Managing certain by-products of the
nuclear fuel cycle, such as the radioactive isotopes of caesium: Cs-134, Cs-135
and Cs-137 is challenging due to their environmental mobility and
radioactivity. While a great many materials can isolate Cs<sup>+</sup> ions
from neutral or basic aqueous solutions via ion exchange, few of these, with
the exception of ammonium phosphomolybdate (AMP), function effectively in
acidic media. The use of AMP, and its porous composite in polyacrylonitrile
(PAN) for management of Cs radioisotopes in various nuclear wastes have been
known for decades and are well studied, yet the effects of radiation on the
physiochemical properties of such composites have only received limited
attention to date. In a previous publication, we demonstrated that a 100 kGy
gamma irradiation dose has negligible effect on the ion exchange performance of
AMP and AMP-PAN with respect to capacity or kinetics under the Cs<sup>+</sup>
concentrations and acidity found in spent fuel recycling. As a continuation of
this prior study, in this publication we explore the effects of gamma
irradiation on the physiochemical properties of AMP and AMP-PAN using a range
of characterisation methods. The effects of the same gamma dose on the
oxidation state of Mo in AMP and AMP-PAN, the thermal degradation of both AMP
and AMP-PAN, combined with a first study into the high-temperature degradation
AMP, are reported. The implications of irradiation, its possible mechanism, the
conditions present in SNF recycling, and for the end-of-life disposal or
recycling of these materials are also discussed.
The Effect of Pressure and Organic Constituents on the Cesium Ion Exchange Performance of IONSIV IE-911
