Familiarization with instrumentation used for reactor core temperature
By :Chandra Mohan Sharma
Contents Company Profile Introduction Integrated Development Environment (IDE) Real Time Operating System(RTOS) CPU Board (RT-20) RTD Input Module (RIM) Resistance Temperature Detector(RTD) Conclusion
Company Profile -NPCIL Nuclear Power Corporation of India Limited is a Public Sector Enterprise under the administrative control of the Department of Atomic Energy (DAE), Government of India, established in 1987. NPCIL is responsible for design, construction, commissioning and operation of nuclear power reactors. NPCIL is presently operating 20 nuclear power reactors with an installed capacity of 4780 MW. The Mission of the Company is ‘To develop nuclear power technology and to produce nuclear power as a safe, environmentally benign and economically viable source of electrical energy to meet the increasing electricity needs of the country. The operating nuclear power units are: Tarapur Atomic Power Station Units-1,2,3&4. Madras Atomic Power Station Units-1&2. Rajasthan Atomic Power Station Units-1 to 6. Narora Atomic Power Station Units-1&2. Kakrapar Atomic Station Units-1&2. Kaiga Generating Station Units-1 to 4.
Introduction To CTMS CTMS :- Channel Temperature Monitoring System. CTMS as the name suggests, is a system to monitor the temperature of the channels or hard-water pipes used in the reactor core which carry the heat produced due to the fission reaction inside the core. These pipes carry the hot D2O to the steam generator. There are RTD’s at the outlet of the each channel which detects the out temperature. This system uses dual RTD’s so that the data from the field is continuously available in case one RTD fails. RTD Fuel Channel D2O Pipe Steam Generator Fuel Channel D2O Pipe Fuel Channel D2O Pipe Fuel Channel D2O Pipe Fuel Channel
Above given diagram is the block diagram of the Test Setup for the Channel Temperature Monitoring System (CTMS). The data from the field is acquired by the RTD Input Module (RIM) board and then it is sent to the RT20 board for processing and this board is connected to a Cathode Ray Tube (CRT) Monitor which shows the result of the processing done by RT20 board on the data acquired from the field. CRT is connected to the RT20 board on connector P4 by a serial connection cable. RIM uses the I/O bus to transfer the data to the processor for processing. The Input Output Interface Module (IOIM) and Versa Euro Module (VME) are both types of interfacing modules that are used to interface different boards to each other.
CTM Resource RequirementsThe basic requirements for the design and development of CTM System are asfollows: Tornado Integrated Development Environment (IDE) Real Time Operating System (RTOS) Serial Connection Cables CPU Board (RT-20 Board) RTD Input Module Boards (RIM) ROM (Relay Output Module) IOIM (Input Output Interface Module) GBINC Board Resistance Temperature Detectors (RTDs)
Tornado IDE The Integrated Environment is used for software cross development. It is an efficient way to develop real time and embedded applications with minimal intrusion on the target system. Here we use “Tornado 2.2” which is an IDE developed by Wind River Systems, Inc. and consists of VxWorks, a high performance real time OS, application building tools (compilers and associated programs), IDE i.e. C and C++ compilers and makefiles etc. Cross development environment ensures the smallest possible differences between the target system during development and the system after development.
Key features of the IDE are: An integrated source-code editor. A project management facility. Integrated C and C++ compilers and make. The browser, a collection of visualization aids to monitor the target system. CrossWind, a graphically enhanced source-level debugger. WindSh, a C-language command shell that controls the target. An integrated version of the VxWorks target simulator, VxSim. An integrated version of the WindView software logic analyzer for the target simulator. Customization options for many features, including integration of alternate editors and configuration management (CM) tools, as well as the entire Tornado GUI itself.
Building Projects in TornadoThere are two types of applications that can be created using tornado. Downloadable Application: A downloadable application consists of one or more relocateable objects modules, which can be downloaded and dynamically linked to VxWorks, and then started from the shell or debugger. Bootable Application: It consists of an application linked to a VxWorks image. It starts when target is booted.To create a downloadable application, you must: Create a project for a downloadable application. Write your application, or use an existing one. Add the application files to the project. Build the project.You can then download the object module(s) to the target system and run theapplication.
A bootable application is completely initialized and functional after a target hasbeen booted, without requiring interaction with Tornado development tools.A bootable application can be created as follows: Add the application project(s) to the VxWorks workspace (or vice versa). Edit the VxWorks initialization file usrAppInit.c, adding calls to the applications initialization and startup routines. Use the project facility to help scale VxWorks. Build the bootable application.
VxWorks (RTOS) Modern real-time systems are based on the complementary concepts of multitasking and intertask communications. A multitasking environment allows a real-time application to be constructed as a set of independent tasks, each with its own thread of execution and set of system resources. The intertask communication facilities allow these tasks to synchronize and communicate in order to coordinate their activity. Another key facility in real-time systems is hardware interrupt handling, because interrupts are the usual mechanism to inform a system of external events. To get the fastest possible response to interrupts, interrupt service routines (ISRs) in VxWorks run in a special context of their own, outside any tasks context. Multitasking provides the fundamental mechanism for an application to control and react to multiple, discrete real-world events. The VxWorks real- time kernel, wind, provides the basic multitasking environment. Multitasking creates the appearance of many threads of execution running concurrently when, in fact, the kernel interleaves their execution on the basis of a scheduling algorithm . VxWorks uses Round Robin Scheduling Algorithm. On a context switch, a tasks context is saved in the task control block (TCB).
Task State Transitions:Task Scheduler Control Routines CALL DESCRIPTION kernelTimeSlice() Controls round-robin scheduling. taskPrioritySet( ) Changes the priority of a task. taskLock( ) Disables task rescheduling. taskUnlock( ) Enables task rescheduling.
CPU Board (RT-20) This is the main module where microprocessor resides and it is identified as RT-20. It is a VME Bus based CPU Board and uses Motorola MC68020, a 32-bit microprocessor at 16 MHz Clock speed. The Board has provision for 512 KB of EPROM (256 KB used only) and dual ported high speed 512 KB of battery backed SRAM. The board has provision for MC68882 Floating Point Numeric Coprocessor. It has Dual Asynchronous Receiver Transmitter (DUART). VME Bus interface is provided using VIC068A.
Decode & Control Local Memory EPROM On Board IO SIO PIO Logic SRAM RTC DISP DPSRAM MC68020 Floating Point Processor LOCAL BUSMicro-Controller MC68881 VME ADD DATA & FRONT PANEL Front Panel Switches and P3, P4 Control INDICATORS Connectors VIC068A VME BUS Block Diagram of RT-20 Board
RTD Input Module (RIM) RIM stands for RTD Input Module. This is a standard Euro size module with two 64 pin Euro connectors naming P1 and P2. The inputs from field RTDs come to the module on P1 and P2 is placed on I/O motherboard. INPUT SECTION: It accepts 32 RTD inputs on P1. The inputs from field RTDs come to the module on P1. The RTD inputs from field come to TB (Terminal Box) and then these are transmitted to RIM through Flat Ribbon Cable (FRC). The resistive input is converted to voltage input by passing 1 mA constant current through RTDs and voltage across the RTDs is fed to the MUX. The inputs are multiplexed using 8-channel multiplexer and output is fed to an instrumentation amplifier. The inputs are band limited, so that the noise should be filtered out.
ADC: The output of this amplifier is connected to the Buffer input of an Analog to digital converter (ADC). The ADC used, is a 12-Bit Successive approximation type, with the maximum conversion time of 10 µS. The End of Conversion is sensed by the status pin of the ADC which can be accessed by the D0 bit on the output data bus on P2 connector. OUTPUT SECTION: The 12-bit output of ADC then goes to buffers (U11, U12 & U15). This data is now ready to access by RT-20 through IOIM for further manipulation or decision making. The module interfaces with the I/O Bus on P2 connector.
There are 32 channels depicted by c1 to c32. Also all channels are connected to theirrespective RTD’s depicted by RTD1 to RTD32
Resistance Temperature Detector(RTD) RTD (Resistance Temperature Detector) is basically a temperature sensitive resistor. It is a positive temperature coefficient device, which means that the resistance increases with increase in temperature. The resistive property of the metal is called its resistivity. The resistive property defines length and cross sectional area required to fabricate an RTD of a given value. The resistance is proportional to length and inversely proportional to the cross sectional area: R= r X L / A Where R = Resistance (ohms) r = Resistivity (ohms) L = Length A = Cross sectional area
Conclusion The Temperature monitoring system is one of the primary necessities in a nuclear power plant as the temperature in the reactor must be controlled so that a related hazard could be prevented. This will help safeguard many lives, amenities and equipments. This is why the motto of NPCIL is “Safety First and Production Next”. So for this sole purpose there are Channel Temperature Monitoring Systems fitted in every nuclear power plant which monitors the temperature of the reactor core and if the temperature rises or falls above or below the respective predefined threshold value, the system generates an alarm and some predefined action related to that alarm is performed.