PRA-0060

Full Title Automatic Passive Protection Devices for Nuclear Reactors Tech Area / Field

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.

Rotor Dynamic Calculation Procedures for Electromagnetic and Auxiliary Bearings pra-0061

Full Title Development and Verification of Rotor Dynamic Calculation Procedures for Electromagnetic and Auxiliary Bearings Using IPM Test Rigs Tech Area / Field

FIR-REA: Fission Reactors / Reactor Concept

MAN-TRI: Manufacturing Technology / Tribology

Brief Description of Technology Investigations of rotor dynamics in electromagnetic or catcher bearings are performed by many foreign firms: General Atomics (USA), Framatome (France), Thermodyn (France), and IPM (Germany).

The majority of the materials published do not contain a sufficient data base (initial data and test results) required to verify the calculation results. With regards to the catcher bearings, frequently only a number of successful "landings" is recorded without giving information on perturbing forces and shaft coordinates.

The difference of the newly developed procedure resides in the fact that during its development the following factors are supposed to be taken into account: - tangential forces influencing the rotor stability; - complex tribological characteristics of materials; - rotor flexibility; - influence of damping characteristics of a bearing; - availability of movable element between a rotor and stator.

The development and verification of this procedure will allow: - the specification of the description of a control object, which will be used at the choice of EMB control laws; - the determination of possible mechanisms of buildup of forces acting on catcher bearings during the shaft "landing"; - the facilitation of the justification of catcher bearing design choice.

Legal Aspects No patents have been issued.

Special Facilities in Use and Their Specifications For verification of the procedure, a special FLP-500 test rig from IPM (Zittau, Germany) is available for testing the rotor with electromagnetic and catcher bearings. Its technical data are as follows:

Test bearing diameters (max) 300 mm

Speed (max) 7200 mm

Loads: Pressure 300 kN Tensile 100 kN Moment of Torsion 4000 Nm

Kind of Loads axial + radial

Pressure 0–3 bar

Temperature 333 K (393 K)

Medium He, N₂, air, vacuum

Engine Power, Pmax 300 kW

Shaft Mass 1320 kg

Testbox dimensions: Diameter 1 m Height 3 m

Scientific Papers “Dynamic Behavior of Flexible Rotors with Active Magnetic Bearings on Safety Auxilary Bearings,” A.Gelin, J.Der Hagopian, I.M.Pugnet, Proceeding of III Working Conference on Magnetic Bearings, Zittau, Germany, September 1996.

“Active Magnetic Bearings for Rotating Machinery in Future Gas-cooled Reactor Plants,” J. Alastair Rennie, Colin F. McDonald, Proceeding of IV International Symposium on Magnetic Bearings, Zurich, August 1994.

Materials of II and III International Working Seminars on Magnetic Bearings, Zittau, Germany, 1995 and 1996.

Leaktight Step Motor Development pra-0062

Full Title Leaktight Step Motor Development Tech Area / Field

FIR-INS: Fission Reactors / Nuclear Instrumentation

MAN-MCH: Manufacturing Technology / Machinery and Tools

Brief Description of Technology The purpose is the development of a parametric range of step motors — leaktight electric machines with low speed and high torque that perform discrete conversion of electric energy.

The urgency of the development is determined by conceptual safety requirements for various plants, including reactor biotechnology and chemistry plants where leaktight mechanisms with electric drives are used for operation in vacuum or under pressure of different media.

Step motors provide various operational modes for the mechanisms: - control rod drive mechanism (CRDM) movement with different velocities and for a specified value; - CRDM holding in a predetermined position given the loads affecting the CRDM; - stopping CRDM movement in a given mode at a corresponding signal; - retardation, i.e., motion of CRDM with a constant velocity that tends to accelerate under the effect of certain forces.

OKBM leaktight step motors: - are indispensable as electric drives for leaktight mechanisms functioning in a vacuum or under media pressure; - do not require shaft sealing; - exclude leaks to the environment; - meet the strictest safety requirements; - do not require immediate maintenance during operation; - provide high reliability, lifetime, and safety.

OKBM production and testing base allow the creation of prototypes, individual sets and small series of leaktight step motors of different purposes. The project supervisor is F. M. Mitenkov, Academician of the RAS.

Legal Aspects There is some patented knowledge in Russia for a leaktight step motor.

Special Facilities in Use and Their Specifications The reliability of OKBM leaktight step motors has been verified by the successful operation of ice-breaker nuclear power plants over 20 years with an operating age of more than 100,000 his.

Scientific Papers None.