No abstract

Carbon steel is one of the candidate overpack materials for geological disposal of high-level radioactive waste in Japan. Corrosion of carbon steel is classified into two types: general corrosion and localised corrosion. In this study, propagation of general and localised corrosion (pitting corrosion and crevice corrosion) were investigated by immersion tests of carbon steel under the aerobic conditions. The results of the immersion tests showed that the corrosion growth rate was strongly dependent on the environmental conditions and type of steel. However, the upper limit of the pitting factor, the ratio between the maximum corrosion depth and the average corrosion depth, was determined approximately using only average corrosion depth. Based on the experimental and literature data, an empirical model that predicts the maximum corrosion depth of an overpack from average corrosion depth was developed by applying the extreme value statistical analysis using the Gumbel distribution function.

The corrosion behaviour of a carbon steel weld joint under anaerobic conditions was investigated to estimate the long term integrity of the carbon steel overpack. The welded specimens in this study were prepared using three different welding methods: gas tungsten arc welding, gas metal arc welding and electron beam welding. General corrosion was observed for each immersion specimen, and the corrosion rate at the weld joint was the same as or less than that of the base metal. The concentration of hydrogen that absorbed during immersion testing was ,2?48610 25 mol kg[Fe] 21 (0?05 ppm) after 3 years, a value regarded as having little influence on hydrogen embrittlement. The susceptibility to hydrogen embrittlement was the highest in the base metal, suggesting that there was little adverse effect on the weld joint from welding. The welded carbon steel overpack is assumed to maintain its resistance to corrosion as a disposal container for the expected lifetime under anaerobic underground conditions.

Thirteen pre-school and ten undergraduate pairs participated as eyewitnesses to a simulated criminal event presented through animated cartoons using a presentation trick (MORI technique). Although there were two different versions, the MORI technique had participants observe only one version without being aware of the other. In three reporting sessions, participants recalled what they presumed they had jointly observed; individually immediately after the presentation, collaboratively after the individual recall, and again individually one week later. The main results were: pre-schoolers, as well as undergraduates, showed better recall in the collaborative tests, though the former generally showed poorer recall than the latter, pre-schoolers tended to conform more frequently than undergraduates in the week-later tests, and both pre-school and undergraduate pairs conformed more often for amendment than distortion.

The ground-state bands of 248,250,252 Cf have been established up to the 10 + , 12 + , and 10 + states, respectively, by in-beam γ -ray spectroscopy using neutron-transfer reactions with a 153-MeV 18 O beam and a highly radioactive Cf target. The deexcitation γ rays in 248,250,252 Cf were identified by taking coincidences with outgoing particles of [16][17][18][19] O measured with Si E-E detectors, and by selecting their kinetic energies. Moments of inertia of 248,250,252 Cf were discussed in terms of the N = 152 deformed shell gap.