  We compute the decay rate for the CKM-suppressed electromagnetic penguin
decay $B \to X_d + \gamma$ (and its charge conjugate) in NLO QCD, including
leading power corrections in $1/m_b^2$ and $1/m_c^2$ in the standard model. The
average branching ratio of the decay $B \to X_d\gamma$ and its charge conjugate
is estimated to be in the range $6.0 \times 10^{-6} \leq <BR(B \to X_d \gamma)>
\leq 2.6 \times 10^{-5}$, obtained by varying the CKM-Wolfenstein parameters
$\rho$ and $\eta$ in the range $-0.1 \leq \rho \leq 0.4$ and $0.2 \leq \eta
\leq 0.46$ and taking into account other parametric dependence. In the stated
range of the CKM parameters, we find the ratio $R(d\gamma/s\gamma) = <BR(B \to
X_d\gamma)>/<BR(B \to X_s\gamma)>$ to lie in the range between 0.017 and 0.074.
Theoretical uncertainties in this ratio are found to be small. Hence, this
ratio is well suited to provide independent constraints on the CKM parameters.
The CP-asymmetry in the $B \to X_d \gamma$ decay rates is found to be in the
range $(7 - 35)%$. Both the decay rates and CP asymmetry are measurable in
forthcoming experiments at $B$ factories and possibly at HERA-B.
