Volatilization of B4C control rods in Fukushima Daiichi nuclear reactors during meltdown: B–Li isotopic signatures in cesium-rich microparticles
Journal
Journal of Hazardous Materials
Journal Volume
428
Start Page
128214
ISSN
0304-3894
Date Issued
2022-04
Author(s)
Fueda, Kazuki
Takami, Ryu
Minomo, Kenta
Morooka, Kazuya
Horie, Kenji
Takehara, Mami
Yamasaki, Shinya
Saito, Takumi
Shiotsu, Hiroyuki
Ohnuki, Toshihiko
Law, Gareth T.W.
Grambow, Bernd
Ewing, Rodney C.
Abstract
Boron carbide control rods remain in the fuel debris of the damaged reactors in the Fukushima Daiichi Nuclear Power Plant, potentially preventing re-criticality; however, the state and stability of the control rods remain unknown. Sensitive high-resolution ion microprobe analyses have revealed B–Li isotopic signatures in radioactive Cs-rich microparticles (CsMPs) that formed by volatilization and condensation of Si-oxides during the meltdowns. The CsMPs contain 1518–6733 mg kg–1 of 10+11B and 11.99–1213 mg kg–1 of 7Li. The 11B/10B (4.15–4.21) and 7Li/6Li (213−406) isotopic ratios are greater than natural abundances (~4.05 and ~12.5, respectively), indicating that 10B(n,α)7Li reactions occurred in B4C prior to the meltdowns. The total amount of B released with CsMPs was estimated to be 0.024–62 g, suggesting that essentially all B remains in reactor Units 2 and/or 3 and is enough to prevent re-criticality; however, the heterogeneous distribution of B needs to be considered during decommissioning.
Subjects
Boron-lithium isotopes
Cesium-rich microparticle
Fukushima Daiichi Nuclear Power Plant
Re-criticality
Secondary ion mass spectrometry
Publisher
Elsevier BV
Type
journal article