The corium undergoes degradation. The Elephants Foot, hard and strong shortly after its formation, is now cracked enough that a cotton ball treated with glue can easily remove its top 1- to 2-centimeter layer. The structures shape itself is changed as the material slides down and settles. The corium temperature is now just slightly different from ambient. The material is therefore subject to both day–night temperature cycling and weathering by water. The heterogeneous nature of corium and different thermal expansion coefficients of the components causes material deterioration with thermal cycling. Large amounts of residual stresses were introduced during solidification due to the uncontrolled cooling rate. The water, seeping into pores and microcracks, has frozen there. This is the same process that creates potholes on roads, accelerates cracking.
Corium (and also highly irradiated uranium fuel) has the property of spontaneous dust generation, or spontaneous self-sputtering of the surface. The alpha decay of isotopes inside the glassy structure causes Coulomb explosions, degrading the material and releasing submicron particles from its surface. The level of radioactivity is such that during 100 years, the lavas self irradiation ( α decays per gram and 2 to  of β or γ) will fall short of the level required to greatly change the properties of glass (10 α decays per gram and 10 to 10 Gy of β or γ). Also the lavas rate of dissolution in water is very low (10 g·cm·day), suggesting that the lava is unlikely to dissolve in water.
It is unclear how long the ceramic form will retard the release of radioactivity. From 1997 to 2002, a series of papers were published that suggested that the self irradiation of the lava would convert all 1,200 tons into a submicrometre and mobile powder within a few weeks. But it has been reported that it is likely that the degradation of the lava is to be a slow and gradual process rather than a sudden rapid process. The same paper states that the loss of uranium from the wrecked reactor is only  per year. This low rate of uranium leaching suggests that the lava is resisting its environment. The paper also states that when the shelter is improved, the leaching rate of the lava will decrease.
Some of the surfaces of the lava flows have started to show new uranium minerals such as UO·2HO (eliantinite), (UO)O·4HO (studtite), uranyl carbonate (rutherfordine), čejkaite (), and the unnamed compound NaU(CO)·2HO. These are soluble in water, allowing mobilization and transport of uranium. They look like whitish yellow patches on the surface of the solidified corium. These secondary minerals show several hundred times lower concentration of plutonium and several times higher concentration of uranium than the lava itself.