Spectrometric analysis demonstrates predictable europium-155 fission yields across varying neutron energies, indicating viable long-term nuclear forensic analysis.
As a high mass ‘wing’ fission product, the cumulative fission yield (CFY) of 156 Eu varies both with incident neutron energy and actinide isotope undergoing fission. Fission product 155 Eu should yield comparable information to that of 156 Eu long after this shorter half-life radioisotope has decayed (half-life of 4.75 years versus 15.19 days). In this context a series of solid Eu 2 O 3 mounts previously prepared for the measurement of 156 Eu have been reanalyzed for 155 Eu. Samples generated from the separation of europium from dissolved Highly Enriched Uranium (HEU) targets irradiated by thermal neutrons were used for technique development, with gamma-ray spectrometry proving to be an effective measurement technique. Utilizing this method two complimentary analyses paths were developed and then successfully applied to the measurement of sample sets where either the incident neutron and/or actinide fuels were varied. As would be expected, if the measurements were accurate and precise, 155 Eu fission yields varied in a predictable fashion with both neutron energy and actinide fuel. As further validation of the technique, the increased perturbation away from thermal fission yields as the cumulative fission yield mass chain increases was also observed (153<155<156). This was evidenced through comparison with prior analysis results for 153 Sm and 156 Eu. 155 Eu can thus be measured with a high degree of confidence in samples where both these shorter half-life radioisotopes have decayed.
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Haynes et al. (2026) studied this question.
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