Sensitivity study on forest fire breakout and propagation conditions for forest fire hazard curve evaluations

摘要

As a part of external hazard probabilistic risk assessment methodology development, a sensitivity study on forest fire hazard curves was performed on condition parameters where frequency/probability variables were varied within respective fluctuation ranges. Important variables related to forest fire breakout time, forest fire breakout points, and forest firefighting operation were identified. The probability fluctuation on forest fire breakout time only affects the intensities of the hazard curves, but not the frequency, because the intensity increases in daytime due to sunshine and the breakout probability in daytime is statistically higher than the daily average. The hazard curves of the reaction intensity and the fireline intensity increased around 4% and 14% respectively in comparison with those without the forest fire breakout time fluctuation. The probability fluctuation on forest fire breakout points affects only the frequency of the hazard curves, but not the intensities. The hazard curves vary around +70% to -40% in frequency, because each forest fire breakout point has different distance to the plant and the forest fire arrival probability varies with propagation duration. The probability fluctuation due to forest firefighting operation only affects the frequency of the hazard curves, but not the intensity. The effect of the forest firefighting operation was conservatively assumed where there is no forest firefighting operation outside a plant, hence all potential forest fires arrive at the plant. The hazard curves remarkably increase around 40 to 80 times in frequency in comparison with those with considering the forest firefighting operation effect outside the plant. This study indicated that the most significant factor in the forest fire hazard risk is whether the forest firefighting operation outside the plant is expected before the forest fire arrival at the plant.