Comparison of codes assessing galactic cosmic radiation exposure of aircraft crew.

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.

Air crew dosimetry with a new version of EPCARD.

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 approximately 8 %.

Long-term measurements of cosmic ray neutrons by means of a Bonner spectrometer at mountain altitudes - first results.

A Bonner multi-sphere spectrometer has been installed in 2005 at the Environmental Research Station 'Schneefernerhaus' (2660 m above sea level) on the Zugspitze mountain, Germany, to measure the energy spectrum of cosmic-ray neutrons at high altitudes continuously. The system can be used to investigate small temporal variations in the cosmic radiation intensity. For example, measurements were done during periods of 2 Forbush decreases of the cosmic radiation intensity in July and September 2005, respectively. The results were compared with those obtained by using neutron monitors, and neutron fluence spectra measured during these events are presented and discussed.

Altitude-dependent dose conversion coefficients in EPCARD.

Conversion coefficients that depend on altitude, cutoff rigidity and solar activity were developed and introduced in the European Program Package for the Calculation of Aviation Route Doses (EPCARD). A set of specially chosen long-distance flights were used to compare the new particle effective doses and ambient dose equivalents with those calculated using the previous averaged constant conversion coefficients. The data show very good agreement to each other. The dose differences for the chosen flights are <11%, for typical civil flight levels.

Pitfalls and modelling inconsistencies in computational radiation dosimetry: lessons learnt from the QUADOS intercomparison. Part I: Neutrons and uncertainties.

The QUADOS EU cost shared action conducted an intercomparison on the usage of numerical methods in radiation protection and dosimetry. The eight problems proposed were intended to test the usage of Monte Carlo and deterministic methods by assessing the accuracy with which the codes are applied and also the methods used to evaluate uncertainty in the answer gained through these methods. The overall objective was to spread good practice through the community and give users information on how to assess the uncertainties associated with their calculated results.

Pitfalls and modelling inconsistencies in computational radiation dosimetry: lessons learnt from the QUADOS intercomparison. Part II: Photons, electrons and protons.

'QUADOS', a concerted action of the European Commission, has promoted an intercomparison aimed at evaluating the use of computational codes for dosimetry in radiation protection and medical physics. This intercomparison was open to all users of radiation transport codes. Eight problems were selected for their relevance to the radiation dosimetry community, five of which involved photon and proton transport. This paper focuses on a discussion of lessons learned from the participation in solving the photon and charged particle problems. The lessons learned from the participation in solving the neutron problems are presented in a companion paper (in this issue).

QUADOS intercomparison: a summary of photon and charged particle problems.

QUADOS, a Concerted Action of the European Commission, has promoted an intercomparison aimed at evaluating the use of computational codes for dosimetry in radiation protection and medical physics. This intercomparison was open to all users of radiation transport codes. Eight problems were selected for their relevance to the radiation dosimetry community, five of which involved photon and proton transport. This paper focuses on the analysis of the photon and charged particle problems. The neutron problems were presented in a paper at the NEUDOS9 conference.

Intercomparison on the usage of computational codes in radiation dosimetry.

'QUADOS', a Concerted Action of the European Commission, has run an intercomparison aimed at evaluating the use of computational codes for dosimetry in radiation protection and medical physics. This intercomparison was open to all users of Monte Carlo, analytic and semi-analytic codes or deterministic methods. Its main aim was to provide a snapshot of the methods and codes currently in use. It also intended to furnish information on the methods used to assess the reliability of computational results and disseminate 'good practice' throughout the radiation dosimetry community. Eight problems were selected for their relevance to the radiation dosimetry community, three of which involve neutron transport. This paper focuses on the analysis of the neutron problems.

Options for the modified radiation weighting factor of neutrons.

The recent ICRP Report 92 has noted that the current radiation weighting factor, wR, depends on the energy of the incident neutrons in a manner that differs substantially from the dependence, which results from the current convention, QL. At all neutron energies, but most conspicuously below 1 MeV, the values of wR exceed those of the effective quality factor, qE. The discrepancy is largely due to the fact that--in the absence of computed values of the effective quality factor for neutrons--wR has been patterned after the values of the ambient quality factor, which accounts insufficiently for the low-linear energy transfer (LET) gamma ray component from neutron capture in the human body. There are different options to remove the discrepancy. Option 1 is to reduce wR substantially at all neutron energies to make it equal to qE for a standard condition, such as isotropic incidence of the neutrons. Since such a reduction may cause problems in those countries where the current wR values are already legally implemented, ICRP 92 has proposed what is here termed Option 2. It recommended to replace QL by the increased value 1.6 QL - 0.6 and, accordingly, to make the radiation weighting factor equal to 1.6 qE - 0.6. With Option 2 the radiation weighting factor needs to be decreased appreciably at low neutron energies, but for fission neutron spectra the overall changes are minor. To guide--regardless which option is chosen--the selection of the numerical values, the effective quality factor, qE, is computed here for different directional distributions of neutrons incident on the anthropomorphic phantoms ADAM and EVA. None of the sex averaged numerical values is found to deviate much from those for isotropic incidence. Isotropic incidence can, thus, be used as an adequate standard condition. A numerical approximation is proposed for the standard qE that is nearly equivalent to a formula invoked by ICRP 92, but is somewhat simpler and provides realistic values of qE even for the extremely high neutron energies in space. In line with ICRP 92, it is emphasised that wR needs to be seen as a derived quantity related to the LET-dependent weighting factor.

Neutron spectra at flight altitudes and their radiological estimation.

Since the publication of the ICRP-report 60, air crews and other frequently flying persons are considered as occupationally exposed people. At civil flight levels neutrons contribute the major part to the radiologically relevant dose to men. The quantification of the neutron dose, and herewith the radiation risk due to neutrons, suffers from spectral data available especially in the energy range above 20 MeV. Experimental data were recently obtained at a low flight level on top of the mountain Zugspitze at 3000m using a modified Bonner sphere spectrometer. The resulting spectra are compared with Monte-Carlo transport calculations from top of the atmosphere down to 700 g/cm2. These data and others from the literature are used to calculate operational and risk related quantities, i.e. ambient dose equivalent and effective dose.

[Behavior of back fat thickness, the activity of NADP-dependent dehydrogenases from adipose tissue and adipose tissue constituents fat and protein and their evidence for energy metabolism in dairy cows]. / Verhalten der Rückenfettdicke, der Aktivitäten der NADP-abhängigen Dehydrogenasen des Fettgewebes sowie der Fettgewebsbestandteile Fett und Protein und ihre Aussage zum Energiestoffwechsel der Milchkuh.

Studies were conducted into 60 Friesian dairy cattle in the GDR for determination of dorsal fat thickness (DFT), activities of glucose-6-phosphate dehydrogenase (GPDH) and isocitrate dehydrogenase (ICDH) in adipose tissue, concentrations of fat and protein in adipose tissue, 2 weeks ante partum as well as 0, 2, 4, 6, 8, 12, 16, 20, 28, 36 weeks post partum, and liver fat levels, 2 and 4 weeks post partum. DFT, ICDH, GPDH, ICDH-GPDH ratio, fat level, fat-protein quotient, changes in DFT, GPDH, and fat-protein quotient exhibited significant relations with the weeks of lactation. The above 60 experimental cows were subdivided by 6 groups of half-siblings consisting of 10 animals each. Significant differences were found to exist between these groups of half-siblings with regard to DFT, GPDH, ICDH-GPDH ratio, and fat-protein quotient. Within each of the half-sibling groups, significant differences were found to exist between individuals for DFT, ICDH, GPDH, ICDH-GPDH ratio, and fat-protein quotient. The above parameters can be used to describe the energy metabolism of dairy cow via quantitative and temporal curves of fat mobilisation and fat deposition. In the context of both animal health and breeding, more attention should be given to determination of mobilisation and deposition of fat as well as to the post partum energy deficit.

Mathematical simulation of proton tracks in water vapor and their microdosimetric analysis.

The spatial pattern of primary physical events was calculated for protons in water vapor by means of a Monte Carlo program. Two different cross section data sets were used to cover the proton energy range from 0.2 to 15 MeV. From the spatial pattern of primary energy deposition, proximity functions were derived and from these the dose mean lineal energy yD was calculated. The contributions of different track components to yD for spherical target volumes of 1-100 nm were analysed. The results are compared with the LET approximation and with analytical calculations of yD based on expectation values of the radial energy deposition around the proton path (radial dose profiles). Finally the associated volume of proton tracks was calculated using the so called 'linear approximation', and energy deposition distributions were derived. These were compared with distributions calculated by means of restricted-LET.

[Glucose tolerance in miniature swine]. / Untersuchungen zur Glukosetoleranz an Miniaturschweinen.

Miniature pigs of the "Mini-Lewe" breed were used to study the behavior of glucose and insulin. Firstly, the blood glucose levels within definite intervals of life were determined, thereafter glucose and insulin data were collected during a day and for a period of 60 min (taking 5 blood samples). In intravenous glucose tolerance tests animals with varying glucose utilization were established.