AbstractThe Monte-Carlo simulation of correlation measurements that rely on the detection of fast neutrons and photonsfrom fission requires that particle interactions in each history be described as closely as possible. The MCNP-PoliMi 1 code has been developed from the standard MCNP code to simulate each neutron–nucleus interaction as closely aspossible.Inparticular,neutroninteractionandphotonproductionaremadecorrelatedandcorrectneutronandphotonfission multiplicities have been implemented. The code output consists in relevant information about each collision, forexample the type of collision, the collision target, the energy deposited, and the position of the interaction. A post-processing code has also been developed and can be tailored to model specific detector characteristics. These featuresmake MCNP-PoliMi a versatile tool to simulate particle interactions and detection processes. The application of theMCNP-PoliMi code to simulate neutron and gamma ray detection in a plastic scintillator is presented.r 2003 Elsevier B.V. All rights reserved.