major concerns about the safety of the reactor arose from the formation of cracks in the so-called core shroud inside the reactor vessel since the 1990s. this is due to steel corrosion by the coolant. notwithstanding the countermeasures (reinforcements of the shell, chemical additives in the coolant), the cracks were increasing in length year after year. the longest crack is one third of the limit allowed by the safety specifications and it was expected that by 2012 it woulde be still less than half this value. the situation is continuously monitored and other chemical measures for its stabilization are being tested.