Coolant Channel Outlet Temperature Monitoring System in Indian PHWRs

1
Coolant Channel Outlet Temperature Monitoring
System in Indian PHWRs

• G. Ganesh
• Head, Process Information Systems Section
• Reactor Control Division
• BARC, Mumbai, India

2
Introduction

• One of the important surveillance limitation
  functions
• Only CTM system can detect excessive rise in
  outlet temperature of a particular coolant
  channel
• Monitors Outlet temperature of each coolant
  channel using a pair of RTDs
• Indirectly detects the inadequate coolant
  flow/fuel abnormal condition in any coolant
  channel
• Generates Power Setback / Control room
  annunciations

3
Sensor Excitation

• Two wire RTD (Pt-200) on stubs of ROH
• MI cable Shielded twisted pair
• Constant voltage source
• Half bridge circuit
• Monitoring of excitation voltage for variation
• Self heating

4
Sensor Excitation
5
MAPS CTM System(Madras Atomic Power Station)

• First computerized CTM system in Indian PHWR
• Performed only monitoring function
• Scan period 6 Seconds
• Lead cable resistance compensation
• Presents several computed parameters (Zone Mean
  Temp, Zone Mean Temp Deviation, Thermal Power)
• Hardcopy records of instantaneous readings

6
MAPS CTM System Contd

• Based on 8 bit microprocessor
• Monochrome CRT with keyboard
• One demand logging printer one alarm printer
• In-house developed hardware software
• Software in PASCAL and assembly

7
MAPS CTM System Contd
8
NAPS-2 CTM System(Narora Atomic Power Station)

• Two independent, identical Computerized CTM
  systems
• First time both RTD installations were connected
  to Computerized CTM systems
• Each system independently acquires temperature
  inputs from a set of RTDs
• Contact outputs for flux tilt control
• Significant changes in hardware and software
  compared to MAPS

9
NAPS-2 CTM System Contd

• Based on 16 bit microprocessor
• Faster ADC with digital filtering
• Watchdog for monitoring system health
• Scan period 4 seconds
• Faster operator response
• Dynamic display formats
• Software in C and assembly with a real-time
  kernel

10
NAPS-2 CTM System Contd
306 analog inputs
11
RAPS-3,4 CTM System(Rajasthan Atomic Power
Station)

• First time power setback function was
  computerized
• System categorized as safety related system
  (class IB)
• CTM balancing procedure during hot conditioning
  was computerized
• RTD excitation through switched current to
  eliminate self-heating error

12
Current switching scheme
13
RAPS-3,4 CTM System Contd

• Distributed computer architecture
• AU (Alarm Unit), OIU (Operator Information Unit),
  CU (Control Unit)
• Communication of channel status between AUs
• Software in C and assembly
• Diverse software on AUs
• Windows OS based HMI
• Identical CTM systems at RAPS-3,4 KGS-1,2

14
RAPS-3,4 CTM System Contd
15
RAPS-3,4 CTM System Human Machine Interface
16
TAPS-3,4 CTM System(Tarapur Atomic Power
Station)

• 392 coolant channels
• Dynamic alarm generation
• Online setback test
• Switching of failed RTDs between installations
• Built around 32 bit (internal) microprocessor
• Intelligent Ethernet communications module
• Communicates data to Reactor Parameter Display
  System
• IEEE, IEC-880 and MISRA-C guidelines

17
Design Principles

• Simple, proven hardware
• Redundancy sensor, system
• Coincidence check for setback
• Single failure criteria
• Diverse software
• Physical separation
• On-line diagnostics

18
TAPP-3,4 CTM System Contd
19
VV Methodology

• Design Walk-through
• Review of design documents
• Tool assisted program analysis for checking
  conformance to adopted design practices.
• checking compliance to adopted Programming
  standard like MISRA C
• computation of software quality metrics
• carry out code reviews.

20
VV Methodology

• Static program analysis for detecting runtime
  errors.
• buffer index out of range,
• arithmetic errors,
• non termination of loops
• non-initialized variables
• Assertion based analysis of software for checking
  conformance to Requirements Specification
• based on deductive techniques and model checking.
  This is applicable to only restricted part of
  software used for safety functions.

21
Conclusion

• Continuous evolution in functionality from MAPS
  to TAPS
• Simple monitoring system to a Safety related
  system
• Stricter software quality control
• Hardware 8 bit CPU (5MHz) to 32 bit CPU (20MHz)
  
• Stand-alone single computer to networked multi
  computer system

22
Thank You