Pressurized water reactor fuel corrosion-related unidentified deposit and its related safety issues – II. Corrosion product deposition and heat transfer modeling

CRUD depositions on fuel cladding are the main cause of power shift and localized corrosion in nuclear power plants. This paper is the second of a three-part study concerning the deposition of corrosion products and its related safety issues. In this paper, analytical modules are proposed to predict CRUD growth and internal heat and mass transfer. CRUD growth depends on dynamic balance between corrosion product deposition, flow erosion and chemical equilibrium. In the multi-module iteration, the CRUD thickness is updated first followed by internal temperature and concentration fields. Temperature affects the chemical equilibrium, deposition and erosion equilibrium on CRUD surfaces. The accuracy and reliability of the coupling method are verified by experimental results. The difference of effective thermal conductivity between previous experimental results and calculation results is less than 0.4384 W/(m × K) and the cladding temperature relative error between WALT Loop results and calculation results is less than 1 %. The influences of operation conditions are evaluated. Coolant with lower pH reduces corrosion product solubility leading to high CRUD thickness. The main source of CRUD growth is from soluble precipitation, because CRUD depositions formed from soluble precipitation are thicker than those from the insoluble particles of the same concentration. High heat flux increases CRUD growth, internal wick boiling and boron hideout. Hydrogen in reactor application range has a minimal meaningful effect on CRUD growth, wick boiling and boron hideout. This study provides a precise method for further understanding CRUD growth and its internal multi-physical phenomena to alleviate CRUD-related safety issues.