1983年 · 第03卷第01期

In this paper the mechnisms of radiation action, particularly at the low doses of interest for radiation protection, are reviewed. Main generalities concerning the information available on the effects of radiation in man and mammalian species, both non-stochastic effects (including effects in utero) and stochastic effects (tumor induction and genetic effects) are given. And, the risk estimates which are the scientific points of departure for the ICRP system of dose limitation are presented. In addition, current problems and possible future trends in these fields are also discussed. (Q. X. Zhang)

Radiation protection in medicine deals with the protection of patients and that of personnel. This paper presents a detailed discussion on the use of justification, optimization of protection, and dose limits in this field, in order to minimize the radiation exposure to patients, especially to children and women of reproductive capacity. The protection of personnel in a radiology department has also been discussed. (X. A. Chen)

This paper has reviewed and analysed the investigation results on the five components of hemopoietic microenvironment. It was determined that every component of hemopoietic microenvironment could promote the recovery of hemopoietic function from radiation injury. It was found and confirmed preliminarily that fibroblastoid precursor cells of hemopoietic stroma played chief role in the hemopoietic microenvironment behavior. These results would not only provide a new approch to prevent and to treat the ultrasevere acute radiation sickness, but also be advantageous to the study of the pathogenesis of the diseases of hemopoietic system.

Chromosome aberrations in A-bomb survivors were analyzed by means of a G-banding method and the results were compared with that of the conventional staining method in order to verify whether the banding technique could improve the detection of stable aberrations. The present results showed that significantly high frequency of aberrant cells was found by G-banding technique as compared with that by conventional staining method. This may be due to the fact that some types of symmetric exchanges can only be detected by the banding technique.

The renal damage of rats poisoned with different doses of uranyl nitrate was found primarily in the second segment of the proximal convoluted tubules. Experiments with long term repeated injections of small doses of uranyl nitrate into rats and rabbits showed that the induced renal damage was not more severe than that caused by single injections of the same dose. With the elapse of time, even though the injections were continued, the renal damage gradually became slighter or failed to appear. Owing to the fact that chronic renal damage can only be caused by dose level which would almost induce an acute damage, the occurrence of chronic renal damage in occupational workers exposed to uranium at normal levels is very improbable. A series of animal experiments were conducted with various kinds of animals, different uranium compounds, different routes and schedules of administration. The results showed that the hepatic damage, if any, was always slighter than the renal damage. When the tetravalent uranium compounds were injected into the portal vein system and were made to flow directly into the liver, the renal necrosis still predominated over hepatic injury.

This paper reports the reformation of nine diagnostic X-ray apparatus for bettering radiological protection. After reformation, the results of evaluation conformed with the criteria laid down by the Rules of Radiological Protection in Medical X-Ray Diagnosis. The improved parts were simple in structure, easy to fabricate and convenient for operation. They provided definite protection for medical diagnostic X-ray workers.

An improved procedure is described for the determination of plutonium-239 in urine and air samples. It mainly consisted of wet ash, rapid co-precipitation of plutonium with bismuth phosphate. anion exchange separation and purification, and electro-deposition. The advantages of modified procedure are: the time of operation is much shorter, taking about 8 hr for the urine samples, 6 hr for air and aerosol samples. The plutonium-239 average recovery is as high as (80±5.7)% for urine samples (with 3.49 dpm plutonium-239), (80.4±4.4) % and (82.4±3.3) % for air and aerosol samples (with 9.14 dpm plutonium-239) respectiveiy. The electro-deposition prevents the release of irritative gas. The lowest detectable limit is 0.04 dpm/1.5 l urine (confidence limits 95%) with a counting time of 24 hr for urine samples and 2 aCi/1 for 10 m³ of collected air samples. The decontamination effect for common α-radionuclides, such as uranium, polonium etc. , is quite good, but not so for neptunium.

The procedure can be applied to routine assay of urine samples of the occupationally exposed personnel and air samples from different plutonium plants. It is also useful for the survey of natural background radioactivity.