Investigation of Spatial and Temporal Aspects of Airborne Gamma Spectrometry: Final Report

A study has been conducted which demonstrates the reproducibility of Airborne Gamma-ray Spectrometry (AGS) and the effects of changes in survey parameters, particularly line spacing. This has involved analysis of new data collected from estuarine salt marsh and upland areas in West Cumbria and SW Scotland during three phases of field work, in which over 150000 spectra were recorded with a 16 litre NaI(Tl) detector. The shapes and inventories of radiometric features have been examined. It has been shown that features with dimensions that are large relative to the survey line spacing are very well reproduced with all line spacings, whereas smaller features show more variability. The AGS technique has been applied to measuring changes in the radiation environment over a range of time scales from a few days to several years using data collected during this and previous surveys of the area. Changes due to sedimentation and erosion of salt marshes, and hydrological transportation of upland activity have been observed

An imaging neutron/gamma-ray spectrometer

We present the test results of a neutron/gamma-ray imaging spectrometer for the identification and location of radioactive and special nuclear materials. Radioactive materials that could be fashioned into a radiation dispersal device typically emit gamma rays, while fissile materials such as uranium and plutonium emit both neutrons and gamma rays via spontaneous or induced fission. The simultaneous detection of neutrons and gamma rays is a clear indication of the presence of fissile material. The instrument works as a double-scatter telescope, requiring a neutron or gamma ray to undergo an interaction in two detectors to be considered a valid event. While this requirement reduces the detector efficiency, it yields information about the direction and energy of the incident particle, which is then used to reconstruct an image of the emitting source. Because of this imaging capability background events can be rejected, decreasing the number of events required for high confidence detection and thereby greatly improving its sensitivity. The instrument is optimized for the detection of neutrons with energies from 1-20 MeV and gamma rays from 0.4 to 10 MeV. Images and energy spectra for neutron and gamma rays are reported for several sources including depleted uranium and plutonium. In addition, the effect of neutron source shielding is investigated

Activities of \gamma-ray emitting isotopes in rainwater from Greater Sudbury, Canada following the Fukushima incident

We report the activity measured in rainwater samples collected in the Greater Sudbury area of eastern Canada on 3, 16, 20, and 26 April 2011. The samples were gamma-ray counted in a germanium detector and the isotopes 131I and 137Cs, produced by the fission of 235U, and 134Cs, produced by neutron capture on 133Cs, were observed at elevated levels compared to a reference sample of ice-water. These elevated activities are ascribed to the accident at the Fukushima Dai-ichi nuclear reactor complex in Japan that followed the 11 March earthquake and tsunami. The activity levels observed at no time presented health concerns.Comment: 4 pages, 8 figure