GROUPR Full Fission Source 

This exercise will make use of the RECONR and GROUPR modules
to compute the full fission source for U235, 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/BV version of the U235 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): 
reconr 20 21 'exercise 8'/ new tape ID title 1395 1/ MAT .002/ fractional tolerance '92U235'/ descriptive card for new tape 0/ groupr 20 21 0 22 1395 3 0 5 1 1 1 1/ 30group structure 'exercise 8'/ 0. 1e10 3 18/ just do the fission cross section 3 455/ delayed fission nubar 6 18/ prompt fission matrix 5 455/ delayed fission matrix 0/ 0/ stop
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.

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27 March 2000  T2 Nuclear Information Service  ryxm@lanl.gov 