Performance evaluation of passive pulse generator for auto depressurization system of Advanced Heavy Water Reactor

Abstract

The Advanced Heavy Water Reactor (AHWR) is a 300 MWe pressure tube type boiling light water cooled, heavy water moderated reactor. It has natural circulation based main heat transport system with integral steam drums. Recently, work has been initiated on a novel passive safety system named Passive Auto Depressurization System (PADS) for AHWR. This system is a part of shutdown cooling system and in case of occurrence of small break loss of coolant accident; PADS system mitigates chance of reactor core temperature rise. It actuates automatically at low steam drum level and rapidly depressurizes main heat transport system so that water injection from gravity driven water pool can be initiated to maintain coolant inventory for a sufficiently long time.The main component of PADS is Passive Pulse Generator (PPG), a passive device which is actuated at low steam drum level and generates high pressure signal within a short time span. The PPG generates a passive pressure pulse of around 11 bar amplitude with 8 min response time with threshold steam drum level fall of 100 mm. This pressure pulse is used for opening a passive valve which initiates decay heat removal through isolation condenser leading to depressurization of main heat transport system. An experimental facility has been designed towards the development and performance evaluation of PPG for PADS system of AHWR.This paper deals with the design of the experimental facility describing its piping layout, steam drum & heat exchanger vessel and associated instrumentation & control system. Test results along with RELAP5 analysis are discussed to validate PPG performance for PADS in AHWR.