The International Reactor Innovative and Secure (IRIS) is modular, economic, medium size (1000 MWth), grid appropriate and based on the safety-by-designTM philosophy. The integral configuration of the primary system, the strong coupling of reactor vessel and containment, during accident conditions, and the passive safety systems guarantee a very high degree of inherent safety. The IRIS International Consortium, that led by Westinghouse has developed the plant design, is strongly pursuing the objective to obtain the Final Design Approval (FDA) by the U.S. Nuclear Regulatory Commission (NRC), by 2013.The relative licensing process requires the execution of integral and separate effect tests on a properly scaled reactor simulator. Within the framework of an Italian R&D program on Nuclear Fission, managed by ENEA and supported by the Ministry of Economic Development, the SPES3 facility is being designed and will be built at SIET laboratories. 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 Westinghouse AP-600 reactor. On the basis of the lessons learned and relying on existing auxiliary systems, the simulation of an accidental sequences matrix on the SPES3 facility will provide the needed experimental results to verify the general behaviour of the system and allow a code assessment process suitable to produce a reliable tool for the IRIS plant analyses.The main scaling parameters for the facility design have been determined through a Phenomena Identification and Ranking Table (PIRT) and a Hierarchical Two-Tired Scaling Analysis (H2TS) process resulting in 1:100 volume and power scale, 1:1 elevation scale, prototypical fluid at plant pressure and temperature nominal conditions. The detailed scaling of all plant components is the result of an iterative process between a Top-Down system scaling and Bottom-Up process scaling, i.e. a continuous verification of the experimental facility component design adequacy to appropriately 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 SGs. A single outer pump simulates the eight IRIS primary internal circulation pumps. Two Emergency Boration Tanks (EBT), the two 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 removing the decay heat during the long term accidental transients. The IRIS containment compartments are simulated in SPES3 by appropriately connected separated tanks, representing 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). Shape and dimensions are fixed in order to reproduce the trend of IRIS compartment volumes versus height. Both the primary and secondary loops are designed for 17.25 MPa pressure and the corresponding saturation temperature. The containment tanks are designed for 2 MPa pressure and the corresponding saturation temperature.In order to fit the new facility components and pipes on the existing steel structure of SPES2, an appropriate design of piping layout has been defined.A large set of instruments (about 600) will be installed on SPES3 to provide data both for the test run and analysis. It will consist of conventional (relative and absolute pressure transmitters and temperature sensors) and special (for two-phase flow measurement) instrumentation.The planned test matrix consists of 13 integral tests and 2 separate effect tests. The integral tests, which will simulate Design Basis Accidents (DBA) and Beyond Design Basis Accidents (BDBA) scenarios, are aimed at assessing the plant response and verifying the safety system effectiveness. The considered accidental events consist of a series of split and Double Ended Guillotine (DEG) breaks, ranging from 2 to 6 inch equivalent, on the main piping of the primary and secondary sides (DVI, EBT balance line and ADS, Feed Line and Steam line). The separate effect tests are devoted to investigate the interaction and characterize the heat transfer of innovative design components like the helical coil steam generators and the EHRS for the long term removal of the decay heat.The Relap5 code is used for the complete simulation of the facility through the three steps planned to achieve the foreseen objectives: 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 through the Relap5+Gothic codes will provide information on the appropriateness of the performed scaling 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 to be used to tune the IRIS-specific analyses.Thanks to the iteration between facility design and analysis, the SPES3 facility will provide suitable 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 necessary for the Final Design Approval.
|Titolo:||The SPES-3 Experimental Facility Design for the IRIS Reactor Integral Reactor Simulation|
|Data di pubblicazione:||28-apr-2008|
|Appare nelle tipologie:||4.1 Contributo in Atti di convegno|