Corrosion Behavior of Simulated HLW Glass in the Presence of Magnesium Ion

Static leach tests were conducted for simulated HLW glass in MgCl2 solution for up to 92 days to investigate the dissolution mechanism of HLW glass under coastal repository condition. Under the condition that magnesium ion exists in leachate, the dissolution rate of the glass did not decrease with time during leaching, while the rate decreased when the magnesium ion depleted in the leachate. In addition, altered layer including magnesium and silica was observed at the surface of the glass after the leach tests. The present results imply that dissolution of the glass is accompanied with formation of magnesium silicate consuming silica, a glass network former. As a consequence, the glass dissolved with an initial high dissolution rate

Changes in epidemiological characteristics and sero-prevalence against the varicella zoster virus in school-age children after the introduction of a national immunization program in Japan

A national immunization program using two doses of live attenuated varicella vaccine was introduced for children aged one to two years in Japan in October 2014. Varicella cases declined after 2014, and immunological status against varicella among vaccinated children changed in post-vaccination era. A retrospective observational study of anti-varicella antibody seroprevalence, varicella vaccination status, and history of varicella among 528 students in the first grade of elementary school was conducted. The percentage of students who received at least a single dose of varicella vaccination increased from 67% (187 of 279 students) in 2007–2008 to 91% (226 of 249 students) in 2017. Students with a history of varicella decreased from 114 of 279 (41%) in 2007–2008 to 48 of 249 (19%, P < .01) in 2017. Among them, the rate of breakthrough varicella after a single dose of vaccine in students with a history of varicella significantly increased from 38% (43 of 114 students) in 2007–2008 to 58% (28 of 48 students) in 2017 (P < .05). The antibody-positive rate significantly decreased from 50% among subjects without varicella zoster who received a single dose (95%CI: 41–58%) in 2007–2008 to 29% (95%CI: 21–38%) in 2017 (P < .01). The antibody-positive rate among students without varicella history who received two doses of vaccine was only 43% (95%CI: 32–55%) in 2017. The number of varicella infections and antibody-positive rate among students without history of varicella who received varicella vaccination decreased after the introduction of a national immunization program