AN ANALYSIS OF THE ADU PRECIPITATION SYSTEM AND ITS CRITICALITY PREVENTION IN NUCLEAR FUEL FABRICATION FACILITIES

Abstract

The Ammonium Diuranate (ADU) precipitation process is primarily used to prepare natural U02 powder used for Canadian Deuterium Uranium (CANDU) type reactors. It can also be used to produce U308 enriched powder from uranyl fluoride liquor for research reactor fuels. In this study, two mathematical models (I & IT) that describe the dynamic behavior of the ADU precipitation system inside BR-5005 Semibatch Precipitation I Reactor of the Fuel Manufacturing Plant (FMPP) at Inshas site were developed. The only difference between them is the mathematical expression regarding the reaction rates in the energy balance equation .The two models were built of a set of non linear ordinary differential and algebraic equations representing the volume change in the system, initial solution density, overall balance, component balance, reaction rates, and overall energy balance of the precipitation system. The models'equations were I solved using a FORTRAN-90 computer code based on Runge- Kutta 4 technique. A comparison of the two models'output with the data taken from the plant operating records as a sort of model validation has been carried out. Model I, could be used as a tool to represent the ADU precipitation system during operation. This is because the temperature values obtained are quite near to the real one, and while the model II cannot represent the system more closely in normal I operating conditions. Model I, could also be used as a tool for a production consequence analysis or as the base for early knowledge to provide vital information to the plant operator during a specific batch, and/or in case of change of any of the operating conditions. Model II, could be used as a tool to represent the ADU precipitation system, only in the case of low rate ofNRtOH addition, with a little mass of uranium. All the static calculations using Monte Carlo Code (MCNP4A) for the precipitation reactor were reviewed in this study in order to understand the moderation curve of the precipitation system (relation between HIU ratio & k). The moderation curve obtained was interpolated using Lagrang's interpolating polynomial technique and was used to concentrate on the criticality prevention during this I process.