No abstract

A modified version of MCNP5 has been developed to treat continuous-energy proton transport. This work is summarised in companion papers by Hughes et al. and Bull et al. (in these proceedings). An intrinsic part of this development effort has involved testing, verification and validation of a capability for simulating proton radiographs. This paper presents the results of calculations simulating various different test objects and the effects of alternative physics models. The significant physics processes include elastic scattering, multiple coulomb scattering, collisional energy-loss and straggling, magnetic fields and attenuation owing to nuclear interactions. Comparisons with experimental data are presented.

The developmental version of MCNP5 has recently been extended to provide for continuous-energy transport of high-energy protons. This enhancement involves the incorporation of several significant new physics models into the code. Multiple Coulomb scattering is treated with an advanced model that takes account of projectile and nuclear target form factors. In the next version, this model will provide a coupled sampling of both angular deflection and collisional energy loss, including straggling. The proton elastic scattering model is also new, based on recent theoretical work. Charged particle transport in the presence of magnetic fields is accomplished either by using transfer maps from the COSY INFINITY code (in void regions) or by using an algorithm adapted from the MARS code (in void regions or in scattering materials). Work is underway to validate and implement the latest versions of the Cascade-Exciton Model and the Los Alamos Quark-Gluon String Model, which will process inelastic nuclear interactions and generate secondary particles.

A detailed evaluation of the fuel-burnup dependent power distribution and the scram reactivity for the PIUS reactor design has been performed. The analyses were carried out using the CPM lattice physics and NODE-P2 core neutronics/thermal-hydraufics codes, and are based on the information provided in the PIUS Preliminary Safety Information Document.Cycle depletion calculations were performed for a set of nine representative initial core loadings and the threedimensional core power distributions were determined. These calculations indicate that the PIUS radial FAh and total Fa power peaking is stronger than that indicated by the PIUS reference-design values.The scram reactivity resulting from the injection of highly borated pool water was calculated for a series of timedependent linear ramp and square-wave pool flows. The three-dimensional distribution of the borated pool water throughout the core was modeled and the spatial reactivity effects of the distributed boron were determined. For pool flows that increase as a linear ramp, the spatial reactivity effects of the distributed boron were very small. In this case, a constant core-average boron reactivity coefficient can be used to model the PIUS scram reactivity.

A major purpose of the Techni cal Information Center is to provide the broadest dissemination possi ble of information contained in DOE's Research and Development Reports to business, industry, the academic community, and federal, state and local governments.Although a small portion of this report is not reproducible, it is being made available to expedite the availability of information on the research discussed herein. ^s"A 4 -5i?5/ 0# 03/0 -7 ORNL/rEDC S6/5