[en] Purpose: To enable effective removal of contaminating tritium while suppressing the dissolution at the surface of stainless steels. Constitution: Upon decontaminating the surface of tritium contaminated stainless steels, tritium at the outermost surface layer of the stainless steels is removed by the surface dissolution using diluted hydrochloric acid. Then, tritium intruded to the grain boundary in the surface layer of stainless steels is removed by dipping into an aqueous sulfuric acid - copper sulfate solution. (Horiuchi, T.)

[en] In this review, synthetic methods of uranium and neptunium compounds mainly from solutions and their natures are summarized. For uranium, 3 compounds of trivalent, 4 compounds of tetravalent and 23 compounds of hexavalent are described in slight details. For neptunium, synthesis methods of stock solutions for pentavalent and hexavalent neptunium, 4 items (6 compounds) of trivalent, 8 items (19 compounds) of tetravalent, 28 items (29 compounds) of pentavalent, 10 items (14 compounds) of hexavalent and 5 items (9 compounds) of heptavalent are described in slight details. Furthermore, on compounds which can not be described in details, the names are listed with literatures. The materials used here have been collected during the research activities on Moessbauer spectroscopic studies of uranium and neptunium compounds, then, the reviews on Moessbauer spectroscopic studies of actinoid compounds are also listed. (author)

[en] Professor Krot (Head of the Laboratory of Transuranium Elements Chemistry, Institute of Physical Chemistry, Russian Academy of Sciences) stayed at Tokai Research Establishment, Japan Atomic Energy Research Institute for 45 days from January 16, 1997 to February 28, 1997 by an invitation of the Research group for Moessbauer Spectroscopy of Actinoids, Advanced Science Research Center. In the mean-time, Professor Krot left many memoranda on actinide research for the Research group. This is a compilation of those memoranda in Japanese translation. The contents include many topics, synthesis of neptunium compounds in valence states of 3, 6 and 7'', method for recovery and reuse of neptunium from compounds in a laboratory'', ''records of the neptunium compounds synthesized during his stay'', and so on. Also, important contents of discussions with Professor Krot in the Research Group are summarized. (author)

[en] In this review, experimental results on studies of radioactive iodine, tritium and neptunium are summarized from various experimental results which the author studied in JAERI. On studies of radioactive iodine, firstly, in experiments which was simulated the reprocess of spent nuclear fuels, the following results were described such as the composition of radioactive organic iodides, the relationship between the yield of organic iodides and reaction temperatures or variation of acids, the relationship between the yield of organic iodides and chemical forms of iodine, the source of carbon for organic iodides. Then, from these experimental results, the process establishing the formation mechanism of organic iodides was fully described. On the basis of the formation mechanism, followings were also discussed on possibilities for the formation of organic iodides under nuclear reactor accidents, and the upper limit of the amount of organic iodides under the atmosphere of HTTR. On studies of tritium, three topics were concisely described on the isotopic composition of tritium gases which were commercially available, the chemical forms of tritium in various materials and the diffusivity of tritium in them, the sorption and desorption behaviors of tritium on surfaces of various materials. On the experimental results of neptunium chemistry, firstly, the relationship between the structure of neptunium compound and the ²³⁷Np Moessbauer isomer shift was discussed. For neptunium(V) compounds, a good correlation was found between the isomer shifts and the mean bond length of Np-all oxygen coordinated, however for neptunium(VI) compounds, better correlation was found between the isomer shifts and the bond length of Np-O in the neptunyl(VI) groups. Furthermore, the experimental results were described on neptunyl(VI) hydroxides in which some of them were new compounds. (author)

[en] A reverse-phase chromatographic isolation procedure for Nb from Mo and Tc is given. The separation is performed with TBP (tri-n-butyl phosphate) on celite column. Molybdenum oxide was irradiated with 20MeV bremsstrahlung, which produces a mixture of ^93mMo, ⁹⁹Mo; ^99mTc; ^91mNb, ^95mNb, ⁹⁵Nb and ⁹⁶Nb. The irradiation was applied to a 6 N HCl solution of the target. Separation was repeated twice, which resulted in isolation of the radioniobium with a decontamination factor of 10⁴ both for Mo and for Tc. Decay analysis of the activity showed that radioniobium thus separated was composed of ^91mNb, ^95mNb, ⁹⁵Nb and ⁹⁶Nb. The γ-spectrum of ⁹⁶Nb was obtained by subtraction of the spectrum taken 119 hr after the end of irradiation from that of 74 hr. (author)

[en] On the neptunium science, ²³⁷Np Moessbauer spectroscopy a general feature of neptunium compounds with various valences are outlined. Then, correlations between isomer shifts and crystal structures of neptunyl (V, VI) compounds were discussed. (author)

No abstract available

[en] This issue is the collection of the papers presented at the CSNI (Committee on the Safety of Nuclear Installations) workshop on iodine chemistry in reactor safety. The 31 of the presented papers are indexed individually. (J.P.N.)

No abstract available

[en] Moessbauer effects are observable in seven elements of actinides from ²³²Th to ²⁴⁷Cm and Moesbauer spectra have been investigated mainly with ²³⁷Np and ²³⁸U for the reasons of availability and cost of materials. This report describes the fundamental characteristics of Moessbauer spectra of ²³⁷Np and the correlation between the isomer shift and the coordination number of Np(V) compounds. The isomer shifts of Np(V) compounds had a tendency to increase as an increase of coordination number and the isomer shifts of Np(V) compounds showed broad distribution as well as those of Np(VI) but δ values of the compounds with the same coordination number were distributed in a narrow range. The δ values of Np(VI) complexes with O_x donor set suggest that the Np atom in its hydroxide (NpO₂(OH)·4H₂O)might have pentagonal bipyramidal structure and at least, pentagonal and hexagonal bipyramidal structures might coexist in its acetate and benzoate. Really, such coexistence has been demonstrated in its nitrate, (NpO₂)₂(NO₃)₂·5H₂O. (M.N.)