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Farfan, E

Publications and source records attributed to Farfan, E.

ASSESSMENT OF 90SR AND 137CS PENETRATION INTO REINFORCED CONCRETE (EXTENT OF 'DEEPENING') UNDER NATURAL ATMOSPHERIC CONDITIONS

When assessing the feasibility of remediation following the detonation of a radiological dispersion device or improvised nuclear device in a large city, several issues should be considered including the levels and characteristics of the radioactive contamination, the availability of resources required for decontamination, and the planned future use of the city's structures and buildings. Currently, little is known about radionuclide penetration into construction materials in an urban environment. Knowledge in this area would be useful when considering costs of a thorough decontamination of buildings, artificial structures, and roads in an affected urban environment. Pripyat, a city substantially contaminated by the Chernobyl Nuclear Power Plant accident in April 1986, may provide some answers. The main objective of this study was to assess the depth of {sup 90}Sr and {sup 137}Cs penetration into reinforced concrete structures in a highly contaminated urban environment under natural weather conditions. Thirteen reinforced concrete core samples were obtained from external surfaces of a contaminated building in Pripyat. The concrete cores were drilled to obtain sample layers of 0-5, 5-10, 10-15, 15-20, 20-30, 30-40, and 40-50 mm. Both {sup 90}Sr and {sup 137}Cs were detected in the entire 0-50 mm profile of the reinforced cores sampled. In most of the cores, over 90% of the total {sup 137}Cs inventory and 70% of the total {sup 90}Sr inventory was found in the first 0-5 mm layer of the reinforced concrete. {sup 90}Sr had penetrated markedly deeper into the reinforced concrete structures than {sup 137}Cs.

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EDITORIAL HPJ SPECIAL ISSUE INTRODUCTION

Radioecology is the study of the fate and transport and potential effects of radionuclides and associated contaminants in the environment. In short, it is the science that describes the fundamental connection between environmental health and human health risks. As such, radioecology can and has provided the credible, consistent and defensible basis for the successful and cost-effective environmental cleanup and closure of nuclear production and waste sites. In addition, radioecology also provides the technical basis for making timely and reliable decisions on cleanup in the aftermath of nuclear incidents such as Chernobyl and Fukushima. The 1986 Chernobyl Nuclear Power Plant (ChNPP) accident resulted in catastrophic health, social, and economic consequences in many countries, predominantly, Ukraine, Belarus, and Russia. The extent of radioactive contamination, levels and forms of contamination, and diversity of the ecosystems affected by the accident did not have any precedent and provided unique opportunities for environmental scientists around the world. Following the natural course of their development, populations of species and their communities found themselves in conditions of chronic radiation exposure that exceeded the natural background by factors of hundreds and thousands. Anything similar would have been extremely difficult if not impossible to recreate in a scientific laboratory. Consequently, since the first few years after the accident, many teams of scientists have visited the Chernobyl Exclusion Zone (ChEZ). The knowledge gained by studying the consequences of this accident has tremendous importance. The concept of an international research and technical center to address the problems involving nuclear and radiological accidents became a reality with the establishment of the International Chernobyl Center (ICC). In May 1995, the US and Ukraine signed a Protocol of Intent on establishment of the ICC, and the government of Ukraine appealed to the international scientific community to support ICC and join its activities (Chernobyl Center 2006). In December 1995, a memorandum of understanding (MOU) on the ChNPP closure was signed by the government of Ukraine, all of the G7 governments, and the European Commission. The ICC foundation was considered critical to ensure the safe decommissioning of the ChNPP reactor units and improvement of the safety of the Chernobyl Containment Shelter. On the 10th anniversary of the Chernobyl accident (26 April 1996), Mr. Viktor Yushchenko, the President of Ukraine, issued a decree to establish the Chernobyl Center for Nuclear Safety, Radioactive Waste and Radioecology (Chernobyl Center). On the same day, a MOU involving the US participation in Chernobyl Center activities was signed by the US and Ukraine (Chernobyl Center 2006). In July 1998, the US and Ukraine signed an agreement to establish the International Radioecology Laboratory (IRL) as part of the Chernobyl Center. The creation of IRL was a logical continuation of previous programs to conduct scientific research in radioecology and provide Ukraine and the rest of the world with the necessary infrastructure and scientific basis to conduct research in radioecology, radiobiology, dosimetry, and environmental protection in the ChEZ (Chernobyl Center 2006). A recent collaborative effort with IRL has been implemented through a project titled 'Long-term impacts from radiation/contamination within the Chernobyl Exclusion Zone' (Farfan et al. 2008; Gerdes et al. 2009; Marra et al. 2010). This collaboration had the following objectives: (1) Assess the long-term impacts to the environment from radiation exposure within the ChEZ; (2) Provide information on remediation guidelines and ecological risk assessment within radioactively contaminated territories based on the results of long-term field monitoring, analytical measurements, and numerical modeling of soils and groundwater radioactive contamination; and (3) Recommend the development and testing of effective cleanup technologies to reduce environmental and health risks. Based on this work, a large amount of data are now available for publication, some of which are presented in this Special Issue of the Health Physics Journal.

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OVERVIEW OF THE COOPERATION BETWEEN THE CHERNOBYL CENTER'S INTERNATIONAL RADIOECOLOGY LABORATORY IN SLAVUTYCH, UKRAINE AND U.S. RESEARCH CENTERS BETWEEN 2000-2010

The International Radioecology Laboratory (IRL) located in Slavutych, Ukraine was created in 1999 under the initiative of the United States Government and the Government of Ukraine in the framework of international cooperation on evaluation and minimization of consequences of the Chernobyl nuclear power plant (ChNPP) accident. Since the time the IRL was founded, it has participated in a large number of projects, including the following: (1) study of radionuclide accumulation, distribution, and migration in components of various ecological systems of the Chernobyl Exclusion Zone (ChEZ); (2) radiation dose assessments; (3) study of the effects of radiation influence on biological systems; (4) expert analysis of isotopic and quantitative composition of radioactive contaminants; (5) development of new methods and technologies intended for radioecological research; (6) evaluation of future developments and pathways for potential remediation of the ChEZ areas; (7) assistance in provision of physical protection systems for ionizing irradiation sources at Ukrainian enterprises; (8) reviews of open Russian language publications on issues associated with consequences of the ChNPP accident, radioactive waste management, radioecological monitoring, and ChNPP decommissioning; (9) conduct of training courses on problems of radioecology, radiation safety, radioecological characterization of test sites and environmental media, and on research methods; (10) conduct of on-site scientific conferences and workshops on the ChEZ and radioecology problems; participation in off-site scientific conferences and meetings; and (11) preparation of scientific and popular science publications, and interactions with mass media representatives. This article provides a brief overview of the major achievements resulting from this cooperation between the IRL and U.S. research centers.

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RADIATION DOSE ASSESSMENT FOR THE BIOTA OF TERRESTRIAL ECOSYSTEMS IN THE SHORELINE ZONE OF THE CHERNOBYL NUCLEAR POWER PLANT COOLING POND

Radiation exposure of the biota in the shoreline area of the Chernobyl Nuclear Power Plant Cooling Pond was assessed to evaluate radiological consequences from the decommissioning of the Cooling Pond. The article addresses studies of radioactive contamination of the terrestrial faunal complex and radionuclide concentration ratios in bodies of small birds, small mammals, amphibians, and reptiles living in the area. The data were used to calculate doses to biota using the ERICA Tool software. Doses from {sup 90}Sr and {sup 137}Cs were calculated using the default parameters of the ERICA Tool and were shown to be consistent with biota doses calculated from the field data. However, the ERICA dose calculations for plutonium isotopes were much higher (2-5 times for small mammals and 10-14 times for birds) than the doses calculated using the experimental data. Currently, the total doses for the terrestrial biota do not exceed maximum recommended levels. However, if the Cooling Pond is allowed to drawdown naturally and the contaminants of the bottom sediments are exposed and enter the biological cycle, the calculated doses to biota may exceed the maximum recommended values. The study is important in establishing the current exposure conditions such that a baseline exists from which changes can be documented following the lowering of the reservoir water. Additionally, the study provided useful radioecological data on biota concentration ratios for some species that are poorly represented in the literature.

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VERTICAL MIGRATION OF RADIONUCLIDES IN THE VICINITY OF THE CHERNOBYL CONFINEMENT SHELTER

Studies on vertical migration of Chernobyl-origin radionuclides in the 5-km zone of the Chernobyl Nuclear Power Plant (ChNPP) in the area of the Red Forest experimental site were completed. Measurements were made by gamma spectrometric methods using high purity germanium (HPGe) detectors with beryllium windows. Alpha-emitting isotopes of plutonium were determined by the measurement of the x-rays from their uranium progeny. The presence of {sup 60}Co, {sup 134,137}Cs, {sup 154,155}Eu, and {sup 241}Am in all soil layers down to a depth of 30 cm was observed. The presence of {sup 137}Cs and {sup 241}Am were noted in the area containing automorphous soils to a depth of 60 cm. In addition, the upper soil layers at the test site were found to contain {sup 243}Am and {sup 243}Cm. Over the past ten years, the {sup 241}Am/{sup 137}Cs ratio in soil at the experimental site has increased by a factor of 3.4, nearly twice as much as would be predicted based solely on radioactive decay. This may be due to 'fresh' fallout emanating from the ChNPP Confinement Shelter.

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ASSESSMENT OF THE RADIONUCLIDE COMPOSITION OF "HOT PARTICLES" SAMPLED IN THE CHERNOBYL NUCLEAR POWER PLANT FOURTH REACTOR UNIT

Fuel-containing materials sampled from within the Chernobyl Nuclear Power Plant (ChNPP) 4th Reactor Unit Confinement Shelter were spectroscopically studied for gamma and alpha content. Isotopic ratios for cesium, europium, plutonium, americium, and curium were identified and the fuel burnup in these samples was determined. A systematic deviation in the burnup values based on the cesium isotopes, in comparison with other radionuclides, was observed. The conducted studies were the first ever performed to demonstrate the presence of significant quantities of {sup 242}Cm and {sup 243}Cm. It was determined that there was a systematic underestimation of activities of transuranic radionuclides in fuel samples from inside of the ChNPP Confinement Shelter, starting from {sup 241}Am (and going higher), in comparison with the theoretical calculations.

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METHOD FOR SIMULTANEOUS 90SR AND 137CS IN-VIVO MEASUREMENTS OF SMALL ANIMALS AND OTHER ENVIRONMENTAL MEDIA DEVELOPED FOR THE CONDITIONS OF THE CHERNOBYL EXCLUSION ZONE

To perform in vivo simultaneous measurements of the {sup 90}Sr and {sup 137}Cs content in the bodies of animals living in the Chernobyl Exclusion Zone (ChEZ), an appropriate method and equipment were developed and installed in a mobile gamma beta spectrometry laboratory. This technique was designed for animals of relatively small sizes (up to 50 g). The {sup 90}Sr content is measured by a beta spectrometer with a 0.1 mm thick scintillation plastic detector. The spectrum processing takes into account the fact that the measured object is 'thick-layered' and contains a comparable quantity of {sup 137}Cs, which is a characteristic condition of the ChEZ. The {sup 137}Cs content is measured by a NaI scintillation detector that is part of the combined gamma beta spectrometry system. For environmental research performed in the ChEZ, the advantages of this method and equipment (rapid measurements, capability to measure live animals directly in their habitat, and the capability of simultaneous {sup 90}Sr and {sup 137}Cs measurements) far outweigh the existing limitations (considerations must be made for background radiation and the animal size, skeletal shape and body mass). The accuracy of these in vivo measurements is shown to be consistent with standard spectrometric and radiochemical methods. Apart from the in vivo measurements, the proposed methodology, after a very simple upgrade that is also described in the article, works even more accurately with samples of other media, such as soil and plants.

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CHRONIC IRRADIATION OF SCOTS PINE TREES (PINUS SYLVESTRIS) IN THE CHERNOBYL EXCLUSION ZONE: DOSIMETRY AND RADIOBIOLOGICAL EFFECTS

To identify effects of chronic internal and external radiation exposure for components of terrestrial ecosystems, a comprehensive study of Scots pine trees in the Chernobyl Exclusion Zone was performed. The experimental plan included over 1,100 young trees (up to 20 years old) selected from areas with varying levels of radioactive contamination. These pine trees were planted after the 1986 Chernobyl Nuclear Power Plant accident mainly to prevent radionuclide resuspension and soil erosion. For each tree, the major morphological parameters and radioactive contamination values were identified. Cytological analyses were performed for selected trees representing all dose rate ranges. A specially developed dosimetric model capable of taking into account radiation from the incorporated radionuclides in the trees was developed for the apical meristem. The calculated dose rates for the trees in the study varied within three orders of magnitude, from close to background values in the control area (about 5 mGy y{sup -1}) to approximately 7 Gy y{sup -1} in the Red Forest area located in the immediate vicinity of the Chernobyl Nuclear Power Plant site. Dose rate/effect relationships for morphological changes and cytogenetic defects were identified and correlations for radiation effects occurring on the morphological and cellular level were established.

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FREQUENCY DISTRIBUTIONS OF 90SR AND 137CS CONCENTRATIONS IN AN ECOSYSTEM OF THE 'RED FOREST' AREA IN THE CHERNOBYL EXCLUSION ZONE

In the most highly contaminated region of the Chernobyl Exclusion Zone: the 'Red Forest' site, the accumulation of the major dose-affecting radionuclides ({sup 90}Sr and {sup 137}Cs) within the components of an ecological system encompassing 3,000 m{sup 2} were characterized. The sampled components included soils (top 0-10 cm depth), Molina caerulea (blue moor grass), Camponotus vagus (carpenter ants) and Pelobates fuscus (spade-footed toad). In a comparison among the components of this ecosystem, the {sup 90}Sr and {sup 137}Cs concentrations measured in 40 separate grids exhibited significant differences, while the frequency distribution of the values were close to a logarithmically normal leptokurtic distribution with a significant right-side skew. While it is important to identify localized areas of high contamination or 'hot spots,' including these values in the arithmetic mean may overestimate the exposure risk. In component sample sets that exhibited logarithmically normal distribution, the geometrical mean more accurately characterizes a site. Ideally, risk assessment is most confidently achieved when the arithmetic and geometrical means are most similar, meaning the distribution approaches normal. Through bioaccumulation, the highest concentrations of {sup 90}Sr and {sup 137}Cs were measured in the blue moor grass and spade-footed toad. These components also possessed distribution parameters that shifted toward a normal distribution.

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RADIATION ECOLOGY ISSUES ASSOCIATED WITH MURINE RODENTS AND SHREWS IN THE CHERNOBYL EXCLUSION ZONE

This article describes major studies performed by the Chernobyl Center's International Radioecology Laboratory (Slavutich, Ukraine) on radioecology of murine rodents and shrews inhabiting the Chernobyl Exclusion Zone. The article addresses the long-term (1986-2005) and seasonal dynamics of radioactive contamination of animals, and reviews interspecies differences in radionuclide accumulations and factors affecting the radionuclide accumulations. It is shown that bioavailability of radionuclides in the 'soil-to-plant' chain and a trophic specialization of animals play key roles in determining their actual contamination levels. The total absorbed dose rates in small mammals significantly reduced during the years following the Chernobyl Nuclear Power Plant accident. In 1986, the absorbed dose rate reached 1.3-6.0 Gy hr{sup -1} in the central areas of the Chernobyl Exclusion Zone (the 'Red Forest'). In 1988 and 1990, the total absorbed dose rates were 1.3 and 0.42 Gy hr{sup -1}, respectively. In 1995, 2000, and 2005, according to the present study, the total absorbed dose rates rarely exceeded 0.00023, 0.00018, and 0.00015 Gy hr{sup -1}, respectively. Contributions of individual radiation sources into the total absorbed dose are described.

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RADIOACTIVE WASTE MANAGEMENT IN THE CHERNOBYL EXCLUSION ZONE - 25 YEARS SINCE THE CHERNOBYL NUCLEAR POWER PLANT ACCIDENT

Radioactive waste management is an important component of the Chernobyl Nuclear Power Plant accident mitigation and remediation activities of the so-called Chernobyl Exclusion Zone. This article describes the localization and characteristics of the radioactive waste present in the Chernobyl Exclusion Zone and summarizes the pathways and strategy for handling the radioactive waste related problems in Ukraine and the Chernobyl Exclusion Zone, and in particular, the pathways and strategies stipulated by the National Radioactive Waste Management Program. The brief overview of the radioactive waste issues in the ChEZ presented in this article demonstrates that management of radioactive waste resulting from a beyond-designbasis accident at a nuclear power plant becomes the most challenging and the costliest effort during the mitigation and remediation activities. The costs of these activities are so high that the provision of radioactive waste final disposal facilities compliant with existing radiation safety requirements becomes an intolerable burden for the current generation of a single country, Ukraine. The nuclear accident at the Fukushima-1 NPP strongly indicates that accidents at nuclear sites may occur in any, even in a most technologically advanced country, and the Chernobyl experience shows that the scope of the radioactive waste management activities associated with the mitigation of such accidents may exceed the capabilities of a single country. Development of a special international program for broad international cooperation in accident related radioactive waste management activities is required to handle these issues. It would also be reasonable to consider establishment of a dedicated international fund for mitigation of accidents at nuclear sites, specifically, for handling radioactive waste problems in the ChEZ. The experience of handling Chernobyl radioactive waste management issues, including large volumes of radioactive soils and complex structures of fuel containing materials can be fairly useful for the entire world's nuclear community and can help make nuclear energy safer.

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ENVIRONMENTAL RADIATION MONITORING IN THE CHERNOBYL EXCLUSION ZONE - HISTORY AND RESULTS 25 YEARS AFTER

This article describes results of the radiation environmental monitoring performed in the Chernobyl Exclusion Zone (ChEZ) during the period following the 1986 Chernobyl Nuclear Power Plant accident. This article presents a brief overview of five comprehensive reports generated under Contract No. DE-AC09-96SR18500 (Washington Savannah River Company LLC, Subcontract No. AC55559N, SOW No. ON8778) and summarizes characteristics of the ChEZ and its post-accident status and the history of development of the radiation monitoring research in the ChEZ is described. This article addresses characteristics of the radiation monitoring in the ChEZ, its major goals and objectives, and changes of these goals and objectives in the course of time, depending on the tasks associated with the phase of mitigation of the ChNPP accident consequences. The results of the radiation monitoring in the ChEZ during the last 25 years are also provided.

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EDITORIAL HPJ SPECIAL ISSUE DEDICATION

This issue is dedicated to the heroes and professionals who helped protect the world from nuclear disasters and to those who were displaced by these catastrophes.

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