PNNL-13501 - Pacific Northwest National Laboratory

Summary and Conclusions
Transmutation of Tc-99 and I-129 in light water reactors
is feasible because reactors are capable of destroying
more of these wastes than they produce. These isotopes
may be mixed directly with the fuel or fabricated into
target pins. In both cases the transmutation rate is highest
when the isotopes are mixed directly with the fuel,
presumably because self-shielding in the target pins is
significant, especially for Tc-99. We therefore
recommend mixing small quantities of Tc-99 directly into
the fuel matrix.
Because of the potential corrosive nature of iodine on
cladding materials in a reactor environment, we do not
recommend mixing I-129 into the fuel. Rather, the I-129
should be bonded with vanadium as solid vanadium
iodide (VI2) and should be fabricated into annular target
pins. We recommend an annular design to accommodate
the pressure increase due to xenon buildup in the I-129
target pin, as xenon gas is a product of I-129
transmutation. We expect that 63% of the projected
Tc-99 inventory and 35% of the projected I-129 inventory
could be destroyed by 2030 if a transmutation scheme is
adopted.
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Nuclear Science and Engineering 371