This study evaluated the habitability of operators for main control room fires in nuclear power plants. Fire modeling (FDS v.6.0) was utilized for a fire safety assessment so that it could determine the performance of the smoke ventilation and operator habitability with the main control room. For this study, it categorized fire scenarios into three cases depending on the conditions in the HVAC system. As a result of fire modelling, it showed that Case 1 (with HVAC) would give rise to the worst situation associated with the absolute temperature, radiative heat flux, optical density, and smoke layer height as deliberating the habitability and smoke ventilation. On the other hand, it showed that Cases 2 (w/o HVAC) and 3 can maintain much safer situations than Case 1. In the case of temperature at 820 s, Cases 2 and 3 were up to approximately 63% greater than Case 1 in the wake of ignition. In addition, the influence of radiative heat flux of Case 1 was even larger than Cases 2 and 3. That is, the radiative heat fluxes of Cases 2 and 3 were approximately 68% higher than Case 1. Furthermore, when it comes to considering the optical density, Case 1 was approximately 93% greater than Cases 2 and 3. Accordingly, it expected that the HVAC system can influence a the performance on the smoke ventilation that can be sustainable for operator habitability. On the other hand, it revealed an inconsecutive pattern for the smoke layer height of Cases 2 and 3 because supply vents and exhaust vents were installed within the same surface.

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.

No abstract

When the fire takes place in Nuclear Powr Plants(NPPs), the reactor should achieve and maintain safe shut-down conditions and minimize the radioactive material released to the environment. The U.S. Nuclear Regulatory Commission (NRC) has issued numerous generic communications related to fire protection over the past 20 years, after it issued its requirements in the Fire Protection Rule set forth in Title 10, Section 50.48 of the Code of Federal Regulations (10 CFR 50.48) and Appendix R to the 10 CFR 50. The and Nuclear Energy Institute (NEI) has developed a Methodology for Risk Informed Fire Safe-Shutdown Analysis, which is related to the Deterministic Method for Multiple Spurious Operations solutions. The aim of this study was to identify, achieve, and maintain Post-Fire Safe-Shutdown of the Main Control Room (MCR) of the CANDU reactor, even though one train of the multiple Safety Structures, Systems, and Components (SCCs) fail by the technical specification and analysis method.