  A review is focused on experimental measurements on neutron lifetime. The
latest measurements with a gravitational trap (PNPI NRC KI) and a magnetic trap
(LANL, USA) confirmed PNPI result of 2005. The results of measurements with
storage of ultra cold neutrons are in agreement, yet, there is discrepancy with
a beam experiment by $3.5{\sigma}$ (1% of decay probability), which is
discussed in literature as "neutron anomaly" along with the ideas of explaining
it by decay into dark matter partially. The second part of the paper is devoted
to so called "reactor antineutrino anomaly", which refers to deficiency of the
measured flux of antineutrino from reactor in respect to the calculated flux by
$3{\sigma}$(deviation by 6.6%). Specific feature of the proposal in this paper
lies in the fact that both anomalies can be accounted for by one and the same
phenomenon of oscillation in baryon sector between a neutron and a neutron of
dark matter $n{\rightarrow}n'$ with mass $m_{n'}$, somewhat less than mass
$m_n$ of an ordinary neutron. Calculations of the proposed model require one
free parameter: mass difference $m_n-m_{n'}$ if one normalizes probability of
oscillations for a free neutron on "neutron anomaly" 1%, then, having succeeded
to interpret 6.6% of neutron anomaly in calculations, one can determine mass
difference. According to preliminary estimations, the mass difference is
$m_n-m_{n'}{\approx}$ 3 MeV. However, the analysis of cumulative yields of
isotopes occurs in fission fragments was performed and it does not confirm
possibility of existence of additional decay channel with emission of dark
matter neutron with mass difference $m_n-m_{n'}{\approx}$ 3 MeV. The result of
the analysis is the conclusion that for mirror neutrons the region of the mass
difference $m_n-m_{n'} {\geq}$ 3 MeV is closed. The region of the mass
difference $m_n-m_{n'}{\leq}$ 2 MeV turned out to be not closed.
