Progression Of Upgrades in I&C of Indian Research Reactors

The Instrumentation & Control (I&C) Systems of Nuclear Research Reactors has evolved over the years. Right from Pneumatic instruments to Modern Digital I&C, it has passed through different phases. Though during design and construction of Reactor the I&C systems relevant safety standards of that time was adopted but current safety standards are to be fulfilled by the operating reactors. Due to obsolescence of C&I systems, C&I upgrade needs to be initiated. Upgraded C&I systems also provide better self-diagnostics, operator interface, enhanced safety & reliability. Research Reactor Dhruva, which was designed in late seventies & is operating safely since commissioning. The I&C systems were facing not only obsolescence but also having limited testability & diagnostic features. Regulatory requirements of current safety standards were also difficult to fulfil. The major Safety Class IA & IB Instrumentation and Control systems of Dhruva are upgraded to modern Digital I&C systems. The upgrades were taken in a phased manner to minimize the downtime of the reactor. The Pneumatic instruments were replaced by Digital Electronic Instruments. The Differential Pressure gauges of Channel Flow Monitoring System were replaced by Indigenously developed Digital instruments, fulfilling the regulatory requirements of current standard. The major I&C systems such as Reactor Trip Logic System, Start-up Logic System and Alarm Annunciation System etc. are replaced by an in-house developed Programmable Logic Controller (PLC). The systems were designed & developed using qualified configurable platform. Additional diagnostic features, better operator interface and security features were incorporated in the system. Verification & Validation (V&V) of the individual systems were carried out as per requirements of present standards. The Radiation Monitoring System, Fire Alarm System, Reactor Regulating System were also upgraded with Digital I&C with better operator interface, additional information & features and redundancy. This paper covers upgrade of different I&C Systems of Dhruva Reactor. (author)