Table of contents

Recent findings related to childhood leukaemia incidence near nuclear installations have raised questions which can be answered neither by current knowledge on radiation risk nor by other established risk factors. In 2012, a workshop was organised on this topic with two objectives: (a) review of results and discussion of methodological limitations of studies near nuclear installations; (b) identification of directions for future research into the causes and pathogenesis of childhood leukaemia. The workshop gathered 42 participants from different disciplines, extending widely outside of the radiation protection field. Regarding the proximity of nuclear installations, the need for continuous surveillance of childhood leukaemia incidence was highlighted, including a better characterisation of the local population. The creation of collaborative working groups was recommended for consistency in methodologies and the possibility of combining data for future analyses. Regarding the causes of childhood leukaemia, major fields of research were discussed (environmental risk factors, genetics, infections, immunity, stem cells, experimental research). The need for multidisciplinary collaboration in developing research activities was underlined, including the prevalence of potential predisposition markers and investigating further the infectious aetiology hypothesis. Animal studies and genetic/epigenetic approaches appear of great interest. Routes for future research were pointed out.

Measurements made in situ with gamma detectors and ex situ measurements of soil samples in a laboratory can have complementary roles in the assessment of radioactively contaminated land on decommissioning nuclear sites. Both in situ and ex situ methods were used to characterize ¹³⁷Cs contamination within an area at the Dounreay site in Scotland. The systematic difference (bias) between estimates of the mean activity concentration was found to be non-significant when in situ measurements were interpreted using a linear depth model, based on ex situ measurements made at two different depths. An established method of evaluating the random components of measurement uncertainty was used. The random component of analytical uncertainty in the in situ measurements, made in field conditions, was found to exceed that for the ex situ measurements, made in the controlled conditions of a laboratory. However, contamination by the target radionuclide was found to be heterogeneous over small spatial scales. This resulted in significantly higher levels of random sampling uncertainty in individual ex situ measurements. As in situ measurements are substantially less costly, a greater number of measurements can be made, which potentially reduces the uncertainty on the mean. Providing the depth profile of contaminants can be modelled with confidence, this can enable estimates of mean activity concentration over an averaging area to be made with lower overall uncertainties than are possible using ex situ methods.

Monte Carlo calculations were used to investigate the efficiency of radiation protection equipment in reducing eye and whole body doses during fluoroscopically guided interventional procedures. Eye lens doses were determined considering different models of eyewear with various shapes, sizes and lead thickness. The origin of scattered radiation reaching the eyes was also assessed to explain the variation in the protection efficiency of the different eyewear models with exposure conditions. The work also investigates the variation of eye and whole body doses with ceiling-suspended shields of various shapes and positioning. For all simulations, a broad spectrum of configurations typical for most interventional procedures was considered. Calculations showed that 'wrap around' glasses are the most efficient eyewear models reducing, on average, the dose by 74% and 21% for the left and right eyes respectively. The air gap between the glasses and the eyes was found to be the primary source of scattered radiation reaching the eyes. The ceiling-suspended screens were more efficient when positioned close to the patient's skin and to the x-ray field. With the use of such shields, the H_p(10) values recorded at the collar, chest and waist level and the H_p(3) values for both eyes were reduced on average by 47%, 37%, 20% and 56% respectively. Finally, simulations proved that beam quality and lead thickness have little influence on eye dose while beam projection, the position and head orientation of the operator as well as the distance between the image detector and the patient are key parameters affecting eye and whole body doses.

In a previous study, the counting efficiency calibration was calculated for 36 computational mesh phantoms called MaMP and FeMP—Male and Female Mesh Phantoms, which span variations in height, weight and gender. They were created to be used in a sitting configuration WBC set-up using an HPGe detector. Now this work is extended to investigate the influence of body sizes and the position of the detector on the counting efficiency (CE) for a different counting geometry. This was done by creating a new set of MaMP and FeMP mesh phantoms lying on a reclining chair and by studying the variation of the counting efficiency using a NaI(Tl) detector for the WBC set-up of SCK-CEN. The deviation of the CE due to the detector's position with respect to the phantom was investigated. Correlations were also studied for CE as a function of trunk volume, waist–hips ratio (WHR) and waist–chest ratio (WCR) for different mesh phantoms.

The upward migration of radionuclides in the ²³⁸U decay series in soils and their uptake by plants is of interest in various contexts, including the geological disposal of radioactive waste and the remediation of former sites of uranium mining and milling. In order to investigate the likely patterns of behaviour of ²³⁸U-series radionuclides being transported upward through the soil column, a detailed soil–plant model originally developed for studying the behaviour of ⁷⁹Se in soil–plant systems has been adapted to make it applicable to the ²³⁸U series. By undertaking a reference case simulation and a series of sensitivity studies, it has been found that a wide variety of behaviour can be exhibited by radionuclides in the ²³⁸U decay chain in soils, even when the source term is limited to being a constant flux of either ²³⁸U or ²²⁶Ra. Hydrological conditions are a primary factor, both in respect of the overall advective flow deeper in the soil, which controls the rate of upward migration, and in the influence of seasonally changing flow directions closer to the soil surface, which can result in the accumulation of radionuclides at specific depths irrespective of changes in sorption between the oxic and anoxic regions of the soil. However, such changes in sorption can also be significant in controlling the degree of accumulation that occurs. This importance of seasonally varying factors in controlling radionuclide transport in soils even in very long-term simulations is a strong argument against the use of annually averaged parameters in long-term assessment models.

With a water table that was simulated to fluctuate seasonally from a substantial depth in soil to the surface soil layer, the timing of such variations in relation to the period of plant growth was found to have a major impact on the degree of uptake of radionuclides by plant roots.

In long-term safety assessment studies it has sometimes been the practice to model the transport of ²²⁶Ra in soil, but to assume that both ²¹⁰Pb and ²¹⁰Po can be treated as being present in secular equilibrium with the ²²⁶Ra. This simplification is not always appropriate. Where geochemical conditions are such that the ²²⁶Ra migrates upward in the soil column faster than ²¹⁰Pb and ²¹⁰Po, disequilibrium is not a significant issue, as the ²²⁶Ra supports ²¹⁰Pb and ²¹⁰Po at concentrations somewhat below those estimated on the basis of assumed secular equilibrium. However, for low, but realistic, values of the distribution coefficients for ²¹⁰Pb and ²¹⁰Po and high, but realistic, distribution coefficients for ²²⁶Ra, the ²¹⁰Pb and ²¹⁰Po can reach the surface soil in high concentrations that are not locally supported by ²²⁶Ra. This means that models based on the assumption of secular equilibrium should not be employed without a careful consideration of the hydrological and hydrochemical situation of interest.

Despite several decades of studies on the risk assessment and risk perception of ionising radiation, risk management of radioactive materials remains a challenging issue. This is also true for wastes containing technologically enhanced naturally occurring radioactive materials. The present work focuses on the underlying reasons for communication problems between experts and affected members of the public. Exploring the case of a German remediation site with residual radioactive contamination in a residential area, the experts' as well as the residents' perspectives were studied by conducting qualitative interviews. Our results indicate a variety of reasons for communication problems on different levels of risk management and risk communication: the regulatory, the communicative and the moral levels. In the observed case, four salient causes for problems in risk communication and risk management emerged: the mismatch in understanding the residents' values, the issue of risk communication in an unforeseen situation, the problem of the regulatory gap between radiation protection and soil protection in regard to legacies with naturally occurring radioactive material in Germany, and the challenge of communicating a highly complex scientific issue to non-scientists. Moreover, one (at least partial) solution could be seen: the introduction of an external mediator. The results indicate that coordination of different health and environment protection disciplines—in this case radiation protection relating to soil protection—is possible and urgently needed. The opportunity to put, at least natural, radioactive material in line with other conventional industrial materials should be taken.

The aim of this study was to estimate cancer mortality and incidence risk associated with external radiation exposure in the BNFL cohort of nuclear workers and to determine if these risks are modified by potential for internal exposure. The cohort comprised 64 956 individuals who were employed at the four study sites between 1946 and 2002, followed up to 2005. External radiation exposures as measured by personal dosimeters (generally 'film badges') were available for 42 431 individuals classified as 'radiation workers'. Poisson regression models were used to investigate cancer mortality and incidence in relation to cumulative external radiation exposure using relative risk models. The cohort showed the expected 'healthy worker' effect. This analysis found an increased risk of all cancers associated with external occupational radiation exposure (ERR/Gy = 0.34 90% CI: 0.07; 0.64), with significant excess risks observed for all solid cancers (ERR/Gy = 0.29 90% CI: 0.02; 0.59) and leukaemia excluding CLL (ERR/Gy = 2.60 90% CI: 0.28; 7.01). The overall cancer risk estimates are consistent with values used by national and international bodies in setting radiation protection standards. The slopes of the dose response relationships for all cancer mortality and incidence were found to be significantly less steep for workers exposed to both external radiation and potentially to internal radiation (ERR/Gy = 0.09 90% CI: −0.17; 0.39) when compared to those workers only exposed to external radiation (ERR/Gy = 1.14 90% CI: 0.49; 1.89). Analyses of individual cancer types indicate that this overall result is mainly driven by that for digestive cancers and in particular cancers of the oesophagus. Categorical analyses also revealed that the difference in the dose response relationship between the two groups is only apparent for those exposed to cumulative external doses in excess of 200 mGy. Such differences have also been observed for non-cancer mortality outcomes in this cohort. Further work is required to explain these differences; for example, whether they may result from confounding by internal organ dose or lifestyle factors associated with socio-economic status.

This paper summarises work undertaken on behalf of the Environment Agency for England to quantify uncertainties resulting from internal exposures to a number of radionuclides considered significant because of their anthropogenic origin, namely: ²³⁸U, ²²⁶Ra, ²³⁹Pu, ²⁴¹Am, ¹³⁷Cs, ⁹⁰Sr, ¹³¹I, ¹²⁹I and ³H. Uncertainties in the biokinetic models that are used to calculate the retention and excretion of radionuclides are derived in order to calculate distributions of effective dose per unit intake following their inhalation or ingestion by members of the UK public. The central values and ranges of the distributions are used to inform the derivation of uncertainty factors (UFs) for the different dose coefficients, which can be used to assess reliability. These represent uncertainties inherent in the structures of the biokinetic models and their parameter values. The inferred UF values are typically around 2–3 for ingestion and 2–6 for inhalation for all age groups, and are comparable to UF values inferred from published studies. It is instructive to consider these ranges alongside the likely levels of exposure that are expected from the radionuclides considered (the microsievert range) and the dose limit of planned exposures for members of the public (1000 μSv).

BABYSCAN, a whole body counter for small children with a detection limit for ¹³⁷Cs of better than 50 Bq/body, was developed, and the first unit has been installed at a hospital in Fukushima, to help families with small children who are very much concerned about internal exposures. The design principles, implementation details and the initial operating experience are described.

The performance of miniature CCD array spectroradiometers, which are widely used for the assessment of personal and environmental exposures, may be affected by variations in ambient temperature. The dark signal, spectral sensitivity and wavelength position of six different array spectroradiometer models, produced by two different manufacturers, were assessed in ambient temperatures ranging from 5 °C to 40 °C. The results are presented with a discussion of the practical implications for field measurements when the instruments are used outside of a temperature controlled environment.

Data related to radioactivity released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on 15 March 2011 gathered by residents of Miharu, Fukushima Prefecture, and by Tohoku University are presented. These data sets consist of (1) the earliest radiation monitoring by a Geiger counter in the town, (2) ratios of radioactivity between ¹³²Te and ¹³⁷Cs for a wide area between Fukushima and Tokyo, (3) radiation measurement of soil samples collected from 18 school grounds, and (4) external radiation exposure of 1400 students using OSL badges. By combining and analysing these various data sets, a curve for the cumulative total external exposure as a function of time, with 16 : 00 h on 15 March 2011 being time zero, is obtained. The average cumulative external dosage is estimated to be 10 mSv (σ = 4.2 mSv) over 10 years. In addition, the initiative that the residents of Miharu took in response to the FDNPP accident, which became known as The Misho Project (MP), is documented; in particular, the time at which the municipality instructed the immediate ingestion of iodine tablets by those under the age of 40, 13 : 00 h on 15 March 2011, is assessed.

Real-time monitoring of the radiation doses received by interventional radiology (IR) staff has become highly desirable. However, occupational doses are rarely measured in real time, due to the lack of a feasible method for use in IR. Recently, the i2 system by RaySafe™ has been introduced to measure occupational exposure in IR in real time. The i2 system consists of several personal dosimeters (PDs) and a base station with a display and computer interfacing. We evaluated the fundamental performance (dose linearity, dose-rate dependence, angular dependence, batch uniformity and reproducibility) of the i2 system. The dose linearity of the i2 was excellent (R² = 1.00) The i2 exhibited slight dose-rate dependence (~20%) at very high dose rates (250 mGy h⁻¹). Little angular dependence (within 20%) was observed between 0° and ±45°, in either the vertical or horizontal direction. We also found that the PD was highly sensitive (about 200%) at angles behind it, e.g. 180°. However, this backscattered radiation is not a problem, in general, due to the placement of the i2 sensor (PD) on the lead apron. We conclude that the i2 system facilitates accurate real-time monitoring and management of occupational doses during IR.

The great benefit of ¹³¹I radionuclide treatment for differentiated thyroid cancer (DTC) was acknowledged by the long survival rate. The main requirements for ¹³¹I therapy in hospital were treatment facilities and a radiation safety plan that assured radiation protection and safety to patient, hospital worker, public, and environment. Objective: To introduce the concepts and methods of radiation safety design for a patient's room in a ¹³¹I treatment ward and a system of radioactive waste water management in hospital. Methods: The design was based on principles of external and internal radiation protection for unsealed source and radioactive waste management. Planning for treatment facilities was concluded from clinical evidence, physical and physiological information for ¹³¹I, radiation safety criteria, hospital resources and budget. The three phases of the working process were: construction, software development, and radiation safety assessment. Results: The ¹³¹I treatment facility and automatic radioactive waste water management system was completely implemented in 2009. The radiation waste water management system known as the 'Suandok Model' was highly recommended by the national regulator to hospitals who desire to provide ¹³¹I treatment for thyroid cancer. In 2011, the Nuclear Medicine Division, Chiang Mai University was rewarded by the national authority for a very good radiation practice in development of safe working conditions and environment. Conclusion: The Suandok Model was a facility design that fulfilled requirements for the safe use of high radiation ¹³¹I doses for thyroid cancer treatment in hospital. The facility presented in this study may not be suitable for all hospitals but the design concepts could be applied according to an individual hospital context and resources. People who use or gain benefit from radiation applications have to emphasise the responsibility to control and monitor radiation effects on individuals, communities and the environment.

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