Design and Qualification of Control and Safety Rod and Its Drive Mechanism of Fast Breeder Reactor

Abstract

Prototype Fast Breeder Reactor (PFBR) has two shutdown systems. The absorber rod of the first system is called Control & Safety Rod (CSR). Control & Safety Rod Drive Mechanism (CSRDM) facilitates start-up & controlled shut-down of reactor and control of reactor power by raising and lowering of CSR and shutdown of the reactor on abnormal conditions by rapid insertion of CSR into the core, i.e., by scram action. After the detailed design and analysis of CSR and CSRDM, they were qualified in two stages. In the first stage, the critical assemblies of the mechanism, such as scram release electromagnet, hydraulic dashpot and dynamic seals, were tested individually simulating the operating conditions of the reactor and the design parameters were fine-tuned. Experiments were also carried out on sodium vapour deposition in the annular gaps between the stationary and mobile parts. In the second stage, prototype CSRDM and CSR were manufactured and subjected to various functional tests in air, in hot argon and subsequently in sodium simulating the operating conditions of the reactor. Tests were carried out keeping CSRDM and CSR at aligned condition and with the possible misalignment between them. The performance was checked and recorded maintaining the temperature of sodium starting from 473 K to 823 K. Then the system was subjected to endurance tests. The results show that the performance of CSRDM and CSR is satisfactory and there is no significant change in the performance during endurance testing.