Key info omitted from nuclear reactor assessment

Posted on : 2012-10-16 14:02 KST Modified on : 2019-10-19 20:29 KST
Kori nuclear plant is already living on borrowed time and prone to malfunction

By Kim Kwang-soo, Busan correspondent

It belatedly came to light that the core damage frequency (CDF) of reactor No.1 at the Kori Nuclear Power Plant in Busan exceeded International Atomic Energy Agency (IAEA) standards. The core of a reactor generates radioactive substances in large quantities. The initial 30-year lifespan of the aged nuclear reactor expired and was extended by 10 years in January 2008. The Korea Hydro & Nuclear Power (KHNP), which operates the reactor, intentionally omitted these facts in its report on the proposed extension of the core.

Parliamentary inspection materials that lawmaker Jo Gyeong-tae (Democratic United Party) received from the KHNP and the Korea Institute of Nuclear Safety (KINS) on Oct. 15 showed that the KHNP measured the core damage frequency (probabilistic risk assessment) in accordance with guidelines presented by the Ministry of Science and Technology (now known as the Ministry of Education, Science and Technology) between November 1999 and November 2002, and the result was 1.19/10,000, higher than the standard set by the IAEA, which is 1/10,000. This means accidents that damage the nuclear reactor have a likelihood 1.19 out of 10,000 chance of occurring for every one year the reactor is in operation.

Nevertheless, the KHNP did not include this result in its "Assessment on Continuing Operations at the Kori No.1 Reactor", which the organization submitted to the Ministry of Science and Technology to determine whether the lifespan of the reactor should be extended or not in June 2006. A KHNP official said, "The inspection findings aren’t reliable and there was no rule that the probabilistic risk assessment had to be included." To this, Rep. Jo pointed out, "It is a serious problem that there is no regulation that allows us to immediately halt the operations of nuclear plants even when the CDF, which is directly related to a major release of radioactive materials, exceeds the standards of the international agency."

More recently, between July 2005 and May 2007, the KHNP carried out a second assessment and found out that the CDF dropped below the IAEA standard to 0.162/10,000th. In its "Report on the Safety of Continuing Operation of Kori No.1 Reactor," released in December 2007, the KINS stated, "The level of damage declined by 86 percent from the first assessment (November 1999-November 2002)." The KHNP reported to the Ministry of Science and Technology that the CDF had improved to a level far below the IAEA standard since the first measurement by the replacement or supplement of reactor equipment including coolant and the KINS acknowledged this.

Yang Lee Won-young, director of denuclearization of energy division at the Korean Federation for Environmental Movement asked back, "If the KHNP called the results of 1999-2002 unreliable, on what grounds does it believe the results from 2005-2007?" Yang added that the organization should disclose the method employed in the assessment and the extent of damage found in the core.

Seoul National University Professor of nuclear engineering Suh Kune-yull said, "The CDF can be altered not only by the replacement of equipment but also by arranging the coefficient," adding, "We cannot confirm that the replacement of equipment resolved the fundamental problems of core damage."

A KHNP official explained, "When we submitted the report to the KINS in 2007, the Nuclear Safety and Security Commission, the Ministry of Science and Technology-affiliated organization, advised us to include probability risk assessment in the report. We didn’t intentionally leave out the data for 1999-2002."

South Korea’s first nuclear power plant, the Kori No.1 reactor, has had 129 reported incidents or breakdowns, which accounts for 19.5 percent of the 659 accidents or breakdowns that have occurred at nuclear power plants across the nation. Voices demanding the reactor be shut down have been continuously raised since the reactor began malfunctioning, including a incident that occurred in February in which electricity provision was cut for 12 minutes and the temperature of cooling water rose after even the emergency generator had ceased to function.

 

Please direct questions or comments to [english@hani.co.kr]

 

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