実験報告書様式（一般利用課題・成果公開利用）（ ※本報告書は英語で記述してください。ただし、産業利用課題として採択されている方は日本語で記述していただいても結構です。 ）MLF Experimental Report

提出日 Date of Report

課題番号 Project No.

装置責任者 Name of responsible person

2014B0008

Yosuke Toh

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Feasibility of time-of-flight prompt gamma-ray analysis for

ANNRI / BL04

radioactive waste at Fukushima Daiichi and nuclear waste

実施日 Date of Experimentmanagement

16/Apr/2015 – 19/Apr/2015

実験責任者名 Name of principal investigator
Yosuke Toh所属 Affiliation
Japan atomic energy agency
試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
Tc-99 78mg,54.7mg (TcO2)
Pd-107 21mg
Ru 176mg
Rh 39.4mg
Pd 78.8mg
Ad 11.8mg

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

In this study, we used the Ge detector array, a combination of two cluster-Ge detectors, eight large coaxial-Gedetectors and BGO anti-Compton shields surrounding cluster-Ge and coaxial Ge detectors, is installed at theflight path length of 21.5 m in ANNRI. For improvements of the accuracy and sensitivity, we have developed anovel non-destructive multi-elemental analytical technique which combines prompt gamma-ray analysis with
time-of-flight technique (TOF-PGA) in J-PARC ANNRI [1]. A key advantage of the developed method is thatfive types of spectra can be obtained simultaneously, namely, PGA, TOF, MPGA, TOF-PGA, and TOF-MPGAspectra. A PGA spectrum shows gamma-ray counts at a given energy. In contrast, a TOF spectrum shows has
three dimensions and plots the energy of the gamma-ray on the X axis, the time-of-flight on the Y axis, andgamma-ray counts at the time of the flight of the neutron that is captured in a sample.

1

2. 実験方法及び結果（つづき） Experimental method and results (continued)

(b)

(a)

Fig.1. PGA and TOF spectra are shown in (a) and (b), respectively.

The TOF-PGA spectrum has three dimensions and plots the energy of the gamma-ray on the X axis, thetime-of-flight on the Y axis, and the number of counts on the Z axis. An MPGA spectrum, which is also a three
dimensional spectrum, is constructed with events comprising a pair of prompt γ rays. The SNR values of these
spectra depend on the element (or nucleus) which has a specific multiplicity of a prompt gamma ray and specificenergies of resonance peaks.
The platinum-group metals (PGEs) generated from four-group partitioning process including radioisotopes
Tc-99 and Pd-107 are irradiated by a pulsed neutron for approximately for 3 or 6 hours. The figure 1 (a) shows
the PGA spectra of Pd-107 and Tc-99. We observed several strong prompt gamma-ray peaks from Pd-107 andTc-99 in the spectra. TOF spectra of Pd-107 and Tc99 is shown in the fig.1(b). The neutron capture resonancepeaks of Tc-99 only are clearly shown. On the other hand, in the TOF spectrum of Pd-107, the resonance peaksof Pd-107 as well as trace impurity elements are observed. We also measured the simulated sample of four-group
partitioning process. In this case, severe peak overlaps occurred in both PGA and TOF spectra because most ofnuclei emits many gamma rays and have a large number of resonance peaks. By contrast, TOF-PGA method
allows us to eliminate or at least to greatly suppress the interference from the other elements. Thus we reasonably
conclude that the developed method allows significant improvements in the SNR values and provides
correspondingly more accurate results. The results will be also submitted to a peer reviewed journal inthe near future.
[1] Y. Toh et al., Anal.Chem. 2014,86,12030-12036

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