Radioactive Transport Research Articles

Transfer functions for QA /QB international regulatory limits for the safe transport of radioactive materials

This paper presents a proposed revision of the International Atomic Energy Agency transport regulations, related to the A 1 and A 2 limit values used to determine the radioactive transport classification. Based on the ‘Q system’, a novel methodology was introduced to derive QA and QB values related to scenarios involving external exposure from a distant source. These values are key parameters that respectively represent the total effective dose and total equivalent dose to the skin, from all primary and secondary particles contributing to radiation exposure. The International Working Group (WG A 1/A 2) is established and associated with the TRANSSC Technical Expert Group on Radiation Protection. A review of the A 1 and A 2 values is performed in response to identified limitations within the existing Q system. The followed approach is based on Monte Carlo simulations that enabled the development of transfer functions aimed at reducing computational time and increasing the flexibility of dose evaluations for any radionuclide with known particle emission spectra. This method allows updating the QA and QB values to account for future data evolutions (decay data, fluence-to-dose conversion coefficients) and standardizing the calculation of regulation limits across all referenced radionuclides and scenarios related to external exposure. The transfer functions are established using three Monte Carlo simulation codes—FLUKA, Geant4, and MCNP—and address the previous limitations of the ‘Q system’, reflecting the latest International Commission for Radiation Protection recommendations and improvements in calculation techniques. The results of the WG show consistent agreement across the codes, with minor discrepancies observed at low primary energies due to statistical uncertainties and different handling of stopping power for electrons/positrons in the codes. This revised approach aligns with current standards and recommendations, ensuring that the radiological consequences of transport accidents are acceptable for the new A 1 and A 2 limits from a radiological protection perspective.

Thermal Tests of Type B Radioactive Transport Package: Experimental Description and Heat Flux Analysis

ABSTRACTThe design of Type B radioactive transport package should be able to withstand the fire accident scenario in transportation accident conditions. For the simulation of the fire scenario, there are mainly three methods: pool fire test, furnace test and thermal radiation test. This paper tried to carry out the fire test with the furnace method that the conditions in the furnace can be more carefully controlled. The paper described the requirements of fire test, test conditions and measurement test methods and analysed the temperature change of fire site and the heat flux data of the surface of the package during the fire test. The test results seemed that the fire test method could provide satisfactory thermal environment for fire test of Type B radioactive transport package.

Machine learning-enabled weather forecasting for real-time radioactive transport and contamination prediction

Effective responses to nuclear accidents require accurate and fast predictions of radionuclide transport in the atmosphere. However, real-time forecasting has been challenging, since predicting the transport requires meteorological forecasting, which relies on computationally intensive numerical weather simulations. To address this challenge, we have developed statistical emulators for the Weather Research and Forecasting model (WRF) to forecast wind and temperature fields around the source location. The emulator is constructed based on pre-computed WRF simulation results and their boundary conditions from global circulation models (GCM), enabling the rapid prediction of local-scale wind/temperature fields by ingesting the GCM-predicted boundary conditions available online for the next several days. We have explored two methods: (1) deep neural network and (2) a vector autoregressive model with exogenous variables (VARX). A Gaussian plume model is then used to take these field as input and to predict the distribution of radioactive material/dose in the environment. The results show that both emulators are capable of forecasting the wind field for several days in the future in real-time, while not compromising accuracy. The autoregressive model has shown a strong performance of predicting the temperature field, owing to the strong temporal autocorrelations in the temperature data. This framework offers a powerful tool for informed decision-making during emergencies such as enabling meteorology-informed timing of containment venting, and real-time guidance of evacuation strategies.

On the inclusion of forest exposure pathways into a stylized lake-farm scenario in a geological repository safety analysis

Geological disposal of radioactive waste has been recognized as the ‘reference solution’ to ensure the safety required for the present and future society and environment. To study the possible exposure pathways from groundwater to humans, radioactive transport modelling is used. One of the ecosystems that may play a significant role when assessing the dose conversion factor (i.e. the dose resulting from a nominal release of 1 Bq/year of each radionuclide) for humans is forest. In this paper we have developed a model of a lake-farm system with a forest component. The biosphere system used in this study represents a typical agricultural scenario in Finland, amended with a typical forest. A lake is assumed to form due to post-glacial land uplift. The main features of this future lake have been obtained from our probabilistic shoreline displacement model. Both deterministic calculations and sensitivity analysis were carried out to simulate the model. The deterministic simulation demonstrates the behaviour of the studied radionuclides (36Cl, 135Cs, 129I, 237Np, 90Sr, 99Tc and 238U) and the proportions of different exposure pathways to humans. Particularly for 135Cs and 129I, forest pathways make a notable contribution to the dose conversion factor. The sensitivity analysis was done using two methods: EFAST and Sobol’. With both methods, the parameters related to the farm contribute the most to the variance of the dose conversion factor for humans. The study demonstrates that the exposure pathways related to forest products may make a considerable contribution to the dose conversion factor in a lake–farm–forest system. It is also confirmed that an advanced sensitivity analysis for a radionuclide transport and dose assessment model on such a landscape scale is feasible even with moderate computational efforts.

Sediment and Radioactivity Transport in the Bohai, Yellow, and East China Seas: A Modeling Study

This paper is concerned with the development of a radionuclide dispersion model for the nuclear power plants in the Bohai, Yellow, and East China seas (BYECS) characterized by high turbidity and multi-scale circulations, focusing on the comparison of dispersion processes of 137Cs depending upon, in particular, the suspended sediment concentration and erosion/sedimentation processes. The simulations were carried out using a multi-fraction sediment transport model embedded in the semi-implicit Eulerian–Lagrangian finite-element coupled wave-circulation model linked with the model of radionuclide transport, which describes the key radionuclide transfer processes in the system of water–multi-fraction sediments. In contrast to the Eulerian models used for hydrodynamics and sediment transport processes, the Lagrangian technique was applied to simulate the transport of radionuclides. The simulation results for total suspended concentration agreed with in situ measurements and the Geostationary Ocean Color Imager data. The results of the simulation of hypothetical releases of 137Cs from four nuclear power plants (NPPs) placed in BYECS essentially differ from the real release of activity in the Pacific Ocean shelf due to the Fukushima Daiichi accident, which took place at the same time and released activity that was similar. The total amount of bottom contamination of 137Cs in releases from the Sanmen, Hanbit, and Hongyanhe NPPs was about 40% of dissolved component, and the total amount of suspended component was about 20% of dissolved component, in contrast with the Fukushima Daiichi accident, where the particulate component was only 2%. The results demonstrate the importance of erosion processes in the budget of 137Cs in shallow areas around the Sanmen and Hanbit NPPs, where strong wind and tidal currents took place.

BORDER MANAGEMENT AND PROCEDURE IN CASE OF HIGH LEVEL OF RADIATION AT THE BORDER CROSSINGS IN THE REPUBLIC OF NORTH MACEDONIA

The aim of this paper is to strengthen the ability of border crossing staff to check the presence of persons and vehicles for possible presence of radioactive materials outside regulatory control, in an effort to prevent smuggling and illicit trafficking in such means and materials. Regarding the use of radiation detection equipment, which is used at the border crossings in the Republic of North Macedonia, for the needs of control and verification of the entire import and export for possible presence of radioactive shipments. It documents the overall detailed process that the officers involved (customs officers and border police) will use to detect all radioactive material passing through the site, the process that will be used to determine the legitimacy of the radioactive substances that would be detected and the most appropriate way, which should be reacted and acted upon if illegal shipments of this type are detected. Information that will help existing and new officials to perform their duties in a timely manner, in an appropriate and consistent manner.

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.

Modelling mixing and transport of radioactive effluents in water reservoirs: an application to the operation of a fusion facility

The aim of the present study is to model mixing and transport of radioactive effluents in the course of time between two water reservoirs. To test the model, a hypothetical case study is presented of liquid effluents potentially released during normal operation of a fusion neutron source devoted to radioisotopes production. A suitable example is an accelerator-driven intense D-T 14 MeV neutron source relying on T and D ion beams, with the potential to provide a neutron yield in the range \( 5{-}7 \cdot 10^{13}\) s-1. It is expected that during normal operation a number of radionuclides will be produced and managed. The present report discusses the mechanisms and parameters which affect and control the fate of radionuclides potentially released into two connected water reservoirs during normal operation of the plant. A mathematical mixing model is developed that describes groundwater flow and radioactive transport between the two basins. The aim of this study is to estimate the amount of radioactivity concentration in both water reservoirs at any time, an information that can be used for radiation protection purposes.

Multi-Physics Model Development for Polonium Transport Behavior in a Lead-Cooled Fast Reactor

210Po, a highly toxic element with strong volatility, is one of the main source terms of a Gen-IV lead-cooled fast reactor (LFR). Therefore, the radioactive safety caused by 210Po has become an important topic in LFR-related research. In order to simulate the behavior of 210Po in an LFR, this work developed a multi-physics model of an LFR from the perspective of radioactive transport. Considering the effects of nuclide decay, cover gas leakage, containment ventilation, and Po aerosol deposition, a comprehensive simulation was carried out to evaluate the sensitivity of those effects on the 210Po distribution in detail. Preliminary results indicate that during normal operation, most of the 210Po in the LBE exist in the form of PbPo, and around 10–9 of 210Po could evaporate from the LBE into the cover gas, and then further leak into the containment. In addition, even if the leakage rate of 210Po in the cover gas into the containment is maintained at 5‰ per day, due to the deposition of Po aerosol, the 210Po contamination on the inner surface of the containment is still below the radioactivity concentration limits.

Role of Serine 263 in the Human Choline Transporter 1 and Congenital Myasthenic Syndrome

Disruptions of the neuromuscular junction (NMJ) result in congenital myasthenic syndromes (CMS). CMS is characterized by a range of phenotypes including muscle weakness, apnoeas, akinesia or even death. CMS type 20 is caused by mutations in the SLC5A7 gene which encodes for the choline transporter (CHT1). CHT1 re-uptake of choline is a requirement for acetylcholine synthesis and NMJ function. The 13 transmembrane domain CHT1 protein is also thought to be phosphorylated at several sites but the role of phosphorylation remains unknown. We have recently reported the missense recessive variant c.C788>T in SLC5A7 (NM_021815.4), in a family with a history of CMS using whole exome sequencing. This variant encodes a p.S263F substitution in CHT1 and results in a complete loss of transport function despite a normal plasma membrane localization. To assess whether a change in phosphorylation and/or charge/size of position 263 results in altered transport function, three substitutions were introduced into CHT1: p.S263A, and phosphomimetics p.S263D and p.S263E. Upon expression in HEK293 cells and the utilization of cell surface biotinylation experiments, we found that WT, p.S263F and p.S263A mutants were present at the plasma membrane. Radioactive transport assays indicated that the p.S263A mutant retained a high level of transport activity while the p.S263D and p.S263E mutants were non-functional. Immobilized metal affinity electrophoresis suggests that wild-type CHT1 may be more phosphorylated than the p.S263F CHT1 mutant. These results support the essential role of the Serine 263 residue in CHT1 choline transport possibly via altering its phosphorylation status as well as size/charge at this position.

Операционные величины радиоактивного загрязнения кожи в случае радиационной аварии

Purpose: Development of recommendations on the use in medical practice of institutions under FMBA of Russia of operational values of radioactive skin contamination in the event of radiological accidents.
 Material and methods: The easily measured radiation parameters were used as operational values: ambient dose equivalent rate (ADER) of γ-radiation, density of skin contamination with γ-, β- and α-emitting radionuclides. Operational values ​​of skin contamination were estimated on the basis of experimental data described in the literature and models on the kinetics of radioactive substances transport in the body, accepted values ​​of dose criteria for deterministic and stochastic effects. The estimation of radioactive material resorption through the skin was based on the results of experimental studies in laboratory animals (mainly piglets) for a limited set of chemical compounds of radionuclides.
 Results: The values of γ-ADER of the main dose-forming radionuclides measured at a distance of 10 cm from the skin surface in the range of 10–1000 μSv/h and the possible health effects due to the skin exposure and the intake of radioactive substances into the body were presented. In the IAEA recommendations, the level of skin contamination at 1 µSv/h is considered as a significant operational value according to the criterion of radioactive substances intake through the mouth from the contaminated surface of the hands. However, in our opinion, this estimate is excessively conservative; therefore it is not included in the recommended operational values. If the skin is contaminated with γ-β-emitting radionuclide solutions at a surface contamination higher than 106 Bq/cm2 (ADER ≥1000 µSv/h), the out of turn emergency decontamination should be carried out. Obligatory indications for the whole body counter examination after thorough decontamination and conducting biophysical analysis of bioassay are the following operational values: γ-ADER from the skin > 10 µSv/h; surface contamination of intact skin with β-active radionuclides > 20 000 β-part./(cm2·min); surface contamination of intact skin with α-active radionuclides > 200 α-part./ (cm2·min).
 Conclusion: The recommended operational values allow preliminarily and promptly to assess the health risk not only in the case of external (contact) exposure of the skin and underlying tissues, but also due to the intake of soluble radioactive substances into the body through intact and damaged (injured) skin. Taking into account the high degree of uncertainty of the estimates obtained, the operational values ​​should be considered as strictly conservative. They should be used only to determinate of urgency of decontamination carrying out for the provision of medical care during the prehospital and early hospital periods with the obligatory follow-up dosimetry examination for the final assessment of absorbed dose.

Time marker of 137Cs fallout maximum in lake sediments of Northwest China

Caesium-137 (137Cs) has no natural source and is commonly employed in establishing the chronology of recent lake sediments in the Anthropocene epoch. Because of their location in the northern mid-latitude Westerlies circulation region, downwind of the Chernobyl accident and their proximity to the Lop Nur Chinese Nuclear Testing (CNT) site, lake sediments in NW China record a137Cs fallout maximum of global atmospheric thermonuclear weapon tests (GTWT) in 1963–1964 Common Era (CE), with probably local fallout subpeaks due to the Chernobyl accident in 1986 CE and CNT in 1976 CE. This complexity means that the use of 137Cs fallout maximum in lake sediments as a time marker in NW China is thus far not well constrained, impeding assessment of recent and future changes in paleoclimate and human activities. To identify the 137Cs time marker and provide a reliable chronology of surface lake sediments for investigating paleoclimatic changes and for defining the Anthropocene epoch in NW China during the last 50–100 years, here we describe chronologies of 6 near-surface sediment cores from NW China based on 137Cs and 210Pb activities, and review the chronology of 23 lake sediments and 10 ice cores from NW China and central Asia based on 137Cs, 210Pb, 239+240Pu, 3H, 241Am, and beta-activity dating methods, and annual layer counting, as well as 240Pu/239Pu isotopic ratios. Based on the potential influence of radioactivity transport from the Chernobyl accident and CNT, and the comparison with deposition records of 26 European lake sediments and 5 Alpine ice cores, we propose that the 137Cs fallout maximum of lake sediments in NW China and central Asia is primarily attributable to GTWT and that there is no unambiguous evidence to confirm the Chernobyl- and CNT-derived 137Cs local-fallout subpeaks. Taking into account the approximately one-year delay between injection of 137Cs into the atmosphere and its incorporation in lake sediment records, we conclude that the 137Cs fallout maximum in lake sediments of NW China provides a reliable GTWT time marker for 1964 CE.

Deposition velocities of some natural radionuclides from the atmosphere at Ninh Thuan and Dong Nai of Vietnam

The deposition velocities of Be-7, K-40, Th-232, U-238 and Pb-210 radionuclides from the atmosphere at Ninh Thuan and Dong Nai monitoring stations of Vietnam were investigated. The deposition velocity was calculated based on it’s specific radioactivity in aerosols and deposition density in fallout samples. The data of the deposition velocities of radionuclides from the atmosphere are needed as input data for the models to simulate atmospheric radioactive dispersion and assess the public dose around nuclear facilities. The radioactivity of Be-7, K-40, Th-232, U-238 and Pb-210 nuclides in aerosols and fallout samples were analyzed by using a low level background gamma spectrometer equipped with HPGe detector of high resolution. The results show that the deposition velocities of Be-7, K-40, Th-232, U-238 and Pb-210 nuclides from the air are in ranges of 0.04÷1.71; 1.84÷27.46; 1.46÷23.63; 0.80÷26.13 and 0.06÷1.53 (cm/s), with average values of 0.55; 13.81; 8.22; 8.12 and 0.58 (cm/s), respectively. The deposition velocities of the radionuclides in the survey areas are comparable with those found in tropical and subtropical regions and these results could be served as the database of the World radioactive transport parameters.

High affinity of 4-(4-(dimethylamino)styryl)-N-methylpyridinium transport for assessing organic cation drugs in hepatocellular carcinoma cells.

Human organic cation transporter 1 (hOCT1) and human organic cation transporter 3 (hOCT3) are highly expressed in hepatocytes and play important roles in cationic drug absorption, distribution, and elimination. A previous study demonstrated that downregulation of hOCT1 and hOCT3 mRNA was related to hepatocellular carcinoma (HepG2) prognosis and severity. Whether these transporters expressed in HepG2 cells serve for cationic drug delivery has not been investigated. Besides radioactive transport, options for assessing hOCTs in hepatocytes are limited. This study clarified the significant roles of hOCTs in HepG2 by comparing cationic fluorescent 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP+ ) with traditional [3 H]-1-methyl-4-phenylpyridinium (MPP+ ). The results showed ASP+ was preferably transported into HepG2 compared to [3 H]-MPP+ with high affinity and a high maximal transport rate. Selective transport of ASP+ mediated by hOCTs was influenced by extracellular pH, temperature, and membrane depolarization, corresponding to hOCT1 and hOCT3 expressions. Furthermore, transport of cationic drugs, metformin, and paclitaxel in HepG2 cells was blunted by OCT inhibitors, suggesting that hOCT1 and hOCT3 expressed in HepG2 cells exhibit notable impacts on cationic drug actions. The fluorescent ASP+ -based in vitro model may also provide a rapid and powerful analytical tool for further screening of cationic drug actions and interactions with hOCTs, particularly hOCT1 and hOCT3 in hepatocellular carcinoma.

Simulating Three-Dimensional Plume Migration of a Radionuclide Decay Chain through Groundwater

In this study, we present a semi-analytical model for simulating three-dimensional radioactivity transport of a radionuclide decay chain and assessing the radiological dose impact on the general public. The mechanisms and processes considered in the model include the one-dimensional advection, hydrodynamic dispersion in longitudinal and two lateral directions, linear equilibrium sorption, and first-order radioactive decay reactions. The semi-analytical model is derived for a semi-infinite domain, and the solutions in the Laplace domain for members of the decay chain are first generalized in a compact format. The concentrations in the original domain of each nuclide are independently evaluated with the help of the efficient and robust Laplace numerical inverse algorithms. The accuracy of the derived semi-analytical model is demonstrated by comparison of our developed model with an existing analytical model described in the literature. The results of the verification exercise indicate that the derived semi-analytical model is accurate and robust. The developed semi-analytical model is applied to an illustrative example that simulates the three-dimensional plume migration of a radionuclide decay chain on both the temporal and spatial scales. Moreover, the time histories of the radiological doses at different distances from the inflow source boundary are presented to understand the potential radiological impact on the general public. The developed model facilitates rapid assessment of the radiological impact posed by the presence of radionuclides in the environment because of leakage from a nuclear waste repository or accidental discharges from nuclear facilities.

Optimization of Radiation Model of Infrared Decoy with Neural Network

In this paper, a numerical model is proposed to calculate the infrared radiation characteristics based on the solution of radioactive transport. However, due to the demand of the real-time, a method with back-propagation neural network (BPNN) is developed to optimize the proposed model. The results of simulation experiments show that BPNN possesses good prediction accuracy, and can make the numerical model achieve the real-time requirement.

Dynamic numerical recipes to improve detection schemes for the interdiction of radioactive shipment

Radiation Portal Monitors (RPM) acquire sequential measurements of gamma activity that can be modeled as a sequence of Poisson distributed random numbers. These series can be analyzed with Statistical Process Control (SPC) methods to trigger alarms when the statistical distribution of the ambient dose during a transit changes. Some usual SPC methods have been compared and modified to narrow the time required to bound an alarm. Both the probabilities of detection and the Average Run Length (ARL) are used and fitted to curves to benchmark the SPC methods, which are ranked as: SR, EWMA, CUSUM, SPRT, FLR, and Shewhart.

Safe Handling of Nuclear Cardiology Radioactive Shipments

Safe Handling of Nuclear Cardiology Radioactive Shipments

Incorporating radioactive decay into charging and coagulation of multicomponent radioactive aerosols

Compositional changes by the decay of radionuclides in radioactive aerosols can influence their charging state, coagulation frequency and size distribution throughout their atmospheric lifetime. The importance of such effects is unknown as they have not been considered in microphysical and global radioactivity transport studies to date. We explore the effects of compositional changes on the charging efficiency and coagulation rates of aerosols using a set of kinetic equations that couple all relevant processes (decay, charging and coagulation) and their evolution over time. Compared to a coupled aggregation-tracer model for the prediction of the radioactive composition of particulates undergoing coagulation, our kinetic approach can provide similar results using much less central processing unit time. Together with other considerations, our approach is computational efficient enough to allow implementation in 3D atmospheric transport models. The decay of radionuclides and the production of decay products within radioactive aerosols may significantly affect the aerosol charging rates, and either hinder or promote the coagulation of multicomponent radioactive aerosols. These results suggest that radiological phenomena occurring within radioactive aerosols, as well as subsequent effects on aerosol microphysics, should be considered in regional and global models to more accurately predict radioactivity transport in the atmosphere in case of a nuclear plant accident.

A Novel Calcium Uptake Transporter of Uncharacterized P-Type ATPase Family Supplies Calcium for Cell Surface Integrity in Mycobacterium smegmatis.

ABSTRACTCa2+ plays an important role in the physiology of bacteria. Intracellular Ca2+ concentrations are tightly maintained in the nanomolar range. Molecular mechanisms of Ca2+ uptake in bacteria remain elusive. Here we show that CtpE is responsible for Ca2+ uptake in Mycobacterium smegmatis. It represents a previously uncharacterized P-type ATPase family in bacteria. Disruption of ctpE in M. smegmatis resulted in a mutant with impaired growth under Ca2+-deficient conditions. The growth defect of the mutant could be rescued by Ca2+ or by ectopic expression of ctpE from M. smegmatis or the orthologous gene (Rv0908) from Mycobacterium tuberculosis H37Rv. Radioactive transport assays revealed that CtpE is a Ca2+-specific transporter. Ca2+ deficiency increased expression of ctpE, resulting in increased 45Ca2+ accumulation in cells. ctpE is a gene that is part of an operon, which is negatively regulated by Ca2+. The ctpE mutant also showed hypersensitivity to polymyxin B, increased biofilm formation, and higher cell aggregation, indicating cell envelope defects. Our work establishes, for the first time, the presence of Ca2+ uptake pumps of the energy-dependent P-type ATPase superfamily in bacteria and also implicates that intracellular Ca2+ is essential for growth and cell envelope integrity in M. smegmatis.