Qs on radiation models

Bo

+--------------------------------------------------------------------+

| I-Radiation | #Its | Vol Chg | Sur Chg | %Lost %Imbal |

| Gray | 3 | 0.0E+00 | 1.3E-03 | 0.00 2.71 |

Comes from a .out file applying Discrete Transfer Method.

+--------------------------------------------------------------------+

| I-Radiation | | %SD Sur | %SD Vol | %Lost %Imbal |

| Full Spectrum | | 5.0E+01 | 1.0E+02 | 0.00 0.34 |

+----------------------+------+---------+---------+------------------+

Comes from a .out file applying Monte Carlo Method.

What's the meanings of "Vol Chg", "Sur Chg", and "%SD" ? Are they also a standard of convergence, how accurate for the figures 0.0E+00, 1.3E-03(DT) and 50, 100(Monte Carlo) here? If the convergence is not nice enough, how can I improve it?

Thank you in advance.

Bo