STRUCTURAL INTEGRITY VERIFICATION OF A PRIMARY CIRCUIT PUMP FLYWHEEL FOR A NUCLEAR RESEARCH REACTOR

摘要

The flywheels on nuclear reactor coolant pump motors provide inertia to ensure a slow decrease in coolant flow in the event of loss of power; thus preventing possible fuel damage due to the reduced coolant flow. During operation at normal speed, a flywheel has sufficient kinetic energy to produce high-energy missiles and excessive vibration of the coolant pump assembly if the flywheel should fail. It is thus important to evaluate the fracture properties of the material to ensure it can withstand the applied stress. The structural integrity of a large steel flywheel to be used in the primary cooling system of the OPAL research reactor at Lucas Heights was evaluated according to the requirements of the US Nuclear Regulatory Commission guide RG 1.14. The guide was developed for nuclear power plants where significant over-speeds in pumps are possible. In the OPAL reactor at ANSTO such pump over-speeds are not possible, however, the code was used to demonstrate the incredibility of failure of the flywheel. An experimental program determined the fracture toughness and tensile properties of the flywheel material; thick section AS 3678 Grade 350 plate. Revision 4 of the well-validated British Energy R6 defect assessment procedure was used to an-alyse the critical speed and crack length for the flywheel using the two-component failure assessment diagram which considers brittle fracture and plastic collapse. The results of the evaluation are presented in this paper, and illustrate what can be accomplished through the application of modern methods of integrity assessment.