The KLT-40S nuclear installation incorporates the following passive safety systems:

—System of reactor shutdown with insertion of control rods into the core under the force of springs (scram rods) or gravity (shim control rods), when holdup electromagnets from the control rod drives are de­energized;

—Passive system of emergency reactor cooldown through the steam generator;

—System of emergency water supply from the ECCS hydro-accumulators;

—Containment and stop valves, normally in a closed position, located at the auxiliary systems of the primary circuit and adjacent systems;

—Passive system of external cooldown of the reactor vessel;

—Self-actuated devices for startup of the safety systems;

—Emergency containment cooling system;

—Protective enclosure.

Passive safety systems operate with natural circulation of the coolant or use the energy of a compressed gas.

9-

ACTIVE EHRS;

10- PASSIVE EHRS;

11- CONTAINMENT BUBBLING SYSTEM;

12- REACTOR

ECCS — emergency core cooling system RVCS — reactor vessel cooling system
EHRS — emergency heat removal system

FIG. I-3. Safety systems of KLT-40S.

The emergency heat removal system (EHRS) is intended to remove residual heat from the reactor in beyond design basis accidents involving NPP blackout and failure of active channels. The system includes two channels, consisting of two heat exchange loops each. The capacity of a single EHRS loop (~1% of nominal reactor power) is sufficient to ensure reliable reactor cooldown and to maintain reactor pressure within design limits.

Residual heat is removed by natural convection of coolant in the primary and intermediate circuits and by the evaporation of water from the tank where heat exchanger-condensers (HXC) are located. Water reserve in EHRS tanks ensures heat removal from the reactor over 24 hours.

The prototypes of a passive EHRS are cooling systems used in propulsion reactors. The effectiveness of such systems has been confirmed both by experiments at test facilities and by tests at operating plants.

The majority of KLT-40S safety systems employ a two channel scheme with internal reservation of active elements such as valves and pumps. Using a two channel scheme for safety systems within the specific conditions of a floating structure (where it is necessary to save on space and equipment weight compared to land based NPPs) allows for a reduction in the amount of bulky equipment required, such as tanks and heat exchangers.

Elements of both active and passive safety systems belong to the second safety class, according to the top level Russian regulation OPB-88/97.

The requirements for manufacturing technologies of devices and equipment for active and passive safety systems correspond to regulatory requirements in the nuclear energy area.

For floating NPPs, specific regulations have been developed and adopted in the Russian Federation, in particular, “The rules of arrangement and safe operation of the equipment and items for light water reactors of the floating nuclear power plants (NP-062-05)”.