As part of the regular maintenance that began at the Krško Nuclear Power Plant at the beginning of this month, a detailed inspection of the nuclear fuel rods is being conducted after damage was detected on the rods of three fuel elements.
According to a statement from NEK, the damage to the rods, with 235 rods linked in one fuel element, was indicated by data from regular measurements during reactor operation. However, considering the overall deviations in the activity of radioactive particles in the primary circuit coolant, and given that the recorded deviations were below three percent of tolerance, and considering the imminent shutdown of the reactor and the start of the regular planned maintenance, it was decided that detailed examinations of the fuel elements and the rods within them would be carried out during the maintenance. The fuel rods are tubes made of zirconium alloy with a diameter slightly above one centimeter, filled with pellets of uranium-enriched nuclear fuel.
According to Ide Novak-Jerele, damage to the fuel element rods has occurred during previous operations of NEK as well, but since greater integrity weaknesses of the damaged rods have been detected this time, a detailed ultrasonic examination of all fuel rods from the 121 fuel elements present in the NEK reactor is underway. According to the initial plan, 56 out of a total of 121 fuel elements were to be replaced during this maintenance, and only after the completion of the detailed inspection will it be known how many fuel elements will actually need to be replaced. Detailed examinations will also be conducted on all other essential parts of the nuclear reactor, in order to work with the nuclear fuel supplier, Westinghouse, to determine the cause of the damage to the fuel rods.
Since the reactor at NEK is of the PWR type, that is, a pressurized water reactor, regardless of such damage within the core, there is no danger of the spread of radioactivity outside the containment, as all radiation remains within the primary circuit of the reactor’s coolant. Due to this intensified inspection work, it is possible that the maintenance may extend slightly beyond the planned period of 35 days. In any case, NEK emphasizes that there is no reason for any concern, as the situation is completely under control and in a routine management mode for maintenance and all anticipated and possible situations.
