How Can U-238 Cross Section Be Accurately Modeled in the Resonance Region?

[Nucengable]

Hello , I was trying to calculate the effective absorption cross section ( group constant) of U-238 in the resonance region between neutron energies (1 ev - 10 kev) but as you can see from the picture U-238 has a lot of resonance at this region, I was wondering if there is a way I can obtain U-238 cross section as function of energy in this region, I was trying to fit the tabulated data of the energy vs cross section (barn) using MS EXCEL but it was incapable to give me an accurate fit. any help would great...

[url=http://www.0zz0.com][PLAIN]http://www3.0zz0.com/2012/05/04/19/327609909.png[/url][/PLAIN]


Thanks.

 

[wizwom]

Resonance escape probabilities for typical light water reactors are 0.90 or so;
http://t2.lanl.gov/data/n7-pdf/u/238.pdf shows how complex this region is for U238, and It seems a detailed paper was done by E Hellstrand in 1957
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5121844&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5121844