報告書番号

U99058

タイトル（和文）

放射性物質輸送の確率論的安全評価（その6） -－輸送リスクのゆらぎ評価方法の提案－-

タイトル（英文）

A Proposal of Ealuation Method on Fluctuation of RAM transport risk

概要 （図表や脚注は「報告書全文」に掲載しております）

放射性物質輸送を対象にINTERTRAN2を用いてリスク評価を行う際に、入力変数のゆらぎが出力結果に与える影響を検討した。具体的には、まずINTERTRAN2の多くの入力項目のうち人口密度、交通量、風速など６つの入力変数について統計データ等から確率分布を作成した。次に、入力変数のサンプリング法として、確率密度を考慮して等密度となるよう階層化し、それぞれの区間から異なる組み合わせを選び出すLatin Hypercube Sampling法を採用し、現実の輸送ルートの特定区間における被ばく線量（被ばくリスク）のゆらぎ（分布形状）を検討した。その結果、今回のモデルでは最大値／平均値および標準偏差／平均値の比が、通常輸送時でそれぞれ４．６倍と０．４１倍、事故時被ばくリスクで１５倍と１．４倍となった。また、同区間の特定地点における方位別の最大／最小値比較では、通常時２．５倍、事故時３３倍を得た。

概要 （英文）

This report describs an evaluation method of fluctuation in risk assessment with INTERTRAN2 code for RAM transport.As the first step, a lot of input items for INTERTRAN2 were prepared from various domestic statistics. As the second step, Latin Hypercube Sampling method was investigated and adopted for sampling of input variables. As a mathematical statistics feature of this method, classification of probability distribution of discussed function and exclusive sampling(ten samplings from each of 50 classifications) of input variables should be noticed. From the view of sampling efficiency, the LHS method needs much less number of sampling than Monte-Carlo sampling. Then, for the purpose of automatic calculation, some programming including the LHS sampling and probability distribution of output dose were tried and a case study of the actual fresh fuel tranport was executed for verification of this method. As the result, fluctuatoin of output dose were discovered as the ratio of maximum value to average, 4.6 for incident-free mode and 15 for accident mode. Furthermore, dose distribution of each direction was calculated and compared for future appliation to disaster prevention of nuclear industry. At the specific site, the maximum and minimum dose ratios of whole directions, 2.5 for incident-free mode and 33 for accident mode, were calculated respectively. These values are expected to be used for public acceptance.

報告者

キーワード