Plant Transients under Small Abnormalities of FBR “Monju” Calculated by a Plant System Code
Hiroyasu MOCHIZUKI1
1Research Institute of Nuclear Engineering, University of Fukui, 1-2-4 Kanawa-cho, Tsuruga, Fukui 914-0055, JAPAN
Abstract
The objectives of the present study are to analyze plant transients caused by small abnormalities and to find plant parameters by which operators can recognize these small abnormalities. In order to evaluate the plant transient during an abnormal situation in the water system using the plant system code NETFLOW++, the turbine and feedwater (FW) systems should be analyzed with good precision. The code is validated using the measured data at “Monju”. Several abnormalities in the water system are candidates of the present study, e.g., FW control valve degradation, FW pump degradation, heat transfer degradation due to fouling on heat transfer tubes of the evaporator, loss-of-feedwater-heating, etc. All major components in the tertiary system are included in the calculation model such as the steam generators, the high-pressure turbine, the deaerator, the FW pump, the FW heaters, the FW control valves, the steam control valve, extraction lines and drainpipes. In case of a malfunction of a FW control valve resulting in low flow rate, a large temperature increase at the outlet of the evaporator is observed. On the other hand, a temperature decrease at the outlet of the evaporator occurs if heat transfer tubes in the evaporator have fouling. As a result of the calculations, it was determined that temperature at the outlet of the evaporator is a good indicator to detect abnormal situations.
Keywords
Monju, FBR, Plant system analysis, Water system, Slight abnormality, Abnormality indicators
Full Paper:PDFEJAM Vol.6No.3 pp.24-32 "Plant Transients under Small Abnormalities of FBR “Monju” Calculated by a Plant System Code"