Kenshi Numakura

Formation of Organic Iodides upon Heating Nitric Acid Solutions Containing Carrier-Free Iodine-131

When nitric acid solution containing carrier-free 131I was heated, a fraction of the 131I was converted to organic iodides, among which methyl iodide was a major component. The yield of organic iodides showed a strong dependence on the concentration of nitric acid. Furthermore, the yield curve referred to reaction time revealed the particular characteristic of a hump appearing in the case of diluted nitric acid solutions. The distribution of 131I among the various oxidation states in the acid solution has also been studied in its relation to reaction time. The results obtained indicate that organic iodide formation is related with the I°-IO3- oxidation step. The yield curve of the organic iodides is discussed qualitatively, by assuming an intermediate state I* existing between two extreme states of oxidation.

An Additional Formation of CH 2 80 BrBr via a Kinetic-energy-independent Process in the Highly Moderated 80 m Br-CH 4 Systems

The moderator effect of Kr on the reaction of (I.T.)-activated 80Br with CH4 has been examined, keeping the ratio of Br2/CH4 at 0.02 or 0.05. The yield of CH280BrBr shows a slight decrease at the beginning of moderation and then tends to increase with further moderation. These facts suggest an additional formation of CH2-80BrBr via a thermal ionic process in highly-moderated systems. When the concentration of Br2 is varied in the system containing 10 cmHg of CH4 and from 40 to 36 cmHg of Kr, the yield of CH280BrBr first increases and then decreases, showing a broad maximum. This dependence not only partly explains the inconsistence of the present results with those previously reported, but also suggests the competition of two types of reaction in its formation. One must be the reaction of a radioactive radical with Br2, leading to the formation of CH280BrBr:·CH280Br+Br2→CH280BrBr.The other type of reaction is a scavenging reaction of Br2 for the reacting 80Br atom.

The Reactions of 80 Br Activated by the ( n ,γ) Process with Methane

The reactions of 80Br activated by the (n,γ) process with CH4 have been examined. By assuming that the limiting yields of products at 1.0 m.f. of the Kr-moderator is due to thermal ionic processes, the kinetic yields were tentatively determined to be the 12.4% for total organic, 11.4% for CH380Br, and 1.0% for CH280BrBr. A similar treatment of the results from the reactions with CD4 gives 5.1% for total organic, 3.9% for CD380Br, and 1.2% for CD280BrBr. When the CH380Br yield was compared with that from the reactions of 80Br from the (I.T.) activation, a noticeable difference was noticed; it was roughly 3 times as large as in the latter system. Furthermore, the pressure effects on the CH380Br show that a fraction of CH380Br is highly excited and is able to decompose even at a pressure of 1920 mmHg. This suggests that the distribution of 80Br in the reaction energy range extends to a higher energy than in the case of 80Br activated by the (I.T.) process.