A Holistic Approach to Assessment of Population Exposure to Radiation: Challenges and Initiatives of a Regulatory Authority.

A regulatory authority for radiation safety should continuously evaluate and improve the national safety framework, in line with current requirements and standards. In this context, the Greek Atomic Energy Commission initiated a series of concerted actions. The radiation dose to the population due to public and medical exposures was assessed. The assessment of dose due to public exposure was based on measurements of radon concentrations in dwellings, radionuclide concentrations in environmental samples, and air dose rates; the assessment of dose due to medical exposure was based on dose measurements for typical examinations or procedures and data on their frequency. The mean effective dose to a member of the population was found to be 4.5 mSv (1.8 mSv and 2.7 mSv from medical and public exposures, respectively). Regarding occupational exposure, aircrew dose assessment, eye lens monitoring, and the national dose registry were significantly improved. With respect to artificial tanning (sun beds), the ultraviolet radiation produced was assessed and the practices followed were observed. Results demonstrated exceedance of the 0.3 W m erythema effective irradiance limit set in European Union standards by 63.5% of the sun beds measured, along with general noncompliance with standards. An overarching activity was the upgrade of the Greek Atomic Energy Commission information system in order to collect and disseminate radiation data electronically, launch a networking strategy for interaction with stakeholders, and facilitate the process of regulatory control. In response to the above findings, regulatory actions have been initiated.

Determination of 226Ra in urine samples by alpha spectrometry.

A radiation protection system to assess the internal contamination of workers during decontamination activities in an abounded fertilizer industry in the region of Attika, Greece, has been implemented. This system concerns, among other radionuclides, 226Ra. Because of the low 226Ra activities in urine, alpha spectrometry was used as the determination method after radiochemical separation. Radium was co precipitated with lead sulphate and purified using anion and cation exchange techniques. The source for the alpha spectrometric measurement was prepared by the electrodeposition of radium, from an aqueous/ethanol solution, onto stainless steel. The tracer used was 229Th. The chemical yield and the activity concentration were calculated via its daughter radionuclide 217At. Using the time-evolution formulas to calculate the 217At growth from its parent radionuclide 225Ra, a computer software was developed. This software was incorporated in a database, which automatically calculates and stores the results.

Quality assurance and quality control programme in the Personal Dosimetry Department of the Greek Atomic Energy Commission.

A quality assurance (QA) and quality control (QC) programme was applied to the personal monitoring department (TLD based) of the Greek Atomic Energy Commission (GAEC). This programme was designed according to the recommendations of international bodies such as the International Organization for Standardization (ISO), the International Electrotechnical Commission (IEC), the International Atomic Energy Agency (IAEA) and the European Commission (CEC). This paper deals with the presentation of the QA/QC programme which includes administrative data and information, technical checking of the equipment, acceptance tests of new equipment and dosemeters, issuing and processing of the dosemeters, dose evaluation, record keeping and reporting, traceability and reproducibility, handling of complaints, internal reviews and external audits.

From films to thermoluminescence dosemeters: the Greek Atomic Energy Commission experience.

The personnel dosimetry department of the Greek Atomic Energy Commission (GAEC) assures the individual monitoring of almost 8000 occupationally exposed workers. Thermoluminescence dosimetry systems will replace the existing photographic dosimetry system for the individual monitoring with the joint support of IAEA and GAEC. The thermoluminescence dosimetry system consists of two automated readers, one automated irradiator and about 20,000 dosemeters purchased from the Rados Co. The properties of two thermoluminescent materials have been compared: LiF has been chosen for the whole-body dosemeter configuration and Li2B4O7 for the extremities. The technical evaluation of the system has been performed according to the European and IEC standards. The overall uncertainty has been calculated. The existing database system, and the accounting and dispatching procedures have been adapted to the new demands. The system became operational on March 2000, and the official distribution of thermoluminescence dosemeters has begun.

Dose constraints to the individual annual doses of exposed workers in the medical sector.

The study is an attempt, within the process of the optimization of radiation protection, to propose constraints to the individual annual doses of classified workers employed in the medical sector of ionizing radiation applications in Greece. These exposed workers were grouped according to their specialties, i.e. medical doctors, technicians and nurses and their occupational category with common or similar tasks, such as diagnostic radiology, interventional radiology, nuclear medicine and radiotherapy. The last 5 years' annual dose distributions of these occupational groups, coming from the National Dose Registry Information System (NDRIS) of the Greek Atomic Energy Commission (GAEC) were analyzed. The proposed dose constraints (DCs) were set at levels, below which the annual doses of the 70 or 75% of the exposed workers per category are expected to be included. At the present stage the derived values may be considered achievable ceiling values referring to acceptably applied practices rather than to optimized ones, taking into account social and economic criteria.

[Improper use of antimycotics in oral diseases]. / Adikaiologete chrese antimyketiasikon se nosemata tou stomatos.

Antimycotics are the drugs of choice in the treatment of mycotic infections including oral candidiasis. Furthermore their complementary use in the treatment of oral conditions in which Candida albicans is implicated aetiopathogenically is also effective. However, according to the results of a retrospective study based on a random sample of 1000 cases from the files of the Oral Pathology Clinic of the Dental School of the University of Athens, it became apparent that these drugs are used either by patients themselves or prescribed by dentists and physicians for a broad spectrum of oral diseases.

The polarized UV-absorption spectra and the crystal structure of two different monoclinic crystal forms of the retinal homologue beta-8'-apocarotenal.

During the visual process, light absorption in the 11-cis retinylidene chromophore leads to a rapid cis-trans-isomerization which initiates the phototransduction step. Important spectroscopic properties of this chromophore can be derived from polarized UV-absorption spectra of crystalline 11-cis-retinal if a parallel X-ray structure analysis is performed. Several questions about the relation between molecular geometry and spectroscopic behavior could not be answered from these spectra. All crystal forms of 11-cis-retinal contain this molecule in its 6-s-cis-ring conformation. For the retinal homologue, beta-8'-apocarotenal (APC), however, two crystal forms with different ring conformation can be grown. The spectrum of alpha-APC (6-s-cis) shows a vibronic structure whereas that of beta-APC (6-s-trans) is diffuse but has a distinct shoulder on the low energy side of the main band. This S-band is typical for retinal spectra and has been ascribed to a transition into a 1Ag-*-state. The appearance of the S-band is not correlated with a 6-s-cis-conformation as suggested by the retinal spectra but is due to intermolecular interactions: beta-APC has a dense dimer packing and a strong electrostatic interaction between the pi-electron systems. This might cause the "forbidden" 1Ag-*-transition. On the other hand, this interaction is missing in the loose and polar packing of alpha-APC which favors vibration in the polyene chain. This finding is remarkable in view of the photodynamic behavior of the visual chromophore for which strong electrostatic interactions with the protein helices of its binding site have to be postulated.