The International Reactor Innovative and Secure (IRIS) is a modular, economic, medium size (1000 MWth), grid appropriate reactor belonging to the Innovative Nuclear Power Plants (NPP), in which a new plant configuration is obtained through the evolution of the mature PWR technology with a safety-by-designTM approach. The IRIS International Consortium, led by Westinghouse, is finalizing the design with the objective of obtaining the Final Design Approval (FDA) by the U.S. Nuclear Regulatory Commission (NRC), by 2013. The main feature of the IRIS is an integral primary system configuration with all main components contained in the Reactor Vessel (RV): pressurizer, primary circulation pumps and once-through helical coil steam generators. A compact spherical steel containment is part of the IRIS safety systems and is involved in a coupled dynamic behaviour in the passive mitigation strategy which enhances the safety and reliability of the IRIS.One of the steps required by the licensing process is the execution of integral and separate effect tests on a properly scaled reactor simulator of the IRIS reactor. The SPES3 facility is being designed and will be built at SIET laboratories in the framework of an Italian R&D program on Nuclear Fission, managed by ENEA and supported by the Ministry of Economic Development. The simulation of a series of accidental sequences will provide data to verify the general behaviour of the system and allow a wide code assessment guaranteeing a reliable tool for the IRIS plant analyses.In the early 90s, the SIET company upgraded the SPES facility (simulating a three loop PWR for the italian PUN - Progetto Unificato Nazionale) in SPES2, providing the experimental data that allowed the licensing of the W AP-600 reactor. On the basis of the gained experience and relying on the same auxiliary systems as SPES2, the SPES3 will provide the experimental results in sight of the IRIS Final Design Approval (FDA) by 2013. The main scaling parameters were defined on the basis of a Phenomena Identification and Ranking Table (PIRT) and of a Hierarchical Two-Tired Scaling Analysis (H2TS) methodology. The IRIS System Decomposition and the Scale Identification (first two steps of H2TS) led to choose 1:100 volume and power scale, 1:1 elevation scale, prototypical fluid at plant pressure and temperature nominal conditions. The detailed scaling of all components of the plant is the result of an iterative process between a Top-Down system scaling and Bottom-Up process scaling, i.e. a continuous verification if the experimental facility component design choices are suitable to represent what expected in the plant. The SPES3 facility simulates the primary, secondary and containment systems of the IRIS reactor. The Reactor Vessel (RV) includes the fuel bundle with electrically heated rods, the inverted hat pressurizer (PRZ) and three helical coil steam generators (SG) simulating the eight IRIS SG modules. A single outer pump simulates the eight IRIS internal primary circulation pumps. Two Emergency Boration Tanks (EBT), the Direct Vessel Injection (DVI) lines and the Automatic Depressurization System (ADS) are also simulated.The secondary side feed lines and steam lines are simulated up to the main isolation valves and the three Emergency Heat Removal Systems (EHRS), represent the four trains of the IRIS primary safety system. The facility configuration is suitable to investigate the natural circulation loops that allow the decay heat removal during the long term accidental transients. Both primary and secondary side are designed for 17.25 MPa pressure and the corresponding saturation temperature.The IRIS containment compartments are simulated in SPES3 by separate tanks, connected by pipes. The tanks, in particular, represent the Dry-Well (DW), two Pressure Suppression Systems (PSS), two Long Term Gravity Make-up Systems (LGMS), the Reactor Cavity (RC) and the ADS Quench Tank (QT). In some cases, the shape of the tanks differs from cylindrical in order to reproduce the trend of IRIS plena volumes versus height. The containment tanks are designed for 2 MPa pressure and the corresponding saturation temperature.A complex design of piping layout allows to fit the new facility components and pipes on the existing steel structure that housed the SPES2. The SPES3 facility will be equipped with about 600 instruments, mainly of conventional type, like relative and absolute pressure transmitters and temperature sensors. Special instrumentation for two-phase flow measurement will be installed too. A matrix, including 15 tests: 13 for integral effects and 2 for separate effects, is foreseen on SPES3. The integral tests are devoted to verify the facility response and safety system effectiveness to take the plant in safe conditions after Design Basis Accidents (DBA) and Beyond Design Basis Accidents (BDBA). Split and Double Ended Guillotine (DEG) Small Break Loca Accidents (LOCA) are foreseen both on the primary side (DVI, EBT balance line and ADS) and the secondary side (Feed Line and Steam line) ranging from 2 to 6 inch equivalent.The separate effect tests are devoted to investigate and characterize the behaviour of innovative design components like the helical coil steam generators and their interaction/heat transfer capabilities with the EHRS.The Relap5 code is used to simulate the SPES3 facility in all its parts. Three steps are foreseen: a) Supporting design analyses aimed at obtaining feedback information on the facility design. In particular the comparison between the SPES3 facility and the IRIS reactor simulations (Relap5+Gothic codes) will provide information on the correctness of the performed choices; b) Pre-test analyses aimed at the test design and test procedure set-up; c) Post-test analyses and code assessment on a set of qualified data.The SPES3 facility will provide experimental data of the main tests required by the NRC. The code assessment on such data will guarantee a reliable tool to perform the IRIS reactor safety analyses in sight of the Final Design Approval.
|Titolo:||Design of the SPES-3 Experimental Facility for the IRIS Reactor Integral Reactor Simulation|
|Data di pubblicazione:||14-apr-2008|
|Appare nelle tipologie:||4.1 Contributo in Atti di convegno|