DagSolid: a new Geant4 solid class for fast simulation in polygon-mesh geometry.

Even though a computer-aided design (CAD)-based geometry can be directly implemented in Geant4 as polygon-mesh using the G4TessellatedSolid class, the computation speed becomes very slow, especially when the geometry is composed of a large number of facets. To address this problem, in the present study, a new Geant4 solid class, named DagSolid, was developed based on the direct accelerated geometry for the Monte Carlo (DAGMC) library which provides the ray-tracing acceleration algorithm functions. To develop the DagSolid class, the new solid class was derived from the G4VSolid class, and its ray-tracing functions were linked to the corresponding functions of the DAGMC library.

An apparatus for the study of high temperature water radiolysis in a nuclear reactor: calibration of dose in a mixed neutron/gamma radiation field.

The cooling water of nuclear reactors undergoes radiolytic decomposition induced by gamma, fast electron, and neutron radiation in the core. To model the process, recombination reaction rates and radiolytic yields for the water radical fragments need to be measured at high temperature and pressure. Yields for the action of neutron radiation are particularly hard to determine independently because of the beta/gamma field also present in any reactor.