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Experimental

Reagents

Ultrapure grade NaOH solution (3 M) was purchased from Kanto Kagaku. Ultrapure grade of tetramethyl ammonium hydroxide (TMAH) solution was purchased from Tama Chemicals. The other reagents were all analytical grade or higher and purchased from Wako Chemical. Empore solid extraction disks, Anion-SR, were purchased from 3 M. Standard solution of 129I (35.8 kBq/g 129I; chemical composition, 50 μg/g NaI and 50 μg/g Na2S2O3 in H2O) was purchased from AREVA and diluted with H2O before use. Potassium iodide (analytical grade,

99.9 %) and KIO3 (analytical standard material grade, 99.98 %) were purchased from Wako Pure Chemical Industries, and 127Iand 127IO3were prepared from these reagents, respectively, because the stable iodine isotope is only 127I.

Separation Using Anion-SR

Figure 27.1 shows the experimental procedure for the solution samples. Sodium iodide-129 (129I: 0.1 Bq ¼ 15 ng) and K127IO3(127I: 1 μg) were added to 50 ml 3 M NaOH solution or 50 ml diluted HCl solution (pH ¼ 2) with and without reductant (0.1 ml 0.1 M NaHSO3) to study iodine species behavior in the analysis using Anion-SR. After addition of the iodine species, the solutions were allowed to stand for 1 day before separation with Anion-SR. The reductant was added approximately 20 min before the separation. The operation of Anion-SR was based on Shimada et al. [3]. Briefly, the Anion SR disk was centered on the base of the filtration funnel and the reservoir was clamped on the top of the disk. The appropriate solution was poured into the reservoir followed by suction filtration The Anion-SR disk was conditioned with acetone, methanol, ultrapure water, 4 w/v% NaOH, and ultrapure water. After conditioning, the sample solution was introduced into the Anion-SR disk and washed with ultrapure water. The extracted I was recovered with 9.5 ml 1 M HNO3. To oxidize Ito IO3-, 0.1 ml NaClO solution (effective Cl concentration, >5 %) was added to the recovered solution. Addition-

ally, 0.1 ml 2 ppm Rh standard solution was added to the recovered solution as an

internal standard. Finally, 1 M HNO3 was added to the recovered solution to a final volume of 10 ml. The concentration of I was measured by inductively coupled plasma mass spectrometry with dynamic reaction cell (DRC-ICP-MS). In the reaction cell, oxygen gas was collided with ions. Because the order of ionization potential is I > O > Xe, O reacts with Xe to neutralize but I does not react with

O. As a result, the count of 129Xe, impurity of Ar gas, was decreased. The

experimental conditions of DRC-ICP-MS were consistent with the conditions reported by Kameo et al. [7]. Percent recovery was calculated as in Eq. (27.1).

Fig. 27.1 Schematic diagram of analysis of

The separation experiment to determine percent recovery was carried out twice, and the uncertainty was quantifi by the dispersion in these two measurements.

Combustion Method

A known amount of Ior IO3was added to1g pine bark, representative of tree samples taken at the establishment of the Japan Atomic Energy Agency, and the bark was put in a wet oxygen gas line set in an electric furnace. Because smoking was observed with noncontrolled temperature increase, especially around 240 oC, the rate of temperature increase in the range from 100 oC to 300 oC was controlled by steps and slow. The vaporized I was trapped in three steps of 20 ml 2 % TMAH solution. Because insoluble organic material was deposited in the gas line and the trap, an oxidant (8.2 g hopcalite II) was set between the sample and traps to decompose it (Fig. 27.2). The temperature of the oxidant was set to 500 oC before the temperature increase of the pine bark sample. The temperature of the sample was kept at 500 oC for 1 h and then increased to 900 oC for 1 h to vaporize iodine species in the sample. The extracted I in the traps was measured by DRC-ICP-MS.

Fig. 27.2 Illustration of the combustion apparatus

Table 27.1 Percent recovery of I (initially 127IO – and 129I-)

Solution condition

Without NaHSO3

With NaHSO3

127I

129I

127I

129I

3 M NaOH

2.3 ± 1.9

71.4 ± 2.9

2.1 ± 0.2

86.4 ± 4.3

HCl (pH 2)

8.6 ± 6.3

19.2 ± 4.8

64.0 ± 7.3

59.6 ± 3.1

 
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