To determine the individual radon daughters concentration, usually, the method of time sequential variation of alpha activities of radon daughters collected on the surface of filter has been adopted. The proposed instrumentation, to provide for the saving of counting time with the accurate determination of 214Pb concentration, the silicon surface barrier type semiconductor detector (thickness of depletion layer is 300μm) and the method of counting during the collecting time have been employed. The above-mentioned detector can not only detect the alpha and beta particles but also separate by energy of the alpha or beta particles of each nuclide. To prevent the disturbance of background amma radiation to the beta counting channel, sufficient investigation has been developed for suitable etermination of region of registered channel (so-called region of interest) corresponded to the beta nergy. The detectable limits of the proposed instrumentation are estimated as 0.5, 2.4, and 0.8[Bq/m3] for 218Po, 214Pb, and 214Bi, respectively, with the sampling time of 1600[s], the flow rate of 2.5×10-4[m3/s] and the counts of the gamma-background of 300 [counts/1800s].
Applicability of reverse osmosis to the treatment of radioactive liquid waste was investigated. In previous papers, we showed the ability of reverse osmosis for decontaminating liquid waste which contains ionic radionuclides with chloride ion. When sulfate ion coexists with chloride, logarithms of DFs of one cation are approximately expressed by a linear function of logarithms of SO42-/Cl- ratio. In this paper, we investigate the relation between DFs and concentrations of coexisting ions in multicomponent cation/anion system. As a result of this study, DFs of rations change more seriously with coexisting anions composition than with cations. In the case of anion, these influences are the reverse. Logarithms of DFs of cations and anions are expressed by linear equation with the two variables, logarithmic concentration ratio of univalent/divalent cations and logarithmic concentration ratio of SO42-/Cl-.
Measurements of 222Rn in outdoor air and indoor air have been carried out every 2 months during about one year from Nov. 1988 using passive electrostatic integrating 222Rn monitor developed by Iida et al. The annual mean outdoor 222Rn concentrations at Beijing, Xi'an, Nanjing, Shanghai, Fuzhou and Guiyang were 8.0, 11.2, 6.4, 4.8, 9.5 and 12.2Bq·m-3, respectively. The high outdoor 222Rn levels at Beijing and Xi'an, situated in inland area, may be attributed to high frequency of the occurrence of inversions in winter. The low 222Rn levels at Nanjing and Shanghai and the high 222Rn levels at Fuzhou and Guiyang correspond to their geological conditions and the 226Ra concentrations in soil. The annual mean indoor 222Rn concentrations were about 2-3 fold of outdoor concentrations at every city. The average indoor 222Rn concentration in China was 29.2Bq·m-3. The annual effective dose equivalent resulting from outdoor and indoor 222Rn concentrations amounts to about 0.72mSv·y-1.
An experimental investigation was carried out on the improvement of a preparation system of tritium-free water, which is used as “back-ground water” in the determination of tritium with the liquid scintillation method, for environmental monitoring. The fundamental consideration was based on the recombination of hydrogen gas reduced tritium content and oxygen gas in laboratory conditions. An assembly for this system was made up of two units, an electrolytic degradation unit for the generation of H2 gas, and a circulation unit of N2 as carrier gas connected with a catalyst column and a cold trap for recombination to H2O. This apparatus was entirely made of glass, and designed as closed system. As operating conditions, the electric current, a circulation rate of N2 gas and a catalyst column temperature were 12A, 2.4l/min and 150°C, respectively. This system has proven to be suitable for preparation of tritium-free water, under the safe and sure condition. Three days are necessary to obtain 40ml of water.
The present situation of personnel neutron monitoring is summarized in the facilities where the neutron exposure really happens, such as reactor, accelerator and nuclear fuel handling facilities, and the actual calibration method using a phantom is described for personnel neutron dosimeters (film badge, albedo TLD, solid state track detector) of practical use in these facilities. The calibration method of neutron dosimeters is not standardized at present, and it is usually carried out using 252Cf and 241Am-Be neutron sources. Neither the energy spectra of these neutron sources are similar to those of actual neutron fields in the facilities nor are the energy responses of these neutron dosimeters coincident with the fluence-to-dose equivalent conversion factor defined by ICRP; it is thus difficult to evaluate the neutron dose equivalent from the measured data. Here, we refer to some typical neutron spectral fields and propose to use the moderating radioactive neutron source field, which has a similar spectrum to that of the actual field, for calibration of personnel neutron dosimeter.
Following the accident at Unit 4 of Chernobyl nuclear power plant, extensive activities have been conducted to mitigate radiological consequences, on the public, associated with radioactive materials released during the accident. Among numerous decisions on protective measures, the decisions on long-term protective measures, in particular relocation, have been subjected to concerns and anxieties of the public, leading to social and political arguments in the three republics which were, are and will continuously be affected by the accident. Corresponding to this difficulty, the Union of Soviet Socialist Republics requested the International Atomic Energy Agency to perform an international assessment of criteria established by the USSR authorities and an evaluation of protective measures on the public. This paper summarises the results of international assessment undertaken by the International Chernobyl Project under the direction of the International Advisory Committee, and includes such items as environmental contamination, exposure to the public, health effect and protective measures.