Incident Angle Dependence of Residual Defect in Silicon Surface Barrier Detector

The fate of radionuclides produced in a light water moderator was investigated by assaying with a Ge(Li) detector sampled coolant water and the waste water produced by regeneration of resins, measuring the radiation dose rates along the surface of the resin column length with TLDs, and studying the sorption of radionuclides to resins in dynamic experiments. The buildup concentrations of short-lived radionuclides, produced by activation in the reactor core water and the amounts of radionuclides sorbed on the resin bed, as estimated from a compartment model, are reported. A method for estimating the production rate of soluble radionuclides with long half-lives in the core water has been developed. Changes in the radiation dose rates along the resin column length recorded during reactor operation and after shut-down, showed that the sorbed radionuclides did not migrate downward, as expected from the chromatography theory, rather they were decreased by the decay process. Moreover, the slopes of the dose rates on both sides of the resin surface were almost identical. These results show the behavior and distribution of radionuclides in the light water moderator of a research reactor.     

Annals of the ICRP. A report of: doses to infants from ingestion of radionuclides in mothers' milk

In the present report, ICRP provides information on radiation doses to the infant due to intakes of radionuclides in maternal milk. As in Publication 88 (ICRP, 2001) on doses to the embryo and fetus following intakes of radionuclides by the mother, intakes by female members of the public and female workers are addressed. Acute and chronic intakes are considered at various times before and during pregnancy as well as during the period of breastfeeding. Dose coefficients per unit intake by the mother (Sv/Bq) are given for the selected radionuclides of the same 31 elements for which age-specific biokinetic models were given in Publications 56, 67, 69, and 71 (ICRP, 1989, 1993, 1995a,b). For these elements, doses were calculated for the most radiologically significant natural or artificial radionuclides that might be released into the environment due to various human activities. Dose coefficients are also given in this report for radionuclides of an additional four elements: sodium, magnesium,phosphorus, and potassium. Relevant human and animal data on elemental and radionuclide transfer to milk are reviewed. The biokinetic models for adults given in earlier ICRP publications are adapted to include transfer to milk. Model predictions of fractional transfer of ingested or inhaled activity to milk are discussed in the report, and the corresponding dose coefficients for the infant are compared with dose coefficients for in utero exposure, as given in Publication 88 (ICRP, 2001). Illustrative information is also given on doses to the female breast from radionuclides in breastmilk, and external doses received by the child from radionuclides retained in the tissues of the mother. For the additional elements considered in this report, but not in Publication 88 (ICRP,2001), information is also given on doses to the embryo and fetus following maternal intakes of radioisotopes during or before pregnancy. A CD-ROM is to be issued giving data that will supplement the information given in this report. In addition to the dose coefficients given here, committed equivalent doses to the various organs and tissues of the offspring will be given. Dose coefficients will also be given for inhalation of a range of aerosol sizes for the selected radionuclides of the elements covered by this report.     

Mathematical Simulation and Analysis of the Behavior of Radionuclides in the System Krasnoyarsk Integrated Mining and Chemical Plant–Enisei–Kara Sea

The equations describing the transport of radionuclides in a system consisting of river water with a suspension and bottom deposits, taking account of the influx of radionuclides with the discharges from the plant and runoff from the basin area, are formulated. The coefficients in the equations are determined by analyzing the data from measurements. On this basis, the flood-plain deposits are dated and the time dependence of the radionuclide discharges over the entire period of operation of plant is determined and the concentration in water and bottom deposits is calculated. The balances between the discharge, the runoff from the basin area, and influx into the bottom deposits, the floodplain, and the Kara Sea are constructed for the past. A procedure is developed for estimating the outflow of mobile forms of radionuclides from the bottom deposits after a sharp decrease of discharges in 1992. The rate of self-purification of the river basin in the future is estimated taking account of this effect and the redistribution of radionuclides between the bottom and flood-plain deposits.     

Isolation and identification of bacteria able to form biofilms from deep subsurface environments

Migration radionuclides in an underground environment are one of the major concerns in the safety assessment of a geological repository. Biofilms can have an impact on the transport of radionuclides in several ways: (1) by acting as a barrier to radionuclide sorption onto geological surfaces, or (2) by providing a sorption site for radionuclides, or (3) by trapping many things, including radionuclides. Little is known about bacterial effects on the biofilm formation deep underground. In this study, we isolated bacterial strains from deep groundwater and evaluated the biofilm formation abilities of these strains by crystal violet assay. Bacterial strains were isolated from ground-water collected at –140 m in the 07-V140-M01 borehole at the Horonobe Underground Research Center, Japan. The crystal violet assay showed that 98% of the isolated strains had biofilm formation abilities under tested conditions. This result suggested that biofilm formation must not be neglected in the study of migration radionuclides in nuclear waste repositories. The isolated strains produced differential amounts of biofilm, although they were identified as the same Pseudomonas species, suggesting that biofilm formation abilities varied at different strain levels. These results support the conclusion that the assessment of biofilm impact on the transport of radionuclides in a geological repository must consider the variation in biofilm formation as a function of strain level.     

Handling of the Bottom Residues of a Nuclear Power Plant

The following technological operations are suggested for reprocessing bottom residues from nuclear power plants: separation of radionuclides using oxidation, filtration, and selective absorption, solidification and long-term storage of secondary radioactive wastes (cement compound from filtration stage and spent sorbent in filters); concentration and obtaining dry salts from bottom residues from which radionuclides have been removed. Laboratory and stand tests have been performed, showing that radionuclides can be removed from the bottom residues of nuclear power plants to a level below the ASA_sat according to NRB-96. This treatment decreases the volume of radioactive wastes by approximately a factor of 100. The dried purified bottom residues, which are commercial danger class III wastes, are shipped to storage sites used for industrial wastes. Calculations of the material flows are performed and the site arrangement of the wastes is given for the bottom residues from the Kursk nuclear power plant. 1 figure, 2 tables, 12 references.     

Radiation Monitoring of Objects in the Environment Using γ Rays from Samples

A method is described for determining the specific activity of a mixture of radionuclides and individual radionuclides in environmental objects on the basis of radiation emitted by samples. This method is suitable for different geometries for measuring the -ray dose rate of the sample and different compositions of the radionuclide mixture in a sample. The conversion factor from the exposure dose rate to the specific activity of radionuclides is determined using a representative sample in which the composition and contribution of radionuclides are determined using spectrometric and radiochemical analyses. 1 table, 2 references.     

Reconstruction of the background spectrum for processing airborne gamma survey data

The reconstruction of the background spectrum is based on a decomposition of the initial spectrum into components which are due to the radiation from naturally occurring radionuclides on the Earth’s surface, cosmic rays, and radiation from the spectrometer itself. For the spectra of the naturally occurring radionuclides, the response functions of the detector are calculated for ²³⁸U, ²³²Th, and ⁴⁰ K in the soil; the instrumental and cosmic-ray background is determined by means of aircraft flights at a large altitude. The method has been tested under real conditions and has given satisfactory results for the evaluation of the soil content of naturally occurring radionuclides and ¹³⁷Cs from global fallout. The method will increase considerably the sensitivity and accuracy of the aerial gamma-ray surveys for the detection of technogenic sources of radiation, whose activity is comparable to that of naturally occurring radionuclides and which have no distinct isolated photopeaks in the observed spectrum.     

Long-term prediction of the migration of radionuclides from solid radwaste storage sites at the Siberian Chemical Works

The results of a calculation of the migration of radionuclides from a repository for solid radioactive wastes from the reactor plant of the Siberian Chemical Works, performed using a method recommended by IAEA with the AMBER 4.4 computer program and by finding an analytical solution, are presented. Three scenarios for migration of radionuclides from the repository are described and estimates of their specific activity in the uppermost water layer and the results on an analysis of the sensitivity of models to a change in the input parameters are presented. __________ Translated from Atomnaya énergiya, Vol. 103, No. 2, pp. 134–136, August, 2007.     

Spectrometry analysis based on approximation coefficients and deep belief networks

A method of spectrometry analysis based on approximation coefficients and deep belief networks was developed. Detection rate and accurate radionuclide identification distance were used to evaluate the performance of the proposed method in identifying radionuclides. Experimental results show that identification performance was not affected by detection time, number of radionuclides, or detection distance when the minimum detectable activity of a single radionuclide was satisfied. Moreover, the proposed method could accurately predict isotopic compositions from the spectra of moving radionuclides. Thus, the designed method can be used for radiation monitoring instruments that identify radionuclides.     

Fission Products and Actinides in Spent Graphite Masonry of the Reactors at the Siberian Chemical Combine

The characteristic feature of the investigations performed was the wide-scale and representative selection of samples of graphite masonry from reactors and the comprehensive analysis of their radioactive contamination. An analysis of a large number of samples made it possible to construct a detailed picture of the contamination. The role of incidents in the formation of the contamination of graphite by individual radionuclides was determined. The distribution of the radionuclides in the masonry was studied. Correlations between the content of different radionuclides were investigated.Schemes for estimating the store of radionuclides in graphite masonry were constructed on the basis of the distribution of the radionuclides of different origin. In the approximate schemes the masonry was represented as a collection of cells. The store of a radionuclide was determined by summing its content in individual cells, which were divided into several categories according to their degree of contamination.The estimates of the store of radionuclides in the masonry differed strongly from the predicted values. The store of fission products and actinides was approximately ten times smaller than previously assumed; this could substantially simplify the disassembly and choice of utilization technology. 2 figures, 10 tables, 3 references.     

微生物还原放射性核素研究进展

微生物还原放射性核素的研究近年来得到了较为广泛的关注,因为这种生物转化作用将在修复受放射性核素污染环境方面发挥重要作用.本文重点介绍了利用微生物还原作用治理放射性核素污染方面的最新研究进展,主要包括U(Ⅵ)、Np(Ⅴ)和Tc(Ⅶ)的微生物还原;讨论了微生物还原放射性核素的可能作用机理;评价了这种生物转化作用对环境的影响以及在受污染环境的生物修复中的可能应用.     

核素在非饱和黄土介质中的二维迁移

试验结果表明，天然降水条件下，在近3年的试验期间，^60Co,^85Sr和^134Cs三种核素在非饱和黄土介质中的比活度分布质心仍在示中源层这内，^85Sr的侧向比活度分布方差与纵向比活度分布方差相当；在人工喷淋条件下，这些核素的迁移距离也很短，说明非饱和黄土对这些核素有较强的吸附滞留能力。或者换句话说，非饱和黄土可以作为中低放废物处置的候选地质介质。另外，根据对试验结果的拟合与分析看出，降水入渗量极大地影响着核素向下的迁移速度和纵向扩展，因此，控制流经处置库的入渗水量，是减少处置废物中放射性核素对环境影响的重要因素。     

纳米零价铁材料对放射性核素的 去除及机理研究进展

随着人类社会的发展，放射性铀矿的开采和使用越来越多，环境面临着越来越严重的放射性污染问题。从生物和环境的角度来看，有效地清除环境中的放射性核素是核能利用过程中最重要的问题之一。纳米零价铁（nanoscale zero valent iron, nZVI）具有较大的比表面积和较高的活性位点，能显著提高放射性污染物的修复效率。本综述的目的是展示nZVI基材料对放射性核素的高效去除能力和环境修复作用。简介了常用的nZVI基材料（表面改性或多孔材料支撑的nZVI材料）及其对放射性核素的去除效果和相互作用机制（如吸附和氧化还原）。最后，对nZVI材料的应用和挑战给出个人见解。本综述有助于为高效去除放射性核素的nZVI材料的设计指明方向，为放射性核素的高效处理处置提供新材料。     

纳米零价铁材料对放射性核素的去除及机理研究进展

随着人类社会的发展，放射性铀矿的开采和使用越来越多，环境面临着越来越严重的放射性污染问题。从生物和环境的角度来看，有效地清除环境中的放射性核素是核能利用过程中最重要的问题之一。纳米零价铁（nanoscale zero valent iron, nZVI）具有较大的比表面积和较高的活性位点，能显著提高放射性污染物的修复效率。本综述的目的是展示nZVI基材料对放射性核素的高效去除能力和环境修复作用。简介了常用的nZVI基材料（表面改性或多孔材料支撑的nZVI材料）及其对放射性核素的去除效果和相互作用机制（如吸附和氧化还原）。最后，对nZVI材料的应用和挑战给出个人见解。本综述有助于为高效去除放射性核素的nZVI材料的设计指明方向，为放射性核素的高效处理处置提供新材料。     

船用反应堆大破口失水事故封闭环境核素扩散研究

基于严重事故分析程序MELCOR耦合计算流体力学软件CFD-FLUENT研究方法,采用MELCOR对船用反应堆失水事故进行分析,结果作为CFD-FLUENT模拟实验的初始条件,对船用反应堆大破口严重失水事故在堆舱内的放射性核素扩散进行研究。研究结果表明,泄漏时间在45 min时,放射性核素扩散至冷却剂进口、出口位置,而在14 min时放射性核素已经开始向安全壳扩散;在51 min时,放射性核素开始从安全壳破口向安全壳外扩散;在87 min时,放射性核素开始向邻舱扩散。本研究计算结果可为核事故的应急决策提供理论支持和数据支撑。      

Monitoring the volume activity of nuclides in air during rehabilitation of the site of old storage facilities at the Russian Science Center Kurchatov Institute

This article is devoted to the monitoring of the volume activity of radionuclides, performed in 2003–2006 as part of the unified project Reabilitatsiya, during liquidation of old storage sites for radioactive wastes at a special site of the Russian Science Center Kurchatov Institute. Methods for dust suppression of radionuclides, means for monitoring the volume activity of aerosols, and methods for organizing such monitoring are described. The concentrations of individual radionuclides in air and the wind-erosion coefficients are presented, and the monitoring results obtained are discussed. __________ Translated from Atomnaya énergiya, Vol. 108, No. 1, pp. 37–43, January, 2008.     

Determination of the Admissable Technogenic Radioactive Contamination of Water in Bays during the Operation of Nuclear Objects in Marine Engineering

The various irradiation pathways due to radioactive contamination of water in bays (estuaries) are analyzed and the dose factors, characterizing the irradiation pathways considered, are determined for an extensive set of radionuclides. A method is proposed for determining the control concentration of radionuclides in water in reservoirs using the above-mentioned dose factors. The method is based on taking account of the professional work performed by workers. Critical population groups are identified on the basis of the irradiation pathways considered, and estimates of the control concentration of radionuclides in the water of a bay are made for these groups. 2 tables, 6 references.     

Calculation of risk-based detection limits for radionuclides in the liquid effluents from Korean nuclear power plants

In order to review if present detection limits of radionuclides in liquid effluent from nuclear power plants are effective enough to warrant compliance with regulatory discharge limits, a risk-based approach is developed to derive a new detection limit for each radionuclide based on radiological criteria. Equations and adjustment factors are also proposed to discriminate the validity of the detection limits for multiple radionuclides in the liquid effluent with or without consideration of the nuclide composition. From case studies to three nuclear power plants in Korea with actual operation data from 2006 to 2015, the present detection limits have turned out to be effective for Hanul Unit 1 but may not be sensitive enough for Kori Unit 1 (8 out of 14 radionuclides) and Wolsong Unit 1 (9 out of 42 radionuclides). However, it is shown that the present detection limits for the latter two nuclear power plants can be justified, if credit is given to the radionuclide composition. Otherwise, consideration should be given to adjustment of the present detection limits. The risk-based approach of this study can be used to determine the validity of established detection limits of a specific nuclear power plant.     

Measurement of cross-sections for the (p, xn) reactions in natural molybdenum

Cross-sections for the residual radionuclide productions by proton-induced activation on natural molybdenum were measured up to 40 MeV by using a stacked-foil technique at the MC50 cyclotron of the Korea Institute of Radiological and Medical Sciences (KIRAMS). This work has given a new data set for the formation of the investigated radionuclides. The present results for most of the radionuclides showed in general good agreement with the earlier reported data as well as the theoretical data taken from the calculations based on the ALICE-IPPE code. The integral yields for thick targets were also deduced from the measured cross-sections of the produced radionuclides. The optimum production of the ^99mTc radionuclide with minimum impurities can be obtained at the energy ranges from 10 to 23 MeV, where the production yields were obtained as 597.15 MBqμA⁻¹h⁻¹ at saturation. The measured cross-sections are used for production of medically important radionuclides such as ^99mTc, ^94mTc and ^93m,gTc by using the medium-energy cyclotrons.     

Radioactive contamination of a site in kiev oblast on april 30, 1986

Data are presented on the level of contamination of a site in a surveyed part of Kiev Oblast on the fourth day after an accident in which radionuclides were discharged from a damaged reactor. It is shown that the contamination on the observation date was much weaker than after discharges were completed by mid-May 1986. The fraction factors of the radionuclides during discharge from the damaged reactor and atmospheric transport to the point of observation of the site contamination are calculated.