Analysis of cesium isotope compositions in environmental samples by thermal ionization mass spectrometry – 1. A preliminary study for source analysis of radioactive contamination in Fukushima prefecture

Figures & data

Table 1. Samples ID, location, and type for Cs isotope ratio analysis.

Sample ID	Sampling point	Sample type
ITT07	Iitate village	Grass (whole)
FTB01	Futaba town	Bark
FTBR35	Futaba town	Grass (roots)
OKMDNP	Okuma town	Moss

Figure 1. Example mass spectra of radioactive Cs observed in this study.

Table 2. Reproducibility of Cs isotope ratio analysis.

	^134Cs/^137Cs	^135Cs/^137Cs
Run 1	0.0314 ± 0.0002	0.3894 ± 0.0005
Run 2	0.0314 ± 0.0001	0.3898 ± 0.0003
Run 3	0.0313 ± 0.0001	0.3897 ± 0.0004
Av.	0.0313 ± 0.0001	0.3896 ± 0.0002

Note: Errors represented refer to ± 2SE.

Figure 2. Analytical precision of Cs isotope ratio as a function of amount of Cs loaded on filament (in terms of ¹³⁷Cs).

Table 3. Comparison of ¹³⁴Cs/¹³⁷Cs ratio analyzed by γ-ray spectrometry and thermal ionization mass spectrometry.

	γ-ray	TIMS
Isotopic ratio*	–	0.0313 ± 0.0001
Isotopic ratio-2^**	–	0.0711 ± 0.0002
Radioactive ratio^**	1.02 ± 0.07	1.040 ± 0.003

Notes: Errors represent here mean ± 2SE.

*: measured data obtained in October 2013.

^**: corrected on 11 March 2011.

Figure 3. Results of Cs isotope ratio analysis obtained from environmental samples in Fukushima prefecture. Contour lines of radiation dose rate were made using published data from MEXT [14]. Errors represent here mean ± 2SE. Value in square brackets represent time-corrected radioactive ratios.

Figure 4. ¹³⁵Cs/¹³⁷Cs ratios as a function of ¹³⁴Cs/¹³⁷Cs activity ratios. Isotope error bars represent ± 2SE. Plus sign (+) indicates ¹³⁴Cs/¹³⁷Cs activity ratios were corrected on 11 March 2011 values. Single asterisk (*) represents calculation results from estimation of radioactive nuclides with ORIGEN-II code [16]. Double asterisk (^**) represents values reported for ¹³⁴Cs/¹³⁷Cs activity ratio in polluted water [3].

Available from: http://www.mext.go.jp/b_menu/shingi/chousa/gijyutu/017/shiryo/__icsFiles/afieldfile/2011/09/02/1310688_1.pdf (accessed on Dec. 16, 2013).

 Google Scholar

Nishihara K, Iwamoto H, Suyama K. Estimation of fuel compositions in Fukushima-Daiichi Nuclear power plant. Japan: Japan Atomic Energy Agency; 2012, JAEA-Data/Code 2012-018 [in Japanese].

 Google Scholar

Komori M, Shozugawa K, Nogawa N, Matsuo M. Evaluation of radioactive contamination caused by each plant of Fukushima Daiichi Nuclear power plant station using 134Cs/137Cs activity ratio as an index. Bunseki Kagaku. 2013;62:475–483. [in Japanese].

 Web of Science ®Google Scholar