Development of nondestructive detection method for long-life β nuclides using bremsstrahlung photons

Radioactive wastes from nuclear fuel cycle facilities generally contain a huge amount of long-life non-γ emitting nuclides such as C-14 and I-129. We have been making a feasibility study on a nondestructive detection method utilizing bremsstrahlung photons obtained from industrial electron beam accelerators. Irradiation experiments were performed for I-129 sample and Au foils by using 30 MeV electron LINAC. Generated nuclides of I-128 from I-129 (γ,n) reaction and Au-196 from Au-197 (γ,n) reaction were measured with a Ge detector. The experiments were analyzed with two calculational methods; a simplified theoretical method and Monte Carlo method using MCNP code. Both calculations reproduced the tendency of the measured data quite well, and especially the MCNP calculations predicted (γ,n) reaction rate within typical deviation of 20%. In addition, an adequate level of photoreaction was found to easily obtained because of the narrow and dense beam of the bremsstrahlung photons. As a result, it became clear that the technology utilizing electron LINACs is sufficiently applicable to the nondestructive method for long life 'difficult to measure' radioactive nuclides. (author)