Quantitative investigation of gamma radiation in accelerator produced ISO neutron fields.

In standard monoenergetic ISO neutron fields, the neutron yield of neutron-producing reactions was measured in combination with the prompt photon yield, including photon energies up to 10 MeV, for the purpose of comparing the two yields. Separating the photons produced by the target (direct photons) from those generated by secondary neutron reactions was achieved using the time-of-flight method. Photon and neutron ambient dose equivalent values were calculated from measured spectral energy distributions. Quasi monoenergetic neutron fields are needed to systematically test the response of measuring instruments to neutron radiation. For this reason, ISO has defined a number of reference neutron radiation fields covering a wide energy range up to 19 MeV. Because neutron detectors may also be affected by photon radiation, the photon fluence in the ISO neutron fields has to be known. This work focuses on quasi monoenergetic accelerator-produced neutron fields in the energy range of 24 keV to 19 MeV.

THE GERMAN DOSE RATE MONITORING NETWORK AND IMPLEMENTED DATA HARMONIZATION TECHNIQUES.

Environmental radiation monitoring networks have been established in Europe and world-wide for the purpose of protecting population and environment against ionizing radiation. Some of these networks had been established during the cold war period and were improved after the Chernobyl accident in 1986. Today, the German Federal Office for Radiation Protection (BfS) operates an early warning network with roughly 1800 ambient dose equivalent rate (ADER) stations equally distributed over the German territory. The hardware and software of all network components are developed in-house allowing the continuous optimization of all relevant components. A probe characterization and quality assurance and control program are in place. Operational and technical aspects of the network and data harmonization techniques are described. The latter allows for calculating of the terrestrial and net ADER combined with uncertainties mainly from site specific effects. Harmonized data are finally used as input to the German emergency management system and the European radiological data exchange platform.

ON THE CONVERSION COEFFICIENT FROM AIR KERMA TO AMBIENT DOSE EQUIVALENT VALID FOR A CS-137 PHOTON FIELD-A CRITICAL REVIEW.

In radiation protection, the quantity ambient dose equivalent, in short H*(10), is very important in the field of area dosimetry, because this quantity is used to estimate the effective dose to human beings, whose permissible limits are restricted by law. The conversion coefficient from air kerma to H*(10), valid for a 137Cs photon field, is essential as it enters the realization of the quantity H*(10) as well as every (directly or indirectly) related calibration. The basic calibration factor of any dose rate instrument is usually related to a calibration in a 137Cs photon field, which underlines the importance of the conversion coefficient discussed in this article. Because different values of this coefficient are used in different calibration facilities, a harmonized best value will be proposed based on detailed investigations on the origin of the values recommended in the past. The newly recommended value differs by almost 1% from the value used by most institutes, at the moment, which is large in comparison with the typical uncertainties in primary fields. The goal of this article is to interpret known ICRU/ICRP data adequately, not to calculate new data.

Novel spectrometers for environmental dose rate monitoring.

A new generation of dosemeters, based on the scintillators LaBr3, CeBr3 and SrI2, read out with conventional photomultipliers, to be used in the field of environmental gamma-radiation monitoring, was investigated. The main features of these new instruments and especially their outdoor performance, studied by long-term investigations under real weather conditions, are presented. The systems were tested at the reference sites for environmental radiation of the Physikalisch-Technische Bundesanstalt. The measurements are compared with that of well characterized classical dose rate reference instruments to demonstrate the suitability of new spectrometers for environmental dose rate monitoring even in adverse weather conditions. Their potential to replace the (mainly Geiger Müller based) dose rate meters operated in about 5000 European early waning network stations as well as in environmental radiation monitoring in general is shown.

INFLUENCE OF RADON PROGENY ON DOSE RATE MEASUREMENTS STUDIED AT PTB'S RADON REFERENCE CHAMBER.

The responses of electronic dose rate meters were investigated in a large volume radon chamber at PTB in a wide range of radon activity concentrations. The measurements were conducted under controlled laboratory conditions and measured dose rate data are compared with Monte-Carlo simulations. Consequences concerning environmental monitoring are described. A further result is that the direct measurement of the dose rates produced by radon progeny in air is hardly possible in radon atmospheres with high activity concentrations, because the major contribution of measured dose rates is produced by radon progeny on the housing of the dose rate instruments. The latter effect largely depends on the ability of surfaces to absorb radon progeny. The Monte-Carlo simulations revealed quantitative results on the height of the single contributions to the total dose rate measured in the radon chamber. When environmental dose rate measurements are performed, the plate-out on detectors can be neglected.

EURADOS intercomparisons and the harmonisation of environmental radiation monitoring.

After the Chernobyl nuclear power plant accident in 1986, all Member States of the European Union have installed area dose rate monitoring networks so that radiological incidents can be detected quickly. However, the different technical approaches and procedures led to inconsistencies in the area dose rate data. In the last 15 years, the working group 'Environmental Radiation Monitoring' of the European Radiation Dosimetry Group (EURADOS) has performed six pan-European intercomparison exercises for detector systems operated in national dosimetric early warning networks. These intercomparisons aimed at the harmonisation of area dose rate measurements of radiation monitoring stations in Europe. The intercomparisons revealed differences in technical properties of the dose rate monitoring systems as well as in the calibration and measuring methods that led to deviations of measured dose rate values by a factor of 5 or more under the same measuring conditions. As a result of the intercomparisons, the accuracy of dose rate measurements could be improved considerably. Further progress in metrologically correct measurements of area dose rates in the natural environment and necessary steps towards a metrologically sound pan-European system for environmental radiation monitoring will be discussed.

Area dose rate values derived from NaI or LaBr3 spectra.

More and more spectrometric systems are being installed in environmental radiation monitoring stations instead of or in addition to dosimetric detectors, because novel spectrometric systems have been developed which do not need any cooling and because the necessary electronics, especially digital multichannel analysers, have become more manageable and more affordable. The advantage of obtaining information about nuclide vectors can justify the operation of a more complex spectroscopic measuring system, but if spectrometers are also used for dose rate measurements in the natural environment, ambient dose equivalent rate values have to be calculated from measured spectra. Different approaches to achieve this goal will be presented in this article. Some practical recommendations will also be presented to avoid known errors.

PTB intercomparisons of passive H*(10) area dosemeters for environmental monitoring.

For measuring the quantity ambient dose equivalent, H*(10), various passive photon and neutron dosemeters have been newly developed and are used in particular for the monitoring of nuclear facilities in the radiation field of the natural ambient radiation. Since 2005, the Physikalisch-Technische Bundesanstalt (PTB) has been performing intercomparisons to study fundamental properties and the long-term behaviour of area dosemeters under real environmental conditions, i.e. the accuracy of photon and neutron measurements performed in the complex natural radiation field. Measuring bodies from four European countries were the participants, including Germany. The goal was, on the one hand, quality assurance for existing passive dosemeters and measurement procedures and, on the other hand, the experimental investigation of whether the requirements of the appropriate standards and guidelines are met in practical use.

Charged fusion product loss measurements using nuclear activation.

In ITER, α particle loss measurements will be required in order to understand the alpha particle physics. Techniques capable of operating in a fusion reactor environment need further development. Recent experimental studies on JET demonstrated the potential of nuclear activation to measure the flux of escaping MeV ions. New results from MeV ion induced activation of metallic, ceramic, and crystal samples placed near the plasma edge are reported. Activation products were measured as function of orientation with respect to the magnetic field as well as function of the distance to the plasma. Sample activity was measured using ultralow-level gamma-ray spectrometry. Distribution of 14.68 MeV fusion proton induced activation products is strongly anisotropic in agreement with simulations and falls off sharply with increasing distance to the plasma. Prospects for using the technique in ITER are discussed.

Monte Carlo simulations of the photon calibration fields at the underground laboratory of PTB.

A unique photon calibration facility operated by Physikalisch-Technische Bundesanstalt (PTB) provides photon fields with area dose rates in the order of the natural environmental radiation and even below. This facility is located in an underground laboratory in the Asse salt mine at a depth of 490 m below ground, where the ambient dose equivalent rate is only 2 nSv h(-1). Radioactive sources of the nuclides (241)Am, (57)Co, (137)Cs, (60)Co and (226)Ra are used to generate photon fields with different characteristics. In the past, the basic properties of the photon field, especially the area dose rate at the reference point and the mean energy of the photon spectra, were calculated by using analytic methods. However, information about scattered photons is only accessible through an investigation of spectra by performing Monte Carlos simulations. Therefore, the photon spectra at the reference point of the calibration facility were calculated using the Monte Carlo transport code MCNP. The results obtained by using this method are of relevance for the traceability of the reference dose rate values to PTB's primary standards, as well as for the determination of the mean photon energy of the spectra. The latter was calculated with respect to the different quantities 'photon fluence', 'air kerma' and 'ambient dose equivalent'. The origin of the scattered component in the photon spectrum is investigated in detail by studying the photon field produced by the quasi-monoenergetic gamma emitter (137)Cs (E(γ) = 662 keV) under various geometrical conditions. Implications of the Monte Carlo simulations on the traceability of the dose rate reference values as well as on the assessment of uncertainties will be described.

Environmental gamma dosimetry with OSL of alpha-Al(2)O(3):C for in situ sediment measurements.

The physical properties of alpha-Al(2)O(3):C are very similar to that of quartz, which make it an attractive dosimetric material for geological and archaeological dating applications. Storage experiments in an ultra-low-radiation underground environment (UDO at PTB) and gamma-ray spectrometry show that the optically stimulated luminescence (OSL) signal of this material does neither suffer from a significant inherent background caused by traces of radionuclides (<6 microGy a(-1)) nor from fading. After having performed a simple calibration procedure, gamma dosimetry based on alpha-Al(2)O(3):C detectors, which were exposed in a brick block and a lead castle for different periods of time, provided concordant results with dose values derived from independent gamma-ray spectrometric measurements using high-purity germanium and NaI:Tl detectors. These investigations indirectly confirm both the absence of a significant inherent background and fading of the detector material. Small doses of a few micro gray accumulated in short exposure times to environmental radiation can be accurately measured, even when doses (i.e. transport dose) much larger than the actual environmental dose have to be subtracted. It is shown that the OSL signal caused by small transport doses can be easily and reproducibly reset even under difficult field conditions by illuminating the dosemeters with the blue light from Luxeon LEDs. Summarised, alpha-Al(2)O(3):C appears to be the material of choice for dosimetric dating applications of quartz or related materials, when analysed by using OSL.

Traceability of the PTB low-dose rate photon calibration facility.

PTB operates an Underground laboratory for DOsimetry and spectrometry (UDO) in the Asse salt mine at a depth of 490 m below the ground. The ambient dose equivalent rate at UDO is only 2 nSv h(-1). Therefore, UDO is well suited for dosimetry at low dose rates as well as for other low-level measurements. UDO provides the only photon calibration facility worldwide for calibrations at low dose rates (comparable to those in the natural environment and even below), which are traceable to primary standards. Photon fields are generated by using radioactive sources of the following nuclides: (241)Am, (57)Co, (137)Cs, (60)Co and (226)Ra. The dose rates and mean photon energy values at the reference point of this calibration facility were calculated analytically after performing calibration measurements using a secondary standard. This procedure ensures for the traceability of the reference dose rate values to PTB's primary standards. The mean photon energy of each spectrum was calculated with respect to the different quantities air kerma and ambient dose equivalent, respectively. The assessment of the uncertainties of the basic properties of the photon calibration fields will be described.

Angular distribution of proton leakage from a fusion plasma using ultra low-level gamma-ray spectrometry.

This experiment aimed at studying a technique to measure the leakage of charged particles from a fusion plasma. The activity induced in samples of various materials placed on a special holder inside a Tokamak was measured using ultra low-level gamma-ray spectrometry (ULGS) performed in three underground laboratories. In total, 27 radionuclides were detected in this experiment. Seven of these radionuclides were mainly produced by proton interactions. For two of them it was possible to determine their angular distribution.

EURADOS intercomparison 2006 to harmonise European early warning dosimetry systems.

In 2006, the European Radiation Dosimetry (EURADOS) Working Group on Environmental Radiation Monitoring (WG3) organised a third European intercomparison of dosimetry systems operated in national early warning networks. Similar to the intercomparisons in 1999 and 2002, the main aim of this exercise was to support the process of harmonisation of area monitoring in Europe by providing the network operators with basic information on the calibration and performance of their dosimetry systems. In order to characterise these systems, their following basic parameters were investigated: the response to terrestrial and cosmic radiation, the detectors' inherent background, the response at low dose rates, the energy dependence of the response as well as the sensitivity of the detector systems to small changes of the dose rate in a natural environmental radiation field. In the 2006 EURADOS intercomparison, scientists from seven countries participated to study the characteristics of 11 detector systems. All results are presented in terms of the operational quantity ambient dose equivalent, H*(10). The advent of this quantity has caused the development of new detector systems for area monitoring. Some of these new systems participated in a EURADOS intercomparison for the first time. The results are consistently presented together with uncertainties so that statistical effects can be distinguished from real detector features, which improves the interpretation of the results. By using the results of this intercomparison, some detectors were re-calibrated. The achievable improvements concerning harmonisation in dose-rate measurements in the natural environment are discussed.

Improvements of a low-level gamma-ray spectrometry system at the underground laboratory "UDO".

The Physikalisch-Technische Bundesanstalt (PTB) operates various low-background gamma-ray spectrometry systems at the underground laboratory for dosimetry and spectrometry "UDO" in the Asse salt mine. Experiences gained with these detector systems within 10 years of operation have led to technical changes and improvements of the most sensitive detector system at UDO. Key aspects are the precautions to suppress radon (and its progenies) and the performance of the detector system after exchanging the end cap. In addition, a brief summary of recent applications of this gamma-ray detector system will be presented.

The second EURADOS intercomparison of national network systems used to provide early warning of a nuclear accident.

In 1999 and 2002, the EURADOS Working Group on Environmental Monitoring organised two European intercomparison exercises of national network systems used to provide early warning in case of a nuclear accident. In total, 12 European countries, represented by more than 40 scientists, participated in these two intercomparisons with more than 35 different dose rate detectors. In addition, an in situ gamma spectrometry intercomparison was performed by a group of European scientists during the 2002 exercise. Results of these spectrometry measurements will be reported elsewhere. This report summarises the results of the second intercomparison, performed in 2002, at the environmental dosimetry facilities of the Physikalisch-Technische Bundesanstalt (PTB) in Germany. The unique combination of the ultra-low background Underground Laboratory (UDO) and two free-field sites (a floating platform on a lake showing an almost pure cosmic radiation field and a free-field gamma ray irradiation facility) provide the particular opportunity to precisely quantify the inherent background of the detectors and to calibrate them almost free of any background and traceable to PTB's primary standards. In addition, the intercomparison comprised investigations on the energy and dose rate dependence of the detectors' response to gamma radiation as well as on the response to cosmic radiation. Finally, the sensitivity of the detector systems to small dose rate variations, similar to that caused by a passing overhead radioactive plume, was studied under realistic free-field conditions. Following the Council Directive 96/29/EURATOM, the participants of the 2002 intercomparison were asked to report their results in terms of the operational quantity ambient dose equivalent, H(*)(10). Although the verification of the individual calibrations showed smaller discrepancies than those in the 1999 intercomparison, in a few cases, these discrepancies would be still unacceptably high in the case of a real emergency situation as demonstrated by the plume results. This shows the clear need for further efforts towards a European harmonisation in environmental dosimetry. For this purpose, a further intercomparison shall be held at the PTB in 2006, especially with the participation of new members of the European Union.

Effective strategies for the prevention of osteoporosis across the life span.

Osteoporosis is generally considered an age-related reduction in the quantity and quality of bone, but it need not be considered an inevitable consequence of aging. Primary prevention of osteoporosis is clearly desirable, and all women should receive counseling regarding universal preventive measures such as dietary calcium and vitamin D, weight-bearing and resistance exercises, and smoking cessation. Perimenopausal and postmenopausal women should also be counseled about the potential benefits and risks of hormone prophylaxis. For individuals who are unable to take estrogens, other pharmacologic measures are available for prevention. Osteoporosis may also affect elderly men and patients receiving glucocorticoid therapy, and preventive measures should also be used for them.

Do medical students' knowledge and attitudes about health and exercise affect their physical fitness?

This study examined the relationship between unselected first-year medical students' knowledge and attitudes about health or exercise and their personal physical fitness. The 131 subjects performed a maximal exercise test to determine physical fitness by measuring maximal oxygen consumption (VO2max), underwent hydrostatic weighing to assess body fat content (percent body fat), and completed a questionnaire to measure their knowledge and attitudes about health promotion/disease prevention and exercise. Many independent variables were significantly associated with VO2max in bivariate analyses, but only percent body fat, resting systolic blood pressure, and perceived barriers to health promotion/disease prevention and to exercise were significant predictors of VO2max (mL x kg-1 x min-1) in the multivariate analyses. The absolute VO2max (L x min-1) can be predicted from percent body fat, weight, and perceived barriers to health promotion/disease prevention. Freshmen medical students' attitudes toward health promotion/disease prevention and exercise constitute one of three strong predictors of physical fitness levels and should be determined, along with percent body fat and resting systolic blood pressure, when estimating fitness levels in a medical student population.

Recurrent acute pancreatitis and intraluminal duodenal diverticulum.

An intraluminal duodenal diverticulum (IDD) and a partial pancreas divisum were diagnosed in a 22-year-old man who exhibited recurrent attacks of acute pancreatitis. Resection of the diverticulum resulted in a complete disappearance of symptoms. The possible etiological relationship between IDD and recurrent acute pancreatitis is discussed.