There is no* energy stored holding it together, just as there is no energy released when splitting a brick from the ground or splitting two magnets.
*The energy stored in the electrical repulsion of the protons is much much less than the energy required to break the strong force bonds amongst the protons and neutrons, so energy is consumed rather than released in a split.
There should still be lots of energy stored holding it together. It’s just incredibly hard to split.
But it takes more energy to split than you get out of it.
There is no* energy stored holding it together, just as there is no energy released when splitting a brick from the ground or splitting two magnets.
*The energy stored in the electrical repulsion of the protons is much much less than the energy required to break the strong force bonds amongst the protons and neutrons, so energy is consumed rather than released in a split.