Radioactivity from natural,industrial, and other sources

Natural radioactivity and the use of x-rays and radioactive substances in the practice of medicine are the main sources of radiation exposure to the general public. The protection standards used in all countries are based on the recommendations of the International Commission on Radiological Protection. These standards are being observed by the nuclear industry and have succeeded in protecting both nuclear workers and members of the general public. The dose received from nuclear power generation is a tiny fraction compared to the doses received from nature and medical practice.However, a great gap exists between the risks of low-level radiation exposure as perceived by the public and the risk that actually exists. This is true not only concerning nuclear power generation, but also with respect to the need to dispose of both high-level and low-level wastes. In addition, the dangers of plutonium have become distorted in the public mind. Fifty years of research into the biological effects of plutonium have been reassuring and an excellent safety record has been achieved in the industrial production of this material.     

宝兴大理石矿的放射性检测

宝兴县境内的大理石资源以其白度高、储量丰、品质优、易开采而享誉中外。对四川省宝兴县陇东镇大理石矿区进行了放射性环境地质调查,通过对取回的大理石样品中226Ra、232Th、40K这3种核素的比活度的测定,根据比活度换算出这几种核素的外照射指数和内照射指数,把所得结果和中华人民共和国国家标准《建筑材料放射性核素限量》中规定的建筑性材料分类标准作对比后发现其内照射指数与外照射指数都符合《建筑材料放射性核素限量》中A类建筑材料和装饰材料的要求,它的产销与适用范围不受限制。     

Ultraviolet Radiation at Sites on the Antarctic Coast

Ground-based measurements of solar UV irradiance combined with calculations using satellite-based ozone data are able to define the variability in UV sunlight at Palmer Station and McMurdo Station, Antarctica over time scales of years. Special attention focuses on the spring and summer seasons. Satellite data show that the annual ozone loss that occurs during October was greater in1991–1992 than in1979–1980. This led to average noontime UVB irradiances computed for clear skies in the latter period that exceeded those in the earlier time by50–65%. However, a biologically weighted irradiance for suppression of photosynthesis in phytoplankton indigenous to the area near McMurdo Station increased by at most 5% over this period in response to the change in ozone owing to an important contribution from the UVA. At Palmer Station the behavior of ozone and cloudiness can mesh so as to produce the largest noontime UVB irradiances of the year in October as opposed to near summer solstice in December and January. Interannual variability in UVB irradiance during October, the month of the major ozone loss, is larger at Palmer than at McMurdo during the time spanned by ground-based irradiance measurements, being1990–1994. However, interannual variations in cloudiness were more important than changes in ozone in causing the observed year-to-year variability at Palmer Station. The opposite situation prevailed at McMurdo during October, where interannual variations in ozone were responsible for most of the year-to-year differences in UVB received at the ground.     

Radioactivity levels in jurak and moasel,comparison with cigarette tobacco

Jurak and moasel are tobacco products that contain, in addition to tobacco, juice of sugar cane, fruits, spices, tar and nicotine. These products are smoked by hubble-bubble, a popular smoking habit in the Middle Eastern and North African countries. Charcoal is put directly on these products during smoking and the smoke passes through water for cooling purpose before it goes to the lung, without filtering. Radioactivity levels were measured in these products, tobacco leaves, charcoal and in cigarette tobacco of most well known brand names by gamma spectrometry system consisting of HPGe detector coupled to a PC-based 8192 channel multichannel analyzer. The average²²⁶Ra concentrations in jurak, moasel, tobacco leaves, charcoal and cigarette tobacco in Bq/kg were: 3.4, 1.8, 3.2, 2.9 and 7 respectively; that of²³²Th were: 3.8, 2.6, 3.5, 2.2 and 7.8 respectively; that of⁴⁰K were 620, 445, 511, 163 and 876 respectively. It is expected that a jurak smoker inhales 10 times the radioactivity and a moasel smoker twice that compared to a 25 cigarette/d smoker.     

Radioactivity Group,Atomic Physics Division,Physikalisch-Technische Bundesanstalt,Braunschweig, Federal Republic of Germany

The scientific activity and organisation of the Radioactivity Group, Atomic Physics Division, Physikalisch-Technische Bundesanstalt, Braunschweig, FRG is discussed.     

Radioactivity in the highly contaminated area near the Chernobyl site

Field measurements of radioactivity were performed in highly contaminated areas around Chernobyl in the summer of 1990. Six radionuclides including the most dominant¹³⁷Cs have been identified in soil samples through -ray spectrometry. The relation between the -ray dose rate above the ground and the radioactivity density in soils has been investigated. The external dose from deposited radiocesium for the period of 70 years after the deposition has been evaluated to be about 5 mSv per 1 and 0.5 Ci km^–2 of¹³⁷Cs and¹³⁴Cs deposition, respectively.     

Epithermal neutron flux characterization of the TRIGA MARK II reactor,Ljubljana, Yugoslavia,for use in NAA

The nonideality of the epithermal neutron flux distribution at a reactor site can be described by a 1/E¹⁺ spectrum representation, with parameter being a measure of the nonideality. -values were determined in 3 typical irradiation positions of the TRIGA MARK II reactor of the Jozef Stefan Institute, Ljubljana, Yugoslavia, using the Cd-ratio for multi-monitor method. The simpler Cd-ratio for dual monitor method (monitors:¹⁹⁷Au–⁹⁴Zr) also yielded reliable results. This characterisation is of use in the k₀-method of NAA, which is recently introduced at the Institute.     

Radioactivity of teeth in the follow-up of old contamination cases

The activity of plutonium and americium has been measured in teeth from two persons involved in an incident 25 years ago at Eurochemic. Assuming that the alpha activity of the teeth is representative of the activity of the skeleton an estimate of the systemic body burden is given and compared to the value obtained from the late urinary excretion using the Leggett-Eckerman excretion model. The results are compared with some data from US Transuranium and Uranium Registries.     

Radioactivity of cattle fodder and milk after the Chernobyl accident

The radioactivities of⁹⁰Sr,¹³⁷Cs and¹³⁴Cs have been measured in soil, fodder and milk from the south-western region of Slovenia, Yugoslavia after the Chernobyl accident. Maximal concentrations of Sr-isotopes in samples and the rate of their decrease in a period up to two years after the accident are given. The transfer of radionuclides from soil to grass and from fodder to milk is discussed.     

Radioactivity in groundwater along the borders of Oman and UAE

Characterizing the quality and radioactivity of groundwater is vital as it represents valuable resource in arid regions. Here we present radioactivity level in groundwater collected from wells in a region along the border between Sultanate of Oman and United Arab Emirates (UAE). The aquifers are alluvium deposits (silt, sand and gravel) and the measured groundwater radioactivity (including ²³²Th, ²³⁸U, ²³⁵U, ²²⁶Ra, ²²²Rn, gross-α and gross-β) indicates values below the WHO permissible limits for drinking water. The results also show large difference in radioactivity fingerprints, in particular for ²²⁶Ra and ²²²Rn within the investigated aquifers. The data further indicate lower radioactivity in groundwater of the alluviums compared to the carbonate aquifers in the region. This feature makes the alluvium aquifers valuable reservoirs that should be carefully exploited as a source of groundwater. As this is the first investigation on the radioactivity of groundwater in alluvial aquifers in the region, it suggests that other alluvial deposits, particularly those inland and far from the marine water intrusion or seepage from carbonate rocks would have low radioactivity fingerprints.     

Characteristics of the tritium distribution in the Danube basin region in Yugoslavia

The investigated water samples were collected from rivers, underground waters and precipitations at different locations near Belgrade during the period 1976–1979. By preconcentration and scintillation counting, the individually and monthly collected samples were analyzed for³H contents. It has been found that the³H-concentration in monthly river water samples (Danube, Sava, Tisa) varies from 39 to 196 TU with a maximum in summer, between 0–192 TU in the underground water depending on the sampling depth and distance from river Sava and Danube, while values of 26 to 153 TU have been detected in the monthly precipitation samples attaining a maximum during the break-through of arctic and polar continental air masses. The results were used to calculate the³H quantity deposited per m² (Bq/m²) of surface, due to precipitations and the flow per second (Bq/s) in the investigated locations in rivers. The interrelation between rivers, underground waters and precipitations is discussed. The³H-distributions obtained are correlated with the water level in rivers and with the precipitation quantities and are interpreted in light of the relevant meteorological parameters and other related phenomena.     

Radioactivity levels and radiation hazard of healing mud from San Diego River, Cuba

Healing mud core samples were collected in the San Diego River (Southwest Cuba), in order to determine the behaviour of the radioactivity levels of ²²⁶Ra, ¹³⁷Cs, ²³²Th and ⁴⁰K and to evaluate their possible radiological impact on peloide therapeutic uses. The radionuclide concentration ranges in healing mud profiles on Bq kg^?1 dry weight varied as follows: ²²⁶Ra = 22–26, ¹³⁷Cs = 4.6–33.0, ²³²Th = 18–31 and ⁴⁰K = 208–433. The calculated average radium equivalent activity (82 Bq kg^?1), total absorbed dose rate (40 nGy h^?1), external hazard index (0.23), annual gonadal dose equivalent (280 μSv h^?1) and annual effective dose equivalent (48.5 μSv y^?1) are less than international recommended values. Hence, the levels of radioactivity in healing muds from San Diego River are not an impediment for its use for medical proposes.     

Radioactivity distribution of thorium in sediment core of the Sabah-Sarawak coast

Thorium activity concentrations were measured in seven marine sediment cores taken from Sabah-Sarawak coast on 2004 by using a gravity box corer. Collected sediments were generally homogenous mud which contained much more mixture of silt and clay compared to sand and relatively low content of organic carbon (i.e. less than 5% at all sampling stations). The results found that activity concentrations of ²³⁰Th, ²³²Th and ratios of ²³⁰Th/²³²Th were ranged from 6.5–20.4 Bq/kg dry wt., 6.8–27.8 Bq/kg dry wt. and 0.69–0.92, respectively. It seem that, ²³²Th activity concentrations are slightly higher than ²³⁰Th at all sampling stations and both radionuclides were generally high at Sabah compared to Sarawak coastal waters. ²³⁰Th activity concentrations in sediment core appear to be correlated with the activity concentrations of ²³²Th at some sampling station. These indicating both radionuclides were supplied from the same of environment and source origin of detrital from terrestrial and shallower water. The low ²³⁰Th/²³²Th activity ratio which is less than unity suggesting that ²³²Th was actively and rapidly regenerated compared to ²³⁰Th from ²³⁴U. It also can be attributed to less efficiently scavenge of ²³⁰Th onto particles prior deposited at the marine sediment bed.     

A Newly Isolated Pseudomonas sp., Epibiotic on the Seaweed, Padina tetrastromatica, off Southeastern Coast of India, Reveals Antibacterial Action

Epibionts from the red (Hypnea valentiae) and brown seaweeds (Padina tetrastromatica) were rapidly isolated on Zobell agar medium. All the isolates from both the seaweeds (76 numbers) were tested against five human pathogens which were resistant to at least one of the commercially available antibiotics at a minimal concentration of 10 mg. The most antibiotic productive isolate (PT19) from Padina tetrastromatica was extracted and observed to inhibit Klebsiella pneumoniae and Pseudomonas aeruginosa with zone sizes of 15 and 10 mm radius, respectively, at a concentration of 300 μg. Further, a direct bioautography was done and an inhibition was witnessed against the aforementioned pathogens even at 2 μg concentration around three spots (R _f values 0.6, 0.7, and 0.8). Preparative thin-layer chromatography yielded a yellow sticky compound (6 mg) which was identified as an alkaloid. The compound on reversed-phase high-pressure liquid chromatography analysis yielded two major and two minor peaks with retention times, 3.1, 4.2, 4.7, and 4.9 min, respectively. The antibacterial compound was recorded 96.6 % pure, and the producer strain was identified as Pseudomonas sp. To our knowledge, we are the first to isolate and identify Pseudomonas from Padina tetrastromatica producing antibacterial alkaloids. This study will pave way for exploring more bacterial load from the said algal groups for bioactivities.     

核电站周围环境放射性最佳监测点数的研究

本文研究的是广东大亚湾核电站周围区域环境放射性监测最佳监测点数问题,分别对正态分布、对数正态分布、t分布和对数t分布等模型求出了监测点数的最佳数量。用车贝雪夫不等式求出了任意分布下监测点数上限值。为了节省人力、物力和时间,对采用监测复合样品的办法进行了探讨。