NSSC Allows Hanul Unit 3 Criticality... "Final Safety Confirmation Planned Through Follow-up Inspections"

[Asia Economy Reporter Joo Sang-don] The Nuclear Safety and Security Commission announced on the 17th that it has approved the criticality of Hanul Unit 3, which underwent a regular inspection starting April 20 this year.

Criticality refers to the state in a reactor where a nuclear fission chain reaction continuously occurs, and the number of neutrons produced equals the number of neutrons lost, resulting in a neutron population equilibrium. Upon approval of criticality, the remaining 10 inspection items, including the zero-power physics test (reactor characteristic test), are conducted during the reactor criticality process or the power ascension process after criticality.

The NSSC conducted inspections on 83 items that must be completed before criticality during this regular inspection and confirmed that the reactor criticality can be safely achieved in the future. During the inspection period, 54 locations of the Containment Liner Plate (CLP) suspected of incomplete concrete filling in the containment building concrete were cut and examined, revealing 6 locations with incomplete concrete filling, which were repaired. The structural soundness evaluation showed no abnormalities in the containment building structure.

Additionally, 221 locations showing signs of paint discoloration and peeling were found on the upper dome of the containment building. Evaluation confirmed surface corrosion on 35 locations of the upper dome steel plates. Measures such as welding were taken on areas with thickness reduction according to relevant procedures, and all foreign substances (59) found inside the steam generator through additional foreign material inspection equipment were removed.

Based on the results of the regular inspection so far, the NSSC has approved the criticality of Hanul Unit 3 and plans to finalize safety confirmation through follow-up inspections (10 items), including power ascension tests.

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