Health & Environmental Research Online (HERO)


Print Feedback Export to File
3028986 
Journal Article 
Analysis of Sm-149 time evolution and the reactivity contribution in nuclear reactors 
Moreira, O 
2015 
Yes 
Annals of Nuclear Energy
ISSN: 0306-4549 
83 
87-93 
WOS:000358096500011 
In this work the theory to describe atomic density time evolutions of Sm-149 and precursor Pm-149 is developed. The isotope Sm-149 is one of neutron poisons in nuclear reactors; this is the reason for studying its concentration time evolution and the associated reactivity. Here, different from other theories already existent, the Pm-149 concentration time evolution equation is corrected to neutron absorption and the production of Sm-149 due to U-235 thermal fission (fission products) is also considered. Albeit the influence of Sm-149 is lesser than that of main neutron absorber Xe-135 (mainly because of absorption cross section values) it is important to determine the Sm-149 perturbation in neutron balance equations and reactivity calculations in nuclear reactors design. Here Pm-149 and Sm-149 time evolution concentrations were calculated for different power cycles, using values for NPP Atucha U-II. The reactivity associated to Sm-149 concentration was estimated using results from two-groups energy diffusion equations. (C) 2015 Elsevier Ltd. All rights reserved. 
Reactor poisons; Reactivity coefficients; PHWR; Samarium evolution; Promethium evolution; Reactor power cycles