Table 4. Nuclide 55 Fe 63. Ni 90 SY 151 238 Nuclides measured in wet-chemistry analyses. Half-life Principal radiation Type of detection . , Gamma counting: Nal(Ti), Ge(Li) detectors. (2.7 y 5,95-keV x ray 92 ¥ B particle (E = 65.9 keV) max Liquid scintillation counter. . 90 § particle of Y daughter (E = 2,27 MeV) max . . Beta counting: gas-filled proportional counter. . B particle (£ = 76 keV) max . eer . Liquid scintillation counter. 28.5 y sm B87 y Pu 87.8 y , 5.50~MeV a Ce a ea ge . ; Alpha-pulse-height analysis (Frisch-grid chamber, solid state). 239 240 241 241 Pu 24,400 y 5.16-MeV a Mass spectrometry, alphapulse-height analysis. Pu 6,540 y 5.17-MeV o Mass spectrometry, alpha pulse height analysis. §8 particle (E = 21 kev) max Mass spectrometry. Pu Am Fe, Ca, Sr 14.0 y 433 y Stable 5.49-MeV a . . Alpha-pulse-height analysis. None (Atomic absorption).