Transport Of Radioactivity Research Articles

A probabilistic model for the simulation of radioactivity transport through a heterogeneous porous medium

The subsurface transport of radioactivity is critically governed by the nature of the medium. In general, the near earth surface medium is a mixture of a homogeneous (sand/soil) part and small stones sitting at few arbitrary locations. A probabilistic approach is adopted to estimate the locations of stones inside a 2D domain and the migration through such a medium for a given distribution is modelled. The entire process is repeated to arrive at a probabilistically averaged concentration value. Results show that the overall transport decreases systematically with the increase of heterogeneity of the medium. Next, simulations are carried out for different heterogeneity and different durations of the migration process. Here also a systematic trend is observed. Concentration corresponding to any in-homogeneity or time of migration falling within this range of modelling can be estimated by interpolation.

The HotSpot Code as a Tool to Improve Risk Analysis During Emergencies: Predicting I-131 and CS-137 Dispersion in the Fukushima Nuclear Accident

Conventional and non-conventional emergencies are among the most important safety and security concerns of the new millennium. Nuclear power and research plants, high-energy particle accelerators, radioactive substances for industrial and medical uses are all considered credible sources of threats both in warfare and in terror scenarios. Estimates of potential radiation releases of radioactive contamination related to these threats are therefore essential in order to prepare and respond to such scenarios. The goal of this paper is to demonstrate that computational modeling codes to simulate transport of radioactivity are extremely valuable to assess expected radiation levels and to improve risk analysis during emergencies helping the emergency planner and the first responders in the first hours of an occurring emergency.

Determination of radiological background fields designated for inverse modelling during atypical low wind speed meteorological episode

This article focuses on the formation of complex trajectories of radiological background fields for atypical accidental discharges of radioactivity into the atmosphere during very low wind speed episodes (calms). Within several hours of a calm meteorological situation, a relatively significant level of radioactivity can be accumulated around the source. In the next stage, the calm situation is assumed to terminate and convective movement of the air immediately starts. A packet of accumulated radioactivity, which has the form of multiple Gaussian puffs, is drifted by wind. Consequently, the pollution is disseminated over the terrain. Significant transport of radioactivity even behind the protective zone of a nuclear facility (up to between 15 and 20 km) has been observed. Original optional statistical pre-processing of calm's results is inserted between the calm and convective stages of the trajectory generation which may improve performance of following computationally expensive methods of Bayesian filtering. Determination of complex trajectory passing through both calm and convective stages of the release scenario represents inevitable prior information for prospective assimilation techniques. Draft twin experiment is outlined for a simple assimilation scenario for re-estimation of the main model parameters based on a notional monitoring network in the outer convective region.

Unconventional oil and gas development and ambient particle radioactivity

Unconventional oil and natural gas development (UOGD) expanded extensively in the United States from the early 2000s. However, the influence of UOGD on the radioactivity of ambient particulate is not well understood. We collected the ambient particle radioactivity (PR) measurements of RadNet, a nationwide environmental radiation monitoring network. We obtained the information of over 1.5 million wells from the Enverus database. We investigated the association between the upwind UOGD well count and the downwind gross-beta radiation with adjustment for environmental factors governing the natural emission and transport of radioactivity. Our statistical analysis found that an additional 100 upwind UOGD wells within 20 km is associated with an increase of 0.024 mBq/m3 (95% confidence interval [CI], 0.020, 0.028 mBq/m3) in the gross-beta particle radiation downwind. Based on the published health analysis of PR, the widespread UOGD could induce adverse health effects to residents living close to UOGD by elevating PR.

Dose and risk estimation of Cs-137 and I-131 released from a hypothetical accident in Akkuyu Nuclear Power Plant

The construction of Akkuyu Nuclear Power Plant (NPP) was launched in 2018 and the plant is expected to be operative by the year 2023. Being situated in the Mediterranean coastline, Akkuyu NPP will be the first nuclear power generation facility in Turkey. The plant will have four Russian VVER-1200 type pressurized water reactors with a total installed capacity of 4800 MW. In this study, atmospheric dispersion and ground level deposition of Cs-137 and I-131 released from a possible accident in Akkuyu NPP was estimated using a Lagrangian particle dispersion model, FLEXPART, for different time periods representing relatively extreme meteorological conditions for Mersin. The source term used in simulations was assumed the same with that of the Chernobyl NPP accident that occurred in 1986. In addition, cumulative dose and risk values were calculated from FLEXPART output datasets considering potential exposure pathways such as inhalation, ground-shine exposure and cloud-shine exposure. The results were further analyzed with python codes and dose and risk maps were created for local and regional scales. According to results of the study, it was found that the vicinity of Mersin and Central Anatolia were simulated to be the most significantly affected areas from the accident under both scenario conditions. The northern and western parts and all coastlines of Turkey were simulated to be more contaminated in the simulations conducted under December 2009 conditions, whereas southern and western parts of Turkey and some parts of Middle East countries like Syria, Iraq and Lebanon were simulated to be comparatively more contaminated under August 2010 conditions. The results indicated that radioactivity levels exceeding 100 kBq/m2 were observed near the accident site under both scenario conditions. Values exceeding 10 kBq/m2 level were simulated in western Turkey in the first scenario whereas similar values were found in eastern Turkey in the second scenario. Furthermore, the results indicated 7-day thyroid dose values ranging between 0.10 mSv and 10.0 mSv in western and eastern parts of Mediterranean region for the first and the second scenario, respectively. Similarly, 1-year effective dose of only Cs-137 ranged between 0.1 mSv and 1.0 mSv around Akkuyu NPP site in both scenarios. The results revealed that meteorological conditions were among the most important parameter for the fate and transport of radioactivity originating from such a catastrophic event.

Hypothetical Accident in Polish Nuclear Power Plant. Worst Case Scenario for Main Polish Cities

Abstract Poland is under threat of potential accidents in nuclear power plants located in its close vicinity, in almost all neighboring countries. Moreover, there are plans to establish a new nuclear power plant in Polish coast. In this paper the analysis of atmospheric transport of radioactive material released during a potential accident in the future nuclear power plant is presented. In the first part of study transport of radioactivity as seen from the long time perspective is analyzed. This involves trajectory analysis as a tool for describing the statistics of air pollution transport pattern and screening the meteorological situations for episode studies. Large sets of meteorological data for selected episodes were stored as a result of this process. Estimation of risk includes both analysis of the consequences and probability analysis of an occurrence of such situation. Episodes then were comprehensively studied in the second phase of the study, using the Eulerian dispersion model for simulation of atmospheric transport of pollutants. This study has proven that the time needed for reaction in case of (hypothetical) accident is enormously short.

Some results of determining the source and reasons for the appearance of 106Ru in Russia in September-October 2017

Probable locations of the sources of ruthenium-106 in the atmosphere in September-October 2017 have been considered. Taking into account the monoisotopic nature of the increase in ruthenium-106 concentration in the ground level air and atmospheric precipitation, the most probable version is substantiated, which suggests that ruthenium-106 came from a ground source located in the Southern or the Middle Urals. In order to locate the possible point of Ru-106 emission into the atmosphere, calculations of the time-inversed travel of air masses at the heights of 500-1500 m from the Ru-106 concentration measurement locations at European points during the relevant observation period were used. To confirm the correctness of the source location, calculations were performed that involved simulating regional transport and propagation of radioactivity in the near zone in case of a hypothetical emission of ruthenium-106 from a conventional source in the Southern Urals, in order to compare the simulation results with the available daily ruthenium-106 drop-out measurement data.

Impacts on the terrestrial environment in case of a hypothetical accident involving the recovery of the dumped Russian submarine K-27

Objects containing radioactivity have been routinely dumped in Arctic waters near NW Russia up until the 1990s. One of the most radioactive objects in this region, the nuclear submarine K-27, was dumped in Stepogovo Fjord and contained spent nuclear fuel (SNF). Although the two K-27 submarine reactors were mothballed before dumping, concerns about the potential long term risks of contamination remain and plans to retrieve and decommission K-27 exist. In this article, human dose and environmental impact aseessments are presented for two possible future scenarios involving: (1) an ingress of water into a reactor in situ leading to a spontaneous chain reaction (SCR) and (2) an on-board fire when SNF is being removed at the mainland decommissiong site at Gremhika Bay on the Kola Peninsula. Assessments have been completed using conservative assumptions, focusing on possible effects to Norwegian territory. Atmospheric transport and deposition of radioactivity was modelled near field and regionally, using appropriate models, whilst human doses and environmental exposures were modelled using a standard IAEA approach and the ERICA tool, respectively. Results indicate that large areas of Norwegian territory could be affected by fallout from the Gremhika scenario, especially in the north, though at levels two orders of magnitude lower than those observed after the Chernobyl accident. Potential doses, primarily due to ground shine, to a critical group of personnel on-site at Stepogovo resulting from a SCR could require preventative measures based on ICRP recommendations (20–100 mSv). Doses to non-human biota in Norway for the Gremhika scenario would be negligible, typical of background dose rates for terrestrial organisms.

The effect of spatially varying velocity field on the transport of radioactivity in a porous medium

In the event of an accidental leak of the immobilized nuclear waste from an underground repository, it may come in contact of the flow of underground water and start migrating. Depending on the nature of the geological medium, the flow velocity of water may vary spatially. Here, we report a numerical study on the migration of radioactivity due to a space dependent flow field. For a detailed analysis, seven different types of velocity profiles are considered and the corresponding concentrations are compared.

A dynamic model to estimate the activity concentration and whole body dose rate of marine biota as consequences of a nuclear accident

This paper describes a dynamic compartment model (K-BIOTA-DYN-M) to assess the activity concentration and whole body dose rate of marine biota as a result of a nuclear accident. The model considers the transport of radioactivity between the marine biota through the food chain, and applies the first order kinetic model for the sedimentation of radionuclides from seawater onto sediment. A set of ordinary differential equations representing the model are simultaneously solved to calculate the activity concentration of the biota and the sediment, and subsequently the dose rates, given the seawater activity concentration. The model was applied to investigate the long-term effect of the Fukushima nuclear accident on the marine biota using 131I, 134Cs, and, 137Cs activity concentrations of seawater measured for up to about 2.5 years after the accident at two locations in the port of the Fukushima Daiichi Nuclear Power Station (FDNPS) which was the most highly contaminated area.The predicted results showed that the accumulated dose for 3 months after the accident was about 4–4.5Gy, indicating the possibility of occurrence of an acute radiation effect in the early phase after the Fukushima accident; however, the total dose rate for most organisms studied was usually below the UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation)’s bench mark level for chronic exposure except for the initial phase of the accident, suggesting a very limited radiological effect on the marine biota at the population level. The predicted Cs sediment activity by the first-order kinetic model for the sedimentation was in a good agreement with the measured activity concentration. By varying the ecological parameter values, the present model was able to predict the very scattered 137Cs activity concentrations of fishes measured in the port of FDNPS. Conclusively, the present dynamic model can be usefully applied to estimate the activity concentration and whole body dose rate of the marine biota as the consequence of a nuclear accident.

Regional long-term model of radioactivity dispersion and fate in the Northwestern Pacific and adjacent seas: application to the Fukushima Dai-ichi accident

The compartment model POSEIDON-R was modified and applied to the Northwestern Pacific and adjacent seas to simulate the transport and fate of radioactivity in the period 1945–2010, and to perform a radiological assessment on the releases of radioactivity due to the Fukushima Dai-ichi accident for the period 2011–2040. The model predicts the dispersion of radioactivity in the water column and in sediments, the transfer of radionuclides throughout the marine food web, and subsequent doses to humans due to the consumption of marine products. A generic predictive dynamic food-chain model is used instead of the biological concentration factor (BCF) approach. The radionuclide uptake model for fish has as a central feature the accumulation of radionuclides in the target tissue. The three layer structure of the water column makes it possible to describe the vertical structure of radioactivity in deep waters. In total 175 compartments cover the Northwestern Pacific, the East China and Yellow Seas and the East/Japan Sea. The model was validated from 137Cs data for the period 1945–2010. Calculated concentrations of 137Cs in water, bottom sediments and marine organisms in the coastal compartment, before and after the accident, are in close agreement with measurements from the Japanese agencies. The agreement for water is achieved when an additional continuous flux of 3.6 TBq y−1 is used for underground leakage of contaminated water from the Fukushima Dai-ichi NPP, during the three years following the accident. The dynamic food web model predicts that due to the delay of the transfer throughout the food web, the concentration of 137Cs for piscivorous fishes returns to background level only in 2016. For the year 2011, the calculated individual dose rate for Fukushima Prefecture due to consumption of fishery products is 3.6 μSv y−1. Following the Fukushima Dai-ichi accident the collective dose due to ingestion of marine products for Japan increased in 2011 by a factor of 6 in comparison with 2010.

An air-mass trajectory study of the transport of radioactivity from Fukushima to Thessaloniki, Greece and Milan, Italy

Analyses of 131I, 137Cs and 134Cs in airborne aerosols were carried out in daily samples at two different sites of investigation: Thessaloniki, Greece (40° N) and Milan, Italy (45° N) after the Fukushima accident during the period of March–April, 2011. The radionuclide concentrations were determined and studied as a function of time. The 131I concentration in air over Milan and Thessaloniki peaked on April 3–4, 2011, with observed activities 467 μBq m−3 and 497 μBq m−3, respectively. The 134Cs/137Cs activity ratio values in air were around 1 in both regions, related to the burn-up history of the damaged nuclear fuel of the destroyed nuclear reactor. The high 131I/137Cs ratio, observed during the first days after the accident, followed by lower values during the following days, reflects not only the initial release ratio but also the different volatility, attachment and removal of the two isotopes during transportation due to their different physico-chemical properties. No artificial radionuclides could be detected in air after April 28, 2011 in both regions of investigation. The different maxima of airborne 131I and 134,137Cs in these two regions were related to long-range air mass transport from Japan, across the Pacific and to Central Europe. Analysis of backward trajectories was used to confirm the arrival of artificial radionuclides following atmospheric transport and processing. HYSPLIT backward trajectories were applied for the interpretation of activity variations of measured radionuclides.

Total beta activity, 137Cs and 90Sr in surface air in northern Finland in 1963

Abstract Air filter samples collected at Sodankylä (67º22´ N, 26º39´ E) were analyzed to determine concentrations of 137Cs and 90Sr in surface air in northern Finland in 1963. Previously, activity concentrations of Pu isotopes have been determined from the same filters. Activity concentrations of 137Cs and 90Sr in surface air were <50 μBq/m3–13800 ± 2700 μBq/m3 and <10 μBq/m3–5340 ± 290 μBq/m3, respectively. Air concentrations of 137Cs and 90Sr varied seasonally with a maximum in spring due to the springtime enhanced transportation of air masses with radioactive aerosols from the stratosphere to the troposphere. Activity ratios 90Sr/239+240Pu and 90Sr/137Cs were 6.9 ± 0.8–75 ± 5 and 0.08 ± 0.03–1.46 ± 0.51, respectively. The median value for the 90Sr/137Cs ratio (0.508) indicates contamination from global nuclear test fallout. An air mass back trajectory analysis suggests that no direct transport of radioactivity from the Novaya Zemlya test site to northern Finland occurred in 1963.

Radionuclide Hysterosalpingography Is Not a Reliable Tool for Investigation of Fallopian Tube Transport – A Controlled Randomized Study Using Particles of Two Sizes during Three Different Parts of the Menstrual Cycle

Background/Aims: Earlier studies with radionuclide hysterosalpingography (RN-HSG) using either small or large particles have shown different results. Some studies have questioned the clinical relevance of RN-HSG. The aim of this study was to evaluate the RN-HSG method using two different sizes of radio-labelled particles during different parts of the menstrual cycle. Methods: Ten healthy women, 28–40 years of age (mean 34.5), with proven fertility, regular menstrual cycle, not using oral contraceptives and due to undergo laparoscopic sterilization, were randomized to RN-HSG after deposition of a solution with either small Albures or large MAASOL, ^99mTc-radio-labelled particles into the cervix uteri. Investigations were, for every patient, performed during the follicular, peri-ovulatory and mid-luteal parts of the menstrual cycle. Transport of radioactivity from cervix to uterus and Fallopian tubes was evaluated. Results: The RN-HSG investigations could not show any difference between the two different sizes of radio-labelled particles. Transport of radioactivity to the Fallopian tube was seen only in some cases and most frequently during the peri-ovulatory period. Conclusion: We found the RN-HSG investigations inconclusive. The RN-HSG method does not seem to be a reliable tool for the investigation of Fallopian tube transport.

Transport of a passive scalar across a protective wall-jet in a pipe. Part II: Analysis and interpretation

First part of this paper ( Tesař, 2011) described experimental investigations, combined with numerical flowfield computations, of a pipe flow in which a parallel wall-jet is blown along the inner surface of the pipe. The aim is to separate the main central flow and prevent its contact with the pipe wall. Although originally motivated by the problem of preventing transport of radioactivity to a radiation detector and its activation, the investigations used heat/mass transport analogy so that the actual subject of investigation was transport of heat from warm central air flow across a cool wall-jet flow into the (also cool) wall of the flow containing pipe. This heat transfer is itself also a problem which may be of interest in applications. In the previous part, apart from the description of the experiments, were also presented the basic characteristics of the time-mean velocity and temperature profiles. This second part analyses the obtained combined experimental and computational data to deduce information about general character and intensity of the radial transport across the turbulent protective wall-jets.

Modelling radioactivity in the Irish Sea: From discharge to dose

In order to support authorised discharges of low level radioactive liquid effluent into coastal regions, mathematical models are required to robustly predict radiological impacts on critical groups of current and proposed changes to liquid discharges. The grid model presented here simulates the long term dispersion and transport of radioactivity discharged from the Sellafield site in Cumbria, UK, and the subsequent exposure of critical groups in Cumbria and across the Irish Sea in Northern Ireland. The fine grid of the model allows a good resolution of the seabed sediment distribution. This benefits the predictions for the last decades of low discharge level, when bed sediment can become a source of contamination by bringing back the legacy of past high discharges. This is highlighted by the dose comparison, where the predicted dose to Cumbria critical group follows well the dose estimated from environmental data during the low discharge level period.

RADIOACTIVE MATERIALS IN BIOSOLIDS: DOSE MODELING

The Interagency Steering Committee on Radiation Standards (ISCORS) has recently completed a study of the occurrence within the United States of radioactive materials in sewage sludge and sewage incineration ash. One component of that effort was an examination of the possible transport of radioactivity from sludge into the local environment and the subsequent exposure of humans. A stochastic environmental pathway model was applied separately to seven hypothetical, generic sludge-release scenarios, leading to the creation of seven tables of Dose-to-Source Ratios (DSR), which can be used in translating from specific activity in sludge into dose to an individual. These DSR values were then combined with the results of an ISCORS survey of sludge and ash at more than 300 publicly owned treatment works, to explore the potential for radiation exposure of sludge workers and members of the public. This paper provides a brief overview of the pathway modeling methodology employed in the exposure and dose assessments and discusses technical aspects of the results obtained.

Simulations of Transboundary Atmospheric Transport of Radioactivity Released from Nuclear Risk Sites at the Far East

A long-range transport of radioactive pollutants in the atmosphere has received considerable attention in recent years, corresponding with many models to address these issues. In this paper a trajectory model TraModel and a Lagrangian particle dispersion model ParModel were introduced and applied successfully to simulate transboundary atmospheric transport of radioactivity released from the Tian Wan Nuclear Power Plant (NPP) in China and Vladivostok nuclear risk site (NRS) in the Russian Far East for some specific weather condition.

Radioactive contamination in the upper part of the Techa river: stirring-up of bottom sediments and precipitation of suspended particles. Analysis of the data obtained in 1949-1951.

A hydrodynamic model of the upper part of the Techa river was developed on the basis of the river valley geometry as well as data of hydrological conditions and of the granulometric composition of bottom sediments. The model describes the transport of radioactivity by suspended sediments with different granulometric compositions (clay, silt) in the early 1950s. It includes the stirring-up of bottom sediments and the precipitation of suspended sediments as a function of water discharge rate and water level in the investigated part of the river. The results allow to specify the development of the river system contamination as a result of inflow of suspended sediments contaminated with radionuclides. In the period of liquid radioactive waste (LRW) discharges, the water of the Techa river contained a large fraction of finely dispersed particles of less than 5 micro m diameter. At the site of LRW discharge 80% of the discharged activity was adsorbed to these particles. Depending on the water flow, 40-80% of the suspensions precipitated at the bottom of subsequent sedimentation reservoirs. A total of about 1.6 MCi adsorbed to the suspended particles entered the open hydrographic system of the Techa river. The conclusion that the largest part of the activity was adsorbed on the suspended particles contradicts the assumption in the Techa river dosimetry system, TRDS-2000, that most of the released activity entered the Techa river in soluble form. For a correct reconstruction of the doses received by the Techa river population it is, therefore, essential to consider hydrodynamic models that take into account the transport of radionuclides adsorbed on the suspended particles.

Radioactivity in cervical mucus after intraperitoneal deposition of Tc-99 m labelled albumin particles before and after sterilisation

Objective: To study the transport of radiolabelled albumin particles from the pouch of Douglas to cervical mucus. Study design: A prospective randomised study, including 10 healthy women, undergoing laparoscopic sterilization. A solution of human serum albumin particles, labelled with Technetium 99 m (Tc-99 m) was injected into the pouch of Douglas, either before or after sterilisation. Results: Gamma camera images showed gradual spread to the entire peritoneal cavity. Blood samples, showed increasing levels of radioactivity. Measurement of radioactivity in cervical mucus showed significant activity both in women sterilized before and after the deposition. Conclusion: The study showed evidence of transport of radioactivity from the pouch of Douglas to cervical mucus. The transport seemed to consist of free activity since no radionuclide labelled particles could be detected in cervical mucus. The transport was probably haematogenous or lymphatic and not intraluminal through the fallopian tube. Further studies utilizing particles comparable in size to fertilized ova are required to design methods for evaluating the transport from the fallopian tube to the uterine cavity.