Safety Rods Drive Mechanisms for Fast Sodium-Cooled Reactors pra-0063

Full Title Development of Control and Safety Rods Drive Mechanisms for Fast Sodium-Cooled Nuclear Reactors Tech Area / Field

FIR-REA: Fission Reactors / Reactor Concept

Brief Description of Technology The goal of the project is to develop control and safety rod drive mechanisms (CSRDMs) for fast sodium-cooled nuclear reactors that are capable of providing enhanced reliability and safety for nuclear plants, easy operation, and extended service life.

The development is realistic due to the following reasons. All the programs for further development of nuclear power that take into account a nuclear fuel resources factor are based on the nuclear fuel production potential of fast-breeder reactors. Significant experience in construction and operation of this type of nuclear reactors has been accumulated in Russia and worldwide.

The direct dependence between reactor-related equipment reliability and reactor safety defines the exceptional attention which is devoted to equipment design validation and development during the design process and functional testing. At present, more attention is being given to simplification of CSRDM design and improvement of their mounting convenience, maintainability, and nuclear safety-related operation control in order to enhance CSRDM reliability and increase the economic efficiency of NPP operation through reducing their refueling outage duration. This conclusion can be drawn from the analysis of CSRDM designs BN-350 and BN-600 used for fast nuclear reactors.

Taking into account the complexity of maintaining electrical equipment pertaining to drive mechanisms located within a reactor, the design under development provides the arrangement of drive motors beyond a reactors primary circuit boundaries.

It is expedient to apply stepping motors, which, being low speed motors, allow the minimization of a reducers gear ratio at the given velocity of a control member and consequently the simplification of a reducers kinematic train, thus improving the reliability of the actuator.

In the design under development, verification of CSRMs fulfillment of control member coupling-uncoupling operations is provided without the mechanisms drive shaft being withdrawn to the upper working position. This reduces the reactor outage time and enhances safety during the indicated operations.

The project supervisor is F. M. Mitenkov, Academician of the RAS.

Legal Aspects There are patents of the Russian Federation for a number of technical solutions used in the design.

Special Facilities in Use and Their Specifications The enterprise OKBM possesses more than 30 years of experience in designing and making control rod drive mechanisms for BN-350 and BN-600 fast sodium-cooled nuclear reactors, which have been operating successfully.

Scientific Papers On the basis of experience gained by OKBM in the development of control rod drive mechanisms, the book “Control and Safety Rod Actuators for Fast Sodium-cooled Nuclear Reactors(in Russian)” was published (edited by Dr. F.M. Mitenkov, Energoatomizdat Publishing House, Moscow, 1980).