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Okano, Yasushi; Yamano, Hidemasa
Proceedings of Asian Symposium on Risk Assessment and Management 2017 (ASRAM 2017) (USB Flash Drive), 3 Pages, 2017/11
Forest fire hazard assessment methodologies using a logic tree have been applied for the evaluation of combination hazard curves of a forest fire with lightning as an initiator of a forest fire and with a strong wind being independent from a forest fire. The complex shape of the combinational hazard curve of forest fire and lighting is due to that both lightning and high velocity wind tend to appear under unstable weather conditions, and there is correlation between two hazards. The evaluated combinational hazard curve of forest fire and strong wind for the instantaneous wind velocity over 80 m/s has extremely small frequency in the range below 10
/year.
Shimomura, Yusuke; Hanari, Akira*; Sato, Isamu*; Kitamura, Ryoichi
JAEA-Technology 2015-062, 47 Pages, 2016/03
JAEA-Technology-2015-062.pdf:1.85MB
In response to new standards for regulating waste management facilities, it was carried out impact assessment of forest fires on the waste management facilities existed in Oarai Research and Development Center of Japan Atomic Energy Agency. At first, a fire spread scenario of forest fires was assumed. The intensity of forest fires was evaluated from field surveys, forest fire evaluation models and so on. As models of forest fire intensity evaluation, Rothermel Model and Canadian Forest Fire Behavior Prediction (FBP) System were used. Impact assessment of radiant heat to the facilities was carried out, and temperature change of outer walls for the assumed forest fires was estimated. The outer wall temperature of facilities was estimated around 160
C at the maximum, it was revealed that it doesn't reach allowable temperature limit. Consequently, it doesn't influence the strength of concrete. In addition, a probability of fire breach was estimated to be about 20%. This report illustrates an example of evaluation of forest fires for the new regulatory standards through impact assessment of the forest fires on the waste management facilities.
Okano, Yasushi; Yamano, Hidemasa
Proceedings of International Topical Meeting on Probabilistic Safety Assessment and Analysis (PSA 2015) (USB Flash Drive), p.22 - 31, 2015/04
An external hazard curve of a forest fire is evaluated based on a logic tree. The logic tree consists domains of "forest fire breakout and spread conditions", "weather condition" and "vegetation and topographical conditions". A location nearby a typical nuclear power plant site in Japan was selected, and the frequency of a large forest fire of the location is approximately 1/5 of the average in Japan. Forest fire breakout points were selected considering typical forest fire causes in Japan. The weather conditions are represented by two parameter sets of "temperature-humidity" and "wind direction-wind speed". A number of forest fire simulations were performed to obtain a response surface for a frontal fireline intensity. The hazard curve is therefore evaluated by a Monte Carlo simulation such that the annual exceedance probability is about 1.0
10
per year for the frontal fireline intensity of 200 kW/m and about 1.310
per year for 300 kW/m.
Okano, Yasushi; Yamano, Hidemasa
no journal, ,
There has been an increased concern in the safety of NPP for external hazards, one of which is a forest fire. Conventional forest fire assessments have been performed with deterministic and conservative manner, using so-called envelope initial and boundary conditions on forest fire analyses. In this study, the forest fire hazard assessment methodology, which is subject to an external-hazard probabilistic risk assessment (PRA), is being developed in order to quantitatively evaluate frequency and consequence of the forest fire that has a potential impact on a NPP and then to obtain the Core Damage Frequency. The new methodology based on a logic tree is developed in this study, as well as the sensibility analyses on weather conditions.
Okano, Yasushi; Yamano, Hidemasa
no journal, ,
As a part of the development of forest fire hazard assessment method and event sequence analyses method for a sodium-cooled fast reactor, this paper describes the analysis of hazard curves of fireline intensity and reaction intensity as heat and flame effects of a forest fire by a logic tree improvements, response surface evaluations, and Monte Carlo simulations applying importance sampling.
Okano, Yasushi; Yamano, Hidemasa
no journal, ,
For an evaluation of a combination hazard curve of forest fire and thunder, it is necessary to take into account not only the overlap occurrence frequency but also meteorological effect on a forest fire intensity. The logic tree of a forest fire hazard curve evaluation was utilized in this study for quantitative estimation of the hazard curve of the combination event of forest fire and thunder.
Ueyama, Masahito*; Iwata, Hiroki*; Nagano, Hirohiko; Tahara, Narumi*; Harazono, Yoshinobu*
no journal, ,
no abstracts in English