That depends on the power rating of the reactor.
A nuclear reactor could.
An Ark reactor as currently describe in comic is very much like a Nuclear Fuel Cell. Possibly convert energy from Nuclear reaction to power. Possibly a plasma nuclear fusion reactor. I believe in the future it could be made. See the link and compare the similarity of fusion reactor and Ark reactor.
The Russians are working on the problem of creating a nuclear reactor fuel out of americium, but they're still working the problem. In addition, they haven't built a reactor that uses americium as a nuclear fuel yet, either.
yes
overheatingpossibly meltdown
Yes, the electric power grid could be powered by electric power generated through nuclear energy.
The nuclear core goes into a process known as 'meltdown' if it becomes too hot. For a reactor to reach critical temperature something serious has to malfunction, this could be a lack of water inside the reactor, pressure loss inside the reactor or no control rods inside the reactor, all of these faults could lead to severe damage to the reactor core and a possible lead to a thermal explosion(not a mushroom cloud explosion).
No. LLNL even tested several Uranium-Hydride bombs in the 1950s. Even though their computer models said the devices should explode, none gave a nuclear yield. One could use the waste from the reactor as a Radiological Weapon, but the reactor itself is not useful as a weapon.
Nuclear energy is released as heat in the fuel of a nuclear reactor, but only when the reactor has been brought to criticality and the chain reaction started. At that point the heat must be used, it can't be stored and used later. Before criticality is established, the reactor is shutdown and producing no nuclear heat from fission, so you could regard it as having potential nuclear energy in that state
By "nuclear leaks" is meant the leakage of radioactive material from a nuclear facility such as a nuclear reactor or a store of spent fuel. This would only happen if the fuel had been damaged and the zircaloy sheathing was leaking, and also the contents of the reactor or store were leaking into the atmosphere. The leaked material could be gaseous like iodine, or could be particulate.
Modern submarines are powered by a nuclear reactor. Others are powered by diesel engines while they are on the surface and batteries while they are submerged. The older ones that were powered by diesel and batteries had their limitations. While they were on the surface running on diesel engines they left a trail of exhaust smoke which gave away their position. When they were submerged and running on batteries they could only last so long and then they had to come to the surface, run the diesel engines and recharge the batteries. The submarines that are run by nuclear power do not have to resurface for a very, very long time.
EBR-1 in Idaho, a fast breeder reactor was the first prototype nuclear power plant in 1951. However being only a prototype it could only power a small bank of lightbulbs inside the control building.APS-1 Obninsk southwest of Moscow, a graphite moderated reactor (predecessor to the RBMK at Chernobyl) went on the main power grid in 1954.BORAX III in Idaho, a boiling water moderated reactor powered the town of Arco for one night in 1955.