Research > Program No. 2: Structural and System Diagnostics > RA3: Simulating severe accidents of NPP of new generation

RA3: Simulating severe accidents of NPP of new generation

Group of devices falling into the category of severe accidents consists of three devices. Equipment LOCA (Loss of coolant accident), gamma irradiation and high voltage. These devices form a complex that is able to expose the EUT to such conditions as would occur in the event of a severe accident at a nuclear power plant or separately.

Equipment LOCA plays a vital role in the safety of nuclear power plants, especially in emergency mode. In surround nuclear reactor (containment) is full of equipment working on the electrical principle. Most often the power cables pumps, sensors, communication cables, etc. You must be able to operate not only under normal conditions, but also in case of non-standard events. One of the worst such event, the leakage of coolant from the primary circuit into the containment.

In order to guarantee the functionality of these devices, it is necessary to test their operation in conditions similar to the situation in the containment during an accident, ie in emergency and post-emergency condition. When the accident unit is exposed to high radiation dose, the presence of superheated steam at high pressure. Furthermore, there may be a spray shower bath. Moreover, the primary refrigerant is pure demineralized water, but boric acid compound, water thyosíranu and other chemical substances that cause acceleration of the degradation of insulating materials. Now they play a critical role in maintaining the functionality of the device.

Are tested not only new equipment, but also installations, which further undergo a process of accelerated thermal aging and radiation corresponding operating conditions over the expected life of the components, which are then subjected to a dose of emergency and emergency conditions (right at the end of life). The test procedure is based on the type of device (cable gland …), as well as the type and dosahovaného reactor power. Accordingly, depends on temperature, pressure, process crash dynamics and chemical composition of the primary coolant.

All these influences act on the primary circuit at the same time. When tested in laboratory conditions, however, the present action of the aforementioned degradation factors (radiation, temperature, pressure, chemical effects) is for safety and technical reasons. Therefore, the samples were first irradiated (irradiation grow old at the desired level), subjected to an elevated temperature. Now the device LOCA tests components on one of these effects, and exposure to the equipment under test thermodynamic shock associated with chemical exposure.

Gamma irradiation facility

Primarily, the device used to irradiate the components, materials and samples at normal and elevated temperatures for heat radiation and aging so as to simulate the conditions of operation of the nuclear power plants. One advantage of this device is the possibility to irradiate at cryogenic temperatures, high temperatures and irradiation of small samples in a vacuum apparatus with a vacuum or in an inert atmosphere at temperatures of -196 ° C to 400 ° C. The activity of cobalt emitters is 200 TBq. The facility also allows the radiation to modify the properties of non-metallic materials and to study the effect of gamma radiation on different systems, perform the sterilization of medical products and equipment, decontaminate different substances (spices, broth, etc.), treating objects from wood-destroying insects, stain glass, etc. ”


The device will be able to undergo the test specimens thermodynamic effects of high temperature, pressure and showering Kill solution in a pressure vessel made of stainless steel. Device will meet the experimental parameters – observe the prescribed thermodynamic profiles, especially a step change in temperature and pressure (see below), in pressure vessels, large-locate equipment to simulate the conditions the hydrogen explosion and post-LOCA. You will also be able to quickly auto-regulation of thermodynamic parameters (increase / decrease temperature / pressure).

Test items can be any objects whose dimensions do not exceed the internal dimensions of the test vessel (and possibly beyond, can be tested in a container at least the critical part), such as electrical cables, cable glands, cable joints and minor electrical switchgear, motors, seals, valves, sensors or other devices for which it is required to test resistance to the aforementioned accident. Typical test items as electric cables, which can be threaded through a through hole in the lid of the test the pressure vessel and during the test is to measure a power burden or their electrical properties.

The test facility allows for testing resistance test subjects not only against the effects of high temperatures and pressures, but especially against the effects of shock action (the so-called thermodynamic shock), and in the case of electric cables, cable connectors, cable glands, connectors, electric and some other components using directly demonstrate their functionality during the accident, it is possible to measure their electrical or other functional properties during the test.

After the accident LOCA simulation test subject is transferred to the pressure vessel post-LOCA, where will the corrosion test. It’s called post-LOCA test or a test for the flooding consisting of immersion – and in the case of cables and their voltage-current load – the shower solution of the specified temperature and pressure.
Part of the equipment also will be smaller chamber for simulation of severe accidents on the high parameters. Especially for simulating hydrogen explosion. Simulation explosion will take place by exposing the test item highly superheated steam, highly superheated air and nitrogen. During and after the test will demonstrate the functional properties of the test sample.

High voltage testing facility

High voltage test will be used to carry out tests in particular low-voltage electrical cables. In addition there is a particular source of AC to DC and 30 kV to 100 kV source. Tests will be carried out according to IEEE 383, NEMA WC-53 and IEC 60520-1. Operated types of tests are:

  • applying a DC voltage,
  • applying the alternating voltage,
  • Measurement of insulation resistance
  • measurement of active (ohmic) resistance cores.

In addition there will be a pool of water heating options for determining the resistivity and cable insulation resistance at higher temperatures.