Ground Deposition Research Articles

Assessment of Radiological Dose around a 3-MW TRIGA Mark-II Research Reactor

A hypothetical accidental case of a 3-MW TRIGA Mark-II research reactor has been assumed to assess the radiological consequences due to the deposition of 137Cs and 90Sr on ground, vegetation, milk and meat. The air concentrations in sixteen cardinal directions have been estimated where the maximum concentration has been found to be at 110 m distance from the core of the reactor for all the directions. Calculated maximum doses of 137Cs, 90Sr and both 137Cs and 90Sr have been found to be within the ranges of 0.005-0.014 μSv hr–1, 0.013-0.036 μSv hr–1 and 0.018-0.05 μSv hr–1, respectively for all the directions, which are below the measured background dose limit 0.25 μSv hr–1 and also within the IAEA acceptable dose rate limit of 0.5 μSv hr–1. The calculated low doses due to the aforementioned radionuclides can be considered negligible with regard to the radiation hazards. The relationship between total effective dose rate for various pathways (i.e. immersion, inhalation, ground deposition, and ingestion of contaminated vegetation, milk, meat) and air concentration in all the directions has been established. Obtained relation reveals that the total effective dose rate is directly proportional to the air concentration, and the overall proportionality constants for 137Cs and 90Sr radionuclides have been obtained as 0.57 and 0.28, respectively. This study might provide information on the radiological safety required for the radiation protection purposes of the people living in the vicinity of the reactor site.

The eruption, pyroclastic flow behaviour, and caldera in-filling processes of the extremely large volume (> 1290 km3), intra- to extra-caldera, Permian Ora (Ignimbrite) Formation, Southern Alps, Italy

The Permian Ora Formation (277–274Ma) preserves the products of the Ora caldera ‘super-eruption’, Northern Italy. The stratigraphic architecture of the exceptionally well preserved intra-caldera succession provides evidence for caldera collapse at the onset of the eruption, a multiple discharge point, fissure eruption style, and progressive, incremental caldera in-filling by numerous pyroclastic flow pulses within the caldera. The ignimbrites of the Ora Formation are voluminous (>1290km3), crystal-rich (~25 to 55%), and ubiquitously welded. The Ora Formation has been divided into four members (a–d), which also define the principal eruption phases. The eruption proceeded in four main stages: (1) early caldera collapse and vent opening, producing locally distributed, basal co-ignimbrite lithic breccia (member a); (2) vent clearing, which produced the eutaxitic, lithic-rich ignimbrite and minor thin ground and ash-cloud surge deposits (member b); (3) waxing and steady eruption, which produced the dominant eutaxitic, coarse-crystal-rich ignimbrite, with local lithic-rich and fine-crystal-rich ignimbrite and minor surge deposits (member c); and (4) waning eruption, recorded by the eutaxitic, fine-crystal-rich ignimbrite, with local lithic-rich ignimbrite deposits (member d).The incremental filling and late-stage outpouring of pyroclastic material from the caldera is recorded by vertical and lateral lithofacies deposit variation and some correlation between stratigraphic sections. These findings reveal a structure to the outwardly monotonous, >1300m thick, intra-caldera fill and thinner (<230m) outflow successions. These data together with the gradational contacts between the main ignimbrite lithofacies, support the hypothesis that pyroclastic material was erupted from multiple source regions in various parts of the caldera, during quasi-steady, low eruption column collapse and pyroclastic flow forming events. Field study revealed the absence of a Plinian fallout deposit, suggesting a lack of a high, buoyant, Plinian precursor eruption phase. This caldera was initiated immediately by a low collapsing column phase, producing the main, thick ignimbrite succession. Simultaneously, catastrophic volcano-tectonic caldera collapse and decompression of the magma chamber occurred, facilitated by the regional extensional environment in the Permian and pre-existing crustal weaknesses. The Ora pyroclastic flow system is suggested as having been a hot and poorly expanded, high particle concentration, granular density current. The confined nature of the majority of the erupted products to the intra-caldera setting, reduced the formation of the full array of facies commonly expected in ignimbrites in extra-caldera settings.

Assessment of Radiological Dose around a 3-MW TRIGA Mark-II Research Reactor

A hypothetical accidental case of a 3-MW TRIGA Mark-II research reactor has been assumed to assess the radiological consequences due to the deposition of 137Cs and 90Sr on ground, vegetation, milk and meat. The air concentrations in sixteen cardinal directions have been estimated where the maximum concentration has been found to be at 110 m distance from the core of the reactor for all the directions. Calculated maximum doses of 137Cs, 90Sr and both 137Cs and 90Sr have been found to be within the ranges of 0.005-0.014 μSv hr–1, 0.013-0.036 μSv hr–1 and 0.018-0.05 μSv hr–1, respectively for all the directions, which are below the measured background dose limit 0.25 μSv hr–1 and also within the IAEA acceptable dose rate limit of 0.5 μSv hr–1. The calculated low doses due to the aforementioned radionuclides can be considered negligible with regard to the radiation hazards. The relationship between total effective dose rate for various pathways (i.e. immersion, inhalation, ground deposition, and ingestion of contaminated vegetation, milk, meat) and air concentration in all the directions has been established. Obtained relation reveals that the total effective dose rate is directly proportional to the air concentration, and the overall proportionality constants for 137Cs and 90Sr radionuclides have been obtained as 0.57 and 0.28, respectively. This study might provide information on the radiological safety required for the radiation protection purposes of the people living in the vicinity of the reactor site.

Validation of the FALL3D model for the 2008 Chaitén eruption using field and satellite data

The 2008 Chaiten Volcano eruption began on 2 May 2008 with an explosive phase that injected large amounts of tephra into the atmosphere. During the first week of the eruption, volcanic ash clouds were transported for hundreds of kilometres over Argentina by the prevailing westerly winds. Tephra deposition extended to the Atlantic Ocean and severely affected the Argentinean Patagonia. Impacts included air and water quality degradation, disruption of ground transportation systems and cancellation of flights at airports more than 1,500 km apart. We use the FALL3D tephra transport model coupled with the Weather Research and Forecasting-Advanced Research Weather (WRF-ARW) meteorological model to simulate tephra fall from the 2-9 May 2008 eruptive period. Our hindcast results are in good agreement with satellite imagery and reproduce ground deposit observations. Key aspects of our analysis, not considered during syn-eruptive forecasts, are the re-initialization of each simulation with actualized meteorological forecast cycles and better constrained model inputs including column heights (inferred from reanalysis of GOES-10 imagery and nearby atmospheric soundings) and granulometric data obtained from field campaigns. This study shows the potential of coupling WRF/ARW and FALL3D models for short-term forecast of volcanic ash clouds. Our results highlight that, in order to improve forecasting of ash cloud dispersion and tephra deposition, it is essential to implement an operational observation system to measure temporal variations of column height and granulometric characteristics of tephra particles in nearly real-time, at proximal as well as distal locations.

Environmental measurements and inspections on imported foods and feedstuffs in Greece after the Fukushima accident

The radionuclides released during the accident at the Fukushima Daichii nuclear power plant following the Tōhoku earthquake and tsunami on 11 March 2011 were dispersed in the whole north hemisphere. Traces of (131)I, (134)Cs and (137)Cs reached Greece and were detected in air, grass, sheep milk, ground deposition, rainwater and drainage water. Members of Six Greek laboratories of the national network for environmental radioactivity monitoring have collaborated with the Greek Atomic Energy Commission (GAEC) and carried out measurements during the time period between 11 March 2011 and 10 May 2011 and reported their results to GAEC. These laboratories are sited in three Greek cities, Athens, Thessaloniki and Ioannina, covering a large part of the Greek territory. The concentrations of the radionuclides were studied as a function of time. The first indication for the arrival of the radionuclides in Greece originating from Fukushima accident took place on 24 March 2011. After 28 April 2011', concentrations of all the radionuclides were below the minimum detectable activities (<10 μBq m(-3) for (131)I). The range of concentration values in aerosol particles was 10-520 μBq m(-3) for (131)I, 10-200 μBq m(-3) for (134)Cs and 10-200 μBq m(-3) for (137)Cs and was 10-2200 μBq m(-3) for (131)I in gaseous phase. The ratios of (131)I/(137)Cs and (134)Cs/(137)Cs concentrations are also presented. For (131)I, the maximum concentration detected in grass was 2.2 Bq kg(-1). In the case of sheep milk, the maximum concentration detected for (131)I was 2 Bq l(-1). Furthermore, more than 200 samples of imported foodstuff have been measured in Greece, following the EC directives on the inspection of food and feeding stuffs.

RADIATION DOSE TO HUMAN AND NON-HUMAN BIOTA IN THE REPUBLIC OF KOREA RESULTING FROM THE FUKUSHIMA NUCLEAR ACCIDENT

This paper describes the radiation doses to human and non-human biota in the Republic of Korea, as a result of the Fukushima nuclear accident. By using the measured airborne activity and ground deposition, the effective and thyroid doses of five human age groups (infant, 5 years, 10 years, 15 years and adult) were estimated by the ECOSYS code, and the whole body absorbed dose rate of the eight Korean reference animals and plants (RAPs) was estimated by the K-BIOTA (the Korean computer code to assess the risk of radioactivity to wildlife). The first-year effective and thyroid human doses ranged from 5.7E-5 mSv in the infant group to 2.0E-4 mSv in the 5 years group, and from 5.0E-4 mSv in the infant group to 3.4E-3 mSv in the 5 years group, respectively. The life-time (70 years) effective and thyroid human doses ranged from 1.5E-4 mSv in the infant group to 3.0E-4 mSv in the 5 years group, and from 6.0E-4 mSv in the infant group to 3.5E-3 mSv in the 5 years group, respectively. The estimated maximum whole body absorbed dose rate to the Korean RAPs was 6.7E-7 mGy/d for a snake living in soil (terrestrial biota), and 2.0E-5 mGy/d for freshwater fish (aquatic biota), both of which were far less than the generic dose criteria to protect biota from ionizing radiation. Also, the screening level assessment for ERICA's (Environmental Risks from Ionizing Contaminants: Assessments and management) limiting organisms showed that the risk quotient (RQ) for the estimated maximum soil and water activity was significantly less than unity for both the terrestrial and freshwater organisms. Conclusively, the radiological risk of the radioactivity released into the environment by the Fukushima nuclear accident to the public and the non-human biota in the republic of Korea is considered negligible.

Granular anchors under vertical loading – axial pull

Granular anchors are a relatively new concept in ground engineering with relatively little known regarding their load–displacement behaviour, failure modes, ultimate pullout capacity, and also potential applications. A granular anchor consists of three main components: a base plate, tendon, and compacted granular backfill. The tendon is used to transmit the applied load to the base plate, which compresses the granular material to form the anchor. A study of the load–displacement response and ultimate pullout capacity of granular anchors constructed in intact lodgement till and made ground deposits is reported in this paper. Parallel tests were also performed on cast in situ concrete anchors, which are traditionally used for anchoring purposes. A new method of analysis for the determination of the ultimate pullout capacity of granular anchors is presented and verified experimentally, with the dominant mode of failure controlled by the column length (L) to diameter (D) ratio. Granular anchors with L/D &gt; 7 principally failed by bulging whereas short granular anchors failed on shaft resistance, with the latter mobilizing similar pullout capacities as conventional concrete anchors.

Atmospheric dispersion and ground deposition induced by the Fukushima Nuclear Power Plant accident: A local-scale simulation and sensitivity study

Following the Fukushima Daiichi Nuclear Power Plant (FNPP1) accident on March 2011, radioactive products were released in the atmosphere. Simulations at local scale (within 80 km of FNPP1) were carried out by the Institute of Radiation Protection and Nuclear Safety (IRSN) with the Gaussian Puff model pX, during the crisis and since then, to assess the radiological and environmental consequences. The evolution of atmospheric and ground activity simulated at local scale is presented with a “reference” simulation, whose performance is assessed through comparisons with environmental monitoring data (gamma dose rate and deposition). The results are within a factor of 2–5 of the observations for gamma dose rates (0.52 and 0.85 for FAC2 and FAC5), and 5–10 for deposition (0.31 for FAC2, 0.73 for FAC5 and 0.90 for FAC10). A sensitivity analysis is also made to highlight the most sensitive parameters. A source term comparison is made between IRSN's estimation, and those from Katata et al. (2012) and Stohl et al. (2011). Results are quite sensitive to the source term, but also to wind direction and dispersion parameters. Dry deposition budget is more sensitive than wet deposition. Gamma dose rates are more sensitive than deposition, in particular peak values.

Radiocesium fallout in the grasslands on Sakhalin, Kunashir and Shikotan Islands due to Fukushima accident: the radioactive contamination of soil and plants in 2011

The accident at the Fukushima Dai-ichi Nuclear Power Plant has resulted in radioactive contamination of environmental media and food in the Far East of Russia, particularly in the Sakhalin Region. To obtain the knowledge about the 134Cs and 137Cs spatial distribution in the Sakhalin Region, soil samples were collected at 31 representative grassland sites on Sakhalin, Kunashir and Shikotan islands (43.80°–46.40° N and 142.73°–146.84° E) in the middle of May and around the end of September to early October 2011. In the autumn, vegetation samples (mixed grass/forb crop and bamboo, Sasa sp.) were collected together with soil samples. Maximum measured activity concentrations (on dry weight) of 134Cs and 137Cs in soil were 30 Bq kg−1 and 210 Bq kg−1, respectively. Within soil profile, 134Cs activity concentrations declined rapidly with depth. Although for both sampling occasions (in the spring and autumn) the radionuclide was completely retained in the upper 3–4 cm of soil, a deeper penetration of the contaminant into the ground was observed in the autumn. In contrast with 134Cs, activity concentrations of 137Cs demonstrated a broad range of the vertical distribution in soil; at most sites, the radionuclide was found down to a depth of 20 cm. This resulted from interfering the aged pre-accidental 137Cs and the new Fukushima-borne 137Cs. To calculate contribution of these sources to the inventory of 137Cs, the 134Cs:137Cs activity ratio of 1:1 in Fukushima fallout (the reference date 15 March 2011) was used. The maximum deposition density of Fukushima-derived 137Cs was found on Shikotan and Kunashir Islands with average density of 0.124 ± 0.018 kBq m−2 and 0.086 ± 0.026 kBq m−2, respectively. Sakhalin Island was less contaminated by Fukushima-derived 137Cs of 0.021 ± 0.018 kBq m−2. For the south of Sakhalin Island, the reference inventory of pre-Fukushima 137Cs was calculated as 1.93 ± 0.25 kBq m−2 (reference date 15 March 2011). For Shikotan and Kunashir Islands, the pre-Fukushima reference levels of 137Cs ground contamination appeared to be higher: on average, 2.81 ± 0.35 kBq m−2. Maximum measured activity concentrations (on wet weight) of 134Cs and 137Cs in the vegetation were 5 Bq kg−1 and 18 Bq kg−1, respectively. Soil-to-plant aggregated transfer factors, Tags, for 134Cs were more than an order of magnitude higher than those for 137Cs. For the above-ground biomass density of 1 kg per m2 (wet weight), plant contamination may contribute approximately 2% and 0.1% to the ground deposition of Fukushima-derived and pre-accidental 137Cs, respectively.

Spray interactions with a windbreak netting used in orchard applications

An extruded plastic windbreak netting, with an optical porosity of 64%, was used to evaluate its potential in reducing sprayer air velocity and intercepting spray droplets in simulated orchard applications. The air velocity reduction was assessed in laboratory tests carried out under static and dynamic conditions. In field tests, the netting was directly sprayed with two orchard airblast sprayers, equipped with different nozzle types.Air velocity reduction was higher in the dynamic setting but decreased at lower air velocities. It also decreased when the netting distance from the air outlet increased. In field tests, the analysis of spray fallout depositions in open area conditions revealed lower recovery rate for conventional than air induction hollow cone nozzles. Comparing the fallout collected on sampling lines (perpendicular to the sprayer travel path) behind the netting and in the open area showed an average spray retention of 30.5% for the netting. The netting affected the fallout pattern along the sampling line, showing a droplet trajectory deflection associated with the momentum and kinetic energy losses. An increase of ground deposition was noticed just behind the netting (up to 2 m). At farther distances ground deposits decreased considerably. The results showed the potential for using a windbreak netting to simulate the droplet retention characteristics of a hypothetical tree foliage, in order to reduce the effect of canopy variability in certain orchard applications studies.

Volcanic ash forecast during the June 2011 Cordón Caulle eruption

We modelled the transport and deposition of ash from the June 2011 eruption from Cordon Caulle volcanic complex, Chile. The modelling strategy, currently under development at the Argentinean Naval Hydrographic Service and National Meteorological Service, couples the weather research and forecasting (WRF/ARW) meteorological model with the FALL3D ash dispersal model. The strategy uses volcanological inputs inferred from satellite imagery, eruption reports and preliminary grain-size data obtained during the first days of the eruption from an Argentinean ash sample collection network. In this sense, the results shown here can be regarded as a quasi-syn-eruptive forecast for the first 16 days of the eruption. Although this article describes the modelling process in the aftermath of the crisis, the strategy was implemented from the beginning of the eruption, and results were made available to the Buenos Aires Volcanic Ash Advisory Centers and other end users. The model predicts ash cloud trajectories, concentration of ash at relevant flight levels, expected deposit thickness and ash accumulation rates at relevant localities. Here, we validate the modelling strategy by comparing results with satellite retrievals and syn-eruptive ground deposit measurements. Results highlight the goodness of the combined WRF/ARW-FALL3D forecasting system and point out the usefulness of coupling both models for short-term forecast of volcanic ash clouds.

A new deep ice core in the Northern Patagonian Icefield reveals a regional cooling in a warming world

Atmospheric dispersion of volcanic ash from explosive eruptions or from subsequent fallout deposit resuspension causes a range of impacts and disruptions on human activities and ecosystems. The April–May 2015 Calbuco eruption in Chile involved eruption and resuspension activities. We overview the chronology, effects, and products resulting from these events, in order to validate an operational forecast strategy for tephra dispersal. The modelling strategy builds on coupling the meteorological Weather Research and Forecasting (WRF/ARW) model with the FALL3D dispersal model for eruptive and resuspension processes. The eruption modelling considers two distinct particle granulometries, a preliminary first guess distribution used operationally when no field data was available yet, and a refined distribution based on field measurements. Volcanological inputs were inferred from eruption reports and results from an Argentina–Chilean ash sample data network, which performed in-situ sampling during the eruption. In order to validate the modelling strategy, results were compared with satellite retrievals and ground deposit measurements. Results indicate that the WRF-FALL3D modelling system can provide reasonable forecasts in both eruption and resuspension modes, particularly when the adjusted granulometry is considered. The study also highlights the importance of having dedicated datasets of active volcanoes furnishing first-guess model inputs during the early stages of an eruption.

Dispersion of Heavy Particles Emitted from Area Sources in the Unstable Atmospheric Boundary Layer

Reliable predictions of the daytime dispersal of heavy particles in the unstable atmospheric boundary layer are important in a variety of disciplines. For many applications, particles disperse from area sources near the ground, and corresponding theoretical solutions are desired to reveal insight into the physical processes. Here, theoretical solutions recently developed for neutral conditions are modified to include the effects of atmospheric instability. The Obukhov length L O and convection velocity w ⋆ are introduced to characterize the patterns of particle dispersion, in additional to friction velocity u ⋆ and settling velocity w s used in the neutral case. The major effects of atmospheric instability are accounted for by modifying the vertical velocity variance profile and considering the ratio of velocity scales w ⋆/u ⋆. Theoretical predictions including the mean concentration profile, plume height, and horizontal transport above the source, and ground deposition flux downwind from the source agree well with large-eddy simulation results while the particle plume is within the atmospheric surface layer. The deposition curve is characterized by a power-law decay whose exponent depends on u ⋆, w s, and w ⋆. A second steeper power-law develops once the plume extends into the mixed layer. This effect is enhanced with increasing atmospheric instability, implying that particles disperse farther from the source.

Dose distribution of 131I, 132I, 133I, 134I, and 135I due to a hypothetical accident of TRIGA Mark-II research reactor.

An attempt has been made in the work to assess radiological dose due to the deposition of 131 I, 132 I, 133 I, 134 I, and 135 I on ground, vegetation, milk and meat considering a hypothetical accident of TRIGA Mark-II research reactor at AERE, Savar. Contribution of dose from ingestion of vegetation due to 131 I has been found to be dominant (62.96%). Also found that contribution of 132 I from immersion is higher (53.67%) and contribution of 133 I in meat is higher (45.64%). The contribution due to 134 I in both from immersion (46.13%) and from ground deposition (47.19%) was dominant while the contribution of 135 I from ground deposition (30.11%), inhalation (26.77%) and immersion (25.92%) were higher. Final result says that the vegetation is the dominant contributor (66.91%) for iodine.

Environmental Measurements in an Emergency

Emergency responders from the Department of Energy are trained regularly to assess the environmental consequences of a radiological or nuclear incident. While drills and exercises are highly effective tools in rehearsing for an emergency, the accidents at the Fukushima Daiichi Nuclear Power Plants presented real-world complexities that are difficult or impossible to simulate in such training. Customarily, the modeled hypothetical event used to create a drill or exercise data set is simple, well defined, and closely resembles conventional assumptions about the type of that event. Consequently, the modeling performed by players from the outset closely resembles the planner's hypothetical event. This approach also entails idealized, uniform data in the simulated plume and ground deposition scenarios created for the drill that match the modeling closely. The real-world event that occurred in Japan sharply deviated from the simple picture ordinarily created for drills and exercises that typically involve a release of radioactivity that is of short duration, a single puff with constant meteorology, or simple deviation such as a wind shift to bifurcate the plume. In the very early stages, accurate plume and deposition model predictions were difficult to produce due to the lack of field monitoring data and other information. In contrast to drills and exercises where plant monitoring data is available, there was much less plant monitoring data, essentially no reactor state information, and the meteorological conditions and releases were much more complex. Inevitably, the measurements in Japan were not homogeneous, thus presenting technical challenges to assessors tasked with ensuring the quality of the finished assessments and data products for government officials, the responder community, and the public. In this paper, examples of some operational real-world complexities are considered. Procedures, measurements, or radiological assessments from the Fukushima response are not in the purview of this paper.

An analytical model for dispersion of biological particles emitted from area sources: Inclusion of dispersion in the crosswind direction

An analytical model for dispersion of biological particles such as spores and pollens released from finite area sources into the atmospheric boundary layer is proposed. The model is applicable to rectangular fields aligned with the mean wind and accounts for effects of turbulent dispersion in the vertical and crosswind direction, as well as depletion of airborne material due to dry deposition. Predictions for the mean particle concentration above the area source and ground deposition downwind from it are derived and validated against detailed numerical simulations of pollen dispersal using large eddy simulation. Effects of particle settling velocity and area source size and geometry on dispersal patterns are investigated. Results show that along the centerline above the source, effects of crosswind dispersion are negligible (except for very narrow area sources). Ground deposition fluxes downwind from the source are strongly affected by crosswind dispersion. Similarly to area sources infinitely long in the crosswind direction, deposition fluxes far from rectangular sources display a power-law decay with distance. The power-law exponent is larger than the one for infinitely wide fields and depends on the relative importance of gravitational settling and turbulent dispersion in the vertical and crosswind directions, but does not depend on source geometry. However, the distance from the source at which the power-law decay is first observed does depend on source geometry.

Application of the Monte Carlo code DETEFF to efficiency calibrations for in situ gamma-ray spectrometry

We studied the applicability of the Monte Carlo code DETEFF for the efficiency calibration of detectors for in situ gamma-ray spectrometry determinations of ground deposition activity levels. For this purpose, the code DETEFF was applied to a study case, and the calculated 137Cs activity deposition levels at four sites were compared with published values obtained both by soil sampling and by in situ measurements. The 137Cs ground deposition levels obtained with DETEFF were found to be equivalent to the results of the study case within the uncertainties involved. The code DETEFF could thus be used for the efficiency calibration of in situ gamma-ray spectrometry for the determination of ground deposition activity using the uniform slab model. It has the advantage of requiring far less simulation time than general Monte Carlo codes adapted for efficiency computation, which is essential for in situ gamma-ray spectrometry where the measurement configuration yields low detection efficiency.

Busan–Gimhae Light Rail Transit Bridge in South Korea

The Busan–Gimhae Light Rail Transit, a private investment project costing US$ 1,2 billion, connects the cities of Busan and Gimhae via light rail transit. This project is the first commercially qualified driverless light rail system in South Korea. The project is 23,2 km in length, consists of a steel box girder bridge 8,9 m in width and 15 m in height, and is the longest bridge structure in South Korea to date. The major structure consists of 21 stations and one depot. The route passes through an area of thick, soft ground deposits at the mouth of the Nakdong River. The deepest sedimentary layer is 85 m. To optimize the foundation design of the bridge structure, pile load tests were performed. Based on the results of these tests, it was determined that friction piles would be constructed rather than the more commonly used end-bearing piles. The 1,6 km section passing through the Nakdong River was constructed in the form of a 5 × 80 m steel box girder bridge, and the remaining section as a 2 × 50 m bridge. The total number of piers is 448. When the route passing through the center of the city was constructed, all processes were performed in a working area only 18 m in width, so as not to disrupt the flow of traffic. This project had a 5-year construction period, and was completed in April 2011. The light rail system was opened to public in September 2011, after test drives.

Radiological Concentration Distribution of &amp;lt;sup&amp;gt;131&amp;lt;/sup&amp;gt;I, &amp;lt;sup&amp;gt;132&amp;lt;/sup&amp;gt;I, &amp;lt;sup&amp;gt;133&amp;lt;/sup&amp;gt;I, &amp;lt;sup&amp;gt;134&amp;lt;/sup&amp;gt;I, and &amp;lt;sup&amp;gt;135&amp;lt;/sup&amp;gt;I Due to a Hypothetical Accident of TRIGA Mark-II Research Reactor

The present work gives a methodology for assessing radiological concentration of 131I, 132I, 133I, 134I, and 135I due to a hypothetical accident of TRIGA Mark-II research Reactor at AERE, Savar, Bangladesh. The concentrations were estimated through different pathways like ingestion of vegetation, milk, and meat from air and ground deposition. The maximum air concentrations for all 16 directions were found at 110 m distance from the core of the reactor and it was found to be highest in the southern (S) direction. The maximum ground concentration occurred immediately just after the accident in different directions. In all pathways, the most concentration was found to be in S-direction. The concentrations in vegetation of 131I, 133I, 135I were significant, while no concentrations of 132I and 134I were observed. The concentration in vegetation for 131I was found to be highest than all other isotopes of iodine. The concentrations of 133I were found to be higher and concentrations of 134I were observed to be lower in both milk and meat compared to other radio isotopes of iodine. In the case of a radiological accident, the results of the present study will be a valuable guide for adopting radiological safety measures for radiation protection against the ingestion of vegetables, milk and meat from around the research reactor at AERE, Savar, Bangladesh.

Model to Predict Spray Deposition in Citrus Airblast Sprayer Applications: Part 2. Spray Deposition

A model was developed to simulate spray dispersion and predict pesticide deposition in citrus trees when using an air-carrier sprayer. The model can be split into two parts: (1) dispersion, which focuses on spray transport and droplet dispersion in open space, and (2) deposition, which focuses on spray transport and deposition inside a canopy. The dispersion part of the model and its validation were presented in the first part of this article. This second part presents details of the deposition component of the model and validation with data from a field experiment. The experiment involved spray application of a fluorescent dye solution to orange trees using a conventional airblast sprayer, and sampling leaves at two heights and four canopy depths. The spray treatments, consisting of combinations of two nozzles (Albuz ATR Lilac and Blue) and two forward speeds (2.4 and 4.8 km h-1), were applied in a randomized complete block design with five replications. Samples were analyzed by fluorometry, and leaf area was measured with an area meter. The results showed good agreements between the model output and the experimental data for canopy deposition, with the best predictions yielding a modeling efficiency and correlation coefficient of 61.3% and 0.92, respectively. However, the ground deposition data were overly underpredicted by more than three orders of magnitude and were not considered appropriate. This shortcoming notwithstanding, the model has potential for meeting the set objectives, and it has been implemented in an expert system to assist spray applicators in making decisions critical for efficient spray operations.