Table 3 Efficiency of 137Cs extracted from air filter samples by heated concentrated nitric acid
Sampling date and time (JST) | Before ext. 137Cs (Bq) | After ext. 137Cs (Bq) | Extraction efficiency (%) |
|---|---|---|---|
March 14 21 pm–March15 9 am | 243 ± 0.7 | 72 ± 0.4 | 70.4 |
March 15 9 am–March 15 15 pm | 41 ± 0.3 | 7.4 ± 0.12 | 82.0 |
March 15 15 pm–March 15 21 pm | 20 ± 0.2 | 6.1 ± 0.11 | 69.5 |
March 15 21 pm–March 16 9 am | 19 ± 0.2 | 0.51 ± 0.04 | 97.3 |
March 16 9 am–March 17 9 am | 9.2 ± 0.19 | 0.52 ± 0.04 | 94.3 |
March 19 9 am–March 20 21 pm | 94.2 ± 0.6 | 0.20 ± 0.03 | 99.8 |
March 20 21 pm–March 21 9 am | 423 ± 0.9 | 1.2 ± 0.05 | 99.7 |
March 21 9 am–March 22 9 pm | 30.8 ± 0.24 | 0.15 ± 0.03 | 99.5 |