Design & development of soft-core processor based remote terminal units for nuclear reactors

Remote Terminal Units (RTUs) are single board, real time remote data acquisition & control systems that are used in Fast Breeder Reactors to acquire analog/digital signals [like voltage, signal inputs from surface thermocouple, leak detector & limit switches], sends digitized data packets over Ethernet to the nearest Local Control Centre (LCC) and generate control outputs in the form of potential free contacts during all states of the reactor operation. The design implementation concepts of soft-core processor based RTUs where TSK51 (a processor IP core from Altium) is used in place of conventional microcontroller along with other glue logic coded in VHDL thereby implementing complete digital logic of the embedded system in a FPGA is being discussed in this paper. This has enabled to overcome the problem of obsolescence of components along with the added advantage of improved reliability and reduced power consumption, which is proven in the last part of the paper. This paper also demonstrates the use of Altium designer software and Altium Nanoboard [Development Kit], which is used in the entire development process, starting from IP cores based development on FPGAs, embedded software development for the IP cores and overall PCB designing.

I. Introduction

Sodium is used as a coolant in Fast Breeder Reactors for extracting heat generated from the reactor core[l] and is highly inflammable when comes in direct contact with air hence requiring continuous surveillance for leak detection, level measurement, temperature control, flow control and pressure control. Remote Terminal Units (RTUs) are single board, real time remote data acquisition & control systems that are used in safety related and Non-Nuclear Safety I&C systems of Fast Breeder Reactors, to acquire various analog/digital signals [like voltage, signal inputs from surface thermocouple, leak detector & limit switches] and send digitized data packets over Ethernet to the nearest Local Control Centre (LCC) and generate control outputs in the form of potential free contacts during all states of the reactor operation [2]. This system help in reducing cabling from large number of surface thermocouples attached with sodium pipelines & leak detectors in FBRs and are designed to operate in extreme field conditions in various reactor buildings.