\section*{Acknowledgments}

The computer code TRIVAC results from a concerted effort made at \'{E}cole Polytechnique de
Montr\'{e}al. The main authors of this  report would therefore like to express their thanks to
\'{E}cole Polytechnique de Montr\'{e}al for its support along the years as well as to
the graduate students and research associates which have contributed to the development of
TRIVAC along the years. Finally, the TRIVAC  team would never have survived without  the financial
support of the  Natural Science and Engineering Research Council of Canada (NSERC),
Hydro--Qu\'{e}bec and Atomic Energy of Canada Limited (AECL).