EXPERIMENTAL STUDY ON LOCA SCENARIO IN INDIAN HEAVY WATER NUCLEAR REACTORS

Abstract

The understanding of operating and emergency thermal hydraulic conditions of the Indian nuclear power plant play significant role for safety of power plant. The fleet of nuclear plant consists of 22 commercial operating units, which are managed (design, construction, commissioning and operation) by Nuclear Power Corporation of Indian Ltd (NPCIL). The total installed capacity of 18 PHWRs, 2 BWRs and 2 VVER (2 units of Kudankulam nuclear plant) produce 6780 MW power which is approximately 2.3 % of the total consumed power in India. The PHWR is based on the CANDU (Canadian Deuterium Uranium), which burns natural uranium as fuel. The availability of the natural uranium in India is limited but the abundant amount of thorium can fulfill the demand of energy in coming decays. The AHWR (burns thorium as a fuel) design and development phase include greatly the safety of the plants during emergency scenario. The LOCA scenario in PHWR and AHWR change the thermal condition and mode of heat transfer, which are being understand with the understanding of components of core, Primary Heat Transport System (PHTS), Moderator system and ECCS of PHWR and AHWR. The LOCA scenario of PHWR and AHWR reactors are discussed greatly along with the rewetting process of AHWR. The nuclear power plant operating cycle is based on the Rankine cycle and similar to the operation cycle of the conventional coal thermal power plant. The conventional thermal power plant burns coal as a fuel whereas, uranium used in nuclear power plant. The 220MWe and 540MWe rating PHWRs are operating in India whereas, the 700 MWe IPHWR is in design and development stage. The heat is supplied to the boiler from the nuclear power. The produced power in 200MWe PHWR is supplied to Rankine cycle with the help of primary heat transport system. The 54 pin fuel cluster having height of 3.5 m is concentrically housed inside a Zr-2.5 wt% Nb pressure tube (PT). The 54 pins of fuel bundle are arranged in three concentric ring inner ring, middle ring and outer rings. These rings consist of 12, 18 and 24 pins in inner, middle and outer rings respectively. The fuel bundle center has a water rode, which is used to provide water supply during the LOCA of the channel. The holes provided on the water rod produce jet effect and able to break the vapor film formed on the surface of the clad tube and promote the nucleate boiling heat transfer so that more decay heat can be removed from clad surface.