An in depth review of existing fire alarm was carried out after the fire incident at Narora Atomic Power Station. This review had revealed that the coverage of the system is not adequate and does not meet the current standard. Hence it was replaced by a state of art addressable type of system, supplied by an Indian firm. The number of detectors was also increased to cover all the areas adequately and also different type of detectors like optical etc were also used.

As part of this up gradation the following additional features were also provided.

• Digital type linear heat sensor cable for fire detection of cable trays of cable bridge

• Aspirating type smoke detectors for fire detection in moderator room which is a high radiation area.

• Beam detector for boiler room for wide area coverage in high temperature areas

• Flame detectors for fire detection in oil tanks.

Different samples of cables were collected in RAPS and were subjected to ageing test to estimate their residual life. For most of the cables residual life was found to be about 8 to 10 years.

Collecting samples of trunk cables is found impracticable due unavailability of adequate length of samples, without disturbing the cable terminations. Hence it is recommended that wherever feasible extra length shall be provided. Alternatively dummy samples may be kept at appropriate locations for testing purpose.

Emergency core cooling system

Emergency core cooling system, existing in RAPS and MAPS was a low-pressure injection system, using moderator pumps. As part of safety up gradation it was decided to retrofit high pressure injection system, in line with the current practices followed.

The existing instrumentation and controls was using pressure switches for detecting the LOCA condition and pneumatic DP transmitters for sensing direction of injection. As part of up gradation the entire instrumentation was modified, using electronic pressure transmitters for detecting LOCA condition and DP transmitters for sensing direction of injection. A test facility was also provided for online testing of all the motorized valves of the system along with their logic.