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OECD/NEA PBMR Coupled Neutronics/Thermal-hydraulics Transients Benchmark - The PBMR-400 Core DesignIn co-operation with PBMR Pty Ltd, Penn State University (PSU)Background and purpose This international benchmark, concerns Pebble Bed Modular
Reactor (PBMR) coupled neutronics/thermal-hydraulics transients based
on the PBMR-400MW design. In many cases the deterministic neutronics,
thermal-hydraulics and transient analysis tools and methods available
to design and analyse PBMRs lag behind the state of the art compared to
other reactor technologies. This has motivated the testing of existing
methods for HTGRs but also the development of more accurate and
efficient tools to analyse the neutronics and thermal-hydraulic
behaviour for the design and safety evaluations of the PBMR. In
addition to the development of new methods, this includes defining
appropriate benchmarks to verify and validate the new methods in
computer codes.
The PBMR functions under a direct Brayton cycle with primary coolant helium flowing downward through the core and exiting at 900°C. The helium then enters the turbine relinquishing energy to drive the electric generator and compressors. After leaving the turbine, the helium then passes consecutively through the LP primary side of the recuperator, then the pre-cooler, the low-pressure compressor, intercooler, high-pressure compressor and then on to the HP secondary side of the recuperator before re-entering the reactor vessel at 500°C. Power is adjusted by regulating the mass flow rate of gas inside the primary circuit. This is achieved by a combination of compressor bypass and system pressure changes. Increasing the pressure results in an increase in mass flow rate, which results in an increase in the power removed from the core. Power reduction is achieved by removing gas from the circuit. A Helium Inventory Control System is used to provide an increase or decrease in system pressure. The PBMR-400 benchmark consists of phases, each consisting of different exercises:
Exercise 1: Neutronics solution
with fixed cross-sections;
Exercise 2: Thermal-hydraulic solution with given power/heat sources; Exercise 3: Combined neutronics thermal-hydraulics calculation - starting condition for the transients.
Exercise 1: Depressurised loss of
forced cooling (DLOFC) without SCRAM;
Exercise 2 : Depressurised loss of forced cooling (DLOFC) with SCRAM; Exercise 3: Pressurised loss of forced cooling (PLOFC) with SCRAM; Exercise 4 : 100-40-100 load follow; Exercise 5 : Fast reactivity insertion - control rod withdrawal (CRW) and control rod ejection (CRE) scenarios at hot full power conditions; Exercise 6 : Cold helium inlet. Reference Frederik Reitsma, Kostadin
Ivanov,Tom Downar, Han de Haas, Sonat
Sen, Gerhard Strydom, Ramatsemela Mphahlele, Bismark Tyobeka, Volkan
Seker, Hans D Gougar: PBMR Coupled Neutronics/Thermal Hydraulics
Transient Benchmark - The PBMR-400 Core Design, Benchmark Definition,
Draft V03, published by the NEA in 2005.
Material available to participants on CD-ROM
Summary of the first workshop, Paris, 16-17 June 2005 (PBMRT1) Summary of the second workshop (PBMRT2) OECD/NEA Issy-les-Moulineaux, France, 26-27 January 2006 Summary of the third workshop (PBMRT3) OECD/NEA Issy-les-Moulineaux, France, 1-2 February 2007 Task list/Outstanding issues from PBMRT3 meeting Summary of the fourth workshop (PBMRT4) OECD/NEA Issy-les-Moulineaux, France, 21-25 January 2008 NEW Proposed Programme for fifth Workshop (PBMRT5), Kongresszentrum, Interlaken, Switzerland, 14 September 2008 NEW Action list from the PBMRT4 workshop Results from the PBMRT4 workshop Web pages for benchmark participants (requires password) Contact at the OECD/NEA: Enrico Sartori Last update: 16 June 2008 |