus and any remaining electrons) is attracted to the cathode. With the presence of the applied electric field - you actually get a 'chain reaction' type effect. Electrons and ions get attracted by the electodes, and accelerate - colliding with other atoms, and knocking more electrons off. This is why electric arcs have the unusual property of reducing their electrical resistance as you increase the current - more current, gives more collisions, which gives more particles able to participate in current flow. To start the arc you just need an electric field strong enough to pull some electrons off the atoms in the gas.
For weakly bound electrons in the outer orbitals (e.g. metals - which are metallic by virtue of the very loosely bound outer electrons) can if heated 'evaporate' electrons off the surface, purely by virtue of the vibrational kinetic energy. They fall back promptly, attracted by the electric field, as they leave the metal with a positive charge. Of course, if you manipulate the electric field by adding a very highly positively charged anode, you can capture these evaporated electrons and direct them somewhere else - and this is how cathode ray tubes, thermionic valves, X-ray tubes, etc. work.
When you get radioactive decay, the net result, regardless of the decay type, is stirring up and the removal of electrons from atoms. We've already discsussed photon emission. But beta particles (electrons) can collide with other electrons and knock them out of their orbitals (so effectively beta and gamma radiation are virtually identical in their effects on atoms). They repeatedly hit electrons, gradually dissipating their energy - and of course, the electrons they knock out of their orbits, collide, or create other photons, as a result, a single particle, can disrupt hundreds or thousands of electrons. Alpha particles do exactly the same thing - they are big and heavy, and can knock electrons out of their orbits. As they are slow, and heavy and highly charged, they tend to be very effective at this, so release their energy via thousands of electron collisions during a journey of only a few micrometers.
During the early development of thermionic tubes/CRTs/X-ray tubes, it was quite common to add some radioactive materials to the heated cathode filament. The problem was that heating alone, wouldn't always get enough electrons off the surface to permit a decent current. By mixing in a radioactive material, the radioactive decay would stir up the electrons, giving them a boost of kinetic energy, and help them 'evaporate'. Alpha emitters (like thorium) were used because they only needed a very short range of action.
Going back to the electric arc issue, Interestingly, many arc lamps actually contain trace amounts of radioactive materials - e.g. I have some halide arc lamps, that contain traces of 85-Kr (beta emitter). The radioactive decay keeps a small number of electrons smashed off their atoms. This makes the lamp easier to start, because there are already a few electrons and ions free to be attracted by the electric field - the field doesn't necessarily have to be strong enough to rip the electrons off.
As to the nuclear stability - that's really very different to the orbiting of electrons. By and large, the nucleus is its own system, bound together by its own forces (of extremely high binding energy and strength), whereas electrons are loosely bound to the nucleus by the relatively weak electromagnetic force. The traditional teaching of classical physics is that the presence of electrons doesn't affect nuclear stability: an isolated nucleus has the same half life as a nucleus in a neutral atom, or a slightly charged ion. This is essentially true. Although, quantum mechanical models in fact predict that there can be an extremely marginal effect on nuclear stability from electron binding, where the nuclear energy level is of a similar level to electron energy levels. As you would expect, this has only been observed in a very few isotopes which are low-energy pure gamma emitters (e.g. 99m-Tc), where changing the electron configuration (e.g. by chemical reaction) can have minute effects on nuclear half life (e.g. decreasing by 0.01%). However, for all practical purposes, it can be assumed that nuclear half life is totally independent of chemcial or electron state.
I mean, if we need hydrogen, why not start thinking about how to create it from waste we have to dispose of anyway.
Regrettably, I can see no plausible way of doing that. Hydrogen is hyperabundant on earth in the form of water - and the hydrogen is easily and efficiently separated by breaking the chemical bonds. Far better to do this, than try to make hydrogen from heavier nuclei, where the energy gradient you have to work against is 10s of thousands of times higher.
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