Radiation Protection Dosimetry - recent issues

Introductory Remarks

Menzel, H., Schonbacher, H., Vylet, V., Ulrici, L., Rokni, S. — Mon, 16 Nov 2009 09:54:48 PST

Operational radiation protection in high-energy physics accelerators

Rokni, S. H., Fasso, A., Liu, J. C. — Mon, 16 Nov 2009 09:54:48 PST

An overview of operational radiation protection (RP) policies and practices at high-energy electron and proton accelerators used for physics research is presented. The different radiation fields and hazards typical of these facilities are described, as well as access control and radiation control systems. The implementation of an operational RP programme is illustrated, covering area and personnel classification and monitoring, radiation surveys, radiological environmental protection, management of induced radioactivity, radiological work planning and control, management of radioactive materials and wastes, facility dismantling and decommissioning, instrumentation and training.

Operational radiation protection in synchrotron light and free electron laser facilities

Liu, J. C., Rokni, S. H., Vylet, V. — Mon, 16 Nov 2009 09:54:48 PST

The third-generation synchrotron radiation (SR) facilities are storage ring-based facilities with many insertion devices and photon beamlines, and have low injection beam power, but extremely high stored beam power. The fourth-generation X-ray free electron laser (FEL) facilities are based on an electron Linac with a long undulator and have high injection beam power. Due to its electron and photon beam characteristics and modes of operation, storage ring and photon beamlines have unique safety aspects, which are the main subjects of this paper. The shielding design limits, operational modes and beam losses are reviewed. Shielding analysis (source terms and methodologies) and interlocked safety systems for storage ring and photon beamlines (including SR and gas bremsstrahlung) are described. Specific safety issues for storage ring top-off injection and FEL facilities are discussed. Operational safety programme elements, e.g. operation authorisation, commissioning, training and radiation measurements, for SR facilities are also presented.

Operational radiation protection issues specific to high-intensity beams

Nakashima, H. — Mon, 16 Nov 2009 09:54:48 PST

This paper describes operational radiation protection issues specific to high-intensity accelerators, aimed at the radiological safety of high-intensity accelerators during construction and operation. The paper is composed of chapters on safety characteristics, radiological safety design and safety management systems of high-intensity accelerators. The Japan Proton Accelerator Research Complex (J-PARC) is taken as a reference, because J-PARC was recently completed after collecting and referring to experiences with existing accelerator facilities all over the world.

Instrument response in complex radiation fields

Agosteo, S., Silari, M., Ulrici, L. — Mon, 16 Nov 2009 09:54:49 PST

This paper aims at giving an overview of the main issues for estimating the radiation protection quantities in complex radiation fields. The measurability (or non-measurability) of the radiation protection quantities is discussed together with the main approaches for their estimate. The main mechanisms through which the various components of complex radiation fields are generated are also outlined. The main instruments employed for estimating the radiation protection quantities are described and discussed together with their response. Finally, a practical example is given, by discussing the results of an inter-comparison exercise held at the Gesellschaft für Schwerionenforschung mbH in Darmstadt (Germany) in the framework of the COordinated Network for RAdiation Dosimetry project, funded by the European Commission.

Individual monitoring at accelerator centres

Wernli, C. — Mon, 16 Nov 2009 09:54:49 PST

The accurate determination of personal dose equivalent requires the proper use of appropriate radiological quantities and units, knowledge of the dose equivalent response of the personal dosemeters used and detailed information on the fluence as well as dose equivalent spectra at the workplaces. This information can then be used to select the appropriate dosemeters, to set up the optimum calibration conditions and to introduce, in case of need, normalisation factors for application in specific radiation fields. High-energy neutrons contribute significantly to the radiation fields around high-energy particle accelerators. Examples for procedures and methods to determine personal dose equivalent at accelerator centres are given.

High-level dosimetric methods

Schonbacher, H., Furstner, M., Vincke, H. — Mon, 16 Nov 2009 09:54:49 PST

This article gives an overview of selected high-dose dosimetric methods suitable for use in accelerators in research and medicine for reference, transfer and routine dosimetry. This comprises solid state, glass, plastic and liquid chemical systems as well as ionisation chambers and calorimeters. The dose covered varies from 0.1 Gy to the MGy range. A summary comparing the main characteristics of these dosemeters is also given.

Operational radiation protection in high-energy physics accelerators: implementation of ALARA in design and operation of accelerators

Fasso, A., Rokni, S. — Mon, 16 Nov 2009 09:54:49 PST

This paper considers the historical evolution of the concept of optimisation of radiation exposures, as commonly expressed by the acronym ALARA, and discusses its application to various aspects of radiation protection at high-energy accelerators.

Radiation safety system

Vylet, V., Liu, J. C., Walker, L. S. — Mon, 16 Nov 2009 09:54:49 PST

The goal of this work is to provide an overview of a Radiation safety system (RSS) designed for protection from prompt radiation hazard at accelerator facilities. RSS design parameters, functional requirements and constraints are derived from hazard analysis and risk assessment undertaken in the design phase of the facility. The two main subsystems of a RSS are access control system (ACS) and radiation control system (RCS). In this text, a common approach to risk assessment, typical components of ACS and RCS, desirable features and general design principles applied to RSS are described.

Understanding and characterisation of the risks to human health from exposure to low levels of radiation

Goodhead, D. T. — Mon, 16 Nov 2009 09:54:49 PST

Exposure to ionising radiation can lead to a wide variety of health effects. Cancer is judged to be the main risk from radiation at low doses and low dose rates, and controlling this risk has been the main factor in developing radiation protection practice. Conventional paradigms of radiobiology and radiation carcinogenesis have served to guide extrapolations of epidemiological data on exposed human populations, so as to estimate risks at low doses and low dose rates, to other types of ionising radiation and to non-uniform exposures. These paradigms are founded on a century of experimental and theoretical studies, but nevertheless there remain many uncertainties. Major assumptions and simplifications have been introduced to achieve a practical system of additive doses (and implied risks) for radiation protection. Advancing epidemiological studies and experimental research continue to reduce uncertainties in some areas while, in others, they raise new challenges to the generality and applicability of the conventional paradigms.

Radiation transport calculations and simulations

Fasso, A., Ferrari, A., Sala, P. R. — Mon, 16 Nov 2009 09:54:49 PST

This article is an introduction to the Monte Carlo method as used in particle transport. After a description at an elementary level of the mathematical basis of the method, the Boltzmann equation and its physical meaning are presented, followed by Monte Carlo integration and random sampling, and by a general description of the main aspects and components of a typical Monte Carlo particle transport code. In particular, the most common biasing techniques are described, as well as the concepts of estimator and detector. After a discussion of the different types of errors, the issue of quality assurance is briefly considered.

Programmes for the evaluation of the environmental impact

Vojtyla, P. — Mon, 16 Nov 2009 09:54:49 PST

The article provides an overview of the different components of programmes for the evaluation of the environmental impact of accelerator facilities. The starting point is the knowledge of radiation and radionuclides that may be encountered in the environment of accelerators. The second step is an efficient environmental monitoring programme suitable for the given source term. The results of the monitoring programme provide an input for models calculating the maximum effective dose received by members of the public, so expressing the dosimetric impact of the facility.

Radioactive waste management and decommissioning of accelerator facilities

Ulrici, L., Magistris, M. — Mon, 16 Nov 2009 09:54:49 PST

During the operation of high-energy accelerators, the interaction of radiation with matter can lead to the activation of the machine components and of the surrounding infrastructures. As a result of maintenance operation and during decommissioning of the installation, considerable amounts of radioactive waste are evacuated and shall be managed according to the radiation-protection legislation. This paper gives an overview of the current practices in radioactive waste management and decommissioning of accelerators.

Carbon-ion radiotherapy: clinical aspects and related dosimetry

Mon, 16 Nov 2009 09:54:49 PST

The features of relativistic carbon-ion beams are attractive from the viewpoint of radiotherapy. They exhibit not only a superior physical dose distribution but also an increase in biological efficiency with depth, because energy loss of the beams increases as they penetrate the body. This paper reviews clinical aspects of carbon-beam radiotherapy using the experience at the National Institute of Radiological Sciences. The paper also outlines the dosimetry related to carbon-beam radiotherapy, including absolute dosimetry of the carbon beam, neutron measurements and radiation protection measurements.

Medical physics aspects of particle therapy

Jakel, O. — Mon, 16 Nov 2009 09:54:49 PST

Charged particle beams offer an improved dose conformation to the target volume when compared with photon radiotherapy, with better sparing of normal tissue structures close to the target. In addition, beams of heavier ions exhibit a strong increase of the linear energy transfer in the Bragg peak when compared with the entrance region. These physical and biological properties make ion beams more favourable for radiation therapy of cancer than photon beams. As a consequence, particle therapy with protons and heavy ions has gained increasing interest worldwide. This contribution summarises the physical and biological principles of charged particle therapy with ion beams and highlights some of the developments in the field of beam delivery, the principles of treatment planning and the determination of absorbed dose in ion beams. The clinical experience gathered so far with carbon ion therapy is briefly reviewed.

Radiation protection constraints for use of proton and ion accelerators in medicine

Agosteo, S. — Mon, 16 Nov 2009 09:54:49 PST

This paper gives some guidelines for radiation protection at proton therapy facilities. The energy and angular distribution of secondary radiation from thick iron and tissue targets bombarded by 250-MeV protons were calculated with Monte Carlo simulations in order to emphasise the influence of the various components of the radiation field on the shielding design. The main constraints for radiation protection (e.g. workload, use and occupancy factors, etc.), shielding design (including access mazes) and the estimate of material activation are also discussed with some practical examples.

Cosmic radiation and aircrew exposure

Beck, P., Bottollier, J.-F., Reitz, G., Ruhm, W., Wissmann, F. — Tue, 13 Oct 2009 08:38:12 PDT

Epidemiological studies of cancer in aircrew

Hammer, G. P., Blettner, M., Zeeb, H. — Tue, 13 Oct 2009 08:38:12 PDT

Exposure to cosmic ionising radiation, in addition to other specific occupational risks, is of concern to aircrew members. Epidemiological studies provide an objective way to assess the health of this occupational group. We systematically reviewed the epidemiological literature on health of aircrew members since 1990, focusing on cancer as the endpoint of interest. Sixty-five relevant publications were identified and reviewed. Whereas overall cancer incidence and mortality was generally lower than in the comparison population, consistently elevated risks were reported for breast cancer incidence in female aircrew members and for melanoma in both male and female aircrew members. Brain cancer was increased in some studies among pilots. Occasionally trends of increasing cancer mortality or incidence with increasing estimated radiation dose were reported. Ionising radiation is considered to contribute little if at all to the elevated risks for cancers among aircrew, whereas excess ultraviolet radiation is a probable cause of the increased melanoma risk.

Implications of the new ICRP recommendations for aircrew dosimetry

Dietze, G. — Tue, 13 Oct 2009 08:38:12 PDT

In 2007 the International Commission on Radiological Protection has published its general recommendations replacing the previous 1990 Recommendations. In this paper mainly those parts of the recommendations, which may influence the assessment of doses to aircrews in flight heights, are presented and discussed. Aircrews are generally defined to be occupationally exposed workers and in many countries their exposure is assessed by determination of route doses in flight heights. While the definition of the operational quantities has not been changed, the paper concentrates on the definition of the effective dose, the introduction of anthropomorphic voxel phantoms, the weighting of the different organs and tissues of the human body and the radiation weighting factors. Its implications for aircrew monitoring is discussed.

Overview of research on aircraft crew dosimetry during the last solar cycle

Beck, P. — Tue, 13 Oct 2009 08:38:12 PDT

Cosmic radiation was discovered successfully in the beginning of the twentieth century by the Austrian Nobel Price winner Victor Hess. Radiation effects to humans are of major concern during human space missions and also due to the increasing aviation altitudes and flight time. ICRP recommendations lead to adaptations of the Basic Safety Standards by the European Council. Beginning in the 1990s up to now, significant improvements and findings in aviation dosimetry and epidemiology were done wordwide. Five research projects on measurements and modelling cosmic radiation exposure were supported by European Research Framework Programmes. In-flight measurements with remarkable agreement (±25%) were carried out to validate calculation codes for routine dose assessment within ±30% for galactic cosmic radiation. Measurements and improvements of modelling radiation exposure due to solar particle events (SPE) is still an objective for future research projects.

Dosimetry at aviation altitudes (2006-2008)

Meier, M. M., Hubiak, M., Matthia, D., Wirtz, M., Reitz, G. — Tue, 13 Oct 2009 08:38:12 PDT

Based upon the European Union (EU)-Directive 96/29/EURATOM, legal regulations on the radiation protection of aircrew had to be implemented into the corresponding national law within the member states of the EU by 13 May 2000. In Article 42 the directive stipulates, among other things, that the exposure of the crew concerned shall be assessed. This requirement has been implemented by dose calculations for most aircrew members in the EU. Some airlines and research institutes regularly spot check the calculated doses by measuring flights. The solar minimum is a time period of particular interest since the dose rates at aviation altitudes reach their maximum within the 11-year solar cycle. For this reason, the German Aerospace Center (DLR) performed repeated measuring flights in cooperation with several German airlines during the past solar minimum from March 2006 to August 2008. The measuring devices used consisted of a tissue equivalent proportional counter, various types of Liulin semiconductor detectors and several bubble detectors.

Continuous measurement of secondary neutrons from cosmic radiation at mountain altitudes and close to the north pole--a discussion in terms of H*(10)

Ruhm, W., Mares, V., Pioch, C., Simmer, G., Weitzenegger, E. — Tue, 13 Oct 2009 08:38:12 PDT

Two Bonner sphere spectrometers (BSSs) have recently been installed to measure secondary neutrons from cosmic radiation continuously, one at the environmental research station ‘Schneefernerhaus’ at an altitude of 2650 m in Germany and the other at the Koldewey station close to the North Pole in Ny-Ålesund, Spitsbergen. After unfolding, both systems provide neutron fluence energy distributions as a function of time. Based on these distributions and on fluence-to-dose conversion coefficients, mean ambient dose equivalent rate values of 75.0 ± 2.9 nSv h^–1 and 8.7 ± 0.6 nSv h^–1 were obtained for October 2008, respectively (quoted uncertainties represent standard deviations of 124 values obtained during the measurement period). Ambient dose equivalent rates measured by means of an extended rem counter at the Schneefernerhaus agree with those based on the BSS neutron energy distributions within 5 %. The ambient dose equivalent rate was also calculated based on simulated FLUKA neutron energy distributions in the atmosphere. Even without detailed modelling of the local environment, an agreement better than 30 % was obtained between the ambient dose equivalent rate based on the FLUKA distributions and those based on the BSS measurements at the Schneefernerhaus, for neutrons above about 20 MeV. This agreement is expected to be even better if the influence of the local environment on the measured neutron fluence energy distribution will be calculated.

Air crew dosimetry with a new version of EPCARD

Mares, V., Maczka, T., Leuthold, G., Ruhm, W. — Tue, 13 Oct 2009 08:38:12 PDT

EPCARD.Net as completely new code is based on the same approved physical algorithm as EPCARD version 3.34. As a major feature, many significant changes were made in the information technology area. There are only a few physical improvements adopted in the parameters database of the new EPCARD.Net. These are mainly ‘dynamic’ fluence-to-dose conversion coefficients and the most recent model of the world grid cut-off rigidity. Differences between EPCARD.Net and EPCARD version 3.34 are discussed in terms of effective dose. These differences turned out to be less than ~8 %.

IASON-FREE: theory and experimental comparisons

Felsberger, E., O'Brien, K., Kindl, P. — Tue, 13 Oct 2009 08:38:12 PDT

A sophisticated flight code named FREE (acronym for Flight Route Effective Dose Estimation) was built for professional commercial usage. During its creation special precautions have been taken to take correctly into account all existing dependencies and details, so that the best possible result is achieved. Some of these factors are presented in detail and their effect on doses or dose rates is estimated. Detailed comparisons to more recent measurements for both quiescent as well as disturbed conditions are presented. The agreement at undisturbed conditions turns out to be excellent and also the comparisons to measured transient effects are very satisfactory.

Development of a predictive code for aircrew radiation exposure

McCall, M. J., Lemay, F., Bean, M. R., Lewis, B. J., Bennett, L. G. I. — Tue, 13 Oct 2009 08:38:13 PDT

Using the empirical data measured by the Royal Military College with a tissue equivalent proportional counter, a model was derived to allow for the interpolation of the dose rate for any global position, altitude and date. Through integration of the dose-rate function over a great circle flight path or between various waypoints, a Predictive Code for Aircrew Radiation Exposure (PCAire) was further developed to provide an estimate of the total dose equivalent on any route worldwide at any period in the solar cycle.

The SIEVERT system for aircrew dosimetry

Clairand, I., Fuller, N., Bottollier-Depois, J.-F., Trompier, F. — Tue, 13 Oct 2009 08:38:13 PDT

Flight personnel are likely to receive an effective dose of several mSv in 1 y of professional activity. In France, the order of 8 December 2003 requires airline companies to monitor the exposure of their flight personnel. This is why public authorities have made the SIEVERT system (a system for evaluating exposure to cosmic radiation in air transport), available to French airlines, to evaluate doses. The SIEVERT system has been operational for use by airlines since the start of summer 2001. So far, more than 2.5 million flights have been processed at the request of more than 30 French airlines. Furthermore, this system was opened to the public in March 2002 (http://www.sievert-system.org), so that every passenger can calculate the dose received during a flight.

AVIDOS--a software package for European accredited aviation dosimetry

Latocha, M., Beck, P., Rollet, S. — Tue, 13 Oct 2009 08:38:13 PDT

AVIDOS is a computer code used for the dose assessment of aircraft crew exposed to cosmic radiation. The code employs a multiparameter model built upon simulations of cosmic radiation exposure done using the FLUKA Monte Carlo code. AVIDOS calculates both ambient dose equivalent H*(10) and effective dose E for flight routes over the whole world at typically used altitudes and for the full range of solar activity. The dose assessment procedure using AVIDOS is accredited by the Austrian office for accreditation according to European regulations and is valid in the whole Europe. AVIDOS took part in an international comparison of different codes assessing radiation exposure of aircraft crew where a fully satisfactory agreement between codes has been found. An online version of AVIDOS with user friendly interface is accessible to public under the internet address: http://avidos.healthphysics.at.

The implementation of cosmic radiation monitoring in routine flight operation of IBERIA airline of Spain: 1 y of experience of in-flight permanent monitoring

Vergara, J. C. S., Roman, R. D.-M. — Tue, 13 Oct 2009 08:38:13 PDT

Since 2000 IBERIA and CIEMAT have been collaborating in experimental measurements of onboard radiation doses received by the crew of IBERIA commercial flights. As part of the IBERIA radiation protection program for aircrew members, a monitoring system for routine aircrew dosimetry has been implemented based on the conclusions from the experimental work and the code EPCARD 3.2. The system feeds the computer code with the predicted flight plans and registers the route dose in the corresponding file for each aircrew member. The radiation protection program also includes a validation of the computed doses with experimental tissue equivalent proportional counter measurements, which in 2008 had been extended with the permanent installation and continuous operation of MDU-Liulin Si spectrometers in eight A-340-300 aircraft. It is expected that these instruments would provide experimental data on the radiation received for 4500 flights per year, which is of special value to detect unpredictable solar particle events.

Overview of on-board measurements during solar storm periods

Beck, P., Dyer, C., Fuller, N., Hands, A., Latocha, M., Rollet, S., Spurny, F. — Tue, 13 Oct 2009 08:38:13 PDT

Radiation exposure of aircraft crew caused by cosmic radiation is regulated in Europe by the European Community Council Directive 96/29/EURATOM and implemented into law in almost every country of the European Union. While the galactic cosmic radiation (GCR) leads on average to an exposure of about 3 mSv per year, solar cosmic radiation can lead to 1 mSv per one subsonic flight during solar storm periods. Compared to GCR, solar cosmic radiation shows a much softer proton spectrum but with a larger contribution of several orders of magnitude. This is the reason for the large radiation exposure in high northern and southern geographic latitudes during solar particle events. Here an overview of active radiation in-flight measurements undertaken during solar storms is given. In particular, tissue-equivalent proportional counter on-board measurements are shown and the radiation quality during solar storm periods with that for GCR is compared.

The ground level event 70 on December 13th, 2006 and related effective doses at aviation altitudes

Matthia, D., Heber, B., Reitz, G., Sihver, L., Berger, T., Meier, M. — Tue, 13 Oct 2009 08:38:13 PDT

The 70th ground level event in the records of the Neutron Monitor network occurred on 13 December 2006 reaching a maximum count rate increase at the Oulu station of more than 90 % during the 5 min interval 3.05–3.10 UTC. Thereafter, count rates gradually decreased registering increases of a few per cent above the galactic cosmic ray background after a few hours. The primary proton spectrum during the first 6 h after the onset of the event is characterised in this work by fitting the energy and angular distribution by a power law in rigidity and a linear dependence in the pitch angle using a minimisation technique. The results were obtained by analysing the data from 28 Neutron Monitor stations. At very high northern and southern latitudes, the effective dose rates were estimated to reach values of 25–30 µSv h^–1 at atmospheric depth of 200 g cm^–2 during the maximum of the event. The increase in effective dose during north atlantic and polar flights was estimated to be in the order of 20 %.

Modelling of radiation exposure at high altitudes during solar storms

Al Anid, H., Lewis, B. J., Bennett, L. G. I., Takada, M. — Tue, 13 Oct 2009 08:38:13 PDT

A transport code analysis using Monte Carlo N-Particle eXtended code, MCNPX, has been used to propagate an extrapolated particle spectrum based on satellite measurements through the atmosphere to estimate radiation exposure during solar storms at high altitudes. Neutron monitor count rate data from stations around the world were used to benchmark the model calculations during a ground-level event (GLE). A comparison was made between the model predictions and actual flight measurements taken with various types of instruments used to measure the mixed radiation field during GLE 60. A computer code has been developed to implement the model for routine analysis.

Comparison of codes assessing galactic cosmic radiation exposure of aircraft crew

Tue, 13 Oct 2009 08:38:13 PDT

The assessment of the exposure to cosmic radiation onboard aircraft is one of the preoccupations of bodies responsible for radiation protection. Cosmic particle flux is significantly higher onboard aircraft than at ground level and its intensity depends on the solar activity. The dose is usually estimated using codes validated by the experimental data. In this paper, a comparison of various codes is presented, some of them are used routinely, to assess the dose received by the aircraft crew caused by the galactic cosmic radiation. Results are provided for periods close to solar maximum and minimum and for selected flights covering major commercial routes in the world. The overall agreement between the codes, particularly for those routinely used for aircraft crew dosimetry, was better than ±20 % from the median in all but two cases. The agreement within the codes is considered to be fully satisfactory for radiation protection purposes.

Evaluation of the implementation of radiation protection measures for aircrew in EU member states

Thierfeldt, S., Haider, C., Hans, P., Kaleve, M., Neuenfeldt, F. — Tue, 13 Oct 2009 08:38:13 PDT

An evaluation of the implementation of radiation protection measures for aircrew in EU Member States has recently been performed in a study sponsored by the European Commission. A comprehensive database has been gathered using questionnaires for civil aviation authorities, aircraft operators and radiation protection authorities in each country. The study has revealed the following results: all countries within the scope of this study where aircrew might receive annual doses >1 mSv have implemented appropriate legislation. The treatment of limits or constraints (action levels) for annual doses of 1, 6, 20 mSv could be an area where clear guidance by the European Commission might be needed. The way in which doses are determined might also be treated in a more harmonised way in the EU, including the transfer of dose data of freelancers or crew members working for other airlines. The establishment of the European Aviation Safety Agency leads to a gradual shift in responsibilities from the national civil aviation authorities towards this centralised European agency. Currently, however, tracking of doses for aircrew still lies with national bodies.

Some changes in instructions to authors

McDonald, J. C. — Mon, 21 Sep 2009 08:33:41 PDT

A review of radiology staff doses and dose monitoring requirements

Martin, C. J. — Mon, 21 Sep 2009 08:33:41 PDT

Studies of radiation doses received during X-ray procedures by radiology, cardiology and other clinical staff have been reviewed. Data for effective dose (E), and doses to the eyes, thyroid, hands and legs have been analysed. These data have been supplemented with local measurements to determine the most exposed part of the hand for monitoring purposes. There are ranges of 60–100 in doses to individual tissues reported in the literature for similar procedures at different centres. While ranges in the doses per unit dose-area product (DAP) are between 10 and 25, large variations in dose result from differences in the sensitivity of the X-ray equipment, the type of procedure and the operator technique, but protection factors are important in maintaining dose levels as low as possible. The influence of shielding devices is significant for determining the dose to the eyes and thyroid, and the position of the operator, which depends on the procedure, is the most significant factor determining doses to the hands. A second body dosemeter worn at the level of the collar is recommended for operators with high workloads for use in assessment of effective dose and the dose to the eye. It is proposed that the third quartile values from the distributions of dose per unit DAP identified in the review might be employed in predicting the orders of magnitude of doses to the eye, thyroid and hands, based on interventional operator workloads. Such dose estimates could be employed in risk assessments when reviewing protection and monitoring requirements. A dosemeter worn on the little finger of the hand nearest to the X-ray tube is recommended for monitoring the hand.

Assessment of radiation doses to Australian participants in British nuclear tests

Crouch, P., Robotham, F., Williams, G., Wise, K. — Mon, 21 Sep 2009 08:33:41 PDT

Between 1952 and 1957, the UK exploded a total of 12 nuclear devices in Australia, and also conducted about 600 ‘minor trials’ that did not involve a nuclear explosion. Over 16 000 Australian servicemen and civilians were involved in the UK tests in Australia. This paper reports the estimation of doses that the Australian participants received as a result of their involvement. Both the external and internal exposure pathways were considered. Most participants received very small doses: 79 % of all participants received <1 mSv, and less than 4 % received >20 mSv, the current internationally recommended annual dose limit to workers. The largest dose recorded was 133 mSv, received by aircrew conducting sampling in the nuclear cloud soon after detonation. Most doses >20 mSv were received by groups who entered the near vicinity of the explosions or fallout contaminated areas to collect samples or instruments soon after a detonation. Internal doses were a very small component of the total dose during the first few months after detonation, but thereafter inhalation became an increasingly important pathway due to the presence of unburnt nuclear fuel in fallout.

Secondary charged particle equilibrium in 137Cs and 60Co reference radiation fields

Behrens, R., Kowatari, M., Hupe, O. — Mon, 21 Sep 2009 08:33:41 PDT

During the calibration or irradiation of dosemeters, typical irradiation geometries (collimated beams) and source-to-detector distances (1–5 m) lead to the fact that for photon energies above a few hundred keV, the secondary charged particle equilibrium is usually not ensured. The reason is that the effective beam radius at the detector position is smaller than the range of the secondary electrons produced in air whose maximum particle energy is as large as the maximum photon energy. Therefore, the International Organization for Standardization (ISO) recommends putting a build-up plate (BUP) made of polymethyl methacrylate in front of the dosemeter to be calibrated in ISO 4037-3. In this paper, the effect of the thickness of the BUP and its distance from the dosemeter at different source-to-dosemeter distances were investigated by means of measurement and calculation. It turned out that the geometrical arrangement of the source, dosemeter and BUP recommended by ISO mostly does not ensure secondary charged particle equilibrium. The consequence is to always place the BUP directly in front of the dosemeter to be calibrated or irradiated.

Development of an algorithm for evaluating personal doses due to photon fields in terms of operational quantities for TLD badge system in India

Mon, 21 Sep 2009 08:33:41 PDT

In order to evaluate and report the personal doses in terms of personal dose equivalent, the performance of the CaSO₄:Dy based thermoluminescence dosemeter (TLD) badge used for countrywide personnel monitoring in India is investigated using monoenergetic and narrow spectrum radiation qualities equivalent to those given in ISO standards. Algorithms suitable for evaluating H_p(10) and H_p(0.07) within ± 30 % are developed from the responses of dosemeter elements/discs under different filters for normal as well as angular irradiation conditions using these beams. The algorithm is tested for TLD badges irradiated to mixtures of low- and high-energy (¹³⁷Cs) beams in various proportions. The paper concludes with the results of test of algorithm by evaluation of badges used in the IAEA/RCA intercomparison studies and discussion on inherent limitations.

Occupational exposure to ambient electromagnetic fields of technical operational personnel working for a mobile telephone operator

Mon, 21 Sep 2009 08:33:41 PDT

In order to investigate the exposure of operational personnel to radiofrequency electromagnetic fields when working for a mobile telephone operator, exposimeters were used to make individual records on 23 Technical Operations personnel (mobile telephone maintenance staff) and also on 22 Other Workers. The exposure densities, to which each of the 45 subjects was subjected, were quantified using 229 exposure indicators. Cluster analysis techniques were applied to the data, in an attempt to show that they would re-emerge as belonging to one of the two groups, i.e. the Technical Operational Personnel group or the Other Workers group. This exploratory investigation has shown that the cluster analysis does not reveal a sufficiently reliable emergence of the two groups, even though certain exposure indicators were significantly different for the two groups. In addition, the use of a Learning Group method does not lead to the discovery of a predictive law that could identify the Technical Operational Personnel as a sub-group within the overall group.

Optimisation of patient radiation protection in conventional X-ray imaging procedures using film reject analysis: a demonstration of the importance of rare earth screen-film systems

Inkoom, S., Schandorf, C., Fletcher, J. J. — Mon, 21 Sep 2009 08:33:41 PDT

The optimisation of patient protection was studied using a conventional film screen of speed class 200 and a rare earth film screen of speed class 400. The entrance surface dose (ESD) for the two film-screen systems was determined for patients undergoing some common diagnostic procedures (chest, lumbar spine and pelvis series). The ESD was the optimising parameter and its trade off with the image quality assessment of the radiographs. The estimated ESDs were compared with reference levels set by the Commission of the European Communities for a typical standard adult patient. A mean dose reduction of 17–33 % was achieved upon adoption of a rare earth film screen of speed class 400. Regular assessment of patient dose, quality control (QC) of parameters that affect the patient dose and image quality, adoption of faster rare earth screens and optimum radiographic technique are recommended in order to achieve optimisation goals.

Patient dose assessment due to fluoroscopic exposure for some selected fluoroscopic procedures in Ghana

Gyekye, P. K., Schandorf, C., Boadu, M., Yeboah, J., Amoako, J. K. — Mon, 21 Sep 2009 08:33:41 PDT

Organ and effective doses to 90 patients undergoing some selected fluoroscopic examinations at the Korle-Bu Teaching Hospital were estimated using the Monte Carlo-based program (PCXMC version 1.5). Radiation dose was estimated from free-in-air measurements. The mean effective doses were found to be 0.29 ± 0.07, 0.84 ± 0.13, 3.15 ± 0.44, 6.24 ± 0.70 and 0.38 ± 0.05 mSv for urethrogram, barium swallow, barium meal, barium enema and myelogram examinations, respectively. The dose area product was estimated to be 3.55 ± 0.95, 16.44 ± 2.60, 50.81 ± 7.04, 99.69 ± 10.85 and 9.32 ± 0.99 Gy cm² for urethrogram, barium swallow, barium meal, barium enema and myelogram examinations, respectively. Optimisation of procedures is required for barium enema and barium meal examinations.

Radon effective dose from TENORM waste associated with petroleum industries

Abo-Elmagd, M., Soliman, H. A., Daif, M. M. — Mon, 21 Sep 2009 08:33:41 PDT

Technically enhanced naturally occurring radioactive material (TENORM) associated with petroleum industries can be accumulated with elevated quantities and therefore can threat the workers through external and internal exposure. Measurements of radon-related parameters give information about the radioactivity levels in the TENORM waste using the well-established correlation. Also, it is useful to calculate the internal exposure due to radon inhalation in terms of effective radon dose. Among radon-related parameters, areal exhalation rate is the most suitable for characterising land and objects with only upper surface contamination in the case of petroleum waste. The TENORM in this study is collected from waste storage areas located near oilfields at south Sinai governorate, Egypt. The average values of exhalation rates as measured by Lucas cell based on delay count method are 273 ± 144 and 38 ± 8 Bq m^–2 h^–1 for scale and sludge, respectively. Whereas, two count method gives results with 18 and 20 % lower values for scale and sludge, respectively with good correlation coefficient of 0.999 and 0.852, respectively. Sealed cup fitted with CR-39 gives results compatible with Lucas cell with minor deviation in case of scale due to its thoron content. The results of CR-39 are qualified by taking into consideration the correction for back diffusion effect. The effective radon dose was calculated for different simulated radioactive waste storage areas with different contaminated areas and air ventilation rate. Minimising the contaminated areas and building up efficient ventilation systems can reduce the internal exposure even in the case of RWSA-containing TENORM with elevated radioactivity.

Activity and radiation protection studies for the W-Ta target of CSNS

Yu, Q. Z., Liang, T. J., Yin, W. — Mon, 21 Sep 2009 08:33:41 PDT

The Chinese government initiated a conceptual design for the project of China Spallation Neutron Source (CSNS), which consists of an H-linear accelerator, a rapid cycling synchrotron accelerating the beam to 1.6 GeV, a target station converting proton beam into lower energy (<1 eV) neutron beam optimised to instruments for neutron scattering applications. The facility operates at 25-Hz repetition rate with an initial beam power of 100 kW. In the target station, the target-moderator-reflector (TMR) components are exposed to the intensive fluxes of high-energy hadrons and become highly radioactive as a result of long-time irradiation. In this paper, the activity of the TMR components are calculated using the Monte Carlo code system LAHET&MCNP4C&CINDER'90. Comparisons of some results with that simulated by FLUKA code are also performed. Detailed analyses of the radionuclides and their characters in the tantalum clad tungsten target (W-Ta target) are important for the radiation protection of the CSNS target station. The shielding design of the service cell for the decay gamma ray induced from the W-Ta target and its vessel shows that the ambient dose rate decreases exponentially with increasing heavy concrete thickness. And 80 cm thickness of heavy concrete for each side of the service cell can satisfy the safety requirement.

Regional survey of CT dose indices in India

Livingstone, R. S., Dinakaran, P. M. — Mon, 21 Sep 2009 08:33:41 PDT

This study intends to evaluate the current level of computed tomography (CT) scanner doses installed in a region in India. In-site CT dose measurement was performed for 127 CT scanners in a region in India. CT dose index (CTDI) was measured using a 10 cm3 pencil ion chamber and 32-cm polymethyl methacrylate body phantom. The CT numbers and image noise were measured for the phantom using software available on each CT scanner. Of the 127 CT scanners, 13 were conventional, 53 helical single-section, 44 multidetector row CT (MDCT) and 17 refurbished machines. The mean-weighted CTDI (CTDI_w) values calculated using standard exposure parameters for conventional, conventional refurbished, single-section helical scanner (SSHS), refurbished SSHS and MDCT scanners were 7.5, 6.53, 6.8, 6.6 and 7.04 mGy. Twenty-seven CT scanners had deranged CT numbers. Periodic quality assurance and regional dose surveys would be beneficial to set up regional reference levels in India.

International Commission on Radiation Units and Measurements Report 80: Dosimetry Systems for Use in Radiation Processing

Murphy, M. K. — Mon, 21 Sep 2009 08:33:41 PDT