The Nuclear Safety and Security Commission said it allowed criticality for Shin-Wolsong Unit 1 on the 17th, which has been undergoing a periodic inspection since Jan. 5.
Criticality refers to the state in which nuclear fission of nuclear fuel continues so that a nuclear power plant can reach normal output. Allowing criticality means permitting normal operation of the plant.
The Nuclear Safety and Security Commission said, "During this periodic inspection, two types of construction errors were identified in post-installed anchor bolts that fix major equipment to concrete, and they were reconstructed."
First, it confirmed that anchor bolts (106 anchors installed on 26 devices) that fix instrumentation equipment such as a flow transmitter were installed with products that were not verified under the technical standards required by law, and all were replaced with anchors that meet the technical standards.
In addition, during maintenance of two traveling water screens that remove foreign substances from seawater flowing into the plant, it was confirmed that 12 anchor bolts fixing them were installed without meeting the effective embedment depth, and all were reconstructed.
The Nuclear Safety and Security Commission will conduct inspections of all nuclear plants to determine whether there are cases of the same type of construction errors and will continue to improve the inspection system related to anchor bolts.
The Nuclear Safety and Security Commission added, "As a result of inspecting 87 items that must be completed before criticality out of a total of 97 periodic inspection items, we confirmed that reactor criticality can proceed safely going forward," adding, "Based on the periodic inspection results to date, we are allowing criticality for Shin-Wolsong Unit 1, and we will make a final confirmation of safety through follow-up tests (10 items), including a power ascension test."