In case of beyond design basis accidents at NPP power units with VVER the experts of work groups are gathered in Information analytical center of Rostechnadzor. These working groups include experts on reactor plant technological equipments and radiological safety. Their tasks embrace current situation diagnosis and prognosis of accident progress.To perform prognosis it is required to use the special models providing high calculation rate.
For the reactor plant modeling it is possible to use best-estimate codes which advantage is high precision. However, calculation rate of these codes is not enough to accident prognosis. Besides, during the accident experts do not have comprehensive information about emergency power unit. Necessity of fast rather than precise calculation forces to perform variant calculations.
The other group of codes employs homogeneous coolant flow approach. The advantage of these codes is high calculation rate of quite detailed reactor plant model. Main disadvantage is relatively rough modeling in case of loss of coolant accident.
A methodology of modeling accidents with large break loss of coolant accident from the main coolant circuit of the NPP with VVER type power unit is presented in this article. The methodology is aimed at calculation of the primary circuit pressure using a model of a homogeneous coolant flow.
The described methodology is implemented in models for rapid-assessment of VVER type power unit’s safety functions. These models are applied by Information analytical center of Rostechnadzor experts during emergency response.The methodology provides necessary speed of calculation and numerical stability in the simulation of accidents with large break loss of coolant accident from the main coolant circuit.
Keywords: modeling, break, coolant, VVER, rapid assessment, homogeneous model, methodology.
Article language: Russian. Pp. 23–31. DOI: 10.26277/SECNRS.2020.97.3.003.
