Development of the Conceptual Design of a New Advanced Neutron
Source at JINR – fast pulse NEPTUN reactor at JINR

1. The scientific program and the concept of the suite of instruments for conducting research in condensed matter physics, nuclear physics and applied research at the new NEPTUN pulsed reactor.
2. A working version of the dynamic bending model and evaluation of the effect of the pellet structure of fuel elements (compared to the rod structure) on the reactivity of dynamic bending at the beginning of the fuel lifetime and verification of calculations at RFNC-VNIITF. Technical specification for conducting experiments to check the shape of the bending of a fuel element prototype under rapid heating in the neutron flux of pulsed reactors.
3. Obtaining a permit for the use of nuclear materials that are exclusively in federal ownership (NM EFO). Production of the first batch of neptunium oxide for the refinement of the fuel manufacturing technology for experimental fuel rods and conducting pre-reactor studies of fuel compositions.
4. Evaluation of temperature shape change of the vessel, safety casing and reactivity modulator of the NEPTUN reactor. A list of experimental tests of chosen technical solutions to justify the design of the reactor. Working design documentation for a full-scale test stand of the reactivity modulator. Start of the manufacturing of the test stand of the reactivity modulator in accordance with the developed working design documentation. Technical specifications for the development of preliminary design and infrastructure projects.
5. Selection of optimal materials for use as a cryogenic moderator at the new NEPTUN reactor. Development of working design documentation for a full-scale test stand of a mesitylene-based cryogenic moderator with a system for fast loading and unloading of working material.

1. Approval of the technical specification, the program of pre-reactor studies of the properties of fuel compositions for fuel elements of the NEPTUN reactor and the conclusion of an agreement for R&D between JINR and JSC VNIINM for 2022-2023.
2. Assessment of the degree of applicability of the harmonic oscillator model, refinement of parameters corresponding to thermal processes in the real NEPTUN reactor. Calculations of dynamics for the case of a small gap in the supports. Preparation of initial data for verification of calculations in RFNC-VNIITF (SC Rosatom).
3. Preliminary scientific program and the concept of a suite of scientific instruments for conducting research in condensed matter physics, nuclear physics and applied research at the new NEPTUN pulsed reactor (IBR-3).
4. Approval of the technical specification and the conclusion of an agreement for R&D to optimize the reactivity modulator of the NEPTUN reactor between JINR and NIKIET. Beginning of elaboration of a list of experimental tests of the chosen technical solutions. Development of working design documentation for the test stand of the reactivity modulator.
5. Analysis of the efficiency of using hydrogen-containing materials (methane, triphenylmethane, liquid hydrogen, deuterium, etc.) as a cryogenic moderator at the new NEPTUN reactor (IBR-3) and their comparison with mesitylene. Development of working design documentation for a chamber-simulator of a cryogenic mesitylene-based moderator with a system for fast loading and unloading of working material.