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KEK | HIGH ENERGY ACCELERATOR RESEARCH ORGANIZATION
April 25, 17:00, 2011
Measurement result of airborne nuclide and air radiation level in Tsukuba area: sixth report
KEK, in conjunction with National Institute for Environmental Study (NIES) have been conducting the measurement to assess the airborne nuclide and air radiation level in Tsukuba area since 15 March. In this report, the results of measurements, conducted between 1 April and 11 April, are shown in the chart below. We also performed a second path of the measurement of all samples, and a correction is made to the first sample taken on 15 March. Other measurements are consistent with the previous measurement. Please refer to the previous reports for the measurement results before 25 March.
KEK will have another measurement hereafter, and will report the result accordingly.
Measurement condition:
- Measurement point: In the premise of NIES (16-2 Onogawa, Tsukuba-City, Ibaraki)
- Air sampling instrument: High-volume air sampler, with the capability of filling 350 litters of air per minutes for 16th and 17th measurements, and 600 litters of air per minutes for 18th.
- Filter used: Collected by a quartz fiber filter and doubly stacked activated carbon filters
Filter analysis instrument: KEK’s High Resolution Ge detector
Measurement result:
The results are shown in chart 1 to 5. The overall radioactivity has been lowered to the level of 1/1000 compare to the 15 March result. We did collected greater amount of particles between 5 to 7 April, the period of 19th measurement, due to the windy weather. However, no significant increase of radioactivity was observed. Iodine-131 (half-life of 8.02 days) remains a major nuclide, but the rise in the percentage of Caesium 134 and 137 were identified.
Chart1 Result of 16th measurement: Detected nuclide and its concentration (Bq/cm3)
Measurement period:1 April, 2011 10 : 54 - 3 April, 2011 10:54
Air collected:1019 cubic meter
| Nuclide | CONC (Bq/cm3) |
| Iodine131 | 1.4×10-7 |
| Tellurium132 | 5.5×10-10 |
| Caesium134 | 1.7×10-8 |
| Caesium136 | 7.0×10-10 |
| Caesium137 | 1.6×10-8 |
| Tellurium129m | no detection |
| Iodine133 | no detection |
| Technetium99m | 1.6×10-8 |
Technetium99m is a daughter nuclide of molybdenum-99, are in the transient equilibrium.
Gamma rays from other nuclei, Lanthanum-140 are also observed.
Chart2 Result of 17th measurement: Detected nuclide and its concentration (Bq/cm3)
Measurement period: 3 April, 2011 11 : 21 - 5 April, 2011 10:59
Air collected:1026 cubic meter
| Nuclide | CONC (Bq/cm3) |
| Iodine131 | 1.8×10-7 |
| Tellurium132 | 1.3×10-9 |
| Caesium134 | 4.4×10-8 |
| Caesium136 | 1.4×10-9 |
| Caesium137 | 3.9×10-8 |
| Tellurium129m | 1.7×10-8 |
| Iodine133 | no detection |
| Technetium99m | 2.4×10-8 |
Technetium99m is a daughter nuclide of molybdenum-99, are in the transient equilibrium.
Chart3 Result of 18th measurement: Detected nuclide and its concentration (Bq/cm3)
Measurement period:5 April, 2011 11:18 - 7 April, 2011 10:24
Air collected:1691 cubic meter
| Nuclide | CONC (Bq/cm3) |
| Iodine131 | 5.0×10-8 |
| Tellurium132 | no detection |
| Caesium134 | 1.4×10-9 |
| Caesium136 | no detection |
| Caesium137 | 1.4×10-9 |
| Tellurium129m | no detection |
| Iodine133 | no detection |
| Technetium99m | no detection |
Chart4 Result of 19th measurement: Detected nuclide and its concentration (Bq/cm3)
Measurement period:7 April, 2011 10:31 - 9 April, 2011 10:31
Air collected:1728 cubic meter
| Nuclide | CONC (Bq/cm3) |
| Iodine131 | 8.4×10-8 |
| Tellurium132 | no detection |
| Caesium134 | 4.0×10-8 |
| Caesium136 | 1.1×10-9 |
| Caesium137 | 3.6×10-8 |
| Tellurium129m | no detection |
| Iodine133 | no detection |
| Technetium99m | no detection |
Gamma rays from other nuclei, Silver-110m and Lanthanum-140 are also observed.
Chart5 Result of 20th measurement: Detected nuclide and its concentration (Bq/cm3)
Measurement period:9 April, 2011 11:08 - 11 April, 2011 10:48
Air collected:1716 cubic meter
| Nuclide | CONC (Bq/cm3) |
| Iodine131 | 3.7×10-8 |
| Tellurium132 | 3.5×10-10 |
| Caesium134 | 3.1×10-8 |
| Caesium136 | 7.4×10-10 |
| Caesium137 | 2.8×10-8 |
| Tellurium129m | 1.1×10-8 |
| Iodine133 | no detection |
| Technetium99m | no detection |
Gamma rays from other nuclei, Silver-110m and Lanthanum-140 are also observed.
Chart 6 Second measurement of the sample taken on 15 March
Measurement period:15 March 2011 14:39 - 15 March 2011 17:34
Air collected:105 cubic meter
Measurement of the quartz fiber filter
of the first sampling on 15 March
at 19:04:12, 15 March, duration 606 seconds
Second Measurement of the quartz fiber filter
at 09:28:12 28 March, duration 4,000 seconds
Results of the second measurement I-131 (main component) and Te-132 are consistent with the first measurement within statistical error.
Due to miscalculation, resutls of the first measurement of 15 March sample for Cs-134,136,137 and Te-129 were underestimated by a factor of about five. Result is also corrected for I-133 by combining the measurement of the doubly stacked activated carbon filters (Apr/27: Corrected from 8.4×10-7 Bq/cm3 to 2.9x10-6 Bq/cm3).
Tc-99m is in the transient equilibrium with Mo-99 in this second measurement.
| Nuclide | CONC (Bq/cm3) |
| Iodine131 | 3.2×10-5 |
| Tellurium132 | 2.3×10-5 |
| Caesium134 | 4.0×10-6 |
| Caesium136 | 6.8×10-7 |
| Caesium137 | 3.8×10-6 |
| Tellurium129m | 3.8×10-6 |
| Iodine133 | 2.9×10-6 |
| Technetium99m | 3.5×10-7 |
Gamma rays from other nuclei, Lanthanum-140 are also observed.
Concentration of the airborne nuclide in each measurement (Bq/cm3)
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