INES-event
INES 1

LEAKAGE OF REACTOR CIRCUIT PIPE 76 MM DIAMETER FROM REACTOR CHANNEL 32-24 TO THE DRUM SEPARATOR

On October 6, 1992 the plant radiation monitoring system detectors indicated the increase of the radioactivity 2xE-12 Cu/l to 1,6E-11 Cu/l in the room where the drum separators of the reactor circuit right side are located. Due to this the radioactivity level was constantly monitored. On October 13, 1992, the radioactivity level in the room was stabilized at 5,6E-10 Cu/l. Radioactivity increase 1xE-12 Cu/l to 1,3E-10 Cu/l was also monitored out of the room (above the reactor) which is common for the ventilation system and the drum separators. No radioactivity increase was detected in the high stack. On October 14, 1992 the investigations and calculations made in the plant gave reason to believe that the leakage of the circuit water in the drum separators room caused the radioactivity level increase. The calculated leakage value is about 300 l/h. This information was presented to the Lithuanian Regulatory Body. Following the requirements of the Safety Rules (available for INPP) as well as those of the "Technical Specifications" the reactor must be shut down in the case of a leakage detection in the drum separators room. But at the same time no directions for a leakage identification are provided in the abovementioned documentation. The reactor has been shut down at 12.00 on October 15, 1992 by agreement reached between VATESI and Ignalina NPP. After the reactor was cooled during the inspection programme performance a crack on the elbow of the pipe from reactor channel 32-24 was detected. Having examined the crack we came to the conclusion that the pipe was damaged mechanically during the installation. But having effected by operational factors pipe metal was destroyed and it caused the leakage. The reactor was put into operation after the damaged part of the pipe was replaced by a new one.
Basic level rating: 0 (Table III.2-A1)
Due to the absence of the direction for a leakage identification in the relevant documentation the final rating level is: 1.

Location: IGNALINA-2
Event date: Thu, 15-10-1992
Nuclear event report
Legenda & explanation