Exercise 8:
GROUPR Full Fission Source

This exercise will make use of the RECONR and GROUPR modules to compute the full fission source for U-235, including both prompt and delayed parts. We are just doing the calculation at zero Kelvin and infinite dilution for simplicity.

Copy t511 from the NJOY distribution to tape20. This file contains the ENDF/B-V version of the U-235 cross sections. Create a file named in8 containing the following lines (as usual, you can leave off the comments to the right of the slash symbol):

           20 21
           'exercise 8'/    new tape ID title
           1395 1/          MAT
           .002/            fractional tolerance
           '92-U-235'/      descriptive card for new tape
           20 21 0 22
           1395 3 0 5 1 1 1 1/  30-group structure
           'exercise 8'/
           3 18/  just do the fission cross section
           3 455/ delayed fission nubar
           6 18/  prompt fission matrix
           5 455/ delayed fission matrix

Run the NJOY job, and then look at the resulting output file.

1. Where does energy dependence begin for the prompt fission matrix? Note that a spectrum and a fission neutron production cross section are given in this range.

2. Check File 5 for MT=18 and explain why the beginning of energy dependence identified in #1 occurs where it does.

3. What is the total nubar at thermal energies (.025 eV)? What is the total nubar near 14 MeV? Hint: You will need to use the fission cross section.


27 March 2000 T-2 Nuclear Information Service ryxm@lanl.gov