Ten days after the Fukushima accident of 11 March 2011, the South Korean government decided to conduct comprehensive special safety inspections (SSI) on all the nuclear facilities in Korea. The country’s nuclear operator Korea Hydro and Nuclear Power (KHNP) had already conducted a voluntary inspection of its nuclear facilities between 16 and 18 March 2011.
Korea has 21 operating reactors and seven reactors under construction. The operating reactors (four CANDU units and 17 pressurized water reactors) have a combined output of 18.7 GW and provide around 30% of Korea’s electricity.
The special inspections were just the first phase of South Korea’s response to Fukushima.
Phase two, currently underway, which includes the development of an action plan to deal with the issues identified during the inspections as well as a review of the lessons from the Fukushima accident. Phase three will involve amendment of regulatory requirements, standards and guides as well as the continued application of lessons learned from the Japanese accident over the longer term. Also in October 2011, Korea established a new independent nuclear regulator the Nuclear Safety and Security Commission (NSSC). NSSC replaces the divisions responsible for nuclear and radiation regulation, which were part of the Ministry of Education, Science and Technology–the same body responsible for promoting nuclear power.
Korea’s special safety inspections (SSI) were performed from 21 March to 30 April 2011; over 70 experts from industry, academia, research institutions, and the Korean Institute of Nuclear Safety (KINS) were involved.
Inspections covered six areas: design against earthquake/tsunami, integrity of power/cooling and fire protection systems, countermeasures for severe accident, emergency response, long-term service (for nine plants operating for more than 20 years), and research reactor/nuclear fuel cycle facilities.
In mid-November, Key Yong Sung from KINS presented the recommendations from the Korean inspections at an OECD/NEA expert meeting in Tokyo, Japan.
The SSI identified 50 actions (46 for nuclear plants; 4 for other facilities) for enhancing nuclear safety by 2015. For operating plants there are 23 priority recommendations that need to be implemented during 2012. The licencee’s comprehensive implementation plan for SSI actions was submitted to the regulator in July 2011. The first progress report was due in January 2012; further reports are due every six months.
To protect against earthquakes, automatic seismic trip systems that activate above 0.18g will be installed at all Korean plants by 2012. Other near-term recommendations include strengthening a bridge at the Wolsong site and raising the height of a seawall at the Kori site. In the longer term, the safety shutdown systems at all units will be upgraded to withstand a design earthquake level of 0.3g and the potential for earthquakes at each site will be reassessed.
Other recommendations include: waterproofing electrical components such as pumps, securing additional emergency generators and securing back-up contingency for spent fuel pool cooling; the latter was identified as a priory action.
The Korean inspectors made three recommendations relating to fire safety–an area that was not highlighted in many other national reviews. Two short-term actions call for simplifying fire protection plans, strengthening cooperation between internal and external fire stations, and the introduction of a performance-based fire protection design. Another recommendation requires alternative water sources to be secured for firefighting purposes in case of tsunami, with a minimum number of workers retained at each site to operate fire trucks.
Six recommendations were identified in the area of severe accident management. Three near-term recommendations require the revision of severe accident management guidelines (SAMGs), development of new SAMGs for low-power shutdown situations, as well as increasing the duration of operator training for severe accidents to ten hours per year. Installation of passive hydrogen removal equipment in plants where it is not already installed, filtered vents to prevent containment overpressure as well as new points for injecting emergency cooling water should also be carried out in the medium term.
To improve emergency response, near-term recommendations call for additional radiation protection equipment (gas masks, potassium iodide tablets) to be secured for the population within 16 km of each nuclear plant, with extra equipment gathered in case of a prolonged emergency. Emergency plans should also be amended to include simultaneous emergencies at multiple units—a recommendation that is common to other countries including the US and Canada—and unannounced emergency exercises should be conducted at all units.
Nine plants with over 20 years of operation, including Kori 1-4, Yonggwang 1&2, Ulchin 1&2 and Wolsong 1, were inspected to confirm the adequacy of their ageing management programmes, to monitor the ageing of critical components, and to determine the adequacy of in-service management of active components like pumps and valves.
One recommendation resulting from this part of the SSI was a call for the ‘drastic reinforcement’ of safety inspections by verifying aging management plans during periodic inspections. Another recommended that the frequency of inspections should be increased at older units; for example, the reactor vessel beltline welds will now be inspected every five years at Kori, rather than every ten years. The reliability of shutdown-actuating equipment should be improved through the introduction of a preventive maintenance programme that reflects the causes of past faults.
New reactors
New build in Korea has already been affected by the events at Fukushima. Commercial operation of Shin Kori 2 and Shin Wolsong 1 OPR-1000 reactors that were due to enter service in late 2011 and early 2012, respectively, have both been delayed. And the start of construction at Shin Ulchin 1 and 2 has been put back from March 2011 and 2012.
Of the 46 recommendations from the SSI, outlined above, 33 are applicable to new plants as well as operating ones. For new plants at the final stage of operating licensing (for example Shin Kori 2 and Shin Wolsong 1) the following improvements must be made prior to commercial operation: installation of a cooling water flow path to spent fuel pool, preparation of a provisional portable diesel generator to supply power to essential equipment with the installation of a full-scale generator by 2014, installation of primary and secondary injection paths for emergency cooling water supply, installation of a hydrogen removal system, reinforcement of education and training for severe accidents, and amendment of emergency plans to consider a multi-unit emergency. For the units at the beginning of operation license or construction all 33 recommendations must be implemented before an operating license is issued.
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This article was first published in the February 2012 issue of Nuclear Engineering International
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