報告書番号

T02010

タイトル（和文）

金属廃棄物中の放射能レベル区分評価技術の開発 -バックグラウンド補正計算の高精度化と検出性能-

タイトル（英文）

Development of technique for quantifying gamma emitters in metal waste- Highly accurate calculation for background correction and detection performance -

概要 （図表や脚注は「報告書全文」に掲載しております）

金属廃棄物がクリアランスレベルと物品持ち出し基準値以下であることを確認するために、3次元非接触式レーザー形状計測とモンテカルロ計算技術を用いた、金属廃棄物中のγ線放出核種の高精度な自動測定の新しい手法を開発した。試作機を用いた様々な試験結果と、改善したBG補正計算精度を基にして実用機の性能を推定し、他手法との比較を行なった。

概要 （英文）

A new technique of precise and automatic measurement of gamma emitters in metal waste has been developed using 3D non-contact shape measurement and Monte Carlo calculation techniques, for assessing whether the specific radioactivity level of metal waste satisfies the clearance level and whether the surface contamination level of the metal waste is below the legal standard. The technique yields a calibration factor for every measurement target automatically and automatically corrects for the reduction of background count rate in gamma measurement due to the self-shielding effect of the measurement target. The accuracy of the present method has been clarified using mock-metal wastes with various types of shape, number and size. As a result of performance estimation by the experimental apparatus, it was revealed that the reduction of background count rate due to the self-shielding effect can be corrected with an accuracy of better than 1% by the MCNP calculation for practical use, thus the detection limit is about 130 Bq. The advantage of this method was clarified by comparison with the detection limits of other methods using thicker shields or more detectors than those of the present method. This method will be useful for low-radioactivity measurement with the objecting of recycling used metal generated from the decommissioning of nuclear power plants.

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