Flow stability analysis of a particle bed reactor fuel element

This paper describes an investigation of thermal hydraulic flow stability in a particle bed reactor fuel element. The work starts from an adaptation of the stability criterion used by Bussard and DeLauer (1958 and 1965). A one-dimensional evaluation was then performed, using the Ergun relation (1952) to evaluate numerically the pressure drop. If one considers the entire element from cold frit to hot frit, the analysis would indicate flow stability for all conditions. When one uses the pressure drop in the bed for the criterion, the resultant criterion curve has the same shape as the curve obtained by using the Bussard-DeLauer methodology, but predicts higher flow rates are required for stability. A two-dimensional thermal hydraulic study used to verify the one-dimensional analysis yields consistent results. Finally, results from an evaluation to determine if the heat deposition shape within the bed could impact the stability show that, for a chosen average element operating condition, a flat deposition shape was stable, while an axial cosine shape was unstable