EXPERIMENTAL STUDIES OF TRANSMUTATION OF 129 I BY SPALLATION NEUTRONS USING JINR DUBNA PHASOTRON
An intensive beam of 660 MeV protons was directed towards a lead target (not surrounded by shielding or neutron reflectors) for 10 minutes. On the top of the target were placed detectors and iodine samples. The neutron field and the transmutation of I were studied by the neutron activation analysis method. First simulations were compared to the experimental data. 1 Description of the experiment The collaboration ”Energy plus transmutation” works on benchmark experiments intended to test simulation programs, which shall be used in design of Accelerator Driven Systems. The work consist of a series of similar experiments, of which each is concentrated on a specific topic. Generally said, we study production of neutrons by spallation reactions on massive targets, their transport, and use for transmutation. Our experimental setups consist of heavy metal (Pb, W, Bi, U) targets of cylindrical shape to which a narrow beam of relativistic protons is directed. In the target protons cause spallations of heavy nuclei to nucleons, and smaller fractions of nucleus. Relativistic nucleons cause further spallations, and mostly neutrons of all energies from thermal up to the energy of the proton beam exit the target sideways. Such neutron production shall be used in the devices called ADS (Accelerator Driven Systems), which will be able to use a wider spectrum of nuclear fuel (Th, nuclear waste from thermal reactors), and their waste should be much less radioactive than the waste from thermal reactors. These systems cannot be built in smaller scale as a test model, and the accelerators to be added to the reactors will not be a cheap extension. That is why we need the precise descriptions of what will be going on in these systems. Our experiments are simplified setups of them, and are used as benchmark tests for the computer simulations that will be used to describe larger and more complicated systems. One of the experiments was held on Dubna Phasotron in December, 2003, and was focused on the studies of short-lived iodine isotopes production. We needed to make our measurements as soon as possible after the irradiation, and use as intensive proton beam as possible. The proton beam was provided by Dubna Phasotron, which accelerated the intensive proton beam to the energy 660 MeV. The beam was directed to the bare lead
MCNPX BENCHMARK TESTS OF NEUTRON PRODUCTION IN MASSIVE LEAD TARGET
Experiments on simplified ADS (Accelerator Driven System) setups are done at the Joint Institute for Nuclear Research Dubna. Relativistic protons are directed at heavy targets, and transmutation is studied in the neutron field produced. Experimental values are used to test program codes. In this study, "The Phasotron Experiment" and the MCNPX 2.4.0 simulations of the experimental setup are presented, the influence of the various parts of the setup on calculations is discussed, and the efficiency of parallel computing for simulations of similar experiments is studied. The experiment is quantitatively well described by MCNPX simulations, even when using a simplified description of the experimental setup. A cluster of computers in our laboratory showed that the speed of our calculations almost linearly increases with the sum of processor power. Many of our other experiments are well described by simulations, promising that MCNPX could well describe larger, and more complex ADS systems.
People and Society in Scotland
People and society in Scotland: a social history ofmodern Scotland, vol. I, 1760-1830, ed. T. M. Devine and R. Mitchison (John Donald in association with the Economic and Social History Society of Scotland, Edinburgh, 1988), pp. xii, 316. £10.00; vol. II, 1830-1914, ed. W. Hamish Fraser and R. J. Morris (Edinburgh, 1990), pp. xvi, 362. £12.50; vol. Ill, 1914-1990, ed. T. Dickson and J. H. Treble (Edinburgh, 1992), pp. xi, 287. £15.00.