G. Padmakumar

Numerical Analysis of Thermal Striping Phenomena Using a Two Jet Water Model

Abstract A numerical analysis simulating the thermal striping phenomena in a 1/5 scale water model of Prototype Fast Breeder Reactor (PFBR) primary circuit is carried out. Two non-isothermal water jets are impinged on a lattice plate placed above the jets. Reynolds stress turbulence model is used to evaluate the temperature fluctuations near the plate. The jets with unity velocity ratio showed maximum temperature fluctuations. The cold jet dominated and hot jet dominated flows result in very high and low temperature fluctuations respectively. This paper presents the computational techniques adopted to simulate the non-isothermal jet mixing phenomena, the results obtained thereby and discussion of these results.

Investigation of Thermal Striping in Prototype Fast Breeder Reactor Using Ten-Jet Water Model

A two-dimensional numerical analysis has been carried out to study the phenomenon of thermal striping in a prototype fast breeder reactor using a 10-jet water model that represents a row of the reactor core consisting of fuel and blanket zones. The above-core structures in the reactor are modeled with a porous lattice plate and solid core cover plate. The Reynolds stress model is used for simulating the turbulence characteristics of jet mixing phenomena. When the ratio of hot jet velocity to cold jet velocity is equal to 1, maximum fluctuations of temperature have been observed. Also the temperature fluctuations reduced gradually beyond a hot jet to cold jet velocity ratio of 1.0. The lattice plate is found to be more prone to thermal striping as compared to the core cover plate.

Numerical Simulation and Experimental Validation of Future FBR Surge Tank Hydraulics

Surge tank is provided in the secondary sodium circuit of Sodium cooled Fast Reactors (SFR) to protect the secondary sodium circuit components from the pressure surges due to sodium water reaction in Steam Generator (SG). The pressurized argon gas inside the surge tank above sodium will act as a cushion and absorb the pressure surges. The entrainment of argon gas into the sodium due to free level fluctuations, turbulence etc. can cause operational difficulties in reactor. It is necessary to develop effective gas entrainment mitigating devices which keeps the sodium free surface calm but the development only through experiments is difficult and time consuming. Therefore a CFD model of surge tank is developed to predict the surge tank hydraulics and it is validated through experiments. Velocity measurement in the model at different directions and different elevations has been carried out using Ultrasonic Velocity Profiler (UVP).

Active magnetic bearings for sodium pump

Centrifugal Pumps are used in the primary and secondary heat transport systems of fast reactors for pumping liquid sodium. Lubrication oil leakage from the conventional bearings used in these pumps is a potential threat to cause reactivity changes which could result in extended reactor shut down. Actively controlled magnetic bearings which do not require lubrication is an excellent alternative to conventional bearings in overcoming these problems. The present work deals with the development of “Thrust and Radial Active” magnetic bearings for a small centrifugal sodium pump of 50 m3/h capacity, which controls both the axial and radial movements of rotor. The developed active magnetic bearing takes a thrust load of around 100kg, and a nominal radial load for the existing vertically-configured shaft system of the centrifugal pump. Performance of the active magnetic bearings has been tested successfully by running the pump up to the full operating speed of 2900 rpm and the measured vibration levels were well within the allowable limits of ISO 14839.