FIR-NSS: Fission Reactors / Nuclear Safety and Safeguarding

Brief Description of Technology
The purpose of this work is the development of automatic passive protection devices (APPD), i.e., self-actuating hydromechanical devices activated by a direct pulse of non-allowable change reactor plant (RP) working medium parameters without the intervention of operating personnel or the use of special energy sources.

APPD are intended both to execute specific functions of assuring safety by imparting to them the functions of an actuator (first group of devices) and to control safety systems’ actuators, for example, CPS mechanisms and pneumatically and electrically driven valves (second group of devices).

Automatic Protection Device (APD)

Automatic protection device (APD) belongs to the first group of devices. APD is intended to protect against overpressurization of an isolatable RP secondary circuit section.

APD design completely corresponds to the concept of protection of an isolatable RP secondary-circuit section that is accepted in OKBM and based on the use for protection of pressure compensation means, which is provided for a primary circuit system.

To assure this concept, the APD when actuating communicates with the system to be protected with a primary circuit cavity.

The APD operation principle resides in the destruction in the weakened section of an sealing element separating a cavity of the system to be protected and a discharge cavity when the pressure of working medium in the cavity of the system to be protected becomes higher than that allowed.

The force necessary to destroy the sealing element is created as a result of a pressure medium of the system to be protected acting on a bellows drive, whereby passive APD actuation is assured.

Under an emergency buildup of pressure in the system to be protected to a value specified by the strength conditions of the system, APD actuation proceeds with rupture of the sealing element in its weakened cross section without the formation of fragments or shavings. As a result, the excess pressure coming through the formed opening is discharged from the system to be protected into the discharge cavity, thus preventing its overpressurization.

Until APD activation, it assures the guaranteed hermeticity of the system to be protected respective to the discharge cavity (the primary circuit in this case) by a solid wall of the sealing element.

Hydroactuated Pneumatic Distributor

Hydroactuated pneumatic distributor (HPD) belongs to second group of APPDs.

HPD is intended for automatic activation of the RP safety system at a non-allowable buildup of primary circuit pressure in emergencies by activation of a safety system’s pneumatically driven isolation valves, for example, emergency cooling system (ECS).

HPD actuation at non-allowable buildup of primary circuit pressure leads to a redistribution of supply and discharge of compressed air in the valves' control pneumatic system and, as a result, to activation of the safety system isolation valves.

The NPD activation process occurs automatically, without the intervention of operating personnel, due to the energy of the working medium.

Thereby, HPD design assures:
- discharge (supply) of compressed air from the isolation valves' pneumatic drives;
- blocking after HPD actuation of a safety system’s pneumatically driven valves standard control system using electromagnetic pneumatic distributors;
- possibility to bring the HPD to working condition after activation (preparation for the next activation) after lowering the pressure in the system to a specified value.

Structurally, the HPD is build on the basis of using the pulse device APD, including a sensing element responding to working medium pressure and a mechanism for adjusting for the actuation pressure.

In this connection, the APD possibilities described above are completely those of HPD.

Legal Aspects
RF Patents have been issued for a number of solutions realized in APPD.

Special Facilities in Use and Their Specifications
There are no analogues of the devices under consideration having operating age as a part of RPs.

Scientific Papers
The information about APPD was presented as the report "Self-Actuating NPP Safety System Devices" at the "Nuclear Energy and Human Safety" International Conference of the Nuclear Society in Nizhny Novgorod, July 1993.

Дата добавления: 2015-07-20