Optimization and Long-Life Validation Methods for EGC

Abstract

The methods and results of accelerated tests performed on fuel and structural materials, individual units and an entire EGC for computational and experimental validation of service-life-power characteristics are examined for long-life (≥7 yr) EGC operating regimes. The results of such studies provide the requisite initial data for the KIM software system used to model the service-life behavior of EGC taking account of the interaction of the main service-life-determining processes. It is shown on the basis of complex computational and experimental studies that the time required for reactor tests of EGC in order to validate a long service life, including for dual-regime operation as part of an NPP, can be reduced.Computational modeling of the behavior of an electricity generating channel (EGC) performed at the Luch Research Institute and Scientific Industrial Association (NII NPO Luch) is being done using the KIM software system, which makes it possible to investigate the thermoelectric characteristics of EGC, mass transfer in fuel elements and the deformation state of fuel elements [1]. The following are determined from the computational results:• electric potential distribution, current density and temperature of the electrodes, voltage and electric power of the EGC; • temperature distribution in the interior of a fuel kernel comprised of uranium dioxide as well as along gas-venting setups with protective perforated screens; • fuel configuration in a fuel element during radial and axial mass transfer; • heat removal through the gas-venting setup; • restructuring of the initial kernel structure; • rate of swelling of the fuel; • deformation of the emitter by a swelling kernel; and • variation of the interelectrode gap width along the EGC. Intra-and extra-reactor tests of materials, individual units and an entire EGC show that the processes enumerated above are service-life-determining for regular operating regimes. The results obtained provide the requisite initial data for KIM and at the same time direct experimental confirmation of the energy and service-life characteristics of EGC according to the aggregate of all the processes studied within the time frame of the tests (Fig. 1).The information value of the experimental data used in the calculations increases considerably if they reflect the specific nature of the long-time service life. This served as a basis for the development and implementation of the methods examined in the present article for performing accelerated tests of materials and individual units of an EGC.The methodological direction of development of methods for performing accelerated tests consisted of determining the accelerating factors and their subsequent mutual effect using a complex computer program.