Abstract: This study investigates the agglomeration and deposition characteristics of submicron UO₂F₂ particles (0.2 μm and 1 μm) within the pipe in UF₆ gas flow under low-vacuum conditions (4000 Pa) through numerical simulations. A kinetic model was developed within the Euler-Lagrange framework to describe particle agglomeration and deposition in gas-solid two-phase flow. The agglomeration model incorporates turbulent agglomeration and Brownian agglomeration, while the deposition model is based on a critical velocity approach derived from energy conservation. The effects of throttle structure, gas flow rate, and particle size on particle deposition and agglomeration were systematically analyzed. The results demonstrate that under low-vacuum conditions, inertial separation is the primary mechanism for particle deposition in both orifice plate and valve-equipped pipelines. Larger particles exhibit higher deposition ratios than smaller ones. In the orifice plate pipeline, particles are primarily entrained by recirculating gas and deposit on the pipe wall downstream of the orifice plate, forming annular or cylindrical deposition patterns. Increasing the gas flow rate raises the pressure ratio across the orifice plate, resulting in localized supersonic flow downstream and enhancing the recirculation zone intensity, thereby entraining more particles and further increasing the deposition ratio. In the valve-equipped pipeline, particles mainly deposit on the pipe wall near recirculation zones, forming three distinct rings at low flow rates or cylindrical shapes at high flow rates. Due to the stronger throttling effect of the orifice plate compared to the valve, the inertial separation of particles is more pronounced in the orifice plate pipeline, leading to higher particle deposition ratios. Analysis of the turbulent dissipation rate and collision kernel functions reveals that in the orifice plate pipeline at a gas flow rate of 90 g/s, the contributions of turbulent collisions and Brownian collisions to particle growth are comparable. Under other conditions, Brownian collisions play a more significant role in particle growth than turbulent collisions.