  The pionic decay of a possible d'-dibaryon in the process d' --> pi + N + N
is studied in the microscopic quark shell model and with a single-quark
transition operator describing the transition q --> pi + q'. For the d' with
quantum numbers J^P=0^-, T=0, we employ a six-quark shell-model wave function
with a spatial s^5p [51]_X-configuration with N=1 harmonic oscillator quanta.
It is shown that the pionic decay width depends strongly on the mass and size
of the d'. In the case that the calculated d' mass is close to the experimental
one a small pionic decay width of 0.04 MeV is obtained. This is an order of
magnitude smaller than the experimentally suggested value of 0.5 MeV. Two
possibilities to improve the calculated width are suggested. The effect of the
nonstatic correction term in the transition operator and the influence of the
form factor at the decay vertex on the decay width are also discussed.
