The gamma spectra of fission products mixture calculated in the previous report were combined with the crystal data and the gamma-ray scintillation spectra for a well type NaI (Tl) scintillation crystal were computed. Similar calculations were performed to obtain the spectra of
239Np, a daughter of an activation products of
238U with the thermal neutron,
239U.
Results are given graphically as the figures which predict recording spectra for gamma-ray spectrometer as functions of time after fission. They are composed of five peaks in the lower energy range and four peaks in the higher one, progress of which depends fairly strongly upon decay time. The progress is as follows;
(1) During first 3 weeks after fission, peak IV and VII have decayed below detection.
(2) Peak X, which exists under the background at the first day after fission, appears on about 3 days after fission and reaches the maximum height at 2 weeks after fission.
(3) After a 50200 days decay period, Peak V, X and VI have decayed in succession below detection.
(4) About 18 months after fission, Peak VII reappears.
(5) About 2 years after fission, Peak VIII have disappeared into the baseline and the spectrum possesses only four peaks I, II, III and VII.
(6) About 7 years after fission, peaks I, II and III have decayed and only peak VII retains.
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