Mochovce approaching the finish line, entering the last testing phase before fuel loading
Slovenské elektrárne completed all works on the hot hydrotest and started the major inspection, which is the last phase of non-active tests before the commissioning of unit 3 at the Mochovce nuclear power plant. During this inspection, the biggest power generating company in Slovakia will carry out the prescribed pre-operational inspections of all important systems and equipment. The major inspection is a prerequisite for initiating the physical and energy start-up.
After the hot hydrotest, the company successfully performed also an integrated test of the strength and tightness of the Unit 3 hermetic zone. It is one of the most important tests in the preparation for commissioning during which the hermetic zone was pressurised to 150 kilopascals (the underwater pressure in 15 metre depth) and the strength of the walls and ceilings at the limit of the hermetic zone was measured, as well as its resistance to leakages. The hermetic zone consists of reinforced concrete structure of the primary circuit building with 1.5 metre thick walls.
The hot hydrotest had five sub-stages that included the pressure and tightness tests on the primary circuit and reactor at nominal operating parameters, at temperature of 265°C and pressure from 0.5 to 19.12 megapascals (MPa), e.g. one and a half times the pressure reached in an operating unit. Slovenské elektrárne also carried out functional tests of the primary and secondary circuit equipment, tests of safety systems, ventilation, electrical components, control and management systems, as well as other systems. The company also examined systems and measures resulting from stress tests, and compared all the data obtained with data in the design and related equipment documentation.
Slovenské elektrárne fulfilled the hot hydrotest in full scope. It did all the defined tests and passed successfully. Slovak Nuclear Regulatory Authority (NRA) monitored the whole course of the hot hydrotest. The NRA noted the preliminary evaluation of the hot hydrotest and will issue its final opinion after assessing the required analyses and in the concluding evaluation of the test programme verified by the scientific management of commissioning. The hot hydrotest lasted a month and a half longer than scheduled, mainly due to an unplanned false activation of the fire extinguishing system.
The later than planned completion of hot hydrotest and the delay in the construction works resulted in the need to re-schedule the commissioning. Several works proved to be substantially more time-consuming, and on top of that in April 2018 cooperation with the building company was terminated. Slovenské elektrárne expects that unit three will be technically prepared for fuel loading during the course of summer 2019.
Before the Nuclear Regulatory Authority issues the relevant licences, other state administration authorities, such as the Public Health Authority, the Labour Inspectorate, and the Firefighting & Rescue Corps, will also have to issue opinions, which is a time-demanding process. The exact date of commissioning will depend on the licensing process, the proceeding of which will be significantly affected by the anticipated obstructions of involved parties, in particular Austrian anti-nuclear organisations. As much as 8 months may pass from the time of technical readiness for fuel loading up to the actual date of fuel loading.
The delay will also impact the total budget for the completion of Units 3 and 4, in an estimated cost of €270 million, representing a 5% increase in total costs. This budget increase will be fully covered by the majority shareholder of Slovenské elektrárne, namely Slovak Power Holding B.V.
More than 3,500 employees and contractors work on site, of whom two thirds on unit 3 and the remainder on unit 4. Unit 3 is completed at 98.8% and unit 4 at 84.6%.
- The hermetic space system (also termed “containment”) is a complex of parts that either individually or in conjunction, enable safety functions to be fulfilled.
- The hermetic zone is divided into an outer and an inner part:
The outer hermetic boundary is formed by reinforced concrete walls lined with steel sheeting, which separate all hermetic spaces from the surroundings.
The inner hermetic boundary is formed by a similar construction as the outer boundary, and these have the main hermetic spaces from adjacent hermetic spaces, semi-service spaces and hermetic seals.