ISSN オンライン: 2688-7231
ISBN 印刷: 978-1-56700-497-7 (Flash Drive)
ISBN オンライン: 978-1-56700-496-0
Proceedings of the 25th National and 3rd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2019)
Transient Analysis Of All Steam Generators Feed Valve Stuck Open For 700 MWe IPHWRs
700 MWe Indian Pressurized Heavy Water Reactor (IPHWR) is a horizontal channel type reactor with two loops of Primary Heat Transport (PHTS) system. There are four Steam Generators (SGs) which receive feed water from the common header at the downstream of a set of two feed valves which operate in tandem. Three (two operating and one stand by) main boiler feed water pumps (BFP) supply feed water to Steam Generators (SGs).
In each set of valves, one is a large capacity (80%) valve (one active and one standby) and the other is a small capacity (20%) valve. In the event of all SGs feed valve stuck open, all SGs feed valves large as well as small are stuck open. The reason for this event postulation is to study and predict the behaviour of the plant under the transient encountered during operation. Transient analysis for this event is performed using in- house developed system thermal hydraulic coupled 3_D neutron kinetics computer code ATMIKA.T.
This paper provides timelines of following sequence of events which is important for operator's action to maneuver the event, and the main findings of the study are:
· Feed water flow increases and steam flow reduces as more heat is required for sensible heat.
· SG level rises and reaches very high level set point at around 94.0 s and as a result turbine trips and feed water isolating valves on the large feed water lines get closed.
· Feed water flow reduces drastically.
· Atmospheric Steam Discharge Valves (ASDVs) opens due to turbine trip.
· Reactor setback occurs due to ASDVs opening which causes power run down.
· As large feed water isolation valves get closed, SG level starts falling.
· Reactor trips as SG Level reaches its set point of reactor trip at around 244 s (~4 minutes).
· Auxiliary Boiler feed pump (ABFP) started on SG level very low in all four SGs at around 254 s.
· As power becomes less than the feed water flow, SG level recovers and starts flooding SGs.