Vol.6,

Calculation of moderator analogues for 14 MeV neutrons as source were made at a IBM/PC AT computer using TAMAKER-ANISN program and 46 groups (25 neutron groups, 21 photon groups) UW cross section data. The intensifying effect of lead and natural uranium for moderating 14 MeV neutrons is confirmed. Adopting proper structure of the moderator, the intensifying factor M (times) may be larger than 3. Using lead and natural uranium in sub-critical assemblies (or call boosters), with 14 MeV neutrons as source, with the same dimension as that of above, the intensifying effect is also confirmed. With a proper structure of sub-critical assembly, the intensifying factor M may be close to or even larger than (1-k)^-1 where k is the effective multiplication factor.

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Samarium-153-EDTMP (ethylene diamine tetramethylene phosphonate), for its promising biological properties, has been proved as a palliating therapeutic agent for bone tumor in human beings. ¹⁵³Sm with high radionuclear purity and specific activity of 5.18 GBq (140 mCi)/mg Sm₂O₃ was prepared by irradiating natural Sm₂O₃(¹⁵²Sm, 26.7%) sample, replacing costly enriched samarium oxide target, at a flux of 4x10¹³n·cm^-2·s^-1 for 110h. The yield of ¹⁵³Sm complexing with EDTMP is greater than 98%at pH 8〜10 in boiling water bath for 30 min, and not significantly decreases within one week after ¹⁵³Sm-EDTMP complex formation.

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D2+ions of 70 and 90 keV were separately implanted into two thick samples of sintered alumina ceramic and the distribution of deuterium has been measured for three runs at an interval of 5 months using high energy proton backscattering and elastic recoil detection (ERD). The measured data show that there is little diffusion of deuterium in Al₂O₃ and the diffusion coefficient is deduced to be 1.1×10^-17cm²/s. The measured total concentration of implanted deuterium is 4.5×10¹⁸ at./cm². The profile of hydrogen adsorbed on the surface of A1₂O₃ samples was also observed by ERD and ¹H(¹⁹F, αγ)¹⁶O analysis. The distribution range of ¹H in Al₂O₃ after deuterium implantation is much larger than that before one.

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It is capable of giving the initial intakes of radionuclides and the assessment quantities used in radiation protection according to its measured results of radionuclides in vivo. It is accomplished by providing the software of controlling, interface and internal dose estimation programs to the original iron cabin shielding whole-body counter. The preliminary application shows that its data processing is rapid and correct, and can meet the requirement of rapid internal radioactive contamination monitoring and diagnosing in case of lots of internal contamination subjects happened in nuclear accident.

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The energy spectra of reflected electrons from the substrates of targets have been calculated by the bipartition model of electron transport, the contributions of the inner shell ionization events produced by the reflected electrons from the substrates in the targets to the x-ray counting in a Si(Li) detector have been estimated. It has been confirmed that, by such correction to the measured data, the experimental results of inner shell ionization cross sections by electron impact with fine precision may be obtained under the condition of thick substrate.

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Most of the natural occurring radionuclides in both noodles and bread are found to have specific activities below the detectable limit of the high purity germanium (ntype) spectrometer system of the EG&G Ortec Company. For dried bread, ⁴⁰K, ¹³⁷Cs and ⁶⁰Co are found to be 44.45〜84.52, <0.012 〜0.052, <0.018 〜0.054 Bq/kg; for noodles, to be 29.55〜64.54, <0.01〜0.069 and<9.8×10^-3 〜 0.074 Bq/kg, respectively. The weighted committed dose equivalents due to the ingestion of ¹³⁷Cs from noodles and bread for a male and female adults have been estimated to be 0.5 and 0.6 µSv, respectively, being less than the values recommended by ICRP.

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The measurement principle and analysis method of natural gamma-ray spectra using NaI(Tl) scintillation spectrometer are briefly described first, then block diagrams of the HD-8004 NaI(Tl) gamma-ray spectrometer. Finally, sample measurements are listed and discussed. The results are quite promising. Based on the analysis of these measurements, measures to improve the accuracy of spectrum measurement are proposed. It is well hoped that these measures can contribute to the development and application of gamma-ray spectrum measurement.

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MoS_x (x=1.79〜2.34) films of 200 nm thickness are deposited onto brass and C20 steel substrates by the ion beam assisted technique, respectively. Structures and compositions of these films, and changes in valence states of the Mo element are examined by XRD and XPS before and after wear. The lubrication properties and wear resistances for two kinds of samples are evaluated using a pin-on-disk installation in atmosphere at the room temperature. Tribo-wear behaviours and the microstructures between two kinds of samples exhibit obvious differences.

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This paper points out the limitation of Beck formula and gives a revised formula owing to the water content and ²²² Rn escape in soil for calculating γ radiation dose rate through the experimental fitting from 576 sets of measured values in Zhejiang Province. When the revised formula is applied to Beijing Municipality, where there is a great difference in the meteorology and soil conditions, the calculated average in general is only 3.5% different from that measured; those of every position deviate only 2.1% averagely; and their dispersion is in the experimental errors. Therefore, the revised formula possesses a high reliability and a broad suitability, and is an effective method to estimate the γ radiation dose rate on the land.

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