VUJE, a.s.

Diagnostics, in-service inspections and equipment qualification

VUJE designs, develops and delivers special methods and single-purpose equipment for use by operators of power installations, and provides services in the field of inspections of material integrity, diagnostic of machinery, it evaluates material degradation, etc.

Thanks to the quality of its work, VUJE is successful not only in the Slovak Republic, but also abroad, e.g. in Hungary, the Netherlands, Sweden, France, and Spain. In the implementation of its professional tasks, VUJE combines first-class hardware with detailed professional knowledge of its staff.

Presentation for Diagnostics of Nuclear Power Components

VUJE performance in the field of diagnostics, in-service inspections and equipment qualification is focused on the following areas:

In-service inspections of material integrity

VUJE develops and produces advanced remotely controlled manipulators and mechanization facilities for material in-service inspections of selected components and for repairs of equipment in nuclear power plants. Remotely controlled manipulators are used in non-destructive inspections of all major components, such as main sealing plane of reactor pressure vessels, mechanical parts of reactor coolant pumps, main circulation piping, pressurizers, and primary manifolds and heat exchange tubes in steam generators. It develops methods for non-destructive inspections and test probes for the Eddy-current method.

In the field of in-service inspections of equipment material integrity in nuclear power plants in Sweden, the Netherlands, and Hungary, VUJE cooperates with foreign firms (NRG – the Netherlands, SIEMENS – Germany). Outside nuclear industry, VUJE applies its experience with non-destructive inspections of materials and weld joints also in the field of oil industry, chemistry and conventional engineering. Quality assurance system for these activities is ensured by the quality of personnel at the European level and by the state accreditation in the area in question.

Diagnostic systems

VUJE develops systems and delivers complete facilities for vibration monitoring and determination of the presence of free particles in selected points of nuclear units. Special emphasis is paid to the diagnostic of coolant leaks from reactor coolant systems, which is a component in the LBB methodology (“Leak Before Break”). The measurement part of the diagnostic systems consists of up to date components based on digital hardware (analog-digital transmitters, digital signal processors).

Evaluation modules in the delivered diagnostic systems are based on industrial personal computers using multitask operating system. The delivered diagnostic systems (including measurement circuits) are certified internationally and comply with strict criteria for electromagnetic compatibility, seismic resistance and resistance against the working environment (operation at high temperature and humidity of the surrounding environment). Also the diagnostic measurements of mechanical vibrations, the support and balancing of rotating machines, the tests of resistance and vibrational stability of electric and electronic equipment are covered by the VUJE activities accredited. Within the framework of non-accredited activities, VUJE detects coolant leaks from pressurized components. In piping systems with flowing coolant, it measures excitation dynamic forces of both hydraulic and acoustic origin and carries out experimental analysis of stress and strain in structural elements of machines, equipment, and structures.

Facilities for tests and repairs

VUJE also develops and produces modern remotely controlled tools for maintenance, repair, decontamination and manipulation with nuclear power plant equipment. Manipulators and their control systems are implemented based on proven industrial components. Besides complete equipment supply, VUJE provides also supporting activities for its use according to the requirements of operators.

Assessment of equipment lifetime

VUJE performs stress and strain analyses and lifetime calculations for components in nuclear power units by means of advanced computer tools (e.g., ADINA, CAEPIPE, PMD etc.). A specialized unit carries out integrity analyses of high-energy piping and pressure vessels (particularly of reactor pressure vessels) using up to date, internationally accepted procedures and by means of modern computer tools. On demands from operators and Slovak regulatory bodies, VUJE conducts acceptability analyses of defects found in components at nuclear power installations, develops temperature and pressure limiting curves for reactor coolant systems for both normal and accident conditions, and periodically assesses the lifetime of pressure components. VUJE designs and implements programs for the assessment of equipment life in instrumentation and control systems and in electric systems, mainly in cable distribution systems.

Structural analyses of structures and materials

VUJE uses a set of advanced computer codes such as LS-DYNA 3D for structural analyses of structures under static loading, e.g. during impact loading on protective barriers, in the case of container drop with spent fuel, during impacts of missiles from turbine blades, and for impact effects of isolation valves. It performs analyses of in-reactor structures under dynamic effects in the course of LOCA accidents.

VUJE analyzes the effects and mechanisms of material degradation and evaluates the level of damage. It monitors the conditions inside reactor pressure vessels under the effects of radiation by means of specimens. It delivers systems for post-accident evaluation of conditions in nuclear power units under operation by means of samples taken. It determines the effects of corrosion and erosion on materials in selected systems of both primary and secondary systems. It carries out reviews of operational defects in equipment by evaluating material conditions.

Equipment qualification

VUJE performs equipment qualification with the objective to demonstrate and document reliable compliance with required functions for selected equipment during both normal operational and accident conditions, to evaluate the current conditions of safety-elated equipment with regards the its qualified lifetime, and to develop recommendations and proposals for the operators how to ensure reliable and safe plant operation and maintain equipment qualification in the course of the whole lifetime.

VUJE carries out qualification tests in a newly built laboratory for the simulation of LOCA type accidents. For the performance of seismic tests, an accredited laboratory for seismic tests is available in VUJE.