  The thermonuclear explosion of massive white dwarfs is believed to explain at
least a fraction of Type Ia supernovae (SNIa). After thermal runaway, electron
captures on the ashes left behind by the burning front determine a loss of
pressure, which impacts the dynamics of the explosion and the neutron excess of
matter. Indeed, overproduction of neutron-rich species such as $^{54}$Cr has
been deemed a problem of Chandrasekhar-mass models of SNIa for a long time. I
present the results of a sensitivity study of SNIa models to the rates of weak
interactions, which have been incorporated directly into the hydrodynamic
explosion code. The weak rates have been scaled up/down by a factor ten, either
globally for a common bibliographical source, or individually for selected
isotopes. In line with previous works, the impact of weak rates uncertainties
on sub-Chandrasekhar models of SNIa is almost negligible. The impact on the
dynamics of Chandrasekhar-mass models and on the yield of $^{56}$Ni is also
scarce. The strongest effect is found on the nucleosynthesis of neutron-rich
nuclei, such as $^{48}$Ca, $^{54}$Cr, $^{58}$Fe, and $^{64}$Ni. The species
with the highest influence on nucleosynthesis do not coincide with the isotopes
that contribute most to the neutronization of matter. Among the last ones,
there are protons, $^{54,55}$Fe, $^{55}$Co, and $^{56}$Ni, while the main
influencers are $^{54,55}$Mn and $^{55-57}$Fe, in disagreement with Parikh et
al (2013), who found that SNIa nucleosynthesis is most sensitive to the
$\beta^+$-decay rates of $^{28}$Si, $^{32}$S, and $^{36}$Ar. An eventual
increase in all weak rates on pf-shell nuclei would affect the dynamical
evolution of hot bubbles, running away at the beginning of the explosion, and
the yields of SNIa.
