  We present preliminary results of INTEGRAL/IBIS observations on Cas A, Tycho
and Vela Junior Supernova remnants in the line emission of 44Ti. This
radioactive nucleus is thought to be exclusively produced in supernovae during
the first stages of the explosion. It has a lifetime of about 87 y and is then
the best indicator of young SNRs, as exemplified by the detection of 44Ti in
the youngest known Galactic SNR Cas A with GRO/COMPTEL and latter with
BeppoSAX. In this paper, we will focus on this SNR for which we confirm the
detection of 44Ti and point out the importance to know the nature of the hard
X-ray continuum, the Tycho SNR, for which no indication of 44Ti was ever
reported, and Vela Junior, for which the claimed detection of 44Ti with COMPTEL
is still controversial. The INTEGRAL/IBIS observations bring new constraints on
the nature of these SNRs and on the nucleosynthesis which took place during the
explosions.
