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In this study, standardization of 14 C is carried out using the CIEMAT/NIST method with a conventional liquid scintillation counter, which is the national standard, and a triple-to-double coincidence ratio (TDCR) counter developed by the National Institute of Advanced Industrial Science and Technology (AIST). An efficiency calculation for the CIEMAT/NIST method was conducted by the program CN2004. The TDCR calculation was conducted at AIST using a custom-made program. The activity measured by the TDCR counter was in good agreement with that measured by the conventional national standard within the given uncertainties.These two measurement methods will be used for calibration services at AIST according to the purpose.

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Sealed radioactive sources of 22Na for positron annihilation lifetime spectroscopy (PALS), free from the legal regulations, are commercially available from an American company. However, thick foils are used to seal 22Na in these sources and large fractions of the positrons annihilate in the sealing materials. Further, it is pointed out that a long lifetime component over 1 ns appears in the positron lifetime spectrum acquired with the Kapton sealed source (POSK-22, IPL Inc.). In this research, attempts were made to develop high quality sealed positron sources, potentially free from regulations, for ubiquitous application of PALS. The sources prepared in the present work are of high quality and applicable to our new PALS, which does not require sample cutting and is potentially applicable to truly nondestructive, onsite inspection of various materials