IMAS-H2: Monitoring of H2-accumulation

Major task of the system

Detection of local H2-accumulations in boiling water reactors (BWRs).

Scheme and function

  • monitoring of temperatures at selected points of steam lines
  • temperature monitoring using 2 totally independent measurement systems
  • 3rd system checks function of the 2 monitoring systems
  • if limit is exceeded an alarm is sent to plant control room
  • quick-look evaluation of data in control room
  • measures determined on the basis of this quick-look evaluation
IMAS Integrity Management System
scheme of the monitoring system IMAS H2
scheme of the monitoring system IMAS-H2


  • two totally independent measurement chains
  • two totally independent measurement systems
  • two totally independent power supplies
  • additional check of the monitoring systems by a 3rd system
  • hard- and software function control by internal and external watchdog
  • local and central data storage
  • alarm output in case of violation of limits
  • alarm output in case of hardware defect
  • alarm at the I&C cabinet and at the control room
  • visual check of the measured data in case of an alarm