the rate of temperature increase was optimized to avoid anomalous combustion.
Greater than 90 % recovery was obtained for both I
À and IO 3
À , and the chemical
species in the trap solutions was observed to contain I
À .
Keywords
129 I • Combustion • Fukushima Daiichi Nuclear Power Station • Iodine
species • Isotopic exchange • Solid-phase extraction
27.1 Introduction
Because of the accident, a large amount of radioactive waste was generated at the
Fukushima Daiichi Nuclear Power Plants (FDNPP). To establish the waste management strategy, the radioactivity inventory has to be evaluated. Iodine-129 is one
of the important nuclides of which the radioactivity has to be evaluated. Although
I
À is considered a major species of
129 I generated in the reactor, IO 3
À and I 2 are
possibly generated, depending on the reactor conditions [1]. Furthermore, because
seawater was introduced to the reactors for cooling down in the early phase of the
accident and seawater contains the natural iodine species,
127 IO 3
À , an isotope
exchange reaction between
127 IO 3
À and
129 I
À may have occurred. Therefore,
analytical conditions to determine total I content, in this case IO 3
À and I
À , in
water and tree samples were investigated in the current work.
Presently, contaminated water is accumulating in the basement of the reactor and
turbine buildings at FDNPP. The accumulated water-processing equipment was
installed to decontaminate and to desalinate. Consequently, secondary waste such
as spent zeolite and sludge is generated. To evaluate the radioactivity inventory of
the waste indirectly, water samples were collected from the inflow and outflow of
the apparatus [2]. The contaminated water contains high levels of radioactivity of
137 Cs,
90 Sr, and other radionuclides. To limit radiation exposure of the analyst,
rapid chemical separation of iodine species from these radionuclides is required.
Chemical separation studies using the solid-phase extraction sorbent Anion-SR
have been reported to rapidly separate I
À from major fission products such as Cs
and Sr in contaminated water samples [3]. However, Anion-SR essentially extracts
only I
À and not IO 3
À
. Therefore, reduction of IO 3
À to I
À is required to analyze total
I. In this study, NaHSO 3 was used as the reductant and the solution conditions were
studied to reduce IO 3
À to I
À .
Because of the hydrogen explosion of FDNPP, trees on the site were contaminated
by the radionuclides. Many of the trees were cut down to provide space to install
tanks storing the contaminated water. Consequently, approximately 40,000 m
3 of
trees were stored in the site as radioactive waste [4]. A combustion method was used
to analyze
129
I in cement, ash, and soil samples [5, 6]. To apply a combustion method
for the tree samples, there were some subjects: evaporation and deposition of the
organic materials and anomalous combustion. Therefore, decomposition of organic
material to CO 2 and H 2 O using oxidant was examined. In addition, the rate of
temperature increase was controlled to avoid anomalous combustion. Furthermore,
the influence of the chemical species, IO 3
À or I
À
, on recovery was studied.
312
A. Shimada et al.
Greater than 90 % recovery was obtained for both I
À and IO 3
À , and the chemical
species in the trap solutions was observed to contain I
À .
Keywords
129 I • Combustion • Fukushima Daiichi Nuclear Power Station • Iodine
species • Isotopic exchange • Solid-phase extraction
27.1 Introduction
Because of the accident, a large amount of radioactive waste was generated at the
Fukushima Daiichi Nuclear Power Plants (FDNPP). To establish the waste management strategy, the radioactivity inventory has to be evaluated. Iodine-129 is one
of the important nuclides of which the radioactivity has to be evaluated. Although
I
À is considered a major species of
129 I generated in the reactor, IO 3
À and I 2 are
possibly generated, depending on the reactor conditions [1]. Furthermore, because
seawater was introduced to the reactors for cooling down in the early phase of the
accident and seawater contains the natural iodine species,
127 IO 3
À , an isotope
exchange reaction between
127 IO 3
À and
129 I
À may have occurred. Therefore,
analytical conditions to determine total I content, in this case IO 3
À and I
À , in
water and tree samples were investigated in the current work.
Presently, contaminated water is accumulating in the basement of the reactor and
turbine buildings at FDNPP. The accumulated water-processing equipment was
installed to decontaminate and to desalinate. Consequently, secondary waste such
as spent zeolite and sludge is generated. To evaluate the radioactivity inventory of
the waste indirectly, water samples were collected from the inflow and outflow of
the apparatus [2]. The contaminated water contains high levels of radioactivity of
137 Cs,
90 Sr, and other radionuclides. To limit radiation exposure of the analyst,
rapid chemical separation of iodine species from these radionuclides is required.
Chemical separation studies using the solid-phase extraction sorbent Anion-SR
have been reported to rapidly separate I
À from major fission products such as Cs
and Sr in contaminated water samples [3]. However, Anion-SR essentially extracts
only I
À and not IO 3
À
. Therefore, reduction of IO 3
À to I
À is required to analyze total
I. In this study, NaHSO 3 was used as the reductant and the solution conditions were
studied to reduce IO 3
À to I
À .
Because of the hydrogen explosion of FDNPP, trees on the site were contaminated
by the radionuclides. Many of the trees were cut down to provide space to install
tanks storing the contaminated water. Consequently, approximately 40,000 m
3 of
trees were stored in the site as radioactive waste [4]. A combustion method was used
to analyze
129
I in cement, ash, and soil samples [5, 6]. To apply a combustion method
for the tree samples, there were some subjects: evaporation and deposition of the
organic materials and anomalous combustion. Therefore, decomposition of organic
material to CO 2 and H 2 O using oxidant was examined. In addition, the rate of
temperature increase was controlled to avoid anomalous combustion. Furthermore,
the influence of the chemical species, IO 3
À or I
À
, on recovery was studied.
312
A. Shimada et al.