The epithermal neutron activation analysis of uranium was studied to deter mining trace uranium via 239 U(T 1/2 =23 5min) produced by the 238 U(n
γ) reaction with boron nitride (BN) as shielding material to reduce the interference from major elements Al
Cl and Na The detection limits of uranium are 8ng/g for biological materials and 0 15μg/g for geological samples
respectively An analytical time of less than one hour per sample is possible The contents of uranium in 15 biological and geological standard reference materials were determined