S. Suresh Kumar

Raman distributed sensor system for temperature monitoring and leak detection in sodium circuits of FBR

Leak detection in coolant loops of nuclear reactors is critical for the safety and performance of the reactors. The feasibility of using Raman distributed temperature sensor (RDTS) has been studied on a 30m test loop. Temperature in sodium circuits of fast Breeder Reactor (FBR) exceeds 550°C, gold coated fiber is chosen as sensor fibers. Leak is simulated through an artificial micro fissure integrated in the test loop with provision for controlled leak rate. The results are discussed in the paper.

Avascular Necrosis of Femoral Head as the Initial Manifestation of CML

Summary: A 12-year-old female is reported who presented with right hip pain for 6 months. With massive splenohepatomegaly and leukocytosis, CML was suspected and confirmed on bone-marrow examination and cytogenetics. Further investigations confirmed avascular necrosis (AVN) of the right femoral head. CML was treated by hydroxyurea, followed by imatinib. AVN was managed conservatively; patient demonstrated progressive improvement, though a mild limp in the gait was persisting at 22 months. AVN as the initial manifestation of CML is a rarity. Leukostasis is considered to be the pathophysiological mechanism. In view of the rarity, a case is reported, along with compilation of previously reported cases.

Testing and Qualification of Diverse Safety Rod and Its Drive Mechanism for PFBR

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.Copyright

Experimental Qualification of Mechanical and Electrical Sub-systems of a Complex Mechanism Against Fatigue Failure

Absorber rod drive mechanisms (ARDM) play an important role in ensuring safety of a reactor by rapid insertion of an absorber rod during abnormal conditions. Various components/sub-systems of ARDMs, both mechanical and electrical, are subjected to different cyclic loadings during service life. Thus, qualifying these systems against fatigue is an important step for gaining confidence in their safe operation for the design life. ASME in Sec. III, Div. 1, Appendices (Para II—1500) provides guidelines for the experimental evaluation of the capability of components to withstand cyclic loading. These rules are developed for static components like pressure vessels. Since no such rules are available for moving components like mechanisms, the same were adopted for the ARDMs, with an understanding that the effect of inertia loads of a moving component are to be accounted in the experiments. In application of these rules to a complex mechanisms such as ARDM, various special cases arise which are not addressed explicitly in the code. The paper describes the intelligent adoption of the fatigue life rules given in ASME to various special cases and their extension to electrical systems. The paper also outlines the experiments carried out for qualifying the ARDM against fatigue.