Preparation of a project for commissioning of an additional emergency feedwater system

Project: „Feasibility study and preparation of a project for commissioning of an additional emergency feedwater system for steam generators and BOD cooling of 5 and 6 units using the equipment installed in EP-1”
Client: „NPP – Kozloduy“
Contract: № 232000001/08.01.2013 г.
Execution: 03.2013÷03.2014

The conceptual design has been developed in accordance with the requirements of the regulatory framework of the Republic of Bulgaria regarding the provision of heat removal from the reactor core under all emergency conditions, incl. in the case of extra-design and severe accidents, art. 74 of the Regulation for ensuring the safety of nuclear power plants.

In order to optimize the costs for the construction and commissioning of DSLPs for Units 5 and 6 (DSLS-5 and 6), it is envisaged to make maximum use of the available (and applicable) equipment of the existing DSLP system in the development of conceptual solutions blocks 3 and 4 (DSAPP-3 and 4).

The basis for the development of the project of the system is the need to ensure the cooling of the core and the BOD in an event that leads to the loss of own power supply and the failure of the three regular emergency diesel generators of Unit 5 and / or Unit 6 of Kozloduy NPP “.

An accident with the complete loss of all AC power sources of the units causes the steam generators to be disconnected, which deteriorates and subsequently terminates the heat transfer from the first to the second circuit. As a result, the parameters in the first circuit increase, the safety valve of the CN opens and the coolant from the first circuit begins to flow to the bubbling tank and then to the containment zone. Due to the lack of opportunity to feed the first circuit, the event leads to a severe accident occurring at high pressure in the first circuit.

In the event of such an accident, it is necessary to ensure that the BOC is cooled down and energized (in case of leaks).

In order to prevent such a scenario, it is necessary to stop the loss of the coolant from the first circuit through the MC CN and to allow the heat to be removed through the second circuit.

The DSAP system provides additional power supply to the GHG and the BOC with a power source that is independent of the unit’s power supply system and with equipment that can operate regardless of the condition of the unit.

The DSAP system is designed to be independent of water and electricity supply