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There has been increasing evidence in recent years about the impact of soil structure on vadose zone hydrology and the distribution of surface applied chemical substances. We have carried out a combined dye and radionuclide tracer study on two monoliths from the same location, one structured and one repacked, as part of an ongoing study to investigate the link between preferential flow, leaching of surface applied substances and their distribution within the soil.A tracer solution containing 1300 Bq/L (58)Co and 0.31 micromol/L Sulforhodamine B (SB) was added with roughly constant irrigation during a period of three weeks. The dye served as a tracer for water movement within the soil and thus allowed linkage of the radiotracer ((58)Co) with the flow pattern. Both were monitored in the outflow and measured within profile sections after monolith disassembly. Preferential flow in the structured monolith promoted the bypass and transport of both tracers, although transport was impeded at depths greater than 30 cm by compacted soil and reduced hydraulic conductivity. Eighty four percent of radiocobalt and 8% of SB were found in the upper 4 cm of the structured monolith. The homogenized monolith, on the other hand, showed mostly chromatographic infiltration and a more efficient soil filtering capacity with 91% of radiocobalt and 20% SB residing in the upper 4 cm. Furthermore no tracer was found in the outflow of the homogenized monolith during normal to high irrigation or at greater depth within the monolith. We have related flow characteristics and sorption of radiotracers by quantifying dye distributions and radionuclide activities throughout the profiles. Activities within the flow paths are up to 20-times higher than those measured in the soil matrix, and a fraction of radiocobalt follows the dye tracer in spite of cobalt's low mobility. The dye can thus be used to trace radionuclide distribution within the soil block.

A benchmark set of measured beta particle spectra for a standardised 60Co hot particle source is presented. The spectra were obtained for conditions similar to those encountered in practical dosimetric applications. The measured spectra were compared with Monte Carlo calculations using the MCNP code. These comparisons provided information to guide the selection of the optimal set-up parameters of the code. Important differences were observed in the MCNP calculated spectra when ITS and the default indexing style algorithm were used. Overall the calculations using the default mode of MCNP version 4B provide the best agreement with the measured electron spectra.

A signal current from a cylindrical ionisation chamber with an ionisation volume of 62.7 cm3, 40 mm in diameter and 50 mm long, peaked when the chamber was lixed at 0 degrees and at 90 degrees in 137Cs and 60Co gamma ray fields for source-chamber distances of 1 m and 2 m. A smaller ionisation chamber showed a small peak at 0 degrees in both fields but not at 90 degrees. However, calculations indicated that the signal current from the smaller chamber would also show a peak at 90 degrees in a 137Cs point-source gamma ray field. Peaks occur because gamma rays attenuate along the cylindrical side wall or along the end walls when a chamber is tilted slightly from 0 degrees or 90 degrees and the direction of the gamma ray beam agrees with the plane of one of these walls. These facts suggest the need for care in the common practice of measuring and calculating responses for cylindrical ionisation chambers fixed perpendicular to gamma ray beams.

Chang-hua Christian Hospital needs to uninstall the 60Co unit. The mode of this 60Co teletherapy unit is SHIMADZU RTGS-10. The original lead head was taken as the source container of this 60Co unit. The source head was dismantled and put into the prepared wooden box, after the source was sealed. This study describes the planning and dismantling of the retirement and transport of the 60Co unit, and personal doses measured during the procedure. This work estimates the doses of radiation received by exposed workers during the dismantling of the machine. The workers received doses of approximately 53 microSv. This study shows that the original lead head can be used as the source container of this 60Co unit. The 60Co machine was smoothly dismantled and transported by conscientious and careful workers, using planned and controlled radiation protection, following the ALARA (as low as reasonably achievable) rule.

Risk assessment of intentional or accidental discharges of toxic substances into river systems requires combined hydraulic and chemical modeling. Periodic discharges of known volumes with low radioactivity by the Beznau nuclear reactor (Switzerland) serve as validation tracers for both river flow and chemical speciation simulation. Validation of the former has been achieved by comparison of modeled and measured arrival times of radiocobalt along a 65 km transect with a maximum reaction period of 24 hours. Modeled breakthrough curves coincide well with measurements collected during three field campaigns, in spite of the fact that sorption and sedimentation processes were not activated during simulation. This gives indirect evidence of inefficient cobalt sorption. Particle/solution distribution measurements carried out during breakthrough allow further validation of our speciation approach, which is based on Tableau setup of inorganic reactions combined with sorption and organic complexation. Modeled and measured speciation results confirm recent observations of enhanced complexation of cobalt with dissolved organic substances, which significantly reduces particle sorption. The large variability of conditional stability constants for sorption and complexation reactions, for sorption site densities, and for organic ligand concentrations explains the variability of published particle-solution distribution coefficients.

Three contaminated housing units, yielding annual dose levels of 6, 22 and 57 mSv, were selected randomly from identified radiation contaminated buildings (RCBs) to perform this experiment. The results are presented of a study to investigate the probability of finding RCBs by using eight thermoluminescence dosemeters (TLDs) for each suspected radiation contaminated housing unit. The results revealed that, for these three housing units, the probabilities of detecting contaminated housing units using eight TLDs were 93%, 86% and 99%, respectively. The number of TLDs required for such a determination depended strongly on both the radiation contaminated level (i.e., the activity) in the housing unit and the distribution of contaminated columns and beams in the house.

The energy response of standard (TLD-100) and high-sensitivity (TLD-100H) LiF thermoluminescence dosemeters (TLDs) has been studied for photon beams with mean energies from about 25 keV to 1100 keV. Canadian primary standards for air kerma were used to establish the air kerma rates for each of the photon beams. TLDs were mounted in a PMMA holder and the air kerma response was measured as a function of energy. The EGSnrc Monte Carlo code was used to model the TLD holder and calculate the absorbed dose to the TLD chip per unit air kerma for each beam. The measured and calculated results were combined to obtain the intrinsic dose response of the TLD chip. Broadly, our results are consistent with existing data, which show a marked difference in the energy dependence of the two materials. However, the precision of our measurements (standard uncertainty of about 0.6%) has permitted the identification of features that have not been noted before. In particular, the energy dependence of the two materials is quite different in the important energy region delimited by 137Cs and 60Co gamma rays.

Residual 60Co activity in five steel samples induced by neutrons from the Nagasaki atomic bomb has been measured within about 1000 m from the hypocenter. The chemical separation of cobalt and nickel from steel samples was performed, and cobalt-enriched samples were prepared for all samples. Gamma-ray measurements were carried out with a low-background well-type germanium detector. The gamma-ray spectra for five samples were compared with the spectrum of a control sample to ensure that the observed 60Co was actually induced by A-bomb neutrons. The activation of cobalt by environmental neutrons was also investigated. It has been shown that the present 60Co data are consistent with earlier Hashizume's data.

The first 60Co-contaminated rebar building was found in Taipei City in 1992. In order to provide effective remedial suggestions to the building owner and residents of contaminated housing units, and to evaluate the dose equivalent to the residents, the Atomic Energy Council (AEC) organized a survey team on October 17, 1992. The main object of this team was to perform a detailed survey and dose equivalent evaluation of the 60Co-contaminated buildings. By the end of 2000, 181 buildings with 1607 housing units were identified as being contaminated with radioactive rebars at different levels. This article presents the detailed radiation survey and dose equivalent evaluation procedures employed by the survey team.

Twenty years of environmental monitoring data around the Swedish nuclear power plants and the Studsvik research facilities have been evaluated. In the marine environment, Fucus vesiculosus generally has high activity concentrations and the presence of a large variety of radionuclides in comparison with other bioindicators. However, for single nuclides the detection frequency was higher for 110mAg in Littorina spp and for 152Eu in Macoma baltica in comparison with other bioindicators. Close to the discharge point the activity concentration of 60Co in F. vesiculosus and in the discharge water were correlated. In the terrestrial environment, few radionuclides were detected and the activity concentrations were generally low. Of the terrestrial indicators, mosses had the highest activity concentrations and also comprised the largest variety of radionuclides. The radiation doses to humans based on measurements of released activity were small. Based on the results from the evaluation, alternative sampling strategies for the monitoring program are discussed.

The activities of 137Cs, 60Co and 40K were determined in samples of wild (Taraxacum officinale, Plantago lanceolata and Populus nigra 'Italica') and edible (vegetable, corn, fruit) plants as well as soil collected from the 30 km safety zone of the Bulgarian NPP "Kozloduy" and comparisons with earlier measurements and analyses of samples from other regions and with literature values were performed. The derived transfer factors for 137Cs and 40K from soil to plants ranged between 0.002 and 0.009 for 137Cs, and between 0.09 and 0.35 for 40K. The individual effective dose (calculated from the present results and data on the activity of other foodstuffs and from information about dietary habits) comprises 4.5% of the annual dose limit.

The leach test of radionuclide in cement-solidified waste form was performed. After leach test, compressive strength of waste form was measured. Cement-solidified waste form produced at Korean nuclear power plant, Kori (PWR) was chosen for the leach test. Specimens were cored out from a full-scale waste form (2001 drum size). The leach test procedure used for this study was ANSI/ANS 16.1 procedure. The leach ability indexes for cesium and cobalt isotopes were determined. Semi-infinite model was used for analysis of the controlling mechanism in the release of isotopes. Release mechanism of cesium was dominated by diffusion but release of cobalt behaved somewhat differently from the diffusion controlled release. Averaged leachability indexes were 8.6 for cesium and 11.4 for cobalt. Compressive strength after leach/ immersion test was 7.34 MPa for the sample immersed in simulated seawater and 8.34MPa for the sample immersed in deionized water.

One of the input ways of radionucleids into the organism is through food intake. The aim of the present study is to measure the radioactivity levels in food and water samples within energy windows corresponding to 137Cs, 125I, 131I, 59Fe, and 57Co. Samples were taken from local and imported food belonging to the venezuelan basic alimentary basket and included: beef meat, hen egg, chicken bone, tomato, black bean, rice, powder milk from local dealers or imported from Italy and New Zeeland, potable water from the Valencia city aqueduct and bottled water from local sources or imported from Portugal. Radioactivity was measured with a well type Nal (TI) scintillation counter. Analyzed foods and water presented levels lower than the minimal detectable activity for 137Cs, 131I, 59Fe, 57Co, but it was detected in the Valencia city aqueduct water and in bottled water imported from Portugal, levels greater than the minimal detectable activity for the 125I energy window. These results strongly suggest the need of repeated multienergy windows monitoring of radioactivity of basic alimentary basket foods and potable water.

Since the beginning of the 1990s the exploration of optically stimulated luminescence (OSL) in retrospective accident dosimetry has driven an intensive investigation and development programme at Risø into measurement facilities and techniques. This paper reviews some of the outcomes of this programme, including the evaluation of the single-aliquot regenerative-dose (SAR) measurement protocol with brick quartz and the determination of dose-depth profiles in building materials as a guide to determining the mean energy of the incident radiation. Investigations into heated materials are most advanced, and a lower detection limit for quartz extracted from Chernobyl bricks was determined to be <10 mGy. The first results from the measurement of doses in unheated building materials such as mortar and concrete are also discussed. Both small-aliquot and single-grain techniques have been used to assess accident doses in these cement based building materials more commonly found in workplaces. Finally some results of a preliminary investigation of the OSL properties of household chemicals are discussed with reference to their potential as accident dosemeters.

The energy responses of LiF-TLDs irradiated in megavoltage electron and photon beams have been determined experimentally by many investigators over the past 35 years but the results vary considerably. General cavity theory has been used to model some of the experimental findings but the predictions of these cavity theories differ from each other and from measurements by more than 13%. Recently, two groups or investigators using Monte Carlo simulations and careful experimental techniques showed that the energy response of 1 mm or 2 mm thick LiF-TLD irradiated by megavoltage photon and electron beams is not more than 5% less than unity for low-Z phantom materials like water or Perspex. However, when the depth of irradiation is significantly different from dmax and the TLD size is more than 5 mm, then the energy response is up to 12% less than unity for incident electron beams. Monte Carlo simulations of some of the experiments reported in the literature showed that some of the contradictory experimental results are reproducible with Monte Carlo simulations. Monte Carlo simulations show that the energy response of LiF-TLDs depends on the size of detector used in electron beams, the depth of irradiation and the incident electron energy. Other differences can be attributed to absolute dose determination and precision of the TL technique. Monte Carlo simulations have also been used to evaluate some of the published general cavity theories. The results show that some of the parameters used to evaluate Burlin's general cavity theory are wrong by factor of 3. Despite this, the estimation of the energy response for most clinical situations using Burlin's cavity equation agrees with Monte Carlo simulations within 1%.

During the JCO-accident in Tokai-mura in 1999, the surrounding village was irradiated by an uncontrolled neutron flux. At some locations in that village, the thermal neutron flux was determined retrospectively by measurement of the very low activity of 51Cr and 60Co in stainless-steel spoons using gamma-ray spectrometry in underground laboratories. Activities determined in the HADES underground facility are presented here, together with calibrations performed using a well-defined thermal neutron flux to directly estimate the fluence of thermal neutrons independent of most assumptions. The results show measurable 51Cr in three samples and 60Co in four samples taken from locations at distances of up to 430m from the accident location despite the elapse of 4 half-lives of 51Cr before measurement. Effects of air transport of the samples were considered and shown to be negligible.

A computer routine was developed for automatic deconvolution of electron paramagnetic resonance spectra of tooth enamel samples for individual radiation dose reconstruction in the low dose region. The deconvolution routine uses the non-linear least square fit of a model simulating a tooth enamel spectrum by superposition of derivative Gaussian functions to obtain the amplitude of the dosimetric radiation induced signal. The parameters of the model and of the routine were optimized on a dose response level using a criterion of the least standard deviation of the derived radiation induced signal amplitude from the regression line vs. the nominal doses for the series of spectra of samples irradiated in known doses in the range 0-500 mGy. It was found that for the series of spectra of the heterogeneous samples (every sample is prepared from different teeth of different persons), it is essential to vary in the least square fit the parameters describing the shape of the native background signal in order to obtain the best accuracy. In the case of the series of spectra of the homogeneous (pooled) samples, almost the same accuracy of the results was obtained using the procedures with varied and fixed background signal parameters. The standard error of the dose reconstruction by the optimized deconvolution procedure was estimated as about 30 mGy for heterogeneous samples and 20 mGy for homogeneous samples.

This paper summarizes the vertical distributions of 22Na, 137Cs, and 60Co above controlled water tables in deep and shallow lysimeters during a four-year experiment. The activity concentration profiles were all determined at the time of harvest of a winter wheat (Triticum aestivum L. cv. Pastiche) crop. Activity concentrations in different crop tissues were determined and crop uptake expressed as both an inventory ratio (IR) and a transfer factor (TFw), weighted to account for root and radionuclide distributions within the soil profile. Experimental variates were subjected to analysis of variance to determine the single and combined effects of the soil depth and the year of the experiment on the results obtained. Each radionuclide showed significant variations in activity concentration with soil depth, but the significance of these variations from year to year was dependent on radionuclide. A distinction in the behavior of weakly sorbed (22Na) and more highly sorbed (137Cs and 60Co) radionuclides was observed. The former exhibited significant variations in its distribution in the soil profile from year-to-year whereas the latter did not. Relatively high TF, values for 22Na were maintained throughout the experiment, whereas for 137Cs and 60Co, the highest TFw values were recorded in 1990 followed by a significant decline in 1991, with TFw remaining low in 1992 and 1993. The TFw values were, in general, significantly higher for deep lysimeters than for shallow lysimeters. This is thought to provide evidence of enhanced radionuclide absorption by the relatively small fraction of roots in the vicinity of the deeper water table.

The linear and mass attenuation coefficients of different types of soil, sand, building materials and heavy beach mineral samples from the Chittagong and Cox's Bazar area of Bangladesh were measured using a high-resolution HPGe detector and the gamma-ray energies 276.1, 302.8, 356.0, 383.8, 661.6 and 1173.2 and 1332.5 keV emitted from point sources of 133Ba, 137Cs and 60Co, respectively. The linear attenuation coefficients show a linear relationship with the corresponding densities of the samples studied. The variations of the mass attenuation coefficient with gamma-ray energy were exponential in nature. The measured mass attenuation coefficient values were compared with measurements made in other countries for similar kinds of materials. The values are in good agreement with each other in most cases.

Two types of radioactive particle were identified in marine sediment and lichen samples collected from the Kola Bay, NW Russia. The particles were identified by means of gamma-ray spectrometry and autoradiography, separated and subjected to various analysis techniques. Several complementary techniques are needed to characterise particle properties thoroughly. 137Cs was present in the sediment matrix in large (approximately 100 microns) greenish particles that were most probably pieces of paint. Although their element composition was heterogeneous, 137Cs was found to be evenly distributed. 60Co in the lichen matrix was present in small (approximately 1 micron) particles. No U or transuranium elements were detected in either type of particle.

The behaviour of radionuclides discharged from nuclear facilities in the Rhône River depends on their distribution among the dissolved, colloidal and particulate phases. A large water sample was fractionated using sequential ultrafiltration. Size distributions of organic carbon, Fe, Al, Si, Ca, Mg, Cu, Zn, 137Cs, 60Co and 106Ru were obtained. Our results show that organic colloids account for 11% of the total organic carbon content. Approximately 20% of the dissolved (< 450 nm) Fe and Al are in colloidal classes. 137Cs is not significantly transferred by the colloidal phase while 25% of 60Co or 106Ru is associated with organic and inorganic colloids.

To assess the impact of radionuclides entering the marine environment from dumped nuclear waste, information on the physico-chemical forms of radionuclides and their mobility in seawater-sediment systems is essential. Due to interactions with sediment components, sediments may act as a sink, reducing the mobility of radionuclides in seawater. Due to remobilisation, however, contaminated sediments may also act as a potential source of radionuclides to the water phase. In the present work, time-dependent interactions of low molecular mass (LMM, i.e. species < 10 kDa) radionuclides with sediments from the Stepovogo Fjord, Novaya Zemlya and their influence on the distribution coefficients (Kd values) have been studied in tracer experiments using 109Cd2+ and 60Co2+ as gamma tracers. Sorption of the LMM tracers occurred rapidly and the estimated equilibrium Kd(eq)-values for 109Cd and 60Co were 500 and 20000 ml/g, respectively. Remobilisation of 109Cd and 60Co from contaminated sediment fractions as a function of contact time was studied using sequential extraction procedures. Due to redistribution, the reversibly bound fraction of the gamma tracers decreased with time, while the irreversibly (or slowly reversibly) associated fraction of the gamma tracers increased. Two different three-compartment models, one consecutive and one parallel, were applied to describe the time-dependent interaction of the LMM tracers with operationally defined reversible and irreversible (or slowly reversible) sediment fractions. The interactions between these fractions were described using first order differential equations. By fitting the models to the experimental data, apparent rate constants were obtained using numerical optimisation software. The model optimisations showed that the interactions of LMM 60Co were well described by the consecutive model, while the parallel model was more suitable to describe the interactions of LMM 109Cd with the sediments, when the squared sum of residuals were compared. The rate of sorption of the irreversibly (or slowly reversibly) associated fraction was greater than the rate of desorption of the reversibly bound fractions (i.e. k3 > k2) for both radionuclides. Thus, the Novaya Zemlya sediment are supposed to act as a sink for the radionuclides under oxic conditions, and transport to the water phase should mainly be attributed to resuspended particles.

A standardized procedure is proposed to obtain from laboratory experiments the kinetic accumulation and release rates necessary to calibrate dynamic models to quantify radionuclide direct and trophic transfer in fish. The model takes into account the food-chain effect, the feeding rate, and the growth of organisms. It takes as examples (54)Mn, (60)Co, and (137)Cs transfer dynamics through a simple pelagic food-chain (phytoplankton, zooplankton, prey fish, and predator fish). The estimated kinetic rates used in quantifying all the transfers of the three radioactive pollutants through the pelagic food chain are compared from the radioecological point of view. For fish, comparison was based on the calculation of concentration factors referring to direct transfer from water and trophic transfer factors. For the prey fish and the predator fish, direct transfer gave the following order for accumulation (60)Co < (137)Cs < (54)Mn. Values reached at equilibrium in L/kg WW were respectively for the prey fish and the predator fish: 8.7 < 27.4 < 107 and 4.14 < 6.59 < 13.4. For the trophic route, (137)Cs is the most accumulated (TTF(eq) = 0.485 in 291 days for the prey fish and TTF(eq) = 1.45 in 17 years for the predator fish). A sensitivity analysis adapted to the case of a chronic contamination scenario of a watercourse was run. It showed that the phytoplankton biomass, the contact time of these drifting particles from a release point to the station where they are ingested and the feeding rates of the fish are the most influential parameter with regard to the concentration in fish, whatever the trophic level. Contamination charts are constructed for the predator fish to illustrate the relationship between the most influential ecological parameters and the radionuclide concentration in fish for simple contamination scenarios. They are shown to be effective tools for helping in the choice of the most relevant value of aggregated concentration factors (ACFs: radionuclide concentration ratio between the organism and the water, referred to steady-state and to all possible transfer pathways) for a given key ecological situation in a given ecosystem. An example is given of a simple chronic release scenario of 1 Bq/L and a phytoplanktonic bloom period. For (137)Cs, the ACF increases with increasing contact time and increasing feeding rate, to nearly 550 L/kg WW at equilibrium. For (54)Mn, ACF reaches 65 L/kg WW. For (60)Co, the general pattern of the relationship is due to the rapid kinetic rates governing the distribution of the radionuclide between dissolved and solid (phytoplankton) phases with a maximum value for ACF of 7.2 L/kg WW for the case study. Analysis of these charts provides a basis for overall guidelines for chronic releases in a given watercourse.

Baseline values of concentrations of the natural radionuclides (238U, 226Ra, 228Ra/232Th, 210Pb) and artificial radionuclides (137Cs, 60Co) in food and drinks (tap water, milk, and water-based drinks) were determined by gamma spectroscopy. All food and drinks were found to contain detectable 40K contents: 0.1 to 160 Bq kg(-1) (fresh mass) for food and 0.006 to 61 Bq L(-1) for drinks. Most of the other natural radionuclides in solid food were found to have contents below the minimum detectable activities (MDA). More samples in the leafy vegetable, tomato, carrot and potato categories contained detectable amounts of 228Ra than the meat, cereal, and fish categories, with concentrations up to 1.2 Bq kg(-1) for the former categories and 0.35 Bq kg(-1) for the latter categories. The 238U and 226Ra radionuclides were detectable in most of the water-based drink samples (reaching 0.22 and 0.015 Bq kg(-1), respectively), and the 228Ra and 210Pb radionuclides were detectable in fewer water-based drink samples. The 137Cs contents in solid food were detectable in most of the solid food samples (reaching 0.59 Bq kg(-1)), but in drinks the 137Cs contents were very low (the maximum value is 0.23 Bq L(-1)) and normally lower than the MDA values. Nearly all the 60Co contents in food and drinks were below the MDA values and their contents were below those of 137Cs. The results indicate that drinks provide higher intake of natural radionuclides than solid food, but the solid food provides higher intake of 137Cs than drinks. From the measured concentrations, estimates were made on the consumption rate of radionuclides from food and drinks. The health effects due to the ingestion of the radionuclides were evaluated by calculating the committed effective dose. The committed effective dose due to the ingestion of natural radionuclides was estimated to be 69 microSv and 280 microSv for an adult male and female, respectively. The committed effective dose due to the ingestion of 137Cs and 60Co was estimated to be 0.5 microSv for both an adult male and female. The contributions from these two artificial radionuclides were less than those from the natural radionuclides by a factor of more than 100 and were also below the 1 mSv limit set in the new ICRP recommendations.

The chi-square statistic has many scientific applications, including the evaluation of variance in counting data and the proper functioning of a radiation counting system. This paper provides a discussion of the fundamental aspects of the chi-square test using counting data. Practical applications of the chi-square statistic are discussed, including the estimation of extra-Poisson variance and dead time for a counting system. The consequences of passing or failing the chi-square test are discussed regarding the proper estimator for the population variance of the counting data. Example scenarios are used to provide insight into the applications of the chi-square statistic and the interpretation of values obtained in hypothesis testing.

As in the method for the calibration of 192Ir high-dose-rate (HDR) brachytherapy sources, the ionization chamber wall correction factor A(w), is needed for 192Ir and 60Co gamma rays and 250 kV x-rays. This factor takes into account the variation in chamber response due to the attenuation of the photon beam in the chamber wall and build-up cap and the contribution of scattered photons. Monte Carlo calculations were performed using the EGS4 code system with the PRESTA algorithm, to calculate the A(w) factor for 51 commercial ionization chambers and build-up caps exposed to the typical energy spectrum of 192Ir and 60Co gamma rays and 250 kV x-rays. The calculated A(w) correction factors for 192Ir and 60Co sources and 250 kV x-rays agree very well to within 0.1% with published experimental data (the statistical uncertainty is less than 0.1% of the calculated correction factor value). For the 192Ir sources, A(w) varies from 0.973 to 0.993 and for the 250 kV x-rays the minimum value of A(w) for all chambers studied is 0.983. The calculated A(w) correction factors can be used to calculate the air kerma calibration factor of HDR brachytherapy sources, when interpolative methods are considered, contributing to the reduction in the overall uncertainties in the calibration procedure.

Environmental radon (222Rn) monitors that incorporate electret detectors are confounded by background gamma radiation, which may cause the electret to discharge by as much as 7.5 volts per mR. Although background gamma corrections were formerly made by multiplying the known background gamma exposure rate with a constant conversion factor, this research demonstrates that doing so introduces an error ranging up to about 20%, especially in high gamma background areas. A new, more accurate method of background gamma correction has been developed that uses an average, voltage-dependent discharge factor, Dgamma (V Kg C(-1)). This factor and its coefficients were experimentally determined by separately exposing groups of electret radon detectors to photons from 60Co and 137Cs. Statistical analysis shows that Dgamma is independent of the orientation of the electret during irradiation but that some dependency on dose rate or energy of the irradiating photons may be expected. The discharge of the electret due only to gamma irradiation, Vgamma is determined by multiplying the total integrated gamma exposure by Dgamma. The discharge of the electret during a radon measurement can then be corrected for background gamma radiation by subtracting Vgamma from the total discharge of the electret resulting in a net discharge due solely to radon. A new equation has also been developed in this study for the radon discharge factor, D(Rn)(V m3 Bq(-1) s(-1)), that is entirely consistent with the gamma discharge factor and was thoroughly evaluated by exposing the electret radon detectors to known concentrations of radon.

It has recently been found that several resident and office buildings in Taiwan were constructed with 60Co-contaminated reinforcing steel bar (rebar). Both governmental officials and the residents of such buildings have been concerned about this finding. In order to respond to the situation, the government has adopted a number of remedial measures, including full-scale radiation survey, dose evaluation and physical examinations of residents. This article presents three methods for evaluating the dose equivalents of the residents living in the contaminated rebar buildings by means of gamma-ray survey, necklace-type thermoluminescence dosimeters (TLDs) and the human lymphocyte chromosome aberration analyses. The results reveal that the dose evaluation by gamma-ray survey is rather conservative. Generally for the residents whose annual dose equivalents are greater than 5 mSv (0.5 rem) by gamma-ray survey, the dose equivalents from necklace-type TLDs are only within the range of 20 to 50% of the evaluated values mentioned above. For chromosome analyses, at least 500 lymphocyte cells were scored and analyzed for each resident. Most of the chromosome analysis data show that the dose equivalents received by residents are lower than the detection limit of the method (100 mSv) and quite different from the estimated dose obtained from either gamma-ray survey or necklace-type TLD measurements.

Residual 60Co radioactivity produced by the neutrons from the Hiroshima atomic bomb has been measured by means of gamma-ray spectrometry for seven steel samples located up to 1,800 m slant range and one control sample obtained at 4.5 km from the hypocenter. After removing the main constituent of iron ions from the steel sample by the solvent extraction method, nickel and cobalt were chemically separated by the ion exchange process. Gamma-ray measurements were performed with a low background well-type germanium detector. Derived specific activities 60Co:Co were compared with previous measurements and with the calculation based on the neutron fluence of current dosimetry system DS86. It has been shown that a systematic discrepancy exists between the measured and calculated activity. The calculated-to-measured ratios for 60Co are consistent with those of 152Eu and 36Cl activity.

This paper reports on the Monte Carlo simulation of in vivo x-ray fluorescence (XRF) measurements. Our model is an improvement on previously reported simulations in that it relies on a theoretical basis for modelling Compton momentum broadening as well as detector efficiency. Furthermore, this model is an accurate simulation of experimentally detected spectra when comparisons are made in absolute counts; preceding models have generally only achieved agreement with spectra normalized to unit area. Our code is sufficiently flexible to be applied to the investigation of numerous source-excited in vivo XRF systems. Thus far the simulation has been applied to the modelling of two different systems. The first application was the investigation of various aspects of a new in vivo XRF system, the measurement of uranium in bone with 57Co in a backscatter (approximately 180 degrees) geometry. The Monte Carlo simulation was critical in assessing the potential of applying XRF to the measurement of uranium in bone. Currently the Monte Carlo code is being used to evaluate a potential means of simplifying an established in vivo XRF system, the measurement of lead in bone with 57Co in a 90 degrees geometry. The results from these simulations may demonstrate that calibration procedures can be significantly simplified and subject dose may be reduced. As well as providing an excellent tool for optimizing designs of new systems and improving existing techniques, this model can be used in the investigation of the dosimetry of various XRF systems. Our simulation allows a detailed understanding of the numerous processes involved when heavy metal concentrations are measured in vivo with XRF.

Radionuclides were added to the anoxic hypolimnion of a Canadian Shield lake to simulate the nuclear fuel waste disposal scenario where radionuclides might enter the bottom waters of a lake. The radionuclides remained in the hypolimnion until lake mixing at autumn turnover after which 60Co was rapidly lost and 134Cs was slowly lost from the water. Only 0.4% of the 60Co and 0.6% of the 134Cs remained in the water at year 5. Highest concentrations occurred in periphyton and filter feeders, Holopedium gibberum and clams (Anodonata grandis grandis). From maximum annual concentrations in clam tissues, it was estimated that the availability of 60Co for uptake had a half-time (t1/2) of 835 days in the lake, whereas that for 134Cs was 780 days. Loss rate coefficients, k, for the radionuclides from taxa ranged from 0.0008 to 0.0043 day-1 (t1/2 = 161-866 days) for 60Co and from 0.0009 to 0.005 day-1 (t1/2 = 139-770 days) for 134Cs. Cobalt-60 concentrations in forage fish were low, whereas 134Cs concentrations increased over the first year or two, then slowly declined. On the basis of k values measured for forage fish, the biological half-time of 134Cs in forage fish ranged from 428 to 630 days. Maximum 134Cs concentrations in forage fish were higher following hypolimnetic addition than epilimnetic addition. Relatively high 134Cs concentrations in periphyton at year 5 point to the importance of benthic pathways in the recycling of contaminants to higher trophic levels. The presence of 134Cs in biota 5 years after the addition, long after concentrations were no longer detectable in surface waters, is evidence of the persistence of Cs in aquatic systems. The k values (or t1/2 values) for the loss of 60Co and 134Cs from water and their uptake and loss from biota can be used to establish parameter values for assessment models. The results demonstrate that assessment models should account for the release of radionuclides from sediment and their subsequent recycling in the food chain when modeling over the long term after the end of a radionuclide release to the environment.

In order to test the common quality standards for the performance of measurements of internal radioactivity, the European Commission funded a European intercomparison of whole body counters, which was organized and carried out by the Institut fuer Strahlenhygiene (part of the German Bundesamt fuer Strahlenschutz). Forty-four whole body counting facilities from forty-two institutions in nineteen countries (the fifteen member states of the European Union plus Hungary, the Czech Republic, Switzerland and Norway) took part in this intercomparison, which made it the most comprehensive ever carried out in Europe. For the study, the 70 kg tissue equivalent St Petersburg phantom was used with rods containing 40K, 57Co, 60Co, and 137Cs. The overall results of the whole body counter study were rather good.

Since late 1992, over 100 building complexes in Taiwan, including both public and private schools, and 1,000 apartments have been identified as emitting elevated levels of gamma-radiation. These high levels of gamma-radiation have been traced to construction steel contaminated with 60Co. Accurate reconstruction of the radiation exposure dosage among residents is complicated by the discovery of multiple radioactive sources within the living spaces and by the lack of comprehensive information about resident life-style and occupancy patterns within these contaminated spaces. The objective of this study was to evaluate the sensitivity of current dose reconstruction approach employed in an epidemiological study for the health effects of these occupants. We apply a statistical method of local smoothing in dose rate estimation and examine factors that are closely associated with radiation exposure from multiple radioactive sources in the apartment. Two examples are used, a simulated measurement in a hypothetical room with three radioactive sources and a real apartment in Ming-Shan Villa, one of the contaminated buildings. The simulated and estimated means are compared along 5-10 selected points of measurement: by local smoothing approach, with the furniture-adjusted space, and with the occupancy time-weighted mean. We found that the local smoothing approach came much closer to theoretical values. The local smoothing approach may serve as a refined method of radiation dose distribution modeling in exposure estimation. Before environmental exposure assessment, "highly occupied zones" (HOZs) in the contaminated spaces must be identified. Estimates of the time spent in these HOZs are essential to obtain accurate dosage values. These results will facilitate a more accurate dose reconstruction in the assessment of residential exposure in apartments with elevated levels of radioactivity.

Assessment of radiological risks in strategies for decommissioning of nuclear installations have to consider not only technical concepts such as cutting and decontamination techniques but, even more important, requirements for input of reliable information on the hydrological situation and retardation capabilities of relevant radionuclides specific to the respective decommissioning operation. In this paper we describe appropriate methods for obtaining site-specific sorption data and present results achieved from a case study performed as a commercial contractual work preliminary to the planned decommissioning of a nuclear power plant. A detailed mineralogical study of the sediment used in our sorption experiment highlights the necessity of a thorough sample homogenization and characterization. Batch experiments using radiotracer techniques for the determination of site-specific sorption coefficients show significant retardation for Co-60 and Cs-137 after only 2 h of equilibration between the preconditioned groundwater and sediment. Sorption is more effective in the groundwater of a deeper aquifer containing a higher amount of colloidal clay (illite) particles < 0.63 micron. The Co-60 radiotracer is more completely sorbed than the Cs-137 radiotracer. Equilibration of radionuclide distribution is slow, particularly for Co-60. Presence of EDTA reduces sorption of Co-60 efficiently while Cs-137 sorption remains unaffected.

We used the multitracer technique to study the transfer of several radionuclides to two mushroom species. Radionuclides accumulated in the fruiting bodies of the mushrooms in the order of 83Rb > 65Zn > 54Mn > 22Na > 75Se and 85Sr > 60Co > 88Y, 102Rh, 139Ce, 143.144Pm, 146.153Gd and 173Lu > 175Hf. The concentration ratio values for 83Rb, 65Zn and 54Mn in the fruiting bodies were more than 10, whereas those for 60Co, 88Y, 102Rh, 121mTe, 175Hf and the rare earth elements were less than 1. There were major differences in the accumulations of the alkali elements.

As of October 1996 there are more than 90 radiation-contaminated steel supported rebar buildings (containing more than 1000 apartments) dispersed in the northern part of Taiwan. These apartments were contaminated with cobalt-60 at a total activity ranging from 1-140 microSv/yr. In this paper, a method is developed for evaluating external dose equivalent and dose equivalent rates encountered by the residents wearing specially designed thermoluminescent dosimeter (TLD)-embedded chains, belts and badges. Comparisons are also made between the TLD readings and the exposure readings from indoor layout personal dosimetry surveys and room occupancy adjustments to the buildings. The accuracy and sensitivity of the TLDs compared with the ionization chamber readings are judged to be considerable improvements over those of previous studies. From the present study, it is concluded that the reliability of the daily activity records provided by the residents during the entire TLD-wearing period is the most critical but challenging feature of the external dose equivalent measurement.

A model to predict the time weighted exposures to gamma radiation was developed for buildings constructed with structural steel having some contamination from 60Co. Several buildings throughout sixteen city blocks in downtown Taipei were built about ten years ago with this material. These buildings were used for residential, business, and educational purposes with radiation levels ranging from background to five hundred times background. A comprehensive epidemiologic study by the National Yang Ming University Medical School in Taipei is underway to study the effects of this exposure to the building occupants. An evaluation of external radiation exposure was performed using survey instruments and thermoluminescent dosimeters. Exposure data from the survey instruments were used in a computer model developed to calculate cumulative radiation exposure estimates for the epidemiologic research. While the survey instrument data provided radiation levels at a point in time, the thermoluminescent dosimeters were placed in fixed locations and on several volunteers for a period of one month to verify the modeling results. The model itself is a mathematical algorithm that provides estimates with minimum and maximum range values by taking into account differences in the survey data between adults and children, variable occupancy patterns, background radiation, and radioactive decay. Several assumptions (background rates, height adjustment values, and occupancy factors) are easily adjusted to improve the estimated radiation exposures. The model predicted the exposures as measured by the thermoluminescent dosimeters with greater reliability for adults than for children. The differences between the two methods were about 10-15% for the adults and about 60% for the child. This strategy, its advantages, limitations, and its performance against actual thermoluminescent dosimeter measurements are presented.

In this paper measurements of the radionuclides of 36Cl, 41Ca, 60Co, 152Eu and 154Eu in samples from Hiroshima, which were exposed to neutrons of the A-bomb explosion, are interpreted. In order to calculate the neutron spectrum at the sample site, neutron transport calculations using Monte Carlo techniques were carried out. Activation profiles in a granite mock-up irradiated with reactor neutrons could be reproduced by this method using DS86 input parameters. The calculated neutron spectrum at the sample site for non-thermal neutrons is identical to that obtained in DS86, but contains some 50% more thermal neutrons. The influence of parameters like soil composition, source terms and air humidity on the activation of these radioisotopes is discussed. The granite-covered earth at the sample site, for example, hardens the spectrum in comparison with DS86 values. Even when using a fission spectrum pointing downward and neglecting air humidity one cannot explain our 36Cl measurements. If the effective thermal neutron fluences, that have a similar ratio of resonance integral to thermal neutron capture cross sections obtained from 36Cl, 41Ca and 152Eu, are averaged, a bomb yield of about 16 kt is deduced in agreement with a bomb yield of (15 +/- 3) kt estimated in DS86.

The previously reported ability of SP-Sephadex C25 column chromatography for partitioning biologically important cobalamins has been modified to include analytical separation of nitritocobalamin (NO2-Cbl) and nitrosocobalamin (NO-Cbl). Gel column dimensions (1.5 x 11.0 cm), a low eluent flow-rate (125 microliters/min), collection of small eluate fractions (160 microliters) plus maintenance of He saturated mobile and gel phases all combined to eliminate ordinarily confusing proximal elution of NO2-Cbl and NO-Cb1 with sulfitocobalamin (SO3-Cbl) and cyanocobalamin. Cobalamin elution profiles from the gel column were monitored by direct radiometric analysis of 57Co-labelled cobalamin standards or competitive intrinsic factor radioassays for cobalamin sample sizes up to 10.0 ng. Failure to implement the chromatographic conditions detailed here totally obscured analysis of NO2-Cbl coexisting with SO3-Cbl in brain tissues for chicks exposed to dietary sulfites and caused oversight of NO-Cb1 normally coexisting in prepared NO2-Cbl standards.

This paper reports the experimental investigation of a simple design of plane-parallel electron chamber, which has very thin layers of copper (0.018 or 0.035 mm) as conducting material. Measurements comparing the prototype chambers with other ionization chambers (PTW/Markus, NACP) have been carried out, both in a 60Co gamma-ray beam and in high-energy electron beams. The results show that the Ce factors (proportional to the product of water/air stopping-power ratio and perturbation factor) for converting the in-phantom air-kerma-calibrated chamber reading to the absorbed dose to water are nearly constant for incident electron energies between 4 and 11 MeV for prototype chambers with 0.018 mm thick copper layers and between 4 and 15 MeV for chambers with 0.035 mm thick copper layers. Other aspects concerning these prototype chambers, such as polarity effect, cable effect, collecting efficiency and angular response, have also been studied and the results are presented in this paper.

An existing radiochemical NAA procedure for Cd, Co, and Cu was improved to allow determination of individual radiochemical yields by the radioisotopic tracer technique, thus eliminating errors owing to variable recovery. 109Cd was used as tracer for Cd determination via 115Cd/115mIn, 57Co for Co via 60Co, and potentially for Ni via 58Co, whereas as a novelty 67Cu, produced by reactor irradiation of ZnO of natural isotopic composition (by the 67Zn [n,p] 67Cu reaction) was used for Cu via the indicator nuclide 64Cu. The simple production and purification of 67Cu by anion exchange is described. Results for biological RMs are given and discussed.

Three types of tissue-air ratio (TAR) are summarized. These TARS differ in their definition of the in-air absorbed dose. The first defines it as the absorbed dose at the centre of a spherical or cylindrical minimal water phantom in free space. The second defines it as the maximum primary absorbed dose in a semi-infinite water phantom. The third defines it as the absorbed dose in an imaginary infinitesimal mass of water within the cavity of a chamber in free space, where the absorbed dose is averaged within the cavity. It is concluded that the 60Co TAR data compiled by Godden and the 60Co TAR data of Johns and Cunningham should be reviewed. Aeq and other factors are evaluated for spherical and cylindrical minimal water phantoms in a 60Co gamma-ray beam. A method of obtaining Aeq and other factors for an ionization chamber with a known Awall correction factor is also reported. The work indicates some discrepancies with previously published material.

For 60Co gamma-rays, using zero-area tissue-maximum ratio (TMR) and revised scatter-maximum ratio (SMR) data, we investigate how the scatter-primary ratio (SPR), the scatter factor (SF), and the dose-kerma ratio (beta) change with field size and depth. We also investigate how the depth of maximum absorbed dose (dmax) changes with field size in three ways: the first uses zero-area primary plus scatter absorbed dose data, the second uses integrated primary absorbed dose data, and the third uses integrated primary plus scatter absorbed dose data. The investigated characteristics are also compared with reported ones.

Specific activities of 152Eu:Eu in stone samples exposed to the Hiroshima atomic bomb were determined for 70 samples up to a 1,500-m slant range from the epicenter. The specific activities of 60Co:Co were also determined for six samples near the Hiroshima hypocenter. First, the 152Eu data were investigated to find out the directional dependence of neutron activation. Directional anisotropy was not definite; however, there was an indication that the activation in the west-southwest was lower than in other directions. Second, measured 152Eu and 60Co radioactivity data were compared with activation calculations based on DS86 neutrons. It is clearly shown that the measured data are lower than the calculation near the hypocenter and vice versa at long distances beyond 1,000 m. The calculated-to-measured ratios of 152Eu are 1.6 at the hypocenter, 1.0 at approximately 900 m, and 0.05 at a 1,500-m slant range. Present results indicate that systematic errors exist in the DS86 neutrons concerning the source-term spectrum, neutron transport calculations in air, and/or activation measurements.

The study objective was to determine whether environmental radionuclide accumulations were occurring in an aquatic system with a 13-y history of supplying a power plant with reactor-cooling water as well as receiving plant discharge. The aquatic system consisted of the following: 1) a reactor-cooling lake; 2) a secondary lake approximately 8 km downstream; and 3) a small stream that interfaced with the two lakes. Gamma-emitting radionuclides were identified and quantified in samples of benthic sediments obtained from representative areas of the aquatic system. This study demonstrated that in a reactor-aquatic cooling system, the component of the aquatic system most likely to experience radionuclide accumulation will not necessarily be the reactor-cooling lake, but will be that component of the aquatic system whose benthic sediments contain the highest concentrations of organic matter. Further, it was shown that the quantity of oxidizable organic matter present in a sediment is a good predictor or marker for potential sites of radionuclide accumulation (i.e., 60Co and 137Cs).

The implementation and results of a source term control program implemented at the James A. FitzPatrick Nuclear Power Plant (JAF), a mature boiling water reactor (BWR) facility that has been in commercial operation since 1975, are discussed. Following a chemical decontamination of the reactor water recirculation piping in the Reload 8/Cycle 9 refueling outage in 1988, hydrogen water chemistry (HWC) and feedwater Zn addition were implemented. This is the first application of both HWC and feedwater Zn addition in a BWR facility. The radiological benefits and impacts of combined operation of HWC and feedwater Zn addition at JAF during Cycle 9 are detailed and summarized. The implementation of hydrogen water chemistry resulted in a significant transport of corrosion products within the reactor coolant system that was greater than anticipated. Feedwater Zn addition appears to be effective in controlling buildup of other activated corrosion products such as 60Co on reactor water recirculation piping; however, adverse impacts were encountered. The major adverse impact of feedwater Zn addition is the production of 65Zn that is released during plant outages and operational transients.

Following ideas of Japanese and Canadian scientists the authors tried to develop practical application of dental enamel for dosimetry of gamma-radiation accumulated by an individual. Human teeth were irradiated in vitro with gamma-rays of 60Co and with x-rays, and the amount of free radicals in ++non-caries enamel was measured on an ESR spectrometer. Linear regression ESR signals on dose of radiation within an interval of 0.1-20 Gy were plotted for gamma- and x-rays with regression coefficients 0.276 and 0.693, respectively. These regressions were used for estimation of accumulated doses of gamma-radiation in 85 residents of Byelorussia and 301 residents of the Tomsk region during investigation of teeth that were removed in normal dental practice.

Specific activity 60Co/Co in two steel samples taken at 687m S and 1295m NNW from the hypocenter was measured by gamma-ray spectrometry and neutron activation analysis. The results were, respectively, (2.64 +/- 0.38) x 10(1) and (3.09 +/- 0.48) x 10(-1) dpm/mg Co at the time of bombing, which are consistent with previous data by Hashizume et al. for steel rings on the surface of roofs of buildings. The present data are expected to serve as verification of the bomb neutron transport calculations. Content of nickel and copper in the samples, determined by colorimetric and neutron activation methods, respectively, was too small to account for any significant 60Co production by the (n,p) and (n, alpha) reactions.