検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年

Estimation of source term uncertainty in a severe accident with correlated variables

変数の相関を考慮したシビアアクシデント時におけるソースタームの不確かさ評価

Zheng, X.; 伊藤 裕人; 玉置 等史; 丸山 結

Zheng, X.; Ito, Hiroto; Tamaki, Hitoshi; Maruyama, Yu

BWRのシビアアクシデント時におけるソースタームの評価を目的として、福島第一原子力発電所2号機の事故を例にとり、シビアアクシデント総合解析コードMELCOR (Ver.1.8.5)を用いた不確かさ解析を実施した。最初のステップとして、炉内溶融進展挙動及び放射性物質移行挙動モデルに係わる主要なパラメータを抽出し、Morris法によりパラメータの絞り込みを行なった。得られた各パラメータの不確かさ分布及びパラメータ間の相関を設定した後、Iman-Conover法による順位相関を考慮したラテン超方格サンプリング(LHS)法を用いて入力データセット作成し、Cs, CsI等の格納容器外放出量について不確かさを評価した。合わせて、相関係数に基づいてソースタームに大きく寄与するパラメータを検討し、炉心コンポーネントや構造物の破損、エアロゾルのプールスクラビングに係わるモデル等がソースタームの不確かさに大きな影響を及ぼすことを明らかにした。

Integral severe accident code MELCOR 1.8.5 has been applied to estimating uncertainty of source term for the accident at Unit 2 of Fukushima Daiichi Nuclear Power Plant and to discussing important models or parameters influential to the source term. Forty-two parameters associated with models for the transportation of radioactive materials were chosen and narrowed down to 18 through a set of screening analysis. These 18 parameters in addition to 9 parameters relevant to in-vessel melt progression obtained by the preceded uncertainty study were inputted to the subsequent sensitivity analysis by Morris method. This one-factor-at-a-time approach can preliminarily identify inputs which have important effects on an output, and 17 important parameters were selected from the total of 27 parameters through this approach. The selected parameters have been integrated into uncertainty analysis by means of Latin Hypercube Sampling technique and Iman-Conover method, taking into account correlation between parameters. Cumulative distribution functions of representative source terms were obtained through the present uncertainty analysis assuming the failure of suppression chamber. Correlation coefficients between the outputs and uncertain input parameters have been calculated to identify parameters of great influences on source terms, which include parameters related to models on core components failure, models of aerosol dynamic process and pool scrubbing.

Access

:

- Accesses

InCites™

:

Altmetrics

:

[CLARIVATE ANALYTICS], [WEB OF SCIENCE], [HIGHLY CITED PAPER & CUP LOGO] and [HOT PAPER & FIRE LOGO] are trademarks of Clarivate Analytics, and/or its affiliated company or companies, and used herein by permission and/or license.