“…Recently, Aoyama et al 8 have improved the ammonium phosphomolybdate (AMP) procedure for determination of 137 Cs in seawater, which includes a reduction of the amount of AMP and achievement of high sensitivity of 137 Cs determination by using high-efficiency well-type Ge-detectors. Furthermore, ultra low background γ-spectrometry using Ge detectors with high efficiency and low background materials in an underground facility (Ogoya Underground facility: OUL) can realize higher sensitive determination of 137 Cs.…”