Exercise 1: Simple Cross Sections

 Use your text editor to open the file T511 as provided with the NJOY97 package. This is the "Standards" tape from ENDF/B-V. Search for the beginning of the elastic cross section tabulation (Hint: look for MAT=1301, MF=3, and MT=2): What is the elastic cross section at 0.0253 eV? This is the nominal energy used in ENDF files for room temperature. What is the mathematical shape of this cross section at low energies? Where does the cross section begin to deviate from its low-energy shape? What interpolation law is specified for elastic scattering? What is the elastic scattering cross section at .0015 eV? Search for the beginning of the radiative capture cross section (MT=102): What is the capture cross section at 0.0253 eV? What is the mathematical shape of this cross section at low energies? Where does the cross section begin to deviate from its low-energy shape? What interpolation law is specified for capture? What is the capture cross section at .0015 eV? Search for the beginning of the total cross section (MT=1): Does the total cross section at 0.0253 eV match the sum of the elastic and capture cross sections? Compute the total cross section at .0015 eV using linear interpolation. What is the percent error with respect to the sum of the elastic and capture cross sections at that energy? Does the more complicated interpolation law given for MT=1 really solve the problem? Congratulations! You now know how to read simple cross sections from a file in ENDF format. Just watch out for cases where resonance parameters are used to generate part of the cross section.

 15 December 2012 T-2 Nuclear Information Service ryxm@lanl.gov