The116Sn (n, γ)117mSn reaction commonly used in reactor-neutron activation analysis (RNAA) turned out to be seriously interfered by the117Sn (n, n′)117mSn reaction, as observed from irradiation in channels with largely different neutron thermalization. To estimate the magnitude
of this primary interference an attempt was made to determine the relevant fission neutron averaged cross-section, yielding
approximately σn, n, (117Sn)==0.09±0.01 barn. This value—believed to be the first measured and published—is remarkably high especially when compared
to the 2200 m·s−1 cross-section σo[116Sn(n, γ)117mSn]=0.006 barn.