A novel vertebrate system for the examination and direct comparison of the relative biological effectiveness for different radiation qualities and sources.

PURPOSE: The recent rapid increase of hadron therapy applications requires the development of high performance, reliable in vivo models for preclinical research on the biological effects of high linear energy transfer (LET) particle radiation. AIM: The aim of this paper was to test the relative biological effectiveness (RBE) of the zebrafish embryo system at two neutron facilities. MATERIAL AND METHODS: Series of viable zebrafish embryos at 24-hour post-fertilization (hpf) were exposed to single fraction, whole-body, photon and neutron (reactor fission neutrons () and (p (18 MeV)+Be, = 3.5 MeV) fast neutron) irradiation. The survival and morphologic abnormalities of each embryo were assessed at 24-hour intervals from the point of fertilization up to 192 hpf and then compared to conventional 6 MV photon beam irradiation results. RESULTS: The higher energy of the fast neutron beams represents lower RBE (ref. source LINAC 6 MV photon). The lethality rate in the zebrafish embryo model was 10 times higher for 1 MeV fission neutrons and 2.5 times greater for p (18 MeV)+Be cyclotron generated fast neutron beam when compared to photon irradiation results. Dose-dependent organ perturbations (shortening of the body length, spine curvature, microcephaly, micro-ophthalmia, pericardial edema and inhibition of yolk sac resorption) and microscopic (marked cellular changes in eyes, brain, liver, muscle and the gastrointestinal system) changes scale together with the dose response. CONCLUSION: The zebrafish embryo system is a powerful and versatile model for assessing the effect of ionizing radiation with different LET values on viability, organ and tissue development.

Neutron activation and prompt gamma intensity in Ar/CO2-filled neutron detectors at the European Spallation Source.

Monte Carlo simulations using MCNP6.1 were performed to study the effect of neutron activation in Ar/CO2 neutron detector counting gas. A general MCNP model was built and validated with simple analytical calculations. Simulations and calculations agree that only the 40Ar activation can have a considerable effect. It was shown that neither the prompt gamma intensity from the 40Ar neutron capture nor the produced 41Ar activity have an impact in terms of gamma dose rate around the detector and background level.

A simplified technique to determine the self-absorption correction for sediment samples.

A self-absorption correction factor is required for the determination of the radioactive isotope concentration in sediment samples at the low-energy region. A simplified technique for this correction factor for a well-type HP germanium detector is described. This correction is especially important when the ratio between the sample density and reference sample density (rho(sa.)/rho(re)) is greater than approximately 1.4.