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Event Report Forms (ERFs) are filed to the IAEA. Sometimes there are multiple event reports, updating the rating, the event description. Here you only see the latest event report

ERF send date: Mon, 21-10-1996
ERF description: On 8 November 1995 at 00:10 on Unit 2 the functioning test of one of the control rods (No. 6/7) was being conducted because some deficiency in the control of the concerned control rod was suspected. During the test when the control rod was dropped from the upper end position it became stuck in a position 200-225 cm and further movement of the rod was not possible. According to the Technical Specifications the unit was shut down, the control rods were moved to the lower end position, the boration and cooling of the reactor was commenced in order to start the elimination of the problem. It was identified that the sticking of the control rod was caused by a metallic foreign material jammed between the control rod and the labyrinth sealing of the guide tube.
During the annual overhaul of the Unit in 1996, a relatively large amount of foreign material was found in the primary circuit and their material was with a high probability the same as that of the piece which caused the sticking of the control rod in 1995. This temporary maintenance cover of steam generator must have been left in the circuit during the 1995 maintenance operations.
These facts serve as a reason for reevaluating the rating of the event.
Basis for rating according to C-I of Table 1 following the "spirit" of the INES guidelines the basic rating is level 1.
Additional factors: - Potential common cause failure (INES guidelines III-5.1)
- Deficiencies in safety culture and in the quality assurance process (INES guidelines III-5.3)
Taking into account the above factor the new rating is "2".

ERF rating date: 17-10-1996
ERF contact person: Mr. G. Macsuga
ERF address: Hungary
ERF affiliation: Hungarian Atomic Energy Commission, Nuclear Safety Inspectorate, P.O. Box 565

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