• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.184.1-184
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 2003.10a
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• pp.98.2-98.2
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• 2003

• Journal of Korea Society of Digital Industry and Information Management
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• v.17 no.1
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• pp.35-44
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• 2021

With the development of information technology, the cybersecurity threat continues as digital-related technologies are applied to the instrumentation and control system of nuclear power plants. The malfunction of the instrumentation and control system can cause economic damage due to shutdown, and furthermore, it can lead to national disasters such as radioactive emissions, so countering cybersecurity threats is an important issue. In general, the study of cybersecurity in instrumentation and control systems is concentrated on safety systems, and diverse protection systems perform protection and reactor shutdown functions, leading to reactor shutdown or, in the worst case, non-stop situations. To accurately analyze cyber threats in the diverse protection system, its linked facilities should be analyzed together. Risk analysis should be conducted by analyzing the potential impact of inter-facility cyberattacks on related facilities and the impact of cybersecurity on each configuration module of the diverse protection system. In this paper, we analyze the linkage of the diverse protection system and discuss the cybersecurity linkage threat by analyzing the availability of equipment, the cyber threat impact of the linked equipment, and the configuration module's cybersecurity vulnerability.

• Fire Science and Engineering
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• v.30 no.3
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• pp.79-85
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• 2016

Serious electrical problems, such as shorts, ground faults, or circuits, often cause fire events in the fire proof zone of nuclear power plants. These would be directed to the loss of safe shutdown capabilities performed by safety-related systems and equipment. The fire event can be treated with the basic design principle that safety systems should maintain their functions with redundancy and independency. In the case of a cable fire in the main control room, operators cannot perform their mission properly and can misjudge the situation because of spurious operation, incorrect indication or instrument. These would deteriorate the plant capabilities of safety shutdown and result in disastrous conditions. Therefore, during a main control room fire, 5 minutes of operator action time is very important to operate the safety shutdown components. This paper describes the cable functional failure temperature criteria and conducted a cable functional failure time evaluation using Fire Dynamic Simulator to obtain the operator action time for a main control room fire.

• Fire Science and Engineering
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• v.32 no.1
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• pp.57-65
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• 2018

In this study, a post-fire safe shutdown analysis (PFSSA) including multiple spurious operation (MSO) treatments for cables was conducted with an imaginary nuclear power plant for training using a deterministic fire analysis code. The imaginary nuclear power plant for the training consisted of a reactor containment building and an auxiliary building, including a total of 22 fire areas. The equipment including valves, pumps, emergency diesel generators, switch gears, motor control centers, and logic controllers were located in each fire area of the imaginary plant. It was assumed that each equipment is connected with two cables and that each cable passes through the fire areas along the cable trays. A database containing the information on the equipment and cables for the imaginary plant was constructed for the fire area analysis. The fire area analysis was performed for several assumed MSO scenarios, equipment logics, and cable logics. A mitigation measure using a three hour rated wrap was applied to the failed cables and cable trays after the fire area analysis.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.1
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• pp.23-29
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• 2016

The Second Shutdown Drive Mechanism (SSDM) provides an alternate and independent means of reactor shutdown. The Second Shutdown Rods (SSRs) of SSDMs are poised at the top of the core by the hydraulic force driven from a hydraulic system during normal operation. The rods drop by gravity when a trip is commended by a Reactor Protection System, Alternate Protection System, Automatic Seismic Trip System or operator by means of power off solenoid valves of hydraulic system. This paper describes the test results of seismic qualification of a prototype SSDM hydraulic system to demonstrate that its structural integrity and operability (functionality) are maintained during and after seismic excitations, that is, an adequacy of the SSDM design. From the results, this paper shows that the SSDM hydraulic system satisfies all its design requirements without any malfunctions during and after seismic excitations.

• Fire Science and Engineering
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• v.26 no.1
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• pp.10-15
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• 2012

The fire event occurred in fire proof zone often causes serious electrical problems such as shorts, ground faults, or open circuits in nuclear power plants. These would be directed to the loss of safe shutdown capabilities performed by safety related systems and equipments. The fire event can treat the basic design principle that safety systems should keep their functions with redundancy and independency. In case of a cable fire, operators can not perform their mission properly and can misjudge the situation because of spurious operation, wrong indication or instrument. These would deteriorate the plant capabilities of safety shutdown and make disastrous conditions. In this paper, investigation and cause analysis of cable fire in Nuclear Power Plant, we described the cable fire temperature and functional failure criteria and the cable functional failure temperature evaluation by exposed fire is studied.

• Nuclear Engineering and Technology
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• v.44 no.5
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• pp.459-470
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• 2012

From the PSA point of view, the Fukushima accident of Japan in 2011 reveals some issues to be re-considered and/or improved in the PSA such as the limited scope of the PSA, site risk, etc. KAERI (Korea Atomic Energy Research Institute) has performed researches on the development of an integrated risk assessment framework related to some issues arisen after the Fukushima accident. This framework can cover the internal PSA model and external PSA models (fire, flooding, and seismic PSA models) in the full power and the low power-shutdown modes. This framework also integrates level 1, 2 and 3 PSA to quantify the risk of nuclear facilities more efficiently and consistently. We expect that this framework will be helpful to resolve the issue regarding the limited scope of PSA and to reduce some inconsistencies that might exist between (1) the internal and external PSA, and (2) full power mode PSA and low power-shutdown PSA models. In addition, KAERI is starting researches related to the extreme external events, the risk assessment of spent fuel pool, and the site risk. These emerging issues will be incorporated into the integrated risk assessment framework. In this paper the integrated risk assessment framework and the research activities on the emerging issues are outlined.

• Journal of the Korean Society of Safety
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• v.26 no.5
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• pp.41-45
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• 2011

The fire event occurred in fire proof zone often causes serious electrical problems such as shorts, ground faults, or open circuits in nuclear power plants. These would be directed to the loss of safe shutdown capabilities performed by safety related systems and equipments The fire event can treat the basic design principle that safety systems should keep their functions with redundancy and independency. In case of a cable fire, operators can not perform their mission properly and can misjudge the situation because of spurious operation, wrong indication or instrument. These would deteriorate the plant capabilities of safety shutdown and make disastrous conditions. In this paper, the cables of the representative nuclear power plant in korea is selected and the cable functional failure temperature by exposed fire using Cable Response to Live Fire(CAROLFIRE) is studied. It is expected that the results are very useful to know the cable failure temperature by exposed fire. We confirmed the safety and integrity of the cable by exposed fire and those results will use the based data of cable exposed fire characteristics.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.551-556
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• 1997

A present study addresses a loss-of-RHR event as an initiating event under specific low power or shutdown conditions. Two typical plant configurations, cold leg opening case with water-filled steam generators and pressurizer opening case with emptied steam generators, were evaluated using the RELAP5/ MOD3.2 code. The calculation was compared with the experiment conducted at ROSA-IV/LSTF in Japan. As a result, the code was capable of simulating the system transient behavior following the event. Especially, thermal hydraulic transport processes including non-condensable gas behavior were reasonably predicted with an appropriate time step and CPU time. However, there were some code deficiencies such as too large system mass errors and severe flow oscillations in core region.