ABSTRACT
The levels of residual radioactivity induced in Havar foils at the entrance of a high-pressure 18O-enriched water target used for the production of 18F- in a medical cyclotron with 16 MeV protons have been determined using high-resolution gamma-ray spectrometry. Whole body and skin dose rates arising from exposure to these foils during their periodic replacement have been estimated. The results indicate that irradiated foils do not represent a significant radiological hazard for the cyclotron operating staff and that no waste disposal difficulties should be encountered after an appropriate 'cooling' period of 2 years.
Subject(s)
Cyclotrons , Fluorine Radioisotopes/analysis , Isotope Labeling/methods , Occupational Exposure/analysis , Radiation Protection/methods , Radioactive Waste/analysis , Radiometry/methods , Radiopharmaceuticals/analysis , Body Burden , Computer Simulation , Equipment and Supplies/adverse effects , Fluorine Radioisotopes/adverse effects , Health Personnel , Humans , Isotope Labeling/adverse effects , Models, Biological , Radiation Dosage , Radiation Injuries/prevention & control , Radioactive Waste/adverse effects , Radiopharmaceuticals/adverse effects , Reproducibility of Results , Sensitivity and Specificity , Skin Physiological Phenomena , Whole-Body Counting/methodsABSTRACT
Concentrations of plutonium-239, plutonium-240, strontium-90 and total alpha-emitters have been measured in children's teeth collected throughout Great Britain and Ireland. The concentrations of plutonium and strontium-90 were measured in batched samples, each containing approximately 50 teeth, using low-background radiochemical methods. The concentrations of total alpha-emitters were determined in single teeth using alpha-sensitive plastic track detectors. The results showed that the average concentrations of total alpha-emitters and strontium-90 were approximately one to three orders of magnitude greater than the equivalent concentrations of plutonium-239,240. Regression analyses indicated that the concentrations of plutonium, but not strontium-90 or total alpha-emitters, decreased with increasing distance from the Sellafield nuclear fuel reprocessing plant-suggesting that this plant is a source of plutonium contamination in the wider population of the British Isles. Nevertheless, the measured absolute concentrations of plutonium (mean = 5 +/- 4 mBq kg-1 ash wt.) were so low that they are considered to present an insignificant radiological hazard.
Subject(s)
Air Pollution, Radioactive , Alpha Particles , Plutonium/analysis , Strontium Radioisotopes/analysis , Tooth/chemistry , Adolescent , Bone and Bones/chemistry , Female , Humans , Male , United KingdomABSTRACT
Schottky diodes have been used as room-temperature mixers of CO(2)-laser radiation. When a microwave local oscillator signal was introduced directly into the diode, beat notes between lasers separated by up to 69 GHz were observed. At CO(2) frequencies (30 THz) the photon energy exceeds the measured dc nonlinearities, and the device is expected to approach operation as a photon counter rather than a classical resistive mixer.
