報告書番号

U98037

タイトル（和文）

放射性物質輸送の確率論的安全評価（その５） -INTERTRAN2コードによるケーススタディと課題の摘出-

タイトル（英文）

A Probabilistic Safety Assessment of Radioactive Materials Transport- A Case Study with INTERTRAN2 code and An Extraction of Problems-

概要 （図表や脚注は「報告書全文」に掲載しております）

当所がこれまで進めてきた確率論的安全評価（ＰＳＡ）の新たなフェイズとして、周辺環境へのリスク評価手法を開発するするために、その母体としてＩＡＥＡが開発した放射性物質陸上輸送時の被ばく線量評価用INTERTRAN2コードを取り上げた。まず、複数の陸上輸送時の被ばく線量評価コードの概要と開発の経緯について整理し、続いてINTERTRAN2コードを構成する、RADTRAN4など５つのコードについて、その構造とデータのやりとり等の関連性について分析した。 さらに、同コードの我が国の放射性物質輸送への適用性を検討するため、仮想地点における２つのルートを設定し、通常輸送時(IncidentFree)と事故時(Accident)における集団線量を計算（ケーススタディ）した。 以上の成果をもとに、同コードの課題／留意点を、実用上の視点と高度化の視点の２つの観点から、摘出分析し、対応策も提言した。

概要 （英文）

CRIEPI has been trying to adapt the PSA method to a safety assessment of radioactive materials (RAM) transport in Japan. The scenario analysis method for RAM transport accident and the estimation method of accident probabilities were developed in the first step of study. Considering the concept of “severity measure of package” in an accident, in the second step, a new approach of simulation with probabilistic distribution of parameters was proposed and “the risk curve” in a tunnel fire accident was made on trial. As the new step of environmental risk assessment, the authors decided to adopt the “INTERTRAN2 code”, which was developed by IAEA for assessing dose in incident-free or accident mode of RAM transport, as the body for development works. After comparing some dose assessment code for RAM transport which include “INTERTRAN”, ”RADTRAN”and “CRIEPI code” etc., the situations of development in those days and their relations were discussed for the purpose of identifying the position of “INTERTRAN2”. Then, 5 sub-programs, i.e. RADTRAN4, PPI, TRANSAT, TICLD and LHS, were analyzed in detail for a trial calculation. Two different routes at the hypothetical area which partially reflects the regional situation and traffic situation in Japan were selected in the trial calculation for the purpose of investigating the adaptability of “INTERTRAN2”. Shuttle transport of hypothetical LLW containers was established in this case study. The collective dose in trial calculation was evaluated in both cases of “Incident Free mode” and “Accident mode” and their subdivisions of collective dose were accorded to the definition of “INTERTRAN2”. Because of small accident probability, the results of collective dose in "Incident-Free mode" were extremly larger than those in "Accident mode." As for the difference of distance and population for two routes, it was revealed that collective dose data were properly derived from the route characteristics. Therefore, it is supposed that “INTERTRAN2 code”might be useful for any assessment prior to the start of tranport. As a result, it was confirmed that “INTERTRAN2” code was adaptable to RAM transport in Japan, although there are some problems to be solved from the viewpoint of practical use and refining with a probabilistic approach.

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