Radiological Assessment Models Research Articles

Study on radiological environmental impact assessment of nuclear fuel cycle facilities

The radiological assessment model REIA 1.0 is established to assess the radio-logical environmental impact of radioactive airborne effluents released from nuclear fuel cycle facilities. It is based on the double Gaussian probability distribution function model and considers the wind pendulum effect of the long-term diffusion factor. The simulation results of the REIA 1.0 model are compared with those of the AERMOD-VIEW model and radiation environmental monitoring results of nuclear fuel cycle facilities. The results are: using the REIA 1.0 and AERMOD-VIEW models, the relative deviations of simulation results are less than 33.33% in 192 subregions. Except for three points, the relative deviations are less than 20%, the simulated results are consistent with the radiation environmental monitoring results in seven sites using the REIA 1.0 model, and the REIA 1.0 model can characterize the incremental contribution of radionuclide concentration in the air caused by the radioactive airborne effluents from nuclear fuel cycle facilities. It can effectively assess the radiological environmental impact of nuclear fuel cycle facilities.

Radiological Impact Assessment of Acute Tritium Releases in Environment—A Soil Dynamic Model

Radiological and environmental impact assessment models are important tools that support nuclear safety. The present study summarizes the upgrades of a research-grade model (CROPTRIT) with an emphasis on a soil submodel and the balance between air-to-plant and soil-to-plant pathways, together with the needs that must be accomplished by an operational model in order to be applied to nuclear facilities involving large tritium loads.

Identification of areas of interest for radiological impact assessments in an evolving landscape context

Regulations concerning potential future health impacts of the final disposal of radioactive wastes in geological disposal facilities are written in terms of annual dose to individuals who are representative of small groups living in the landscape in the vicinity of the repository site. As disposal programmes in Sweden and Finland have progressed towards licensing and construction, so too has detail describing the state and evolution of surface biosphere and the landscape around the proposed disposal sites increased. Simple and generic biosphere dose assessment models in early iterations have grown in complexity with increasing site-specific detail that aims to capture the radiologically significant features of the landscape into which future releases of radionuclides might credibly occur. Current dose assessment models used in support of license applications for disposal programmes in Sweden and Finland are highly complex and their application consequently lacks transparency. An alternative simpler approach to characterising landscape objects for dose assessment models would be beneficial in that it would offer an additional line of reasoning and would add clarity, thereby supporting the decision-making process of the regulatory authorities.In the context of coastal Fennoscandia, landscape change is relatively rapid and dramatic with post-glacial landrise transforming areas of the coastal seabed into terrestrial ecosystems over a period of a few thousand years, global sea level rise notwithstanding. The locations of the geosphere-biosphere interfaces for deep geologic disposal can be estimated with some precision but the nature of the receiving ecosystems at the time of the release is less certain.The approach described here provides a statistical quantification of key morphological characteristics of areas in the landscape where doses could arise, so as to better express uncertainties in dose modelling. The proposed method assumes that the variation in the morphology of potential release locations can be described by the variation in landscape objects seen in the landscape on a wider scale, providing a statistical description of the possible landscape objects, so allowing a more comprehensive range of potential future evolutions to be addressed.Our understanding of the evolution of the landscape, based on the kinds of terrain and ecosystem development models used by POSIVA in Finland and SKB in Sweden, suggests that objects identified in present-day maps can be used as analogues for a statistical characterisation of objects in the future landscape; objects identified in the observed topography and bathymetry can therefore serve as the basis for the statistical description of landscape dose objects over the period during which doses are likely to arise. Using digital elevation models around a disposal site in Finland, we show that the statistical descriptions of landscape dose objects at three times over a period of 10 kyear of the evolved landscape are sufficiently similar to establish the suitability of the approach.The aim of this statistical analysis is to supplement current methods for defining radiological assessment models so as to provide additional numerical support to both the simpler and more complex methods employed by implementors and regulators. The method has been developed in the context of the Swedish and Finnish regulatory review process and is referred to in the IAEA's revised BIOMASS methodology. We briefly address how the method might be applied in other landscape contexts.

Ensuring robust radiological risk assessment for wildlife: insights from the International Atomic Energy Agency EMRAS and MODARIA programmes

In response to changing international recommendations and national requirements, a number of assessment approaches, and associated tools and models, have been developed over the last circa 20 years to assess radiological risk to wildlife. In this paper, we summarise international intercomparison exercises and scenario applications of available radiological assessment models for wildlife to aid future model users and those such as regulators who interpret assessments. Through our studies, we have assessed the fitness for purpose of various models and tools, identified the major sources of uncertainty and made recommendations on how the models and tools can best be applied to suit the purposes of an assessment. We conclude that the commonly used tiered or graded assessment tools are generally fit for purpose for conducting screening-level assessments of radiological impacts to wildlife. Radiological protection of the environment (or wildlife) is still a relatively new development within the overall system of radiation protection and environmental assessment approaches are continuing to develop. Given that some new/developing approaches differ considerably from the more established models/tools and there is an increasing international interest in developing approaches that support the effective regulation of multiple stressors (including radiation), we recommend the continuation of coordinated international programmes for model development, intercomparison and scenario testing.

Consequences of marine ecological environment and our preparedness for Fukushima radioactive wastewaterdischarge into the ocean

<p indent="0mm">Ten years after the Fukushima nuclear accident (FNA), Japan announced the planned discharge of over one million tons of Fukushima radioactive wastewater (FRW) into the Pacific Ocean in two years. This decision regarding FRW disposal has aroused worldwide concerns and public fears, which may be exacerbated by reputational damage and the lack of a clear public understanding of the possible adverse impacts of the FRW. As one of the countries surrounding the Pacific Ocean, China is a stakeholder in this decision regarding the FRW disposal. In this study, we compared the FRW source and its associated radionuclide components with the liquid effluent from routine operation of the nuclear power plant and its associated radionuclides. The activity concentrations of 13 radionuclides in the pre- and post-treated FRW by the Advanced Liquid Processing Systems (ALPS) were quantitatively compared with limits for radionuclide concentrations required by Japan law, guidance levels for radionuclides in drinking water provided by the World Health Organization (WHO), and baseline concentrations of radionuclides in surface seawater from the Pacific Ocean before the FNA. Sediment-seawater distribution coefficients and bioconcentration factors are also shown to provide insights into the mobility and biological availability of radionuclides derived from the FRW in the marine environment. Although 62 radionuclides can be recovered from the FRW by ALPS according to a report from the Tokyo Electric Power Company (TEPCO), a large amount of ³H remains in the ALPS-treated FRW. The total amount of ³H in the ALPS-treated FRW was approximately <sc>8.6×10¹⁴ Bq</sc> (by October 31, 2019), with an average concentration of <sc>7.3×10⁵ Bq/L,</sc> higher than the concentration limit <sc>(6×10⁴ Bq/L)</sc> required by Japan law and guidance level <sc>(10⁴ Bq/L)</sc> provided by the WHO. The amount of ³H in the ALPS-treated FRW <sc>(8.6×10¹⁴ Bq</sc> by October 31, 2019) is continually increasing, and is already higher than the amount of ³H (3×10¹⁴<sc>‒7×10¹⁴ Bq)</sc> released into the Pacific Ocean immediately after the FNA. Additionally, other radionuclides (e.g., ¹⁴C, ⁹⁰Sr, ¹²⁹I, etc.) in the ALPS-treated FRW with high bioconcentration factors and high activity-dose conversion factors relative to ³H should also be carefully monitored and evaluated. The measured results provided by the TEPCO indicated that ~70% of the current ALPS-treated FRW should be repurified to reduce concentrations of other radionuclides to meet Japan’s legal requirements. Despite several unresolved factors (e.g., the FRW source terms, discharging plan, hydrodynamic and biogeochemical processes, etc.) simultaneously influencing the fate of FRW in the marine environment, we qualitatively described the hydrodynamically driven passive transport pathway and the biologically driven active transport pathway of the FRW. The transport of the FRW should be comprehensively investigated from the perspective of physical-biogeochemical processes at multiple scales (e.g., large-scale wind-driven circulation, mesoscale eddies, small-scale turbulence) and three-dimensional (e.g., vertical and horizontal vectors) oceans. Key gateways and transport pathways relevant to the FRW entry into the China seas have been suggested to include the Luzon Strait, the outer continental shelf and cross-shelf penetrating fronts in the East China Sea, the Yellow Sea Warm Current, and the Korean Coastal Current. Under specific conditions, the neglected biologically driven active transport pathway may significantly accelerate transport speed for the FRW-derived radionuclides via migratory animals (e.g., Pacific bluefin tuna) and may impose relatively high radiological risk to humans via seafood consumption. Finally, the consequences of marine ecological environment and our preparedness for the FRW release were discussed from the perspectives of total radioactivity, radionuclide components in the FRW, transport pathways of the FRW, and enhancing capacity to meet radiological risk assessment needs. Nuclear power plants located near the coastal seas are gradually developing in China and play a significant role in China’s national strategy of “Carbon Neutrality”. Technical systems of measurement, tracer, and assessment of radionuclides in the marine environments should be given more attention and be continually enhanced in line with the development of nuclear power plants. Several directions including extremely low minimum detection activity for the analytical methods of radionuclides, buoy-based online and real-time measurement technology for marine radioactivity, construction and validation of numerical models for marine radioactivity, key marine biogeochemical processes for radionuclides, radiation dose-effect for marine biotas, radiological assessment models, and remediation technology for radionuclides in marine environments are emphasized as key technologies in nuclear emergency preparedness to protect marine environment security.

Client perceptions of the BreastScreen Australia remote radiology assessment model

BackgroundTelehealth and teleradiology are increasingly used around the world to facilitate health care provision when the health care provider and clients are separated by distance. The BreastScreen Australia Remote Radiology Assessment Model (RRAM) is an initiative developed to address the challenges of inadequate access to a local radiological workforce in regional Australia. With the growth in telehealth innovations more broadly, the RRAM represents a departure from the traditional onsite model where a radiologist would be co-located with practice staff during assessment clinics. Understanding client satisfaction is an important consideration with new models. This article explores client perceptions of the RRAM including awareness, satisfaction with experiences, confidence in the quality of care being received, and preferences regarding models of service delivery.MethodsClients in four BreastScreen services across three Australian states and territories were invited to provide feedback on their experiences of the RRAM. Brief face-to-face interviews based on a survey were conducted at the conclusion of assessment clinic visits. Clients also provided feedback through surveys completed and returned by post, and online.Results144 clients completed the survey regarding their experiences of the RRAM. The majority were aged between 50 and 59 years (55/144, 38.2%). Most had attended a BreastScreen service for either screening or assessment on a total of two to five occasions (85/142, 59.9%) in the past. Nearly all women who attended a RRAM clinic expressed satisfaction with their experience (142/143, 99.3%). Clients were aware that the radiologist was working from another location (131/143, 91.6%) and the majority believed there wouldn’t be any difference in the care they received between the RRAM and the onsite model (120/142, 84.5%). Clients generally had no particular preference for either the onsite or RRAM model of service delivery.ConclusionsClients’ high satisfaction with their clinic experiences, high confidence in care being received, and the majority having no preference for either the onsite or remote model indicates their acceptance of the RRAM. Client acceptance of the model supports continuation of the RRAM at these sites and expansion. Findings may inform future telehealth innovations where key health care team members are working remotely.

Study of Radiological Assessment Models for Contaminated Soil, Buildings, and Outdoor Surfaces: Overview, Comparison, Similarity with Chemical Models, Challenges, and Lessons Learned.

A research project was conducted by the United States Environmental Protection Agency's (EPA) Superfund remedial program to study radiological assessment models used for contaminated sites. Several models developed by regulatory agencies in different countries are studied to present overview and comparisons. These models are recommended by governmental agencies for radiological assessment of contaminated soil, inside buildings, and outdoor surfaces. The project also addressed the methodological consistency between the EPA and the United Kingdom Environment Agency (UK EA) for radiological and chemical assessment models. The main purpose of this project is to establish a common ground for cooperation between regulatory agencies by facilitating better understanding of each agency's modeling approach and identifying the similarities and differences between these agencies. The project produced five reports that are published at the EPA's website. This paper summarizes the content of each report and presents results of a survey distributed electronically following an EPA webinar about the research projects, including the familiarity of the respondents with these models. All findings were statistically analyzed.

Evaluating the quality and safety of the BreastScreen remote radiology assessment model of service delivery in Australia

Introduction Breast cancer is the most commonly diagnosed cancer in Australian women. Given the diverse geography and populations within Australia, the ability to offer a telemedicine-supported breast screening and assessment service may increase access. The aim of this study was to assess clinical outcomes of a telemedicine-based remote radiology assessment service delivery model for detecting breast cancer in regional Australian women compared to the traditional radiologist onsite model. Methods This study was a pre–post intervention study using de-identified administrative data. Data were collected from seven sites across three health jurisdictions within Australia. There were a total of 21,117 assessment visits, with 10,508 (49.8%) pre- and 10,609 (50.2%) post-remote model implementation. Of the 10,609 post-remote model visits, 3,904 (36.8%) were under the remote model. The main outcome was cancer detection, split into any cancer, any invasive cancer or any small invasive cancer. Timeliness of assessment was also examined. Results After adjusting for multiple factors, there were no statistically significant differences in cancer detection rates between the remote and onsite models (adjusted odds ratio (AOR) = 1.02, 95% CI 0.86–1.19, n.s.). Implementing the remote assessment model had statistically significant positive effects on the timeliness of assessment (AOR = 0.68, 95% CI 0.59–0.77, p < 0.001). Discussion This study found the remote model delivers safe and high-quality assessment services, with equivalent rates of cancer detection and improved timeliness of assessment when compared to the traditional onsite model. Careful monitoring and ongoing evaluation of any health-service model is important for ongoing safety, efficiency and acceptability.

\u201cFrom the technology came the idea\u201d: safe implementation and operation of a high quality teleradiology model increasing access to timely breast cancer assessment services for women in rural Australia

Breast cancer is the most commonly diagnosed cancer in Australian women. Providing timely diagnostic assessment services for screen-detected abnormalities is a core quality indicator of the population-based screening program provided by BreastScreen Australia. However, a shortage of local and locum radiologists with availability and appropriate experience in breast work to attend onsite assessment clinics, limits capacity of services to offer assessment appointments to women in some regional centres. In response to identified need, local service staff developed the remote radiology assessment model for service delivery. This study investigated important factors for establishing the model, the challenges and enablers of successful implementation and operation of the model, and factors important in the provision of a model considered safe and acceptable by service providers.MethodsSemi-structured interviews were conducted with service providers at four assessment services, across three jurisdictions in Australia. Service providers involved in implementation and operation of the model at the service and jurisdictional level were invited to participate. A social constructivist approach informed the analysis. Deductive analysis was initially undertaken, using the interview questions as a classifying framework. Subsequently, inductive thematic analysis was employed by the research team. Together, the coding team aggregated the codes into overarching themes.Results55 service providers participated in interviews. Consistently reported enablers for the safe implementation and operation of a remote radiology assessment clinic included: clinical governance support; ability to adapt; strong teamwork, trust and communication; and, adequate technical support and equipment. Challenges mostly related to technology and internet (speed/bandwidth), and maintenance of relationships within the group.ConclusionsUnderstanding the key factors for supporting innovation, and implementing new and safe models of service delivery that incorporate telemedicine, will become increasingly important as technology evolves and becomes more accessible. It is possible to take proposed telemedicine solutions initiated by frontline workers and operationalise them safely and successfully: (i) through strong collaborative relationships that are inclusive of key experts; (ii) with clear guidance from overarching bodies with some flexibility for adapting to local contexts; (iii) through establishment of robust teamwork, trust and communication; and, (iv) with appropriate equipment and technical support.

Operationalising an ensemble approach in the description of uncertainty in atmospheric dispersion modelling and an emergency response

Uncertainties were propagated through the chain of atmospheric dispersion and radiological assessment models based on an ensemble approach for a range of scenarios. It was apparent that the time taken to complete model runs, ranging from several hours to a few tens of hours, was not appropriate for an emergency response. Thus, for an operational method, there was a requirement to reduce the number of ensemble members and/or reduce model run time for a single ensemble member, such that a measure of uncertainty may be obtained within the timeframe of one hour, but without significant detriment to the model endpoints derived, the uncertainty estimated and the radiation protection advice inferred. This study proposes recommendations for operationalising an ensemble approach used in the description of uncertainty in atmospheric dispersion modelling and an emergency response.

Analytical techniques for charactering radioactive particles deposited in the environment

Since 1945, a series of nuclear and radiological sources have contributed to the release of radioactive particles containing refractory elements into the environment. Several years of research have demonstrated that the particle composition will depend on the source, while the release scenarios will influence particle properties of relevance for environmental transfer. Radioactive particles can also carry sufficient amount of radioactivity (MBq) and represent point sources of radiological concern. Most radiological assessment models, however, are based on bulk concentrations, assuming that radionuclides in the environment are evenly distributed. In contrast, radioactive particles and thereby doses are unevenly distributed, while leaching of radionuclides from particles prior to measurements can be partial, potentially leading to underestimation of inventories. For areas affected by particle contamination, information on particle characteristics controlling the particle weathering rates and remobilization of particle associated radionuclides will therefore be essential to reduce the overall uncertainties of the impact assessments. The present paper will focus on analytical strategies, from screening techniques applicable for identifying hot spots in the field, fractionation techniques and single particle extraction techniques as a preparatory mean to apply non-destructive solid state speciation techniques, till leaching techniques applied sequentially to obtain information on binding mechanisms, mobility and potential bioavailability. Thus, a combination of techniques should be utilized to characterize radioactive particles in order to improve environmental assessments for areas affected by radioactive particle fallout.

Lung cancer screening: nodule identification and characterization

The accurate identification and characterization of small pulmonary nodules at low-dose CT is an essential requirement for the implementation of effective lung cancer screening. Individual reader detection performance is influenced by nodule characteristics and technical CT parameters but can be improved by training, the application of CT techniques, and by computer-aided techniques. However, the evaluation of nodule detection in lung cancer screening trials differs from the assessment of individual readers as it incorporates multiple readers, their inter-observer variability, reporting thresholds, and reflects the program accuracy in identifying lung cancer. Understanding detection and interpretation errors in screening trials aids in the implementation of lung cancer screening in clinical practice. Indeed, as CT screening moves to ever lower radiation doses, radiologists must be cognisant of new technical challenges in nodule assessment. Screen detected lung cancers demonstrate distinct morphological features from incidentally or symptomatically detected lung cancers. Hence characterization of screen detected nodules requires an awareness of emerging concepts in early lung cancer appearances and their impact on radiological assessment and malignancy prediction models. Ultimately many nodules remain indeterminate, but further imaging evaluation can be appropriate with judicious utilization of contrast enhanced CT or MRI techniques or functional evaluation by PET-CT.

Effects of radionuclide and rainfall characteristics on field loss parameters of grass

The decrease of foliar activity in vegetation after its initial contamination by foliar deposition is termed “field loss” (Chamberlain, 1970). This work investigated further laboratory data concerning field loss of 134Cs, 137Cs, 85Sr, 133Ba and 123 m Te deposited on grassland (Madoz-Escande et al., 2005). Treatments consisted in rainfall scenarios cumulating 14 mm per week, combining two levels of intensity (8 or 30 mm/h) and two levels of frequency/precocity (late once or early twice-a-week). The time course of field loss was monitored in the edible tissues which were sampled by mowing between the rainfalls. Data were analyzed with an offset exponential loss model which is applicable to chronic contamination and is consistent with approaches adopted in radiological assessment models. Its parameters were estimated by the maximum-likelihood method, and their accuracy was determined by nonparametric boostrap. Radionuclide and rainfall conditions significantly affected the estimated rate ( λ 1) and extent ( A 1) of field loss. Field loss rate ( λ 1) and nonentrainable fraction (1 − A 1) varied by a factor 1.5–3. Cesium was very mobile but persistent. On the contrary Tellerium was found less labile, but eventually was almost completely eliminated. Strontium and Barium had intermediate behaviors. Field loss was more efficient for moderate late once-a-week rainfalls (8 mm/h). Higher rainfall intensity reduced more the radionuclides losses than higher rainfall frequency/precocity. This paper reports statistically relevant effects that should be considered for more realistic assessments.

Influence of crop types and soil properties on radionuclide soil-to-plant transfer factors in tropical and subtropical environments

This paper presents a descriptive statistical analysis of radionuclide soil-to-plant transfer factors ( Fv ) for tropical and subtropical environments. These values were collected from previous databases and standard publications with the objective of contributing to the IAEA Technical Report Series: Handbook of parameter values for the prediction of radionuclide transfer to humans in terrestrial and freshwater environments. More than 2200 Fv values of different radionuclides were gathered and arranged into specific databases, detailing relevant information regarding the environments where this parameter was calculated. This study explores the dependence of Fv values to crop types, and soil properties. The wide variability and uncertainty observed in calculated Fv values were considerably reduced when the data was independently grouped into clusters containing the same radionuclide/plant group/soil type combinations. For each cluster the principal statistical quantities were determined. Using these quantities, the Fv distributions of each data set was explored. Fv probability distribution is discussed to clarify the use of this empirical parameter in radioecological and radiological assessment models.

A model testing study for the transfer of radioactivity to fruit

This paper compares predictions of the foodchain model SPADE with experimental data for the transfer of 134Cs and 85Sr to strawberry plants following acute foliar and soil contamination. The transfer pathways considered in this exercise included direct deposition to fruit, leaf-to-fruit, soil-to-leaf and soil-to-fruit transfers. Following foliar contamination, the difference between predicted and measured radionuclide activity values varied between a factor of 0.5–10 for fruit and 4.5–7 for leaf. Following soil contamination, the difference between predicted and measured values varied between a factor of 3–74 for fruit and 32–44 for leaf. In all cases the difference between measured and predicted values was smaller for 85Sr than 134Cs. Measured and predicted activities were higher for leaf than fruit. Both measured and predicted 134Cs concentrations in fruit and leaf are higher when deposition occurs at ripening than at anthesis. These results confirm the need for more data on fruit, even for Cs and Sr, to support models in predicting the transfer of radionuclides to fruit crops. Ongoing research projects funded by the UK Food Standards Agency aim to provide some data on radionuclide transfer to herbaceous, shrub and tree fruits, which will help improve radiological assessment models in order to provide better protection for consumers.

Testing of a foodchain model using Chernobyl 137Cs fallout data and considering the effect of countermeasures

Chernobyl 137Cs fallout data obtained during the period 1986–1996 from the most contaminated area in Russia were used within the IAEA BIOMASS programme to test the reliability of radiological assessment models. This model-testing scenario included information and data on countermeasures that were applied in the test area after the accident. This paper presents the predictions of the terrestrial foodchain model SPADE that was used in this model-testing exercise. SPADE predictions compared reasonably well with test data except for pigs and wild berries where differences were up to a factor of 50 and 200, respectively. Estimated intake of 137Cs and ingestion dose by adult men and women living in the test area compared favourably with the test data. Overall, SPADE proved to be capable of simulating agricultural countermeasures and their effectiveness. Modelling of countermeasures was found to be a complex process with large uncertainties regarding their ‘real’ implementation and effectiveness. The lessons learned from this exercise will be valuable in making future dose assessments/reconstructions involving countermeasures with improved results.

Optimisation of41Ar environmental monitoring to provide a validation of radiological assessment models

The aerial discharges of particulate matter, from Sellafield, have declined by more than three orders of magnitude, since their peak in the mid 1970s, as a result of back-fitting abatement plant to the older installations. The decline in the level of particulates has led to the volatile and inert nuclides being the main contributors to the critical group dose. Of these 41 Ar, from the Calder Hall reactors, dominates with an assessed contribution of 42 µSv a-1 out of a total critical group dose of 65 µSv a-1 from both power generation and reprocessing discharges during 1999. This predominance has led to a requirement for field validation of the assessed dose. A programme of field measurements, using a sodium iodide spectrometer, calibrated to measure the external dose rate, has been carried out to determine the 41 Ar gamma flux at the critical group location. Comprehensive meteorological measurements were correlated with 41 Ar emission rates and gamma flux measurements. The resulting database of measurements has provided an extensive validation toolkit with which to determine the accuracy of the dose predictions from the radiological assessment models used by both industry and the UK regulators. This paper presents the results of the dose rate measurements of 41 Ar, together with a comparison of both long- and short-term dose rate predictions from a number of radiological assessment models. The relative performance of the models has been tested in a variety of meteorological stability conditions and discharge scenarios.

A study on transfer factors of 60Co and 65Zn from soil to plants in the tropical environment of Bangladesh.

Soil to plant transfer factor (TF) of 60Co and 65Zn was determined from radioisotope experiments on plants grown in pots under outdoor ambient tropical conditions for three growing seasons (1995-1998). The TFs were obtained for different plants/crops such as, rice, bean, peanuts pineapple, cabbage, tomato, spinach and grass. The average TF values of 60Co are found to be 0.087. 0.15, 0.12, 0.67, 0.28, 0.79, 1.03 and 0.34 respectively for the above mentioned plants/crops. In case of 65Zn, the average TF values are found to be 2.24, 1.17. 0.89, 1.09, 0.78, 1.34, 2.92 and 1.78, respectively, for the above mentioned plants/crops. The data will be useful to assess the radiation exposure to man associated with the releases of radionuclides from nuclear facilities by means of radiological assessment models that require transfer factors as input parameters to predict the contamination of radionuclides in foodchain.

Determination of soil-to-plant transfer factors of 137Cs and 90Sr in the tropical environment of Bangladesh.

Soil-to-plant transfer factors (TF) of 137Cs and 90Sr have been determined for different plants/crops, such as rice, beans, peanuts, pineapple, cabbage, tomato, spinach and grass. They were obtained from radioisotope experiments on plants grown in pots under outdoor ambient tropical conditions for three growing seasons (1994-1996). In the case of 137Cs and concerning the above mentioned plants/crops, the average TFs were found to be 0.28, 0.25, 0.77, 0.19, 0.23, 0.28, 0.59 and 0.18, respectively. In the case of 90Sr, the average TFs were found to be 0.82, 0.51, 0.20, 0.82, 0.69, 0.59, 0.91 and 0.84, respectively. A minor seasonal variation was observed. This study provides a database of TFs for tropical environments to be used, e.g., for radiological safety assessment models.

Data quality and validation of radiological assessment models.

Simulation models must be tested against measurements before their predictions can be viewed as reliable. However, having data to test all pathways in a model is rare, and finding data that were collected for the purpose of model testing is even rarer. Thus modelers must take every opportunity to test portions of their models with data obtained under less than ideal circumstances. With careful preparation of the data and a thorough understanding of the data requirements of the model, the success of the test can be assured. Monitoring data collected after the Chernobyl reactor accident were used for model testing in two international studies, the Biospheric Model Validation Study and the Validation of Environmental Model Predictions. Based on these experiences, this paper describes the data requirements of validation, the validation of models with less than ideal data, the value of good data, the role of modeling in improving the quality of data and, most importantly, ways to improve collection and preparation of data to assist further validation. Although the examples are specific to radiological assessment models, the principles of data collection and preparation herein may be applied to testing all simulation models.