[en] The application of the ratio of the readings of the 9- and 3-in. Bonner spheres is a widely used method to characterize the spectral distribution of neutron survey fields, especially in the United States. A method has been introduced to determine a correction factor for the energy dependence of the responses of individual albedo dosimeters when these are exposed in any slowing-down neutron field. The basic idea is to approximate the energy dependence of the response of the albedo dosimeter by the response of a 3-in. sphere, assuming that the energy dependence of the response of the 9-in. sphere is sufficiently similar to the required fluence-to-dose equivalent conversion function. It is concluded that the concept of the 9-in./3-in. sphere ratio is still applicable if the new operation quantities are applied and if the general overresponse of the method at energies below 1 MeV remains acceptable

[en] Recent findings in radiation transport calculations and experiments in the Earth's atmosphere are summarised. Emphasis is placed on the neutrons as the major contributor to effective dose and dose equivalent. Spectral distributions and conversion coefficients are used to determine the dose quantities. The conservativity of the operational quantity is studied. The depth dose characteristic in the atmosphere and its slope is compared with data from theoretical calculations. The concept of the computer program package EPCARD is explained in brief which is intended to combine experimental and theoretical data obtained from different laboratories under different geomagnetic and solar conditions. (author)

[en] Document available in abstract form only, full text of publication follows: This paper describes the results of neutron spectrometry using the Bonner Sphere Spectrometer (BSS ) at the ring cyclotron facility at the Research Centre for Nuclear Physics (RCNP), Osaka University, Japan. The BSS system consists of 15 polyethylene (PE) spheres with spherical ³He proportional counters in their centre. It also includes two PE spheres with lead shells inside, to increase their response to high-energy neutrons above 10 MeV. Quasi-monoenergetic neutron fields at RCNP were generated from a 10 mm thick Li target using the ⁷Li(p,n)⁷Be reaction, injected by 245 and 388 MeV protons. The neutrons produced at 0 deg. and 30 deg. were extracted into the time-of-flight (TOF) tunnel of 100 m length through the concrete collimator of 10 x 12 cm² aperture and 150 cm thickness. The neutron energy spectra were measured at distance of 41 m from the target in the TOF tunnel. To deduce the energy spectra of neutrons from thermal to 1 GeV, an unfolding method with MSANB code was used together with response functions obtained by neutron transport calculations using the MCNP/LAHET code. The neutron energy spectra are discussed in terms of neutron fluence rates and ambient dose equivalent H*(10). The BSS results are also compared to neutron energy spectra measured by a NE213 organic liquid scintillator using the TOF method. (authors)

[en] This work is devoted to the calculation of responses as functions of neutron energy for a paired set of Andersson-Braun rem counters, which is commercially available. Different Monte Carlo codes such as MCNP, LAHET, HADRON and MCNPX were applied in the calculations. The study extended to frontal, lateral and isotropic neutron incidence. For an estimation of the contribution of charged high-energy particles to the reading, the responses to protons and pions were also determined. The results obtained give good bases for the practical use of the new instrument in high-energy neutron fields

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[en] Full text of publication follows: High-energy neutron fields (above 20 MeV), which are typical of secondary cosmic rays and the neutron field outside the shielding of particle accelerators, are especially important in terms of radiation protection due to their large contribution to total dose. A Bonner Sphere Spectrometer (BSS) is one of the most accurate and reliable instruments to measure neutron fluence rates up to several hundreds of MeV. The response functions of BSSs are usually calculated by means of Monte Carlo (MC) codes such as MCNPX, FLUKA, PHITS, MARS, GEANT4, and others. At neutron energies above 20 MeV calculated response functions may be uncertain up to a factor of 2 due to uncertainties in the theory (/model)- based reaction cross-sections on which all transport codes rely. Therefore, experimental calibration of BSSs in high-energy neutron fields is important for response validation. The uncertainties arising from the use of different transport codes and different INC models are discussed, with special emphasis on a calculational inter-comparison exercise initiated by EURADOS (European Radiation Dosimetry Group). Furthermore, experimental results from response measurements in quasi-monoenergetic high-energy neutron fields at the ring cyclotron facility of the Research Center for Nuclear Physics (RCNP), University of Osaka, Japan, are presented. The response of a complete set of Bonner spheres were for the first time measured at neutron energies of 244 MeV and 387 MeV and compared to calculations using various MC codes and models. (authors)

[en] Replicative synthesis of DNA in the brain of the adult frog was studied by light microscope autoradiography. Animals collected during the active period (May-June) and in hibernation (January) were used. In active frogs, 3H-thymidine labelling occurred mainly in the ependymal cells which line the ventricles. The mean labelling index (LI%) was higher in the ependyma of the lateral and fourth ventricles than in the ependyma of the lateral diencephalon and tectal parts of the mesencephalon. In the recessus infundibularis and preopticus the number of labelled cells (LCs) was several times greater than in the lateral parts of the third ventricle. LCs were seen subependymally only occasionally. The incidence of LCs in the parenchyma of the brain was much lower in most regions than in the ventricular ependyma; LCs were mainly small and, from their nuclear morphology, they were glial cells. The LI% reached the highest value in the septum hippocampi and in the nucleus entopeduncularis. In these locations, LCs were larger and closer in size to the nerve cells of these regions. From comparison with data obtained earlier in the brain of mammals, it is evident that the distribution of proliferating cells in the olfactory and limbic system is phylogenetically conservative. The occurrence of pyknotic cells in the same areas which contain LCs, suggests that cell division reflects in part the process of cell renewal observed in mammals. However, proliferating cells could also be linked to the continuous growth observed in non-mammalian vertebrates. In hibernating frogs, LCs and pyknoses were not seen or were found occasionally, which further indicates the functional significance of both processes

[en] The main purpose of the present calculations was the evaluation of the fluence-to-effective dose conversion coefficients for cosmic radiation in the atmosphere. During their work air crew members are exposed to elevated ionising radiation from cosmic radiation which shall be determined. Cosmic radiation in the Earth's atmosphere exhibits a complex environment consisting of neutrons, protons, photons, electrons, positrons, pions, muons and heavy ions. Their energy range extends up to hundreds of GeV. To calculate the dose components from the particle fluences in the atmosphere, the effective dose conversion coefficients of all particle types produced by the galactic cosmic rays have to be determined. In the high energy range (approximately above 10 MeV) there is only a limited number of data available in the literature. Only INFN (Instituto Nazionale di Fisica Nucleare) in Italy has published a consistent set of fluence-to-effective dose conversion coefficients for all kinds of radiation and incident energies up to 10 TeV, calculated by the FLUKA transport code. The aim of this work is to validate these earlier calculations performed by FLUKA using the high energy code MCNPX and fill in the gaps in the conversion coefficients as a function of particle energy

[en] In 1981 new recommendations on occupational limits for inhalation of ²²²Rn, ²²⁰Rn and their short-lived daughters were adopted by ICRP, based on epidemiological studies and dosimetric models. These recommended limits are derived from the basic dose and risk limits proposed by ICRP in 1977. The approaches to dose limitation are shortly outlined and the main results including estimation of the effective dose equivalents and recommended limits for radon daughters are summarized. (author)