Confirmation of deficient welding work in two penetration pipes of the ‘Hanbit Nuclear Power Plant’

Some of the penetration conduits at Unit 5 of the Hanbit Nuclear Power Plant in Yeonggwang-gun, Jeollanam-do, where a suspicion of construction work was raised, were found to use inappropriate materials.

Hanbit Nuclear Power Plant in Yeonggwang-gun, Jeollanam-do. News 1

On the 19th, the Hanbit Nuclear Power Plant Nuclear Safety Committee Regional Office held the ‘Hanbit Nuclear Safety Council’ at the Radiation Control Center in Yeonggwang-gun, Jeollanam-do, and announced the results of an investigation into suspected improper work on the head of the Hanbit 5 reactor.

In the process of repairing and welding 84 head penetration pipes of the reactor head penetration pipes of the Hanbit No. 5 nuclear power plant of Korea Hydro & Nuclear Power from April to last month, two penetration pipes 39 and 67 were ‘Inconel 690 material was not found to be used’ and non-compliant stainless steel material was used.

The planned preventive maintenance was a maintenance job that consisted of reinforcing the Inconel 600 material used in the existing pipe with Inconel 690 material, which compensated for the deficiencies by being vulnerable to corrosion and cracking at high temperatures and pressures.

The reactor head penetration tube is an insertion passage for a control rod that controls nuclear fission. If an abnormality occurs here, there may be a problem with the insertion of the control rod, resulting in an uncontrollable nuclear fission situation. During preparation for operation on the 26th of last month, Hanbit 5 had a problem with the newly replaced steam generator and the reactor was automatically shut down.

Since the 30th of last month, the Wonan Committee has been conducting field investigations checking a closed circuit television (CCTV) that contains images of the workplace. However, there is a possibility that the number of poorly constructed pass-through ducts will increase due to poor recording conditions or lack of video.

In August, when it was revealed that the No. 69 bypass pipe was welded with the wrong material, KHNP said: “There is no problem with the rest of the bypass pipes as a result of a full investigation,” and began preparations for the operation. However, it is analyzed that the defects in the self-check were revealed since in this investigation the unsuccessful construction was confirmed.

A National Security Council official said: “I thought I voluntarily reported that the bypassed part was working normally when solder error # 69 occurred. I think there was something I missed,” he said.

Young-gwang = Reporter Jin Chang-il [email protected]