Analysis of Reliability-Critical Hydraulic Impact Conditions at WWER-1000 NPP Active Safety Systems

Abstract

An original method to determine the onset of conditions for reliabilitycritical hydraulic impacts for reliability analysis of active safety systems of nuclear power installations is proposed. The suggested method is based on determining the effect of head-flow characteristic delay onto hydraulic impact preconditions during the changes of pipeline system hydrodynamic parameters under transitional modes (e.g. in pump start-up). The delay time of responses to change in the hydrodynamic system parameters embodies the determining factor of head-flow characteristic’s inertance, depending on both design and technical parameters of system components (including pumps), and the hydrodynamic parameters change rate under transitional modes. Using the proposed method, the analysis of conditions for critical hydraulic impacts is performed for the primary high-pressure safety injection system of serial WWER-1000 nuclear power plants. The analysis results allow a conclusion that for this system the conditions leading to hydraulic impact due to the pump start are not reached. The developed method can be applied to any thermal and nuclear power facilities’ pipeline systems equipped with pumps.

Criteria and Conditions of Thermal Hydrodynamic Instability in the Circuits of Natural Circulation of Nuclear Power Plants in Case of Leak Accidents

“…The method is based on the fundamental thermodynamic principles of analysis of the influence of fluctuating pressure and flow disturbances in PSS-NC circuits on the conditions and consequences of THI in the process of accidents with circulation circuit leaks. According to these principles, if pressure and mass increase (or decrease) simultaneously and independently of each other in an equilibrium system, the system is unstable [9][10][11][12].…”

“…-Negative consequences for the reliability/safety of NPPs of this type of THI in PSB-PC can be: violation of safety functions for emergency cooling of the active zone of reactors and refueling of steam generators, hydrodynamic and thermal shocks in systems important for safety, etc. [9][10][11][12].…”

Модернізація Стратегій І Систем Управління Аваріями На Ядерних Енергоустановках З Їх Повним Тривалим Знеструмленням

“…Модернізація стратегій і систем управління аваріями на ядерних енергоустановках з їх повним тривалим знеструмленням (12) Рівняння руху живильної води у системі АЖНПП ПГ із загальною довжиною трубопроводу L: (13) Рівняння руху пари в паропроводі від ПГ:…”

Thermal hydraulic method of optimizing the thermal resistance of nuclear fuel of reactor installations

“…One of the current approaches to improve the efficiency of nuclear power plant (NPP) operation is to increase the depth of nuclear fuel (NF) burnup [1 -7] and others. Increasing the depth of nuclear fuel burnup (DNFB) can be achieved by modernizing the thermophysical properties of NF, in particular, in well-known experimental studies, reviewed, for example, in [8]; it was found that DNFB ~ n F −  ( 0 n  , F  is the parameter of thermal conductivity of NF).…”

“…Thus, an "artificial" decrease in core thermal conductivity NF increases DNFB (ceteris paribus). In practice, an "artificial" decrease in F  can be achieved by chemically adding to NF elements with reduced thermal conductivity [8]. The consequence of a relative decrease in F  (ceteris paribus) is a relative increase in temperature of NF ( ) F T and, accordingly, in DNFB.…”