Methane Gas Hydrate (MGH) is formed by ‘cages’ of 12 or more water molecules which encapsulate a methane molecule. It only forms in the presence of abundant methane. Since the planet is 318 times the mass of the Earth, there is plenty of methane present. It is freed from the MGH by the continuing fusion reaction, or in the cases of the other giant planets by occasional small impacts which are always interpreted as ‘storms’ by astronomers who believe the giant planet are balls of gas. Methane is detected in the atmospheres of all four giant planets by its infrared absorption spectra. But the methane molecule is destroyed by sunlight once it rises to the top of an atmosphere, so its continual observation indicates that it is continually being released.
The explosions are due to the fact that in the low temperature in which the giant planets were formed the fractionation (relative concentration) of deuterium (heavy hydrogen) is greatly enhanced, so the water molecules are mostly heavy water. This deuterium is a nuclear fuel. Just as the miniturization of nuclear bombs requires the material to be compressed. The compression by a huge impact both increases the local temperature and compresses the MGH triggering the huge planet-producing explosion. As the burning in the crater continues, it melts more ice making more deuterium available. The whole planet is not going to melt because it is too massive and cold.
There are many small impacts on the giant planets which produce fusion explosions, for example the larger of the Shoemaker-Levy 9 fragments. These explosions are only transient because of the low temperature of these planets. A huge impact compresses and raises the temperature of a large amount of MGH causing a large explosion, blasting out a huge cloud of material which eventually forms a terrestrial planet. This happened 6,000 years ago when proto-Venus was created. I say proto-Venus because it is still essentially a molten sphere of heavy elements (iron, nickel, sulfur, with a thin basalt crust) on which the volatile elements blasted into space at the same time have not yet settled because it is too hot. Such a large impact triggers a huge furnace on Jupiter which slowly diminishes but the temperature of the reaction has decreased to the lowest possible value which produces gamma radiation and helium nuclei which have been detected by the Galileo atmospheric probe. Incidentally, the creation of Venus shows how al the other terrestrial planets, Mars and the Earth were formed, each by a separate impact Mars 4.6 and Earth 3.9 billion years ago. Mercury was the solid iron core of Mars until 687 BC, when it was ejected in the vicinity of the Earth.