There are highly toxic radio-isotopes and high heat emitting isotopes in spent nuclear fuels which could be a burden in a deep geological repository. Some preliminary study in order to see if there are some advantages in terms of waste burden, in case that the spent fuel is appropriately processed and then disposed of in a final repository, has been carried out at KAERI. This study is focused on the proliferation resistance for various processing alternatives for them. The evaluation criteria and their indicators for proliferation resistance analysis are selected and then evaluated quantitatively or quantitatively for the alternatives. The processing alternatives are grouped into three categories according to the level of decrease of burden for final disposal and named them as Level I, Level II and Level III technolgy alternatives. Level I alternative is to maximize the long-term safety in the final repository from the removal of I- 129, semi-volatile radioisotope, which is the greatest impact on the long-term safety of the repository. Level II alternative is to remove the strontium-90, high heat emitter, in addition to the removal in Level I. The Level III is to additionally remove uranium from main stream of the level II to reduce the volume of the high level wastes to be disposed. The intrinsic radiation and chemical barriers against the nuclear proliferation are selected and analyised for the alternatives. It is resulted from the proliferation resistance analysis that all three options showed excellent resistance to nuclear proliferation for the two barriers. However, Level III technology including electrochemical refining process is relatively a little weaker than others. Overall, it could be an effective means to reduce the burden of disposal if the spent fuels are appropriately conditioned for final disposal. Further detailed studies are, however, needed to finalize its feasibility.

This study was conducted with two ruminally cannulated Holstein steers to examine the effect of micronized and steam flaked corn on ruminal fermentation characteristics. The in situ dry matter degradability after 48 h incubation was the highest (P<0.05) at micronized corn (2.5 mm thickness) compared with steam flaked corn treatments. The steam flacked corn (3.3 mm thickness) was degraded lower (P<0.05) than the 2.9 and 3.1 mm thickness of steam flacked corn. Effective dry matter degradability and the rate of constant were the highest (P<0.05) at micronized corn (2.5 mm thickness) compared with steam flaked corns as well. The in vitro dry matter degradability after 48 h incubation was tended to higher (P=0.088) at micronized corn (2.5 mm thickness) than steam flaked corns, whereas there is no significantly difference between steam flaked corn treatments. Total volatile fatty acid concentration was higher at steam flaked corn (2.9 mm thickness) than micronized corn (2.5 mm thickness) and steam flaked corn (3.1 and 3.3 mm thickness). The acetate : propionate ratio was the highest (P=0.008) at steam flaked corn (2.9 mm thickness) and the lowest (P=0.008) at micronized corn (2.5 mm thickness). Total gas and methane production after 48h ruminal incubation was the highest (P=0.001) at micronized corn (2.5 mm thickness) compared with steam flaked corns. According to these results, the thickness of steam flaked corn as resulted corn processing is believed to do not affect methane production. However, further study is needed to better understand the present results to verify the correlation between corn processing method and their thickness on methane production using the same thickness corns by difference processing methods.