The prime requirement of reactor safety combined with the need for high availability of nuclear plants have, in recent years, led to considerable research and development efforts at the Bhabha Atomic Research Centre in the field of reactor safety and control engineering. The areas of special interest have been the development of a fast acting emergency shutdown system, on-line fault detection facility for the reactor protection circuits, enhanced instrumentation capability for measurement of critical plant parameters and computerised systems for plant protection, control, performance evaluation, disturbance analysis, and data acquisition and display with particular attention to the problem of manmachine interface. Some of these recent concepts have been incorporated in safety and control systems of theDhruva reactor which is at present undergoing commissioning trials at Trombay. The special features of these systems are highlighted in the paper. The safety strategy adopted for the reactor and the consequent development of special safety systems are described in detail. The choice of the reactor control scheme and the methodology followed in the design of the automatic power control system are indicated. Campbell instrumentation for measurement of neutron flux or in other words reactor power, extensive use of microprocessors in safety related instrumentation and an improved man-machine interface through suitable design of control room have helped in achieving a high degree of reactor safety. The salient features of these systems are also included.

Following a sequential two-photon excitation, fluorescence is observed from several selectively excited single rotational-vibrational energy levels of theE³π0_g⁺ state of molecular iodine. The re-emittedE →B fluorescence spectrum from each of the populated rovibrational level of theE state consists of a series of sharp lines terminating on the various discrete ro-vibrational levels of theB state and a few broad lines due to transitions taking place on to the continuum of theB state. The point of transition from sharp lines to broad features in the fluorescence spectrum has been utilized to determine theB state dissociation limit. This method of obtaining the dissociation limit of the molecular electronic states appears to be quite simple and straightforward.