As part of the power start-up phase and the gradual increase in reactor power, tests are currently also being performed on the safety valves used to discharge steam from the steam generators. This is a standard operation. It is also routinely performed when the other nuclear units in Slovakia are returned to operation following scheduled outages. These outages, which are required for refuelling and maintenance, take place at least once a year.

Similar tests are also carried out at conventional power plants, as every pressure vessel is fitted with a safety device which, by law, must be inspected at regular intervals. These tests are usually accompanied by loud noise.