JAEA-Data/Code 2007-004 - Welcome to Research Group for ...

Usually, enter IRES=2 for the heavy nuclide in fuel of which cross-sections
have sharp resonance structure, otherwise IRES=0. For the nuclides born during
burn-up calculation, the IRES values are given in the burn-up chain library (cf.
Sect.3.3).
When PEACO routine is used, the IRES value given in MCROSS library is
applied even if any value is entered for IRES. However, the input IRES is still
effective in the evaluation of the self-shielding factor based on the NR
approximation (applied out of the energy range of PEACO calculation).
In the tabulation of P ij for PEACO calculation, the cross-sections of
non-resonant nuclides are assumed as constant by using the value of the highest
energy group of PEACO calculation, unless IRES=3 or IRES=4 is specified.
For the systems involving coolant water with boron or control rod, the
specification of IRES=3 or IRES=4 for B-10 gives more exact treatment. However,
treatment by IRES=3 requires the P ij tabulation by energy group and that by
IRES=4 does two-dimensional tabulation. Both treatments need much computer
time.
3 IXMICR Indicator to write the effective cross-sections into the effective microscopic crosssection
file (MICREF)
= 0 No edit.
= 1 Write the effective microscopic cross-sections into the MICREF file.
= 2 Write the microscopic cross-sections of hyperfine group structure
averaged in the cell into UMCROSS file after PEACO calculation. The
seventh and eighth characters of the member name are taken from the last
half of CASENAME. During the cell burn-up calculation, the seventh
character is overridden by b-tag. This option may be utilized for the
output of former step in the treatment of double heterogeneity.
= 3 both of functions of IXMICR=1 & =2.
Note:
If the cell burn-up routine is used (IC20=1), the same option is available in Sect.
2.11 for the nuclides not appearing in this input section (e.g. MA or F.P.)
127