AMBIENT DOSE EQUIVALENT RECEIVED AT 15 MV LINAC ENVIRONMENTS DUE TO PHOTONEUTRONS CONTAMINATION.

Mapping of the photoneutron spectrum and flux performed at several positions over the treatment table of a 15 MV medical linac. Neutron activation technique has been applied to obtain the neutron spectra in the mixed γ -n field. Thick foils have been used due to the low neutron flux and the measurements were unfolded using the MINUIT minimizer. GEANT4 code simulations have been performed to reproduce the photoneutrons' spectrum and estimate the flux along the treatment table. The mixed radiation field around medical linear accelerator was evaluated and the variation of the ambient dose equivalent over the treatment table was estimated. Photoneutrons' ambient dose equivalent inside the irradiation field estimated as 0.56 ± 0.05 while the peripheral as 0.42 ± 0.04 mSv Gy-1. The effective dose inside the irradiation field is ranged between 0.004 and 0.049 while the peripheral up to 0.035 mSv Gy-1.

Post-Chernobyl 137Cs in the atmosphere of Thessaloniki: a consequence of the financial crisis in Greece.

The background radiation level of (137)Cs at the urban atmosphere of Thessaloniki has been increased during the recent decade only due to the Fukushima accident fallout. Since then, no other signal of (137)Cs was observed until the winter period of 2013, when slightly elevated (137)Cs concentrations were measured. The (137)Cs signals observed were up to 12 µBq m(-3), mainly during holidays and weekends followed by lower or even non-detectable activities in the next working days. Those episodes are attributed to the increase of biomass products combustion for residential heating as this year the tax of oil for heating was drastically raised as a consequence of the financial crisis. A preliminary survey of various wood products as well as of bottom ashes from different domestic burning devices is presented. (137)Cs concentrations up to 11 Bq kg(-1) were measured in wood products and up to 500 Bq kg(-1) in ash samples.

Radioiodine and radiocesium in Thessaloniki, Northern Greece due to the Fukushima nuclear accident.

Radioiodine ((131)I) in air and rainwater as high as 497 µBq m(-3) and 0.7 Bq L(-1), respectively, as well as (137)Cs and (134)Cs in air as high as 145 µBq m(-3) and 126 µBq m(-3), respectively were recorded in Thessaloniki, Northern Greece (40°38'N, 22°58'E) from March 24, 2011 through April 09, 2011, after a nuclear accident occurred at Fukushima, Japan (37°45'N, 140°28'E) on March 11, 2011.