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The air-scattered radiation (Skyshine) is commonly a primary contributor to the public radiation exposure at distant locations form a high-energy particle accelerator facility. We have reported the results of the first series of measurement of skyshine from neutrons, using superheated bubble dosimeters. We have continued our measurements of skyshine, produced during "typical" operational condition at the National Superconducting Cyclotron Laboratory (NSCL). The measurements were carded out using the BD-100R Bubble Dosimeters with sensitivities of 470 nSv and 220 nSv per bubble at 20 °C, with an accuracy of ± 20% when calibrated using the [sup 241]AmBe neutron spectrum. The dosimeters were placed at 25 and 50 meters from a point on the shielding roof of the NSCL's Analysis Hall, and 75, 100, and 115 meters from this point but about one to two meters above the floor of the NSCL facility at these distances. The skyshine neutron dose equivalents were measured for the [sup 4]He[sup 2+], [sup 13]C[sup +4], and [sup 20]Ne[sup 6+] beams at the energy of 140 MeV/A, 100 MeV/A and 100MeV/A respectively. [ABSTRACT FROM AUTHOR]

Adequate radiation shielding is vital to the safe operation of modem commercial medical cyclotrons producing large yields of short-lived radioisotopes. The radiological shielding constitutes a significant capital investment for any new cyclotron-based radioisotope production facility; hence, the shielding design requires an accurate cost-benefit analysis often based on a complex multi-variant optimization technique. This paper demonstrates the application of a Genetic Algorithm (GA) for the optimum design of the high yield target cave of a Medical Cyclotron radioisotope production facility based in Sydney, Australia. The GA is a novel optimization technique that mimics the Darwinian Evolution paradigm and is ideally suited to search for global optima in a large multi-dimensional solution space. [ABSTRACT FROM AUTHOR]