PFBR, India’s first commercial fast breeder reactor employing fast fission is a challenging project from technological point of view to meet the energy security of the country. It is currently under advanced stage of construction at Kalpakkam, India. PFBR is equipped with two independent, fast acting and diverse shutdown systems. A shutdown system comprises of sensors, logic circuits, drive mechanisms and neutron absorbing rods. The absorber rods of the second shutdown system of PFBR are called as Diverse Safety rods (DSR) and their drive mechanisms are called as Diverse Safety Rod Drive Mechanisms (DSRDM). DSR are normally parked above active core by DSRDM. On receiving scram signal, Electromagnet of DSRDM is de-energised and it facilitates fast shutdown of the reactor by dropping the DSR in to the active core. For the prototype development of DSR and DSRDM, three phases of testing namely individual component testing, integrated functional testing in room temperature and endurance testing at high temperature sodium were planned and are being done. The electromagnet of DSRDM operates at high temperature sodium environment continuously. It has been separately tested at room temperature, in furnace and in sodium. Specimens simulating the contact conditions between Electromagnet and armature of DSR have been tested to rule out self welding possibility. The Dashpot provided to decelerate the DSR at the end of its free fall has been initially tested in water and then in sodium. The prototype of DSR has been tested in flowing water to determine the pressure drop and drop time. The functional testing of the integrated prototype DSRDM and DSR in aligned and misaligned conditions in air/water has been completed. The performance testing of the integrated system in sodium has been done in three campaigns. Based on the performance testing in the first two campaigns of sodium testing, design modifications and manufacturing quality improvement were done. Methods of drop time measurement based on ultrasonics and acoustics were also developed along with the first two campaigns. During the third campaign of sodium testing, the performance of the system has been verified with 30 mm misalignment at various temperatures. The third campaign has qualified the system for 10 years of operation in reactor. This paper describes the test setup for all the above mentioned testing and also gives typical test results.
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.
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