Measurement of Reaction Rates in Be/PE/Fe Combined Spheres

Reaction rates of 27Al(n,α)24Na, 197Au(n,2n) 196Au and 197Au(n,γ) 198Au reactions in Be/PE/Fe combined spheres bombarded by central DT neutrons were measured by activation foil method with a HPGe detector. The simulating calculation was carried out using MCNP/4B code and ENDF/B-Ⅵ database for the above reactions. It is seen that the calculated reaction rate with that from experiment fits well for 27Al(n,α)24Na and 197Au(n,2n) 196Au reactions, and is far from agreement for 197Au(n,γ) 198Au reaction. A possible explanation for the disagreement is the self shielding effect of the activation Au foils for the low energy neutrons.