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PubMed2006

Stabilization/solidification of hazardous and radioactive wastes with alkali-activated cements.

This paper reviews progresses on the use of alkali-activated cements for stabilization/solidification of hazardous and radioactive wastes. Alkali-activated cements consist of an alkaline activator and cementing components, such as blast furnace slag, coal fly ash, phosphorus slag, steel slag, metakaolin, etc., or a combination of two or more of them. Properly designed alkali-activated cements can exhibit both higher early and later strengths than conventional portland cement. The main hydration product of alkali-activated cements is calcium silicate hydrate (CSH) with low Ca/Si ratios or aluminosilicate gel at room temperature; CSH, tobmorite, xonotlite and/or zeolites under hydrothermal condition, no metastable crystalline compounds such as Ca(OH)(2) and calcium sulphoaluminates exist. Alkali-activated cements also exhibit excellent resistance to corrosive environments. The leachability of contaminants from alkali-activated cement stabilized hazardous and radioactive wastes is lower than that from hardened portland cement stabilized wastes. From all these aspects, it is concluded that alkali-activated cements are better matrix for solidification/stabilization of hazardous and radioactive wastes than Portland cement.

Alkalies↗
PubMed2006

The GIS-based SafeAirView software for the concentration assessment of radioactive pollutants after an accidental release.

The European Commission Joint Research Centre (JRC) in Ispra (Italy) has long been running nuclear installations for research purposes. The Nuclear Decommissioning and Facilities Management Unit (NDFM) is responsible for the surveillance of radioactivity levels in nuclear emergency conditions. The NDFM Unit has commissioned the implementation of a specifically developed decision support system, which can be used for quick emergency evaluation in the case of hypothetical accident and for emergency exercises. The requisites were to be a user-friendly software, able to quickly calculate and display values of air and ground radioactive contamination in the complex area around JRC, following an accidental release of radioactive substances from a JRC nuclear research installation. The developed software, named "SafeAirView", is an advanced implementation of GIS technology applied to an existing MS-DOS mode dispersion model, SAFE_AIR (Simulation of Air pollution From Emissions_Above Inhomogeneous Regions). SAFE_AIR is a numerical model which simulates transport, diffusion, and deposition of airborne pollutants emitted in the low atmosphere above complex orography at both local and regional scale, under non-stationary and inhomogeneous emission and meteorological conditions. SafeAirView makes use of user-friendly MS-Windows type interface which drives the dispersion model by a sequential and continuous input-output process, allowing a real time simulation. The GIS environment allows a direct interaction with the territory elements in which the simulation takes place, using data for the JRC Ispra region represented in geo-referenced cartography. Furthermore it offers the possibility to relate concentrations with population distribution and other geo-referenced maps, in a geographic view. Output concentration and deposition patterns can be plotted and/or exported. In spite of the selected specific databases, the SafeAirView software architecture is a general structure, therefore the decision support system could be easily modified to be applied in a region different from the JRC one. Beside the description of SafeAirView, the present paper presents a statistical evaluation of the software, which has considered three well known tracer experiments: Copenhagen, Indianapolis and Kincaid. The data sets related to these experiments are all included in the so called Model Validation Kit.

Data Interpretation, Statistical↗
PubMed2004

Radioactively contaminated electric arc furnace dust as an addition to the immobilization mortar in low- and medium-activity repositories.

Electric arc furnace dust (EAFD), generated by the steel-making industry, is in itself an intrinsic hazardous waste; however, the case may also be that scrap used in the process is accidentally contaminated by radioactive elements such as cesium. In this case the resulting EAFD is to be handled as radioactive waste, being duly confined in low- and medium-activity repositories (LMAR). What this paper studies is the reliability of using this radioactive EAFD as an addition in the immobilization mortar of the containers of the LMAR, that is, from the point of view of the durability. Different mixes of mortar containing different percentages of EAFD have been subjected to flexural and compressive strength, initial and final setting time, XRD study, total porosity and pore size distribution, determination of the chloride diffusion coefficient, dimensional stability tests, hydration heat, workability of the fresh mix, and leaching behavior. What is deduced from the results is that for the conditions used in this research, (cement + sand) can be replaced by EAFD upto a ratio [EAFD/(cement + EAFD)] of 46% in the immobilization mortar of LMAR, apparently without any loss in the long-term durability properties of the mortar.

Cementation↗
PubMed1992

Radioactive contamination of food sampled in the areas of the USSR affected by the Chernobyl disaster.

In October 1990 a Netherlands humanitarian fact finding mission on aid to people affected by the Chernobyl disaster visited contaminated regions in Russia, Byelorussia and the Ukraine. The mission consisted of medical, socio-psychological and agricultural experts. The results of radioactivity measurements on food products sampled in the contaminated areas are reported here and the radiation burden for the Soviet citizens due to these products is discussed. The radiocaesium contamination measured in 19 food products ranged between 0 and 170 Bq kg-1 and 40K from 25 to 200 Bq kg-1 in the fresh product. Strontium-90, measured in a few samples, was found to be between 1.8 and 30 Bq kg-1. Mushrooms and reindeer moss were very highly contaminated: from 103,000 to 284,000 Bq kg-1 of radiocaesium in the fresh product. Strontium-90 in these samples was 7.8-1550 Bq kg-1. The contamination of all food products was far below the stated limits, except for mushrooms. Extrapolation of the results to the total food consumption gave the radioactive burden due to this food as an estimated 0.2 mSv per year. All of the food products investigated, except mushrooms, can be regarded as safe with respect to radioactive contamination. In addition to sampling agricultural produce, field exposure measurements were also carried out. The measured values, expressed in equivalent doses, ranged from 1.8 to 14 mSv per year at a height of 1 m, with a median value of about 4 mSv per year.

Accidents↗
PubMed1987

Surface radioactivity resulting from the deposition of 222Rn daughter products.

Studies of indoor radiation environments typically involve measurements of 222Rn, airborne 222Rn decay products, and the degree of radioactive equilibrium. This paper describes the relationship between the 222Rn in air, and the level of surface radioactivity that results from the build-up and decay of the daughter isotope, 210Pb. Samples of 222Rn were collected from Mystery Cave, which is located in southeastern Minnesota and from the basement of a house in Minneapolis, MN. Lead-210 was measured on surfaces within the cave, on a rock removed from the cave, and on a basement window. Surface alpha activities were measured on the rock sample and on the window. Radon-222 concentrations in the cave air ranged from 3 to 13 kBq m-3. In the basement, 222Rn levels were between 0.2 and 0.4 kBq m-3. Virtually all the surface radioactivity resulted from the deposition and decay of airborne 222Rn daughter products and was not produced by the decay of U in the rock. Radon-222 concentrations in the cave air were almost 30 times higher than in the basement air; however, the surface 210Pb activity in the cave was 100 times higher than that in the basement. This suggests that in the cave air, 222Rn daughter products are more likely to reach the walls and decay to 210Pb. The measurements of surface alpha activity did not show a similar trend primarily because 210Pb had diffused further into the coating of dirt on the rock than into the glass of the window. The resulting surface activity of the rock was lower than expected based on the 210Pb concentration, because many of the alpha-emitting nuclei were at depths beyond the range of emitted alpha particles. On surfaces where the penetration range of alpha particles is greater than the diffusion depth of 210Pb atoms, either the 210Pb concentration or surface alpha-activity measurements should provide estimates of average long-term 222Rn concentrations.

Air Pollutants↗
PubMed1989

Assessment of radiological emissions from Spanish coal power plants: radioactive releases and associated risks.

The radioactivity of coals and ashes from Spanish coal power plants (CPP) was evaluated. This radioactivity is due mainly to 40K and the U and Th series. The samples were measured in secular equilibrium using a NaI(T1) detector. The annual average airborne releases were also evaluated. An atmospheric dispersion model was developed to predict the annual average concentration of radionuclides in air. The risks from inhalation were calculated and compared with those from nuclear power plants (NPP) and natural radioactivity.

Air Pollutants↗
PubMed2003

Resuspension: decadal monitoring time series of the anthropogenic radioactivity deposition in Japan.

Monthly atmospheric depositions of (90)Sr and (137)Cs have been observed at the Meteorological Research Institute (MRI), Tsukuba, Japan. This study reports temporal trends and levels of (90)Sr and (137)Cs depositions in the 1990s. Although the current (90)Sr and (137)Cs concentrations declined dramatically, they have been found continuously in the deposition samples throughout the 1990s. During this period, the annual (90)Sr ((137)Cs) deposits at MRI ranged from 70-180 (140-350) mBq/m(2)/year. With a sufficiently long time series, the decreasing trend of the deposition evidently differs from the past stratospheric fallout; it is far slower. Thus, reservoirs other than the stratosphere provide small amounts of (90)Sr and (137)Cs to the atmosphere. A simple calculation clearly refutes the significance of the ocean as a potential source of airborne anthropogenic radioactivity. We will demonstrate that these radionuclides in the deposited materials originate from resuspension processes (soil dust suspension processes). The temporal trends of the time series monitoring reveal differences from those in the UNSCEAR Report 2000, which were predicted by a model that disregarded resuspension. The specific activity of (90)Sr ((137)Cs) in the annual depositions exhibited a 10-year (20-year) half-life. Those data were comparable with values reported in the literature for the half-residence time (HRT) of (90)Sr and (137)Cs in Japanese surface soils. They were also comparable to those calculated from nationwide data of (90)Sr and (137)Cs concentrations in the surface soil (0-10 cm) obtained from the Ministry of Education, Culture, Sports, Science and Technology Environmental Radiation Database (the MEXT Database). Regarding the activity ratio of (137)Cs/(90)Sr, the Japanese nationwide surface soil data collected during the 1990s in the MEXT Database (median: 5.3, n = 584) did not accord with that in the deposition samples (average: 2.1, n = 82) at MRI. This supports our previous hypothesis that Asian dust may transport a large fraction of anthropogenic radioactivity into the Japanese atmosphere. We need to study the fate of long-lived anthropogenic radioactivity dispersed in the environment over greater spatial and temporal scales.

Air Pollutants, Radioactive↗
PubMed1994

An approach to detecting delayed effects of radioactive contamination on industrial-urban-area dwellers.

Detecting changes in humans that result from radioactive contamination of the area of residence many years after an incident (i.e., when the radiation has substantially decayed) presents a difficult epidemiological problem. Problems of this kind are even more complicated ina areas where the population is continually exposed to other harmful man-made factors. The city of Kamensk-Uralsky (Sverdlovsk region, Russia) is a good case in point. In 1957, part of Kamensk-Uralsky was contaminated as the result of an accident at the Kyshtym nuclear plant. In addition, the population of the contaminated area is being exposed to atmospheric emissions from several industrial enterprises. Two comparable groups of residents were formed: one in the contaminated are and another in a control area within the same city characterized by similar levels of chemical pollution but substantially lower radioactive contamination. The groups were composed of only those people who had been living in these areas continually since time of the accident and who were under 15 years of age at the time of the accident. The groups were matched by sex, age, and socio-occupational characteristics. For each subject, data were gathered on more than 50 parameters including hematological, immunological, and biochemical indices of the health status. All these data were obtained from blood tests taken in the fall of 1992. Data processing was carried out with the help of a computerized mathematical pattern recognition methodology, which ensured reliable discrimination between the generalized health status in the areas under study. We found that the health status of inhabitants of the area more contaminated with radioactive fallouts was adversely affected by radiation.

Adult↗
PubMed1976

Survey of radioactive agents for in vitro labeling of phagocytic leukocytes. II. Particles.

When various radioactive particles are incubated and tumbled in concentrated suspensions of blood phagocytes at body temperature for 1 hr, they bind to the phagocytic cells with a labeling yield of 30-40%. In vitro experiments show that, for some radioactive colloids, a sizeable fraction of the total cellular binding results from nonspecific surface adsorption to other cells and from reversible surface adsorption to phagocytes without engulfment. No completely satisfactory in vitro methods have been found for separating leukocytes with completely engulfed particles from those with surface-adherent particles; nonetheless, surface adherence can be partially reversed by 20% acid citrate dextrose (ACD) solution or by an excess of nonradioactive colloid. Gelatinization of colloidal particles tends to increase their binding to phagocytic cells but also increases the degree of nonspecific adherence to other cells. Technetium-99m-millimicrospheres, 0.5-2 mum in diameter, are optimal in size for phagocytosis by neutrophils, and their non-specific adherence to other cells is minimal. Because of the microspheres' poor stability in aqueous suspension, however, it is technically difficult to separate free from phagocytosed radioactivity after cell incubation. The highly stable small-particle colloids (less than 0.1 mum), such as 198Au-colloid or 111In-colloid without iron carrier, are phagocytosed poorly or not at all by neutrophils, although they are engulfed by mononuclear cells.

Chlorides↗
PubMedDate not supplied

[Destruction of radioactive particles by strains of Cladosporium cladosporoides (FRES.) de Vries].

Reactions on the ionizing radiation of 14 Cladosporium cladosporioides strains were studied. Only 5 of them displayed radiotropizm. The ability of C. cladosporioides strains 4 and 5 with positive radiotropizm and museum C. cladosporioides strain 396 and its alb-mutant SM without positive radiotropizm to destruct radioactive particles of Chernobyl and explosion origin was studied. Two ways of radioactive particles destruction by C. cladosporioides were established, one of them is a direct way by fungal overgrowth of hot particles and the second one an indirect way only by fungal metabolites. Mycelium of the studied C. cladosporioides strains sorbed radionuclides from radioactive particles during cultivation on the liquid and agarized media. No certain inclinations of the individual strains to accumulation of radionuclides 137Cs or 152Eu were ascertained.

Cesium Radioisotopes↗
PubMed2001

[Determination of content and specific activity of radioactive elements in phosphate slag by spectral and energy spectrum analysis].

Phosphate slag is the slag discarded after phosphate ore is smelted. The content and specific activity of radioactive elements in slag must be determined accurately for environmental protection and comprehensive utilization. This paper discusses how IR spectrum and X-ray diffraction method are used to study its components. The main phase composition is glassy slag. The samples are decomposed with HF-HNO3-HClO4. After anion-exchange separation, arsenazo III is used to determine the content of uranium and thorium in slag. The average content of U is 32.11 micrograms.g-1 and 8.5 micrograms.g-1 for Th. gamma spectrum is used to determine the specific activity of radioactive nuclear elements in it. The specific activities of 226Ra, 232Th and 40K are 112 +/- 2.0% Bq.kg-1, 18.8 +/- 6.4% Bq.kg-1 and 77.6 +/- 3.7% Bq.kg-1, respectively. The values are calculated as follow: M(Ra) = 0.6 Bq.kg-1, M gamma = 0.5 Bq.kg-1. The results show that the values are below 1.0 Bq.kg-1, which is stipulated by national GB6566-86 standard for radioactivity of building materials. The slag is therefore can be utilized to produce slag cement. This provides theoretical basis for the treatment of it.

Elements, Radioactive↗
PubMed2003

Natural specific radioactivity in different soils. Transfer in the soil plant food chain.

In order to warrant customer's health we must pay attention to the quality of the environment and production processes; that means look all over alimentary chain. Media speak often about this topics, because of the interest of the public opinion regarding agribusiness; Nether the less much is know about soil radioactivity, but often scant attention is directed to the knowledge of the amount what remains in food and arrives to the man who is the last and main user of the product. As a consequence of that, we have done some originals studies concerning specific radioactivity in alimentary chain: soil-plant-food. These studies have been made in relation with geopedologic position of fields in volcanic, clayey, sandy soils of Latium. We have measured radioactive activity over some alimentary chains both annual (like turnip and garden cress) and pluriannual (such as vine). We made comparisons on the same soils studying the following natural markers: K40, Pb214, and Bi214; and Cs137, one of the main natural markers.

Food Chain↗
PubMed2006

[Experimental study on the treatment of low level radioactive waste water by inorganic nanofiltration membrane].

Soluble sodium poly(acrylic) acid (NaPAA) with molecular weight of 2000-5000 was selected as an assistant reagent of inorganic nanofiltration membrane which was used to treat low level radioactive waste water mainly containing radionuclides 90Sr, 137Cs and 60Co. The effect of non-active simulated wastewater pH and NaPAA concentration on the retention efficiency of non-active nuclides strontium, cesium and cobalt ions and membrane permeation flux were explored, and the effect mechanism was also preliminarily discussed. The optimum process parameters were decided: pH 7-8, NaPAA volume concentration no lower than 0.1%. Real radioactive waste water was treated under optimum experiment condition. The results show that the decontamination efficiency of total beta and gamma emitters of low-level radioactive wastewater were both up to about 95% by inorganic nanofiltration assisted by NaPAA, and the permeation flux was also satisfying.

Membranes, Artificial↗
PubMed1991

[Nuclear medicine--personnel exposure and release of radioactivity].

The Nuclear Medicine Division and 30 other groups at the University of Hannover School of Medicine are taken as examples to describe the diagnostic, therapeutic and research uses of radioactivity and the effectiveness of the associated radiation protection. The evolution of radiation exposures of 520 employees followed over the last six years and the methods used for the disposal of radioactive waste are explained. The adaptation of protective measures to individual and, in particular, specific working conditions has led to approximately 90% of all exposures remaining under the detection limit of the personal dosimeters during the entire observation period. Only a few people contributed to the collective radiation dose. In 1990, the average annual dose equivalent among personnel in the Nuclear Medicine Division was 0.12 mSv/person. By the installation of facilities for the storage of isotopes with short half-lives and of filters in the air circulation system, environmental contamination could be held much below the legal limits. Combustible and liquid waste containing radionuclides with long half-lives such as tritium and 14C had to be disposed of separately. However, they were a small fraction of the total radioactivity used.

Environmental Pollutants↗
PubMedDate not supplied

Chernobyl three years later: radiobiologic evaluation of a radioactive contamination.

On April 26, 1986, after partial fusion and confining loss by explosion of a nuclear reactor, 5 x 10(7) Ci of radionuclides escaped from Chernobyl. Three years later, maps show contamination by radioactive isotopes (formed during that period) of 21,000 km2 of Soviet soil, mainly in Byelorussia and part of the Ukraine. Decontamination measures have not been effective to date and 135,000 persons are being followed medically, taking into account the radioactive doses they received. An initial excess of morbidity from solid tumors has been noted much sooner than in the case of Hiroshima and Nagasaki, but its significance is in dispute. Three years later, only the extent of the ecologic disaster caused by the radioactive contamination can be confirmed. It is too early to draw conclusions about radiation-induced carcinogenesis for the contaminated population.

Accidents↗
PubMed1993

[Prevalence of radioactive particles in the territory of Byelorussia and their contents in the lungs].

Examination conducted in 1987--1988 included 200 samples of the autopsy material of subjects who died of various causes in different regions of Byelorussia. It revealed the presence of "hot" particles (i.e. particles with high specific radioactivity) in 50% of the samples taken from the northwest and in 70% of those from the southeast regions. A correlation was found to exist between the radioactive particles content in the soil, air and lungs of residents from the contaminated territory. It was shown that in 1990--1991, in contrast to 1987--1988, the particles content in a single lung sample reduced, which was associated both with mechanical removal of particles and their disintegration and, as a consequence with the accumulation of plutonium in the body. Study of radioactive particles distribution in the whole lung showed that at present they are found primarily in the lower segments.

Autopsy↗
PubMedDate not supplied

[Ecological consequences of radioactive pollution for soil bacteria within the 10-km region around the Chernobyl Atomic Energy Station].

The diversity of aerobic chemoorganotrophic (capable of growing on nutrient agar) bacteria in radioactive soil (0.3-17.0 microCi/kg soil) sampled in the 10-km zone around the Chernobyl Nuclear Power Plant (CNPP) was found to be lower than that observed in control, uncontaminated soil with a radioactivity of 0.002-0.006 microCi/kg soil. All the radioactive soil samples contained the bacteria Bacillus cereus and Methylobacterium extorquens or M. mesophillicum, which exhibited a high tolerance to 0.3-1.0 M hydrogen peroxide, whose action can to a certain extent simulate the effect of ionizing radiation. Some of the contaminated soil samples contained other species of chemoorganotrophic bacteria with a low tolerance to H2O2. The survival of bacteria in the Chernobyl accident zone is probably due to the functioning of mechanisms efficiently neutralizing peroxide compounds and repairing radiation-damaged DNA. The population of cellulolytic, nitrifying, and sulfate-reducing bacteria in contaminated soil was found to be 1-2 orders of magnitude less than in control soil, indicating the unfavorable effect of anthropogenic radiation on the abundance and diversity of soil bacteria.

Bacillus cereus↗
PubMedDate not supplied

[Size distribution of artificial and natural radioactive aerosols in the 30-kilometer zone of the Chernobyl AES in 1986-1996].

During 10 years after the Chernobyl accident the systematical measurings of size distributions of radioactive aerosols were conducted near the block-IV. In the ground level the active median aerodynamic diameters (AMAD) of 137Cs aerosols were ranged from 0.4 up to 1.4 microns in May, 1986. In that time the aerosol carriers of radioactive Te, Ru and I had AMAD 0.3 ... 0.5 micron. During 1987-1996 AMAD of aerosol of fission products of the Chernobyl accident was stable in range 4 ... 7 microns. Simultaneously concentrations and size distributions of natural radioactive aerosols were determined. The cosmogenic 7Be aerosols had AMAD 0.5 ... 0.7 micron. AMAD of the aerosols of daughter products of radon and thoron was found 0.4 ... 0.6 micron.

Aerosols↗