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April 5, 17:00, 2011

Measurement result of airborne nuclide and air radiation level in Tsukuba area: fifth 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 25 March and 1 April, are shown in the chart below. 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:

  1. Measurement point: In the premise of NIES (16-2 Onogawa, Tsukuba-City, Ibaraki)
  2. Air sampling instrument: High-volume air sampler, with the capability of filling 600 litters of air per minutes.
  3. Filter used: Collected by a quartz fiber filter and doubly stacked activated carbon filters
  4. Filter analysis instrument: KEK’s High Resolution Ge detector

Measurement result:

Iodine-131 (half-life of 8.02 days) remains a major nuclide. However, the level of radiation increased during the sampling of 28 and 30 of March. The ratio of Cesium-134 and 137 also increased during this period.

The air sampling instrument was moved from the balcony of the second floor to the roof top of the NIES building on 1 April. We will report subsequent data in the next report as the sampling environment has changed.

Chart1 Result of 11th measurement: Detected nuclide and its concentration (Bq/cm3)

Measurement period:25 March, 2011 10:58 - 26 March, 2011 10:22
Air collected:844 cubic meter

graph
NuclideCONC (Bq/cm3)
Iodine1315.7×10-7
Tellurium1323.1×10-9
Caesium1349.3×10-9
Caesium136no detection
Caesium13710.0×10-9
Tellurium129mno detection
Iodine133no detection
Technetium99mno detection

Chart2 Result of 12th measurement: Detected nuclide and its concentration (Bq/cm3)

Measurement period:26 March, 2011 10:29 - 27 March, 2011 11:03
Air collected:884 cubic meter

graph
NuclideCONC (Bq/cm3)
Iodine1311.1×10-7
Tellurium1326.6×10-10
Caesium1341.6×10-9
Caesium136no detection
Caesium1371.6×10-9
Tellurium129mno detection
Iodine133no detection
Technetium99mno detection

Chart3 Result of 13th measurement: Detected nuclide and its concentration (Bq/cm3)

Measurement period:27 March, 2011 11:23 - 28 March, 2011 10:48
Air collected:850 cubic meter

graph
NuclideCONC (Bq/cm3)
Iodine1311.0×10-7
Tellurium1323.9×10-10
Caesium1346.3×10-10
Caesium136no detection
Caesium1375.2×10-10
Tellurium129mno detection
Iodine133no detection
Technetium99mno detection

Chart4 Result of 14th measurement: Detected nuclide and its concentration (Bq/cm3)

Measurement period:28 March, 2011 10:59 - 30 March, 2011 10:10
Air collected:1698 cubic meter

graph
NuclideCONC (Bq/cm3)
Iodine1315.7×10-7
Tellurium1321.7×10-8
Caesium1342.5×10-7
Caesium1361.2×10-8
Caesium1372.3×10-7
Tellurium129m5.3×10-8
Iodine133no detection
Technetium99m1.2×10-8

Technetium99m is a daughter nuclide of molybdenum-99, are in the transient equilibrium.
Gamma rays from other nuclei, Barium-140 and Lanthanum-140 are also observed.

Chart5 Result of 15th measurement: Detected nuclide and its concentration (Bq/cm3)

Measurement period:30 March, 2011 10:17 - 1 April, 2011 10:10
Air collected:1723 cubic meter

graph
NuclideCONC (Bq/cm3)
Iodine1312.2×10-7
Tellurium1326.9×10-9
Caesium1341.3×10-7
Caesium1366.1×10-9
Caesium1371.2×10-7
Tellurium129m3.3×10-8
Iodine133no detection
Technetium99m7.7×10-9

Technetium99m is a daughter nuclide of molybdenum-99, are in the transient equilibrium.
Gamma rays from other nuclei, Barium-140 and Lanthanum-140 are also observed.



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