Article may be useful;

Amar N. Garg, Rajiv G. Weginwar, Nitin L. Chutke

Radiochemical neutron activation analysis of Fe, Co, Zn, Sb and Se in biomedical and environmental samples. Science of The Total Environment

Volumes 139–140, 1 November 1993, Pages 421–430

http://www.sciencedirect.com/science/article/pii/0048969793900399

In this regard one may refer to our another publication; "A simultaneous  radiochemical solvent extraction method for Se(IV) and Sb(III) using N. L. Chutke, M. N. Ambulkar and A. N. Garg, Chem. Anal. (Warsaw) 38, (1993) 733-743." where again the method has been employed for the determination of Se in some biological standard reference materials.

. In case one has any difficulty or any specific question, I may be answer the same.

Hello, regarding sample preparation and Se analysis by INAA you may find the attached articles useful. If you have further questions, just contact me.

I agree with Reka Szoke! 

If you want to determine Se only, there is no need for radiochemical separation; with a little patience INAA can do the job.

Hi,

You can use coincidence method in "Determination of selenium in geological

sample by event–event coincidence technique".

good luck my friend

Thanks