Assessment of shutdown systems performance for LBLOCA for taps no. 3 and 4
- Directorate of Safety, Nuclear Power Corporation of India Limited, Nabhikiya Urja Bhavan, Anushakti Nagar, Mumbai, PIN-400094 (India)
A Large Break Loss of Coolant Accident (LBLOCA) in Pressurized Heavy Water Reactor (PHWR) occurs when large diameter pipe ruptures such as Reactor Inlet Header (RIH), Reactor Outlet Header (ROH) or Pump Suction Line(PSL). LBLOCA in PHWR results in insertion of positive reactivity due to core voiding leading to increase in reactor power. For large breaks, there is an early increase in neutron power as regulating system is not able to compensate and the event leads to reactor trip occurring from neutronic signals. In addition several other trip signals will be activated namely low PHT pressure, low PHT coolant flow and high RB pressure one after the other in a short time, the peak power transient gets significantly influenced in the early transient response. One or other Shut Down System (SDS) gets actuated promptly to terminate the transient. To study the system behavior under large break LOCA (LBLOCA) condition for 540 MWe twin unit Tarapur Atomic Power Station (TAPS 3 and 4), a wide range of break sizes is considered starting from 5% break (transition boundary between LBLOCA and Small Break LOCA) up to the guillotine break at RIH, ROH and PSL with class IV power supply available as well as failed covering early blow-down and ECCS injection phase of the accident. These analyses were done using NPCIL in-house developed system Thermal Hydraulic Neutronic code ATMIKA considering 3-D neutronics. It is seen that in the entire spectrum of break size at particular location, there is flow stagnation/low flow in the early period of transient for a particular break and represent most limiting case as far as fuel clad overheating and clad oxidation is concerned, known as critical break. It is observed that critical breaks in pump suction line are governing with respect to fuel sheath temperature excursion. LOCA analysis has been done with recent IAEA supplied ENDF/B.VI 69 group neutron cross-section library for equilibrium core and minimum allowed Isotopic Purity (I.P.) of PHT coolant i.e. 97% as specified in station technical specification. Analysis examines Shut Down systems performance for the governing case for various LOCA condition and other related physics inputs. (authors)
- Research Organization:
- American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
- OSTI ID:
- 21021199
- Resource Relation:
- Conference: 2006 International congress on advances in nuclear power plants - ICAPP'06, Reno - Nevada (United States), 4-8 Jun 2006; Other Information: Country of input: France; 21 refs; Related Information: In: Proceedings of the 2006 international congress on advances in nuclear power plants - ICAPP'06, 2734 pages.
- Country of Publication:
- United States
- Language:
- English
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