Mochovce NPP Unit 3 reactor control assembly
Slovenské elektrárne (SE), an Enel Group company, completed the construction works of Mochovce NPP Unit 3 by finalising the control assembly of Mochovce NPP Unit 3 reactor. This a new important milestone in the commissioning of Unit 3 reactor which is now ready for primary circuit testing. Afterwards, the reactor will be prepared for the first hydrostatic test.
“We are very pleased to announce the successful completion of assembly of the internal elements of Unit 3’s reactor, which is the heart of a power plant,” said Nicola Cotugno, Chairman of the Board of Directors and General Director of Slovenské elektrárne. “This is one of the most important milestones achieved in the first half of this year, marking the completion of construction works of Unit 3 which now enters the testing phase. It also confirms our strong commitment to complete new Mochovce NPP units, with the third unit completion at more than 92.5%, and Unit 4 at 74.9 %.”
The aim of control assembly was to check the reactor vessel and the mutual mechanical relations of the reactor’s individual internal equipment. The operation also aimed at checking the assembly and disassembly operations of the reactor internal equipment in order to prepare it for individual testing.
Test on reactor’s functionality and assembly of the reactor required 22,000 man-hours and have been carried out in close cooperation with Škoda JS and its subsidiary Škoda Slovakia under strict so-called clean conditions in the Mochovce NPP Unit 3 reactor hall.
The next step will be the extensive testing and assembly works on the reactor and its internal equipment which is carried out in line with the programme for the reactor equipment’s commissioning and installation works. This programme will include:
- the so-called “cold” and “hot” hydrostatic test of reactor and primary circuit equipment connected with circulation flushing of the primary circuit equipment, check of leak-tightness and reading of hydraulic characteristics of the reactor and its internals.
- Inspections and checks of the reactor equipment after performance of hydrostatic tests at parameters close to the operating.
In this phase, activity of the reactor equipment will be tested in the non-active conditions, i.e. without nuclear fuel. Along with this programme, preparatory works for testing of emergency control rod assembly (ECRA) drives are performed.
The reactor’s internal equipments, which represent the technological heart of the nuclear power plant, are key structural components of the reactor together with the reactor pressure vessel. Their function is to direct the coolant flow in the reactor, position fuel assemblies and ECRA in the core and lead ECRA through the reactor core.
Emergency control rod assemblies are a standard component of reactors and they are independent systems which allow to change the balance of neutrons if needed, and interrupt or regulate the fission chain reaction through fast injection of absorbate into the core and taking a part of fuel out of the core. They also allow to maintain reactor power at a certain level or change it from a level to another, as well as compensating fast reactivity changes.The emergency control rod assembly motor-operated drives are situated in the upper plenum above the reactor, and they perform vertical or safety vertical movement of the emergency control rod assemblies.
Unit 3 of Mochovce NPP will contain 37 automatic ECRAs and 312 fuel assemblies in the tandem arrangement.