Three-dimensional Monte Carlo Code Research Articles

Edge impurity ion analysis using plasma ion mass spectrometry

In this paper we describe results from a new design of plasma ion mass-spectrometer (PIMS) which can resolve the ion energy parallel to the total magnetic field. The experimental ratios of the collector signals for different charge states are fitted to the results from a three-dimensional Monte Carlo code. This procedure determines the impurity ion temperature and transmission function for the instrument. Transmission corrected spectra are then used to calculate impurity concentrations, charge state distributions and Z eff in the boundary.

Establishment of a simple neutron calibration field from a moderated 252Cf source : Part I. Design and calculation of the simple neutron calibration field

This paper describes the development and standardization of simple neutron reference calibration fields. These fields have been arranged for calibration of neutron detectors particularly used for radiation control and environmental measurements, having four different neutron spectra formed by a 252Cf source with or without moderators of iron, carbon or polyethylene. These calibration fields are independent of room-scattered neutrons, since they use only direct neutron components which are obtained by subtracting the results with shadow blocks from the results without those. The absolute energy spectra and dose equivalents of direct neutrons and room-scattered neutrons, and the effect of a shadow shield have been calculated by the one-dimensional ANISN-W, two-dimensional DOT-3.5 discrete ordinates codes and the three-dimensional MORSE-CG Monte Carlo code, for these four fields.

Skyshine Radiation from a Pressurized Water Reactor Containment Dome

AbstractThe radiation dose rates resulting from airborne activities inside a postaccident pressurized water reactor containment are calculated by a discrete ordinates / Monte Carlo combined method. The calculated total dose rates and the skyshine component are presented as a function of distance from the containment at three different elevations for various gamma-ray source energies. The one-dimensional ANISN code is used to approximate the skyshine dose rates from the hemisphere dome, and the results are compared favorably to more rigorous results calculated by a three-dimensional Monte Carlo code.

Neutron streaming analysis for helical geometry system, heliotron-H fusion power reactor.

Nuclear analysis was carried out for the Heliotron-H reactor. Due to the helical geometry of the system, 14 MeV neutron streaming inherent in the reactor exists; some of source neutrons generated in the plasma region can see the coil shield surface in a direct line-of-sight manner and stream through blanket regions without collisions. With an appropriate coordinate transformation from the helical geometry, analysis on the neutron streaming was made possible by a method coupling the three-dimensional Monte Carlo code and two-dimensional discrete-ordinates transport code. For each radiation response parameter in the helical magnet, the streaming neutrons contribute 40–50%. This fact strongly suggests the need of taking account of the contribution from the streaming neutrons to provide an adequate shielding for the helical magnet.

Helical Geometry Effect on Tritium Breeding in Heliotron Fusion Reactor Blanket

An examination is made of the helical geometry effect on the tritium breeding in the Heliotron reactor blanket. Calculations are performed with the threedimensional Monte Carlo code MORSE-I for the cylindrical, torus and helical geometry models, each approximating the configuration of the Heliotron reactor in various degrees. A comparison of the tritium breeding ratios obtained between these models indicates that the helical geometry effects would be modest. However, it is found that there exists neutron streaming through between blanket regions, due to the helical geometry of the system.

Gamma-Ray Energy Deposition in Silicon Detectors

Calculations of the gamma-ray energy deposition spectrum have been performed for a silicon ionization dosimeter based on a silicon surface barrier detector. The technique used was a coupled photon-electron transport calculation using the three-dimensional Monte Carlo code, SANDYL. Comparison of calculated pulse-height spectra and measurements of standard calibrated gamma sources demonstrated the need to take into account the nonuniformity of the charge collection efficiency in the device. To this end, measurements were made of the radial dependence of the charge collection efficiency and sensitive volume. These results yielded an improved model and improved agreement between calcullation and experiment.

Neutron Inelastic Scattering fromZr90

Excitation functions have been measured for $\ensuremath{\gamma}$-ray emmission following neutron inelastic scattering from the 2.186-, 2.319-, 2.748-, 2.748-, 3.077-, 3.310- and 3.84-MeV levels of $^{90}\mathrm{Zr}$ for neutrons in the energy range 2.85 to 5.97 MeV. The $\ensuremath{\gamma}$ rays were detected at 55\ifmmode^\circ\else\textdegree\fi{} to the incident neutron beam using an anti-Compton spectrometer consisting of a NaI(T1) annulus enclosing a 45-${\mathrm{cm}}^{3}$ Ge(Li) detector. Multiple-scattering corrections were accounted for with the three-dimensional Monte Carlo code 05R. $\ensuremath{\gamma}$-ray angular distributions were calculated and used to deduce the total neutron inelastic scattering cross section from the cross section measured at 55\ifmmode^\circ\else\textdegree\fi{}. These cross sections are in agreement with values calculated from Hauser-Feshbach theory corrected for level-width fluctuations and with previous measurements.

Delayed-Neutron Multiplication in Far-Subcritical Systems

Three methods are presented for calculating the multiplication of the delayed-neutron response which occurs in far-subcritical samples of fissionable material irradiated by an external neutron source: a three-energy group analytic expression; the zero prompt-lifetime approximation in conjunction with a one-dimensional steady-state transport theory code; and a three-dimensional time-dependent Monte Carlo code. The accuracy and limitations of the calculational techniques are demonstrated by a comparison with experimental measurements.