Generation of radioactive dust by lava-like fuel-containing materials at the Shelter Object of Chernobyl NPP

During 2011–2013, the α-activity of dust that was accumulated on the sample surface of lava-like fuel-containing materials in room 304/3 of the Shelter Object of Chernobyl NPP over a period of 1–284 days was measured. The α-activity of the dust collected during the 823 days was 495.5 Bq, or 2.15 kBq m −2 per year, with the annual increment exceeding 3%. The maximal activity of the dust is in the period immediately after condensation moisture removal from the lava. The supposed source of the dust is fragmentary dispersion of lava areas with high fuel concentration. Disintegration of lava fragments continued after their detachment.