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論文

NRDの開発,2; NRTAによる面密度測定に対するサンプル厚の系統的な影響の検証

土屋 晴文; 原田 秀郎; 小泉 光生; 北谷 文人; 高峰 潤; 呉田 昌俊; 飯村 秀紀; 木村 敦; Becker, B.*; Kopecky, S.*; et al.

核物質管理学会(INMM)日本支部第35回年次大会論文集(インターネット), 9 Pages, 2015/01

福島第一原子力発電所での過酷事故のような事例で発生するとされる粒子状溶融燃料デブリ中の核物質を非破壊で定量することを目的とし、中性子共鳴透過分析法(NRTA)と中性子共鳴捕獲$$gamma$$線分析法を合わせた中性子共鳴濃度分析法(NRD)を開発している。NRDの開発のために、IRMMの中性子飛行時間施設GELINAにて、NRTA実験を行った、実験では、サンプル厚の効果を調べるため、異なる厚みの銅サンプルを用い、混合物の影響を検証するために、銅にB$$_{4}$$Cを重ねたサンプルを用いた。銅の面密度を得るには、共鳴解析コードREFITを用いた。その結果、推奨共鳴パラメータを使った解析で得た面密度は、サンプルの質量や面積から計算した面密度から大きくずれるとわかった。そこで、実験データから銅の中性子幅を新たに求め、面密度が期待値と2%以内で一致することを確かめた。加えて、混合物のNRTA測定に与える影響も議論する。

論文

Impact of systematic effects on results of neutron resonance transmission analysis

土屋 晴文; 原田 秀郎; 小泉 光生; 北谷 文人; 高峰 潤; 呉田 昌俊; 飯村 秀紀; 木村 敦; Becker, B.*; Kopecky, S.*; et al.

Nuclear Instruments and Methods in Physics Research A, 767, p.364 - 371, 2014/12

 被引用回数:6 パーセンタイル:36.56(Instruments & Instrumentation)

中性子共鳴吸収透過法(NRTA)による面密度の測定に対するサンプル厚の影響を検証するために、EC/JRC/IRMMの中性子飛行時間施設GELINAにおいて、NRTA実験を実施した。実験では、厚みの異なる円盤状の銅金属を用いて、GELINAの25m飛行導管を利用した。実験データから面密度を導出するために、共鳴解析コードREFITを用いて、共鳴解析を行った。その結果、推奨共鳴パラメータ値を用いると、求めた面密度が質量や面積から計算できる面密度から大きくずれることがわかった。そこで、0.25mm厚のサンプルを用いた実験データをREFIT用いて解析して、中性子幅と共鳴エネルギーを導出した。新たに求めた共鳴パラメータ値を使って、面密度を導出し、サンプルの厚みはもちろん、共鳴の強さが面密度の測定におよぼす影響を議論した。

論文

Thickness and mixed sample effects on areal density measurement with NRTA for particle like debris of melted fuel

土屋 晴文; 原田 秀郎; 小泉 光生; 北谷 文人; 高峰 潤; 呉田 昌俊; 飯村 秀紀; 木村 敦; Becker, B.*; Kopecky, S.*; et al.

Proceedings of INMM 55th Annual Meeting (Internet), 6 Pages, 2014/07

Neutron resonance densitometry (NRD) is based on a combination of neutron resonance transmission analysis (NRTA) and neutron resonance capture analysis (NRCA). This technique is a non-destructive method to quantify nuclear materials in particle-like debris of melted fuel that is generated by a severe accident like the one at the Fukushima Daiichi Nuclear Power Plant. To verify the effectiveness of NRD, the Japan Atomic Energy Agency (JAEA) and the Joint Research Center, Institute for Reference Materials and Measurements (EC-JRC-IRMM) started collaboration in 2012. One of the main objectives of this collaboration is to quantitatively investigate all uncertainty components on results of NRD measurements. Clearly, systematic effects due to the characteristics of samples such as the sample inhomogeneity, presence of impurities, radioactivity and temperature have a strong impact on the accuracy. To study the uncertainty due to the sample characteristics, NRTA and NRCA experiments are in progress at the time-of-flight facility GELINA (Geel Electron LINear Accelerator) of the EC-JRC-IRMM. In this presentation, we show results considering mixed sample effect on NRTA measurements. Data are analyzed with the resonance shape analysis code REFIT to derive the elemental composition of the sample and the areal density of the main components. In addition the effect of neutron absorbing matrix material will be discussed.

論文

Development of neutron resonance densitometry

原田 秀郎; Schillebeeckx, P.*; 土屋 晴文; 北谷 文人; 小泉 光生; 高峰 潤; 呉田 昌俊; 飯村 秀紀; 木村 敦; 瀬谷 道夫; et al.

Proceedings of INMM 55th Annual Meeting (Internet), 8 Pages, 2014/07

Neutron resonance densitometry (NRD) has been developed to quantify nuclear materials in particle-like debris of melted fuel formed in severe accidents of nuclear reactors such as Fukushima Daiichi Nuclear Power Plants. NRD is a method combining NRTA (neutron resonance transmission analysis) and NRCA (neutron resonance capture analysis). It relies on neutron TOF technique using a pulsed white neutron source. A specially designed $$gamma$$-ray spectrometer for NRCA has been developed for the characterization of contamination materials mixed with nuclear fuel materials. Achievable accuracy is studied based on Monte Carlo simulations and experimental data measured at the time-of-flight facility GELINA of the EC-JRC-IRMM. Analysis method of NRTA for particle-like debris has been developed by adding a function in a resonance analysis code REFIT. In this contribution, these achievements on NRD for the characterization of nuclear materials mixed with highly radioactive nuclides are reviewed, and its applicability is discussed.

論文

Particle size inhomogeneity effect on neutron resonance densitometry

Becker, B.*; 原田 秀郎; Kauwenberghs, K.*; 北谷 文人; 小泉 光生; Kopecky, S.*; Moens, A.*; Schillebeeckx, P.*; Sibbens, G.*; 土屋 晴文

ESARDA Bulletin, (50), p.2 - 8, 2013/12

Neutron Resonance Densitometry (NRD) represents a possible option to determine the heavy metal content in melted nuclear fuel. This method is based on the well-established methodology of neutron time-of-flight (TOF) transmission and capture measurements. In particular, NRD can measure both the isotopic and the elemental composition. It is a non-destructive method and is applicable for highly radioactive material. The details of this method are explained in another contribution to this symposium. The accuracy of NRD depends among other factors on sample characteristics. Inhomogeneities such as density variations in powder samples can introduce a significant bias in the determination of the composition. In this contribution, the impact of the particle size distribution of such powder samples on results obtained with NRD is investigated. Various analytical models, describing the neutron transport through powder, are compared. Stochastic numerical simulations are used to select a specific model and to estimate the introduced model uncertainty. The results from these simulations will be verified by dedicated measurements at the TOF-facility GELINA of the EC-JRC-IRMM.

論文

Development of neutron resonance densitometry at the GELINA TOF facility

Schillebeeckx, P.*; Abousahl, S.*; Becker, B.*; Borella, A.*; Emiliani, F.*; 原田 秀郎; Kauwenberghs, K.*; 北谷 文人; 小泉 光生; Kopecky, S.*; et al.

ESARDA Bulletin, (50), p.9 - 17, 2013/12

Neutrons can be used as a tool to study properties of materials and objects. An evolving activity in this field concerns the existence of resonances in neutron induced reaction cross sections. These resonance structures are the basis of two analytical methods which have been developed at the EC-JRC-IRMM Neutron Resonance Capture Analysis (NRCA) and Neutron Resonance Transmission Analysis (NRTA). They have been applied to determine the elemental composition of archaeological objects and to characterize nuclear reference materials. A combination of NRTA and NRCA together with Prompt Gamma Neutron Analysis, referred to as Neutron Resonance Densitometry (NRD), is being studied as a non-destructive method to characterize particle-like debris of melted fuel that is formed in severe nuclear accidents such as the one which occurred at the Fukushima Daiichi Nuclear Power Plants. This study is part of a collaboration between JAEA and EC-JRC-IRMM. In this contribution the basic principles of NRTA and NRCA are explained based on the experience in the use of these methods at the time-of-flight facility GELINA of the EC-JRC-IRMM. Specific problems related to the analysis of samples resulting from melted fuel are discussed. The programme to study and solve these problems is described and results of a first measurement campaign at GELINA are given.

論文

NRTAによる粒子状溶融燃料デブリ中の核物質定量化に対するサンプルの厚さの影響

土屋 晴文; 原田 秀郎; 小泉 光生; 北谷 文人; 高峰 潤; 呉田 昌俊; 飯村 秀紀; Becker, B.*; Kopecky, S.*; Kauwenberghs, K.*; et al.

核物質管理学会(INMM)日本支部第34回年次大会論文集(インターネット), 8 Pages, 2013/10

福島第一原子力発電所の事故のような現象で発生する粒子状の溶融燃料デブリの核物質を定量するため、中性子共鳴濃度分析法を開発している。これは、中性子共鳴透過分析法(NRTA)と中性子共鳴捕獲$$gamma$$線分析法を組合せたものである。デブリは、形状や大きさ、含まれる不純物の量などに関して、大きなばらつきがあると予測される。こうした不確定性が測定の精度にどのような影響を与えるのかを把握する一環として、サンプルの厚みが中性子共鳴透過測定に与える影響を調べた。2012年12月から2013年2月にIRMMの中性子飛行時間測定施設で、厚みが0.125, 0.25, 0.7mmと異なる銅のサンプルを用いて測定を実施した。得られたデータから、厚みごとの面密度を導出し、それらは2%以内で期待される面密度と一致することを確認した。

論文

Sample thickness effect on nuclear material quantification with NRTA for particle like debris of melted fuel

土屋 晴文; 原田 秀郎; 小泉 光生; 北谷 文人; 高峰 潤; 呉田 昌俊; 飯村 秀紀; Becker, B.*; Kopecky, S.*; Kauwenberghs, K.*; et al.

Proceedings of INMM 54th Annual Meeting (CD-ROM), 6 Pages, 2013/07

Neutron resonance densitometry (NRD) is based on a combination of neutron resonance transmission analysis (NRTA) and neutron resonance capture analysis (NRCA). This non-destructive technique is considered for the quantification of nuclear materials in samples of melted fuel that will be removed from the Fukushima Daiichi Nuclear Power Plant. However, NRD has never been applied for measurements of melted fuel, and the measurements are considered to be difficult because of the characteristics of the samples. To verify the effectiveness of NRD, all components having an impact on the results have to be investigated. The uncertainty of the result is strongly influenced by the characteristics of the sample, in particular the sample inhomogeneity, particle size, presence of neutron absorbing impurities, radioactivity and temperature. To estimate the impact of the sample characteristics, JAEA and JRC-IRMM have started a collaboration. Within this collaboration experiments are in progress at the Time-Of-Flight facility of the EC-JRC-IRMM. In this presentation, results of neutron transmission measurements on Cu samples with different thicknesses at a 25-m flight path are reported. The data, which are analyzed with a resonance shape analysis code REFIT, are used to verify the effect of the particle size and the presence of neutron absorbing impurities. Some of the results are also used to validate data obtained by Monte Carlo simulations.

論文

Contribution of the JRC to the development of neutron resonance densitometry to characterize melted fuel from severe accidents

Schillebeeckx, P.*; Becker, B.*; Emiliani, F.*; Kopecky, S.*; Kauwenberghs, K.*; Moens, A.*; Mondelaers, W.*; Sibbens, G.*; 原田 秀郎; 北谷 文人; et al.

Proceedings of INMM 54th Annual Meeting (CD-ROM), 7 Pages, 2013/07

JAEA and EC-JRC started a collaboration to study Neutron Resonance Densitometry (NRD) as a method for the characterization of melted fuel formed in nuclear accidents. NRD is based on a combination of Neutron Resonance Transmission Analysis (NRTA) and Neutron Resonance Capture Analysis (NRCA). In this presentation, the contribution of the EC-JRC-IRMM to the project is discussed. Within the project the GELINA facility will be used to validate the method and perform tests on calibration and test samples. In a first exercise the test samples will not contain actinides, however, they will contain nuclides having similar characteristics as the melted fuel for NRCA and NRTA. These samples will be produced and characterized at dedicated laboratories of our institute. To study the impact of the sample characteristics, in particular the particle size distribution of powder samples, various analytic models are compared. In addition stochastic simulations are used to select a specific model and to estimate the uncertainties introduced by the model. The stochastic model is also used to verify bias effects due to sample properties. The results of the simulations are verified by measurements at GELINA. In addition, the data reduction and analysis procedures will be adapted such that they can be used for in-field application of NRD. The changes required for NRD applications are discussed.

論文

Contribution of the JRC to the development of neutron resonance densitometry to characterize melted fuel from severe accidents

Schillebeeckx, P.*; Becker, B.*; Emiliani, F.*; Kopecky, S.*; Kauwenberghs, K.*; Moens, A.*; Mondelaers, W.*; Sibbens, G.*; 原田 秀郎; 北谷 文人; et al.

Proceedings of INMM 54th Annual Meeting (CD-ROM), 7 Pages, 2013/07

Neutron resonance densitometry (NRD) is proposed as a non-destructive method to characterize particle like debris originating from severe nuclear accidents such as the one occurred at the Fukushima Daiichi Nuclear Power Plants. The method strongly relies on the use of Neutron Resonance Transmission Analysis (NRTA) to quantify the amount of special nuclear materials present in the debris. In this contribution the basic principles of NRTA are explained based on measurements performed at the time-of-flight facility GELINA installed at the EC-JRC-IRMM. In addition, the main systematic effects affecting the accuracy of the results are discussed, with a special emphasis on the variety in shape and size of the particle like debris samples. To verify the impact of the particle size distribution various analytical models have been compared and validated by results of both stochastic numerical calculations and NRTA experiments at GELINA. Results of a preliminary analysis of the experimental data are presented.

論文

Particle size inhomogeneity effect on neutron resonance densitometry

Becker, B.*; 原田 秀郎; Kauwenberghs, K.*; 北谷 文人; 小泉 光生; Kopecky, S.*; Moens, A.*; Schillebeeckx, P.*; Sibbens, G.*; 土屋 晴文

Proceedings of 35th ESARDA Annual Meeting (Internet), 7 Pages, 2013/05

Neutron Resonance Densitometry (NRD) represents a possible option to determine the heavy metal content in melted nuclear fuel. It is a non-destructive method and is applicable for highly radioactive material. The accuracy of NRD depends among other factors on sample characteristics. Inhomogeneities such as density variations in powder samples can introduce a significant bias in the determination of the composition. In this contribution, the impact of the particle size distribution of such powder samples on results obtained with NRD is investigated. Various analytical models, describing the neutron transport through powder, are compared. Stochastic numerical simulations are used to select a specific model and to estimate the introduced model uncertainty. The results from these simulations will be verified by dedicated measurements at the TOF-facility GELINA of the EC-JRC-IRMM.

論文

Development of neutron resonance densitometry at the GELINA TOF facility

Schillebeeckx, P.*; Abousahl, S.*; Becker, B.*; Borella, A.*; Emiliani, F.*; 原田 秀郎; Kauwenberghs, K.*; 北谷 文人; 小泉 光生; Kopecky, S.*; et al.

Proceedings of 35th ESARDA Annual Meeting (Internet), 11 Pages, 2013/05

Neutron Resonance Capture Analysis (NRCA) and Neutron Resonance Transmission Analysis (NRTA) have been applied to determine the elemental composition of archaeological objects and to characterize nuclear reference materials. A combination of NRTA and NRCA, referred to as Neutron Resonance Densitometry (NRD), is being studied as a non-destructive method to characterize particle-like debris of melted fuel that is formed in severe nuclear accidents such as the one which occurred at the Fukushima Daiichi Nuclear Power Plants. This study is part of a collaboration between JAEA and EC-JRC-IRMM. In this contribution the basic principles of NRTA and NRCA are explained based on the experience in the use of these methods at the time-of-flight facility GELINA of the EC-JRC-IRMM. Specific problems related to the analysis of samples resulting from melted fuel are discussed. The programme to study and solve these problems is described and results of a first measurement campaign at GELINA are given.

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