Measurement of k0 values for europium, lutetium and iridium at FRM II with a very well thermalized neutron spectrum

The k0 values of 6 non-1/v nuclides (152Eu, 152mEu, 154Eu, 177Lu, 192Ir and 194Ir) were determined using the extended Høgdahl formalism at the research reactor FRM II with very high f values. Standards were irradiated in 4 channels at different local temperatures between 40 °C and 55 °C measured using temperature sensitive irreversible labels. A good agreement with the recommended values was found for 152Eu, 154Eu and 177Lu using the original g(Tn) factors by Gryntakis, however, the k0 values for 152mEu in this work were 7% higher. New k0 values were also determined using the g(Tn) factors by Van Sluijs. Differences up to 6% were found for Eu isotopes compared with the recommended values. The recommended k0 values for 192Ir and 194Ir could be confirmed using g = 1. The theoretical k0 values for 177Lu were calculated using new nuclear data. They are up to 6% less than the recommended values. The present k0 values determined in this work showed a similar trend. The influence of different g(Tn) factors on the determination of the k0 values was investigated.

The Effect of Irradiation on Ni-Containing Components in CANDU® Reactor Cores: A Review

For nickel-containing alloys irradiated in thermalized neutron fluxes, the formation and reaction of 59 Ni with thermal neutrons can lead to time-varying changes in displacement damage rate, expressed as displacements per atom per second (dpa.s -1 ), gas formation and nuclear heating. Ni-rich alloys are used in PWR and BWR reactors as spacers within fuel assemblies but also as tensioning springs for these same assemblies. Flux thimbles have also been made from Ni-rich alloys in the past but are gradually being replaced by thimbles made from other alloys containing substantially less Ni. In a CANDU® reactor, Ni-alloys are used as tensioning springs, fuel channel spacers (in the form of garter springs) and as cable sheathing and core wires in flux-detector assemblies. Prediction of the irradiation processes that affect the functionality of these CANDU internals, such as irradiation embrittlement and irradiation creep, especially under conditions of extended operation, necessitates a consideration of the effect of the transmutation of Ni. Over the past 10 years, there has been a considerable increase in the understanding of the effects of irradiation on the properties of components made from Ni-rich alloys. The nuclear processes and the effects of irradiation damage on the performance of components made from these alloys will be described.