Europium has a strong tendency to absorb neutrons, making it useful in nuclear power production. A nuclear power plant produces electricity from the energy released by nuclear fission. Slow-moving neutrons collide with uranium or Plutonium atoms, breaking them apart and releasing energy as heat. The amount of energy produced in a nuclear power plant is controlled by the number of neutrons present. Europium is used to absorb neutrons in this kind of control system. Chemical properties Europium is the most active of the lanthanides. It reacts quickly with water to give off hydrogen. It also reacts strongly with oxygen in the air, catching fire spontaneously. Scientists must use great care in handling the metal.