Observing nuclear neutrinoless double beta (0νββ82682ννQββ82ννββνν6νββνν) decay would be a revolutionary result in particle physics. Observing such a decay would prove that the neutrinos are their own antiparticles, help to study the absolute mass of neutrinos, explore the origin of their mass, and may explain the matter-antimatter asymmetry in our universe by lepton number violation. We propose developing a time projection chamber (TPC) using high-pressure νββ82682ννQββ82ννββνν6νββννSeFνββ82682ννQββ82ννββνν6νββνν gas and Topmetal silicon sensors for readout in the China Jinping Underground Laboratory (CJPL) to search for neutrinoless double beta decay of νββ82682ννQββ82ννββνν6νββννSe, called the Nνββ82682ννQββ82ννββνν6νββννDEx experiment. Besides being located at CJPL with the world’s thickest rock shielding, Nνββ82682ννQββ82ννββνν6νββννDEx combines the advantages of the high νββ82682ννQββ82ννββνν6νββνν (2.996 MeV) of νββ82682ννQββ82ννββνν6νββννSe and the TPC’s ability to distinguish signal and background events using their different topological characteristics. This makes Nνββ82682ννQββ82ννββνν6νββννDEx unique, with great potential for low-background and high-sensitivity 0νββ82682ννQββ82ννββνν6νββνν searches. Nνββ82682ννQββ82ννββνν6νββννDEx-100, a Nνββ82682ννQββ82ννββνν6νββννDEx experiment phase with 100 kg of SeFνββ82682ννQββ82ννββνν6νββνν gas, is being built, with plans to complete installation at CJPL by 2025. This report introduces 0νββ82682ννQββ82ννββνν6νββνν physics, the Nνββ82682ννQββ82ννββνν6νββννDEx concept and its advantages, and the schematic design of Nνββ82682ννQββ82ννββνν6νββννDEx-100, its subsystems, and background and sensitivity estimation.