The international Jules Horowitz Material Testing Reactor (JHR) is under construction at the CEA Cadarache research center in southern France. Its first criticality is foreseen by the beginning of the next decade. In order to perform JHR neutron simulations, a specific calculation scheme, named Horowitz Reactor simulation Unified System 3-Dimention/Neutron (HORUS3D/N), has been developed since the 2000s for the very first JHR definition studies. Then it was improved and modified in parallel with the JHR design evolution, integrating the most accurate neutron codes and nuclear data libraries. This paper describes the very latest version of HORUS3D/N, named HORUS3D/N v4.2. The industrial route is based on the APOLLO2.8–4 and CRONOS2.10 deterministic codes and the European nuclear data library JEFF3.1.1. Besides, HORUS3D/N v4.2 includes the APOLLO2.8/REL2005/CEA2005 package recommendations applied for light reactor studies. This paper also provides the performance quantification of HORUS3D/N v4.2 as a result of the Verification & Validation—Uncertainty Quantification (V&V–UQ) process. This reference calculation scheme is now a basis for the development of the neutron calculation tool dedicated to JHR operation and loading studies.