A nucleonic analysis of the Engineering Test Facility neutral-beam-injector-duct and vacuum-pumping-duct shields has been made using a hybrid Monte Carlo/discrete-ordinates method. This method used Monte Carlo to determine internal and external boundary surface sources for subsequent discrete-ordinates calculations of the neutron and gamma-ray transport through the shields. Confidence was provided in both the hybrid method and the results obtained through a comparison with three-dimensional Monte Carlo results. Also determined in the analysis were the energy and angular distributions of neutrons and gamma rays entering the neutral-beam-injector duct from the toroidal plasma chamber, as well as exiting the duct into the neutral-beaminjector chamber. In addition, the energy and angular distributions of neutrons entering the vacuum-pumping chamber were determined. I.
Calculations have been performed on the Maine Yankee Power Plant to obtain threedimensional neutron fluxes using the spatial synthesis with the two-dimensional discrete ordinates code DORT(Ref. l), the three-dimensional discrete ordinates code THREEDANT BackgroundThe computation of neutron fluxes from the core out to and within the shield tank has always been a difficult problem to solve accurately and easily. For example, traditional methods for use in the analysis of pressure vessel damage resulting from neutron irradiation have primarily relied on two-dimensional transport calculations and a spatial-synt hesis methodology to generate three-dimensional fluxes from the results of two two-dimensional calculations. Such synthesis methodology makes assumptions on the spatial separability of the neutron flux and results in additional analysis uncertainty. Three-dimensional calculations offer the possibility of obtaining the required neutron fiuences more efficiently and more accurately.The Reactor Physics Group at Yankee Atomic Electric Company and the Radiation Transport Group at Los Alamos National Laboratory have investigated some of these issues through calculations on Maine Yankee. This effort was divided into three parts. This paper presents the results of the final stage of this effort where full-core calculations were made using the three-dimensional codes THREEDANT and MCNP, and the synthesized three-dimensional results obtained from two-dimensional DORT calculations. CalculationsThe material and geometric bases for these calculations is the Maine Yankee power plant (Ref 4). A one-eight azimuthal cross section of the reactor, at core midplane, is shown in Figure 1. The axial extent of the core is from -173.61 to +173.61 cm. All three calculations described herein used this basic information as a starting point and then made whatever geometric and material approximations were necessary for the code to be used. Because of the flexibility of the MCNP code, geometric detail is not limited other than in the complexity and size of the input file.The same XY pinwise power distribution, corresponding to cycle 1, was available for the development of the source for each of the calculational methods. In the axid direction,
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The theory of two-dimensional cross-6ection and secondary-energy-di.stributi on (SED) sensitivity was implemented by developing a two-dimensional sensitivity and uncertainty analyaia code, SENSIT-2D. Analyses of the Fusion Engineering Design (FED) conceptual inboard shield indicate that, although the calculated lmcertainties in the 2-D model are of the same order of magnitude as those resultinf rom the 1-D rr,tdel,there might be severe differences. The more complex the geometry, the more compulsory s 2-D analysis becomes. Specific reriulta show that the uncertainty for the integral heating of t}.e toroicfal field (TF) coil for the FED is 114.6%. The main contributors to the ,ross-section uncertainty q rc chromium and iron. Contributions to the total uncertainty were smaller for nickel, copper, hydrogen and carbon. All arlalysen were performed with the Los Alamos f+2-group cross-section library generated from ENDF/B-V data, and the COVFILS covrriance matrix libtary,
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