  A new, fully dynamic and self-consistent radiation hydrodynamics code,
suitable for the calculation of supernovae light curves and continuum spectra,
is described. It is a multigroup (frequency-dependent) code and includes all
important $O(v/c)$ effects. It is applied to the model W7 of Nomoto,
Thielemann, \& Yokoi (1984) for supernovae of type Ia. Radioactive energy
deposition is incorporated through use of tables based upon Monte Carlo
results. Effects of line opacity (both static or line blanketing and expansion
or line blocking) are neglected, although these may prove to be important. At
maximum light, models based upon different treatments of the opacity lead to
values for $M_{B,max}$ in the range of -19.0 to -19.4. This range falls between
the values for observed supernova claimed by Leibundgut \& Tammann (1990) and
by Pierce, Ressler, \& Shure (1992).
