Temperature dependence of spurious pulses in use of plastic scintillation detectors

Standardization of 99mTc and 99Mo by the use of a 4pibeta-4pigamma counter

Technetium-99m is widely used for many diagnostic investigations in nuclear medicine, thus the standardization of this nuclide is important. In classical 4pibeta-gamma coincidence counting of (99m)Tc, the steep slope of the efficiency function and the large extrapolation range may cause a large measurement uncertainty. In order to overcome these difficulties, we apply the 4pibeta+4pigamma sum counting technique for the standardization. Furthermore, we adopt both the 4pibeta-4pigamma coincidence counting method and the 4pibeta+4pigamma sum counting technique for the standardization of its parent nuclide (99)Mo. High efficiencies for both nuclides were easily achieved by the use of our 4pibeta-4pigamma counter. All the results were consistent with the reference value obtained by the conventional method obtained by NMIJ.

Standardization of 152Eu and 154Eu by 4πβ−4πγ coincidence method and 4π(β+γ) integral counting

The 4pibeta-4pigamma coincidence counting and 4pi(beta+gamma) integral counting techniques were applied for the standardization of 152Eu and 154Eu. In these techniques, the beta-detector is composed of two thin plastic scintillators sandwiching the source coupled with a slender photomultiplier tube. This beta-detector was inserted into a large well-type NaI(Tl) scintillation detector for gamma-ray detection, making a 4pibeta-4pigamma detector configuration. The results obtained by the above two techniques were in good agreement and consistent with the results of international comparisons.

Absolute radioactivity measurements by the use of a 4πβ–4πγ detector configuration

The radioactivity of 60Co and 134Cs sources were measured using a 4pibeta-4pigamma detector configuration with a well-type NaI(Tl) crystal and a sandwich type 4pibeta detector composed of two sheets of NE102A plastic scintillator coupled to a slender photomultiplier tube. The beta-detector was inserted into the well of the gamma-detector. Since counting efficiencies in both the beta- and gamma-channels can be kept high, excellent counting statistics were attainable even when weak sources were measured. This configuration can also be used for radioactivity measurements based upon the direct integral counting of 4pibeta + 4pigamma logic sum signals, and two independent results can be obtained for every measurement. This technique is especially useful for the standardization of complex decaying nuclides.